• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.9
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• pp.1597-1604
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• 2016

The speed at which the SRM (Switched Reluctance Motor) makes a transition from chopping control to single pulse operation. (i.e., low speed to high speed operation). It is unsatisfied with performance at all operational regimes. In this paper, the operational performance of SRM can be improved by using current hysteresis control method. This method maintains a generally flat current waveform. At the high speed, the current chopping capability is lost due to the development of the back-EMF. Therefore SRM operates in single pulse mode. By using zero-current switching and zero-voltage switching technique, the stress of power switches can be reduce in chopping mode. When the commutation from one phase winding to another phase winding, the current can be zero as fast as possible in this period because several times negative voltage of DC-source voltage produce in phase winding. This paper is compared to performance based on energy efficient C-dump converter topology and the proposed resonant C-dump converter topology. Simulation and experimental results are presented to verify the effectiveness of the proposed circuit.

• Journal of Electrical Engineering and Technology
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• v.10 no.2
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• pp.574-585
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• 2015

This paper aims to improve the performance of conventional direct torque control (DTC) drives proposed by Takahashi by extending the idea for 5-level inverter. Hybrid cascaded H-bridge topology is used to achieve inverter voltage vector composed of 5-level of voltage. Although DTC is very popular for its simplicity but it suffers from some disadvantages like- high torque ripple and uncontrollable switching frequency. To compensate these shortcomings conventional DTC strategy is modified for five levels voltage source inverter (VSI). Multilevel hysteresis controller for both flux and torque is used. Optimal voltage vector selection from precise lookup table utilizing 12 sector, 9 torque level and 4 flux level is proposed to improve DTC performance. These voltage references are produced utilizing a hybrid cascaded H-bridge multilevel inverter, where inverter each phase can be realized using multiple dc source. Fuel cells, car batteries or ultra-capacitor are normally the choice of required dc source. Simulation results shows that the DTC drive performance is considerably improved in terms of lower torque and flux ripple and less THD. These have been experimentally evaluated and compared with the basic DTC developed by Takahashi.

• Journal of Advanced Marine Engineering and Technology
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• v.13 no.1
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• pp.57-68
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• 1989

This paper treats the analytical and experimental studies on the improvement of commutating circuit for the speed control of DC motor. A simple circuit composed of R, L and C elements is proposed here for switching off power SCR carrying the load current. The real important in this chopper circuit is to determine the reasonable values of commutating circuit constants. In this paper, the reasonable values of the commutating circuit constants are basically determined on a view point of commutating performances in the given circuit model and must satisfy the following conditions. The first, the peak commutating current should be larger than the anticipated maximum load current. The second, the circuit turn-off time (tc) must be longer than the SCR turn-off time (tq). The third, the resistor should be enough large to permit the current to be neglected in the analysis of the commutation circuit, as well as be enough small to permit to charge the capacity voltage (Ec) to the half the value of source voltage (E) before the next communication cycle is initiated. The last, the period of chopping signal must be the least possible multiple of the damping vibration period of commutating circuit. The improved chopper circuit used in the experiment under unloaded condition was composed to meet the reasonable conditions mentioned above, and a successful commuting performance was achieved without failure. Several types of microprocessor having a different value of CPU speed individually have been applied to the experiment under the loaded conditions. Also it shows that the faster the speed of CPU is, the more stable the commutation turns out.

• Korean Journal of Human Ecology
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• v.14 no.5
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• pp.737-747
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• 2005

The purpose of this study was to identify the impact of preschoolers' cognitive ability, parenting behavior, and attachment to their mothers and teachers on delay of gratification of preschoolers. The participants of this study were 116 mothers and their 15 teachers of 3-6 year olds from 2 day-care centers in Seoul. T-test, F-test, Correlation analysis, multiple regression analysis were used for data analysis. First, the result of this study showed that preschoolers' delay of gratification by cognitive ability was significant to only motor intelligence. Second, preschoolers' delay of gratification showed positive correlation with warm-acceptance of parenting. Third, preschoolers' delay of gratification by attachment to their mothers was statistically significant, but it was not significant to their teachers. Fourth, the effect of preschoolers' intelligence, parenting behavior, and attachment to their mothers and teachers on delay of gratification was statistically significant to mothers' warm-acceptance($\beta$=.24, p<.05) and was negatively significant to mothers' permissiveness(.$\beta$=-.35, p<.001).

• Proceedings of the KAIS Fall Conference
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• 2010.11b
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• pp.595-598
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• 2010

본 연구의 목적은 뇌졸중으로 인한 만성 편마비 환자를 대상으로 발에 시지각 자극을 적용하여 균형과 보행에 관한 운동기능에 미치는 효과를 알아보고자 하였다. 6개월 이상 된 편마비 환자 16명이 연구에 참여하였고, 무작위로 실험군(EG) 10명과 대조군(CG) 10명으로 구분하였다. 두 군 모두 기본적인 물리치료를 적용하였고 실험군은 정적균형도구인 Tetrax Multiple System을 이용하여 발목에 감각되먹임 시지각 자극을 매회 30분, 4주간 주 3회 실시하였다. 운동 중재 전과 후의 운동기능에 해당하는 균형(TUG), 보행(DGI)을 측적하여 본 연구의 효과를 비교하였다. 실험군에서 정적 균형, TUG, 그리고 동적 균형지수(DGI) 지수는 중재 전후 통계적으로 유의한 차이를 나타냈고(p<.05), 실험, 대조군간 전후의 변화율에서도 유의한 차이가 나타났다(p<.05). 대조군에서는 DGI 만 중재 전후 통계적으로 유의한 차이가 나타났다. 순수하게 유산소 운동만을 실시하였다. 통계처리 방법으로 전 후 차이를 검증하기 위하여 대응표본 t 검정을 실시하였고 대조군과의 차이 검증을 위하여 독립표본 t 검정을 실시하였다. 모든 통계적 유의수준은 0.05로 하였다. 본 연구에서는 편마비 환자에게 흥미를 촉진하고 운동 기능 회복의 효과를 강화할 수 있는 감각 되먹임이 동반된 시지각 자극을 적용하여 균형 및 보행기능의 향상을 얻을 수 있었고, 차후 연구는 장기간의 추적 관찰 연구가 지속되어야 하고 발목 뿐만 아니라 다른 관절에서의 비교연구가 필요할 것이다.

