• 한국과학교육학회지
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• 제5권1호
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• pp.11-17
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• 1985

This study had its objective to indentify the basic biological concepts as recommended by scholars in biology and by high school biology teachers for inclussion in the high school biology curriculum and to determine the importance levels of the concepts. The scholars for this study were selected to insure that their majors are evenly distributed across the biological areas. The final concept list contains 137 biological concepts along with their importance level judged by the scholars and high school biology teachers. The biological concepts are categorized into 12 biological areas. This study suggests that the concepts in the final list can not refect the conceptual hierarchy or inclusiveness, goals or objectives of biology education in the high school, and difficulty levels of the concepts. This study also claims that the concept list like the one produced by this study should be successively' checked and revised due to the continuous development of biological knowledge system and the constant change in the meanings of the knowledge system.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 D
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• pp.2636-2638
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• 2000

In this paper, we show the simple methods of designing the Smith predictor for the long dead time processes. We are using the relay feedback to model the processes in the second-order plus dead time structure. The model is able to represent a various class of processes dynamics including low- or high-order, and monotonic or oscillatory process. A PID type controller is proposed for the main controller in the Smith controller, which insure the stability of overall system. Simulation Examples are also provided to illustrate the effectiveness and applicability of the proposed controller.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2000년도 춘계학술대회 논문집
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• pp.589-597
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• 2000

This paper deals with the basic design of the traction motor(TM) by performing the train performance simulation(TPS). The TPS, considering min condition, provides some important information about selecting the latins of TM such as current, power and frequency, etc. Especially, calculating the current flowing into the TM by the TPS in the situation of normal condition and M-car cut out respectively, we can inspect whether the TM endures thermally under the contingency or not. This paper reviews the tractive effort of the train to meet the demands of consumer and then designs the TM electrically. finally, performing the TPS under emergency condition, it checks the thermal capacity of the TM to insure the justice of the TM under construction.

• 천문학회지
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• 제28권2호
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• pp.223-243
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• 1995

We describe the implementation of a multi-dimensional numerical code to solve the equations for idea! magnetohydrodynamics (MHD) in cylindrical geometry. It is based on an explicit finite difference scheme on an Eulerian grid, called the Total Variation Diminishing (TVD) scheme, which is a second-order-accurate extension of the Roe-type upwind scheme. Multiple spatial dimensions are treated through a Strang-type operator splitting. Curvature and source terms are included in a way to insure the formal accuracy of the code to be second order. The constraint of a divergence-free magnetic field is enforced exactly by adding a correction, which involves solving a Poisson equation. The Fourier Analysis and Cyclic Reduction (FACR) method is employed to solve it. Results from a set of tests show that the code handles flows in cylindrical geometry successfully and resolves strong shocks within two to four computational cells. The advantages and limitations of the code are discussed.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 추계 학술발표회 제16권2호
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• pp.117-120
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• 2004

Up to now, many researches have been performed md verified that many properties of concrete can be improved by using mineral admixtures such as blast furnace slag, silica fume, and expansive admixture. But it is not clear whether there is any need for entraining air to make a high strength concrete using expansive admixture and mineral admixtures to insure enough freeze-thaw resistance. this paper presents the strength and durability properties of high strength concrete using expasive admixtures and industrial by-products. It was observed from the test results that very high strength concrete$(W/B=20\%)$ is not needed to be air entrained and high strength concrete$(W/B=30\%)$ using expansive admixture and mineral admixtures is needed to be entrained $2\~4\%$ air.

• 한국지능시스템학회:학술대회논문집
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• 한국퍼지및지능시스템학회 1993년도 Fifth International Fuzzy Systems Association World Congress 93
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• pp.822-825
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• 1993

A fuzzy logic controller derived from the variable structure control (VSC) theory is designed. Unlike the conventional design of the fuzzy controller, we do not fuzzify the error and the rate of error, but fuzzify the sliding surface. After the fuzzy sliding surface is introduced, the fuzzy rules are defined based on the sliding control theory. It will be shown this sliding mode fuzzy controller is a kind of VSC that introduces the boundary layer in the switching surface and that the control input is continuously approximated in the layer. As a result we can guarantee the stability and the robustness by the help of VSC, which were difficult to insure in the past fuzzy controllers. Simulation results for the inverted pendulum will show the validity.

• Journal of Mechanical Science and Technology
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• 제20권10호
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• pp.1607-1613
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• 2006

GIS (Gas Insulated Switchgear) is used in electric power system to insure non conductivity, breaking capacity and operating reliability. In the present study, dynamic analysis on the closing resistors of the GIS has bees carried out by the commercial dynamic analysis code COSMOS MOTION and 3-D modeling program SOLID WORKS. In order to find the minimum value of chatter vibration of closing resistors, the motion of moving and fixed resistor parts of closing resistors were simulated by varying the spring constant, the damping coefficient and the mass of moving and fixed resistor parts. The simulated results were compared with experimental results. The application of the results could reduce chatter vibration of closing resistors of the GIS. These data are also useful on the development of future model GIS with minimum chatter vibration for the determinations of the spring constant, the damping coefficient and mass of a moving part.

• 한국해안해양공학회지
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• 제2권1호
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• pp.43-50
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• 1990

본 연구는 허용응력 설계법에 의한 파랑하중을 받는 스틸자켓의 부재단면 최적화를 다루고 있다. 건설경비의 최적화에 대한 목적함수로서 스틸자켓의 중량을 택하였으며 제약조건은 구조물의 변위와 응력이 허용치 내에 있도록 하였다. 비선형 최적화문제는 수정된 Newton-Raphson법을 이용한 SUMT 방법을 사용하여 해석하였다.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1996년도 춘계학술대회
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• pp.108-110
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• 1996

Open MRI is a new concept in clinical application of the MRI such as interventional study. Receiving RF coils used in the open MRI must have open structures to insure convenient manipulations fur the patient. In this paper, we presented experimental study fur open head coil suitable to 0.3 Tesla vertical field MRI system with its experimental results.

• 한국농공학회지
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• 제36권3호
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• pp.144-154
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• 1994

An efficient tidal model, TIDE which is an iterative type, nonlinear finite element model has developed for the analysis of the tidal movement in the coastal area which is characterized by irregular boundaries and bottom topography. Traditional time domain finite element models have been in difficulties with requirement for high eddy viscosity coefficients and small time steps to insure numerical instability. These problems are overcome by operating in the frequency domain with an elaborate grid system by combining the triangular and quadrilateral shape grids. Furthermore, in order to handle non-linearity which will be more significant in the shallow region, an iterative scheme with least square error minimization algorithm has been implemented in the model. The results of TIDE model are agreed with the analytical solutions in a rectangular channel under the condition of tidal waves entering the channel closed at one end.