Phosphatase Activity in Cheonho Reservoir

Kwag, No-Tae,Son, Jae-Hak,Lee, Jeong-Sub,Ahn, Tae-Young The Microbiological Society of Korea 1995 The journal of microbiology Vol.33 No.4

Phosphatase activity was measured with other environmental factors in Cheonho reservoir in 1994. It ranged form 95 to 1,685 nM/1/h and was correlated significantly with chlorophyll-a. Such a close relation well matched the fact that over 90% of phosphatase activity was detected in > 3 $\mu\textrm{m}$ fraction. The phosphatase activity also correlated negatively with dissolved inorganic phosphate concentration, which implies derepression of phosphatase production by phosphate limitation. Significant correlation was analyzed between phosphatase activity and BOD, which also appeared to be closely correlated with chlorophyll-a. A great percentage of organic materials seems to be generated autochthonously by algae and extracellular enzyme even though allochthonous influence was thought to be stronger in Cheonho reservoir.

Co-Ni alloy nanowires prepared by anodic aluminum oxide template via electrochemical deposition.

Kwag, Yong-Gyu,Ha, Jong-Keun,Kim, Hye-Sung,Cho, Hyoung-Jin,Cho, Kwon-Koo American Scientific Publishers 2014 Journal of Nanoscience and Nanotechnology Vol.14 No.12

<P>The alloy nanowires are more prospective magnetic and shape memory materials. Fabrication of binary or more alloy nanowires using electrochemical deposition process is generally challenging due to the different synthesis conditions of individual elements. In the present work, binary NiCo alloy nanowire arrays have been fabricated by electrochemical deposition using anodic aluminum oxide template medium technique. The optimum conditions (temperature, voltage and time) for synthesis of NiCo alloy nanowire array were achieved based on the ideal experimental conditions of single Ni and Co nanowire arrays. The synthesized NiCo alloy nanowire arrays were characterized by X-ray diffraction, field emission scanning electron microscopy and energy dispersive X-ray spectrometer. The amorphous NiCo alloy nanowires were crystallized by annealing of 800 degrees C for 1 hour in argon atmosphere. The controlled composition of electrolyte provided to achieve a uniformly distributed chemical composition of Ni and Co (49.26:50.74) in nanowires.</P>

The Effect of Managerial Overconfidence on the Values of Equity and Firm: A Simulated Valuation Approach

Kwag, Seung Woog 한국상업교육학회 2020 상업교육연구 Vol.34 No.5

1) 기업은 줄곧 경영진 자기과신의 희생양이 되어 왔다. 미국을 비롯한 대부분의 국가 에서 경영진 자기과신은 기업의사결정의 핵심 요인으로서 각종 투자정보를 분석하고 평가하는 과정에 깊이 관여하며 기업가치 증대 활동을 위축시키는 원인으로 주목받았 다. 특히 인수대상기업의 가치를 평가하는 고난도 과업을 담당하는 경영진들 사이에 서 두드러진다. 본 논문은 경영진 자기과신이 기업가치에 미치는 영향을 가치평가모 형과 민감도 시뮬레이션을 활용하여 고찰한다. 가치평가모형으로는 배당할인모형과 자유현금흐름모형이 사용된다. 시뮬레이션분석 결과는 기업가치가 경영진 자기과신의 변화에 매우 민감하게 반응함을 여실히 보여준다. 배당성장모형을 적용했을 때 자기 과신은 자기자본의 가치를 정상가치보다 평균 약 4.5배 과대평가하는 오류를 유발했 다. 자유현금흐름모형의 경우에는 기업가치가 자기과신으로 인해 정상가치보다 평균 약 9.9배가 치솟았다. 경영진 자기과신이 기업경영에 긍정적으로 작용한다는 연구도 종종 보고되고 있지만 자기과신으로 인한 주식가치나 기업가치의 과대평가를 과소평 가해서는 안 된다. 주식시장의 검증을 거치며 과도한 가치평가의 오류가 수정되면 기 업가치는 큰 폭으로 감소하게 되고 그 피해는 고스란히 주주들의 몫이 되기 때문이 다. 따라서 경영진 자기과신은 기업이나 개인의 투자의사결정 시 적절히 할인되어야 하고 재무관리와 회계 교육 시 가치평가의 필수요인으로 다루어져야 한다. The corporate world has suffered a crisis of managerial overconfidence. In the United States and around the world, managerial overconfidence has been a key input of corporate decisions for decades. Managerial overconfidence affects how managers interpret the information they receive from various media and on- or off-line sources. Managerial overconfidence is particularly pronounced among managers of acquiring companies who face the difficult task of evaluating the takeover targets. The purpose of this article is to investigate the impact of managerial overconfidence on firm value through a valuation framework. To this end, we employ two conventional valuation models – the dividend discount model (DDM) and the free cash flow model (FCFM) - to reveal the valuation effect of managerial overconfidence. Simulated sensitivity analyses show that the propensity of firm value to managerial overconfidence changes rapidly when the degree of managerial overconfidence strengthens. The simulation results show that when the DDM is applied the overconfident value of equity is, on average, 4.5 times the non-overconfident value of equity. When the FCFM is simulated, the ratio of the overconfident value of firm to the non-overconfident value of firm becomes 9.9 times, a big jump from 4.51 times for the DDM case. Regardless of the evidence of its useful contributions, managerial overconfidence appears to be a value-destroying behavioral bias that needs to be properly and cautiously addressed in corporate and individual investments and in educational settings of finance and accounting.

