Spektra: Jurnal Fisika dan Aplikasinya
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REVIEW: MENENTUKAN PERBANDINGAN JARIJARI IONIK ATOM KECIL DENGAN ATOM BESAR (R/R) PADA STRUKTUR KRISTAL OKTAHEDRON DAN KUBUS
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Struktur kristal oktahedron dan kubus menarik untuk dikaiji ulang (review) agar dapat membekali pemahaman mahasiswa dalam menganalisis perbandingan jari-jari ionik atom kecil dengan jari-jari ionik atom besar (r/R) sebagai penyusun molekul dalam bahan keramik maupun kajian difraksi sinar-X dalam mata kuliah fisika modern. Kajian perbandingan (r/R) pada struktur kristal oktahedron (berbilangan koordinasi 6) diperoleh hasil perbandingan (r/R) dalam selang 0,414 – 0,732, sedangkan kubus (bilangan koordinasi 8) diperoleh hasil perbandingan (r/R) dalam selang 0,732 - 1. Contoh senyawa berstruktur oktahedron adalah NaCl, karena jari-jari ionik Na+ sebesar 0,102 nm dan jari-jari ionik Clsebesar 0,181 nm, sedangkan contoh senyawa berstruktur kubus adalah CsCl, karena jari-jari ionik Cs+ sebesar 0,170 nm.
Kata kunci: Jari-jari ionik, kubus, oktahedron, perbandingan r/R, struktur kristal.
Abstract
Octahedral and cubic crystal structure was interesting to be reviewed in order to provide an understanding to the students for analyzing the ionic radius ratio of small and large atoms (r/R) as molecul composer in ceramic materials and x-ray diffraction in modern physics chapter. Study of ratio on octahedron crystal structure (coordination number of 6) theorem resulted r/R ratio in range 0.414 0.732, while cubic structures (coordination number of 8) theorem resulted r/R ratio in range 0.732 - 1. For example octahedron structure is NaCl, because Na+ radii is 0.102 nm and Clradii is 0.181 nm, while for example cubic is CsCl, because Cs+ radii is 0.170 nm.
Key words: crystal structure, cubic, ionic radius, octahedron, ratio of r/R,
ANALISA PENGARUH REDUKSI TERMAL TERHADAP KERUSAKAN STRUKTUR (STRUCTURAL-DISORDER) PADA LAPISAN TIPIS GRAPHENE OXIDE TEREDUKSI
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Tujuan penelitian ini adalah menganalisa kerusakan struktur pada lapisan tipis graphene oxide setelah direduksi pada temperatur reduksi yang bervariasi. Lapisan tipis graphene oxide yang disintesis menggunakan metode Hummers direduksi secara termal pada variasi temperatur 3500C dan 8500C selama 2 jam dalam pemanas vakum (~10-3Torr). Kuantitas defect sampel dikarakterisasi menggunakan Raman Spectroscopy sedangkan mikrostrukturnya dikarakterisasi menggunakan SEM (Scanning Electron Microscope). Persentase (kuantitas) defect pada graphene oxide dinyatakan dengan ID/IG. Nilai ID/IG graphene oxide, graphene oxide tereduksi pada temperatur 3500C dan 8500C secara berurutan adalah 0.958, 0.823 dan 1.102. Nilai ID/IG tersebut menunjukkan bahwa kuantitas defect graphene oxide berkurang setelah direduksi pada suhu 3500C tetapi bertambah saat direduksi pada suhu 8500C. Hasil gambar SEM menunjukkan bahwa lapisan tipis graphene oxide menkerut setalah direduksi pada temperatur 3500C dan berubah menjadi material seperti graphite berpori (porous stacked-layer graphite) setelah direduksi pada temperatur 8500C.
Kata-kata kunci: graphene oxide tereduksi, reduksi termal, kerusakan struktur.
