• Proceedings of the KIPE Conference
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• 2001.12a
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• pp.11-14
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• 2001

Direct torque control (DTC) scheme provides a very quick torque response without the complex field-orientation block and inner current regulation loop. DTC is known as an appropriate scheme for high power induction motor drives because it can be used at lower switching frequency There are a major drawbacks with the application of DTC schemes it is large current harmonics due to flux drooping in a low speed range. In order to solve the problem, the fuzzy variable switching sector scheme are adopted in this paper. A meaningful contribution of this paper is to propose a simple realization scheme of the fuzzy variable switching sector technique. Experimental results show the effectiveness of this proposition.

• International Journal of Contents
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• v.12 no.4
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• pp.69-75
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• 2016

Adolescent media addiction has emerged as an important social agenda in Korea. However, there has not been enough discussion on the causal structure of media addiction and policy interventions. The objective of this study is to identify and assess the mechanism of the existing and the revised Shutdown policy based on the systems thinking approach. To achieve this purpose, we establish the relationship between media usage, flow, and addiction, and develop a causal loop diagram. Based on the causal loop diagram, we explore the causal structure of two policy scenarios: shutdown policy and deregulation. Our study suggests that policy interventions inducing direct parental control on children's media usage time are ineffective since the time control reduces children's autonomy, which helps alleviate media addiction. Therefore, this study suggests that policy intervention should focus on alleviating addiction itself rather than on controlling media usage time.

• Journal of Microbiology and Biotechnology
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• v.18 no.2
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• pp.392-395
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• 2008

In an attempt to delineate the direct effect of arsenite-induced endothelial dysfunction on nitric oxide (NO) production, confluent bovine aortic endothelial cells (BAEC) were incubated with arsenite, and endothelial NO synthase expression and NO production were measured. Exposure of arsenite decreased NO production for up to 24h. This decrease was accompanied by decreases in cAMP, protein kinase A (PKA) activity, and furthermore, significant reduction of pCREB. In conclusion, this study is the first to demonstrate that exposure of arsenite decreases NO production by a reduction of pCREB and PKA activity that may be mediated by cAMP, leading to endothelial dysfunction.

• Journal of the Korean Society of Safety
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• v.35 no.4
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• pp.1-8
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• 2020

Intensity of accidents associated with dangerous machines and devices are (hereafter items), in general, high compared to other industrial accidents. This study focuses on cause analysis of accidents associated with items that are subject to safety certification. The method is based on automated analysis of abstracts of accidents written in descriptive format. The analysis results indicate that more than 50% of accidents associated with items are caused by technical reasons and nearly 50% of accidents were preventable. More effective prevention of industrial accidents would then be realized by safety certification at the stage of danger generation. Transition from the direct regulation on users to manufacturers is also needed to improve the effectiveness and efficiency of industrial safety system in Korea.

• Proceedings of the KIPE Conference
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• 2012.11a
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• pp.193-194
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• 2012

The bidirectional boost-buck chopper type AC voltage regulator is presented in this paper. The main characteristic of the AC chopper is the fact that it generates an output AC voltage larger or lower than the input AC one, depending of the instantaneous duty-cycle. Boost-buck chopper type AC voltage regulator, derived from the DC chopper modulated method, is a kind of direct AC-AC voltage converter and has many advantages: such as fast response speed, low harmonics and high power factor. It adopts high switching frequency AC chopper technique and can do wide range step less AC voltage regulation.

• Archives of Pharmacal Research
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• v.26 no.3
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• pp.183-191
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• 2003

Nucleic acid therapies represent a direct genetic approach for cancer treatment. Such an approach takes advantage of mechanisms that activate genes known to confer a growth advantage to neoplastic cells. The ability to block the expression of these genes allows exploration of normal growth regulation. Progress in antisense technology has been rapid, and the traditional antisense inhibition of gene expression is now viewed on a genomic scale. This global view has led to a new vision in antisense technology, the elimination of nonspecific and undesirable side effects, and ultimately, the generation of more effective and less toxic nucleic acid medicines. Several antisense oligonucleotides are in clinical trials, are well tolerated, and are potentially active therapeutically. Antisense oligonucleotides are promising molecular medicines for treating human cancer in the near future.

• The Korean Journal of Air & Space Law and Policy
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• v.8
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• pp.297-332
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• 1996

It is well observed in the satellite telecommunication policy of several States that legal constraints imposed upon the service coverage of satellite telecommunication as well as broadcasting are to be relaxed in a progressive way. Major aspects of such policy change lie in the adoption of policy refusing traditional concept of national frontier. In the case of direct broadcasting satellite service, while a debate upon the legal issues regarding the spill-over effect of that service is no more major concern of the States, many multinational enterprises are looking for strategic alliance for regional or global DBS project. On the other hand, an implementation plan for connecting the world through global mobile personal communication satellite system is being pursued by several joint effort of multinational firms. Legal issues arise regarding the regulatory competence of each State, Especially, a controversial issue is concerning the sovereign right well recognized upon the regulation of telecommunication. This study is focusing upon the evolution of such policy change for the purpose of allowing us to expect future develpment of worldwide satellite telecommunication policy environment.

• Journal of Electrical Engineering and information Science
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• v.3 no.1
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• pp.14-20
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• 1998

The resistive shunting for the fine control of a Direct Energy Transfer(DET) systems is fully developed, but the non-resistive shunting using variable size solar array segments is in progress. This paper presents the spacecraft power control through switching of solar array segments, which uses a fully regulated DET power regulation. This method eliminates a dissipative element and removes the associated design limitations which arise from the dissipative elements for radiating cooling in deep space. The switching shunt regulator comprises the switched Solar Array Shunt(SAS) modules that regulate the solar array power. These SAS modules connect/disconnect the solar array segments to/from the bus according to the loading in the main bus without significant variations in the dissipation level. In this paper, twelve segments are used in the shunting. In order to verify the basis of analysis, the computational result of an analytic loop gain is performed.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2006.06a
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• pp.77-78
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• 2006

A mixed method between $H_2\;and\;H_{\infty}$ control are widely applied to systems which has parameter perturbation and uncertain model to obtain an optimal robust controller. Brushless Direct Current (BLDC) motors are widely used for high performance control applications. Conventional PID controller only provides satisfactory performance for set-point regulation. However, with the presence of nonlinearities, uncertainties and perturbations in the system, conventional PID is not sufficient to achieve an optimal robust controller. This paper presents an approach to ease designing a Mixed $H_2/H_{\infty}$ PID controller for controlling speed of Brushless DC motors and the genetic algorithm is used to solve the optimized problems. Numerical results are shown to prove that the performance in the proposed controller is better than that in the optimal PID controller using LQR approach.

• 제어로봇시스템학회:학술대회논문집
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• 1999.10a
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• pp.21-24
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• 1999

There-have been many control strategies for the enact joint position tracking of flexible manipulators, but direct cartesian space tracking control methods an not developed well. In this paper, we propose a PD control method based on the cartesian error in the end point trajectory tracking. the proposed controller is composed of PD control combined with nonlinear saturation term hut has a very simple form. the effect of this term is continuous suppression of vibration which is induced by the coupling of rigid motion. This control works both on the regulation and on the tracking cases. The performance and validity of this control method is shown by simulation examples.