• 한국정보통신학회논문지
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• 제17권10호
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• pp.2330-2336
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• 2013

사람이 만든 시스템들은 서로 상호 작용하는 여러 개의 요소 시스템들로 이루어지기 때문에, 시스템 오류로 인한 비정상적인 현상이 발생하였을 경우 그 논리적 오류를 분석하는 것이 매우 어렵다. 또한 높은 품질과 안정적인 시스템 개발을 위해서는 논리적 해석 방법이 반드시 적용되어질 필요가 있다. 본 논문에서는 시스템의 합성과 축소화 두 연산을 정의하고 이것을 기반으로 시스템을 해석하는 방법을 제안한다. 제안한 방법에서는 시스템의 합성과 축소화 과정을 반복적으로 수행하되 내부 이벤트들을 간소화 시킴으로써 주요 입출력 이벤트들의 응답이 같음을 확인하는 방법이다. 제안한 방법의 효용성을 보이기 위해 기존의 간단한 통신 프로토콜에 대하여 적용하여 보았으며, 전송매체에 전달된 메시지는 수신측에 반드시 전달된다는 것을 확인할 수 있었다.

• 대한간호학회지
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• 제35권2호
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• pp.270-282
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• 2005

Purpose: This study was conducted to develop a comprehensive cognitive rehabilitation program that can be easily applied to brain injured patients by family members or nurses in community or hospital settings. Methods: A Systemic literature review design was used. Thirty-three related studies were reviewed. Result: Based on the results of the literature review, the training tasks for attention were designated to enhancing 4 hierarchical areas, i.e., focused, selective, alternating, and divided attention. On the other hand, the memory rehabilitation tasks mainly consisted of mnemonic skills, such as the association method which helps patients memorize given information by linking together common attributes, the visual imagery method, and self-instruction method. The problem solving rehabilitation program included a task of games or plays which stimulated the patients' curiosity and interest. The training tasks for problem solving were to encourage the process of deriving reasonable solutions for a problematic situation resembling real problems that the patients were faced with in their everyday life. Conclusion: It is expected that the cognitive rehabilitation program developed from this study could help patients having difficulty in their every day life, due to a reduced cognitive ability resulting from brain injury, to effectively adapt to every day life.

• Transactions on Electrical and Electronic Materials
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• 제18권2호
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• pp.97-102
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• 2017

A current transformer (CT) is a type of sensor that consists of a combination of electric and magnetic circuits, and it measures large ac currents. When a large amount of current flows into the primary winding, the alternating magnetic flux in the iron core induces an electromotive force in the secondary winding. The characteristics of a CT are determined by the iron core design because the iron core is saturated above a certain magnetic flux density. In particular, when a large current, such as a current surge, is input into a CT, the iron core becomes saturated and the induced electromotive force in the secondary winding fluctuates severely. Under these conditions, the CT no longer functions as a sensor. In this study, the characteristics of the secondary winding were investigated using the time-difference finite element method when a current surge was provided as an input. The CT was modeled as a two-dimensional analysis object using constraints, and the saturation characteristics of the iron core were evaluated using the Newton-Rhapson method. The results of the calculation were compared with the experimental data. The results of this study will prove useful in the designs of the iron core and the windings of CTs.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제3권2호
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• pp.1-4
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• 1999

The Helmholtz equation is very important in physics and engineering. However, solution of the Helmholtz equation is in general known as a very difficult phenomenon. For if the ${\omega}$ is negative, the FDM discretized linear system becomes indefinite, whose solution by iterative method requires a very clever preconditioner. In this paper we assume that ${\omega}$ is nonnegative, and determine the optimal ${\rho}$ parameter for the three dimensional ADI iteration for the Helmholtz equation. The ADI(Alternating Direction Implicit) method is also getting new attentions due to the fact that it is very suitable to the vector/parallel computers, for example, as a preconditioner to the Krylov subspace methods. However, classical ADI was developed for two dimensions, and for three dimensions it is known that its convergence behaviour is quite different from that in two dimensions. So far, in three dimensions the so-called Douglas-Rachford form of ADI was developed. It is known to converge for a relatively wide range of ${\rho}$ values but its convergence is very slow. In this paper we determine the necessary conditions of the ${\rho}$ parameter for the convergence and optimal ${\rho}$ for the three dimensional ADI iteration of the Peaceman-Rachford form for the real Helmholtz equation with nonnegative ${\omega}$. Also, we conducted some experiments which is in close agreement with our theory. This straightforward extension of Peaceman-rachford ADI into three dimensions will be useful as an iterative solver itself or as a preconditioner to the the Krylov subspace methods, such as CG(Conjugate Gradient) method or GMRES(m).

• 대한한의학원전학회지
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• 제30권4호
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• pp.83-93
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• 2017

Objective : Doctors' discussions on Makwon's warm-disease are studied in an effort to contemplate a way to use the outcome in practice. Method : Doctors' discussions on Makwon as found in researches and texts are categorized into physical and pathologica, and their symptoms and treatments are analyzed. Result & Conclusion : Many doctors of warm disease explained that, in terms of the physical aspect, Makwon is closely related to stomach. Some doctors also mentioned its relationship with triple engizers, defense and nutrient qi, and spleen. In terms of pathology, most of the doctors considered Makwon to be a hiding place of foul turbidity pathogen, and explained that a treatment has to be applied before the disease pattern worsens. Diverse syndroms of Makwonwere introduced. Their discussions mainly revolved around warm and epidemic or category of dampness-heat diseases. Alternating chills and fever was also mentioned often, and generalized pain, nausea, tongue of thick and slimy fur symptoms are shown. Ouguk's Dalwonneum is used as the basic treatment. The most effective prevention method of the incubation of pathogen are the symptoms that allows the analysis of the mechanism of disease. Therefore, a good utilization method of resolve turbidity with aroma or spices may contribute to the prevention of Makwon-disease in terms of cultural aspect.

