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INDONESIA
BERKALA FISIKA
Published by Universitas Diponegoro
ISSN : -     EISSN : -     DOI : -
Core Subject : Science,
Physics
BERKALA FISIKA adalah jurnal saintifik yang diterbitkan secara periodik 3 bulanan. Jurnal ini memuat kajian-kajian Fisika baik kajian teoretik maupun hasil eksperimen. Jurnal ini juga memberi ruang yang luas bagi kajian – kajian aplikasi fisika dalam bidang teknologi, ilmu-ilmu hayati dan kedokteran.
Arjuna Subject : -
Articles 5 Documents
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Search results for , issue "Vol 14, No 4 (2011): Berkala Fisika" : 5 Documents clear
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
Publisher : BERKALA FISIKA

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Abstract

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
APLIKASI PRAKTIS MODEL IDENTIFIKASI AUTOREGRESSIVE MOVING AVERAGE EXOGENOUS (ARMAX) DENGAN METODA KUADRAT TERKECIL REKURSIF Khuriati RS, Ainie
BERKALA FISIKA Vol 14, No 4 (2011): Berkala Fisika
Publisher : BERKALA FISIKA

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Abstract

AbstractEffect on variations in power heating to air temperature in the mosquito box were modelled. Transfer function for temperature ranges from 34.93 oC to 39.93 C determinedexperimentally. A step function used to excite power control and its effect on the air temperaturemeasured. From these information, the transfer function in the ARX and ARMAX form determinedand compared. An analysis of the computational results has confirmed that the ARMAX model andthe recursive least square method are superior to the ARX model and the Extended Least Square method to model the thermal behaviour in the mosquito box as indicated by the level of fitting and system stabilitytedKeywords: Identification, prediction error method, caged mosquitoes
STRUKTUR NANOKRISTAL CeO YANG DISINTESIS MENGGUNAKAN METODE PRESIPITASI DENGAN VARIASI LAMA WAKTU KALSINASI 2 Nursanti, Ida; Muhlisin, Zaenul; Sutanto, Heri; Nurhasanah, Iis
BERKALA FISIKA Vol 14, No 4 (2011): Berkala Fisika
Publisher : BERKALA FISIKA

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Abstract

Nanocrystalline CeO have been synthesized by using a precipitation method. in a mixedsolvent system of aqua DM and isopropanol. Precipited was calcined at temperature of 300 C forvarious calcination time.  X-ray difractometer was used to investigate resulting presipitedmicrostructure.  X-ray diffraction patterns were analyzed to study effect of calcination time tostructure and crystallite size. Refinement process of x-ray diffraction pattern was carried out byusing Rietveld method.  The results show that all of precipited were CeO  nanocrystalline withsingle phase of cubic fluorite.  The difference in lattice parameter was correlated to oxygenvacancy.  Crystallite size was found in the range 9 – 11 nm, its incresed as calcination timeincreased.   The increasing of calcination time did not significant influence to  crystallite size. These result indicated that CeO  nanocrystalline  exhibited weak-agglomeration.Keywords: CeO222, nanocrystalline, microstructure, x-ray diffraction, precipitation 2o
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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Abstract

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)
PEMODELAN ANOMALI GRAVITASI SESAR DENGAN PENDEKATAN MODEL SHEET (MODELLING GRAVITY ANOMALIES OF FAULT BY SHEET MODEL APPROACH) Nurwidyanto, M Irham; Setiawan, Ari
BERKALA FISIKA Vol 14, No 4 (2011): Berkala Fisika
Publisher : BERKALA FISIKA

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Abstract

AbstractThe modelling gravity anomaly of fault model with a model sheet approach with the aim to study the response of gravity anomalies of faults was done.Modelling is done by modelling approaches bedding with a thickness t and density contrastwith surrounding Δρ. The  gravity anomaly at a point are formulated and  the calculation andvisualization program created in matlab8RS. From the modelling is made it can be concluded that the fault position is generally locatedbetween the gravity anomaly minimum and maximum gravity anomaly. When thetypes of fault arevertical normal fault then the fault position precisely located on the horizontal gradient  maximumvalue, whereas when the fault are not vertical, the location of fault are  to be near (around) themaximum horizontal gradient.Key words: modelling, gravity anomalies, faults, model sheets.

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