Spektra: Jurnal Fisika dan Aplikasinya
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ANALISIS DIAMETER KRITIS DAN SUHU CURIE BAHAN PARMALLOY FECOB BERBENTUK BOLA-NANO SERTA PENGARUH TEMPERATUR (HEAT ASSISTED) DENGAN MENGGUNAKAN PROGRAM SIMULASI MIKROMAGNETIK NMAG DAN VAMPIRE
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Bahan paduan magnet (parmalloy) FeCoB bersifat magnet kuat karena memiliki koersivitas medan magnetik yang kuat. Dari sifat yang dimiliki ini, FeCoB sangat cocok digunakan sebagai bahan piranti penyimpan data. Namun demikian, bahan parmalloy FeCoB ini akan mengalami perubahan sifat magnetnya ketika mendapat pengaruh temperatur (heat assisted) yang berubah-ubah dan dimensi (diameter bola) yang berbeda. Dengan adanya kondisi tersebut, diperlukan informasi yang cukup dari bahan parmalloy FeCoB agar menjadi efektif dan efisien ketika bahan ini digunakan sebagai bahan dasar hard-disk. Oleh karena itu, dilakukan analisis bahan parmalloy FeCoB yang terdiri dari dimensi diameter yang mempengaruhi perubahan sifat magnet (diameter kritis), suhu Curie akibat perubahan temperatur dan diameter bahan, serta kurva histerisisnya. Penelitian ini dilakukan dengan menggunakan program simulasi mikromagnetik Nmag dan Vampire. Hasil yang didapatkan dari bahan parmalloy FeCoB ini adalah memiliki diameter kritis sebesar 10 nm dan suhu Curie sebesar 700 K. Dari hasil ini dapat disimpulkan bahwa bahan parmalloy FeCoB akan efektif dan efisien sebagai bahan dasar hard-disk bila dimensi diameter yang digunakan di bawah diameteri kritis dan dioperasikan di bawah suhu Curie.
Kata-kata kunci: parmalloy, kurva histerisis, suhu Curie, heat assisted.
Abstract
The magnetic alloy material (parmalloy) FeCoB is strongly magnetic material category because it has strong coercivity. So, FeCoB is suitable for use as data storage device. However, the FeCoB will be changed of its magnetic properties when it used to varying temperatures (heat assisted) and different dimensions (spherical diameter). Therefore, some sufficient information is required from the material when this material is used as a hard-disk base material. An analysis of FeCoB parmalloy material consisting of diameter dimensions influencing the change of magnetic properties (critical diameter), Curie temperature due to changes in temperature and material diameter, and hysteresis curve. This research was using simulation of program micromagnetic are Nmag and Vampire. The results of this research are the critical diameter is 10 nm and value of Curie temperature is 700 K. The conclusion from that results is the material will be effective and efficient as the hard-disk base material when the diameter dimension is used under critical diameter. And it will be operated under Curie temperature.
Keywords: parmalloy, hysterisis curve, Curie temperature, heat assisted
ANALISIS KOMPLEKSITAS STRUKTUR PORI PADA SAMPEL DIGITAL MEDIUM BERPORI
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Kompleksitas struktur pori terhubung pada sampel digital medium berpori 2D telah dianalisis menggunakan parameter tortuositas. Jalur pori terhubung dilacak dengan menggunakan Simple Neurite Tracer. Metode pelacakan dan perhitungan tortuositas tersebut diujikan pada lima model sederhana yang menunjukan perbedaan tingkat kompleksitas yang signifikan. Metode analisis kompleksitas tersebut kemudian diterapkan pada sampel medium berpori berupa citra digital batuan berukuran 560 × 393 piksel, dan tanah berukuran 560 × 475 piksel. Citra digital sampel tanah dan batuan yang dianalisis berupa irisan 2D pada bidang z-y (sagittal) yang diambil dari sampel 3D hasil pemindaian menggunakan -CT Scanner SkyScan 1173. Pelacakan jalur pori terhubung pada sampel model maupun sampel digital 2D batuan dan tanah yang menggunakan Simple Neurite Tracer menghasilkan koordinat jalur pori terhubung yang kemudian digunakan untuk menghitung nilai tortuositas. Tortuositas dihitung dengan menggunakan definisi rasio antara jumlah total sudut keberlikuan jalur terhadap jarak antara dua sisi sampel yang saling berhadapan. Untuk 5 sampel model yang menunjukkan kompleksitas yang berbeda, diperoleh bahwa semakin kompleks struktur pori tersebut, maka semakin besar nilai tortuositasnya. Untuk analisis pada sampel digital batuan, nilai tortuositasnya yaitu 0,0392 sedangkan pada sampel tanah didapat nilai tortuositas sebesar 0,0431.
