• 대한한방내과학회지
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• 제21권2호
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• pp.275-281
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• 2000

Object : This study was carried out to examine the effect of Bupleuri Radix on experimental cholestasis, and make clear apart of this mechanism. Methods : Two models of common bile duct ligation group and taurocholate load group after common bile duct ligation were induced, and Bupleuri Radix extract was taken orally for 14 days. In the 1, 2, 4, 7 and 14 days after treatment, the mitochondrial and microsomal monoamine oxidase(MAO) A and B activities in liver were measured. Results : The mitochondrial MAO A and B activities increased in both Blupleuri Radix treated group after common bile duct ligation and Blupleuri Radix treated group after taurocholate load and common bile duct ligation. MAO A increased in Blupleuri Radix treated group after taurocholate load and common bile duct ligation, and MAO B increased in Blupleuri Radix treated group after common bile duct ligation. The microsomal MAO A activities increased in both Blupleuri Radix treated group after common bile duct ligation and Blupleuri Radix treated group after taurocholate load and common bile duct ligation. Conclusion : According to the result, it is consider that Blupleuri Radix not only improves cholestatis in liver, but also decreases a genetic synthesis of taurocholic acid.

• 대한한의학회지
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• 제21권3호
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• pp.68-76
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• 2000

Object : This study was earned out to examine the effect of Bupleuri Radix on experimental cholestasis, and make clear a part of this mechanism. Methods : Two models of common bile duct ligation group and taurocholate load group after common bile duct ligation were induced, and Bupleuri Radix extract was taken orally for 14 days. In the 1, 2, 4, 7 and l4days after treatment, cytosolic, mitochondrial and microsomal catechol-O-methyltransferase(COMT) activities in liver were measured. Results : The activities of cytosolic, mitochondrial and microsomal COMT increased in the Blupleuri Radix treated group after common bile duct ligation and after taurocholate load and common bile duct ligation. The activities of cytosolic and mitochondrial COMT increased particularly in Blupleuri Radix treated group after taurocholate load and common bile duct ligation. Conclusions : According to the result, it is considered that Blupleuri Radix not only improves cholestatis in liver, but also decreases a genetic synthesis of taurocholic acid.

• Safety and Health at Work
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• 제11권3호
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• pp.335-346
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• 2020

Background: Nursing service is a nonroutine work with an excessive physical load and diverse tasks. This study derived representative common tasks based on the frequently occurring tasks with a high physical load in the nursing workers' daily work and developed indicators to evaluate the work risk by reflecting the characteristics of nonroutine work. Methods: Common tasks were classified through the following stages: literature review, first focus group interview (FGI) with experts, first classification of common tasks, second FGI with hospital health managers, a survey of nursing service workers, and the final classification of common tasks for each task type. To develop an objective risk index for physical load assessment, we investigated the frequency and duration of the derived common tasks via survey. Results: Nursing common tasks were categorized into six task types and 56 subtasks. To evaluate the risks of various tasks in nonroutine works, three frequencies and three working time levels were defined by examining the task frequency and working hours. Exposure time was defined to reflect the characteristics of a nonroutine job. The final risk assessment was the product of the exposure time level and job intensity level. From this, four risk action levels were derived. Conclusion: This study has the advantage of solving the problem of focusing on some tasks in evaluating the physical load. It was meaningful in that a new risk assessment index based on exposure time was proposed based on the development of an evaluation scale for frequency and time by reflecting the characteristics of nonroutine work.

• 한국가스학회지
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• 제20권4호
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• pp.58-64
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• 2016

차량에 사용되는 주엔진은 부하영역 전체에서 효율을 증가시키기 위해 커먼레일 디젤엔진을 사용하고 있다. 그러나, 발전기용 엔진은 아직도 기계적 구성엔진으로 캠으로 구동되는 연료분사밸브가 사용되어지고 있다. 또한, 발전기용 엔진 대부분은 50%이하의 부분부하가 적용되고 있다. 따라서, 전부하에 세팅된 차량용 디젤엔진을 부분부하에서 효율적인 운전을 하기 위해서는 연료분사시기 재조정이 필요하다. 본 연구에서는 시설물에 사용되는 엔진발전기의 운용특성을 파악하여 연료분사시기를 재조정함으로서 부분부하 연료소비율을 개선시킨 결과를 연구하고자 한다.

• Journal of Power Electronics
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• 제17권3호
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• pp.641-652
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• 2017

This paper proposes a cost-effective topology to drive a three-phase open-end load based on a five-leg indirect matrix converter (IMC) and a space vector modulation (SVM) method. By sharing an inverter leg with two load terminals, the proposed topology can reduce the number of power switches when compared to topologies based on a direct matrix converter or a six-leg IMC. The new SVM method uses only the active vectors that do not produce common-mode voltage (CMV), which results in zero CMV across the load phase and significantly reduces the peak value of the CMV at the load terminal. Furthermore, the proposed drive system can increase the voltage transfer ratio up to 1.5 and provide a superior performance in terms of an output line-to-line voltage with a three-level pulse-width modulation waveform. Simulation and experimental results are given to verify the effectiveness of the proposed topology and the new SVM method.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.740-741
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• 2007

This paper analyses the transient state of underground distribution system against single line to ground fault in underground transmission systems, when underground transmission systems and distribution systems are made of common grounding. Underground transmission systems and distribution systems are modeled by EMTP/ATPDraw. Simulation is carried out considering variation of parameters such as value of common grounding, balance load and unbalance load.