Abstract
The aim of this research is to analyse the structural-defect of graphene oxide reduced at various reduction temperatures. Graphene oxide thin film synthesized by Hummers method was thermally reduced at the temperature of 3500C and 8500C for 2 hours in vacuum condition (~10-3 Torr). The presence of defects was characterized by Raman spectroscopy while the material’s microstructure was characterized by SEM (Scanning Electron Microscope). A measure of defects existing on graphene oxide was represented by a ratio of D peak intensity and G peak intensity (ID/IG). The ID/IG value of raphene oxide and graphene oxide which is thermally reduced at 3500C and 8500C was 0.598, 0.823 and 1.102, respectively. Those ID/IG indicated that the quantity of defect was diminished after thermal reduction at 3500C, yet it was increased after severe thermal reduction at 8500C. SEM images of samples indicated the wrinkled graphene oxide thin film after thermal reduction at 350 0C and it formed a porous stacked-graphite like material after severe thermal reduction at 8500C
Keywords: reduced graphene oxide, thermal reduction, structural disorder
PENGARUH TEGANGAN TABUNG (KV) TERHADAP KUALITAS CITRA RADIOGRAFI PESAWAT SINAR-X DIGITAL RADIOGRAPHY (DR) PADA PHANTOM ABDOMEN
Get PDFThe measurement of image quality of Digital Radiography (DR) with using the abdomen phantom. Image take with low kV to high kV for 10 times exposure. Image processing is done using the image application. The resulting radiograph image is analyzed by FFT analysis, Histogram and Gaussian Filter. In the FFT analysis the radiographic image tends to differ according to the tube voltage variation of 40 kV to 85 kV. In the radiographic image histogram analysis, including the imperfect image category because the distribution of pixel distribution is not yet complete in the gray scale area for all exposure variations. In the analysis using Gaussian filters the resulting radiographic image tends to be the same so that although using low kV and high kV the image will be the same. The use of Gaussian filters can help reduce the use of high kV on abdominal examination and reduce exposure to radiation dose.
Keywords: Digital Radiography, Image Quality, Fourier Transform Filter, Gaussian Filter, Histogram
PENGARUH PANJANG STACK SELUBUNG KABEL TERHADAP PERUBAHAN SUHU PADA SISTEM PENDINGIN TERMOAKUSTIK
Get PDFResearch on environmentally friendly thermo-acoustic coolants uses a heat exchanger from the cable sheath material. The resonator tube used in the thermoelectric cooler is a 5.25 cm diameter PVC (polyvinyl chloride) tube with a length of 87 cm. Variations in stack lengths of 4cm, 5cm, 6cm, 7cm, and 8cm were performed to obtain results on thermoelectric coolers. Results are available on the use of stack length 4 cm high temperature 21.6 oC from the initial temperature), the stack length 5 cm high temperature 21.1 oC from the initial temperature (room temperature), the stack length of 6 cm resulted in a maximum temperature drop of 22.6 oC from the initial temperature (room temperature), the stack length of 7 cm resulted in a maximum temperature drop of 22.0 oC from the initial temperature (room temperature), while the stack length of 8 cm resulted in a decrease in temperature maximum of 23.3 oC from the initial temperature (room temperature).
Keywords: Thermoacoustic, stack, temperature changes
IDENTIFIKASI KANDUNGAN UNSUR-UNSUR VARIETAS SERBUK KOPI DENGAN TEKNIK LASER INDUCED SHOCK WAVE PLASMA SPECTROSCOPY
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Telah dilakukan penelitian untuk mengidentifikasi kandungan unsur- unsur varietas kopi dengan teknik Laser Induced Shock Wave Plasma Spectroscopy (LISPS). Varietas kopi yang digunakan adalah kopi luwak, kopi jawa dan kopi toraja. Ketiga sampel kopi semula berbentuk serbuk dan diberi perlakuan awal dengan dibentuk pellet agar serbuk kopi menjadi padat. Sampel pellet kopi diletakkan dalam sebuah ruang vakum yang bisa diatur tekanan udaranya. Agar dihasilkan emisi plasma, sampel pellet kopi ditembak oleh laser Nd:YAG (1064 nm) dengan variasi energi 12 mJ dan 45 mJ. Untuk setiap variasi energi dilakukan variasi tekanan udara yaitu 5, 15 dan 35 torr. Emisi plasma yang dihasilkan ditangkap oleh spektrometer dan ditransmisikan ke monitor. Gambar spektrum emisi ditampilkan di monitor. Hasil penelitian menunjukkan bahwa teknik ini bisa digunakan untuk mengidentifikasi kandungan unsur-unsur kopi dan memberikan hasil analisa yang cepat dan real time. Untuk energi terendah 12 mJ dan 45 mJ garis spektrumnya sudah terlihat cukup tajam. Elemen yang dikandung ketiga varietas kopi yaitu Ca(Kalsium), K(Kalium), Mg (Magnesium) dan H(Hidrogen). Hasil eksperimen menunjukkan bahwa spektrum emisi paling tajam terlihat pada (45 mJ, 5torr). Dan dari ketiga sampel, kopi luwak memiliki spektrum paling tajam.
