CatatanIni adalah tugas kuliah Pemrograman Visual saya selama studi S1 di Jurusan Teknik Elektro Universitas Udayana, 2011. Memang tugas ini jauh ketinggalan tetapi bisa menjadi hiburan jauh di masa depan dimana kecanggihan Visual Basic sudah sangat maju dan ketika melihat tugas ini, para programer tua akan merasa nostalgia dan para programer muda akan kaget mengenai bagaimana belum berkembangnya Visual Basic dulu. Tugas ini belum pernah dipublikasikan di mana pun dan saya dan Muhammad Audy Bazly, sebagai penulis dan pemegang hak cipta, melisensikan tugas ini dengan penyesuaian CC-BY-SA di mana siapa pun dapat membagikan, menyalin, menerbitkan ulang, dan menjual dengan syarat untuk menyatakan nama kami sebagai penulis dan memberi tahu bahwa versi asli dan terbuka tersedia di sini. Mengenal Visual Basic 6.0Bahasa Basic pada dasarnya adalah bahasa yang mudah dimengerti sehingga pemrograman di dalam bahasa Basic dapat dengan mudah dilakukan meskipun oleh orang yang baru belajar membuat program. Hal ini lebih mudah lagi setelah hadirnya Microsoft Visual Basic, yang dibangun dari ide untuk membuat bahasa yang sederhana dan mudah dalam pembuatan scriptnya (simple scripting language) untuk graphic user interface yang dikembangkan dalam sistem operasi Microsoft Windows. Visual Basic merupakan bahasa pemrograman yang sangat mudah dipelajari, dengan teknik pemrograman visual yang memungkinkan penggunanya untuk berkreasi lebih baik dalam menghasilkan suatu program aplikasi. Ini terlihat dari dasar pembuatan dalam visual basic adalah FORM, dimana pengguna dapat mengatur tampilan form kemudian dijalankan dalam script yang sangat mudah. Ledakan pemakaian Visual Basic ditandai dengan kemampuan Visual Basic untuk dapat berinteraksi dengan aplikasi lain di dalam sistem operasi Windows dengan komponen ActiveX Control. Dengan komponen ini memungkinkan penguna untuk memanggil dan menggunakan semua model data yang ada di dalam sistem operasi windows. Hal ini juga ditunjang dengan teknik pemrograman di dalam Visual Basic yang mengadopsi dua macam jenis pemrograman yaitu Pemrograman Visual dan Object Oriented Programming (OOP). Visual Basic 6.0 sebetulnya perkembangan dari versi sebelumnya dengan beberapa penambahan komponen yang sedang tren saat ini, seperti kemampuan pemrograman internet dengan DHTML (Dynamic HyperText Mark Language), dan beberapa penambahan fitur database dan multimedia yang semakin baik. Sampai saat buku ini ditulis bisa dikatakan bahwa Visual Basic 6.0 masih merupakan pilih pertama di dalam membuat program aplikasi yang ada di pasar perangkat lunak nasional. Hal ini disebabkan oleh kemudahan dalam melakukan proses development dari aplikasi yang dibuat. Interface Antar Muka Visual Basic 6.0Interface antar muka Visual Basic 6.0, berisi menu, toolbar, toolbox, form, project explorer dan property seperti terlihat pada Gambar 1 berikut: Pembuatan program aplikasi menggunakan Visual Basic dilakukan dengan membuat tampilan aplikasi pada form, kemudian diberi script program di dalam komponen-komponen yang diperlukan. Form disusun oleh komponen-komponen yang berada di [Toolbox], dan setiap komponen yang dipakai harus diatur propertinya lewat jendela [Property]. Menu pada dasarnya adalah operasional standar di dalam sistem operasi windows, seperti membuat form baru, membuat project baru, membuka project dan menyimpan project. Di samping itu terdapat fasilitas-fasilitas pemakaian visual basic pada menu. Untuk lebih jelasnya Visual Basic menyediakan bantuan yang sangat lengkap dan detail dalam MSDN. Toolbox berisi komponen-komponen yang bisa digunakan oleh suatu project aktif, artinya isi komponen dalam toolbox sangat tergantung pada jenis project yang dibangun. Komponen standar dalam toolbox dapat dilihat pada Gambar 2 berikut ini. Adapun fungsi-fungsi komponen-komponen kontrol yang ada di ToolBox pada Visual Basic:
Konsep Dasar Pemrograman Dalam Visual Basic 6.0Konsep dasar pemrograman Visual Basic 6.0, adalah pembuatan form dengan mengikuti aturan pemrograman Property, Metode dan Event. Hal ini berarti:
Membuat Project BaruUntuk memulai pembuatan program aplikasi di dalam Visual Basic, yang dilakukan adalah membuat project baru. Project adalah sekumpulan form, modul, fungsi, data dan laporan yang digunakan dalam suatu aplikasi. Membuat projrct baru dapat dilakukan dengan memilih menu [File] >> [New Project] atau dengan menekan ikon [new project] pada Toolbar yang terletak di pojok kiri atas. Setelah itu akan muncul konfirmasi untuk jenis project dari program aplikasi yang akan dibuat seperti terlihat pada Gambar 3 berikut. Visual Basic 6.0 menyediakan 13 jenis project yang bisa dibuat seperti terlihat pada gambar 3 di atas. Ada beberapa project yang biasa digunakan oleh banyak pengguna Visual Basic, antara lain:
Selanjutnya pilih Standard EXE dan tekan [Ok]. Lalu muncul tampilan dari Standard Exe seperti pada gambar 1.1. Dengan demikian project sudah siap dibuat.Dalam pembuatan project sebelumnya double click pada form yang terbuat maka adak terlihat jendela tersembunyi (hidden windows) yang berupa jendela untuk pembuatan program atau jendela kode (code windows). Hal ini Dapat dilakukan dengan cara memilih ikon jendela form atau jendela kode yang ada di [Project Explorer]. Hal ini dapat dilihat pada Gambar 4 dan Gambar 5. Pada jendela form, pengguna dalam membangun tampilan dari program aplikasi yang akan dibuat dengan mengatur komponen-komponen baik letak, properti dan eventnya. Untuk mengambil suatu komponen dari [Toolbox] dapat dilakukan dengan click komponen tersebut, kemudian clik atau tarik pada posisi yang benar pada form. Sebagai contoh mengambil label dari Toolbox dapat dilakukan dengan cara seperti Gambar 6 di bawah ini. Langkah-langkah mengambil label dari toolbox untuk dipasangkan dalam form adalah sebagai berikut:
Catatan: jangan lupa untuk mengatur property name dari setiap komponen yang digunakan, karena name merupakan identitas obyek yang akan digunakan dalam menulis program. Langkah berikutnya adalah memberikan teks pada label, misalkan “Hello world”, maka piliha properti Caption, dan isi dengan Hello world. Hasil tampilan program adalah sebagai berikut: Dan untuk menjalankan program click ikon Run () pada toolbar atau pilih menu [Run] >> [Start], atau dengan tekan tombol [F5]. Sehingga hasil program adalah: Pada Gambar 9 adalah contoh program yang kami buat yaitu perhitungan free space loss untuk menghitung hilang kuat sinyal di udara. Cara sama dengan hanya menambah rumus-rumus saja. Program tersedia di Github.
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NoteThis is a collection of my Electrical Materials course assignment during my undergraduate study at the Electrical Engineering Department of Udayana University, 2010. Some of my assignments were lost because some of them were handwritten and submitted but here are the surviving assignments that were recorded electronically. The purpose of this post apart from being a reference for students is for others who want to know what kind of assignments were given during my era. This assignment has never been published anywhere and I, as the author and copyright holder, license this task with a CC-BY-SA compliant where anyone can share, copy, republish and sell on condition to state my name as the author and notify you that the original and open versions are available here. Introduction to Electrical Insulation and an introduction for the general public who have not yet studied electricityTo study electrical insulation, it is better to know in advance how electricity flows and its properties. In an atom there are three kinds of charges. Positive, negative and neutral charges. positive charge is called "proton", negative charge is called "electron" and neutral charge is called "neutron". Similar charges (++,-) repel each other, different charges (+-) attract each other. Electricity is a flowing charge, in the salt bridge in chemistry, electricity can be generated because of the flowing electrons. This will explain more about the salt bridge, but the reader doesn't have to go into it. It is enough to read it because this section is an introduction. In chemistry it is known as the oxidation number, which is a number that states the amount of electric charge of an element in its compound. There are two chemical reactions known in this section, namely reduction and oxidation. A particle is said to experience a reduction when it captures an electron, it is said to undergo oxidation when it releases an electron. In a salt bridge, there are two poles connected by cables that can carry electric current, one pole is reduced (accepts electrons) and the other pole experiences oxidation (releases electrons). If in the middle of the cable is connected to a multi-tester, it will appear that there is an electric current flowing in the cable. Because this section is for introduction only, the author will not provide further information. If you want to know more about it, study Chemistry especially Electrochemistry. The basic things an electrician should know are current, voltage and resistance. The currents are already described in the section on salt bridges. Current is defined as I = dq/dt is the charge flowing per second in units of I (amperes). Voltage is like the pressure in water, V = dw/dq is the energy in the charge in V (volts). Resistance is the resistance to an electric current, V = IR or R = V/I in units of R (ohms). To understand resistance, think of it as a water pipe being narrowed. If the pipe is narrowed, the water will press harder and will flow less, if it is narrowed again until it closes, there will be no water flowing. Similar to resistance. To learn more about this study Electrical Circuits. After knowing this, we can understand more easily about electrical insulation. A material is said to be a conductor if it can easily carry an electric current, for example iron, water, salt and so on. Humans are good conductors because about 80% of our body is water. Therefore, it is easy for us to feel stun (tension felt by humans). Walk the carpet in rubber boots! Bring your finger to the metal connected to the ground (pegam iron lock and touch it to the metal connected to the ground). There will be sparks. According to physics, electric sparks originate from an electric charge that jumps through the sharp end to a different potential place. Often when you turn on a portable lamp, you feel electrocuted. Why, when there is lightning striking near us, can't you avoid? According to physics, high voltages can produce large electric currents. Lightning hitting trees will send electricity to the earth. When we take a step, between the two legs there is a great tension. Here a current will flow through our bodies and kill us. But in a person sitting (feet together) between the legs there is no tension. Here the current passes through the earth without passing through the body. (Taken from Physics is Fun 2, by Prof. Yohanes Surya, Ph.D.) On the other hand, a material that is difficult to carry an electric current is called an electric insulator. Examples of electrical insulators that are widely known to people are polymer materials, for example rubber. Some say strong electrical insulators are dielectrics. True, the dielectric is a material that can polarize (break up the combined charges). There is another sense that an electrical insulator is one where there is no electricity. The causes of this material being an insulator, among others, the absence of space or the fullness of the atomic nucleus against the electrons, so that the electrons cannot enter, the range of one atom to another is too wide, so that the electrons are difficult to flow (requires large energy), and there may still be other reasons for this. other thing. You can study the properties of atoms in chemistry. Why do scientists need to develop electrical insulating materials, when air itself is a strong electrical insulator? If air were a conductor, electricity would certainly propagate in all directions as electricity flows through