• Nuclear Engineering and Technology
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• 제49권1호
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• pp.277-284
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• 2017

This paper presents the establishment and characterization of a neutron calibration field using a bare $^{252}Cf$ source of low neutron source strength in Vietnam. The characterization of the field in terms of neutron flux spectra and neutron ambient dose equivalent rates were performed by Monte Carlo simulations using the MCNP5 code. The anisotropy effect of the source was also investigated. The neutron ambient dose equivalent rates at three reference distances of 75, 125, and 150 cm from the source were calculated and compared with the measurements using the Aloka TPS-451C neutron survey meters. The discrepancy between the calculated and measured values is found to be about 10%. To separate the scattered and the direct components from the total neutron flux spectra, an in-house shadow cone of 10% borated polyethylene was used. The shielding efficiency of the shadow cone was estimated using the MCNP5 code. The results confirmed that the shielding efficiency of the shadow cone is acceptable.

• 전자공학회논문지A
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• 제32A권3호
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• pp.110-117
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• 1995

New formulas for the minimum noise figure and the optimum source impedance of microwave FETs are derived using the noise equivalent circuits obtained from the steady-state Nyquist theorem for multi-terminal semiconductor devices. The derived formulas manifest the relationships between the noise sources and the physical parameters of a noise equivalent circuit. Furthermore the formulas can explain the effect of gate leakage current on the minimum noise figure and the optimum source impedance. comparisons with the published experimental data confirm the validity and usability of our formula.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2011년도 추계학술대회 논문집
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• pp.643-648
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• 2011

This paper deals with the ESM(equivalent source method) with the continuation of acoustic near-field for NAH(near-field acoustic holography) to overcome the finite measurement aperture effect and reconstruct the normal velocity on an arbitrarily shaped structure surface. The continuation method is an extension of the measured sound field into a region outside and is based on the Green's function relating acoustic quantities on the two conformal surfaces. This algorithm is not limited to planar surfaces and can be applied to arbitrarily shaped surfaces. The ESM is an alternative approach of BEM-based NAH for the reconstruction on a general structure. In ESM the acoustic field is represented by a set of point sources located over a surface that is close to the structure surface. The simulation results of this study shows that the reconstruction error of particle velocity on the source surface is 11% and 16% for planar and cylindrical sources separately.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1999년도 춘계학술대회 논문집
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• pp.175-180
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• 1999

Generally, When we measure of object 3D surfaces with phase shifting shadow moire method, it is use of optical system consist of light source, grating, and ccd camera. At this time, it is important parameter that vertical distance of grating and camera, grating and light source, and horizontal distance of camera and light source. When use camera consist of complex lens vertical distance of grating and camera is unknown parameter. From this cause equivalent wave length of moire fringe is uncertain. In this study, We exactly obtain a vertical distance of grating and camera so improve on measurement accuracy.

• ETRI Journal
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• 제44권5호
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• pp.759-768
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• 2022

A novel energy harvesting technique that uses conducted electromagnetic interference as an energy source is presented. Conducted EMI generated from fluorescent light using a switched-mode power supply was measured and modeled as an equivalent voltage source. Two types of rectifier circuits-a bridge rectifier and a voltage doubler-were used as the harvesting devices for conducted EMI source. The matching networks were designed based on the equivalent model, and the harvested power was improved. The implemented energy harvester produces a regulated power over 68.9 mW and current over 15.1 mA while a regulated voltage can be selected between 3.3 V and 5 V. The proposed system shows the highest harvesting power indoor environment and can provide enough power for the Internet of Things devices.

• Nuclear Engineering and Technology
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• 제20권2호
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• pp.132-136
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• 1988

지하수 오염물질의 이동모형 개발에 있어서 중요한 문제의 하나가 각각의 폐기물 저장용기 나 드럼을 독립된 선원으로 볼 것이냐 아니면 상응하는 합쳐진 선원으로 볼 것이냐 하는 문제이다. 본 논문에서는 포화된 다공성 매질에서의 분산된 선원에 대한 연구를 소개한다. 지하수의 유동이 있는 다공성 매질에서 평면상에 분산된 점 형태의 선원들을 가정하여 얻어 진 지하수내의 오염물질의 농도분포를 상응하는 크기를 가진 무한한 평면선원이나 하나의 점 선원을 농도분포들과 비교하였다. 본 연구의 결과로 다음의 세 영역을 찾아낼 수 있었다. 즉, (1) 선원에 가까운 관계로 인근 선원의 영향이 커서 각각의 선원들을 따로 고려한 모형을 사용하여야 하는 영역, (2) 선원에서 몇 미터 떨어진 지점으로부터 수백 내지 수천미터 떨어진 지점까지의 각각의 선원 대신 상응하는 유한한 평면 선원만이 정착한 결과를 얻게 하는 영역, (3) 선원으로부터 충분히 멀리 떨어져 있어서 상응하는 유한한 평면 선원만이 정확한 결과를 얻게 하는 영역이다

• Journal of Astronomy and Space Sciences
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• 제30권2호
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• pp.107-112
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• 2013

Tissue equivalent proportional counter (TEPC) can measure the Linear Energy Transfer (LET) spectrum and calculate the equivalent dose for the complicated radiation field in space. In this paper, we developed and characterized a TEPC for radiation monitoring in International Space Station (ISS). The prototype TEPC which can simulate a 2 ${\mu}m$ of the site diameter for micro-dosimetry has been tested with a standard alpha source ($^{241}Am$, 5.5 MeV). Also, the calibration of the TEPC was performed by the $^{252}Cf$ neutron standard source in Korea Research Institute of Standards and Science (KRISS). The determined calibration factor was $k_f=3.59{\times}10^{-7}$ mSv/R.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 추계학술대회논문집
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• pp.1101-1106
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• 2004

This study presents the reconstruction of sound field radiated from an automotive engine using equivalent sources. Basic concept of the method presented is to replace the engine noise source with elementary sources of multipoles, e.g., monopoles and dipoles. The so-called Helmholtz equation least-squares (HELS) method can reconstruct the sound radiation fields from spherical geometries in a series expansion of spherical Hankel functions and spherical harmonics. In this paper, multi-Point, multipole equivalent sources are employed to reconstruct the sound field radiated from an automotive engine with a fixed rotation speed. To ensure and improve the accuracy of reconstruction, the spatial filters of multipole coefficients and wave-vectors are adopted for suppressing the adverse effect of high-order multipoles. Optimal filter shapes are designed with regularization parameters minimizing the generalized cross validation (GCV) function between actual and reproduced model. After regeneration of field pressures using the proposed method as many as necessary, the vibro-acoustic field of an engine could be reconstructed by using the BEM-based near-field acoustic holography (NAH) technique in a cost-effective manner.

• Nuclear Engineering and Technology
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• 제52권6호
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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.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2000년도 전력전자학술대회 논문집
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• pp.392-395
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• 2000

This paper proposes a soft-switching current -source inverter with a sitched-capacitor module The system operation was analyzed by a theoretical approach with equivalent circuits and verified by a computer simulation with ISPICE software. The proposed system could be effectively applied for the power converter of photovoltaic power generation interconnected with the power system.