Kata Kunci : Laser Induced Shock Wave Plasma Spectroscopy (LISPS), Teknik Ablasi Laser, Identifikasi Unsur Kopi
Abstract
Research to identify the elements of varieties of coffee powder with Laser Induced Shock Wave Plasma Spectroscopy LISPS have done. Varieties of coffees used are civet coffee, java coffee and toraja coffee. The samples were originally in powder and those made into pellets. Sample were put in a vacuum chamber that can be set the air pressure. Laser Nd:YAG(1064 nm) irradiated sample and produce plasma with energy variation 12 mJ and 45 mJ. For each energy variation is given pressure variation 5, 15 and 35 Torr. Plasma emission recorded by spectrometer and spectrum emission shown on the monitor. The result of research show that this method can be used for identify the elements of coffee powder and gives a fast and real time analysis. Spectrum emission already look good at 12 mJ and 45 mJ. Elements of the three varieties of coffee are Ca (calcium), K (Potassium), Mg( Magnesium) and H(Hydrogen). The result of this research showed that the best spectrum emission shown at (45 mJ,5 Torr), and the best spectrum emission among three samples of coffe is civet coffee.
Keywords: Laser Induced Shock Wave Plasma Spectroscopy (LISPS), Laser Ablation Technique, Identify the elements of coffee
SUBSURFACE VELOCITY MODEL FROM INVERSION OF H/V SPECTRAL RATIO OF AMBIENT NOISE RECORDS
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The Horizontal-to-Vertical (H/V) spectral ratio method uses continuous ambient noise records has been used extensively to study the characteristics of site response due to the earthquake occurrence. Sources of ambient noise are usually from human activities or natural excitations and might be composed of body and surface wave components. Several studies have investigated the possibility to extract information on the shallow subsurface model from the inversion of H/V spectral ratio. In this study, we investigated the shallow subsurface velocity model below two broadband seismometers at Simeulue Island, Aceh. Two broadband seismometers of PUTR and LEWK were selected because of the relatively clear peak amplitude of H/V spectral ratios, which may reflect the existence of strong impedance contrast. The initial models are set to be fixed of five homogeneous medium layers with the last medium to be infinite homogeneous medium. By setting fixed layer boundaries in the inversion process, the velocities in the medium may vary to obtain the most suitable fitting to the observed H/V spectral ratio. From the inversion process, we suggest we suggest that the strong impedance contrasts may occur on the shallow part of the medium at 2 up to 15 m depth.
Keywords: ambient noise records, H/V spectral ratio, inversion process
PERBANDINGAN HASIL EKSPERIMEN SUPERPOSISI GELOMBANG BUNYI BONANG BARUNG SECARA SIMULTAN DAN MIXING BERBANTUAN AUDACITY DAN MATLAB
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Bonang dapat dimainkan secara simultan dari dua nada yang sama dengan satu oktaf terpisah, sehingga muncul fenomena superposisi. Untuk mengamati perbedaan dalam waveform dan spektrum superposisi untuk berbagai warna suara bonang barung, audacity digunakan dalam penelitian ini untuk merekam dan menganalisis bunyi bonang barung. Perangkat lunak MATLAB digunakan untuk mengolah data dari domain waktu ke domain frekuensi. Objek penelitian adalah satu set bonang barung laras pelog Gending Bahana yang terbuat dari besi. Pencon bonang barung dipukul secara terpisah dan dipukul secara simultan. Hasil rekaman bonang barung yang dipukul secara terpisah kemudian di-mix dengan fasilitas mix and render pada audacity. Kemudian dianalisis dengan spektrum plot dan menghasilkan nilai frekuensi dasar dan frekuensi-frekuensi harmonik. Selain dianalisis dengan menu analisis pada audacity, hasil rekaman bunyi bonang barung dapat dianalisis dengan program FFT pada perangkat lunak MATLAB. Perbandingan hasil superposisi mix dengan superposisi simultan dengan audacity persentasenya berkisar dari 0% sampai dengan 2%, sedangkan perbandingan hasil analisis superposisi dengan program pada MATLAB persentasenya berkisar dari 0% sampai dengan 0,4%. Perbedaan frekuensi superposisi dengan audacity dan MATLAB terjadi karena MATLAB dapat menambahkan suara yang sangat rendah. Hasil superposisi yang diperoleh dari hasil mix dan simultan nilainya masih berada pada rentang yang hampir sama. Sehingga pada saat dipukul, hasil superposisi mix dan simultan akan terdengar sama oleh orang yang mendengarnya karena frekuensi dan amplitudonya hampir sama meskipun terdapat beda fase.
