• Title/Summary/Keyword: Full Peak Efficiency

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A High-efficiency Method to Suppress Transformer Core Imbalance in Digitally Controlled Phase-shifted Full-bridge Converter

  • Yu, Juzheng;Qian, Qinsong;Sun, Weifeng;Zhang, Taizhi;Lu, Shengli
    • Journal of Power Electronics
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    • v.16 no.3
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    • pp.823-831
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    • 2016
  • A high-efficiency method is proposed to suppress magnetic core imbalance in phase-shifted full-bridge (PSFB) converters. Compared with conventional solutions, such as controlling peak current mode (PCM) or adding DC blocking capacitance, the proposed method has several advantages, such as lower power loss and smaller size, because the additional current sensor or blocking capacitor is removed. A time domain model of the secondary side is built to analyze the relationship between transformer core imbalance and cathode voltage of secondary side rectifiers. An approximate control algorithm is designed to achieve asymmetric phase control, which reduces the effects of imbalance. A 60 V/15 A prototype is built to verify the proposed method. Experimental results show that the numerical difference of primary side peak currents between two adjacent cycles is suppressed from 2 A to approximately 0 A. Meanwhile, compared with the PCM solution, the efficiency of the PSFB converter is slightly improved from 93% to 93.2%.

Corrections of Self-Absorption Effect Using the Monte Carlo Method in the Radioactivity Analysis of Environmental Samples (환경시료의 방사능 분석에서 Monte Carlo 방법을 이용한 자체흡수 효과 보정)

  • Seo, Bum-Kyoung;Lee, Dae-Won;Lee, Kil-Yong;Yoon, Yoon-Yeol;Yang, Tae-Keun
    • Journal of Radiation Protection and Research
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    • v.26 no.2
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    • pp.51-58
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    • 2001
  • In the low level radioactivity measurement, such as environmental radioactivity, there were used commonly cylindrical and Marinelli type beakers by means of measurement container. If there are differences in the matrix density or sample height between standard source and sample, it must be determined full energy peak efficiency considering self absorption effect. In this paper, we compared measured efficiency with calculated full energy peak efficiencies in the HPGe detector using the Monte Carlo method. For cylindrical container, we calculated the variation of the efficiency with sample height. Also, we calculated the variation of the detection efficiency with apparent density in the cylindrical and Marinelli container. It was seen that it need to be corrected for self absorption in the energy range of below 1000keV. Also, in order to verify the validity of calculation, we compared the calculated value with reference value using NIST SRM 4353 reference soil.

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A Development of GUI Full-Energy Absorption Peak Analysis Program for Educational Purpose (전 에너지 흡수 피크 분석용 GUI 기반 교육용 프로그램 개발)

  • Sohn, Jong-Wan;Shin, Myung-Suk;Lee, Hye-Jung;Jung, Kyung-Su;Jeong, Min-Su;Kim, Sang-Nyeon
    • Journal of Radiation Protection and Research
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    • v.34 no.2
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    • pp.69-75
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    • 2009
  • To obtain precise information about characteristics of gamma ray detector system responses, we developed new GUI computer program to analize full-energy absorption peak using our developed Delphi computer code for educational purpose. By use of the well known 4 nonlinear peak shaping functions, peaks were fitted with least square fit method in this code. In this paper, we described the methods to search for 12 coefficients in above 4 nonlinear peak shaping functions by use of our developed code in details. The computer code was tested for 1 $\mu$Ci $^{137)Cs$ 661 keV gamma ray peak spectrum detected by 25 % relative efficiency HPGe detector with 5.35 cm (D) $\times$ 5.5 cm (L) size.

Improving the Overall Efficiency for DC/DC Converter with LoV-HiC System

  • Han, Dong-Hwa;Lee, Young-Jin;Kwon, Wan-Sung;Bou-Rabee, Mohammed A.;Choe, Gyu-Ha
    • Journal of Power Electronics
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    • v.12 no.3
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    • pp.418-428
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    • 2012
  • It is very important to improve the overall efficiency of systems with a source of power that has low-voltage high-current terminal characteristics such as fuel cells. A resonant converter is required for high efficiency systems. However, the peak value of the switches current is large in a resonant converter. This peak current requires a large number of switches and results in system failures. In this paper, an analysis and experiments of a resonant isolation push-pull converter are performed. A switching loss analysis is performed in order to compare losses between a resonant push pull converter and a hard switching push-pull converter. Specially, the conduction loss is studied based on the ratio between the resonant frequency and the switching frequency. In addition, a method for improving the efficiency is implemented with conventional HF insolation converters.

