• Advances in materials Research
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• v.1 no.2
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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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• v.4 no.3
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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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• v.3 no.4
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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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• v.11 no.1
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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.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.3 no.1
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• pp.47-52
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• 2010

In this paper, we introduce a new approach for real-time 3D face pose discrimination based on active IR illumination from a monocular view of the camera. Under the IR illumination, the pupils appear bright. We develop algorithms for efficient and robust detection and tracking pupils in real time. Based on the geometric distortions of pupils under different face orientations, an eigen eye feature space is built based on training data that captures the relationship between 3D face orientation and the geometric features of the pupils. The 3D face pose for an input query image is subsequently classified using the eigen eye feature space. From the experiment, we obtained the range of results of discrimination from the subjects which close to the camera are from 94,67%, minimum from 100%, maximum.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.5
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• pp.1134-1138
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• 2008

In this paper, the synthesis of distributed impedance transformers is presented that is essential for power divider design, whereby a broadband power divider is designed. Transfer functions of distributed transformers are synthesized with Chebyshev approximation, and their element values are calculated for various minimum insertion losses(MIL) and ripples. Desired performance of transformers is obtained by optimizing MIL's and ripples of a transfer function. As an application example, a four-way power divider is designed that operates over 2 to 8GHz frequency range. Experimental results are shown to approach the design performance, so transformer design by distributed network synthesis proves to be useful to power divider design.

• Environmental Engineering Research
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• v.19 no.4
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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.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.53 no.5
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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.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.24 no.2
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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.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.3
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• pp.727-732
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• 2004

In this paper, we introduce a new approach for real-time 3D face pose discrimination based on active IR illumination from a monocular view of the camera. Under the IR illumination, the pupils appear bright. We develop algorithms for efficient and robust detection and tracking pupils in real time. Based on the geometric distortions of pupils under different face orientations, an eigen eye feature space is built based on training data that captures the relationship between 3D face orientation and the geometric features of the pupils. The 3D face pose for an input query image is subsequently classified using the eigen eye feature space. From the experiment, we obtained the range of results of discrimination from the subjects which close to the camera are from 94,67％, minimum from 100％, maximum.