Kata-kata kunci: audacity, bonang barung, FFT, MATLAB, dan Superposisi.
Abstract
Bonang can be played simultaneously on the same two-tone one octave apart, so it appears the phenomenon of superposition. To observe the differences in superposition waveform and spectrum of various timbres of bonang barung, the audacity software was employed. It is used to record and analyse the sound bonang barung, and MATLAB software to process data from the time domain to the frequency domain. The object of research is a set pelog bonang barung Gending Bahana made of iron. The research was conducted by recording of bonang barung sounds using software audacity. Pencon bonang barungs were beaten separately and simultaneously. The recorded sound of bonang barung that is beaten separately then mixed with mix and rendering facilities in audacity. Then the recorded sounds analyzed by spectral plots for producing the fundamental and harmonic frequencies. Besides analyzed with analysis menu on audacity, recordings of sound bonang barung can be analyzed with FFT program in MATLAB software. The results showed that comparison of the results of mix and simultaneous superposition with audacity percentage ranged from 0% to 2%, while the comparison of the results of superposition analysis with MATLAB program on the percentage ranged from 0% to 0,4%. Superposition results obtained from the mix and simultaneous value remained at almost the same range. So that when struck, mix and simultaneous superposition result will sound the same by those who hear it because of the frequency and the amplitude is almost as though there is a phase difference.
Keywords: audacity, bonang barung, FFT, MATLAB, and superposition
STRUKTUR KRISTAL DAN KOMPOSISI KIMIA SEMIKONDUKTOR CD(SE0,6TE0,4) HASIL PREPARASI DENGAN METODE BRIDGMAN
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Telah dilakukan penumbuhan kristal bahan semikonduktor Cd(Se0,6Te0,4) dengan metode Bridgman. Penelitian ini bertujuan mengetahui komposisi kimia, parameter kisi, struktur kristal dan morfologi kristal bahan semikonduktor Cd(Se0,6Te0,4). Pemanasan tahap pertama dari suhu 27°C>200°C>250°C>300°C masing-masing 1 jam, 400°C (2 jam), lalu furnace dimatikan hingga 27 °C (2,25 jam). Tahap kedua dilakukan16 jam kemudian, dimulai dari suhu 27°C>200°C>300°C masingmasing 30 menit, ke 400°C dan 500°C masing-masing 1 jam, 600°C (2 jam), furnace dimatikan hingga 27°C. Penelitian menggunakan 4 sampel, melalui kerakterisasi XRD dan penghitungan parameter kisi menggunakan metode analitik dipilih sampel 4 (Cd=0,362 gram, Se=0,858 gram dan Te=0,390 gram) untuk diuji karakterisasi menggunakan EDAX dan SEM. Hasil karakterisasi XRD sampel 4 menunjukkan telah terbentuk fase Cd(Se0,6Te0,4) terkristalisasi dalam struktur heksagonal, dengan parameter kisi a=b=4,2941Ǻ dan c=6,9975Ǻ. Setelah dilakukan analisis SEM dan EDAX menunjukkan massif yang dihasilkan cukup homogen dengan perbandingan mol Cd:Se:Te=1:0.70:0.40.
Kata-kata kunci: Metode Bridgman, Struktur Kristal, Komposisi Kimia, Morfologi Permukaan Cd(Se0,6Te0,4)
Abstract
Has made crystal growing a semiconductor material Cd (Se0,6Te0,4) with Bridgman method. This study aims to determine the chemical composition, lattice parameters, crystal structure and morphology of crystalline semiconductor material Cd (Se0,6Te0,4). The first stage of the heating temperature of 27 ° C> 200 ° C> 250 ° C> 300 ° C respectively 1 hour, 400 ° C (2 hours), then the furnace was turned off to 27 ° C (2.25 hours). The second phase dilakukan16 hours later, starting from a temperature of 27 ° C> 200 ° C> 300 ° C each for 30 minutes, to 400 ° C and 500 ° C respectively 1 hour, 600 ° C (2 hours), the furnace was turned off up to 27 ° C.The study used four samples, through kerakterisasi XRD and calculation of lattice parameters using the analytical method selected sample 4 (Cd = 0.362 gram, Se and Te = 0.858 grams = 0.390 gram) to be tested using EDAX and SEM characterization. XRD characterization results have formed the sample 4 shows the phase Cd (Se0,6Te0,4) crystallizes in a hexagonal structure with lattice parameters a = b = c = 4,2941Ǻ and 6,9975Ǻ. After the analysis of SEM and EDAX showed massif produced quite homogenous with the mole ratio of Cd: Se: Te = 1: 0.70: 12:40.