Out-of-plane behavior of perforated masonry walls strengthened with steel-bar truss system

  • Hwang, Seung-Hyeon;Mun, Ju-Hyun;Yang, Keun-Hyeok;Kim, Sanghee
    • Structural Engineering and Mechanics
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    • v.83 no.6
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    • pp.799-810
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    • 2022
  • This study investigated the effect of the strengthening efficiency of unbonded steel-bar truss system on the out-of-plane behavior of perforated masonry walls. Four full-scale unreinforced masonry (URM) walls with two different planes were prepared using the unbonded steel-bar truss system and a URM walls without strengthening. All masonry walls were tested under constant axial and cyclic lateral loads. The obtained test results indicated that the pinching effect in the out-plane behavior of masonry walls tends to decrease in the in- and out-of-plane strengthened URM walls using the unbonded steel-bar truss system with the higher prestressing force ratio (Rp) of vertical reinforcing bars in the unbonded steel-bar truss system, regardless of the perforated type of the masonry wall. Consequently, the highest maximum shear resistance and cumulative dissipated energy at peak load in the post-peak behavior were observed in the in- and out-plane strengthened URM walls with the highest Rp values, which are 2.7 and 6.0 times higher than those of URM. In particular, the strengthening efficiency of the unbonded steel-bar truss system was primarily attributed to the vertical prestressed steel-bars rather than the diagonal steel-bars, which indicates that the strains in the vertical prestressed steel-bars at the peak load were approximately 1.6 times higher than those in the diagonal steel-bars.

Experimental and Simulated Efficiency of a HPGe Detector in the Energy Range of $0.06{\sim}11$ MeV

  • Park Chang Su;Sun Gwang Min;Choi H.D.
    • Nuclear Engineering and Technology
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    • v.35 no.3
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    • pp.234-242
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    • 2003
  • The full energy peak efficiency of a hyper pure germanium (HPGe) detector was calibrated in a wide energy range from 0.06 to 11 MeV. Both the experimental technique and the Monte Carlo method were used for the efficiency calibration. The measurement was performed using the standard radioisotopes in the low energy region of $60{\sim}1408$ keV, which was further extended up to 11 MeV by using the $^{14}N(n,r)\;and\;^{35}Cl(n,r)$ reactions. The GEANT Monte Carlo code was used for efficiency calculation. The calculated efficiency had the same dependency on the r-ray energy with the measurement, and the discrepancy between the calculation and the measurement was minimized by fine-tuning of the detector geometry. From the calculated result, the efficiency curve of the HPGe detector was reliably determined particularly in the high energy region above several MeV, where the number of measured efficiency points is relatively small despite the wide energy region. The calculated efficiency agreed with the measurement within about $7\%$. In addition to the efficiency calculation, the origin of the local minimum near 600 keV on the efficiency curve was analyzed as a general characteristics of a HPGe detector.

New mathematical approach to calculate the geometrical efficiency using different radioactive sources with gamma-ray cylindrical shape detectors

  • Thabet, Abouzeid A.;Hamzawy, A.;Badawi, Mohamed S.
    • Nuclear Engineering and Technology
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    • v.52 no.6
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    • pp.1271-1276
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    • 2020
  • The geometrical efficiency of a source-to-detector configuration is considered to be necessary in the calculation of the full energy peak efficiency, especially for NaI(Tl) and HPGe gamma-ray spectroscopy detectors. The geometrical efficiency depends on the solid angle subtended by the radioactive sources and the detector surfaces. The present work is basically concerned to establish a new mathematical approach for calculating the solid angle and geometrical efficiency, based on conversion of the geometrical solid angle of a non-axial radioactive point source with respect to a circular surface of the detector to a new equivalent geometry. The equivalent geometry consists of an axial radioactive point source with respect to an arbitrary elliptical surface that lies between the radioactive point source and the circular surface of the detector. This expression was extended to include coaxial radioactive circular disk source. The results were compared with a number of published data to explain how significant this work is in the efficiency calibration procedure for the γ-ray detection systems, especially in case of using isotropic radiating γ-ray sources in the form of point and disk shapes.