Kata-kata kunci: simple neurite tracer, tortuositas, kompleksitas, medium berpori
Abstract
The complexity of the connected pore structure of 2D porous digital media samples has been analyzed using tortuosity parameter. Connected pore was traced using the Simple Neurite Tracer. The tracing method and the tortuosity calculation were tested on five simple models showing significant differences in complexity levels. The complexity analysis method was then applied on digital image of a rock sample with the size of 560 × 393 pixels, and a soil sample with the size of 560 × 475 pixels. Digital images of the rock and soil samples were analyzed on the 2D slices in the zy (sagittal) plane which were obtained from the scanned 3D samples using the µ-CT SkyScan 1173 Scanner. Connected pore tracing for both the 2D models as well as the rock and soil samples was done using the Simple Neurite Tracer which produce the coordinate of the connected pore path which is then used to calculate the value of tortuosity. Tortuosity is calculated by using the definition of the ratio between the sum of the curvaceous angles of the connected pore path to the distance between two facing sides of the sample. For 5 sample models with distinctive complexity, it was found that the more complex the pore structure, the greater the tortuosity value. For analysis on digital samples of rocks, the tortuosity is 0.0392 whereas in the soil sample, the tortuosity is 0.0431.
Keywords: simple neurite tracer, tortuosity, complexity, porous medium
EDDY CURRENT SENSOR BERBASIS FLAT COIL FR4 UNTUK MENENTUKAN KETEBALAN PELAT LOGAM NON MAGNETIK AL
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Sensor arus eddy (eddy current) digunakan untuk pengukuran ketebalan logam khususnya logam non magnetik seperti alumunium. Penelitian ini telah mengembangkan sensor eddy current berbahan PCB (printed circuit board) jenis FR4 yang memiliki ketebalan lapisan tembaga 35micron. Prototipe yang dihasilkan mempergunakan koil sensor dengan jumlah gulungan (n) 30 lilitan, diameter (Æ) 30mm, lebar dan jarak antar koil, (dkoil) 0,254mm dan tahanan (Rkoil) sebesar 4,26Ω. Respon sensor ketebalan pelat logam terhadap bahan uji dievaluasi dengan memberikan eksitasi frekuensi tunggal 700Khz, 1MHz dan 1.33MHz. Rangkaian ketebalan pelat telah mempergunakan rangkaian pengunci fasa (phase locked loop) dan mampu mengukur variasi ketebalan mulai 0,2 mm sampai 2 mm, sementara jarak antara sensor dengan logam uji dijaga konstan 2 mm. Hasil pengukuran memberikan respon kurva U(t) dalam hubungan
Kata-kata kunci:sensor eddy current, PCB FR4, material non magnetik, ketebalan logam, rangkaian phase locked loop
Abstract
Eddy current sensor is used to measure the thickness of metals, especially non-magnetic metals such as aluminum. This research has developed eddy current sensor made from PCB (printed circuit board) type FR4 which has 35micron copper layer thickness. The developed prototype uses a designed coil sensor with the number of winding (n) 30 turn, diameter () 30mm, width and distance between coils, (dkoil) 0.254 mm and coil resistance (Rkoil) of 4.26 Ω. The sensor response to the test material was evaluated by giving a single frequency excitation of 700 Khz, 1 MHz and 1.33 MHz. The plate thickness electronics has used a phase locked loop circuit and is capable to measure the thickness variations from 0.2 mm up to 2 mm, while the distance between the sensor coil and the test object was kept constant at 2 mm. The measurement results give the U (t) curve response in the exponential relationship.