Keywords: Bridgman method, crystal structure, chemical composition, surface morphology of Cd(Se0,6Te0,4
IMPLEMENTASI TEORI DISTRIBUSI PROBABILITAS GAUSSIAN PADA KUALITAS RANGKAIAN PENYEARAH GELOMBANG PENUH
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Penelitian ini bertujuan untuk memanfaatkan probabilitas distribusi Gaussian untuk membantu menentukan kualitas rangkaian penyearah gelombang penuh. Sebagai sampel digunakan dioda IN4002 dan IN4007 yang dihubungkan secara seri dengan tahanan 1.200 ohm. Rangkain dipasok dengan power supply 15 volt AC berfrekuensi 50 Hz. Data tegangan output diode dicuplik dengan bantuan sensor tegangan loggerpro pada setiap 5 detik sampai diperoleh 5000 data. Pengolahan data dilakukan dengan melakukan fitting data menurut distribusi probabilitas normal Gaussian. Kualitas penyearah ditentukan dari nilai simpangan baku yang kecil. Dari penelitian menunjukkan bahwa dioda 1N4002 mempunyai kualitas lebih baik sebagai komponen penyerah gelombang penuh dengan simpangan baku 0,39 %. Selain itu dari eksperimen ini dapat dihasilkan buku petunjuk praktikum yang layak digunakan untuk praktikum mahasiswa.
Kata-kata kunci: kualitas penyearah gelombang penuh, dioda, distribusi normal Gaussian.
Abstract
The objective of the research is employing Gaussian Distribution Probability to assist determination of quality of full wave rectifier circuit. Two diodes 1N4002 and 1N4007 were used as samples. The diodes were connected to resistor 1,200 ohm. The device was connected to 15 volt AC power supply with frequency of 15 Hz. Data were logged from diodes using loggerpro voltage sensor on each of 5 seconds up to 5000 data. Data was analyzed by fitting according to the Gaussian normal probability. The quality of device was determined from the lowest deviation standard. From the results show that diode 1N4002 have the best quality as an electronic component of full wave rectifier that have standard deviation of 0.39. Furthermore, from this research could be resulted a module of experiment that reliable if it is used as guidance book for experiment of students.
Keywords: full-wave rectifier quality, diode, Gaussian normal distribution
PEMANFAATAN DATA SATELIT HIMAWARI 8 UNTUK MENDETEKSI SEBARAN ASAP: STUDI KASUS DI KALIMANTAN DAN SUMATERA TANGGAL 8 DAN 9 SEPTEMBER 2015
Get PDFThe forest fires that occurred in the entire month of September 2015 was quite considerably disturbing many public activities in Borneo and Sumatera. The smoke which is caused by forest fire has negative impact for the surrounding environments, one of them is reducing horizontal visibility. Meteorological stations in Borneo and Sumatra recorded the lowest visibility occurred on September, 8th and 9th 2015 at average range was 100 m. Based on information of BMKG (Indonesian Agency of Meteorological, Climatological and Geophysics) noted that during the month of September 2015 there was a distribution of hotspots which indicates the occurrence of forest fire cases. This research is aimed to determine the potential of distribution of smoke by satellite imagery of Himawari 8 to reduce its negative impacts. By using this method that is by comparing the hotspot distribution data from BMKG with false color RGB image product (1 visible channel and 2 near infrared channel) along with trajectory of smoke’s distribution by utilizing application of GMSLPD SATAID. The distribution of smoke can be seen as an image with the brownish pattern which partially covered the area of Borneo and Sumatera. The result showed that the smoke’s distribution by the result of RGB imagery well-matched enough with the hotspot’s distribution data from BMKG, which the smoke almost covered most area of the western of Sumatera and center of Borneo. In this case also supported by the trajectory of smoke’s distribution which is derived from southeast-south and spread to the northwest-north in the researches area. By using the observation data from chosen meteorological stations showed a similar result with the above method. Thus, it can be assumed that by using satellite imagery of Himawari 8 is quite capable to discover smoke’s distribution caused by forest fires case.
Keywords: Smoke, Satellite, Himawari 8, SATAID