• The Korean Journal of Financial Management
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• v.18 no.1
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• pp.83-106
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• 2001

본 연구에서는 1997년 말 외환위기 이후 $1998\sim1999$년에 걸쳐 행하여진 한국 은행산업 구조 조정의 성과를 실증적으로 분석하였다. 실증분석의 결과 위험수준이 높아 구조조정 기간에 금융감독당국으로부터 강한 경영개선 압력을 받을 가능성이 높은 은행들은 무수익여신, 부실여신비율 등 대출행위의 건전성 측면과 대출, 유가증권간의 투자비율, 그리고 유가증권 내 자산종목 간의 투자 비율 등 여러 가지 위험관련 변수들과 관련하여 측정된 건전화에 대한 동기면에서 외환위기 이전에 비하여 유의적이고 일관된 보다 높은 건전화에 대한 동기를 가지고 있었음을 볼 수 있었으며, 이러한 결과는 외환위기 이후의 은행권 구조조정 정책에 대한 어느 정도의 유효성을 보여 주는 결과로 사료된다. 또한 은행 집단별 분석에서는 구조조정 과정에서 퇴출 또는 우량은행에게 인수/합병된 부실은행들은 구조조정 이전의 기간에 그 외의 은행들 보다 위험추구에 대한 동기가 매우 강하였음을 볼 수 있었으나 이러한 위험추구의 동기가 우량은행에로의 인수/합병을 통하면서 상당히 감소하였음을 발견할 수 있었으며, 이러한 결과는 총표본에 대한 분석에서의 결과와 일관되게 외환위기 이후의 구조조정 정책에 대한 어느 정도의 유효성을 보여 주는 결과로 사료된다.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.7 s.172
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• pp.170-176
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• 2005

Analysis of structures which are composed of numerous repeated unit structures can be simplified by using homogenized properties. If the unit structure is repeated in one direction, the whole structure may be regarded as a beam. Once the effective stiffness is obtained from the analysis of the unit structure in a proper way, the effort for the detail modeling of the global structure is not required, and the real structure can be replaced simply with a beam. This study proposes a kinematical periodicity constraint to be imposed on the FE model of the unit structure, which improves the accuracy of the effective stiffness. The method is employed to a one dimensionally arrayed 3D structure containing periodically repeated un-symmetric holes. It is demonstrated that the deformation behavior of the homogenized beam agrees well with that of the real structure.

• Journal of the Korea Concrete Institute
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• v.14 no.6
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• pp.934-941
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• 2002

It is important to consider the effect of member size when estimating the ultimate strength of a concrete flexural member because the strength always decreases with an increase of member size. In this study, the size effect of a reinforced concrete (RC) beam was experimentally investigated. For this purpose, a series of beam specimens subjected to four-point loading were tested. More specifically, three different effective depth (d$\approx$15, 30, and 60 cm) reinforced concrete beams were tested to investigate the size effect. The shear-span to depth ratio (a/d=3) and thickness (20 cm) of the specimens were kept constant where the size effect in out-of-plane direction is not considered. The test results are curve fitted using least square method (LSM) to obtain parameters for the modified size effect law (MSEL). The analysis results show that the flexural compressive strength and the ultimate strain decrease as the specimen size increases. In the future study, since $\beta_1$ value suggested by design code and ultimate strain change with specimen size variation, a more detailed analysis should be performed. Finally, parameters for MSEL are also suggested.

• Magazine of the Korea Concrete Institute
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• v.8 no.6
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• pp.173-182
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• 1996

An experimental research was carried out to investigate the effect of thc compressive strength of concrete on the stirrup effectiveness in shear behavior of concrete beams. For this purpose. total 24 beams of section dimension of $300{\times}600mm$ were tested: 4 specimens without web reinforcement and 20 specimens with web reinforcement in the form of vertical stirrups. Main variables were two levels(norma1 and high strength) of the compressive strength of concrete and six types of t h e shear rcinfor.cement ratios. Prior to experiment, for given sections and assumed material constants, the reference shear reinforcement ratio(${\rho}_vACI$) which leads to the flexure failure using the provisions of the ACI Building Code(AC1 318-95) was calculated. and the shear reinforcement ratios were relatively selected from the value of ${\rho}_vACI$. From test results, it was shown that thc safety factor of ACI eyuation for p1,ediction of shear strength was decreased with increasing the compressive strength of concrete in beams without stirrups. However. it was observed that as the amount of' stirrup is increased, the safety factor for high strength conci,ete beams with high stirrup ratio is ensured more than that for normal strength concrete beams. Therefore i t appears that the stirrup effectiveness of high strength concrete beams is greater than that of normal strength concrete beams.