water. The most basic is the safety factor. Touching electricity with a voltage higher than 60V can jeopardize safety. This can happen intentionally or accidentally. Therefore, the copper cable in every house to carry the electric current must be covered with a polymer material, usually rubber so that it is not dangerous. In ancient times paper and textiles were used instead of rubber. Refrigerator, TV, Computer, Laptop, Mouse, Keyboard, Rise Cooker, light button, Telephone, Hand Phone, Charger and all electronic items we hold use electrical insulation so that we can touch, otherwise we will be electrocuted. The keyboard buttons on our computers use insulation in the form of mica, now it has switched to rubber. If the two wires on the utility pole touch, a short circuit can occur because the voltage is too large, after which it can cause fires and other harmful things. Therefore they must be isolated. Wood, Paper and Textiles are fibrous electrical insulation materials. Their mechanics are good. Paper and textiles are elastic. The weakness of this fibrous material is hygroscopic (absorbs water). For example wood has a resistivity of 104-1016 ohms. 104 ohms if wet and 1016 ohms if dry. Therefore sometimes as an electric insulator and if it is wet it can be a lightning conductor (for example in trees). Paper and textiles have a resistance of about 10-2-109 ohms. As an insulator it is usually used in wrapping cables, capacitors, transformer boards and others. Mica is used for high voltage isolation. Usually used in generators, motors, capacitors for radio frequency control. Has a resistivity of 1013-1016 ohms. The glass has a resistivity of 107-1017 ohms. Plastics and rubber are hydrocarbon compounds (there must be elements of hydrogen and carbon). Plastic (for PVC) has a resistivity of 1011-1016 ohms and rubber has a resistivity of 1014-1015 ohms. For more, you can study Electrical Materials. ThermoelectricThere are 2 keywords in thermoelectricity, namely thermo related to temperature or temperature, electricity is something related to electricity. In general, the thermoelectric effect is known as a conversion, with differences in temperature producing a voltage and vice versa. You can imagine that in 2 semiconductors connected to a cable, if the semiconductor is cold and the other is hot, there will be a temperature difference. This temperature difference can be studied to produce a voltage. The basic concept of the thermoelectric mechanism/workings can be said, an electron or electron hole or charge will separate/diffuse from the hot part to the cold part. The Seedbeck effect is the conversion of a temperature difference to a voltage. Estonian-German physicist Thomas Johann Seedbeck found that a compass needle is reflected when two metal connected (closed chains) are formed between the compass. The needle reflects because of the magnetic field. Danish physicist Hans Christian Orsted perfected it. To find a coefficient in thermoelectric materials, you can use the principle of the magnitude of the resulting stress at a temperature difference of 1 Kelvin. SAB = SB - SA = (ΔVB/ΔT)-(ΔVA/ΔT) The Peltier effect, whose name comes from the French physicist Jean-Charles Peltier, this law concerns the heat that flows when a current is flowed. Q = ∏ABI = (∏A - ∏B)I To make it easier to understand this effect can be said to be almost reversed with seedbek. Current flowed to move heat. This heat transfer can be compared to heat transfer. Therefore one thermoelectric part can be cold and another 1 can be hot. The Thompson Effect, whose name comes from William Thompson or another name for Lord Kelvin, which explains the positive Thompson effect and the negative Thompson effect. The positive Thompson effect explains that the hot part is a high potential and the cold part is a low potential. The current moves from hot to cold, so from high to low potential. The negative Thompson effect explains that cold parts are a high potential and hot parts are low potential. The current moves from high heat to cold, so from low to high. q = pJ2 - uJ(dT/dx) Thermogenerators use the principle of the seedbeck effect. The purpose of this generator, mostly for energy efficiency. Throughout the world there is a name wasted heat, even 90% of the electricity generated is from heat. The waste heat can be calculated as about 15 terawatts and to make use of this wasted heat a thermogenerator is created. Other applications such as engines/machines produce heat energy and heat energy is wasted into the environment. Cars generate wasted heat too. Can be installed thermoelectric in the car to save/use heat energy as well as a coolant, sometimes called the automotive thermoelectric car. In solar cells there is also wasted heat. Solar cells only need UV light to generate electricity, but sunlight also causes heat. Therefore it is combined with thermoelectric and its name is solar/thermoelectric device. The opposite of the seedbeck effect is to apply the peltier effect. In contrast to the thermogenerator, this tool requires electricity to produce heat or cold. An example for applying heat is a heater. For cooling, for example, the old refrigerator. Usage in the present era is as portable heating and cooling usually for camping. Because it produces both hot and cold. Often used as a cooler in electrical equipment, such as computers, digital cameras, etc. In medicine it is used to make chemical mixtures rapidly by using temperature to cool or heat them. Now what will be applied is the USB beverage cooler. Reference
Mirror
CatatanIni kumpulan tugas kuliah Bahan Listrik saya selama studi S1 di Jurusan Teknik Elektro Universitas Udayana, 2010. Beberapa tugas saya hilang karena beberapa tugas ditulis tangan dan dikumpulkan tetapi berikut inilah tugas yang selamat yang tercatat secara elektronik. Maksud dari postingan ini selain sebagai referensi bagi para mahasiswa adalah bagi yang lainnya yang ingin mengetahui tugas seperti apa yang diberikan selama era saya. Tugas ini belum pernah dipublikasikan di mana pun dan saya, sebagai penulis dan pemegang hak cipta, melisensikan tugas ini dengan penyesuaian CC-BY-SA di mana siapa pun dapat membagikan, menyalin, menerbitkan ulang, dan menjual dengan syarat untuk menyatakan nama saya sebagai penulis dan memberi tahu bahwa versi asli dan terbuka tersedia di sini. Pengenalan Isolasi Listrik dan Pengantar untuk kalangan umum yang Belum Belajar ListrikUntuk mempelajari isolasi listrik, lebih baik mengetahui terlebih dahulu bagaimana listrik mengalir dan sifat-sifatnya. Dalam sebuah atom dikenal tiga macam muatan. Muatan positif, negatif dan netral. muatan positif disebut “proton”, muatan negatif disebut “elektron” dan muatan netral disebut “neutron”. Muatan sejenis (++,--) saling tolak menolak, muatan berbeda sejenis (+-) saling tarik menarik. Listrik adalah muatan yang mengalir, dalam jembatan garam pada ilmu kimia, listrik dapat dihasilkan karena elektron yang mengalir. Setelah ini akan menjelaskan lebih tentang jembatan garam, tetapi pembaca tidak harus mendalaminya. Cukup dengan membacanya karena bagian ini sebagai perkenalan. Dalam ilmu kimia dikenal dengan istilah bilangan oksidasi, yaitu bilangan yang menyatakan banyaknya muatan listrik suatu unsur dalam senyawanya. Ada dua reaksi kimia yang dikenal pada bagian ini, yaitu reduksi dan oksidasi. Suatu partikel dikatakan mengalami reduksi bila menangkap elektron, dikatakan mengalami oksidasi jika melepas elektron. Pada jembatan garam ada dua kutub yang dihubungkan kabel yang dapat mengalirkan arus listrik, salah satu kutub mengalami reduksi (menerima elektron) dan kutub yang satu lagi mengalami oksidasi (melepas elektron). Jika ditengah kabel tersebut dihubungkan dengan multi-tester, akan kelihatan bahwa ada arus listrik yang mengalir pada kabel tersebut. Karena bagian ini sebagai pengenalan saja, maka penulis tidak akan member keterangan lebih lanjut. Bila ingin lebih mengetahui tentang hal tersebut, pelejarilah Kimia khusunya Elektrokimia. Hal dasar yang harus diketahui oleh orang listrik adalah arus, tegangan dan resistansi. Arus sudah dijelaskan pada bagian jembatan garam. Arus dirumuskan dengan I=dq/dt adalah muatan yang mengalir tiap detik dengan satuan I (ampere). Tegangan adalah bagaikan tekanan dalam pada air, V=dw/dq adalah energi pada muatan dengan satuan V (volt). Resistansi adalah hambatan pada arus listrik, V=IR atau R=V/I dengan satuan R (ohm). Untuk mengerti resistansi anggap saja bagaikan pipa air dipersempit. Jika pipa dipersempit maka air akan menekan lebih keras dan sedikit yang mengalir, jika disempitkan lagi hingga menutup tidak akan ada air yang mengalir. Mirip dengan resistansi. Untuk mempelajari lebih lanjut tentang hal ini pelajarilah Rangkaian Listrik. Setelah mengetahui hal tersebut, baru kita dapat lebih mudah paham tentang isolasi listrik. Suatu bahan dikatakan konduktor bila dapat dengan mudah mengalirkan arus listrik, contohnya besi, air, garam dan sebagainya. Manusia adalah konduktor yang baik karena sekitar 80% tubuh kita terdiri dari air. Oleh karena itu kita mudah merasakan setrum (tegangan yang dirasakan manusia). Berjalanlah di atas karpet dengan sepatu karet! Dekatkan jari anda pada logam yang dihubungkan ketanah (pegam kunci besi dan sentuhkan ke logam dihubungkan ketanah). Akan terlihat percikan api. Menurut fisika, bunga api listrik berasal dari muatan listrik yang melompat melalui ujung lancip ke tempat yang berbeda potensialnya. Seringkali ketika anda menghidupkan lampu portable, anda merasa kesetrum. Mengapa ketika ada petir menyambar dekat kita, tidak boleh lari? Menurut fisika, tegangan tinggi dapat menghasilkan arus listrik yang besar. Petir yang mengenai pohon akan mengalirkan listrik ke bumi. Ketika kita melangkah, anatar dua kaki terdapat tegangan besar. Disini arus akan mengalir lewat tubuh kita dan membunuh kita. Tetapi pada orang yang duduk (kaki rapat) di antara kedua kaki tidak ada tegangan. Di sini arus lewat bumi tanpa melalui tubuh. (Diambil dari Fisika itu Asyik 2, oleh Prof. Yohanes Surya, Ph.D.) Hal sebaliknya, bahan yang susah untuk mengalirkan arus listrik disebut isolator listrik. Contoh isolator listrik yang banyak dikenal orang adalah bahan polimer, contohnya karet. Ada yang mengatakan isolator listrik yang kuat adalah dielektrik. Benar, dielektrik adalah suatu bahan yang dapat melakukan polarisasi (memecah gabungan muatan). Ada pengertian lain bahwa isolator listrik adalah dimana tidak adanya listrik. Penyebab bahan tersebut menjadi isolator antara lain tidak adanya tempat atau penuhnya inti atom terhadap elektron, sehingga elektron tidak dapat masuk, rentang suatu atom terhadap yang lain terlalu lebar, sehingga elektron susah untuk mengalir (perlu energi besar), dan mungkin masih ada alasan hal-hal lain. Dapat dipelajari sifat-sifat atom pada kimia. Mengapa ilmuwan perlu mengembangkan bahan isolasi listrik, padahal udara sendiri merupakan isolator listrik yang kuat? Jika udara merupakan suatu konduktor maka listrik pasti akan merambat ke segala arah seperti listrik dialirkan pada air. Yang paling mendasar adalah faktor keamanan. Bila kita menyentuh listrik yang tegangannya lebih tinggi dari 60V dapat membahayakan keselamatan. Hal ini bisa terjadi secara sengaja maupun tidak sengaja. Oleh karena itu kabel tembaga di setiap rumah untuk mengalirkan arus listrik harus diselimuti oleh bahan polimer, biasanya karet agar tidak membahayakan. Zaman dahulu digunakan kertas dan tekstil daripada karet. Kulkas, TV, Komputer, Laptop, Mouse, Keyboard, Rise Cooker, tombol lampu, Telepon, Hand Phone, Charger dan semua barang elektronik yang kita pegang menggunakan bahan isolasi listrik agar dapat kita sentuh, jika tidak, kita akan kesetrum. Tombol-tombol keyboard pada komputer kita menggunakan isolasi berupa mika, sekarang sudah beralih ke karet. Jika kedua kabel pada tiang listrik bersentuhan, dapat terjadi konslet karena tegangan yang terlalu besar, setelah itu dapat menyebabkan kebakaran dan hal lain yang merugikan. Oleh karena itu mereka harus diisolasikan.
