K Sofjan Firdausi
Jurusan Fisika, Universitas Diponegoro, Semarang

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KOMPARASI KUALITAS CITRA HASIL REKONSTRUKSI METODE ALGEBRAIC RECONSTRUCTION TECHNIQUE (ART) ADITIF DAN MULTIPLIKATIF (MART) PADA CT SCAN Anam, Choirul; Firdausi, K Sofjan
BERKALA FISIKA Vol 14, No 4 (2011): Berkala Fisika
Publisher : BERKALA FISIKA

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AbstractImage recontruction for CT scan by the methods of additive ART and muliplicative ART (MART) have been carried out using Malab software. The object used is Sheep-Logan phantomwith matrix size 50x50,  used a paralel beam and  angle interval 10, 50, 10,respectively. It is obtained that additive ART produces many artifacts, while MART producesfewer artifacts. Additive ART produces a contras between objects and background with relativelyhigh, while MART produces relatively lower contrast. It is obtained that in the additive ART,interval angle affects the quality of image. This does not happen to MART. So, the MARTreconstruct CT image faster, because it can be obtained relatively good image despite the angleinterval is large.Keywords: Image reconstruction, Additive ART, Multiplicative ART (MART)
STUDI UJI ALTERNATIF KUALITAS MINYAK GORENG BERDASARKAN PERUBAHAN POLARISASI CAHAYA TERIMBAS Susan, Ade Ika; Firdausi, K Sofjan; Setiabudi, Wahyu
BERKALA FISIKA Vol 14, No 4 (2011): Berkala Fisika
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AbstractIn this research, we report the quality of several cooking oils before and after heating. The parameter of quality was based on electrooptics characteristic or, so called, the change ofpolarization angle induced by external electric field. In this examination, it was used threedifferent brands of cooking oils. The samples were heated in the time interval between 0-120minutes. The electrooptics characteristic was determined by measuring the change ofpolarization angle of light as it passed through the oil while it was applied by external electricfield. The field was produced by two parallel plates connected to different potential between 0-9kV. The light source was diode laser atλ = 650 nm and λ = 532 nm. The quality of oil was then determined by average polarization angle per potential difference, i.e. α ≡ Δθ/ΔV. Based on the result of observation, the fresh oil before heated has smaller change of polarization angle thanoil after heated, which is in agreement to the previous study. The longer heating time is, morefree radicals are produced, which leads to higher polarization. It shows also that the change ofpolarization depends on the wavelength.  From two diode lasers, the effective wavelength toproduce higher number free radicals is obtained by 532 nm. The increasing average ofpolarization angle is linearly to the increasing of heating time. It is obvious that the electroopticsparameter could be proposed as an alternative quality test of cooking oil.Keyword: Cooking oil quality, Change of polarization angle, electrooptics
  AN IMPROVEMENT OF NEW TEST METHOD FOR DETERMINATION OF VEGETABLE OIL QUALITY BASED ON ELECTROOPTICS PARAMETER Firdausi, K Sofjan; Triyana, Kuwat; Susan, Ade Ika
BERKALA FISIKA Vol 15, No 3 (2012): Berkala Fisika
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An improvement of measurement for determination of frying oil quality has been conducted based on electrooptics parameter. The samples were several palm oils, coconuts oil, arefine olive oil, and a corn oil. The measured electrooptics parameter was the change of light polarizationθ through the samples within an external electric field, which leads to the increase oftransmitted lightζ, obtained by tabulating θ via Malus’ Law. The electric field was produced by high DC voltage power supply 0-10 kV on two parallel plates in a separated distance of circa 1 cm. The sources of light were red diode laser 5 mW (λ=650 nm), green diode laser 5 mW (λ=532 nm), He-Ne laser 1 mW (λ=633 nm), and a 100W-ligth bulb. For palm oils, the average value Δζwas approximately between 3×10-4 and 8×10-4. For coconuts oil and corn oil, Δζ was in the rangevalue of palm oils. However for refine olive oilΔζ was the smallest, out of the range and indicated minimum amount of free radicals. The electrooptics parameter here could classify various types offrying oils, distinguish between fresh oils and used oils, and also distinguish between edible oilsand expired oils.  This method could be an alternative quality test of frying oils. It conductedwithout additional treatments, relative simple, and quite accurate.Keywords: electrooptics, frying oil, polarization, transmitted light
SIFAT ELEKTROOPTIS SEBAGAI PARAMETER INDIKASI MUTU BERBAGAI JENIS MINYAK GORENG KEMASAN Murni, Sri; Firdausi, K Sofjan; Hidayanto, Eko; Bawono P, Ari
BERKALA FISIKA Vol 15, No 4 (2012): Berkala Fisika
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Abstract In this paper, we introduce the change of polarization angleβ induced by external electric field, as a quality indication of several edible oils without preliminary treatment. The averagevalue ofβ in the interval of applied potential difference plays important role as level of number offree radicals produced in the edible oils. The samples used were olive oil, extra olive oil, palm oil,and corn oil. Theβ value was obtained by measurement of the change polarization angle as the function of magnitude the electric field on the samples. The electric field was produced by DCvoltage power supply on two parallel plates in a separated distance of 2.5 cm and in area of 5 cm× 3 cm. The source of light used was He-Ne laser 1 mW (λ=633 nm). The experiment result showsthat for all the fresh frying oil samples the polarization angle has value between 2.3× 10/V and3.3× 10-4 0/V in the experimental condition. The extra olive oil has the smallest value while palmoil has the greatest. According to the previous study, the olive oil is relatively the best oil.Keywords: frying oil, electrooptics, polarization angle
