• Journal of Mechanical Science and Technology
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• 제17권5호
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• pp.718-725
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• 2003

The present study addresses the distortion of the compression wave reflected from an open end of a shock tube. An experiment is carried out using the simple shock tube with an open end Computational work is also performed to represent the experimented flows. The second-order Total Variation Diminishing scheme is employed to numerically solve the unsteady, axisy-mmetric, inviscid, compressible governing equations. Both the experimented and predicted results are in good agreement. The generation and development mechanisms of the compression wave, which Is reflected from the open end of the shock tube, are obtained in detail from the present computations. The effect of size of the baffle plate at the open-end that causes the reflection of the incident expansion wave is found negligible. A good correlation is obtained for transition of the reflected compression wave to a shock wave inside the tube. The present data show that for a given wave length of the incident expansion wave the transition of the reflected compression wave to a shock wave can be predicted with good accuracy.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 추계학술대회 논문집 학회본부 D
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• pp.700-702
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• 2000

The new design methodology of a hybrid fuzzy controller by means of the genetic algorithms is presented. In fuzzy controller which has been widely applied and used. in order to construct the best fuzzy rules that include adjustment of fuzzy sets, a highly skilled techniques using trial and error are required. To deal with such a problem, first, a hybrid fuzzy controller(HFC) related to the optimal estimation of control parameters is proposed. The HFC combined a PID controller with a fuzzy controller concurrently produces the better output performance than any other controller from each control output in steady state and transient state. Second, a auto-tuning algorithms is presented to automatically improve the performance of hybrid fuzzy controller, utilizing the simplified reasoning method and genetic algorithms. In addition, to obtain scaling factors and PID Parameters of HFC using GA, three kinds of estimation modes such as basic, contraction, and expansion mode are effectively utilized. The HFCs are applied to the first-order second-order process with time-delay and DC motor Computer simulations are conducted at step input and the performances of systems are evaluated and also discussed from performance indices.

• Steel and Composite Structures
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• 제10권3호
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• pp.207-222
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• 2010

Fire incident in buildings is common, so the fire safety design of the framed structure is imperative, especially for the unprotected or partly protected bare steel frames. However, software for structural fire analysis is not widely available. As a result, the performance-based structural fire design is urged on the basis of using user-friendly and conventional nonlinear computer analysis programs so that engineers do not need to acquire new structural analysis software for structural fire analysis and design. The tool is desired to have the capacity of simulating the different fire scenarios and associated detrimental effects efficiently, which includes second-order P-D and P-d effects and material yielding. Also the nonlinear behaviour of large-scale structure becomes complicated when under fire, and thus its simulation relies on an efficient and effective numerical analysis to cope with intricate nonlinear effects due to fire. To this end, the present fire study utilizes a second-order elastic/plastic analysis software NIDA to predict structural behaviour of bare steel framed structures at elevated temperatures. This fire study considers thermal expansion and material degradation due to heating. Degradation of material strength with increasing temperature is included by a set of temperature-stress-strain curves according to BS5950 Part 8 mainly, which implicitly allows for creep deformation. This finite element stiffness formulation of beam-column elements is derived from the fifth-order PEP element which facilitates the computer modeling by one member per element. The Newton-Raphson method is used in the nonlinear solution procedure in order to trace the nonlinear equilibrium path at specified elevated temperatures. Several numerical and experimental verifications of framed structures are presented and compared against solutions in literature. The proposed method permits engineers to adopt the performance-based structural fire analysis and design using typical second-order nonlinear structural analysis software.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2000년도 추계학술대회논문집
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• pp.7-14
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• 2000

The purpose of this study is to improvement strategies for transportation systems of container cargo in Busan port. Therefore, it was forecasted the future container cargo demand using logistic curve formula. In 2011, container cargo demand was forecasted 8.791 million TEU(T/S including 12.559 million TEU). In order to improvement transportation systems of container cargo, this study presented following; $\circled1$ port facilities expansion, $\circled2$ diversity of container transport modes. $\circled3$ make up ICD and exclusive container roads, $\circled4$ the second Seoul-Busan Expressway.

• 한국항만학회지
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• 제15권1호
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• pp.19-26
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• 2001

The purpose of this study is to improve the strategies for transportation systems of container cargoes in Busan port. Therefore, container cargoes forecasting is done through logistic methods based on past trends. In 2011, container cargoes demand was forecasted 8.791 million TEU(T/S including 12.559 million TEU). In order to improve transportation systems of container cargoes, the conclusions of this study can be summarized as follows ; \circled1 port facilities expansion, \circled2 diversity of container transport modes, \circled3 make up ICD and exclusive container roads, \circled4 the second Seoul-Busan Expressway.