Kayu, Kertas dan Tekstil adalah bahan isolasi listrik berserat. Mekanis mereka baik. Kertas dan tekstil bersifat elastis. Kelemahan dari bahan berserat ini adalah higroskopis (menyerap air). Contohnya kayu memiliki resistivitas 104-1016 ohm. 104 ohm jika basah dan 1016 ohm jika kering. Oleh karena itu terkadang sebagai isolator listrik dan jika basah dapat sebagai konduktor petir (contohnya pada pohon). Kertas dan teksil memiliki resistansi sekitar 10-2-109 ohm. Sebagai isolator biasanya digunakan dalam membungkus kabel, kapasitor, papan transformator dan lain-lain. Mika digunakan untuk isolasi tegangan tinggi. Biasanya digunakan pada generator, motor, kapasitor untuk pengatur frekuensi radio. Memiliki resistivitas 1013-1016 ohm. Kaca memiliki resistivitas 107-1017 ohm. Plastik dan karet adalah senyawa hidrokabon (pasti ada unsur hidrogen dan karbon). Plastik (untuk PVC) memiliki resistivitas 1011-1016 ohm dan karet memiliki resistivitas 1014-1015 ohm. Untuk lebih lanjut dapat mempelajari Bahan-Bahan Listrik. TermoelektrikTerdapat 2 kata kunci pada termoelektrik, yaitu termo yang berkaitan dengan temperatur atau suhu, elektrik adalah sesuatu yang berhubungan dengan listrik. Secara umum efek termoelektrik diketahui sebagai suatu konversi, dengan perbedaan suhu akan menghasilkan tegangan dan sebaliknya. Dapat dibayangkan pada 2 semikonduktor yang terhubung dengan kabel, jika semikonduktor yang 1 dingin dan 1nya lagi panas, akan terdapat beda suhu. Beda suhu ini diteliti dapat menghasilkan tegangan. Konsep dasar mekanisme/cara kerja termoelektrik ini dapat dikatakan, suatu elektron atau lubang elektron atau muatan akan terpisah/diffuse dari bagian yang panas ke bagian yang dingin. Efek Seedbeck adalah konversi dari beda suhu menjadi tegangan. Fisikawan Estonia-Jerman bernama Thomas Johann Seedbeck menemukan bahwa jarum kompas terpantul bila terbentuk 2 metal tersambung (rangkaian tertutup) diantara kompas tersebut. Jarum terpantul karena ada medan magnet. Fisikawan Danish Hans Christian Orsted menyempurnakannya. Untuk mencari suatu kofisien pada bahan termoelektrik dapat menggunakan prinsip besarnya tegangan yang dihasilkan pada perbedaan suhu 1 kelvin. SAB = SB - SA = (ΔVB/ΔT)-(ΔVA/ΔT) Efek Peltier yang namanya berasal dari fisikawan Perancis Jean-Charles Peltier, hukum ini mengenai kalor yang mengalir bila arus dialirkan. Q = ∏ABI = (∏A - ∏B)I Untuk mempermudah mengerti efek ini dapat dikatakan hampir terbalik dengan seedbek. Arus dialirkan untuk memindahkan kalor. Pemindahan kalor ini dapat diumpakan sebagai pemindahan panas. Oleh karena suatu bagian termoelektrik bisa dingin dan yang lagi 1 bisa panas. Efek Thompson yang namanya berasal dari William Thompson atau nama lain Lord Kelvin, yang menjelaskan tentang efek Thompson positif dan efek Thompson negatif. Efek Thompson positif menjelaskan bahwa bagian panas adalah potential tinggi dan bagian dingin adalah potential rendah. Arus bergerak dari panas ke dingin, jadi dari potential tinggi ke rendah. Efek thompson negatif menjelaskan bahwa bagian dingin adalah potential tinggi dan bagian panas adalah potential rendah. Arus bergerak dari panas tinggi ke dingin, jadi dari rendah ke tinggi. q = pJ2 - uJ(dT/dx) Termogenerator menggunakan prinsip efek seedbeck. Tujuan pada generator ini, kebanyakan untuk mengefisiensi tenaga. Diseluruh dunia ada namanya panas yang terbuang bahkan 90% tenaga listrik yang dihasilkan adalah dari panas. Panas yang terbuang dapat dihitung sekitar 15 terawatt dan untuk memanfaatkan panas yang terbuang ini dibikin termogenerator. Pemakaian lain seperti pada engine/mesin, menghasilkan energi panas dan energi panas terbuang ke lingkungan. Mobil menghasilkan panas yang terbuang juga. Dapat dipasang termoelektrik pada mobil untuk penghematan/pemakaian energi panas sekaligus sebagai pendingin terkadang disebut automotive termoelektrik car. Pada sel surya juga terdapat panas yang terbuang. Sel surya hanya memerlukan sinar UV untuk menghasilkan listrik, namun sinar matahari juga menyebabkan panas. Oleh karena itu digabung selsurya dengan termoelektrik dan namanya adalah solar/termoelektrik device. Pemakaian yang berlawanan dengan efek seedbeck yaitu menerapkan efek peltier. Kebalikan dengan termogenerator alat ini memerlukan listrik untuk menghasilkan panas atau dingin. Contohnya untuk penerapan panas adalah heater. Untuk pendingin contohnya kulkas zaman dulu. Pemakaian pada era sekarang yaitu sebagai pemanas dan pendingin portable biasanya untuk kamping. Karena menghasilkan keduanya berupa panas dan dingin. Sering juga dipakai sebagai pendingin pada alat-alat listrik, seperti komputer, camera digital, dll. Di kedokteran dipakai untuk membuat campuran kimia secara cepat dengan menggunakan temperatur untuk mendinginkan atau memanaskan. Sekarang yang akan deterapkan yaitu USB pendingin minuman. Referensi
NoteThis a collection of my English class assignment during my undergraduate studies in Department of Electrical Engineering, Udayana University, 2010. For native speakers, this kind of assignment can be for elementary/primary school or highschool students but for us, the highschool and undergraduate course are repetitive since here in Indonesia, English is rarely used outside of tourism. The intention of posting this other than as a reference for students are for others who would like to know what kind of assignments are given during my era. This assignment has never been published anywhere and I, as the author and copyright holder, license this assignment customized CC-BY-SA where anyone can share, copy, republish, and sell on condition to state my name as the author and notify that the original and open version available here. Also to mention these names as some are group assignments: Yulianti Murprayana, Dani Pranata, Alit Wigunawan, I Gusti Made Widiarsana, I Nyoman Apriana Arta Putra. Final AssignmentThe AssignmentTitleThe title should really reflect your personality. For example: A brave girl from Kuta (because she has learnt surfing on the beach) or A determined girl from a jungle (because she comes from Kintamani nad now study and live in Denpasar city) or A sportive and strong young man from Ubud (because he has mastered martial arts and like to help friends and familiy) etc. My pictureThe latest photo with you as the center. It can be you passport photo or you do an action and zoom in on you with some backdrops. (no high school or little girl or little boy). Picture size should be at least 3 x 4 with sufficient resolution. My personal detailsName, age, birthday, gender, place of birth, home address (let's omit this one for now). Things I enjoy doing: Things I don’t like: Someday, I want to be a … My AssignmentA Boy who Dreams To be a WarriorThings I enjoy doing:
Things I don’t like and don’t like doing:
Someday, I want to be a man who influences the world, to take part in the world’s stage. One day I would like to be a man who stands on top of the world. It doesn’t matter dying as long as I fight on the path I believe in. Translate a local Indonesian folk lore to English Group AssignmentPan Belog dan Bebekjaman dahulu kala ada seoarng lelaki bernama Pan Belog.Pan Belog sangat dungu. Di desa itu ia terkenal karena kebodohannya. Banyak orang mencemoohkan dan menertawakannya. Ia bukan saja tidak mau bersekolah, tetapi juga tidak mau bekerja. Namun di depan istrinya, ia tidak pernah menolak tugas. Ia tidak suka dibilang malas, dan juga tidak suka dibilang bodoh. "Bapane!" seru istrinya pada suatu pagi. "Hari ini aku sangat sibuk. Tolong belikan aku dua ekor bebek di pasar. Bebek itu akan digunakan upacara di rumah mertua." Setelah menerima uang, Pan Belog segera berangkat ke pasar. "Pilih bebek yang gemuk dan berat, Bapane!" kata istrinya lagi. "Beres!" jawab Pan Belog. Baru saja masuk ke pintu pasar, lelaki bodoh itu melihat banyak pedagang bebek. "Aku beli dua bebek. Ini uang!" katanya kepada seorang pedagang. Pedagang itu heran, karena pembeli bebek itu mengambil begitu saja dua ekor bebek dan menyerahkan sekeping uang ringgit. Sebetulnya ia masih memiliki sisa uang, tetapi ia segera pergi dan tidak memperdulikan uang kembalian. "Aneh benar laki-laki itu," pikir pedagang bebek. "Ia tidak menawar dan tidak menanyakan uang kembalian," pikirnya lagi sambil menyimpan sekeping uang ringgit itu. Dalam perjalanan pulang, Pan Belog melewati sebuah sungai yang cukup dalam. Dalam hatinya terlintas, ingin mengetahui keadaan bebek itu. Bebek-bebek itu sangat gemuk. Istrinya pasti senang mendapatkan bebek yang gemuk itu. Bur! Geek, geek, geek! Bebek-bebek itu dilemparkan ke sungai. Bebek-bebek itu bersahut-sahutan riang gembira. Mereka berenang ke sana ke mari. Membenamkan seluruh tubuhnya, lalu mengambang kembali. "Kurang ajar!" teriak Pan Belog. "Pedagang itu telah menipuku!" katanya. Lelaki bodoh itu mengira bebek-bebek itu adalah hewan palsu. Tubuhnya hanya terdiri dari bulu-bulu, sedangkan badannya kosong. Pan Belog meninggalkan bebek-bebek palsu itu. Ia pulang dan segera melaporkan perbuatan pedagang yang suka menipu itu. "Mana bebekmu? Dan mana uangmu?" tanya istrinya setelah melihat Pan Belog pulang dengan tangan hampa. "Aku ditipu oleh pedagang jahat itu!" kata Pan Belog marah-marah. Lalu ia menceritakan pengalamannya, mulai dari memilih bebek, menyerahkan sekeping ringgit, dan melepas bebek-bebek itu di sungai. "Bebek itu kosong. Hewan itu hanya terdiri dari bulu-bulu," kata Pan Belog menutup ceritanya. "Dasar dungu!" teriak istrinya marah-marah. "Bebek berenang dikira kosong!" Istrinya tambah marah setelah mengetahui suaminya tidak membawa uang kembalian. Sang istri mengambil sebilah kayu lalu mengancam suaminya. Pan Belog lari terbirit-birit. Ia kembali ke sungai untuk mengambil bebek-bebek itu. Tetapi di sana tak ada bebek yang berenang. Pan Belog and DuckOnce upon a time there was a man called Pan Belog. Pan Belog was very dumb (belog is a balinese language of dumb). In the village, he was famous for his stupidity. Many people mocked and laughed at him. He not only did not wanted to go to school, but he also did not wanted to work. But in front of his wife, he never refused the task. He did not like being called lazy, and also did not like being called stupid. "Daddy !" cried his wife one morning. "Today I am very busy. Would you please buy me a pair of ducks in the market. that duck will be used in-law's house for ceremony." After receiving the money, Pan Belog immediately went to the market. "Select a duck that is fat and heavy, Dad!" said his wife again. "yes, of course!" replied Pan Belog. When entering the market, he saw a lot of duck traders. "I would like to buy two ducks with this money!" he said to a merchant. The traders were surprised, because the buyer was simply taking two ducks and handed over ringgit coin. Actually, he still had money left, but he soon left and ignored the change. "What a strange man," thought the duck traders. "He did not bid and did not ask for any change," he thought again as he saves the ringgit coin. On the way home, Pan Belog went through a river which was deep. In the heart occurred, wanted to know the state of the duck, the ducks were very fat. His wife is definitely excited about getting the fat duck. Bur! Geek, geek, geek! The ducks were thrown into a river. The duck’s merry. They swim back and forth. Immerse the entire body, then floating back. "Brazen!" yelled pan Belog. "The merchant had tricked me!" he said. Stupid man thinks the ducks are fake animal. His body was only composed of the feathers, while the body is empty. Pan Belog left the fake ducks. He came home and immediately reported the act of traders who like to cheat it. "Where are your ducks? And where are your moneys?" asked his wife after seeing Pan Belog went home empty handed. “I was deceived by the evil merchants!" said pan Belog angrily. Then he described his experiences, from choosing a duck, handed a piece of the ringgit, and release the ducks in the stream. "The ducks were empty. The animals were consists only of feathers," said Pan Belog close the story. "What a fool!" cried his wife got angry. "Ducks swim mistakenly empty?!" His wife was more upset after finding out her husband did not bring change. The wife took a chip of wood and threatened her husband. Pan Belog ran. He returned to the river to retrieve the ducks. But there were no ducks that swam. Identify Past TenseParagraph 1The underline words are in past tense. "Ferdinand Porsche started work on the 'people's car' with money he received from the german government in 1934" - Because the event happened in the past, in 1934. "Then in 1938 he returned to Germany, founded Volkswagen GmbH and started production with his new American machinery in wolfsburg, lower saxony" - Same as the above sentence but in 1938. Paragraph 2Commercial production stopped during the war and the factory and its 9000 workers fell into British hands in 1945. After the war the British helped the local economy by ordering 20.000 cars but decided not to take over the company as they did not think it had a future. Reason : Because the writer use verb 2 in that sentence and the writer, retell what happened in 1945 Paragraph 3First sentence is one sentence of simple past tense because the incident occurred in 1949. The sentence is not only there are some words that turn into verb 2, for example, Went, Founded, Became and arrived but there are also some who used to be past tense 'was' in the phrase 'the VW beetle legend was born'. In addition to sentence 1, sentence 3 is also an example of a sentence past because they occurred in 1960 and there are limited and valued word which is the verb 2 of the limit and value. Paragraph 4The company continued its globalization by setting up its own production facilities in Australia (1957), Nigeria (1973) and Japan (1990) while expanding into the USA (1976) and Spain (1986) by buying car manufactures. The company also set up a joint venture in China (1982). Political events at the end of 1989 gave VW the opportunity to move into central Europe, where it soon began production in the former East Germany and expanded into the Czech Republic. Reason : Because the writer use verb 2 in those sentence and the time was in past. Paragraph 5There are no past tense sentences in this paragraph. Explain Indonesian Judiciary System in EnglishThe Indonesian judicial system comprises the Supreme Court and the Constitutional Court. The 2001 amendments to the Constitution of the Republic of Indonesia grant the Supreme Court and the Constitutional Court powers to organize judiciaries in order to uphold justice and law. The constitution provides the Constitutional Court with the power, among other things, to review the constitutionality of legislation passed by the DPR, to determine jurisdiction disputes between key state institution, to decide motions for the dissolution of political parties and to resolve disputed election results. The judiciary subordinate to or under the oversight of the Supreme Court (Mahkamah Agung) comprises :