PEMBUATAN KURVA ISODOSIS PAPARAN RADIASI DI RUANG PEMERIKSAAN INSTALASI RADIOLOGI RSUD KABUPATEN KOLAKA - SULAWESI TENGGARA Syahria, Syahria; Setiawati, Evi; Firdausi, K Sofjan
BERKALA FISIKA Vol 15, No 4 (2012): Berkala Fisika
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t have been conducted research about the influence of distance variability betweensecondary radiation source and the determining spot to scatter  radiation exposure in theinspection room I radiology instalation RSUD Kolaka – South East Sulawes, it producted isodosecurve .This research use phantom, in the form of water in the plastic container high 40 cm andwidth 21 cm, with exposure wide 30×  40 cm. Exposure condition is given by fixed expose factor covering of tube voltage 90 kV, tube current 150 mA and exposure time 0.8 second.  Sample in this research is distance of 1 meter; 1,5 meter and 2 meter from the secondary radiation source to thedetermining spot, which measuring the scatter radiation exposure is directly conducted by thesurvey meter measuring instrument.The result of research indicates that the amount of thescattered radiation exposure will downhill progresivley to addition distance, so it can know thepoints/places that safe to the scatter radiation exposure. It can also know the maximum time limitallowed for a radiator worker in the inspection room I.Keywords : Isodose Curve ,  Phantom, Expose factor, Scatter radiation exposure.
REVIEW PENGUJIAN HUKUM MALUS DAN SIFAT OPTIS AKTIF LARUTAN GULA MENGGUNAKAN SISTEM DETEKSI CAHAYA Amitasari, Ria; Istiyawan, Wardono; Sugito, Heri; Bawono P, Ari; Firdausi, K Sofjan
BERKALA FISIKA Vol 16, No 1 (2013): Berkala Fisika
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Abstract In this paper, we review the test results of Malus’ Law and optical activity of sugarsolution using a system light detector. Two polarizers were used in the experiment to serve thechoice of a certain direction of electric field of light and to determine the change of polarizationangle. The change of transmitted intensity were measured using LDR detector which was thenacquisitioned by microcontroller and displayed via LCD and computer using  Microsoft Visual Studio C#. The experiment result is in agreement to the Malus’ Law with correlation coefficient of 0.99, and by using the equipment we obtain linearity between the change of polarization angle andconcentration of sugar solution, which is appropriate to the theory, as well. The specific rotarypower is (54±2) o/dm(g/mL) in the experimental uncertainty.Keywords: Malus law, change of polarization angle, light detector
EVALUASI KUALITAS BEBERAPA JENIS MINYAK GORENG KEMASAN SETELAH DIPANASKAN MENGGUNAKAN SIFAT ELEKTROOPTIS Murni, Sri; Bawono Putranto, Ari; Hidayanto, Eko; Firdausi, K Sofjan
BERKALA FISIKA Vol 16, No 3 (2013): Berkala Fisika
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In this report, we have determined the average value of polarization angle for various edible oils, before and after heating. The change of polarization angle was measured averagebetween potential differences 0-9 kV. The heating time for the samples was conducted up to 10 hours at average temperature by 180°C. The source of light was He-Ne Laser 1 mW (633 nm) with optical length of samples of 1 cm. In agreement to the previous experiment, our result shows that all vegetable oils provide increasing of free radicals indicated by increasing polarizationangle for longer heating time. For the heating time interval 0-10 hours, the level degradation ofoil rises quadratically. From various edible oils, olive oil is still the relative best quality from allsamples in this experiment. This method, once again, shows more powerful relative to otherstandard methods.Keywords: frying oil, electrooptics, polarization angle
PEMANFAATAN SIFAT OPTIS AKTIF ALAMI UNTUK KENDALI MUTU MINYAK GORENG MENGGUNAKAN LAMPU PIJAR Asy Syifa, A Y; Nisa, Fathia; Prasanti, Irvani D; Murni, Sri; Firdausi, K Sofjan
BERKALA FISIKA Vol 16, No 2 (2013): Berkala Fisika
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In this study the properties of natural optical activity of the various vegetable cookingoils was used as a new method for a quality control and was proposed as a new prospect forpreliminary test of oil quality. The samples used were various packaging cooking oil obtained inthe shops and were considered already fulfilled by SNI. The source of light to illuminate was a75W light-bulb. The change of the polarization angle of light was measured using polarizer basedon Malus’ law, and it was used to indicate the levels of oil quality degradation. The experimentalresult shows that highest change of polarization angle indicates relative lowest quality of oils. Anolive oil shows the best oils relative from other types of vegetable oils. The natural polarization inthis case is able to differentiate between various types of oil, and to distinguish fresh oil andexpired oil. It seems that natural polarization accommodates some contributed components oflevel of degradation of oil quality, i.e. free fatty acid and saturated fat. This method provides someadvantages, such as, simple equipments, a fast test, without preliminary treatment, and accurateresults. For the future, it shows a reliable test to conduct as a previous quality control for cookingoil and replaces the role of conventional, expensive standard methods. This method offers also achallenge to evaluate the level of authentication or halal of oils and fats.Keywords: oil quality, polarization angle, optical activity.
