• Journal of Electrical Engineering and Technology
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• 제10권3호
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• pp.990-1001
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• 2015

This paper presents analysis of Switched Reluctance Machine (SRM) using Geometry Based Analytical Model (GBAM), Finite Element Analysis (FEA) and Fourier Series Model (FSM) with curve fitting technique. Further a Transient Analysis (TA) technique is proposed to corroborate the analysis. The main aim of this paper is to give in depth procedure in developing a Geometry Based Analytical Model of Switched Reluctance Machine which is very accurate and simple. The GBAM is developed for the specifications obtained from the manufacturer and magnetizing characteristic of the material used for the construction. Precise values of the parameters like Magneto Motive Force (MMF), flux linkage, inductance and torque are obtained for various rotor positions taking into account the Fringing Effect (FE). The FEA model is developed using MagNet7.1.1 for the same machine geometry used in GBAM and the results are compared with GBAM. Further another analytical model called Fourier Series Model is developed to justify the accuracy of the results obtained by the methods GBAM and FEA model. A prototype of microcontroller based SRM drive system is constructed for validating the analysis and the results are reported.

• 한국수학교육학회지시리즈A:수학교육
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• 제46권3호
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• pp.331-349
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• 2007

This study aims to improve the teaching and learning method on the conic sections. To do that the researcher analyzed the impact of dynamic geometry software on students' problem solving of the conic sections. Students often say, "I have solved this kind of problem and remember hearing the problem solving process of it before." But they often are not able to resolve the question. Previous studies suggest that one of the reasons can be students' tendency to approach the conic sections only using algebra or analytic geometry without the geometric principle. So the researcher conducted instructions based on the geometric and historico-genetic principle on the conic sections using dynamic geometry software. The instructions were intended to find out if the experimental, intuitional, mathematic problem solving is necessary for the deductive process of solving geometric problems. To achieve the purpose of this study, the researcher video taped the instruction process and converted it to digital using the computer. What students' had said and discussed with the teacher during the classes was checked and their behavior was analyzed. That analysis was based on Branford's perspective, which included three different stage of proof; experimental, intuitive, and mathematical. The researcher got the following conclusions from this study. Firstly, students preferred their own manipulation or reconstruction to deductive mathematical explanation or proving of the problem. And they showed tendency to consider it as the mathematical truth when the problem is dealt with by their own manipulation. Secondly, the manipulation environment of dynamic geometry software help students correct their mathematical misconception, which result from their cognitive obstacles, and get correct ones. Thirdly, by using dynamic geometry software the teacher could help reduce the 'zone of proximal development' of Vigotsky.

• 한국군사과학기술학회지
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• 제1권1호
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• pp.211-218
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• 1998

As a part of trajectory modulation to increase system survivability and terminal effectiveness, impact angle control is required in the terminal phase of tactical missile systems. The missile systems are not allowed to have high altitude to reduce probability of detection by sensors of missile defense systems. In this paper, an analytic form of a time-optimal control law is suggested in the case of constrained missile maneuverability and impact angle under the assumption of a zero-lag autopilot. The control law is obtained by establishing optimal missile-target engagement geometry in the vertical plane. Extension of the law for missiles with autopilot response lags requiring a numerical solution is studied by introducing an iterative algorithm for optimal switching time determination of which the initial switching instants are obtained from the analytic solution. Also suggested is a closed-form impact angle control law derived by an energy-optimal approach. The performances of the proposed guidance laws are evaluated by a series of computer runs.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1999년도 춘계학술대회논문집
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• pp.84-87
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• 1999

This paper presents a preform design method that combines the analytic method and inference of known knowledge with neural network. The analytic method is a finite element method that is used to simulate backward extrusion with pre-defined process parameters. The multi-layer network and back-propagation algorithm are utilized to learn the training examples from the simulation results. The design procedures are utilized to learn the training examples from the simulation results. The design procedures are two methods the first the neural network infer the deformed shape from the pre-defined processes parameters. The other the network infer the processes parameters from deformed shape. Especially the latest method is very useful to design the preform From the desired feature it is possible to determine the processes parameters such as friction stroke and tooling geometry. The proposed method is useful for shop floor to decide the processes parameters and preform shapes for producing sound product.

• 전자공학회논문지A
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• 제32A권8호
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• pp.107-118
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• 1995

Three-dimensional simulator for thermal oxidation process is developed. The simulator is consisted by two individual module, one is analytic-model module and the other is numerical-model module. The analytic-model which uses simple complementary-error function guarantees fast calculation in prediction of multi-dimensional oxidation process. The numerical-model which is based on boundary element method (BEM), has a good accuracy and suitable for various process conditions. The results of this study show that oxide growth is retarded at the corner of hole structure and enhanced at the corner of island structure. These effects are reson of different distribution of oxidant diffusion and mask stress. The utility of models and simulator developed in this study is demonstrated by using it to predict not only traditional shape of LOCOS but also process effects in small geometry.