Bayesian-based seismic margin assessment approach: Application to research reactor

Kwag, Shinyoung,Oh, Jinho,Lee, Jong-Min,Ryu, Jeong-Soo Techno-Press 2017 Earthquakes and structures Vol.12 No.6

A seismic margin assessment evaluates how much margin exists for the system under beyond design basis earthquake events. Specifically, the seismic margin for the entire system is evaluated by utilizing a systems analysis based on the sub-system and component seismic fragility data. Each seismic fragility curve is obtained by using empirical, experimental, and/or numerical simulation data. The systems analysis is generally performed by employing a fault tree analysis. However, the current practice has clear limitations in that it cannot deal with the uncertainties of basic components and accommodate the newly observed data. Therefore, in this paper, we present a Bayesian-based seismic margin assessment that is conducted using seismic fragility data and fault tree analysis including Bayesian inference. This proposed approach is first applied to the pooltype nuclear research reactor system for the quantitative evaluation of the seismic margin. The results show that the applied approach can allow updating by considering the newly available data/information at any level of the fault tree, and can identify critical scenarios modified due to new information. Also, given the seismic hazard information, this approach is further extended to the real-time risk evaluation. Thus, the proposed approach can finally be expected to solve the fundamental restrictions of the current method.

Lift/Drag Prediction of 3-Dimensional WIG Moving Above Free Surface

Kwag, Seung-Hyun The Korean Society of Mechanical Engineers 2001 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.15 No.3

The aerodynamic effects of a 3-dimensional Wing in Ground Effect (WIG) which moves above the free surface has been numerically investigated via finite difference techniques. The air flow field around a WIG is analyzed by a Marker & Cell (MAC) based method, and the interactions between WIG and the free surface are studied by the pressure distributions on the free surface. Waves are generated by the surface pressure distribution, and a Navier-Stokes solver has been employed, to include the nonlinearities in the free surface conditions. The pressure values Cp and lift/drag ratio are reviewed by changing the height/chord ratio. In the present computations a NACA0012 airfoil with a span/chord ratio of 3.0 are treated. Through computational results, it is confirmed that the free surface can be treated as a rigid wavy wall.

Imaging Mode Design and Performance Characteristics of the X-band Small SAR Satellite System

Kwag, Young-Kil The Korean Society of Remote Sensing 2000 大韓遠隔探査學會誌 Vol.16 No.2

A synthetic aperture radar (SAR) system is able to provide all-weather, day-and- night superior imaging capability of the earth surface, and thus is extremely useful in surveillance for both civil and military applications. In this paper, the X-band high resolution spaceborne SAR system design is demonstrated with the key design performance for a given mission and system requirements characterized by the small satellite system. The SAR multi-mode imaging technique is presented with a critical parameter assessment, and the standard mode results are analyzed in terms of the image quality performances. In line with the system requirement X-band SAR payload and ground reception/processing subsystems are designed and the major design results are presented with the key performance characteristics. This small satellite SAR system shows the wide range of imaging capability with high resolution, and proves to be an effective surveillance systems in the light weight, high performance and cost-effective points of view.

A STUDY OF 2-D IMAGE RECONSTRUCTION using PARALLEL BEAM PROJECTIONS IN IBM PC

Kwag, Jung Geun 대구보건대학 1996 대구보건대학 論文集 Vol.16 No.-

영상재구성기법은 잘 알려진 영상처리기법으로서 주로 X-ray단층촬영기, NMR 그리고 CT 등에 쓰인다. 영상재구성의 목적은 프로젝션들로부터 목적물의 절단면의 영상을 얻는 것이다. 본 연구에서는 2차원 영상재구성기법에 관한 기본개념 및 수식을 설명하였다. 또한, 평형 주사방식에서 2차원 영상재구성인 Inverse Radon Transform, Filtered Back-Projection 혹은 Convolution Back-Projection에 대하여 설명하고 Filtered Back-Projection 알고리즘과 Convolution Back-Projection 알고리즘으로 IBM-PC 586팬티엄에서 컴퓨터시뮤레이션하고 검토하였다. 이상으로 종래의 고가의 컴퓨터에서 실행하던 것을 IBM-PC 586팬티엄에서 실행하므로서 NMR 및 CT의 가격저렴화를 기할 수 있다고 본다.