• 유통과학연구
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• 제11권12호
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• pp.25-37
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• 2013

Purpose - The structure of retailing has changed as retailers develop markets in response to business environment changes. This study aims to analyze the general situation of retailers in order to predict future global strategy using case studies of overseas expansion strategy and the Metro Group's global strategy. Research design, data, and methodology - The backgrounds to the new retail business model and retailer classification are analyzed as theoretical data. In addition, the key success point of the Metro Group's "cash and carry" strategy is analyzed as is the Metro Group's global CFAR (collaborative planning, forecasting, and replenishment) strategy. Finally, the plan for cooperation and precise forecasting under the Metro Group's supply chain management are analyzed from the promotion environment viewpoint. Related materials analyzed included the 2012 annual report, the Metro Group's web page, and a video interview with the executive in charge of global strategy and the new market development department. Some data were revised to avoid disrupting essential aspects of the case studies. Results - The important finding was that the Metro Group could be a world-class retail company with its successful global expansion strategy. The Metro Group's global strategy's primary goal is to have a leading business position in Eastern and Western Europe. The "cash and carry" strategy is highest priority in its overseas expansion strategy. Moreover, the Metro Group has standardized product planning capacity, which could be applied in various countries with different structural and cultural backgrounds. This is the main reason that the Metro Group could rapidly become successful in the Eastern Europe and Asian markets through its structural overseas expansion strategies. In addition, the Metro Group emphasizes the importance of supply chain management. Conclusions - First, retailers should create additional value through utilizing the domestic market, market power, and economies of scale to launch a global strategy to maximize benefits from diversification. Second, the political, economic, and cultural background of the target country needs to be understood to successfully implement the overseas expansion strategy. Third, the main factor of successful cooperation with a local partner is how quickly the company gains total understanding of the business resources and core competence of its partner. All organizations should focus on the achievement of goals in order to successfully operate the partnership. Fourth, retailers should improve their business, financial and organizational structure. Moreover, the work processes and company culture should also be improved to respond strongly in the competitive global market. Fifth, the essential point of a successful retail business is the control capacity of its branding and format. The retailer could avoid forecasting errors through supply chain management by perfectly distributing the actual amount of its inventory. In addition, the risks along the supply chain are effectively shared between the supply chain partners. Finally, the central tendency of the market is to gain in strength with this taking place across all parts of the business.

• 대한전자공학회논문지
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• 제26권1호
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• pp.122-128
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• 1989

본 논문에서는 회로해석 중에서 DC및 과도(transient)해석에 필요한 비선형 대수 방정식을 풀기 위한 새로운 방법으로서 Quadratic Newton Raphson Method(QNRM)을 제안한다. QNRM은 Newtok-Raphson method(NRM)에 기본을 두고 있지만, 비선형 대수 방정식의 Taylor 급수 전개에서 2차 미분항을 포함한다. 각 반복 과정에서 미지수에 관한 2차식이 되는데 해를 예측함으로서 선형화 할 수 있다. QNRM의 수렴속도를 올리기 위해서는 이 해의 정확한 예측이 매우 중요하명 그 한 방법을 제시하였다. QNRM을 DC및 과도해석에 적용한 결과 NRM을 사용한 것보다 계산시간 및 반복횟우에 있어서 25% 이상 감소됨을 보여주었다.

• Structural Engineering and Mechanics
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• 제28권2호
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• pp.129-152
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• 2008

This paper considers the solution of the stochastic differential equations (SDEs) with random operator and/or random excitation using the spectral SFEM. The random system parameters (involved in the operator) and the random excitations are modeled as second order stochastic processes defined only by their means and covariance functions. All random fields dealt with in this paper are continuous and do not have known explicit forms dependent on the spatial dimension. This fact makes the usage of the finite element (FE) analysis be difficult. Relying on the spectral properties of the covariance function, the Karhunen-Loeve expansion is used to represent these processes to overcome this difficulty. Then, a spectral approximation for the stochastic response (solution) of the SDE is obtained based on the implementation of the concept of generalized inverse defined by the Neumann expansion. This leads to an explicit expression for the solution process as a multivariate polynomial functional of a set of uncorrelated random variables that enables us to compute the statistical moments of the solution vector. To check the validity of this method, two applications are introduced which are, randomly loaded simply supported reinforced concrete beam and reinforced concrete cantilever beam with random bending rigidity. Finally, a more general application, randomly loaded simply supported reinforced concrete beam with random bending rigidity, is presented to illustrate the method.

• 대한전자공학회논문지
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• 제19권3호
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• pp.1-4
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• 1982

본 논문은 제한 대역 랜덤 입력 신호를 가진 선형 시스템의 해석을 위한 효과적이고 통계적으로 정확한 기법을 발견, 비교 연구하는 데 그 목적이 있다. 전 논문에서 보인 truncated expansion 정확도를 이용한 새로운 각환 기법이 만들어졌고, 평균 자병 에러 기준에 의거하여 기법들의 성능 비교 연구가 일차, 이차 선형 시스템 모델들에 대해 수행 되었다. 그 결과, 새로운 제고 대역 state 변환 기법이 다른 기법들(일차 state 변환 기법 또는 Z-변환 기법)보다 더욱 효과적이고 통계적인 의미에서 정확함이 판명되가다.

• Asia pacific journal of information systems
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• 제13권4호
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• pp.1-27
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• 2003

With a swift development of information technology, web sites get more important roles as user's living places. This quantitative and qualitative expansion of web sites requires the need for an evaluation framework of web sites from comprehensive perspectives. This study proposes two dimensions for web site categorization and three dimensions for web site evaluation. These dimensions were developed based on the architectural perspectives that have been used to evaluate buildings in the real world for more than a thousand years. First, in order to categorize various web sites, we extracted two dimensions, user's goals and user's behaviors from behavioral architect which approaches user's behaviors in designing buildings. Second, in order to evaluate four web sites groups, we suggested three dimensions, which are firmness, commodity, delight used in evaluating buildings in the real world. Then for each of the four different web sites groups an empirical survey was conducted to verify these three dimensions of architectural metrics. This ends with study implications and limitations.