Dependence Evaluation of the Self-Absorption Correction Factor for p-type High Purity Germanium Detector Characteristics (p-type HPGe 검출기 특성에 따른 밀도 보정인자 의존도 평가)

  • Jang, Mee;Ji, Young-Yong;Kim, Chang-Jong;Lee, Wanno;Kang, Mun Ja
    • Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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    • v.13 no.4
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    • pp.295-300
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    • 2015
  • The precise determination of the activity for each radionuclide in environmental samples requires the self-absorption correction factor. In this research, we derived the self-absorption correction factor for three p-type high purity germanium detectors using the Monte Carlo code MCNPX. These detectors have different characteristics such as crystal diameter, height and size of the core. We compared the calculated full-energy peak efficiency with the experimental value using a standard sample with $1g/m^3$ density and verified the modeling. We simulated the dependency of the full-energy peak efficiency on the 0.3, 0.6, 0.9, 1.0, 1.2 and $1.5g/m^3$ samples and obtained the corresponding self-absorption correction factor. The self-absorption correction factors calculated for the three detectors differ by less than 1% over most of the energy range and sample densities considered. This indicates that the self-absorption correction factors are independent of the crystal characteristics of HPGe detector.

Efficiency calibration and coincidence summing correction for a NaI(Tl) spherical detector

  • Noureddine, Salam F.;Abbas, Mahmoud I.;Badawi, Mohamed S.
    • Nuclear Engineering and Technology
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    • v.53 no.10
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    • pp.3421-3430
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    • 2021
  • Spherical NaI(Tl) detectors are used in gamma-ray spectrometry, where the gamma emissions come from the nuclei with energies in the range from a few keV up to 10 MeV. A spherical detector is aimed to give a good response to photons, which depends on their direction of travel concerning the detector center. Some distortions in the response of a gamma-ray detector with a different geometry can occur because of the non-uniform position of the source from the detector surface. The present work describes the calibration of a NaI(Tl) spherical detector using both an experimental technique and a numerical simulation method (NSM). The NSM is based on an efficiency transfer method (ETM, calculating the effective solid angle, the total efficiency, and the full-energy peak efficiency). Besides, there is a high probability for a source-to-detector distance less than 15 cm to have pulse coincidence summing (CS), which may occur when two successive photons of different energies from the same source are detected within a very short response time. Therefore, γ-γ ray CS factors are calculated numerically for a 152Eu radioactive cylindrical source. The CS factors obtained are applied to correct the measured efficiency values for the radioactive volumetric source at different energies. The results show a good agreement between the NSM and the experimental values (after correction with the CS factors).

Dead Layer Thickness and Geometry Optimization of HPGe Detector Based on Monte Carlo Simulation

  • Suah Yu;Na Hye Kwon;Young Jae Jang;Byungchae Lee;Jihyun Yu;Dong-Wook Kim;Gyu-Seok Cho;Kum-Bae Kim;Geun Beom Kim;Cheol Ha Baek;Sang Hyoun Choi
    • Progress in Medical Physics
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    • v.33 no.4
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    • pp.129-135
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    • 2022
  • Purpose: A full-energy-peak (FEP) efficiency correction is required through a Monte Carlo simulation for accurate radioactivity measurement, considering the geometrical characteristics of the detector and the sample. However, a relative deviation (RD) occurs between the measurement and calculation efficiencies when modeling using the data provided by the manufacturers due to the randomly generated dead layer. This study aims to optimize the structure of the detector by determining the dead layer thickness based on Monte Carlo simulation. Methods: The high-purity germanium (HPGe) detector used in this study was a coaxial p-type GC2518 model, and a certified reference material (CRM) was used to measure the FEP efficiency. Using the MC N-Particle Transport Code (MCNP) code, the FEP efficiency was calculated by increasing the thickness of the outer and inner dead layer in proportion to the thickness of the electrode. Results: As the thickness of the outer and inner dead layer increased by 0.1 mm and 0.1 ㎛, the efficiency difference decreased by 2.43% on average up to 1.0 mm and 1.0 ㎛ and increased by 1.86% thereafter. Therefore, the structure of the detector was optimized by determining 1.0 mm and 1.0 ㎛ as thickness of the dead layer. Conclusions: The effect of the dead layer on the FEP efficiency was evaluated, and an excellent agreement between the measured and calculated efficiencies was confirmed with RDs of less than 4%. It suggests that the optimized HPGe detector can be used to measure the accurate radioactivity using in dismantling and disposing medical linear accelerators.