• Structural Engineering and Mechanics
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• 제25권3호
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• pp.311-330
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• 2007

Model-based predictions of structural behavior are negatively affected by uncertainties of various type and in various stages of the structural analysis. The present paper focusses on dynamic analysis and addresses the effects of uncertainties concerning material and geometric parameters, mainly in the context of modal analysis of large-scale structures. Given the large number of uncertain parameters arising in this case, highly scalable simulation-based methods are adopted, which can deal with possibly thousands of uncertain parameters. In order to solve the reliability problem, i.e., the estimation of very small exceedance probabilities, an advanced simulation method called Line Sampling is used. In combination with an efficient algorithm for the estimation of the most important uncertain parameters, the method provides good estimates of the failure probability and enables one to quantify the error in the estimate. Another aspect here considered is the uncertainty quantification for closely-spaced eigenfrequencies. The solution here adopted represents each eigenfrequency as a weighted superposition of the full set of eigenfrequencies. In a case study performed with the FE model of a satellite it is shown that the effects of uncertain parameters can be very different in magnitude, depending on the considered response quantity. In particular, the uncertainty in the quantities of interest (eigenfrequencies) turns out to be mainly caused by very few of the uncertain parameters, which results in sharp estimates of the failure probabilities at low computational cost.

• 시스템엔지니어링학술지
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• 제9권1호
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• pp.55-63
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• 2013

Nuclear power plant site selection is a complex process and its successful completion is a critical milestone in the NPP development cycle. Proper siting of NPP will ensure public health and safety, environmental conservation, reduced project failure risks and a smooth NPP development process among other benefits. The objective of this paper is to demonstrate the application of systems engineering to the problem of NPP siting in Kenya. The siting process demonstrated in this paper includes stakeholder need analysis where stakeholders are identified and their needs concerning NPP site are elicited and converted into system functional requirements. A value model is then developed and potential sites iteratively subjected to three types of criteria i.e. exclusionary criteria, avoidance criteria and suitability criteria. This process is used to identify the candidate sites. An additive value model; multiple objectives Decision Analysis (MODA) is then used to calculate candidate solutions values. The site with the highest solution value score is selected. Sensitivity studies using different criterion weight sets (thereby reflecting different viewpoints) can be conducted to assess their effect on the selection of a preferred site and thereby lend additional credibility to the decision process.

• 터널과지하공간
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• 제9권3호
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• pp.230-237
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• 1999

석회석은 시멘트의 원료로 년간 약 8천만 톤 이상이 주로 강원도와 충북지역에서 채굴되고 있다. 그러나 노천채굴에 따른 환경오염원의 유발과 환경보전의 논리로 개발에 많은 제한을 받고 있다. 최근에는 개발기술이 향상되고 있으며, 개발조건 역시 변화되고 있기 때문에 이에 맞추어 석회석 개발과 관련된 제도 역시 부분적으로 수정, 보완되어야 할 것이다. 따라서 본 연구에서는 환경오염저감을 위한 몇가지 대책과 관련 제도의 부분적인 개정 방안을 제시하였다. 이와 같은 과정을 거처 환경보전과 개발의 조화속에 시멘트 산업의 획기적 발전이 있길 기대한다.

• 한국태양에너지학회 논문집
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• 제23권1호
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• pp.29-38
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• 2003

To develope chemical heat pump using available energy sources, solar heat and other kinds of waste thermal energy, we have studied the material and heat transfer rate in the cylindrical bed reactor packed with Calcined Dolomite. Our results from the studies are as follows ; 1 The time needed to complete dehydration reaction at the wall side of the cylindrical reactor(r/rL=0.5) was shorter than that of the center(r/rL=0.0) as much as 12%. 2. Two dimensional (radial and circumferential) partial differential equations, concerning heat and mass transfer rate in the packed bed of calcined Dolomite, are solved numerically to describe the characteristics of the reaction in the cylindrical reactor. The solution reads rate of reaction in the packed bed reactor depends on the temperature and concentration of reactants. These results read the supplied heat transfers from the wall side of the cylinder to the center, dehydration reaction begins at the inner side of the wall of the cylindrical reactor and the dehydration reaction proceeds from the wall side to center of cylinder.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년도 제30회 춘계학술대회논문집
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• pp.285-288
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• 2008

본 연구는 연료(수소)층과 산화제(공기)층의 사이에 불활성기체(질소)또는 연료(수소)를 평행분사하는 수치해석을 다루고 있다. 수치해석을 위해서 완전 보존되는 비정상 2차 시간정확도법과 2차 TVD방법이 유한 체적법과 사용되었다. 결과는 3가지 종류로 구성되어있다. 첫째는 연료와 산화제의 단일 혼합층이고, 둘째는 연료와 산화제의 사이에 불활성기체를 분사하는 방식이며, 세 번째는 연료와 산화제의 사이에 연료를 분사하는 방식이다. 전체 유동층의 수직두께는 4cm이며 삽입된 중간층의 두께는 1,2,4mm의 세가지 경우에 대하여 계산하였다.

