• 대한방사선기술학회지:방사선기술과학
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• 제24권2호
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• pp.5-11
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• 2001

Most of X-ray generator had used rectifier type transformer with high tension generator which is supplied in a clinical diagnosis. Because the ripple rate of tube voltage is high, X-ray generating efficiency is very low. In these days, high tension generator for inverter type X-ray generator is being supplied from a broad which uses semi-conductor switching element for the electric power that have a high speed switching ability to solve these problem. But, semi-conductor element with large capacity is used with X-ray tube's large consumption power and diffusion is difficult in the small size hospital because production cost is going up by doing digital control through DSP. Therefore, this paper designed and manufactured CR type voltage divider for feedback control of tube voltage with high frequency resonance type inverter and for high tension transformer with high frequency. It was to make economical diffusion type X-ray generator which has wide output voltage and load extent. It was preyed that the X-ray generator had the stability of X-ray tube's output characteristics.

• Nuclear Engineering and Technology
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• 제55권6호
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• pp.2230-2245
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• 2023

KANT (KAIST Advanced Nuclear Tachygraphy) is a PWR core simulator recently developed at Korea Advance Institute of Science and Technology, which solves three-dimensional steady-state and transient multigroup neutron diffusion equations under Cartesian geometries alongside the incorporation of thermal-hydraulics feedback effect for multi-physics calculation. It utilizes the standard Nodal Expansion Method (NEM) accelerated with various Coarse Mesh Finite Difference (CMFD) methods for neutronics calculation. For thermal-hydraulics (TH) calculation, a single-phase flow model and a one-dimensional cylindrical fuel rod heat conduction model are employed. The time-dependent neutronics and TH calculations are numerically solved through an implicit Euler scheme, where a detailed coupling strategy is presented in this paper alongside a description of nodal equivalence, macroscopic depletion, and pin power reconstruction. For validation of the steady, transient, and depletion calculation with pin power reconstruction capacity of KANT, solutions for various benchmark problems are presented. The IAEA 3-D PWR and 4-group KOEBERG problems were considered for the steady-state reactor benchmark problem. For transient calculations, LMW (Lagenbuch, Maurer and Werner) LWR and NEACRP 3-D PWR benchmarks were solved, where the latter problem includes thermal-hydraulics feedback. For macroscopic depletion with pin power reconstruction, a small PWR problem modified with KAIST benchmark model was solved. For validation of the multi-physics analysis capability of KANT concerning large-sized PWRs, the BEAVRS Cycle1 benchmark has been considered. It was found that KANT solutions are accurate and consistent compared to other published works.

• Nuclear Engineering and Technology
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• 제44권2호
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• pp.177-198
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• 2012

This paper reviews the fast reactor physics and computational methods. The basic reactor physics specific to fast spectrum reactors are briefly reviewed, focused on fissile material breeding and actinide burning. Design implications and reactivity feedback characteristics are compared between breeder and burner reactors. Some discussions are given to the distinct nuclear characteristics of fast reactors that make the assumptions employed in traditional LWR analysis methods not applicable. Reactor physics analysis codes used for the modeling of fast reactor designs in the U.S. are reviewed. This review covers cross-section generation capabilities, whole-core deterministic (diffusion and transport) and Monte Carlo calculation tools, depletion and fuel cycle analysis codes, perturbation theory codes for reactivity coefficient calculation and cross section sensitivity analysis, and uncertainty analysis codes.

• Nuclear Engineering and Technology
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• 제44권2호
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• pp.161-176
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• 2012

McCARD is a Monte Carlo (MC) neutron-photon transport simulation code. It has been developed exclusively for the neutronics design of nuclear reactors and fuel systems. It is capable of performing the whole-core neutronics calculations, the reactor fuel burnup analysis, the few group diffusion theory constant generation, sensitivity and uncertainty (S/U) analysis, and uncertainty propagation analysis. It has some special features such as the anterior convergence diagnostics, real variance estimation, neutronics analysis with temperature feedback, $B_1$ theory-augmented few group constants generation, kinetics parameter generation and MC S/U analysis based on the use of adjoint flux. This paper describes the theoretical basis of these features and validation calculations for both neutronics benchmark problems and commercial PWR reactors in operation.

• Journal of Information Technology Applications and Management
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• 제18권1호
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• pp.15-39
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• 2011

A deeper understanding of how organizations behave as social complex adaptive systems is needed. In this paper we demonstrate how the Leadership Invigorating Flows of Energies model can help with this understanding. The model highlights the role of emergent leadership as a force encouraging the creation, diffusion, and utilization of knowledge through self-organizing mechanisms. We illustrate our approach by examining Wikipedia and show how it can be described as a social CAS. Our analysis of Wikipedia describes how emerging intrapreneurship behaviors result in dynamic flows of knowledge and self-organizing feedback mechanisms across the organization. We provide implications for organization studies and present evidence to support claims made by advocates of complexity theory. We conclude by proposing that Wikipedia can be seen as a new form of organization, and finish with a brief note highlighting a possible way forward.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2017년도 전력전자학술대회
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• pp.435-436
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• 2017

This papaer is study on thermal analysis of the active-front-end(AFE) rectifier for solid-state-transformer(SST) applications. finite element analysis simulation model is combined by switching component model, power diode and heat-sink model. thermal model is calculated by computer program and feedback the result. using simulation result analysis switching loss and compare to thermal diffusion of the heat in the model for steady-state operation.