• Journal of Power Electronics
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• 제15권3호
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• pp.712-720
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• 2015

A model predictive current control (MPCC) method that does not employ a cost function is proposed. The MPCC method can decrease common-mode voltages in loads fed by three-phase voltage-source inverters. Only non-zero-voltage vectors are considered as finite control elements to regulate load currents and decrease common-mode voltages. Furthermore, the three-phase future reference voltage vector is calculated on the basis of an inverse dynamics model, and the location of the one-step future voltage vector is determined at every sampling period. Given this location, a non-zero optimal future voltage vector is directly determined without repeatedly calculating the cost values obtained by each voltage vector through a cost function. Without utilizing the zero-voltage vectors, the proposed MPCC method can restrict the common-mode voltage within ± V_dc/6, whereas the common-mode voltages of the conventional MPCC method vary within ± V_dc/2. The performance of the proposed method with the reduced common-mode voltage and no cost function is evaluated in terms of the total harmonic distortions and current errors of the load currents. Simulation and experimental results are presented to verify the effectiveness of the proposed method operated without a cost function, which can reduce the common-mode voltage.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제51권6호
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• pp.298-306
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• 2002

We performed an safety evaluation on constructing of a common grounding system for electrical railway in view of its efficacy and technical fit. In order to compare the conventional grounding method, which has been individually conducted, with the common grounding with all ground wires connected in common to the counterpoise buried below the surface of the earth in parallel with rail, we set up scenarios with several cases of fault and load conditions in Chungbuk railway sections with the common grounding system. Based on models for railway conductors including the grounded system, line Parameters of railway power system are computed. The circuit model for power system with up and down lines, auto-transformers and railway substations is used to compute impedances of counterpoise and substation ground net. For each scenario with faults and operation conditions of railway, the induced potentials on signal and communication lines are also computed. It is shown that the common grounding for Chungbuk railway is superior experimentally to the conventional method in three respects: (1) the lower rail potentials during operation of railway in line, (2) the lower rail potentials for short-circuit faults between catenary and rail, and (3) the lower stress voltages on signal and communication lines for short-circuit or ground faults. The analysis results confirm that the grounding system for electric railway is required to be built by the common grounding and be evaluated on its safety in design.

• 한국철도학회논문집
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• 제13권3호
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• pp.290-297
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• 2010

현재 국내 표준열차하중은 일반철도와 고속철도로 나뉘어져 있으며, 일반철도의 경우 미국의 표준열차하중 혹은 과거 일본의 K하중을 기반으로 하는 L22, 고속철도의 경우 Eurocode의 LM71를 기반으로 하는 HL25 하중 모델을 적용하고 있다. 표준열차하중의 구조물 설계의 출발점이 되는 것으로 매우 중요한데 반하여 국내에서는 표준열차하중 개발과 관련한 연구가 진행된 바가 전무한 상황이다. 반면, 유럽과 일본에서는 선진 설계법 도입과 병행하여 합리적 표준열차하중에 대한 연구가 지속적으로 수행되고 있다. 최근 유럽에서는 새로운 표준열차하중인 LM2000 모델 개발 시 결정론적, 확률론적, 비용효과 분석 등 종합적이고 합리적인 방법에 의해 표준열차하중을 개발한 사례가 있다. 본 논문에서는 국내 표준열차하중 개발을 위한 단계적 접근 중 하나로서 결정론적 분석에 의한 표준열차하중 결정 과정을 분석하였다. 현재 국내 운행 중인 실열차를 기반으로 교량 단면력에 대한 여유도를 평가하여 합리적인 표준열차하중을 제시하고자 하였다.

• Journal of Power Electronics
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• 제18권3호
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• pp.923-930
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• 2018

Based on the application of an integrated dynamic brake (IDB) system that uses a PWM inverter fed-AC motor drive to operate the piston, a new active zero state PWM (AZSPWM) is proposed to improve the stability and reliability of the IDB system by suppressing the conducted electro-magnetic interference (EMI) noise under a wide range of load torque. The new AZSPWM reduces common-mode voltage (CMV) by one-third when compared to that of the conventional space vector PWM (CSVPWM). Although this method slightly increases the output current ripple by reducing the CMV, like the CSVPWM, it can be used within the full range of the load torque. Further, unlike other reduced common-mode voltage (RCMV) PWMs, it does not increase the switching power loss. A theoretical analysis is presented and experiments are performed to demonstrate the effectiveness of this method.