In Indonesia, most disputes appear before the courts of general judiciary, which consist of a court of First Instance, a Court of Appeal and a Court of Cassation. Although the Courts of First Instance and Courts of Appeal vary from one judicial system to another, at the cassation level the Supreme Court (Mahkamah Agung) will preside over cases in all judicial systems. The Courts in the general judiciary comprise the District Courts (Pengadilan Negeri) as Courts of First Instance, the High Courts (Pengadilan Tinggi) as Courts of Appeal, and the Supreme Court (Mahkamah Agung) as the Court of Cassation and civil review (Peninjauan Kembali). Write 20 Passive Sentences
Simple Present Tense Group AssignmentAlthough the present means now but this should not mean that such action is carried out at this time. Tense is used to express something that is fixed, customs or the ultimate truth, because it is often related to events in the past present and future, this tense at least have specific times information. English language sentences generally should have a subject and predicate, that’s why all tenses will be formulated like that. In the present tense generally, subject is a noun or pronouns and the predicate verb must. Affirmative Sentence Formula = S + V1(s or es)Example:
Negative Sentence Formula = S + do(es) not + V1Example:
Interrogative Sentence Formula = tobe/do(es) + S + V1Example:
If there were no other verbs in a sentence, then we use verb to be. Affirmative sentence formula is S + to be + noun / adjective / adverb Example:
Negative sentence are formed by placing not after to be. Example:
Interrogative sentence are formed by placing to be in front of the sentence. Example:
Absence NoteDenpasar, 11th Oktober 2010 To: I Nyoman Satya Kumara Department of Electrical Engineering Faculty of Engineering University of Udayana, Jimbaran, Bali. Dear Mr. Kumara My name is Fajar Purnama with my student number 1004405045, English class A. I would like to tell you that today October 11th 2010 I cannot attend your lesson because I have a very important meeting at Alfa Prima that discuss about my graduation certificate about video shooting and editing tutor. I also attact my dispensation note, I’m looking forward to attend to your next lesson. Best Regards (signatures) Fajar Purnama & Alfa Prima Direct and Indirect SpeechLet's include a bonus assignment I found from my Highschool times. Mirror
NoteThis is my undergraduate assignment that I translated to English in the Electric Field Theory course where my task is to write an essay on the Amperes Law and Magnetic Fields. Apart from me this group consists of Vencisisca Jeane R, Rr. Sanita Eling Cipta Nesa, Putu Arie Pratama, Fajar Purnama, Muhammad Audy Bazly, Muhammad Nordiansyah. This assignment has never been published anywhere and we as the authors and the copyright holders license this task customized CC-BY-SA where anyone can share, copy, republish and sell on condition to state our name as the author and inform that the original and open version available here. Chapter 1 Introduction1.1 BackgroundIn everyday life, many applications of several physical laws occur, one of which is Ampere's law and magnetic fields. Where in general the relationship between Ampere's law and magnetic fields, namely the Ampere's law states that the magnetic field can be generated in two ways, namely through an electric current (the initial formulation of the Ampere law), and by changing the electric field (Maxwell's addition). Maxwell's correction of the Ampere law is quite important, thus this law states that changes in the electric field can give rise to a magnetic field, and vice versa. Three genius scientists from France, Andre Marie Ampere (1775-1863), Jean Baptista Biot (1774-1862) and Victor Savart (1803-1862) stated that the force will be generated by an electric current flowing in a conductor that is between the magnetic fields. This is also the reverse of Faraday's law, in which Faraday predicts that an induced voltage will arise in a moving conductor and cut across the magnetic field. This law is applied to electric machines, and the image below will explain this phenomenon. 1.2 ProblemThe problems raised in this assignment are as follows:
1.3 ObjectiveThe main purpose of writing the assignment "Ampere Law and Magnetic Field" this time is to know and understand in detail about Ampere's law and magnetic fields. The other objectives of this paper are:
1.4 BenefitThe benefits obtained from the paper "Ampere Law and Magnetic Field" are as follows:
1.5 Scope of MaterialIn this assignment, the scope discussed by the author is limited to the issues discussed, namely the Ampere Law and Magnetic Fields. Chapter 2 Discussion2.1 Biot-Savart LawThe magnetic field differential, dH is the result of the current element differential I dH. The field is inversely proportional to the distance (r2), is a free medium that is around it and has a direction which is the cross product of I dI and aR. This relationship is known as the Biot-Savart Law, where the equation can be, seen as below: dH = (I dI x aR)/(4ÏR2) (A/m) The direction of R must come from the current element at the point where dH has been determined, as in the following figure: Current elements must not be separated. All elements complement the current filament contribution to H and the current must be involved. The integral form in Biot-Savart's Law is as follows: H = â®(I dI x aR)/(4ÏR2) A simple closed integral requires all the current elements involved in obtaining the H. Example Problem 1: Current I is long and straight along the z-axis of the cylindrical coordinates as shown in the figure below. Without losing any of its general properties, choose a point in the z = 0 plane. Then in its differential form, it is as follows: dH = (I dz ax X (rar X zaz) / (4Ï(r2+z2)<</sup>sup>(3â2)) = (I dz raâ ) / (4Ï(r2+z2)(3â2)) H = [â«-ââ(Ir dz) / (4Ï(r2+z2)(3â2))] aâ = aâ /2Ïr The magnetic field by surface currents and volume is also given by the Biot-Savart law of integral form, where I dI is replaced by K dS or Jdv respectively, and where the integral is taken over the entire surface, or volume, concerned. An important example is the current in an infinite plane with a constant density K. Where the equation can be seen as follows: H = K/2 X an 2.2 Ampere LawThe line integral of the tangential component H along the closed path is equal to the magnitude of the current in the vicinity: â®H.dI = Ienc This is Ampere's law. At first sight, we might think that the application of this law is to determine flow by an integration. In fact, usually the current is known and this law will give us a way of determining H. So the application of the law is very similar to using Gauss's law to determine D in a given charge distribution. To be able to take advantage of Ampere's law in determining H there must be a sufficiently high degree of symmetry to the problem being discussed. The two conditions that must be met are as follows:
The Biot-Savart law can be used to determine which path meets these conditions. But in most cases, the path is immediately visible. Example Problem 2: Use the amperes law to get H by a long, straight current I. The Biot-Savart law shows that H is tangential and with the same magnitude along the circle in Figure 2.3, then the equation is as follows: â®H.dI=H(2Ïr)=I H = aÏ/2Ïr 2.3 CurlThe curl of the vector field A is another vector field. Point P in Figure 2.3 is located in the area âS which is bounded by closed curve C. In the integration that defines curl, C is the area traversed by the curl so that the closed area is on the left. Normal units, determined using the rule of thumb, are as shown in the figure. Thus, the curl component of A in the direction an is defined as follows: (curl A).an = lim(âSâ0)(â®A.dI/âS) In the coordinate system, curl A is the fully specified value defined by the component along the three vector units. For example, the x component of Cartesian coordinates is defined by taking the contour line C of the square in the plane x = conts, via the point P, as shown in Figure 2.5: (curl A).an = lim(ây âzâ0) â¡(â®A.dI / ây âz) If, A = Axax + Ayay + Azaz, at the angle from closed âS to the center (point 1), then: â® = â«12 + â«23 + â«34 + â«41 =Ayây + (Az+(âAz/âyây))âz + (Ay+(âAy/âzâz))(-ây) + Az(-âz) =((âAz/ây)-(âAy/âz)) âyâz (curl A).ax = (âAz/ây)-(âAz/âz) The y and z components can be determined in the same way. The combination of the three components can be seen in the equation below: curl A = ((âAz/ây)-(âAz/âz)) ax+((âAx)/âz-(âAz)/âx) ay+((âAy)/âx-(âAx)/âx) az (cartesian) The third-order determinant can be written like the equation below, the expansion of which gives the Cartesian curl of A. curl A=|(ax&ay&az @ â/âx&â/ây&â/âz @ Ax&Ay&Az)| The elements of the second line are components of the del operation. This shows that â à A can be written for curl A. As with other expressions of a vector analysis, this notation is used for curl A in other coordinate systems, even though à A is defined in Cartesian coordinates only. The expressions for curl A at the coordinates of the cylinder and the sphere can be derived in the same way as above. Although, with a higher difficulty. curl A = (1/r (âAz)/(ââ ) - (âAâ /âz)) ar + ((âAr/âz) - (âAz/âr)) aâ + ((â(rAâ ))/âr - (âAr/ââ )) az (cylinder) curl A = 1/(r sinâ¡ ) [(â(Aâ sinâ¡Î¸))/âθ - (âθ/ââ )] ar+1/r [1/sinâ¡Î¸ (âAr/ââ )-(â(rAâ )/âr)] aâ + 1/r [(â(rAâ ))/âr-(âAr)/(ââ )] az (spherical) The frequency of use of the two properties of the curl operator can be explained as follows:
2.4 The relationship of J and HIn the law of amperes, the equation definition of (curl H) x can be written as follows: (curl H).ax=lim(ây âzâ0)â¡Ix/(ây âz)- Jx Where Jx = dlxâdS is the area of density in x direction of current. So that the x component of curl H and direction of current J are the same at every point. Likewise for the x and y components, it can be seen as follows. âÃH=J This is one of Maxwell's equations in the static electric field. if H is known for the entire region, then â à H = J will produce J for the region. Sample Problem 3: CatatanIni merupakan tugas S1 saya di mata kuliah Teori Medan Listrik dimana tugasnya adalah menulis essai mengenai hukum ampere dan medan magnetik. Selain saya kelompok ini terdiri dari Vencisisca Jeane R, Rr. Sanita Eling Cipta Nesa, Putu Arie Pratama, Fajar Purnama, Muhammad Audy Bazly, Muhamad Nordiansyah. Tugas ini tidak pernah dipublikasi dimanapun dan kami sebagai penulis dan pemegang hak cipta melisensi tugas ini customized CC-BY-SA dimana siapa saja boleh membagi, menyalin, mempublikasi ulang, dan menjualnya dengan syarat mencatumkan nama kami sebagai penulis dan memberitahu bahwa versi asli dan terbuka tersedia disini. BAB 1 Pendahuluan1.1 Latar BelakangDalam kehidupan sehari-hari banyak penerapan dari beberapa hukum-hukum fisika yang terjadi, salah satunya yaitu hukum ampere dan medan magnetik. Dimana secara umum hubungan antara hukum ampere dan medan magnetik, yaitu hukum ampere menyatakan bahwa medan magnet dapat ditimbulkan melalui dua cara yaitu lewat arus listrik (perumusan awal hukum ampere), dan dengan mengubah medan listrik (tambahan Maxwell). Koreksi Maxwell terhadap hukum ampere cukup penting, dengan demikian hukum ini menyatakan bahwa perubahan medan listrik dapat menimbulkan medan magnet, dan sebaliknya. Tiga orang ilmuwan jenius dari perancis, Andre Marie Ampere (1775-1863), Jean Baptista Biot (1774-1862) dan Victor Savart (1803-1862) menyatakan bahwa gaya akan dihasilkan oleh arus listrik yang mengalir pada suatu penghantar yang berada diantara medan magnetik. Hal ini juga merupakan kebalikan dari hukum Faraday, dimana Faraday memprediksikan bahwa tegangan induksi akan timbul pada penghantar yang bergerak dan memotong medan magnetik. Hukum ini diaplikasikan pada mesin-mesin listrik, dan gambar dibawah ini akan menjelaskan mengenai fenomena tersebut. 1.2 Rumusan MasalahAdapun permasalahan yang diangkat dalam makalah ini adalah sebagai berikut:
1.3 TujuanTujuan utama dari penulisan makalah “ Hukum Ampere dan Medan Magnetik “ kali ini adalah untuk mengetahui dan memahami secara rinci mengenai hukum ampere dan medan magnetik. Adapun tujuan lain dari pembuatan makalah ini adalah:
1.4 ManfaatManfaat yang diperoleh dari makalah “ Hukum Ampere dan Medan Magnetik “ ini adalah sebagai berikut:
