• Advances in materials Research
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• 제1권2호
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• pp.115-128
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• 2012

The structural and electrical properties of $(1-x)Ba(Sm_{1/2}Nb_{1/2})O_3-xBaTiO_3$; ($0{\leq}x{\leq}1$) ceramics were prepared by conventional ceramic technique at $1375^{\circ}C$/7 h in air atmosphere. The crystal symmetry, space group and unit cell dimensions were derived from the X-ray diffraction (XRD) data using FullProf software whereas crystallite size and lattice strain were estimated from Williamson-Hall approach. XRD analysis of the compound indicated the formation of a single-phase cubic structure with the space group Pm m. Dielectric study revealed that the compound $0.75Ba(Sm_{1/2}Nb_{1/2})O_3-0.25BaTiO_3$ is having low and ${\varepsilon}^{\prime}$ and ${\varepsilon}^{{\prime}{\prime}}$ a low $T_{CC}$ (< 5%) in the working temperature range (up to+$100^{\circ}C$) which makes this composition suitable for capacitor application and may be designated as 'Stable Low-K' Class I material as per the specifications of the Electronic Industries Association. The correlated barrier hopping model was employed to successfully explain the mechanism of charge transport in the system. The ac conductivity data were used to evaluate the density of states at Fermi level, minimum hopping length and apparent activation energy of the compounds.

• Journal of Electrical Engineering and Technology
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• 제4권3호
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• pp.323-329
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• 2009

This paper presents a new approach for thermal unit commitment (UC) using a differential evolution (DE) algorithm. DE is an effective, robust, and simple global optimization algorithm which only has a few control parameters and has been successfully applied to a wide range of optimization problems. However, the standard DE cannot be applied to binary optimization problems such as UC problems since it is restricted to continuous-valued spaces. This paper proposes binary differential evolution (BDE), which enables the DE to operate in binary spaces and applies the proposed BDE to UC problems. Furthermore, this paper includes heuristic-based constraint treatment techniques to deal with the minimum up/down time and spinning reserve constraints in UC problems. Since excessive spinning reserves can incur high operation costs, the unit de-commitment strategy is also introduced to improve the solution quality. To demonstrate the performance of the proposed BDE, it is applied to largescale power systems of up to 100-units with a 24-hour demand horizon.

• International Journal of Automotive Technology
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• 제3권4호
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• pp.165-170
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• 2002

For a vehicle Anti-lock Braking System (ABS), the control target is to maintain friction coefficients within maximum range to ensure minimum stopping distance and vehicle stability. But in order to achieve a directionally stable maneuver, tire side forces must be considered along with the braking friction. Focusing on combined braking and turning operation conditions, this paper presents a new control scheme for an ABS controller design, which calculates optimal target wheel slip ratio on-line based on vehicle dynamic states and prevailing road condition. A fuzzy logic approach is applied to maintain the optimal target slip ratio so that the best compromise between braking deceleration, stopping distance and direction stability performances can be obtained for the vehicle. The scheme is implemented using an 8-DOF nonlinear vehicle model and simulation tests were carried out in different conditions. The simulation results show that the proposed scheme is robust and effective. Compared with a fixed-slip ratio scheme, the stopping distance can be decreased with satisfactory directional control performance meanwhile.

• International Journal of Fuzzy Logic and Intelligent Systems
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• 제11권1호
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• pp.59-64
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• 2011

In 2001, the notion of a fuzzy poset defined on a set X via a triplet (L, G, I) of functions with domain X ${\times}$ X and range [0, 1] satisfying a special condition L+G+I = 1 is introduced by J. Negger and Hee Sik Kim, where L is the 'less than' function, G is the 'greater than' function, and I is the 'incomparable to' function. Using this approach, we are able to define a special class of fuzzy posets, and define the 'skeleton' of a fuzzy poset in view of major relation. In this sense, we define the linear discrepancy of a fuzzy poset of size n as the minimum value of all maximum of I(x, y)${\mid}$f(x)-f(y)${\mid}$ for f ${\in}$ F and x, y ${\in}$ X with I(x, y) > $\frac{1}{2}$, where F is the set of all injective order-preserving maps from the fuzzy poset to the set of positive integers. We first show that the definition is well-defined. Then, it is shown that the optimality appears at the same injective order-preserving maps in both cases of a fuzzy poset and its skeleton if the linear discrepancy of a skeleton of a fuzzy poset is 1.

• 한국정보전자통신기술학회논문지
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• 제3권1호
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• pp.47-52
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• 2010

본 논문에서는 능동적 적외선 조명을 이용한 3차원 얼굴 방향 식별을 위한 새로운 방법을 제안하고자 한다. 적외선 조명 하에서 밝게 나타나는 동공을 효과적으로 실시간 검출하여 추적할 수 있는 알고리즘을 제안한다. 다른 방향의 얼굴들에서 동공의 기하학적 왜곡을 탐지하여, 3차원 얼굴 방향과 동공의 기하학적 특성 사이의 관계를 나타낸 학습 데이터를 사용하여 고유한 눈 특징 공간을 구축하였고, 입력된 질의 영상에 대한 3차원 얼굴 방향을 고유한 눈 특징 공간을 사용하여 실시간으로 얼굴 방향을 측정할 수 있었다. 실험결과 카메라에 근접한 실험 대상자들에 대하여 최소 94.67%, 최고 100% 의 식별 결과를 나타내었다.