• Journal of Korean Biological Nursing Science
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• v.17 no.4
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• pp.287-296
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• 2015

Purpose: The purpose of this study was to identify the influence of physical activity and depression on sleep quality among the young-old and old-old community-dwelling elderly. Methods: Participants were 216 community-dwelling older adults in Korea aged 65 or above. Data were collected using structured questionnaires with face-to-face interviews that included demographic and health-related characteristics, International Physical Activity Questionnaires (IPAQ), the Short Form Geriatric Depression Scale (SGDS) and the Pittsburgh Sleep Quality Index (PSQI). A hierarchical multiple regression was conducted to examine whether physical activity and depression would predict sleep quality under other controlled factors. Results: There were differences in demographic and health-related characteristics, physical activity, and depression by age groups, but not in sleep quality. In the young-old elderly, physical activity (${\beta}=-0.22$, p=.043) and depression (${\beta}=0.31$, p=.002) were significantly associated with sleep quality (F=4.46, p=.001, Adjusted $R^2=.16$). In the old-old elderly, physical activity (${\beta}=-0.29$, p=.001) and depression (${\beta}=0.41$, p<.001) were significantly associated with sleep quality (F=10.79, p<.001, Adjusted $R^2=.29$). Conclusion: These finding highlight physical activity and depression as important contributors to sleep quality in both young-old and old-old elderly.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.8
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• pp.81-87
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• 2020

A stable rotational-to-linear motion transformation structure using a driving mechanism with 2 degrees of freedom was developed for an orthogonal mechanism to prevent the interference of each axis in 2D motion. In this mechanism, a step motor was used for precise position control. This structure was developed to maneuver workparts in micro particle blast machining experiments. To determine the real-time performance of micro particle blast machining, the control, input, and output were operated simultaneously and precise position control was implemented, using a timer interrupt with multiple execution codes. The two step motors obtained precise position control by removing backlash with a ball-screw mechanism. The device has menu-type control codes for user-friendliness, and real-time sequence control was simultaneously adopted for user control input.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.249-254
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• 2001

Abstract In this paper, we propose a method of cooperative control based on artifical intelligent system in distributed autonomous robotic system. In general, multi-agent behavior algorithm is simple and effective for small number of robots. And multi-robot behavior control is a simple reactive navigation strategy by combining repulsion from obstacles with attraction to a goal. However when the number of robot goes on increasing, this becomes difficult to be realized because multi-robot behavior algorithm provide on multiple constraints and goals in mobile robot navigation problems. As the solution of above problem, we propose an architecture of fuzzy system for each multi-robot speed control and fuzzy-neural network for obstacle avoidance. Here, we propose an architecture of fuzzy system for each multi-robot speed control and fuzzy-neural network for their direction to avoid obstacle. Our focus is on system of cooperative autonomous robots in environment with obstacle. For simulation, we divide experiment into two method. One method is motor schema-based formation control in previous and the other method is proposed by this paper. Simulation results are given in an obstacle environment and in an dynamic environment.

• Korean Journal of Pharmacognosy
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• v.16 no.1
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• pp.31-35
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• 1985

Intraperitoneal administration of ginseng butanol fraction(GBF) to chronic morphinization in male Sprague-Dawley rats inhibited the development of tolerance to the analgesic effect and hyperthermic action of morphine. Rats were rendered tolerant to morphine by subcutaneous multiple morphine injections for a period of 8 days. The development of tolerance was evidenced by the decreased analgesic response to morphine and inhibition of tolerance by the greater analgesic response. Concomitant administration of morphine with GBF blocked the tolerance to the hyperthermic effect of morphine as evidenced by elevation of body temperature by morphine. Dopamine receptor sensitivity was enhanced in morphine tolerant rats as measured by apomorphine induced in spontaneous motor activity. GBF administration also blocked dopamine receptor supersensitivity induced by chronic morphinization.

• Nuclear Engineering and Technology
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• v.49 no.2
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• pp.327-334
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• 2017

Common-cause failure (CCF) events can significantly impact the availability of safety systems of nuclear power plants. For this reason, the International Common Cause Data Exchange (ICDE) project was initiated by several countries in 1994. Since 1997 it has been operated within the Organisation for Economic Co-operation and Development (OECD)/Nuclear Energy Agency (NEA) framework and has successfully been operated over six consecutive terms (the current term being 2015-2017). The ICDE project allows multiple countries to collaborate and exchange CCF data to enhance the quality of risk analyses, which include CCF modeling. As CCF events are typically rare, most countries do not experience enough CCF events to perform meaningful analyses. Data combined from several countries, however, have yielded sufficient data for more rigorous analyses. The ICDE project has meanwhile published 11 reports on the collection and analysis of CCF events of specific component types (centrifugal pumps, emergency diesel generators, motor operated valves, safety and relief valves, check valves, circuit breakers, level measurement, control rod drive assemblies, and heat exchangers) and two topical reports. This paper presents recent activities and lessons learnt from the data collection and the results of topical analysis on emergency diesel generator CCF impacting entire exposed population.