• International Journal of Advanced Culture Technology
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• 제8권3호
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• pp.192-197
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• 2020

Foreign students in South Korea face important challenges when they try to maintain their health. As a measure of their motivation to actively build skills for overcoming those challenges, we evaluated the 10-item Consumer Health Activation Index (CHAI), testing its feasibility, dimensionality, and reliability. There were no missing data, there was no floor effect, and for the total scores the ceiling effect was trivial (< 2%). Results of the Kaiser-Meyer-Olkin test and Bartlett's test of sphericity indicated that the data were suitable for the detection of structure by factor analysis. The results of parallel analysis and the shape of the scree plot supported a two-factor solution. One factor had 3 items concerning "my doctor" and the other factor had the 7 remaining items. Reliability was high for the 10-item CHAI (alpha = 0.856), for the 3-item subscale (alpha = 0.838), and for the 7-item subscale (alpha = 0.857). Reliability could not be improved by deletion of any items. Use of the CHAI to gather data from these foreign students is feasible, and reliable results can be obtained whether one uses the total score from all 10 items or scores from the proposed 7-item and 3-item subscales.

• Bulletin of the Korean Chemical Society
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• 제29권1호
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• pp.94-98
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• 2008

A fundamental study was developed concerning the novel solvent extraction of the tetravalent metal ions; zirconium(IV), hafnium(IV) and thorium(IV). Their extraction behavior in toluene was investigated with a recently synthesized naphthol-derivative Schiff base, 1-({[4-(4-{[(E)-1-(2-hydroxy-1-naphthyl)methyliden]amino}phenoxy) phenyl]imino}methyl)-2-naphthol (HAPMN). The spectrophotometrical examination of the complex formation between HAPMN and the Zr(IV), Hf(IV) and Th(IV) ions in acetonitrile revealed the formation of stable 1:1 complexes in the solution. After the thorium extraction in toluene, it was found that [Th(OH)3HA] was the respective deriving substance. While, in the case of zirconium and hafnium extraction, the extracted adduct was found to be [M4(OH)8(H2O)16Cl62HA]. The stoichiometric coefficients of these extracted species were determined by the slope analysis method. The extraction reaction followed a cation exchange mechanism.

• 한국농촌건축학회논문집
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• 제17권1호
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• pp.55-64
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• 2015

The purpose of this study is to find out the application plan for the landscape planning after grasping the current situation of the historical and cultural resources in Cheongju city and closely examining their conservation and use state. Concerning the method of the study, I considered the resources related concepts and came up with the characteristics of the historical and cultural resources and the application planning as landscape factors after the research on the actual condition and their present situation. Regarding the study or research, I studied the cultural assets, historical and cultural resources, historical and cultural planning, and further examined the historical and cultural resources by dividing them diversely and further, studied the current situation of their system and the related law. For the current situation of the historical and cultural landscape resource in Cheongju city I conducted the assessment of the landscape resources by areas, types, locations. On the basis of this study I came up with the basic direction for the application plan and the solution to the management of the landscape and think that these plans or suggestions will make a contribution to the establishment of their identity by regions.

• Journal of Electrical Engineering and Technology
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• 제1권1호
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• pp.28-34
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• 2006

Recently, in accordance with the development of IT technology, it is prevalent for power quality monitors to be connected to each other via networks and share their data because such networks provide system-wide insights to customers concerning power quality. Those systems can alarm and display power quality events for the convenience of customers. However, if a power quality event occurs, it is difficult for customers to determine its cause and solution because the systems do not provide appropriate power quality diagnosis functions. The power quality management system presented in this paper has been developed to provide customers with various power quality diagnosis functions so that they can cope well with power quality problems with the right measure in the right place. This paper presents the structure and functions of the developed power quality management system and shows some results of the power diagnosis functions.

• 한국정밀공학회지
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• 제24권7호
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• pp.112-119
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• 2007

Cavities of Class V are caused by heavy occlusal loads due to bruxism and clenching habit. It is general to restore abfraction lesions with dental filler materials to reduce stress concentration. A material should be selected from various dental products based on long term clinical experiences or personal preference concerning filler methods. A quantitative criterion is necessary to make an evaluation of the results as dentists decide treatment methods and dental materials relying on their clinical experiences. The purpose of this study is to find an optimal restoration method and material for noncarious cervical lesions using the finite element method. An objective function was defined to minimize the sum of tensile and compressive stresses. Several models with different combinations of resins were suggested and compared in terms of the values of objective function. An optimal solution was to fill TetricFlow inside the lesion and Z100 in the remaining region with a thickness ratio of 0.125.