Keywords: eddy current sensor, PCB FR4, nonmagnetic material, thickness, phase locked loop circui
ANALISIS PEMANFAATAN DUA ELEMEN PELTIER PADA PENGONTROLAN TEMPERATUR AIR
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Elemen peltier bisa digunakan sebagai pemanas dan pendingin. Pada penelitian ini elemen peltier digunakan sebagai pendingin air. Tujuan dari penelitian ini adalah untuk membandingkan hasil pemakaian antara satu dan dua elemen peltier pada sistem kontrol temperatur air. Alat dirancang dengan menggunakan LM35 sebagai sensor temperatur dan mikrokontroler Atmega 8535 untuk mengontrol sebelum ditampilkan ke LCD. Sistem kontrol On-off digunakan pada sistem ini. Hasil penelitian menunjukkan bahwa kemampuan dari elemen peltier menurun seiring meningkatnya massa air. Kemampuan elemen pertier dalam melakukan proses pendinginan bergantung pada jenis transfer panasnya, walaupun dengan menggunakan satu elemen peltier, transfer panas dengan memanfaatkan heatsink dan fan lebih baik daripada menggunakan pompa menggunakan dua elemen peltier. Dua elemen peltier memiliki kemampuan menurunkan temperatur lebih cepat dimenit-menit awal, namun untuk mencapai keadaan set temperatur, satu elemen lebih cepat daripada dua elemen peltier untuk rangkaian yang berbeda. Cara transfer panas dari elemen peltier juga mempunyai pengaruh yang cukup besar pada kemampuan pendinginan air untuk mencapai temperatur minimum.
KataKunci: elemen peltier, sistem kontrol, temperatur air, pendingin
Abstract
Peltier element can be used as a heating or cooling in a system. In this research the peltier element is used as a cooler in water.The research purpose is to compare the result between one and two element peltier in water temperature control system. The prototype is designed using LM35 as temperature sensor and Atmega8535 microcontroller to process the output of the sensor before displayed on LCD. On-off control is used to control the system. The results show the ability of a Peltier element decreases with the increasing of the mass of water. The ability of peltier element in cooling system depent on heat transfer, eventough using one element, heat transfer using heat sink dan fan is better than using pump with two peltier element. Two element decreasing the temperatur faster than one in early cooling, but slower to reach setting temperature bu using this circuit. The way to transfer heat from peltier element also have significant effect to get minimum cooling temperature.
Keywords: peltier element, control system, water temperature, coolin
KORELASI POLARISASI MAGNET Z/H UNTUK IDENTIFIKASI PREKURSOR GEMPA DI SEKITAR PELABUHAN RATU
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Efek seismo-elektromagnetik yang berlangsung dalam rentang frekuensi luas yang mendahului gempa telah banyak dilaporkan dalam beberapa penelitian sebelumnya. Efek tersebut diharapkan dapat dimanfaatkan dalam mitigasi bencana gempa. Penelitian ini membahas penerapan metode korelasi polarisasi magnet komponen Z/H untuk mengidentifikasi prekursor gempa di sekitar Pelabuhan Ratu. Data yang dipergunakan adalah data magnet tiga komponen selama 31 hari sebelum kejadian gempa. Identifikasi anomali geomagnet dilakukan dengan menerapkan metode korelasi polarisasi magnet Z/H untuk menghitung rasio Simpangan koefisien korelasi (Skk) dengan Deviasi standar simpangan koefisien korelasi (Dskk). Ambang batas anomali adalah -1. Nilai Skk/Dskk < -1 mengindikasikan adanya anomali geomagnet. Kemunculan badai magnetik yang mempengaruhi anomali geomagnet dievaluasi menggunakan Disturbance storm time index (indeks Dst). Hasil penerapan metode korelasi polarisasi magnet Z/H pada lima kasus gempa di sekitar Pelabuhan Ratu dari Januari – Maret 2017 dengan magnitudo M > 4 dan memenuhi radius zona manisfestasi prekursor menunjukkan kemunculan anomali geomagnet yang dikategorikan sebagai prekursor gempa. Kemunculan anomali geomagnet berkisar antara 16 – 2 hari sebelum gempa terjadi.
Kata-kata kunci: korelasi, geomagnet, prekursor gempa, Pelabuhan Ratu.
Abstract
Seismo-electromagnetic effects occurring in wide frequency range that preceded earthquake have been widely reported in several previous studies. The effect is expected to be utilized in earthquake disaster mitigation. This study discusses application of magnetic polarization correlation method of Z / H component to identify earthquake precursors around Pelabuhan Ratu. Data used are three components magnet data for 31 days before earthquake events. Identification of magnetic anomaly was done by applying the magnetic polarization Z / H method to calculate correlation coefficient ratio (Skk) with standard deviation of correlation coefficient deviation (Dskk). The anomaly threshold is -1. Less than -1 of Skk / Dskk values indicate geomagnetic anomaly. The emergence of geomagnetic storms that affect geomagnetic anomalies is evaluated using the Disturbance storm time index (Dst index). The result of application of Z / H magnet polarization correlation method in five earthquake cases around Pelabuhan Ratu from January to March 2017 with magnitude M > 4 and meeting precursor manifestation radius zone showed the occurrence of geomagnetic anomalies categorized as earthquake precursors. The appearance of geomagnetic anomalies ranged from 16 to 2 days before earthquakes occurred.
