• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 추계학술대회 논문집 전력기술부문
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• pp.215-217
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• 2002

본 논문에서는 2004, 2007년 한전 계통에 대해 상정사고 시 수도권 지역에서의 순동 무효전력원 필요성, 확보 방안을 제시하였다. 수도권 지역에서 순동 무효전력원의 필요성을 제시하였고, 수도권 지역의 모든 354KV 이상 송전선로 1루트 상정사고 리스트를 작성하여 전압 안정도 측면에서 문제가 발생하는 상정사고를 선정하였다. 선정된 상정사고에 PSS/E를 사용한 QV곡선을 이용하여 순동 무효전력 확보방안을 제시하였다.

• 한국정보통신설비학회:학술대회논문집
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• 한국정보통신설비학회 2008년도 정보통신설비 학술대회
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• pp.559-562
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• 2008

In this paper we propose a lock-in detection method for portable sensor systems and demonstrate with the portable detection module that has high sensitivity and robustness against the noise. The simple portable sensor module is manufactured using MCU(Micro Contorl Unit), OPAMP, MOSFET and a pair of infrared sensor. Manufactured sensor module is testified in the noisy environment caused by an external light and an white noise source. Without any type of band pass filters, we recover a signal of 33 $mV_{p-p}$ in 80 $mV_{p-p}$ white noise and get the DR(Dynamic Reserve) of 14 dB.

• 복식
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• 제56권7호
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• pp.148-162
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• 2006

The purpose of this study is to examine the concept of convergence which is one of the trendy issues as a new digital paradigm of Integrative thinking in 21st century, to analyze the plastic feature and internal meaning of convergence expressed in fashion design, and to grasp the cultural symbolism through this aesthetic analysis. Because there have been considerable discussions on convergence, centering on industrial product area associated with media, I will proceed my study on the basis of them. For this, the documentary study and practical case study have been executed. This study will be helpful to find a direction of future fashion design trend. Convergence in digital stage can be defined as a phenomenon which different functions of product move towards one direction for greater efficiency, and not only as a technical integration between functions of product, but also an extension of area. Convergence can be classified by their use as (1) convergence for convenient daily life (2) convergence with intelligent scientific technology (3) convergence for entertainment on the basis of sensual experience. The plasticity of convergence designs feature as a open dynamic structure which potentiate transformation and their internal meaning can be inquired such qualities as integrative multiplicity, efficiency, mobility, intelligence. Specially convergence fashion design has protection qualify resulting from wearability on body. Ultimately convergence fashion design as a future digital paradigm can be thought as both eco-friendly design and human-centered design from positive technology-based viewpoint, because it is easy to transform according to our environment, convenient to reserve, and efficient to enhance spatial usibility.

• 한국경영과학회지
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• 제23권2호
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• pp.187-200
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• 1998

This paper presents an original approach for solving short-term power scheduling in extended power system with two fuels in a unit and a limited fuel using Lagrangian relaxations. The underlying model incorporates the full set of costs and constraints including setup, production, ramping, and operational status, and takes the form of a mixed integer nonlinear control problem. Moreover, the mathematical model developed includes two fuels in a unit and a limited fuel, regulation reserve requirements of prespecified group of units. Lagrangian relaxation is used to disaggregate the model by generator into separate subproblems which are then solved with a nested dynamic program including empirical knowledges. The strength of the methodology lies partially in its ability to construct good feasible solutions from information provided by the dual. Thus, the need for branch-and-bound is eliminated. In addition, the inclusion of two fuels in a unit and a limited fuel provides new insight into the limitations of current techniques. Computational experience with the proposed algorithm indicates that Problems containing up to 23 units including 8 unit used two fuels and 24 time periods can be readily solved in reasonable times. Duality gaps of less than 4％ were achieved.

• 전기학회논문지
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• 제56권10호
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• pp.1731-1737
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• 2007

The Korea electricity wholesale market is operated under the cost-based-pool system and the government regulation to the new generation capacities in order to insure the resource adequacy. The goal of government's regulation is the electricity market stability by attracting proper generation investment while keeping the reliability of system. Generation companies must mandatory observe that government plan by now. But if the restructuring is to be complete, generation companies should not bear any obligation to invest unless their profitability is guaranteed. Namely the investors' behavior will be affected by the market prices. In this paper, the system dynamics model for Korea wholesale electricity market to examine whether competitive market can help to stabilize is developed and analyzes the investors behavior. The simulation results show that market controlled by government will be operated stable without resulting in price spike but there is no lower price because of maintaining the reasonable reserve margin. However, if the competition is introduced and the new investment is determined by the investor's decision without government intervention, the benefits from lower wholesale price are expected. Nevertheless, the volatility in the wholesale market increases, which increases the investment risks.