• 한국기계가공학회지
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• 제13권6호
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• pp.54-60
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• 2014

In industry, several casting process are widely used to manufacture complex and accurate blank part of hard materials such as aluminum, casting steels, bronze and magnesium alloys which are difficult to manufacture in a blank shape. Even if the casting process does not high accuracy superior surface characteristics other machining process, the casting process is widely used in manufacturing blank part. Furthermore, it is difficult to select appropriate casting process a part among several casting process. for effective selection different process, a careful decision given casting application is necessary. An appropriate casting for a given material and shape condition must be selected for novice engineers in industry. In this paper, an expert system based on an analytic network process(ANP) is suggested for best selection of casting considering a prior interdependency effect among various factors such as material, geometry, process capability, economy and equipment.

• 한국수학사학회지
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• 제19권4호
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• pp.81-96
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• 2006

수학에서 분석(analysis)의 역사는 고대 그리스에서부터 시작되었다. 그리스의 기하적 분석법은 16세기 비에트$(Vi{\`{e}}te)$와 데카르트(Descartes) 이후 방정식을 이용한 문제해결(대수적 분석법)로 확장되었으며, 그 결과 대수는 분석을 위한 기술(art for analysis)로 대변되었다. 그리고 뉴헌(Newton)과 라이프니츠(Leibniz)에 의해 미적 분학이 탄생되면서 분석은 대수에서 한 걸음 더 나아가 오늘날 수학의 한 분야인 해석학으로 발전되었다. 그 동안 수학교육학 연구에서는 분석과 관련된 논의가 파푸스(Pappus)와 데카르트를 중심으로 다루어져 왔으나, 지금까지 라이프니츠의 역할과 그에 대한 연구는 거의 다루어지지 않았다. 본 연구는 라이프니츠의 철학 및 논리학을 바탕으로 그 가운데 분석과 관련된 그의 아이디어를 살펴보고, 이를 통해 그가 생각한 수학에서의 분석의 역할에 대해 논의하였다.

• Journal of the korean society of oceanography
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• 제34권4호
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• pp.231-235
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• 1999

A simple analytic model for estimating the volume transport of the Tsushima Current is considered by assuming that the transports through the connecting channels, the Korea and Tsugaru Straits, are geostrophically controled. The model gives a much simpler form of solution than that by Minato and Kimura (1980). It depends no longer on the geometry of the marginal sea and on the thickness of western boundary layer relative to the dimension of the ocean, but considers the geometry of the connecting channels ignored by Nof (1993). The external parameters turn out to be the oceanic meridional sea level difference between the two channels, the depth of the channels and the meridional position of the marginal sea. For typical value of the depth ratio of the channels to the ocean, the model gives an estimate of the Tsushima Current transport of acceptable magnitude.

• 대한수학교육학회지:수학교육학연구
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• 제12권1호
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• pp.95-108
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• 2002

In this article we drew out five definition-methods in school geometry. They are called synonymous method, denotative method, analytic method. And we analyzed them theoretically. On our analysis we tried to identify the level of common sense and the level of science in definition of those two levels on the definition-methods of circle. While the definition-method in elementary school could be regarded as the level of common sense, that in middle school could be considered as the level of science. Finally, we made the following didactical comments. Definitions in school mathematics might have the levels as regard to their roles. Thus, Mathematics teachers, curriculum developers, and text authors all need to recognize the subtle differences in the level of definition-methods.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.243.1-243.1
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• 2014

For two-dimensional grid electrodes immersed in plasmas, sheath expansion due to negative high-voltage pulse applied to the electrode generates high-energy pseudowave. The high-energy pseudowave can be used as ion beam for ion implantation. To estimate ion dose due to high-energy pseudowave, investigation on sheath expansion of grid electroes is necessary. To investigate sheath expansion, an analytic model was developed by Vlasov equation and applying the 1-D sheath expansion model to 2-D. Because of lack of generalized 2-D Child-Langmuir current, model cannot give solvable equation. Instead, for a given grid electrode geometry, the model found the relations between ion distribution functions, Child-Langmuir currents, and sheath expansions. With these relations and particle-in-cell (PIC) simulations, for given grid electrode geometry, computation time was greatly reduced for various conditions such as electrode voltages, plasma densities, and ion species. The model was examined by PIC simulations and experiments, and they well agreed.