• Journal of Power System Engineering
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• v.14 no.6
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• pp.96-101
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• 2010

접안을 위해 선박이 안벽으로 접근할 때나, 좁은 항내에서 선박을 조종할 때는 항해 중에서보다 많은 제약이 따른다. 그것은 대형 선박일수도 분 관성력으로 인해 효과적인 제어가 어렵기 때문이다. 그래서 터그보트를 수동적으로 제어하여 선박을 접안시키는 것이 현재로선 가장 일반적이 접안기술이라 할 수 있다. 지능적인 제어기술을 적용하여 자동접안을 시도하려는 연구결과가 보고되고 있으나, 대부분이 auto-pilot 기술에 지나지 않으며 어느 것 하나 안정적인 접안을 위한 접안기술로 볼 수 없다. 이와 같이 터그보트를 이용할 수밖에 없는 현실이라면, 보다 효과적인 터그보트 제어기술을 기반으로 한 접안지원시스템을 개발하는 것이 우선일 것이다. 그래서 본 논문에서는 터그보트의 원격제어를 통해 모선을 효과적이고 안정적으로 접안하는 문제에 대해 고찰하였다. 즉, 터그보트로 조종되는 선박조종시스템에 대한 모델링을 수행하고, 터그보트로부터 발생되는 제어력을 적절히 분배하여 모선을 제어하는 새로운 접안지원시스템을 개발하였다. 시뮬레이션을 통해 제안된 시스템의 유효성을 검증하였다.

• Journal of Power Electronics
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• v.3 no.1
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• pp.62-67
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• 2003

Recently, photovoltaic system has been studied widely as a renewable energy system, because it does not produce environmental pollution and it has infinity energy source from the sun. A study on photovoltaic system has a lot of problems like as reappearance and repetition of some situation in the laboratory experiment for development of MPPT algorithm and islanding detection algorithm. because output characteristics of solar cell are varied by irradiation and surface temperature of solar cell. Therefore, the assistant equipment which emulates the solar cell characteristics which can be controlled arbitrarily by researcher is require to the researchers for reliable experimental data. In this paper, the virtual implement of solar cell (VISC) system is proposed to solve these problems and to achieve reliable experimental result on photovoltaic system. VISC system emulates the solar cell output characteristics, and this system can substitute solar cell in laboratory experiment system. To realize the VISC, mathematical model of solar cell is studied for driving converter and the DC/DC converters are compared in viewpoint of tracking error using computer simulation. Output dynamic characteristic of PV array is varied by irradiation and PWM converter performance is studied using PSIM simulator.

• Journal of Power System Engineering
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• v.10 no.4
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• pp.139-146
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• 2006

In this paper vector code correlation(VCC) method and an algorithm to promote the image processing performance in building an effective measurement system using cameras are described for automatically berthing and controlling the ship equipped with side thrusters. In order to realize automatic ship berthing, it is indispensable that the berthing assistant system on the ship should continuously trace a target in the berth to measure the distance to the target and the ship attitude, such that we can make the ship move to the specified location. The considered system is made up of 4 apparatuses compounded from a CCD camera, a camera direction controller, a popular PC with a built in image processing board and a signal conversion unit connected to parallel port of the PC. The object of this paper is to reduce the image processing time so that the berthing system is able to ensure the safety schedule against risks during approaching to the berth. It could be achieved by composing the vector code image to utilize the gradient of an approximated plane found with the brightness of pixels forming a certain region in an image and verifying the effectiveness on a commonly used PC. From experimental results, it is clear that the proposed method can be applied to the measurement system for automatic ship berthing and has the image processing time of fourfold as compared with the typical template matching method.

• International Journal of Precision Engineering and Manufacturing
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• v.7 no.1
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• pp.18-23
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• 2006

Cutting by a high speed laser cutting machine is one of most effective technologies to improve productivity. This paper has presented the cutting characteristics and optimal cutting conditions in a high speed feeding type laser cutting machine by using Tacuchi method in the design of experiment. An L9(34) orthogonal array is adopted to study the effect of adjustment parameters. The adjustment parameters consist of cutting speed, laser power, laser output duty and assistant gas pressure. The surface roughness of sheet metal is regarded as a quality feature. Analysis of variance is performed in order to evaluate the effect of adjustment parameters on the quality feature of laser cutting process.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.1495-1499
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• 2003

There is some equipment that helps user to exercise and to walk. But almost all equipments require some physical strength of their muscles. So we developed a system that could assist walking action of the people with lower-limb disability. The system called as walking stand adopted the balancing mechanism which assures the stable walking, and the 4 link-based mechanism that had 2 degrees of freedom on each leg. The walking stand uses four motors and has two sets of the special link-structure to simulate the human walking mechanism. With our system, even serious disabled with lower-limb disability may enjoy walking rehabilitation. And by adjusting the power, it can be used as the walking assistant mechanism instead of conventional wheelchairs. Experiments showed that our walking stand is applicable to the rehabilitation and also to the mobile device in our daily life for those people who do not have enough physical ability to walk by themselves.

