• Journal of the Optical Society of Korea
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• 제19권3호
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• pp.272-276
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• 2015

The PbS quantum dot is an emerging photovoltaic material, which may provide high efficiency breakthroughs. The most crucial element for the high efficiency solar cells's development is to understand charge transport characteristics of PbS quantum dot solids, which are also important in planning strategic research. We have investigated charge transport characteristics of PbS quantum dot solids thin films using space charge limited conduction analysis and assessed thickness dependent photovoltaic performances. The extracted carrier drift mobility was $low-10^{-2}cm^2/Vs$ with the estimated diffusion length about 50 nm. These and recently reported values were compared with those from a commercial photovoltaic material, and we present an essential element in further development of PbS quantum dot solids materials.

• Nuclear Engineering and Technology
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• 제29권4호
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• pp.320-326
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• 1997

The nuclide transport in the one-dimensional porous medium is considered as a first step in developing a decay chain transport in multidimensional inhomogeneous media. A method of solving conventional advection-dispersion equation with decay chain of arbitrary length by using the method of characteristics (MOC) is introduced. In specific cases where the advection are dominant rather than dispersion, the method is known to be useful : one of the most distinctive advantages in applying the model is that the MU minimizes the numerical dispersion, which is distinguished in such common numerical schemes as finite element method and finite difference method. The suggested model is considered to be effective through several illustrations for the case that decay chain of arbitrary length is involved during transport which is difficult to solve by standard numerical solutions if the medium becomes more complicated.

• 방사선산업학회지
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• 제8권1호
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• pp.59-63
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• 2014

Proton Induced X-ray Emission (PIXE) is a MeV ion beam analysis method for use with particle accelerators. PIXE uses low-energy charged particles as an excitation mechanism to generate characteristic x-ray emission from each element in a target. In PIXE analysis, the beam current used is from a few nA to several tens of nA. Chosun University (Cyclotron Research Center) designed a $50{\mu}A$ beam line from the 13 MeV cyclotron for use with a PIXE analysis system, as well as performing beam transport line optimization research. In this study, the beam line operation conditions for the optimization process of beam transport and beam characteristics are shown.

• 한국압력기기공학회 논문집
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• 제19권2호
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• pp.69-74
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• 2023

The paper presents the results investigating the effect of aircraft engine impact location on the intended function evaluation results of spent nuclear fuel transport cask. As a result of the investigation, it is found that the structural integrity is maintained as the maximum accumulated equivalent plastic strain is below the acceptable criterion regardless of the collision location. It is identified that when the aircraft engine collided with the upper part of the transport cask without considering impact limiter the containment performance is weakened compared to when the aircraft engine collided with the central part.

• International Journal of Automotive Technology
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• 제7권1호
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• pp.101-107
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• 2006

The force and moment simulation of a steady-state rolling tire taking the effect of tread pattern into account is described using a steady-state transport method with ABAQUS. Tread meshes can not fully consider a tread pattern because detailed tread meshes are not allowed in the steady-state transport method. Therefore, the tread elements are modeled to have orthotropic property instead of isotropic property. The force and moment simulation has been carried out for the cases of both isotropic and orthotropic properties of tread elements. Both cases of simulation results are then compared with the experimental results. It is verified that the orthotropic case is in a better agreement with the experimental result than the isotropic case. Angle effects of tread pattern have been studied by changing the orientation angle of orthotropic property of tread. It is shown that the groove angle in the tread shoulder region has a more effect on force and moment of a tire than that in the tread center region.

• Nuclear Engineering and Technology
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• 제53권12호
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• pp.3861-3878
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• 2021

The steady-state simplified spherical harmonics equations (SP_N equations) are a higher order approximation to the neutron transport equations than the neutron diffusion equation that also have reasonable computational demands. This work extends these results for the analysis of transients by comparing of two formulations of time-dependent SP_N equations considering different treatments for the time derivatives of the field moments. The first is the full system of equations and the second is a diffusive approximation of these equations that neglects the time derivatives of the odd moments. The spatial discretization of these methodologies is made by using a high order finite element method. For the time discretization, a semi-implicit Euler method is used. Numerical results show that the diffusive formulation for the time-dependent simplified spherical harmonics equations does not present a relevant loss of accuracy while being more computationally efficient than the full system.

• 한국화재소방학회논문지
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• 제26권3호
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• pp.79-84
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• 2012

본 연구에서는 국내외 스프링클러헤드 감도시험 기준에 적용하고 있는 반응시간지수(RTI, Response Time Index)를 사용하여 대류항과 전도항 그리고 시간 변화량을 고려한 감열부의 열전달 현상을 해석적으로 분석하였다. 원형 실린더 형상을 갖는 감열부의 열적 특성을 분석하기 위해서 비제차 2차 편미분 형태의 에너지 방정식을 사용하여 감열부 표면의 온도가 일정하고 대칭(Symmetric)인 경계조건을 적용하여 시간 증가에 대한 감열부의 반지름 방향 온도분포를 구하였다. 그 결과 본 연구의 감열부 열적 특성에 관한 분석 기법은 스프링클러헤드의 감도시험 및 감열부의 설계를 위한 자료의 활용이 가능할 것으로 판단된다.

• 한국방재학회:학술대회논문집
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• 한국방재학회 2009년도 정기 학술발표대회
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• pp.145.2-145.2
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• 2009

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1998년도 춘계학술대회 논문집
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• pp.258-262
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• 1998

A structural design based of finite element analysis has been performed to investigate the reliable automatic transport system. For the procedure, different cross-sectional geometric factors were calculated and compared in detail. The von-Mises stresses were chosen to maintain a solid loading braring capacity for the safe design. Parametric studies showed that it is more inportant for the plate bending problem than the vertical loads of hanging bar to assess the safe and economic structural design.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.184.2-184.2
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• 2014

Recent advances in the synthesis and characterization of nanoscale objects provided us with the atomistic understanding of charge transport through single molecular junctions. The representative examples are the mechanically controlled break junction technique and STM or conducting AFM junction techniques. Theoretical studies have been reported on the dependence of electronic charge transport on the geometry of molecule-electrode contacts, the critical element toward the realization of molecular electronics. In this report, we will clarify the puzzling discrepancies between theoretical predictions and experiments.