• The Optical Journal
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• s.124
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• pp.66-72
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• 2009

세상에는 사진만으로 구사할 수 있는 언어가 있다. 사진에서 차지하는 구도는 사진 제작에서 본질적인 것이며 매우 중요성을 갖는다. 구도의 본질은 구성이고 그 목적은 주제를 강조하고 시각적으로 가장 유효적절하게 나타내려는 것이다. 좋은 구도는 눈을 즐겁게 하면서 관심을 끄는 한편 시각적으로 잘 표현된 사진은 단순한 사물로서의 대상이 아니라 의사소통의 중요한 요소이다. 사진의 완성도를 결정짓는 구도까지 공부했으니 이제는 왕초보에서 '왕'자를 떼어내고 초보 사진가로서 세상의 보이는 모든 것들을 지휘해보자.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.18 no.2
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• pp.159-168
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• 2005

An improved stability design method for beam-columns of plane frames is proposed based on system buckling analysis and second-order elastic analysis. For this, the tangent stiffness matrix of beam-column elements is first derived using stability functions and a procedure for evaluating effective buckling lengths is reviewed using elastic system buckling analysis. And then the second-order analysis procedure is presented considering $P-\Delta$ effects and is compared with the closed-form solution through numerical examples. Design examples showing the validity of the proposed method we presented and their numerical results are compared with those obtained from the conventional stability design methods. Finally some useful conclusions are drawn.

• Journal of Korean Society of Steel Construction
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• v.16 no.3 s.70
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• pp.355-363
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• 2004

In order to obtain the effective length factor of beam-column members of plane frames, this paper extensively used an alignment chart approach, based on the nomograph given in LRFD-AISC specification commentaries. However, it should be noted that various simplifications and assumptions were introduced in constructing the alignment chart. To overcome the practical limitations of the alignment chart, this paper proposes a simple but accurate procedure that determined the effective buckling length for stability design of main members of cable-supported bridges. This method requires the full system buckling analysis. The numerical examples showing the suitability of the present scheme are discussed and some conclusions are drawn.

• The Transactions of the Korean Institute of Power Electronics
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• v.9 no.6
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• pp.568-576
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• 2004

This paper presents a new anti-islanding method for distributed power generation system (DPGS) using renewable energy. Based on the concept of real and reactive power mismatch, three different islanding conditions are analyzed. It is shown via analysis that islanding voltage is a function of real power alone, where as its frequency is a function of both real and reactive power. Using this analysis, a new anti-islanding method is developed. The proposed protection algorithm continuously perturbs ($\pm$5%) the reactive power supplied by DPGS while simultaneously monitoring the utility voltage and frequency. If a measurable frequency deviation took place by islanding, the real power of DPGS is further reduced to 80%. This detection method is shown to be fast acting under resonant loads. Possible islanding conditions are simulated and verified with analysis. Experimental results on a 0.5kW utility-interactive fuel cell system are suggested.

• Journal of Korean Society of Steel Construction
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• v.9 no.2 s.31
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• pp.277-285
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• 1997

To investigate the shear strength and hysteretic behavior of SRC column to H steel beam joints, seven cruciform specimens were fabricated and tested. The test specimens showed stable hysteresis behavior with a little pinching. The strength decreased with increase in deflection after the speciemens reached at the maximum strength. The shear strength of panel zones increased with increased in the concrete amount of SRC column sections. The shear strength may conservatively be estimated by the sum of shear yielding strength of steel column web, plastic bending strength of steel column flange and ultimate shear strength of concrete in the panel zone.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.668-668
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• 2013

CIGS 박막태양전지는 다른 박막태양전지에 비해 높은 에너지 변환효율을 보이고 있으며, 광범위한 기술 응용분야를 가지고 있다. CIGS를 광흡수층으로 하는 태양전지의 구조는 5개의 단위박막(배면전극, 광흡수층, 버퍼층, 앞면 투명전극, 반사방지막)을 순차적으로 형성시켜 만든다. 단위박막별로 다양한 종류의 재료와 조성, 또한 제조방법에서는 갖가지 물리적, 화학적 박막 제조방법이 사용된다. 현재 광흡수층인 CIGS층의 경우 동시증발법과 스퍼터링법이 높은 효율을 보이고 있다. 본 연구에서는 CIGS층을 3-stage process를 적용한 동시증발법을 사용하였고, Fluxmeter와 기판후면 온도 모니터링을 이용하여 제조하였으며, 버퍼층은 moving 스퍼터링 법으로 ZnS를 증착하였고, 투명전극층은 PLD (Pulsed Laser Deposition)를 이용하여 제조하였다. 가장 높은 광변환효율을 보인 Al/ZnO/CdS/Mo/SLG박막시료는 유효면적 0.45 $cm^2$에 광변환효율 15.71%, Jsc: 33.64 mA/$cm^2$, Voc: 0.64 V, FF: 73.18%를 얻을 수 있었으며, CdS를 ZnS로 대체한 Al/ZnO/ZnS/Mo/SLG 박막시료는 유효면적 0.45 $cm^2$에 광변환효율 12.13%, Jsc: 33.22 mA/$cm^2$, Voc: 0.60 V, FF: 62.85%를 얻을 수 있었다.