Keywords: correlation, geomagnetic, earthquake precursor, Pelabuhan Ratu
TUMBUKAN TAK-ELASTIK PARTIKEL SEBAGAI MODEL TERBENTUKNYA ASTEROID
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Suatu asteroid diduga merupakan kumpulan partikel yang bertumbukan tak-elastik sehingga membentuk suatu agregat. Ikatan yang terjadi antar partikel diasumsikan hanyalah disebabkan gaya gravitasi. Gaya normal diperkenalkan untuk mencegah dua partikel berada pada posisi yang sama akibat gaya gravitasi. Parameter kontaktopi diperkenalkan dan teramati bahwa nilainya bertambah dengan semakin padatnya susunan agregat dan pada akhirnya akan mencapai nilai saturasi. Dalam sistem yang disimulasikan dengan jumlah partikel N = 22 diperoleh bahwa kontaktopi mencapai nilai saturasi pada C = 35.
Kata-kata kunci: partikel granular, dinamika molekuler, asteroid, kompaksi.
Abstract
An asteroid is assumed to be constucted from particles inealastic collision, which later forms an agregate of particles. Binding between particles is caused only by gravitational force. Normal force is introduced to prevent two particles collapsing into single point as they are colliding and attracted to to each other due to gravitational force. Contactotpy as parameter is presented and it is observed that its value increasing as the agregate becoming denser, and at the end it achieves saturation value. In the simulated system with number of particles N = 22 it is obtained that the contactopy reaches saturation value C = 35.
Keywords: granular particles, molecular dynamics, asteroid, compactio
ANALISIS PENGARUH SUHU MINYAK KELAPA SAWIT (CPO) TERHADAP NILAI TAHANAN TERMAL MEMPERGUNAKAN PEMODELAN KURVA I(V) ISOTERMAL SENSOR PTC
Get PDFPTC level sensor for overfill protection works based on the thermal resistance (Rw). The sensor cannot identify high-temperature fluid in the container and determine the pump switching status “ON†and “OFFâ€Â. This is due to the influence of the medium temperature on the Rw. Analysis is performed by observing the Rw value of crude palm oil (CPO) as a result of the storage temperature. The Rw value was obtained from the modeling of I (U) sensor curve of EPCOS B59050D1100 with temperature variations ranging from 20°C to 80°C. The modeled area is then determined using the isothermal curve and is resulted Rw value of 110.2K/W. The ambient temperature influence on Rw can be modeled after polynomial equation. Compare to the previous air measurement, the thermal resistance in CPO has 62.6% vary than in the air. This value can be used to determine the position of the level sensor switch safely.
Keywords: level sensors, PTC, thermal resistance, CPO, isotherma
INVESTIGASI PEMBENTUKKAN IKATAN Zn-O RODS DI ATAS PERMUKAAN MIKROKANTILEVER DENGAN UJI KARAKTERISASI FTIR
Get PDFIn this work, ZnO (Zinc Oxide) rods, which is a sensitive material for gas detection, are grown on a microcantilever surface by hydrothermal technique. Synthesis of ZnO rods consists of two processes, i.e., a formation of seed layer using Zinc Acetate Dihydrate by a dip-coating and a growth of the ZnO rods using Zinc-Nitrate-Tetrahydrate at a temperature 95°C for time variations of 2 hours, 4 hours and 6 hours. Drying condition for both seed layer and growth of ZnO rods was done at a temperature of 120 oC for 2 hours. The ZnO rods were then characterized by Fourier Transform Infrared (FTIR) in order to investigate the formation of Zn-O bond. The characterization results indicate that the metal oxide correlation is shown in the wavenumber spectrum of 540 cm-1 for a sample with 2-hour growth time, while the wavenumber spectrum of 548 cm-1 and 547 cm-1 for the growth time of ZnO rods for 4 hours and 6 hours. Wavenumber spectrum approximately at 540-548 cm-1 is predicted to be the absorption of the formation of a Zn-O bond.
Keyword: Microcantilever, ZnO rods, dip-coating, hydrothermal, growth time dependent