• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2003년도 International Meeting on Information Display
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• pp.694-697
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• 2003

In applying LCD to TV application, one of the most significant factors to be improved is image sticking on the moving picture. LCD is different from CRT in the sense that it's continuous passive device, which holds images in entire frame period, while impulse type device generate image in very short time. To reduce image sticking problem related to hold type display mode, we made an experiment to drive LCD like CRT. We made articulate images by turn on-off backlight, and we realized the ratio of Back Light on-off time by adjusting between on time and off time for video signal input during 1 frame (16.7ms). Conventional CCFL (cold cathode fluorescent lamp) cannot follow fast on-off speed, so we evaluated new fluorescent substances of light source to improve residual light characteristic of CCFL. We realized articulate image generation similar to CRT by blinking drive. As a result, reduced image sticking phenomenon was validated by naked eye and response time measurement.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 한국자동제어학술회의논문집(국내학술편); 포항공과대학교, 포항; 24-26 Oct. 1996
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• pp.40-43
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• 1996

An off-line programming, OLP, system is widely used in automation fines. To help an on-line robot system to carry out desirable tasks planned by the off-line simulation, an approach to the real-time communication is presented. The OLP system developed consists of a software, a host computer(PC), a SCARA robot body, four servo drivers, and four independent joint controllers. This study focuses on the software where real-time communication is included. The software, can be used in teaching, trajectory planning, real-time running, and performance evaluation. The evaluation of different control algorithms is one of the merits of the software. The software can give servo commands for task running. A comparison of generated and corresponding actual trajectories provides the evaluation of task performance. The safety, of the OLP system is ensured by alarming malfuntions of the system. The OLP system developed can reduce the teaching time and increase the user's convenience.

• 한국운동역학회지
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• 제13권3호
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• pp.99-116
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• 2003

The purpose of this study was to kinematics factors on during round-off at end of beam-salto backward stretched with step-out to cross on balance beam. Four elite female gymnastics players participated as subject of this study. The methods of this study was analyzed using three dimentional analysis. The results and conclusion of this paper is obtained as follows ; 1. The phase of time was the most short time in board touch down phase and board take-off phase. Also, it was shown a more long time in total time compared to previous study. 2. The horizontal displacement of each phase was shown the most high levels in balance beam landing. The vertical displacement was display a non-linearity increase in board take-of phase, and it was shown the most high levels in vertical displacement during landing of balance beam. 3. The horizontal velocity of each phase was shown the most high levels in board touch down, and it was display a gradually decreased levels because flight during board take-of. The resultant velocity of CG on each phase was shown the most high levels in board touch down and board take-off. 4. The angle of hip joint was shown the most high levels as performed a motion in extension state during board take-off, and the angle of knee joint was display a increased levels because of flight cause body extension in board take-off. Also the angle of ankle joint was shown a increasing levels during board take-off. Considering to this results, it is suggest that the change of kinematics factors in board touch down and board take-off is key role on the effective board control.

• 대한기계학회논문집
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• 제19권3호
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• pp.868-876
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• 1995

This study deals with a position control of an electro-hydraulic servo system which consist of cylinder and high speed on-off valves operated by microcomputer. The merits of PWM control of hydraulic equipment are the robustness of the high spee on-off valve, its low price and the direct control without D/A converter. In the PWM control of high speed on-off valve, the time lag and switching time existing between the input and output signals of valve are considered as demerit points. To get analytical results, the effects of these demerits have to be clarified in detail. The object of this study is to propose a mathematical model for the behavior of high speed on-off valve and to get analytical results of this system. The dynamic characteristics of this system is examined by digital computer simulation analytically and compared with experimental results to varify the proposed mathematical model.

• 대한전기학회논문지:전력기술부문A
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• 제55권1호
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• pp.13-17
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• 2006

In this paper, the RCF(Resistive Companion Form) analysis method which is used to analyze small signal stability problems of non-continuous systems including switching devices. The RCF analysis method is mathematically rigorous and computes eigenvalue of the system periodic transition matrix based on discrete system analysis method. As an effect of switching operations, the eigenvalues of the systems are changed and newly unstable oscillation modes may be occurred. As an illustrating example, the oscillation modes of the system with different switching time intervals are computed exactly by the RCF analysis method and the results show that ON/OFF time intervals of switching equipments are important factors to make the system stable or unstable. This result shows that the RCF analysis method is very powerful to analyze small signal stability problems of power systems including switching devices such as FACTS equipments.

• 한국건축시공학회지
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• 제8권6호
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• pp.91-98
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• 2008

It is time-consuming and difficulty to solve the time-cost trade-off problems, as there are trade-offs between time and cost to complete the activities in construction projects and this problems do not have unique solutions. Typically, heuristic methods, mathematical models and GA models has been used to solve this problems. As heuristic methods and mathematical models are have weakness in solving the time-cost trade-off problems, GA based model has been studied widely in recent. This paper suggests the time-cost trade-off optimization algorithm using particle swarm optimization. The traditional particle swarm optimization model is modified to generate optimal tradeoffs among construction time and cost efficiently. An application example is analyzed to illustrate the use of the suggested algorithm and demonstrate its capabilities in generating optimal tradeoffs among construction time and cost. Future applications of the model are suggested in the conclusion.