• 한국산학기술학회논문지
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• 제9권5호
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• pp.1134-1138
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• 2008

본 논문에서는 전력분배기의 설계에 필수적인 분포정수 임피던스 변환기의 합성법을 제시하고, 이에 의하여 광대역 전력분배기를 설계한다. 변환기의 전달함수는 Chebyshev 근사로 합성하며, 변환기의 소자값은 최소 삽입손실(MIL)과 리플에 대하여 계산된다. 변환기의 요구 성능은 전달함수의 MIL과 리플을 최적화함으로써 구할 수 있다. 이의 응용 예로써 $2{\sim}8GHz$에서 동작하는 4-경로 전력분배기(four-way power divider)를 설계하였다. 실험 결과, 전력분배기는 주어진 주파수 대역에서 설계치에 근접하는 성능을 나타내어, 분포정수 회로합성에 의한 변환기의 설계는 전력분배기의 설계에 유용하게 사용될 수 있음을 입증하였다.

• Environmental Engineering Research
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• 제19권4호
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• pp.375-380
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• 2014

Macro fouling due to blue mussels (Mytilus edulis) has affected negatively on the operation efficiency and eventual system failure of offshore structures and coastal power stations. A certain range of chlorine (0.05, 0.1, 0.3, 0.5, 0.7 and 1.0 mg/L) was applied on the mussel larvae to identify the survival rate with respect to various exposure times under laboratory condition. The ciliary movement of the larvae was used to check their survival. The 1.0 mg/L of chlorine shows to 97% of larvae mortality whereas 0.7 mg/L of chlorine shows only 16% of larvae mortality. Minimum exposure times for 100% larvae mortality ranged from 300 to 20 min for increasing concentrations of chlorine (0.05~1.0 mg/L). It was found that 1 mg/L of chlorine was 4 times more efficient than 0.7 mg/L of that, and 15 times more than 0.05 mg/L of chlorine dose. Data collected and analyzed here will help plant operators to optimize chlorine dosage and its scheduling.

• 대한전기학회논문지:전력기술부문A
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• 제53권5호
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• pp.285-295
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• 2004

The outage cost assessment has an important position for determination of the optimal level or optimal range of reliability for power system expansion planning. Establishing the worth of service reliability is a very difficult and subjective task. While the utility cost(reliability cost) will generally increase as consumers are provided with higher reliability, the consumer costs(reliability worth) associated with supply interruptions will decrease as the reliability increases. The total costs to society are the sum of these two individual costs and the optimum or target level of reliability is achieved at minimum point of the total cost curve. This paper addresses the role, need and assessment algorithms and methodologies of the outage cost in power system expansion planning. In a case study, the outage cost has been assessed using macro approach for our country 15years(1986-200l) in the case study. Additionally, determination processing of optimum reliability level is presented in another case study with the five buses MRBTS.

• 설비공학논문집
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• 제24권2호
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• pp.155-163
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• 2012

The aim of this study is to evaluate the performance of the GHP system with 150 energy piles for a commercial building. In order to demonstrate the feasibility of a sustainable performance of the system, simulations were conducted over 1-year and 20-year periods, respectively. The 1-year simulation results showed that the maximum and minimum temperatures of brine returning from the energy piles were $23.80^{\circ}C$ and $7.90^{\circ}C$, which were in a range of design target temperatures. In addition, after 20 years' operation, these returning temperatures decreased slowly to $23.05^{\circ}C$ and $6.98^{\circ}C$, and finally reached to stable state. The results also showed that the energy piles injected heat of 65.6 MWh to the ground and extracted heat of 96.0 MWh from the ground, respectively. Also, it is expected this GHP system with energy piles can operate with average SPF of more than 4.15 for long term.

• 한국정보통신학회논문지
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• 제8권3호
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• pp.727-732
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• 2004

본 논문에서는 능동적 적외선 조명을 이용한 3차원 얼굴 방향 식별을 위한 새로운 방법을 제안하고자 한다. 적외선 조명 하에서 밝게 나타나는 동공을 효과적으로 실시간 검출하여 추적할 수 있는 알고리즘을 제안한다. 다른 방향의 얼굴들에서 동공의 기하학적 왜곡을 탐지하여, 3차원 얼굴 방향과 동공의 기하학적 특성 사이의 관계를 나타낸 학습 데이터를 사용하여 고유한 눈 특징 공간을 구축하였고, 입력된 질의 영상에 대한 3차원 얼굴 방향을 고유한 눈 특징 공간을 사용하여 실시간으로 얼굴 방향을 측정할 수 있었다. 실험결과 카메라에 근접한 실험 대상자들에 대하여 최소 94.67％, 최고 100％의 식별 결과를 나타내었다.