• Journal of Electrical Engineering and Technology
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• v.8 no.3
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• pp.428-435
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• 2013

Flexible AC Transmission System (FACTS) application study on enhancing the flexibility of AC power system has continued to make progress. A thyristor-controlled series capacitor (TCSC) is a useful FACTS device that can control the power flow by adjusting line impedances and minimize the loss of power flow and voltage drop in a transmission system by adjusting line impedances. Reduced power flow loss leads to increased loadability, low system loss, and improved stability of the power system. This study proposes the optimal location and compensation rate method for TCSCs, by considering both the power system loss and voltage drop of transmission systems. The proposed method applies a multi-objective function consisting of a minimizing function for power flow loss and voltage drop. The effectiveness of the proposed method is demonstrated using IEEE 14- and a 30-bus system.

• Journal of applied mathematics & informatics
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• v.19 no.1_2
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• pp.439-445
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• 2005

This paper is to investigate the approximate confidence limits of the reliability performances (such as failure rate, reliability function and average life) for a cold standby series system. The Bayesian approximate upper confidence limit of failure rate is obtained firstly, and next Bayesian approximate lower confidence limits for reliability function and average life are presented. The expressions for calculating Bayesian lower confidence limits of the reliability function and average life are also obtained, and an illustrative example is examined numerically by means of the Monte-Carlo simulation. Finally, the accuracy of confidence limits is discussed.

• YAKHAK HOEJI
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• v.23 no.1
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• pp.31-39
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• 1979

Bethanidine was administered into the lateral ventricle of the rabbit brain for the investigation of the effect on the renal function in doses ranging from 0.1 to 1.0mg/kg. In a dose of 0.1 mg/kg, bethanidine did not exhibit significant changes on the renal function of the rabbit, on the other hand, in the doses of 0.3 and 1.0mg/kg bethanidine elicited the reduction of renal plasma flow and glomerular filtration rate with a marked antidiuresis, at the same time bethanidine produced the decrement of urinary sodium and potassium excretion. After intravenous pretreatment of phentolamine, intraventricular bethanidine in a dose of 0.3mg/kg did not produced the antidiuresis and the decrement of urinary sodium and potassium excretion, wherease renal plasma flow and glomerular filtration rate reduced as before of phentolamine pretreatment although the durations of their reduction were shortened. These observations suggest that bethanidine induces the antidiuresis through the centrally mediated mechanism which interposed other factors in addition to sympathetic stimulation affected by phentolamine, alpha adrenergic blocking agent.

• Solar Energy
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• v.18 no.4
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• pp.39-47
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• 1998

The natural convection heat transfer in a vertical plate with discrete heat sources was studied experimentally. The particular interest was the thermal interaction of the heat sources. In this study, the radiative and conductive heat transfer were considered as heat loss, Thus, the net convective heat transfer rate was presented as adiabatic temperature and thermal wake function. As a results, for non-uniform heating condition, heat input ratio(q1/q2) was most dominant parameter for the thermal wake function. The convective heat transfer rate is decreased with the increasing of channel ratio. For the range of $7.50{\times}10^5<Rac<8.66{\times}10^6$, a useful correlation was proposed as a function of channel Rayleigh number.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.2B
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• pp.21-26
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• 2005

A routing algorithm using the Hopfield Neural Netork (HNN) is proposed in this paper. The proposed algorithm modifies the energy function for achieving the optimality of the solution and higher convergence rate. Experimental results show that the proposed algorithm outperforms convensional methods both in optimality and convergence.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.38 no.2
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• pp.127-136
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• 1989

This paper describes the parameter convergence properties of an adaptive system to identify a single-input single-output plant model. It is demonstrated that, by using power spectrum analysis, the persistency of excitation (PE) condition in order to guarantee the exponential stability of the adaptive control system can be transformed into the positive definite behavior for the auto-correlation function matrix of adaptive signal. The existence of parameter nominal values can be analyzed by this condition and the convergence rates of parameter are determined by examining the auto-correlation function. We may use the sufficient richness (SR) of input spectrum instead of the PE condition to analyze the parameter boundedness. It can be shown that the eigen values of the auto-correlation function are always related with adaptive gain, input amplitude and positions or numbers of input spectra. In each case, the variation of parameter convergence rate can be also verified.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.10
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• pp.702-709
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• 2008

In this paper, the optimal thermal storage time of an air-conditioning system with slab thermal storage in office building was analyzed on the basis of the gradient method algorithm. The sum of room temperature deviation and heat extraction rate was set to the criterion function. It was calculated that four hours is the optimal thermal storage time under the standard evaluation criterion. Furthermore, some case studies were executed by controlling ratio of weight functions of room temperature deviation and heat extraction rate in criterion function. It is possible to design many kinds of optimal operation of an air-conditioning system with slab thermal storage by controlling ratio of the weight functions in criterion function.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.11
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• pp.73-81
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• 1996

This paper presents a general procedure for the selection of the machining parameters for a given machine which provides the maximum material removal rate using a Genetic Algorithms(GAs). Some constraints were given in order to achieve desired surface integrity and cutting tool life conditions as wel as to protect machine tool. Such a constrained problem can be transformaed to unconstrained problem by associating a penalty with all constraint violations and the penalties are included in the function evaluation. Genetic Algorithms can be used for finding global optimum cutting conditions with respect to the above cost function transformed by pennalty function method. From the demonstration of the numerical results, it was found that the near optimal conditions could be obtained regardless of complex solution space such as cutting environment.

• Communications for Statistical Applications and Methods
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• v.30 no.3
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• pp.245-258
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• 2023

This study proposes a modification to the objective function of the support vector machine for the linearly non-separable case of a binary classifier y_i ∈ {-1, 1}. The modification takes into account the position of each data item x_i from its corresponding class centroid. The resulting optimization function involves the centroid mean vector, and the spread of data besides the support vectors, which should be minimized by the choice of hyper-plane β. Theoretical assumptions have been tested to derive an optimal separable hyperplane that yields the minimal misclassification rate. The proposed method has been evaluated using simulation studies and real-life COVID-19 patient outcome hospitalization data. Results show that the proposed method performs better than the classical linear SVM classifier as the sample size increases and is preferred in the presence of correlations among predictors as well as among extreme values.

• Journal of Korean Academy of Nursing
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• v.39 no.4
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• pp.584-593
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• 2009

Purpose: The purpose of this study was to investigate the effect of stretching, muscle strengthening, and walking exercise on the cardiopulmonary function and health-related quality of life in hemodialysis patients. Methods: Twenty-one patients in the intervention and the control group participated in the exercise respectively on maintenance hemodialysis at four university hospitals. The exercise was composed of 20 to 60 min per session, 3 sessions a week for 12 weeks. The effect of exercise was assessed by cardiopulmonary function (peak oxygen uptake, peak ventilation, peak respiration rate, maximal heart rate, and exercise duration) using a cycle ergometer. Grip strength was measured by dynamometer, and flexibility was measured by sit and reach measuring instrument. Health-related quality of life was measured using Medical Outcomes Study Short Form-36. Results: Peak oxygen uptake, peak ventilation, peak respiration rate, exercise duration, grip strength, flexibility, and physical component scale were significantly improved in the intervention group after 12 week's exercise compared to the control group. Conclusion: These findings indicate the exercise can improve cardiopulmonary function, grip strength, flexibility, and physical component scale of health-related quality of life in hemodialysis patients.