• Earthquakes and Structures
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• 제18권6호
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• pp.719-730
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• 2020

Recently, population based optimization algorithms are developed to deal with a variety of optimization problems. In this paper, the salp swarm algorithm (SSA) is dramatically enhanced and a new algorithm is named Enhanced Salp Swarm Algorithm (ESSA) which is effectively utilized in optimization problems. To generate the ESSA, an opposition-based learning and merit function methods are added to standard SSA to enhance both exploration and exploitation abilities. To have a clear judgment about the performance of the ESSA, firstly, it is employed to solve some mathematical benchmark test functions. Next, it is exploited to deal with engineering problems such as optimally designing the benchmark buildings equipped with multiple tuned mass damper (MTMD) under earthquake excitation. By comparing the obtained results with those obtained from other algorithms, it can be concluded that the proposed new ESSA algorithm not only provides very competitive results, but also it can be successfully applied to the optimal design of the MTMD.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2007년도 제29회 추계학술대회논문집
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• pp.243-247
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• 2007

하이브리드 추진에서 연소특성을 나타내는 후퇴율 식을 초기 포트면적으로 나눈 산화제 유속이 고려된 고체연료 유속의 관계식으로 표현하였다. 초기 포트면적을 고려한 산화제 유속을 이용하여 반복 수행 없이 연소율을 쉽게 구할 수 있었고, 고체연료 유속 관계식으로 연료 형상을 간단히 설계할 수 있는 기법에 대한 연구를 수행하였다. 본 연구의 실험에서는 연료로 PE, 산화제로 GOX를 사용하였으며, 연소시간을 다양하게 하여 포트면적 변화에 따른 유속의 변화를 고려하였다. 하이브리드 추진에서, 산화제 유속의 지수가 0.5에 근접할 경우 후퇴율 관계식 보다는 고체연료 유속 관계식을 사용하는 것이 더 적합함을 확인하였다.

• Applied Science and Convergence Technology
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• 제24권4호
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• pp.102-110
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• 2015

Fluid model based numerical analysis is done to simulate a plasma processing system with electrodes at floating potential. $V_f$ is a function of electron temperature, electron mass and ion mass. Commercial plasma fluid simulation softwares do not provide options for floating electrode boundary value condition. We developed a user subroutine in CFD-ACE+ and compared four different cases: grounded, dielectric, zero normal electric field and floating electric potential for a 2D-CCP (capacitively coupled plasma) with a ring electrode.

• 한국농업기계학회:학술대회논문집
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• 한국농업기계학회 1993년도 Proceedings of International Conference for Agricultural Machinery and Process Engineering
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• pp.1212-1221
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• 1993

The shape optimization procedure applying finite element method was carried out for the specific purpose of analysis of a tractor chassis frame. Minimization of the mass as an objective function is executed under multiple constrained conditions of nodal displacements and stresses. The optimization process executions were succeeded in converging into single optimum solution. Although mass reduction and stress alleviation were attained by 40% and 26 to 24% respectively , the geometry of the shape is so complicated for fabrication that the refinement of the geometry is of necessity.

• Journal of Mechanical Science and Technology
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• 제17권1호
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• pp.40-47
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• 2003

In this paper, we constructed the analytic model of control valve as a function of electric and geometric parameters, and analyzed the influence of the design parameters on the dynamic characteristics. For improving the dynamic characteristics, optimal design is conducted by applying sequential quadratic programming method to the analytic model. This optimal design aims to minimize the response time and maximize force efficiency. By this procedure, control valve can be designed to have fast response in motion.

• Journal of the Korean Data and Information Science Society
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• 제22권4호
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• pp.811-817
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• 2011

We shall introduce a general probability mass function which includes several discrete probability mass functions. Especially, when the random variable X is Poisson, binomial, and negative binomial random variables as some special cases of the introduced distribution, the maximum likelihood estimator (MLE) and the uniformly minimum variance unbiased estimator (UMVUE) of the probability P(X ${\leq}$ t) are considered. And the efficiencies of the MLE and the UMVUE of the reliability ar compared each other.