1.5 Ruang Lingkup MateriDalam makalah ini, ruang lingkup yang dibahas oleh penulis hanya sebatas mengenai permasalahan yang di bahas, yaitu sebatas Hukum Ampere dan Medan Magnetik. BAB 2 Pembahasan2.1 Hukum Biot-SavartDifferensial medan magnetik, dH merupakan hasil dari differensial elemen arus I dH. Medan berbanding terbalik dengan jarak (r2), merupakan media bebas yang ada sekitarnya dan memiliki arah yang merupakan cross product dari I dI dan aR .Hubungan ini diketahui sebagai Hukum Biot-Savart, dimana dapat persamaan tersebut, dilihat seperi dibawah ini : dH = (I dI x aR)/(4πR2) (A/m) Arah dari R harus berasal dari elemen arus pada titik dimana dH sudah ditentukan, seperti pada gambar berikut: Elemen arus tidak boleh dipisahkan. Semua elemen melengkapi kontribusi filament arus ke H dan arus harus terlibat. Bentuk integral dalam Hukum Biot-Savart adalah sebagai berikut: H = ∮(I dI x aR)/(4πR2) Integral tertutup sederhana membutuhkan semua elemen arus yang dilibatkan dalam memperoleh nilai H. Contoh Soal 1: Arus I yang panjang dan lurus sepanjang sumbu z dari koordinat silindris adalah seperti tampak pada gambar dibawah ini. Tanpa kehilangan sesuatu sifat umumnya, pilih suatu titik dalam bidang z = 0. Maka dalam bentuk differensialnya, adalah sebagai berikut: dH = (I dz ax X (rar X zaz) / (4π(r2+z2)<</sup>sup>(3⁄2)) = (I dz ra∅) / (4π(r2+z2)(3⁄2)) H = [∫-∞∞(Ir dz) / (4π(r2+z2)(3⁄2))] a∅ = a∅/2πr Medan magnetik oleh arus permukaan dan volume juga diberikan oleh hukum Biot-Savart bentuk integral, dengan I dI digantikan oleh K dS atau Jdv masing-masingnya, dan dimana integral itu diambil diseluruh permukaan, atau volume, yang bersangkutan. Contoh penting adalah arus pada bidang datar tak berhingga dengan kerapatan K yang konstan. Dimana persamaannya dapat dilihat sebagai berikut ini: H = K/2 X an 2.2 Hukum AmpereIntegral garis dari komponen tangensial H sepanjang lintasan tertutup adalah sama dengan besarnya arus yang berada di sekitar lintasan itu: ∮H.dI = Ienc Ini merupakan hukum Ampere. Pada pengamatan pertama, kita barangkali akan mengira bahwa penerapan hukum ini adalah untuk menentukan arus dengan suatu integrasi. Padahal, biasanya arusnya telah dikenal dan hukum ini akan memberi kita cara menentukan H. Jadi penerapan hukum tadi sangat serupa dengan penggunaan hukum Gauss untuk menentukan D dalam distribusi muatan yang diberikan. Untuk dapat memanfaatkan hukum Ampere dalam menentukan H haruslah ada simetri bertaraf cukup tinggi pada masalah yang dibahas. Dua syarat yang harus dipenuhi, adalah sebagai berikut:
Hukum Biot-Savart dapat digunakan untuk menentukan dalam memilih lintasan yang memenuhi syarat-syarat itu. Tapi dalam banyak hal, lintasan tersebut akan segera terlihat. Contoh Soal 2: Gunakan hukum ampere untuk memperoleh H oleh arus I yang panjang dan lurus. Hukum Biot-Savart menunjukkan H adalah tangensial dan dengan besar yang sama sepanjang lingkaran pada gambar 2.3, Maka persamaannya adalah sebagai berikut: ∮H.dI=H(2πr)=I H = aϕ/2πr 2.3 CurlCurl dari medan vektor A merupakan medan vektor yang lain. Titik P pada gambar 2.3 terletak di area ∆S yang dibatasi oleh kuva tertutup C. Dalam integrasi yang mendefinisikan curl, C merupakan area yang dilalui oleh curl sehingga area yang tertutup berada disebelah kiri. Unit normal an , ditentukan dengan menggunakan aturan kaedah tangan kanan, seperti yang ditunjukkan pada gambar. Maka, komponen curl dari A dalam arah an akan didefinisikan sebagai berikut: (curl A).an = lim(∆S→0)(∮A.dI/∆S) Dalam sistem koordinat, curl A merupakan nilai spesifikasi sepenuhnya yang ditentukan oleh komponen di sepanjang tiga unit vektor tersebut. Sebagai contoh, komponen x pada koordinat kartesian didefinisikan dengan cara mengambil garis kontur C persegi pada bidang x = conts, melalui titik P, seperti yang ditunjukkan pada gambar 2.5: (curl A).an = lim(∆y ∆z→0) (∮A.dI / ∆y ∆z) Jika, A = Axax + Ayay + Azaz , pada sudut dari ∆S tertutup ke titik pusat (titik 1), kemudian: ∮ = ∫12 + ∫23 + ∫34 + ∫41 =Ay∆y + (Az+(∂Az/∂y∆y))∆z + (Ay+(∂Ay/∂z∆z))(-∆y) + Az(-∆z) =((∂Az/∂y)-(∂Ay/∂z)) ∆y∆z (curl A).ax = (∂Az/∂y)-(∂Az/∂z) Untuk komponen y dan z dapat ditentukan dengan cara yang sama. Kombinasi ketiga komponen, dapat dilihat pada persamaan di bawah ini: curl A = ((∂Az/∂y)-(∂Az/∂z)) ax+((∂Ax)/∂z-(∂Az)/∂x) ay+((∂Ay)/∂x-(∂Ax)/∂x) az (cartesian) Penentu urutan ketiga dapat ditulis seperti persamaan di bawah ini, ekspansi yang memberikan curl Cartesian dari A. curl A=|(ax&ay&az @ ∂/∂x&∂/∂y&∂/∂z @ Ax&Ay&Az)| Elemen dari baris kedua merupakan komponen dari operasi del. Ini menunjukkan bahwa ∇×A dapat ditulis untuk curl A. Seperti pada ekspresi lain dari suatu analisis vektor, notasi ini digunakan untuk curl A dalam sistem koordinat lain, meskipun∇×A hanya didefinisikan dalam koordinat Cartesian saja. Ekspresi untuk curl A pada koordinat silinder dan bola dapat diturunkan dengan cara yang sama seperti di atas. Meskipun, dengan kesulitan yang lebih tinggi. curl A = (1/r (∂Az)/(∂∅) - (∂A∅/∂z)) ar + ((∂Ar/∂z) - (∂Az/∂r)) a∅ + ((∂(rA∅))/∂r - (∂Ar/∂∅)) az (silinder) curl A = 1/(r sin ) [(∂(A∅ sinθ))/∂θ - (∂θ/∂∅)] ar+1/r [1/sinθ (∂Ar/∂∅)-(∂(rA∅)/∂r)] a∅ + 1/r [(∂(rA∅))/∂r-(∂Ar)/(∂∅)] az (sperikal) Frekuensi penggunaan dari dua sifat operator curl, dapat dijelaskan sebagai berikut:
2.4 Hubungan dari J dan HPada hukum ampere, definisi persamaan dari (curl H)x dapat ditulis sebagai berikut: (curl H).ax=lim(∆y ∆z→0)Ix/(∆y ∆z)- Jx Dimana Jx=dlx⁄dS merupakan daerah kerapatan dari x arah arus. Sehingga komponen x dari curl H dan arah arus J sama pada setiap titik. Demikian pula pada komponen x dan y, dapat dilihat sebagai berikut. ∇×H=J Ini merupakan salah satu persamaan dari Maxwell yang terdapat pada medan listrik statis. jika H diketahui pada seluruh daerah, maka ∇×H=J akan menghasilkan J untuk daerah tersebut. Contoh Soal 3: NoteThis is my undergraduate assignment already in English in the Environmental Studies and Occupational Health & Safety course and I remembered that I was asked to write in Indonesian next time due to that time, English language was not yet supported. Here, I chose a topic about the server room in Global Development Learning Network (GDLN) Udayana University (UNUD) because I have human connections and was able to access there. GDLN back then in 2012 was a place to house the main computer and telecommunication network of the university and a place to perform any kind of distant communication activities such as video conferences and distant learnings. This task has never been published anywhere and I as the author and copyright holders license this task customized CC-BY-SA where anyone can share, copy, republish, and sell it on condition that to state our name as the author and notify that the original and open version available here. AbstractA good server room is a server room that last long or last forever. There are lots of things to consider before planning a server room. Even though we have the things necessary to create a server room but it will only be good for that time. We also must guard the condition of the server room as time pass. Here we will discuss about the physical and virtual safety and security of server room and data center from unwanted threats. Keywords: Server Room, Data Center, Safety, Security, Threat, Physical, Virtual. 1. IntroductionNowadays electronic media are use by almost all people in the world, whether they are for studying, working, entertainment and many other things. These electronic media help civilization to quickly and efficiently finish their jobs. Before, people rely on books, papers, drawing pad and manual equipments to work. These methods took much time and much energy which is very low efficient compare to modern civilization. With human instinct to always want to make life much easier, efficient and flashier, technology will always grow. Thus with new technology being discovered through the continue flow of time there’s always a possibility a new threat or negative impact exist with the new discovered invention. Even though we were able to create a new technology ready to use like server and data center but it doesn’t stop there. After it is useable we must also learn how to take care of this technology. There’s no point a technology created ready to use if it doesn’t last long. So in this assignment we will discuss considerations needed in a server room or data center. In information technology, server is defined as a hardware system to fulfill the request of clients the services could be database server, file server, mail server, print server, web servers, or other. The server here we’ll be discussing is a physical computer. A data center is a facility to house computer systems and associated components, telecommunication and storage. A server room is a place to house servers. Small server can cause large noise and cause great heating to a large room. A large server is even worse. So a standard room and air conditioning isn’t enough to satisfy the demands of storage, for servers. Other than that the safety and security must be considered. Another additional thing that must be considered is the size of the server room. A fixed space is rather risky because it will provide insufficient space to store backups, maintenance and it will be unavailable for upgrading. If there are damage parts replacing it will be difficult due to small or none extra space. So a large extra space is recommended. An ideal server room should have cooling from air conditioner, ventilation for free air cooling, a UPS system to guard the server from instant shutdown, a diesel powered generator in order to keep it alive longer incase the electricity is down, a fire suppressor to minimize the risk of fire, ladders or raised floors in order to access the systems, a false ceiling to place cables and air conditioner, lighting system to provide good vision, environmental monitoring is a strong mean to protect the server room, security construction for the protection, in advance a CCTV and alarms, access control systems is the next thing after security, data cabinet to simplify cable structure, cool aisle containment for extra cooling, cabling is also affecting, and intelligent patching for the server itself. An ideal server room can be said if those things available. In this article we will discuss about what are the cause of server failure, what endanger the servers and how we respond to them. The dangers can either come from inside or outside the room itself, the cause could be by humans or environmental. A server can also be damage due to faulty installation. There are variety of things that could be done and the tools are developing as time pass. So we will discuss them in general. 2. Safety and Security Measures2.1 Threats2.1.1 Environment Factor2.1.1.1 Inner ThreatsInner threats are threats that are potential from inside the room for housing the server itself (from room server). The threats we could mention here are potential of fire, faulty electrical system, faulty room temperature or temperature produced by hardware, short circuit (unstructured cable), faulty room keeping, and faulty room architecture. 2.1.1.2 Outer ThreatsOuther threats are threats that are potential from outside the room for housing the server itself (outside room server). The threats we could mention here are fire from outside, pests, bugs, floods, moisture, outside temperature, thunder, and earthquake. Thunder flood and earthquake can be label as natural disaster. 2.1.2 Human FactorHumans also plays a major role, since servers are sensitive even the smallest faulty can cause great damage. The simple damage that humans can cause is due by clumsiness. We must always be careful in a server room. The other one is insufficient knowledge about the server and the server room itself. 2.1.3 Virtual FactorVirtual factor can either be data overload, faulty in the program, virus and malware, and hacking. Another threat is the loss of data. 2.2 Server Failure (Impacts from Threats)2.2.1 Small Damage – Severe DamageThis kind of damage can be short time malfunction or a repairable damage. A high temperature can cause start failure, hardware malfunction which can be fix if cooled down but a continual damage can cause permanent damage. It’s basic computer knowledge. Another additional damage is hard disks are made of metal. It’s not the heat that is the main problem. It’s because the effect of the heat that’s causing servers or any CPU to stop instantly. Stopping the work of CPU without proper procedure is the cause of severe damage. It can be picture as a human who’s shock. 2.2.2 Fatal DamageFatal damage here means the breakdown of a server. A high voltage can cause a server to explode. It can be expected for most computers. A high voltage can either be from the source itself or from thunders. A faulty electrical system can cause short-circuit or SPOF (single point of failure). Earthquake and faulty room architecture could cause physical damage to servers due to physical impacts. This could permanently damage a server. 2.3 Physical Security and Safety2.3.1 Building2.3.1.1 LocationNullify disasters, like unsusceptible to fire, strong against tremor, earthquake, vibration. set a current/voltage stabilizer to prevent unstable current/voltage from thunder or the source itself. 2.3.1.2 Inner SecurityInside the buildings must be secure. CCTV is recommended for security, fire sensor to detect fire, access by people must be recorded and only those permitted can access, instead of using wall use glass so it’s transparent and easy to watch. 2.3.1.3 Outer SecurityThe surrounding environment around ± 10 meter of the building must be ground zero, empty. Place CCTV outside, anti terrorist motive like a bomb detector. Beyond the empty ground place a park, lots of trees so the building is isolated and easy to monitor. 2.3.2 Fire PotentialTo plan protection from fire potential, we must first examine the cause of the risk of fire. With different type of cause of fire, the chemicals used to put them out are different each type. Fire sensors and alarms are crucial, instant water spray as soon as fire detected is advisable. A fire panel and a fire extinguisher is essential within the room. 2.3.3 TemperatureBoth the server and the room temperature must be considered. Other than keeping the server cooled using hardware fans, we must approximate the heat produce by each server. By knowing the average heat produced we estimate the maximum amount of servers allowed in a room. To control the room temperature, ventilation and air conductors are advised, air conditioner is an excellent choice not only to control the room temperature in normal terms but to control the room temperature when problem occurs where heat suddenly raise up. The room temperature should be 72°F (±2°F) and humidity 45% (±5%). 2.3.4 ElectricitySince servers are sensitive to electricity, a power supply must be chose carefully. Set a current/voltage stabilizer to prevent unstable current/voltage from thunder or the source itself. Calculating the total amount of power needed is the next thing. To prevent damage from black out (electricity go out) a UPS is recommended. Cables should be well isolated so a short circuit does not occur. Between servers and other machines (AC, mechanical) is recommended for the power supply to be separated. The power must not exceed 300 watts per square foot.