• 정보처리학회논문지:컴퓨터 및 통신 시스템
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• 제2권7호
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• pp.283-292
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• 2013

기존 서버 클러스터에서는 고성능을 보장하기 위해, 실시간 요청 수량에 관계없이 모든 서버를 항상 On 한다. 그 방법에서는 QoS를 보장하지만 일부 서버들이 Idle할 때 서버 전력을 낭비하게 된다. 서버들이 소모하는 에너지를 절약하기 위해, 서버가 필요하지 않을 경우 해당 서버의 전력을 Off 하게 하는 서버 전력 제어 방법이 제안되었다. 서버 전력 제어 방법은 서버의 Power가 실제로 어느 시점에 Off 되느냐에 따라 정적인 방법과 동적인 방법이 있다. 정적인 방법에서는 특정 서버가 Off 하기로 결정된 다음 일정 시간 지연 후 그 서버가 Off 된다. 동적인 방법에서는 그 서버에서 수행중인 모든 서비스가 종료된 다음에 해당 서버가 Off 된다. 이는 가변 시간 지연 후 서버가 Off 되는 방법에 해당된다. 정적 종료방식은 단점이 있다. 반복 실험을 통해 수작업으로 최적의 시간 지연을 알아내기 위해서는 많은 시간이 소요된다. 본 논문에서는 정적 종료 방식의 단점을 극복하는 동적 종료 방식을 제안한다. 제안된 방식은 최적의 지연 시간으로 자동적으로 접근하므로 좋은 전력 절약을 하면서 QoS를 보장하는 것을 가능하게 해준다. 30대의 PC 클러스터를 이용하여 실험이 수행되었다. 실험결과는 제안하는 동적 종료 방법이 기존의 정적 종료 방법과 비교할 때 에너지 절감측면에서는 비슷하지만 QoS 측면에서 우수함을 보여준다.

• Structural Engineering and Mechanics
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• 제71권2호
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• pp.139-151
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• 2019

In a project schedule, it is possible to reduce the time required to complete a project by allocating extra resources for critical activities. However, accelerating a project causes additional expense. This issue is addressed by finding optimal set of time-cost alternatives and is known as the time-cost trade-off problem in the literature. The aim of this study is to identify the optimal set of time-cost alternatives using a multiobjective teaching-learning-based optimization (TLBO) algorithm integrated with the non-dominated sorting concept and is applied to successfully optimize the projects ranging from a small to medium large projects. Numerical simulations indicate that the utilized model searches and identifies optimal / near optimal trade-offs between project time and cost in construction engineering and management. Therefore, it is concluded that the developed TLBO-based multiobjective approach offers satisfactorily solutions for time-cost trade-off optimization problems.

• Journal of Advanced Marine Engineering and Technology
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• 제15권1호
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• pp.85-95
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• 1991

All physical systems are nonlinear to some degree. The examples are relay, backlash, deadzone, saturation element and so on. In the linear control system design, it is useful method to restrict the nonlinearity to the linearity of system over the operation range. It is worth noting that nonlinearities may be intentionally introduced in to a system. A simple of an intentional non-linearity is the Bang-Bang controller which uses the On-Off relay. In this paper, an angular position servosystem made of a DC servomotor controlled by a microcomputer is discribed. Authors use two methods in the design of controller. The one is linear controller designed by the optimal feedback control theory only and the other is nonlinear controller designed by On-Off relay with optimal feedback control theory. To do the real time control, the controller is designed by using 16bit personal computer and A/D.D/A converter(12bit) is used in order to convert the signal. According to this way, the results from real time control are as follows. 2) Under the On-Off controller with hysterisis the influence of disturbance is considerably smaller than the linerar controller. 3) An increase in the sampling period has a destabilizing effect. 4)In the controller performance, the response time of the On-Off controller is longer than that of the linear controller. To close, we note that the On-Off controller with hysterisis is more attractive than the linear controller in the presence of the input limit.

• Journal of Magnetics
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• 제17권4호
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• pp.298-301
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• 2012

In order to know the effect of surface irregularity in the detection of local wall thinning of pipeline using pulsed eddy current (PEC), the lift-off effects on PEC signal have been investigated. Three kinds of parameters in the PEC signal, which is "peak amplitude", "time to peak amplitude" and "time to zero crossing" are analyzed to separate the lift-off effects in the PEC signal. The distance from sensor to the bottom of sample which is the total thickness of combined insulator and sample is kept constant. The magnitude of the differential peak amplitude is increased with increasing sample thickness, the time to peak amplitude is increased with increasing the sample thickness. To determine the effect of lift-off, a number of balanced transient responses combining wall thinning locations and lift-off distances were plotted.