A Study on the Influence of Choice Properties of Food Carving Decoration Lecture on Recommended Intention and Revisiting Intention

Kwag, Myung Sug,Kim, Jin Soo Kyung Hee University Management Research Institute 2020 Asia pacific journal of business review Vol.5 No.1

This paper examines the effect of the choice properties of food carving decoration lectures on the recommendation and revisiting intention. As the culinary industry grows, consumers seek not only the value of satiety through food but also the value of aesthetics. They perceived satisfaction from the taste and appearance of the food as well as the interior of the restaurant and the service. Food carving is an important means of fulfilling consumer satisfaction value which is ever-changing. This study attempts to analyze the relationship between the choice properties of food carving lectures and the course recommendation and revisiting intention. This study hypothesis was formulated and the survey was conducted on 125 respondents who had experienced food carving lectures. The reliability and validity of measurement items were verified through Cronbach's Alpha and factor analysis. As a result, all measurement items showed no abnormality. The results of the analyses are as follows. The education satisfaction, education commitment, and brand image, the choice properties of food carving decoration lecture, were found to have a positive effect on the recommendation intention. The results also showed that the education commitment and brand image of food carving decoration lectures were positively associated with revisiting intention. Lastly, the implications of these findings were suggested and for future research were discussed.

Application of Bayesian statistics to seismic probabilistic safety assessment for research reactor

Kwag, Shinyoung,Oh, Jinho,Lee, Jong-Min Elsevier 2018 Nuclear engineering and design Vol.328 No.-

<P><B>Abstract</B></P> <P>Nuclear facilities are susceptible to the damage due to earthquake hazards. The recent strong earthquake events show the need to explore scenarios in which the expected seismic hazard exceeds a design basis earthquake. In this regard, the seismic probabilistic safety assessment (SPSA) methodology has been developed and utilized to access the overall risk to a nuclear power plant. However, it remains challenging to deal with various uncertainties, accurately to describe correlated events, to accommodate newly observed data and to consider severe accident scenarios within the current framework. In order to overcome such challenges and take advantage of the merits of recent systems analysis concepts, this paper explores a SPSA approach by integrating the current SPSA framework with a Bayesian network and Bayesian inference instead of utilizing the standard fault tree-based technique. The proposed approach enables one to account for what are known as Aleatory and Epistemic uncertainties, to consider the correlated events, to incorporate the additional data and to conduct vulnerability assessments in an accident condition. The proposed Bayesian-based method is demonstrated by its application to a research reactor as an example. Several case studies are conducted to demonstrate how additional information such as correlated events and newly observed data changes the system-level fragility and risk. In addition, a critical scenario is investigated in a situation in which an accident has occurred for a vulnerability assessment beyond a design-basis event. Consequently, it is shown that the proposed approach provides an enhanced framework for risk assessments at nuclear facilities under earthquake hazards. This framework is ultimately expected to be extended to effective plans to mitigate system-level risk and to enhance decision support for risk-informed designs.</P> <P><B>Highlights</B></P> <P> <UL> <LI> This study explores a Bayesian-based approach for seismic PSA of research reactor. </LI> <LI> Incorporation of a Bayesian network enables considering correlated events. </LI> <LI> It is also capable of conducting beyond-design-vulnerability assessments. </LI> <LI> Bayesian inference makes it feasible to evaluate real-time risk. </LI> </UL> </P>

A REVEIW OF ELECTRON BEAM TESTING

Kwag, Young Jik 수원대학교 산업기술연구소 1988 산업기술연구소논문집 Vol.3 No.-

작은 chip속에 복잡한 회로가 집적되어 놀라운 기능을 가진 고도집적 IC가 개발되어 computer는 물론 많은 전자기기에 사용하게 되어 전자혁명을 가능하게 하고 있다. 고도 집적회로(LSI)를 개발하는 데는 많은 인력과 개발비를 필요로 하게 되는데 개발과정에서의 개발경비를 줄이고 생산과정에서의 수율을 높이기 위해서는 집적회로내의 불량점을 정확하게 찾아낼 수 있는 정확한 측정기기를 필요로 한다. 주사형 전자현미경(SEM)을 이용하여 집적회로내의 불량점을 찾으려는 종래의 노력은 주사형 전자현미경의 beam의 직경이 측정하고자 하는 집적회로내의 line의 넓이보다 커서 그 목적을 달성할 수 없다. 집적회로내의 불량점을 찾아내기 위해서는 beam의 직경이 측정하고자 하는 점의 line 넓이의 1/5을 넘지 말아야 하므로 beam의 직경은 0.1um-02um을 넘지 말아야 하며, 측정하고자 하는 집적회로가 파괴되지 않고 정확한 결과를 얻기 위해서는 가속전압 1 kv 이하에서 beam의 전류가 InA이어야 한다. 이러한 목적을 달성하기 위해서 주사형 전자현미경을 개조하여 개발된 것이 Electron Beam Testing (EBT)이다. 1975년경 부터 개발되어 사용하게 된 EBT의 방법과 그 응용에 대하여 그간에 발표된 논문들을 중심으로 정리했다.