2.3.5 Environmental IssueThe danger of environmental issue depends on the construction and the location of the building. Preventing damage from natural disaster is not too recommended on this time. The technology we bare is still insufficient, instead we rely on backups. 2.3.6 Hardware CareHardware care is an important issue to keep the hardware in a good condition for long time. Simply frequently clean the hardware and check often. There are special methods to take care of different hardware. 2.4 Virtual Security and Safety2.4.1 Data SafetyTo guard the data from unwanted user is to place security on the access. The basic security is to place a username and password. It’s best to change the username and password overtime to make sure it’s secure. In modern days fingertip sensors are used to tighten security. Virus and malware protection, firewall, and so-on is recommended to protect the server from virtual threats. To create a tight security, seek a professional. 2.4.2 BackupA regular backup is recommended to minimalize the data loss due to unwanted problems. While a disaster can destroy an entire data, with backup the data is copied and instead of starting from a scratch, we use the backup to retrieve the loss data. 3. Server Room in GDLN (Global Developing Learning Network) at Udayana University, Sudirman, Denpasar, Bali.The location of the building is isolated around 10 meters. It’s a strategic from the disaster of floods. Still, the surrounding the area is crowded. The location of the server room is on the 2nd floor of GDLN building. The access to the server room is secured by a pin lock and normal lock. There are 2 doors to enter the room secured by a lock. Half of the walls are brick walls and half of them are glasses. There are no windows for safety reason. Within the room, the size of the room is about 6.5 x 5 meters wide. 5.5 x 5 meters area is use for the server but there are still spaces left in that area. There is a free space about 1 x 5 meters wide. The height of the room is 3 meters. The ISP (internet server provider) used is Tellabs, Tellabs is the brand of the machine. It provides data rate (people usually say bandwidth) of metro gigabytes (higher than one gigabytes). Some server that are used are Sun Fire x 4106, Aten, HP, some CPU modified into server and maybe others that can’t be mention. There is one terminal to control the entire server. There is also a TV antenna VHF (very high frequency) and UHF (ultra high frequency) for video streaming on the web. There is a wireless router for HOTSPOT UNUD. The switch that is use is G First Base TX. There are also some routers to connect on south GDLN, library, Pasca Sarjana building and others. There is also a rack to organize cables which is called wall mount with the brand fortuna. The cables then go behind the walls or above the ceiling to connect to other places that are necessary. For the safety, security and care of the room will be explain in following. There are 4 AC (air conditioner in the room) 1 big one and 3 normal ones use in normal room, at home for example. With that the room temperature is maintained 170C. There is 1 phone, 1 IP camera with a brand of Sony, 1 fire panel and 1 UPS. The UPS is used in case of a black out (electricity go out). The UPS is SENDON model: SX-530K, 30KVA 3 Phase in 1 Phase out, uninterruptible Power Supply, also a diesel type powered generator if extra power is needed. The lighting of the room is standard (the same as normal room). Within the free space or other place of the buildings there is also other equipment such as ladders to satisfy the needs of the server room. 4. ConclusionThe consideration needed in a server room is to know the risk, things that could be harmful the server, how the server work and its limits. After that then we can plan the security and safety whether it is in physical or virtual manner. A good server is not a server that is good at that time but a server that last long. How we take care of them affects the life span of a server and the storage itself such as how the rooms must be set. An ideal server room should have cooling (AC), ventilation, a UPS, a diesel powered generator, a fire system, ladders or raised floors, a false ceiling, lighting system, environmental monitoring, security construction, in advance a CCTV and alarms, access control systems, data cabinet, cool aisle containment, cabling, and intelligent patching for the server itself. Judging from the criteria above GDLN server room is an ideal room server. The only problem for GDLN server room is the place, it is not isolated, crowded outside, most of the security is still manual but tight (manual locks). It’s not an issue but the security is still moderate not as advance as it is provided with fingertip scanner, face scanner, ID card scanner and so-on. Otherwise everything is complete. 5. Attachment5.1 UCSD (University of California, San Diego) Server Room StandardsThe following standards provide campus units with information on how to design or retrofit small to medium size computer server rooms. Following these standards will help to ensure that critical computational resources are maintained in an environment that protects them both during normal operation, as well as in the event of power failures, fires, floods, and other emergency conditions. For more information, or for questions regarding these standards, contact [email protected]. 5.1.1 General Space Characteristics5.1.1.1 Room specifications
5.1.1.2 Equipment
5.1.1.3 Fire prevention
5.1.2 CoolingAn under floor air distribution system is preferred, although ducted systems are acceptable. In either system, racks should be arranged in a hot isle/cold isle configuration. If under floor, minimum height should be 24" and the raised floor must be designed to accommodate the weight of fully loaded server racks, as well as any lifting and transportation devices used in the movement of racks, computational equipment, and ancillary support systems. 5.1.3 Mechanical Systems5.1.3.1 Air conditioning (AC)
5.1.3.2 Future Planning
5.1.4 Electrical Systems5.1.4.1 Capacity and quality
5.1.4.2 Emergency planning
5.1.5 Alarms and Security5.1.5.1 Alarm systems
5.1.5.2 SecurityAll entrances to the room should be properly secured and alarmed where appropriate. 6. Reference
NoteThis is my undergraduate assignment that I translated to English myself in the Data Communication course where my assignment is to write an essay on flow control, error detection and control, and selective repeat ARQ. Apart from me, this group consists of I Gede Ariana, I Made Dwi Angga Pratama, I Putu Arie Pratama, Yulianti Murprayana, I Wayan Alit Wigunawan, I Gusti Made Widiarsana, I Nym Apriana Arta Putra, Muhammad Audy Bazly, I Kadek Agus Riki Gunawan, Muhamad Nordiansyah. This task has never been published anywhere and we as the authors and the copyright holders license this task customized CC-BY-SA where anyone can share, copy, republish, and sell on condition to state our name as the author and notify that the original and open version available here. Chapter 1 Introduction1.1 BackgroundThe development of computer technology is increasing very rapidly, this can be seen in the 80s that computer networks are still a puzzle that academics want to answer, and in 1988 computer networks began to be used in universities, companies, and now. Entering this millennium era, especially WWW (World Wide Web) has become the daily reality of millions of people on this earth. In addition, network hardware and software have really changed, at the beginning of its development almost all networks were built from coaxial cables, now many of them are built from fiber optics (fiber optics) or wireless communication. With the development of computer and communication technology, a single computer model that serves all the computing tasks of an organization has now been replaced by a collection of computers that are separate but interconnected in carrying out their duties, such a system is called a computer network. Two computers are said to be interconnected if they can exchange information. The form of connection does not have to go through copper wire alone but can use optical fiber, microwave, or communication satellites. In a data communication, data packets are sent through a certain medium, there will always be a difference between the sent signal and the received signal. This difference can result in an error or error in the data packet sent so that the data cannot be read properly by the recipient. To avoid errors or errors in the data packets sent, error detection (error checking), error correction (error correction) and error control (error control) are required. In error control, there are three methods that are often used in data communication, namely stop and wait requests, go back N requests, and selective requests. Error control includes the following mechanisms: ACK/NAK, timeout, and sequence number. In error control, the following processes occur: error detection, acknowledgment, transmission after timeout, and negative acknowledgment. 1.2 ProblemThe formulations of the problems raised in this paper are as follows:
1.3 ObjectiveThe objectives of this paper are as follows:
1.4 Scope of MaterialIn this assignment, the scope discussed by the author is only limited to the issues discussed, which is limited to Selective Repeat ARQ in a data communication network, and also to provide an overview to readers about the process of controlling errors in data communication. Chapter 2 DiscussionThe purpose of error control is to deliver error-free frames in the correct order to the network layer. The technique commonly used for error control is based on two functions, namely:
Meanwhile, error control is divided into three, namely:
2.1 Flow ControlFlow control is a technique for ensuring that a sending station does not flood the receiving station with data. The receiving station will typically provide a data buffer of a specified length. When the data is received, it has to do some work before it can clear the buffer and prepare for the next data reception. A simple form of flow control known as stop and wait, it works as follows. The recipient indicates that it is ready to receive data by sending a poll or responding with select. The sender then sends the data. This flow control is regulated/managed by Data Link Control (DLC) or commonly referred to as Line Protocol so that the sending and receiving of thousands of messages can occur in the shortest possible time. The DLC must move data in efficient traffic. Communication lines should be used as level as possible, so that no station is idle while the other stations are saturated with excess traffic. So flow control is a very critical part of a network. The following shows the Time Flow Control Diagram when communication occurs in conditions without errors and errors. Flow control mechanisms that are commonly used are Stop and Wait and Sliding window. 2.2 Error Detection and CorrectionAs a result, the physical processes that cause errors in some media (for example, radio) tend to occur in bursts rather than one by one. Error bursting like that has both the advantage and the disadvantage of isolated single-bit errors. On the plus side, computer data is always sent in blocks of bits. Assume the block size is 1000 bits, and the error rate is 0.001 per bit. If the errors are independent, then most blocks will contain errors. If an error occurs with 100 bursts, then only one or two blocks in 100 blocks will be affected, on average. The disadvantage of burst errors is that they are more difficult to detect and correct than isolated errors. 