PEMBUATAN LAPISAN FOTOKATALIS ZINC OXIDE (ZnO) DENGAN TEKNIK SPRAY COATING DAN APLIKASINYA PADA PENGERING JAGUNG Hidayanto, Eko; Sutanto, Heri; Firdausi, K Sofjan; Arifin, Zaenal
BERKALA FISIKA Vol 16, No 4 (2013): Berkala Fisika
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ZnO thin film has been deposited on the glass with a spray coating technique. Gel of ZnO 0.5 M was synthesized by dissolving 0.5 M zinc acetate dehydrate in isopropanol andmonoethanolamine solution at room temperature with the molar ratio of MEA and ZnAc is 1:1. The solution was stirred using a magnetic stirrer at 70°C for 30 minutes to get the clear and homogeneous ZnO gel. ZnO gel is placed on the spray hole and sprayed on a heated glasssubstrate till 40oC. Then, the spraying layer spraying was allowed to stand for 3 days tostrengthen the contact with glass layer. Deposition results of ZnO layer is transparent withtransmittance values of 71.4 % and decreases with a decrease in wavelength imposed on the layer.The energy dispersive X-ray (EDX) results show the composition of zinc (Zn) is less than theoxygen (O) with a ratio Zn : O = 38.44 % : 61.56 %. The scanning electron microscopy (SEM)results show ZnO thin film has a smooth and homogeneous surface with a grain size of 57 nm. Thetest results demonstrate ZnO layer has a band gap value of 3.01 eV. The drying corn shows thatdirectly drying using sunlight has a faster rate compared using ZnO glass. Surface morphology ofthe layer of dried corn using ZnO glass has brighter color and lice compared to directly drying onsunlight.Keywords: Photocatalyst, ZnO, Thin Film, Spray Coating, Corn, Drying
PENENTUAN FREKUENSI RESONANSI PADA ARTIFISIAL METAMATERIAL MENGGUNAKAN BENTUK SPLIT RING RESONATOR (SRR) YBIC, Muh Yasin; Firdausi, K Sofjan; Priyono, Priyono
YOUNGSTER PHYSICS JOURNAL Vol 3, No 3 (2014): Youngster Physics Journal Juli 2014
Publisher : YOUNGSTER PHYSICS JOURNAL

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Metamaterial represent the material with negative value of permitivity ( ) and permeability ( ). Artificial metamaterial can be realized with periodic structure of wire for the negative relative permittivity ( ), and Split Ring Resonator (SRR) for the negative relative permeability ( ). This research represent the theoretical study about the dimension effect of SRR to active frequency of electromagnetic wave ( ) at artificial metamaterial. Plasmon resonances in SRR due to the interaction with the electromagnetic waves used to determine  in order to obtain the equation in the form of frequency. From these equations graphically simulated between  to the  at various dimension size of SRR, so can be knowable about the dimension effect of SRR to active frequency of metamaterial. At periodic structure of SRR, if the distance apart of SRR ( ) increase hence top boundary of active frequency (magnetic plasma frequency, ) decrease, and  bottom boundary of active frequency (SRR resonance frequency, ) do not change. If radius of SRR ( ) increase hence will decrease the  and . If  the gap ring of SRR ( ) increase hence increase of  and . Keywords: permitivity, permeability, metamaterial, Split Ring Resonator.