• 아동학회지
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• 제22권4호
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• pp.149-166
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• 2001

This study examined differences in function, structure, and satisfaction of adolescent friendships by differing patterns of internet usage and of real life versus internet friendships. Subjects were 396 male and female 10th grade students. Data were collected with structured questionnaires and analyzed by SPSS. Findings were that the internet functioned as a major field of interpersonal relationships for Korean adolescents. Among 3 types of internet usage patterns, pursuit of interpersonal relationship, constituted most of the functioning and the most intimate friendships and game pleasure had the fewest and least intimate friendships both in real life and on the internet. Subjects addicted to the internet had the most functioning friendships and the highest level of intimacy in friendships. As the level of internet addiction increased, the level of satisfaction in friendships in real life decreased while the level of satisfaction of friendships through the internet increased.

• BMB Reports
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• 제41권6호
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• pp.444-447
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• 2008

Trypanothione reductase is an important target enzyme for structure-based drug design against Leishmania. We used homology modeling to construct a three-dimensional structure of the trypanothione reductase (TR) of Leishmania infantum. The structure shows acceptable Ramachandran statistics and a remarkably different active site from glutathione reductase(GR). Thus, a specific inhibitor against TR can be designed without interfering with host (human) GR activity.

• Clinical and Experimental Pediatrics
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• 제52권7호
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• pp.752-755
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• 2009

It is well known that hemodynamic load is one of the most important determinants of cardiac structure and function. Circadian variations in blood pressure (BP) are usually accompanied by consensual changes in peripheral resistance and/or cardiac output. In recent years, reduction in circadian variations in BP and, in particular, loss of nocturnal decline of BP were observed in hypertensive patients with left ventricular hypertrophy (LVH). The patients with only a slight or no loss of nocturnal decline of BP were considered "non-dippers". Regression of LVH was observed after prolonged antihypertensive therapy. Restoration of the circadian rhythm of BP was also observed. However, the classification of patients into "dippers" and "non-dippers" is arbitrary and poorly standardized and repeatable, and in the recent studies, most hypertensive patients with LVH were "dippers". Therefore, we should be particularly cautious about the conclusions drawn using this index. On the other hand, reduced activity of low-pressure cardiopulmonary baroreceptors and impaired day-to-night modulation of autonomic nervous system activity were observed in patients with only LVH. Therefore, alterations in cardiac structure may impair BP modulation. On the other hand, the reverse can also be trueprimary alterations in BP modulation, through a persistently elevated afterload, can increase cardiac mass. Thus, the interrelationship between cardiac structure and BP modulation is complex. Hence, new and more specific methods of evaluating circadian changes in BP are needed to better clarify the abovementioned reciprocal influences.

• 한국정밀공학회지
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• 제10권2호
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• pp.104-113
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• 1993

Characteristics of fiber-reinforced thermoplastic sheet depend on the quantity and shape of fibers. During a molding process of composites, the fiber-maxtrix separation and fober orientation are caused by the flow during the molding process. As a result, the product tends to be nonhomogeneous and anisotropic. Hence, it is very important to clarify the relations between separation-orientation and molding conditions. The correlation between the separation and the orientation have to be clarified for designing the fiber structure. In this paper, the degree of nonhomogeneity which is a measure of the separation is obtained using one-dimensional rectangular shaped part compression molding. And the orientation function is defined and measured by the image processing using soft X-rayed photograph and image scammer. Correlation between the degree of nonhomogeneity and the orientation function is discussed.

• 항공우주시스템공학회지
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• 제15권2호
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• pp.1-9
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• 2021

In this paper, a thickness compensation function is introduced to consider the shear deformation and warping effect resulting from increased thickness in the composite multi-cell wing box. The thickness compensation function is used to perform the structure optimization of the multi-cell. It is determined by minimizing the error of an analytical formula using solid mechanics and the Ritz method. It is used to define a structural performance prediction expression due to the increase in thickness. The parameter is defined by the number of spars and analyzed by the critical buckling load and the limited failure index as a response. Constraints in structural optimization are composed of displacements, torsional angles, the critical buckling load, and the failure index. The objective function is the mass, and its optimization is performed using a genetic algorithm.

• Structural Engineering and Mechanics
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• 제20권6호
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• pp.713-726
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• 2005

Based on the improved first order Taylor interval expansion, a new interval analysis method for the static or dynamic response of the structures with interval parameters is presented. In the improved first order Taylor interval expansion, the first order derivative terms of the function are also considered to be intervals. Combining the improved first order Taylor series expansion and the interval extension of function, the new interval analysis method is derived. The present method is implemented for a continuous beam and a frame structure. The numerical results show that the method is more accurate than the one based on the conventional first order Taylor expansion.