2.2.1 Error Correction CodesThe network designers have devised two basic strategies regarding errors. The first way is to involve sufficient redundant information together with each block of data transmitted to allow the recipient to draw conclusions about what the transmitted character should be. Another way is to involve only enough redundancy to draw the conclusion that an error has occurred, and to allow it to request retransmission. The first strategy uses error-correcting codes, while the second strategy uses error-detecting codes. In order to understand error handling, it is necessary to take a close look at what errors are. Typically, a frame consists of m bits of data (i.e. messages) and redundant r, or check bits. Take the total length of n (that is, n = m + r). An n-bit unit of data and a checkbit is often associated with an n-bit codeword. Two codewords are specified: 10001001 and 10110001. Here we can determine how many different corresponding bits are. In this case, there are 3 different bits. To determine it, simply perform an EXCLUSIVE OR operation on both codewords, and count the number of bits 1 in the result of the operation. The number of bit positions where the two codewords differ is called the Hamming distance (Hamming, 1950). The thing to note is that if two codewords are separated by a Hamming distance d, it will take a single bit error d to convert from one to the other. In most data transmission applications, all 2m of data messages are legal data. However, due to the way the check bit is calculated, not all 2n are used. If an algorithm is specified for calculating the check bits, it is possible to generate a complete list of legal codewords. From this list two codewords with the minimum Hamming distance can be found. This distance is the Hamming distance for the complete code. The error detection and error correction properties of a code depend on the Hamming distance. To detect d errors, you need a code with a distance of d + 1 because with such a code it is impossible that a single bit error d can change one valid codeword to another valid codeword. When the receiver sees an invalid codeword, it can say that an error has occurred during transmission. Likewise, to fix error d, you need a code that is 2d + 1 apart because it says legal codewords can be separated even with a change to d, the original codeword will be closer than other codewords, so error fixes can be determined uniquely. As a simple example of error detection code, take a code where a single parity bit is appended to the data. The parity bit is chosen so that the number of 1 bits in the codeword is even (or odd). For example, if 10110101 is sent in even parity by adding a bit at the end, the data becomes 101101011, whereas with even parity 10110001 becomes 101100010. A code with a single parity bit has a distance of 2, because any single bit error results in a codeword with parity. wrong. This method can be used to detect a single error. As a simple example of error correction code, take a code that has only four valid codewords: 0000000000, 0000011111, 1111100000 and 1111111111. This code has a space of 5, which means that it can fix multiple errors. When the codeword 0000011111 arrives, the recipient will know that the original data should be 0000011111. However, if the triple error changes 0000000000 to 0000000111, the error cannot be corrected. Imagine that we are going to design code with m message bits and r check bits that will allow all single errors to be fixed. Each of the 2m legal messages requires an n + 1 bit pattern. Since the total number of bit patterns is 2 n, we must have (n + 1) 2 m ≤ 2 n. Using n = m + r, this requirement becomes (m + r + 1) ≤ 2 r. When m is specified, it places a lower limit on the number of check bits required to correct a single error. In fact, this theoretical lower limit can be obtained using the Hamming method. The codeword bits are numbered consecutively, starting with bit 1 on the far left. Bits that are powers of 2 (1,2,4,8,16 and so on) are check bits. The rest (3,5,6,7,9 and so on) are inserted with m bits of data. Each check bit forces the parity of a portion of the bit set, including itself, to be even (or odd). A bit can be included in multiple parity computations. To find the check bit to which the data bit at position k contributes, rewrite k as a sum to the powers of 2.For example, 11 = 1 + 2 + 8 and 29 = 1 + 4 + 8 + 16. A bit is checked by the check bit that occurs in its expansion. (for example, bit 11 is checked by bits 1, 2 and 8). When a codeword arrives, the receiver initializes the counter to zero. Then the codeword checks each check bit, k (k = 1, 2, 4, 8, ...) to see if it has the correct parity. If not, the codeword will add k to the counter. If the counter equals zero after all the check bits have been tested (that is, if all the check bits are true), the codeword will be accepted as valid. If the counter is not zero, the message contains an invalid number of bits. For example, if the check bits 1, 2, and 8 have an error, then the inversion bit is 11, because that's the only one checked by bits 1, 2, and 8. Figure 2.2 illustrates some of the 7-bit encoded ASCII characters as an 11 bit codeword using Hamming code. Note that the data is in the bit positions 3, 5, 6, 7, 9, 10, 11. Hamming code can only fix a single error. However, there is a trick that can be used to allow Hamming's code to fix popping errors. A consecutive k number of codewords are arranged as a matrix, one codeword per row. Typically, data will be transmitted one codeword line at a time, from left to right. To correct popped errors, data must be transmitted one column at a time, starting with the leftmost column. When all the k bits have been sent, the second column begins sending, and so on. When the frame arrives at the receiver, the matrix is reconstructed, one column per unit time. If an error burst occurs, at most 1 bit per k codeword will be affected. However Hamming code can fix one error per codeword, so the entire block can be fixed. This method uses the kr check bit to make km of data bits immune to single error bursts of length k or less. 2.3 Selective Repeat ARQSelective Repeat or also known as Selective-reject. With selective reject automatic repeat request (ARQ), the frames that will be sent are only those frames that receive a negative reply, in this case called SREJ or frames whose time has expired. The method of selective-reject ARQ in correcting errors is by at first the transmitter part sends a continuous stream of data from a continuous frame, on the receiving side the data is stored and a cyclic redundancy check (CRC) process is carried out. But this CRC process takes place on a continuous stream of data from the received frame. When an error frame is encountered, the receiver sends the information to the sender via the "return channel". The sending part then takes the frame from the data storage area and puts it in the transmission queue. There are several important points for frame readers, the first is that there must be a way to identify the frame. The second is that there has to be a good way to know if the frame is getting a positive reply or a negative one. Both of these important points can be solved by using sequential numbers sent and received. The sequential number that is sent is at the sender, as well as the sequential number that is received at the receiver. Received sequential numbers that are sent back on the sender's side are the sequential numbers sent by the sender side and get a positive reply from the receiving side. When the receiving side detects an error in the frame, the receiving side will send a sequential number that is sent along with the frame that is considered an error. Of course, in the end the receiving side has to rearrange the frames in the same order as the sending side before the data is passed on to the end user. Selective-reject ARQ is more efficient against Go-Back-N as it reduces the number of retransmissions. However, selective-reject requires a larger data storage capacity for both the sender and receiver side to store the frame until the damaged frame is retransmitted. In addition, on the receiver side there must also be software that can send frames out of sequence so that data can arrive in sequence to the end user. Selective repeat can be implemented in two ways:
From these two events, the frame event is received out of sequence, S holds this frame on the receiving channel until the next incoming frame sequence is received. In the case of implicit retransmission, assuming all ACK frames are received correctly, this can be explained as follows (Figure 2.3):
Whereas implicit retransmission assuming that all I-frames are received correctly except ACK frame N can be explained as follows.
The above operation relies on receiving the ACK frame associated with subsequent frames to initiate retransmission of the previous damaged frame. Another attempt is to use explicit negative acknowledgment frames to request retransmit the error frames. The negative acknowledgment is known as selective reject. On explicit requests, the assumption that acknowledgments are lost on the way can be explained as follows (see Figure 2.5 below).
Chapter 3 Closing3.1 ConclusionThe conclusions that can be drawn from this paper are as follows:
3.2 SuggestionAfter the authors have made this assignment, the suggestions the authors can suggest are, in sending data packets over a certain medium, there will always be a difference between the sent signal and the received signal. This difference can result in an error or error in the data packet sent so that the data cannot be read properly by the recipient. To avoid errors or errors in the data packet sent, error detection, error correction, and error control are required. So the reader should be able to recognize and know the errors that often occur in a data communication. Bibliography
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NoteThis is my undergraduate assignment that I translated myself in the Data Communication course, which was prepared so that readers in 2011 can find out how big the role and influence of Internet technology is in our daily lives. This assignment contains knowledge about the internet at large. Apart from me, our group consisted of Arya Putrawan, Dion Adi Putra, Vencysica Jeane, Sanita Eling Cipta Nesa, and Yulianti Murprayana. This task has never been published anywhere and we as the authors and the copyright holders license this task customized CC-BY-SA where anyone can share, copy, republish, and sell on condition that to state our name as the author and notify that the original and open version available here. Chapter 1 Introduction1.1 BackgroundNowadays computers can be found in almost every government office, company, school, or even household. The rapid development of computer technology, especially in the software sector, has made computers more user friendly and has made it a necessity for certain groups, such as businesses. In doing their work they are very dependent on computers. In the 20s, almost everyone knew and depended on the internet. Looking for information, communicating remotely instantly, entertainment can be accessed via the internet. 1.2 ObjectiveTo get to know the name "internet" and describe well the internet from ancient times to the present. Responding to the history of the internet, the impact of the internet on the global world, knowing how the internet works and its development. Chapter 2 Literature Review2.1 Definition of the InternetThe Internet is a global network of world computers, large and very broad where every computer is connected to one another from country to country around the world and contains various kinds of information, ranging from text, images, audio, video, and others. The Internet itself comes from the word Interconnection Networking, which means the connection of many computer networks of various types, using communication types such as telephone, etc. The networks that make up the Internet work based on a set of protocols. standards used to connect computer networks and address traffic on the network. This protocol set the allowable data format, error handling (error handling), traffic messages, and other communication standards. The standard protocol on the internet is known as TCP/IP (Transmission Control Protocol / Internet Protocol). This protocol has the ability to work on all types of computers, without being affected by differences in hardware or operating systems used. TCP (Transmission Control Protocol) is responsible for ensuring that all connections work properly, while IP (Internet Protocol) transmits data from one computer to another. TPC/IP generally functions to choose the best route for data transmission, choose an alternative route if a route cannot be used, organize and send data sending packets. In order to participate in using the Internet facility, you must subscribe to an existing ISP (Internet Service Provider) serving your area. This ISP is usually called an internet service provider. You can use facilities from Telkom such as Telkomnet Instant, speedy and also other ISP services such as first media, netzip and so on. 2.2 History of InternetInitially the United States Department of Defense (US Department of Defense) wanted to create a distributed computer network system by connecting computers in vital areas to solve problems in the event of a nuclear attack and to avoid centralized information, which in case of war could be easily destroyed. The first time it was used was the telegraph. Unfortunately the telegraph can only function optimally when the weather is good. Another device that was used was computers in ancient times. At that time the exchange of files between the central computer and the terminal was possible. The longer the elapsed time the connection distance can be for the terminal and the higher the speed for the interconnection. But technology at that time was a strategic and military risk because there was no alternative route to communication if attacked. Therefore research was carried out between two physically separate systems and resulted in a packet switching model for a digital network. Labs used include Vinton G. Cerf at Stanford University, Donald Davies (NPL), Paul Baran (RAND Corporation), and Leonard Kleinrock at MIT and at UCLA. This research resulted in the development of packet switching networks such as ARPANET, Telenet, and X.25 protocol. But these gateways are still limited and they want to produce an internetworking protocol where many different networks can combine into a super-framework network. By using the internet protocol (IP) system, the idea of a global network called the Internet developed.