• Journal of Power Electronics
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• 제18권4호
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• pp.1268-1277
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• 2018

A relatively high operating frequency is required for efficient wireless power transfer (WPT). However, the alternating current (AC) resistance of coils increases sharply with operating frequency, which possibly degrades overall efficiency. Hence, the evaluation of coil AC resistance is critical in selecting operating frequency to achieve good efficiency. For a Litz wire coil, AC resistance is attributed to the magnetic field, which leads to the skin effect, the proximity effect, and the corresponding conductive resistance and inductive resistance in the coil. A numerical calculation method based on the Biot-Savart law is proposed to calculate magnetic field strength over strands in Litz wire planar spiral coils to evaluate their AC resistance. An optimized frequency can be found to achieve the maximum efficiency of a WPT system based on the predicted resistance. Sample coils are manufactured to verify the resistance analysis method. A prototype WPT system is set up to conduct the experiments. The experiments show that the proposed method can accurately predict the AC resistance of Litz wire planar spiral coils and the optimized operating frequency for maximum efficiency.

• 대한전자공학회논문지SD
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• 제41권4호
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• pp.101-112
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• 2004

본 논문에서는 3차원 인터커넥트(3D interconnect) 구조를 해석하기 위하여 ADI-유한차분시간영역(ADI-FDTD: Alternating Direction Implicit Finite Difference Time Domain)법으로 맥스웰 회전 방정식(Maxwell's curl equation)을 계산하는 수치 해석 모델을 개발하였고, 개발한 ADI-유한차분시간영역법을 이용하여 3.3 V CMOS 기술로 설계된 샘플러 회로의 일부의 영역에 대해 컴퓨터 모의 실험 결과하여 입력된 구형 전압 신호가 금속 배선을 거치면서 5∼10 ps의 신호 지연과 0.1∼0.2 V의 신호 왜곡이 발생되는 것을 확인하였다. 결론적으로 ADI-유한차분시간영역법을 이용한 풀-웨이브 해석을 통하여 고속의 VLSI 인터커넥트에서의 전자기 현상을 정확하게 분석할 수 있음을 제시하였다.

• 한국전기전자재료학회논문지
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• 제18권2호
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• pp.164-168
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• 2005

Piezoelectric ZnO thin films were for the first time formed on SiO$_2$/Si(100) substrate using 2-step deposition, atomic layer deposition(ALD) and RF magnetron sputtering deposition, for film bulk acoustic resonator(FBAR) applications. The ZnO buffer layer by ALD was deposited using alternating diethyl zinc(DEZn)/$H_2O$ exposures and ultrahigh purity argon gas for purging. The ZnO films by 2-step deposition revealed stronger c-axis-preferred orientation and smoother surface than those by the conventional RF sputtering method. The solidly mounted resonator(SMR)-typed FBAR fabricated by using 2-step deposition method revealed higher quality factor of 580 and lower return loss of -17.35dB. Therefore the 2-step deposition method in this study could be applied to the FBAR device fabrication.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1994년도 하계학술대회 논문집 A
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• pp.147-149
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• 1994

In designing high efficiency electrical machines, calculation of iron loss is very important. And it is reported that in the induction motor and in the T-joint of 3 phase transformer, there occurred rotational magnetic field and much iron loss is generated owing to this field. In this paper, rotational power loss in the electrical machine under rotational magnetic field is discussed. Until now, loss analysis is based on the magnetic properties under alternating field. And with this one dimensional magnetic propertis, it is difficult to express iron loss under rotational field. In this paper, we used two dimensional magnetic property data for the numerical calculation of rotational power loss. We used finite element method for calculation and the analysis model is two dimensional magnetic property measurement system. We used permeability tensor instead of scalar permeability to present two dimensional magnetic properties. And in this case, we cannot uniquely define energy functional because of the asymmetry of the permeability tensor, so Galerkin method is used for finite element analysis.

• 한국항만학회지
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• 제13권2호
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• pp.419-426
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• 1999

It is essential for port planning, coastal zone management and environmental impact study to analyze the variation of current and water quality due to the development of water area and discharged water from estuary barrage and basin etc. Mokpo sea area downstreams from a long river and two large basins, the Yongsan river and Yongam-Kumho basins discharging much of water through water gates for the purpose of flood control and prohibition of salt intrusion to the inland fresh water area. In this study, the numerical calculations were carried out for the analysis of diffusion characteristics due to discharging operation, adapting the results of tidal current simulation ADI methord is applied to the governing equation for the movement of sea water and diffusion and 6-point method to the advection terms of diffusion equation. As the results of this study, it is known that the discharging operation causes increasing and/or decreasing of current velocity and enlarging and/or depressing of pollutant diffusion limits depending on the distance from the discharging gates and the mode of discharging operation. To utilize these result, the linked gate operation and the method increasing exchange of sea water must be considered.