• East Asian Economic Review
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• 제23권1호
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• pp.3-26
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• 2019

This study investigates the effect of high-skilled inventor emigration rate on growth rate of the country of origin (COO). Inventor emigrants represent the human capital that can generate highly innovative work. The social network they form spurs knowledge diffusion and technology transfer back to their COOs, which in turn affects innovation and growth in their home countries. We run dynamic panel estimation for 154 countries during 1990-2011, and empirically show that a positive and statistically significant effect exists for the interaction of inventor emigration and trade. The result indicates that the direct negative impact of the brain drain can be mitigated by the positive feedback effect generated by the high-skilled inventor emigrants abroad. When coupled with an active trade policy that reinforces growth, countries can partially recoup the direct effect of the human capital loss. We stress the importance of international trade for successful technology transfer to occur, and offer insights for policies that can utilize the benefits of the rich social network of their high-skilled emigrants.

• 한국사회복지학
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• 제52권
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• pp.89-115
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• 2003

그동안 사회복지 임상실천 분야에서 주로 관심을 기울여 온 것은 개입방법의 개발과 효과성 측정 연구였다. 반면 이러한 연구 결과물이 어떻게 현장에 보급되고 활용되는지에 대한 관심은 상대적으로 부족한 편이었다. 이러한 현상은 결과적으로 연구와 실천간의 괴리를 초래할 수 있다는 비판이 제기되면서, 최근 외국에서는 사회복지 분야에서도 이론과 실천, 또는 학문과 현장을 잇는 중요한 기제로서 지식 및 기술의 보급과 활용에 대한 관심이 부각되고 있다. 이에 본 연구에서는 본 연구자가 프로그램 개발에 이어 현장보급 노력을 기울여 온 성장기술 프로그램을 중심으로 현장보급 과정과 활용현황을 살펴보고자 하였다. 이를 위하여 보급과 활용에 관한 기존 이론 및 모델들을 정리하고, 그 중 Herie와 Martin의 연구-실천 가교 모델에 의거하여 성장기술 프로그램의 현장 보급과정 및 활용 상황을 추적 조사하고 분석해 보았다. 그 결과 성장기술 프로그램 보급과정의 문제점으로는 구체적인 전략의 부재, 계획성 부족으로 인한 즉흥적인 대응, 초기 보급 대상자에 대한 허술한 파악 등을 도출할 수 있었다. 그리고 효과적인 보급과 활용을 위해서는 적절한 모델을 선택하고 그에 따라 보급과정을 적용하고 실천할 것, 프로그램 개발과정부터 보급에 대해 염두를 두고 진행할 것, 프로그램 개발 뿐 아니라 현장 피드백 확보를 위한 노력을 기울일 것, 그리고 사회복지 교육 및 연구에서 전파과정에 대한 부분을 강화할 것 등을 제언하였다. 이를 통해 몇 가지 한계점들에도 불구하고 보급 및 활용에 대한 중요성을 제시할 수 있었으며, 성장기술 프로그램의 현장 활용성도 파악할 수 있었다. 이와 같은 보급과 활용에 대한 논의들은 국내에서 진행되는 연구의 전파 뿐 아니라 그동안 외국으로부터 도입해온 개입방법들을 한국 상황에 맞게 토착화하기 위하여 앞으로 더욱 활성화될 필요가 있을 것이다.

• 환경정책연구
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• 제14권1호
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• pp.33-52
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• 2015

본 논문의 목적은 국가 로드맵 상에 제시된 7대 부문(산업, 수송, 건물, 공공, 농림어업, 폐기물, 전환)에 대한 부문별 감축 수단을 대상으로 향후 보다 발전적인 이행전략을 분석하는 것이다. AHP와 ANP 방법론을 활용해 방법론 간 차이점이 나타난 부문과 그렇지 않은 부문을 비교분석하였다. 감축대상인 7대 부문 대부분에서 이행목표로서 비용효율성과 효과성(기술개발, 감축성과)보다는 이행가능성이 상대적으로 중요한 것으로 분석되었다. 평가기준에서는 공공, 전환 부문에서 방법론에 따라 최우선순위가 바뀌었으며, 감축방안에 해당하는 대안의 우선순위 및 기준 관점의 대안 내 우선순위도 방법론에 따른 차이가 나타났다.

• 천문학회지
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• 제35권4호
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• pp.159-174
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• 2002

Cosmological hydrodynamic simulations of large scale structure in the universe have shown that accretion shocks and merger shocks form due to flow motions associated with the gravitational collapse of nonlinear structures. Estimated speed and curvature radius of these shocks could be as large as a few 1000 km/s and several Mpc, respectively. According to the diffusive shock acceleration theory, populations of cosmic-ray particles can be injected and accelerated to very high energy by astrophysical shocks in tenuous plasmas. In order to explore the cosmic ray acceleration at the cosmic shocks, we have performed nonlinear numerical simulations of cosmic ray (CR) modified shocks with the newly developed CRASH (Cosmic Ray Amr SHock) numerical code. We adopted the Bohm diffusion model for CRs, based on the hypothesis that strong Alfven waves are self-generated by streaming CRs. The shock formation simulation includes a plasma-physics-based 'injection' model that transfers a small proportion of the thermal proton flux through the shock into low energy CRs for acceleration there. We found that, for strong accretion shocks, CRs can absorb most of shock kinetic energy and the accretion shock speed is reduced up to $20\%$, compared to pure gas dynamic shocks. For merger shocks with small Mach numbers, however, the energy transfer to CRs is only about $10-20\%$ with an associated CR particle fraction of $10^{-3}$. Nonlinear feedback due to the CR pressure is insignificant in the latter shocks. Although detailed results depend on models for the particle diffusion and injection, these calculations show that cosmic shocks in large scale structure could provide acceleration sites of extragalactic cosmic rays of the highest energy.