2.3 The Basic Structure Of The Internet And How It WorksThe interconnecting network or the internet consists of hundreds of thousands of smaller networks that connect educational, commercial, non-profit, military and even individual organizations. This arrangement is called a server/client network. Client computers are computers that request data or services. The server or host computer is the central computer that provides the requested data or service. When a client computer requests information for various flights and ticket prices to the server computer, the server computer sends the information back to the client computer.
2.4 How computers understand data transmitted over the InternetWhen your modem is connected to a modem at a POP ISP location, the two modems then go into the handshaking process, which is looking for the highest possible transmission speed. Then comes the authentication process: your ISP must know who you are by checking your username and password. You will definitely get these two things when you start subscribing to an ISP.
2.4.1 Who Runs the Internet? What Does ICANN Do?Although no one has the internet, everyone on the network must comply with the standards set by the International Board of Trustees of ISOC, Internet Society (www.isoc.org). ISOC is a non-profit and professional community of 100 organizations and 200,000 individual members in more than 180 countries. Organizations that are members of ISOC consist of various companies, government agencies, and foundations. ISOC is a forum for tackling internet problems in the future and is the basis for groups that play a role in developing internet infrastructure standards. June 1998, the United States government proposed the creation of a series of non-profit companies to manage complex issues on the internet, such as fraud prevention, privacy issues and intellectual property protection. First is the International Corporation for Assigned Names and Numbers (ICANN), which was established to manage human-friendly domain names - that is, addresses ending in .com, .org, .net and others, in lieu of IP address numbers. to identify the type of website. ICANN (which can be accessed at www.icann.org) is a global, private and not-for-profit company that does not have statutory authority and enforces policies through an inter members around the world. After receiving criticism for being inefficient, in 2003 ICANN became ICANN 2.0 which was increasingly responsive and active to become a reference for the world internet community in adopting standards. One of the improvements is the ICANN Whois Database which is able to display the name and domain address entered (for example, by typing microsoft.com, the name and address of Microsoft Corp. will appear). However, various groups including the International Telecommunication Union, an agency under the auspices of the United Nations, have alleged that the United States through ICANN controls the internet too much, and several countries have proposed the existence of an international institution as a replacement for ICANN. In July 2005, the United States confirmed that it would maintain its role in Internet governance. Currently, IP addresses in North America, South America, the Caribbean, and sub-Saharan Africa are regulated by the American Registry for Internet Numbers (ARIN; www.arin.net). 2.5 Use of the Internet2.5.1 Internet as a Communication MediaSeveral phenomena and the advantages of the internet as a medium of information and communication compared to other media. Information obtained is easier, faster and cheaper with global reach. This is supported by the fact that to reach as many as 60 million users: it took 30 years for radio, it took 15 years for television, It took 3 years for the web with applications: Email, WWW, NewsGroup, FTP Gopher, and others. Online media sites have sprung up (whether printed media or not) have reduced paper costs and distribution costs, for example: Newspapers on the Internet (Kompas Cyber Media), Seconds, Satunet, CNN, magazines, brochures, etc.
2.6 Internet Negative Impact / LossDependence on the internet is starting to spread to big cities in Indonesia. Unfortunately not all of them have a positive impact, even so far internet users are more dominant in carrying out negative activities. In order to take appropriate action, it is necessary to have a clear and practical understanding of this unhealthy dependence on the internet. Addiction to the cyber world falls into five categories.
2.7 How Far Has the Internet Developed Until Now?
Internet of 2011In 1989, Timothy Berners-Lee, a computer engineer from England created the World Wide Web, a kind of program that allows sound, pictures, movies, music to be displayed on the internet. It is because of this invention that the internet has become more attractive in appearance and very varied. Previously the internet could only be used by certain groups and with certain components. But now people who are at home can also connect to the internet using a modem and telephone network. In addition, the Internet is widely used by companies, educational institutions, government agencies, military institutions around the world to provide information to the public. Apart from the above benefits, the internet also has a negative effect because the information on the internet is too free. So that it allows children to see various things that are not appropriate to see or read. How to access the internetIf at home we don't have a computer connected to the internet, we can take advantage of an internet cafe (internet cafe) or maybe a school computer laboratory that is already connected to the internet to find information. To search for information or data, you can click/press shortcut/image browser. if you use the Internet Explorer browser. Then fill in the address of the site addressed to the Address. To find information quickly, use search sites such as: yahoo.com, google.com, e-smartschool.com or others. After entering the search site, enter the keyword (keywords) you are looking for. The development of the internet and online gamesEntertainment in the form of games accessed through cyberspace, Online Games, since its emergence has been very popular with Indonesian gamers. The types are increasingly diverse, with various challenges offered. From time to time since they first entered Indonesia and were introduced to the community, the development of online games has shown a very fast growth along with technological developments. Many Indonesian private companies then buy game licenses to be marketed in Indonesia. This trend has directly or indirectly influenced the growth of game centers in Indonesia. Game Online Indonesia has entered a period of about 4 years with the launch of the first online game called Nexia by Bolehgame in early 2001. Many things have happened after that with the entry of several new game providers such as Ragnarok Online (RO) in 2003 which finally managed to make online games boom to its highest point, which caused chaos for Indonesia's internet connection because the available bandwidth at that time was insufficient1. If starting at the beginning of online games entering Indonesia, it can be said that until now he has been around seven years old. Chapter 3 Closing3.1 ConclusionInternet is the development of media in the field of communication systems. The reach of the internet has reached the entire world (planet earth). BibliographyNoteThis undergraduate assignment in the Data Security System course is a scientific version of previous tutorial. Actually, we were only given the task of writing an essay on bruteforce, but I happened to try Backtrack Linux at that time and decided to pratice the bruteforce with Hydra. Apart from me, our group consisted of Yulianti Murprayana, Nyoman Arta Jaya, Muhammad Audy Bazly, and Dwi Angga Pratama. This assignment has never been published anywhere and we as the author and copyright holder license this assignment customized CC-BY-SA where anyone can share, copy, republish, and sell it on condition that to state our name as the author and mention that the original and open version available here. If you just want to experiment, just follow the video.
Chapter 1 Introduction1.1 BackgroundBruteforce is a computer network breaching technique by trying all the words in the dictionary as a username and/or password to enter a network. From the word bruteforce itself means to force purely using force. For hackers, bruteforce is the last solution to breach computer networks. However, this technique is rarely used because it requires a long time, large dictionary files, high computer specs and other similar types. If the hacker's human resources are sufficient, this technique is sure to work. Although this technique is commonly known and understood by its mechanism of action, few people know its application. In other words, many know the theory but never take this action. In this paper, an experiment will be conducted to perform bruteforce with Hydra software available on the Linux operating system. The experimental material is the Windows 7 operating system on the telnet service. 1.2 ProblemHow to bruteforce with Hydra on telnet service in Windows 7? 1.3 ObjectiveApply the bruteforce breach technique with the Hydra software on the telnet service on Windows 7. 1.4 Benefit
1.5 Scope and Boundaries
Chapter 2 Literature ReviewBrute-force attacks work by counting every possible combination that can generate a password and testing it to see if it's the right one. As password lengths increase, the amount of time and required computing power to find the correct password increases exponentially. (https://en.wikipedia.org/wiki/Brute-force_attack). Some software that can perform brute force attacks:
Based on Zurück zur Startseite, The following is the development of the brute force attack news:
Chapter 3 Experimental Method3.1 Place and Time of ExperimentThe experiment was carried out at home at Jln. Kusuma Bangsa 5, Denpasar, Bali. Trial time on Monday, March 10, 2012, at 20:00 - 24:00. 3.2 Tools and MaterialsFollowing are the tools used for research: Laptop ACER:
Software:
The following are the materials used for research: PC:
3.3 Experiment Method3.3.1 Scan Host AliveThe first thing to do is to check whether the host is on or off. If the IP address is not known, you can perform scanning in a certain IP (Internet Protocol) address range or with ARP (Adress Resolution Protocol). If using nmap the command is “nmap –sn 192.168.0.0/24”, this command will check the host alive with the ping application from 192.168.0.0 - 192.168.0.255. 3.3.2 Scan portThe second is a port scan to find out which ports on the host are active with a port scanner application. The port scanner used in this paper is NMAP. If it is known that the host's IP address is 192.168.0.3 then the command is "nmap 192.168.0.3". In this paper the bruteforce experiments will be carried out on Telnet. Telnet access can be done with the command "telnet -l (user)". 3.3.3 BruteforceBruteforce in this paper will be done with the open source Hydra software. In this paper, an experimental dictionary is made in the form of a text file, which looks as follows: On the hydra you can do the command "hydra -h" to see the user manual. Next is the command “hydra –L /root/test_dictionary.txt –P /root/test_dictionary.txt –F –V 192.168.0.3 telnet”. "-L" is login, "-P" is password, here both of them will try all the text in the file "test_dictionary.txt". "–F" is command to stop Hydra when login and password have been found, -V to see the process. Chapter 4 Discussion4.1 Which is done by the HydraIn Figure 3.3, it can be seen that hydra tries the names contained in the test_dictionary.txt file as username and password. Hydra starts from above, namely username = robert and password = robert up to 21 attempts and stops at usernama = full moon and password = testhack. 4.2 Experiment ResultsWith the command "telnet 192.168.0.3" by entering username = full moon and password = testhack it will look as follows: It appears that it has successfully entered the host. From the experiments, bruteforce is time-consuming, wasteful of human resources such as RAM, processor and drive. If you apply this method in the real world, you will need a large dictionary of about more than 5 GB because the dictionary must provide all possible passwords ranging from variations of letters from a - z, numbers, and other characters. It doesn't stop there, there must also be all possible numbers of characters in one word, and each character must also have variations. Naturally, a real dictionary would have a large size. The speed to do bruteforce depends on the processor and RAM, in other words, a very large RAM and processor is required. If all the required human resources are met, then the bruteforce will work. Bruteforce is therefore said to be the last resort for hackers when other solutions don't work. Chapter 5 Closing5.1 ConclusionTo apply Bruteforce, you can install available software such as Hydra. After that you need a dictionary in the form of a collection of words in the txt file. The last stage before carrying out bruteforce is to search for information and connect the connection with the purpose of the bruteforce. Then do bruteforce with Hydra as shown in Figure 3.3. 5.2 SuggestionThere are also bruteforce software besides Hydra such as Bruteforce, Ophcrack and Rainbowcrack. But it does not cover the possibility of creating Bruteforce software. It can be suggested that it be used as further research by making bruteforce software yourself, trying other software, bruteforce other services, doing it in real conditions and so on. Questions and Answers (actually my midterm exam)Question
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