• 대한교통학회지
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• 제25권6호
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• pp.129-140
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• 2007

대중교통 운행계획 수립과정은 이론적인 연구의 특성에 따라 설계, 운영, 그리고 평가 단계로 구분할 수 있다. 운영단계와 평가단계에서 이루어지는 연구들에 대해서는 비교적 체계적으로 정리된 연구와 보고서들이 있으나 설계단계에 관한 연구들은 체계적으로 정리된 적이 없다. 본 연구에서는 대중교통 시스템설계에 관한 기존의 연구들을 검토하여 체계적으로 정리하였다. 또한 해당 연구들의 모형 구조를 자세히 분석하여 이의 풀이법을 정리하여 제시하였다. 설계단계에서 결정되는 결정변수로는 노선(망)의 구조, 노선간격 및 위치, 정류장 간격, 배차간격, 및 소요차량수 등이 있다. 노선설계에 관한 해석적 연구에서는 시스템의 총 비용이 목적함수로 많이 사용되고 이는 이용자의 접근비용, 대기비용, 그리고 통행비용으로 구성되는 이용자비용과 운영자의 운영비용으로 구성된다. 목적함수로 사용되는 대중교통 시스템의 총 비용은 노선간격, 배차간격 등의 결정변수들에 대해 미분가능하고 미분값을 0으로 만드는 값이 존재하며 2계 미분값이 양수이기 때문에 전역 최적해가 존재한다. 따라서 목적함수의 미분값을 0으로 만드는 결정변수가 목적함수를 최소로 만드는 최적치가 되며 이 최적치에서 각 부분 함수값들은 모두 동일해지게 된다. 본 연구는 대중교통 운행계획 중 설계단계의 해석적 연구에 대한 체계적인 이해를 도모할 것이며, 관련 연구를 활성화시키는데 큰 도움이 될 것으로 기대된다.

• 설비공학논문집
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• 제6권2호
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• pp.140-154
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• 1994

Experimental studies were performed to determine the characteristics of flow structure and pressure drop in 15 : 1 scale models of multi-louvered fin heat exchanger in a wide range of variables($L_P/F_P=0.5{\sim}1.23$, ${\theta}=27^{\circ}{\sim}37^{\circ}$, $Re_{LP}=50{\sim}2000$). Flow structure inside the louvered fin was analyzed by smoketube method and new correlations on flow efficiency and drag coefficient were suggested. The new definition for flow efficiency, which modifies the existing flow efficiency, can predict the flow efficiency in the range above mentioned and is represented as a function of Reynolds number, louver pitch to fin pitch ratio, louver angle at low Reynolds number. Drag coefficient which is defined here is a function of Reynolds number, louver pitch to fin pitch ratio, louver angle below critical Reynolds number, and can be represented by a function of louver pitch to fin pitch ratio only above the critical Reynolds number.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.635-639
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• 2004

In this paper, we present a novel approach for the structure of Fuzzy Neural Network(FNN) based on wavelet function and apply this network structure to the modeling of chaotic nonlinear systems. Generally, the wavelet fuzzy model(WFM) has the advantage of the wavelet transform by constituting the fuzzy basis function(FBF) and the conclusion part to equalize the linear combination of FBF with the linear combination of wavelet functions. However, it is very difficult to identify the fuzzy rules and to tune the membership functions of the fuzzy reasoning mechanism. Neural networks, on the other hand, utilize their learning capability for automatic identification and tuning. Therefore, we design a wavelet based FNN structure(WFNN) that merges these advantages of neural network, fuzzy model and wavelet transform. The basic idea of our wavelet based FNN is to realize the process of fuzzy reasoning of wavelet fuzzy system by the structure of a neural network and to make the parameters of fuzzy reasoning be expressed by the connection weights of a neural network. And our network can automatically identify the fuzzy rules by modifying the connection weights of the networks via the gradient descent scheme. To verify the efficiency of our network structure, we evaluate the modeling performance for chaotic nonlinear systems and compare it with those of the FNN and the WFM.

• International Journal of Fuzzy Logic and Intelligent Systems
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• 제4권1호
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• pp.111-118
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• 2004

In this paper, we present a novel approach for the structure of Fuzzy Neural Network(FNN) based on wavelet function and apply this network structure to the solution of the tracking problem for mobile robots. Generally, the wavelet fuzzy model(WFM) has the advantage of the wavelet transform by constituting the fuzzy basis function(FBF) and the conclusion part to equalize the linear combination of FBF with the linear combination of wavelet functions. However, it is very difficult to identify the fuzzy rules and to tune the membership functions of the fuzzy reasoning mechanism. Neural networks, on the other hand, utilize their learning capability for automatic identification and tuning. Therefore, we design a wavelet based FNN structure(WFNN) that merges these advantages of neural network, fuzzy model and wavelet transform. The basic idea of our wavelet based FNN is to realize the process of fuzzy reasoning of wavelet fuzzy system by the structure of a neural network and to make the parameters of fuzzy reasoning be expressed by the connection weights of a neural network. And our network can automatically identify the fuzzy rules by modifying the connection weights of the networks via the gradient descent scheme. To verify the efficiency of our network structure, we evaluate the tracking performance for mobile robot and compare it with those of the FNN and the WFM.