• Journal of applied mathematics & informatics
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• 제23권1_2호
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• pp.127-140
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• 2007

We present the boundary value problem (BVP) for the heave motion due to a vertical circular cylinder in water of finite depth. The BVP is presented in terms of velocity potential function. The velocity potential is obtained by considering two regions, namely, interior region and exterior region. The solutions for these two regions are obtained by the method of separation of variables. The analytical expressions for the hydrodynamic coefficients are derived. Computational results are presented for various depth to radius and draft to radius ratios.

• Journal of Nutrition and Health
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• 제32권1호
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• pp.50-63
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• 1999

This study was conducted with 20 female gymnasts and 23 age-matched controls to examine the relationship of diet, menstrual function and bone mineral density (BMD). The results obtained are summarized as follows : Energy intake of gymnasts was 968.9$\pm$421.4kcal, and energy expenditure was 2091.4$\pm$361kcal showing negative energy balance(-1,122.5$\pm$534.6kcal). The average intakes of calcium, iron, vitamin A, thiamin, riboflavin and niacin did not meet the Recommended Dietary Allowances for their age groups. Mean age at menarche in gymnasts is 15.8$\pm$1.2 years compared with 11.8$\pm$2.8 years in age-matched controls. The profile of estradiol, progesterone, and luteinizing hormone was lower than age-matched controls but not significant. Athletic amenorrheic gymnasts(n=12) have the menstrual irregularity(n=10) and amenorrhea(n=2). A number of variables as such nutritional deficiency in diet, negative energy blasnce and hypogonadotropic hormonal status were included. The bone mineral density (BMD) of female gymnasts were significantly higher than controls for the lumbar neck(p<0.001), trochanter(p<0.01), and Ward's triangle(p<0.001), but there were no significant differences for the lumbar spine and forearm. The lumbar spine BMD had a positive correlation with age and lean body weight. The femoral neck BMD was significantly associated with age, group and lean body mass. The trochanter BMD had significant relationship with group, body mass index, energy expenditure and follicular stimulating hormone. Ward's triangle BMD were related to body mass index and follicular stimulating hormone. The significant association was deterced between forearm BMD and age and lean body weight. The major finding of this investigation is that the BMD of gymnasts were higher than age-matched controls despite the fact that gymnasts as a group had inadequate dietary calcium and a higher propensity to have an interruption of their menstrual cycle. These data indicate that grymnsts involved in sports producing significant impact loading on the skeleton had greater femoral neck, trochanter and Ward's triangle bone density than age-matched controls.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 학술대회 논문집 정보 및 제어부문
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• pp.711-713
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• 2004

In the past time, the protection relay did only a protection function. Currently, its upgraded device i.e. IED(Intelligent Electric Device) has been designed to protect, control, and monitor the whole power system automatically. Also the device is desired to successfully measure important elements of the power system. This paper considers design method of a digital protection IED with a function of measuring various elements and a communication function. The protection IED is composed of the specific function modules that are signal process module, communication module, input/output module and main control module. A signal process module use a DSP processor for analysis of input signal. Main control module use a embedded processor, Xscale, that has an ARM Core. The communication protocol uses IEC61850 protocol that becomes standard in the future. The protection IED is able to process mass information with high-performance processor. As each function module is designed individually, the reliability of the device can be enhanced.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2009년도 춘계학술대회 논문집 특별세미나,특별/일반세션
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• pp.359-366
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• 2009

This paper aims for analyzing the vibration serviceability of train by simply expressing its vertical vibration when it passes a railway bridge. For this purpose, bridge-train transfer function was derived and bridge-train interaction analysis was performed by using the derived function. The bridge-train transfer function was developed with the assumption that train is a single mass-spring system, and bridge-train interaction analysis was performed on simple beams of KTX passenger car. The vertical acceleration signals of passenger cars obtained from bridge-train interaction analysis were compared with them of cars obtained from the bridge-train transfer function. As a result, it could be estimated to express the vertical vibration inside the passenger car required for vibration serviceability evaluation by using the vertical vibration of bridges obtained from moving load analysis. Therefore, it may be possible to evaluate the vibration serviceability of railway bridges considering bridge-train interaction effect.