• Communications for Statistical Applications and Methods
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• v.13 no.3
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• pp.607-619
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• 2006

We consider the problem of testing the existence of change in mean and estimating the change-point when the data are from the normal distribution. A change-point estimator using the likelihood ratio test statistic, Gombay and Horvath (1990) test statistic, and nonparametric change-point estimator using Carlstein (1988) empirical distribution are studied when there exists one change-point in the mean. A power study is done to compare the change test statistics. And a comparison study of change-point estimators for estimation capability is done via simulations with S-plus software.

• Journal of the Korean Statistical Society
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• v.5 no.2
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• pp.91-100
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• 1976

The use of the statistic $t = \sqrt{n} (x-\mu)/S$, where $\bar{X) = \sum X_i/n, \mu = E(X_i), S^2 = \sum(X_i-\bar{X})^2/(n-1)$ in statistical inference is usually done under the assumption of normality of the population. If the population is not normally distributed the tabulated values of student t are no longer valid. The moments of t are obtained as a power series in $1/\sqar{n}$ whose coefficients are functions of the cumulants of X. The cumulants are obtained from the moments in the usual manner. The first eight cumulants of t are given up to terms of order $1/n^3$. The first eight cumulants of t are given up to terms of order $1/n^3$. These results extend those of Geary who gave the first six cumulants of t to order $1/n^2$.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.8
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• pp.1297-1302
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• 2017

Recently, SRMs are used in automobiles for power assistant steering, accessory motion control and traction drives. Especially in the motion control and traction drives, safety and efficiency are of paramount importance. The paper describes the essential elements faced in designing and constructing driving circuits for a switched reluctance motor for automobiles. An important factor in the selection of a motor and a drive for industrial application is the cost. The switched reluctance motor(SRM) is a simple, low-cost, and robust motor suitable for variable-speed as well as servo-type applications. With relatively simple converter and control requirements, the SRM is gaining an increasing attention in the drive industry. This paper presents a modified C-dump converter for Switched Reluctance Motor (SRM) machine application in the cooling system of automobiles. The experiments are performed to verify the capability of applicate control method on 6/4 salient type SRM.

• Journal of the Korean Graphic Arts Communication Society
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• v.16 no.1
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• pp.25-38
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• 1998

The developing agent is the materials which first acts on silver grain and make it into metallic silver by reducing reaction. There are several types in developing agent, and according to Lumiere-Andresen principle, substitution product which has amino or hydroxyl group in benzen nucleus has a developing power, but all reduing substances are not in used. In the developing effect, not only the role of developing agent but also that of assistant materials are important. But in this work, we have studied effect, change by lith developing agent which require high contrast image. We made an developing experiment after having manufactured developing solution used hydroquinone and another developing agents like chlorohydroquinone, pyrocatechol and pyrogallol as developing agent. And we added that did in addition of diethanolamine and ascorbic acid, and then we examined the possibility of use.

• Journal of Korea Multimedia Society
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• v.7 no.12
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• pp.1754-1764
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• 2004

Lately mobile handheld devices such as Personal Digital Assistant (PDA) and cellular phones are getting more popular for personal web surfing. However, today most mobile handheld devices have relatively poor web browsing capability due to their low performance so their users have to suffer longer communication latency than those of desktop Personal Computers (PCs). In this paper, we propose an effective pre-refresh mechanism for embedded web browser of mobile handheld devices to reduce this problem. The proposed mechanism uses the idle time to pre-refresh the expired web objects in an embedded web browser's cache memory. It increases the utilization of Central Processing Unit (CPU) power and network bandwidth during the idle time and consequently reduces the client's latency and web browsing cost. An experiment was done using a simulator designed by us to evaluate the efficacy of the proposed mechanism. The experiment result demonstrates that it has a good performance to make web surfing faster.