• 조명전기설비학회논문지
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• 제28권12호
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• pp.108-115
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• 2014

Recently, Uninterruptible power supply(UPS) is spotlighted from concern about black out, due to reserve power problem caused by increased power consumption. When fault occurs on the grid, UPS system supplies power to loads instead of the grid. Also, it is an advantage of possible operation as Energy storage system(ESS). Bi-directional power control of AC/DC Pulse width modulation(PWM) converter is essential for grid-connected UPS system. And, mode transfer control has to be performed considering phase and dynamic characteristic under grid condition. In this paper, control of mode transfer and bi-directional power control of AC/DC PWM converter is proposed for UPS system. Also, it is verified by simulation and experimental results.

• International Journal of Fluid Machinery and Systems
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• 제3권4호
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• pp.352-359
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• 2010

In recent years, the market has shown increasing interest in pump-turbines. The prompt availability of pumped storage plants and the benefits to the power system achieved by peak lopping, providing reserve capacity, and rapid response in frequency control are providing a growing advantage. In this context, there is a need to develop pumpturbines that can reliably withstand dynamic operation modes, fast changes of discharge rate by adjusting the variable diffuser vanes, as well as fast changes from pumping to turbine operation. In the first part of the present study, various flow patterns linked to operation of a pump-turbine system are discussed. In this context, pump and turbine modes are presented separately and different load cases are shown in each operating mode. In order to create modern, competitive pump-turbine designs, this study further explains what design challenges should be considered in defining the geometry of a pump-turbine impeller. The second part of the paper describes an innovative, staggered approach to impeller development, applied to a low head pump-turbine project. The first level of the process consists of optimization strategies based on evolutionary algorithms together with 3D in-viscid flow analysis. In the next stage, the hydraulic behavior of both pump mode and turbine mode is evaluated by solving the full 3D Navier-Stokes equations in combination with a robust turbulence model. Finally, the progress in hydraulic design is demonstrated by model test results that show a significant improvement in hydraulic performance compared to an existing reference design.

• 대한전기학회논문지:전력기술부문A
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• 제48권3호
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• pp.234-240
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• 1999

This paper presents a new approach for large-scale generator maintenance scheduling optimizations. The generator preventive maintenance scheduling problems are typical discrete dynamic n-dimensional vector optimization ones with several inequality constraints. The considered objective function to be minimized a subset of{{{{ { R}^{n } }}}} space is the variance (i.g., second-order momentum) of operating reserve margin to levelize risk or reliability during a year. By its nature of the objective function, the optimal solution can only be obtained by enumerating all combinatorial states of each variable, a task which leads to computational explosion in real-world maintenance scheduling problems. This paper proposes a new priority search mechanism based on each generator's discrete sensitivity value which was analytically developed in this study. Unlike the conventional capacity-based priority search, it can prevent the local optimal trap to some extents since it changes dynamically the search tree in each iteration. The proposed method have been applied to two test systems (i.g., one is a sample system with 10 generators and the other is a real-world lage scale power system with 280 generators), and the results anre compared with those of the conventional capacith-based search method and combinatorial optimization method to show the efficiency and effectiveness of the algorithm.

• Structural Engineering and Mechanics
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• 제46권4호
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• pp.487-504
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• 2013

In the present work a new friction device, with a set of single or double rotational friction flanges and a link element, is described and tested. The mechanism may be applied for the strengthening of existing r/c or steel buildings as well as in new constructed buildings. The device has selectable variable behavior in different levels of displacement and an interlock mechanism that is provided by the link element. The link element may be designed to lock at preselected level of displacement, offering in this way an extra safety reserve against strong earthquakes. A summary of the existing literature about other similar mechanisms is initially presented in this paper. The proposed mechanism is presented and described in details. Laboratory experiments are presented in detail and the resulted response that proves the efficiency of the mechanism at selectable levels of strength capacity is discussed. Drawings of the mechanism attached to a r/c frame with connection details are also included. Finally a dynamic analysis of two r/c frames, with and without the proposed mechanism attached, is performed and the resulted response is given. The main conclusion is that the proposed mechanism is a cheap and efficient devise for the improvement of the performance of new or existing framed buildings to seismic loads.

• Journal of Forest and Environmental Science
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• 제39권4호
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• pp.203-212
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• 2023

Directional felling is a felling method practised by the Forestry Department in Peninsular Malaysia as prescribed in Field Work Manual (1997) for Selective Management Systems (SMS) in forest harvesting. Determining the direction of tree felling in Peninsular Malaysia is conducted during the pre-felling inventory 1 to 2 years before the felling operation. This study aimed to predict and analyze the direction of tree felling using the vector-based path distance back link method in Geographic Information Systems (GIS) and compare it with the felling direction observed on the ground. The study area is at Balah Forest Reserve, Kelantan, Peninsular Malaysia. A Path Distance Back Link (spatial analyst) function in ArcGIS Pro 3.0 was used in predicting tree felling direction. Meanwhile, a binary classification was used to compare the felling direction estimated using GIS and the tree felling direction observed on the ground. Results revealed that 61.3% of 31 trees predicted using the vector-based projection method were similar to the felling direction observed on the ground. It is important to note that dynamic changes of natural constraints might occur in the middle of tree felling operation, such as weather problems, wind speed, and unpredicted tree falling direction.