• 전력전자학회:학술대회논문집
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• 전력전자학회 2004년도 전력전자학술대회 논문집(2)
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• pp.515-518
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• 2004

Increasing of the nonlinear power electronics equipments, power conditioning systems have been researched and developed for many years to compensate the harmonic disturbances and the reactive power. The main function of power conditioning systems is to reduce harmonic distortions, since extensive surveys quantify the problems associated with electric networks having non-linear loads. The main function of power conditioner compensates the current instead of the voltage. Therefore the inverter used in power conditioner is mostly the current controlled type. In this paper, we propose the power conditioner using photovoltaic system, which is operated by the PRT(Polarized Ramp Time) current control algorithm. The proposed system could also achieve Demand Side Management's function and Uninterruptible Power Supply's function simultaneously. To verify the proposed current controlled inverter for improved quality of the grid, the detail simulation and experiment results indicate that operation PCS, DSM and UPS can be achieved.

• 전력전자학회논문지
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• 제7권4호
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• pp.359-365
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• 2002

최근 상업용 빌딩, 주거용 빌딩 및 공장등의 저전압 3상 4선식 배전계통에서 PC, UPS, 정류기기, 조명장치 및 사무용기기등 비선형 부하의 사용이 증가하고 있으며, 이로 인한 과도한 중성선 전류는 중성선의 고장, 변압기의 과열 및 중성선과 접지사이의 전압강하등 심각한 문제를 야기시키고 있다. 본 논문에서는 3상 4선식 배전계통에서 중성선 전류 제거를 위한 새로운 저감된 용량의 능동전력필터를 제안한다. 제안한 방식은 제어가 간단하고 불평형에 기인하는 기본파 전류만이 인버터 스위치로 흐를 수 있기 때문에 인버터의 VA 정격이 작아진다. 제안한 시스템은 실험에 의하여 그 타당성을 입증한다.

• 전기기술인
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• 제228권8호
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• pp.43-48
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• 2001

우리나라에서는 3 Θ 4w 배전방식을 채택하고 있는데 최근에는 컴퓨터 등 OA 기기 사용증가로 이때 발생하는 영상분 고조파에 의하여 중성선에 상전류 보다 큰 전류가 흐르게 된다. 고조파에 의한 중전선 과전류는 케이블, 변압기, 과열소손, 변압기, 발전기 출력저하, 역률저하, 전력손실 증가, ELB, MCCB 오동작, 유도장해, 중성선 대지전위 상승 등 심각한 장애를 일으키고 있다.

• Journal of international Conference on Electrical Machines and Systems
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• 제1권3호
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• pp.372-378
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• 2012

This paper deals with a 3-phase voltage disturbance generator for a performance test of custom power devices such as dynamic voltage restorers (DVR), dynamic uninterruptable power supplies (UPS), etc. The operating principle of the proposed circuit is described in each mode of voltage sag, swell, outage, and unbalance. The main components of the proposed disturbance generator are silicone controlled rectifier (SCR) thyristors, variable autotransformers, and transformers. Therefore, the disturbance generator can be implemented with a considerably low cost compared to the conventional pulse width modified (PWM) inverter and converter type generators. Furthermore, it has good features of high reliability with simple structure, high efficiency caused by no PWM switching of the SCR thyristors, and easy control with a wide variation range. To verify the validity of the proposed scheme, simulations and experiments are carried out.

• 전력전자학회논문지
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• 제17권1호
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• pp.27-33
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• 2012

Internet Data Centers (IDC), as essential facilities for modern IT industry, typically have scores of MW of concentrated electric loads. Uninterruptible Power Supplies (UPS) are necessary for the power feed system of IDCs because of stable power requirement. Thus, conventional AC power feed systems of IDCs have three cascaded power conversion stages such as (AC-DC), (DC-AC), and (AC-DC), which results in very low conversion efficiency. On the contrary, DC power feed systems need just a single power conversion stage (AC-DC) supplying AC mains power to DC server loads, which gives comparatively high conversion efficiency and reliability. This paper compares the efficiencies between 220V AC power feed system and 300V DC power feed system on equal load conditions which were established in Mok-Dong IDC of Korea Telecom company (KT). Experimental results show that the total operation efficiency of the 300V DC power feed system is around 15% higher than that of the 220V AC power feed system.

• Biomolecules & Therapeutics
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• 제19권4호
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• pp.371-389
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• 2011

A new strategy for cancer therapy has emerged during the past decade based on molecular targets that are less likely to be essential in all cells in the body, therefore confer a wider therapeutic window than traditional cytotoxic drugs which mechanism of action is to inhibit essential cellular functions. Exceptional heterogeneity and adaptability of cancer impose significant challenges in oncology drug discovery, and the concept of complex tumor biology has led the framework of developing many anticancer therapeutics. Protein kinases are the most pursued targets in oncology drug discovery. To date, 12 small molecule kinase inhibitors have been approved by US Food and Drug Administration, and many more are in clinical development. With demonstrated clinical efficacy of bortezomib, ubiquitin proteasome and ubiquitin-like protein conjugation systems are also emerging as new therapeutic targets in cancer therapy. In this review, strategies of targeted cancer therapies with inhibitors of kinases and proteasome systems are discussed. Combinational cancer therapy to overcome drug resistance and to achieve greater treatment benefit through the additive or synergistic effects of each individual agent is also discussed. Finally, the opportunities in the future cancer therapy with molecularly targeted anticancer therapeutics are addressed.

• 대한기계학회논문집A
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• 제31권6호
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• pp.635-643
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• 2007

As many engineers and technicians are involved in the design process of large scale and/or complex products, there are a lot of miss matches and interferences due to designers' faults and several kinds of CAD systems. Recently, CAD systems are applied to verify and check the assembly process. Digital Mock-Up(DMU) system, a tool to build a virtual mock-up in the design stage, has been used to prevent the interferences and miss matches during precision design processes. Using the virtual assembly tool, engineers are able to design precision and interference free parts without physical mock-ups. Instead of a single CAD source, several CAD systems are used to design a complex product. Several organizations are involved in the distributed design environment for heterogeneous multi-CAD assembly. XML and the lightweight CAD file are proposed for the multi-CAD assembly. XML data contains hierarchy of the heterogenenous multi-CAD assembly. STEP PDM schema and STEP ISO 10303-28 formations are applied to construct the XML data. The lightweight CAD file produced from various CAD files through ACIS kernel and InterOp not only contains mesn, B-Rep and topological data, but also is used to visualize CAD data and to verify dimensions. Developed system is executed on the desktop computers. It does not require commercial CAD systems to visualize 3D assembly data. Real-time interference and fitness checks, dimensional verification, and design and assembly verification are performed on the developed system. Assembly of heterogeneous models for a car is conducted to verify the effectiveness of the developed DMU system on the Internet.

• 벤처창업연구
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• 제18권2호
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• pp.187-200
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• 2023

본 연구는 대학에서 직・간접적으로 수행하고 있는 창업교육, 창업지원제도, 창업멘토링의 매개가 창업의지에 어떻게 영향을 미치는가를 살펴보고 창업효능감의 조절효과와 대학생의 창업 가능성을 높일 수 있는 프로그램 개발과 방향성을 제시하는 데 있다. 본 연구는 대학생의 대학 창업교육 만족도, 창업지원제도인식, 창업멘토링이 창업의지에 미치는 영향에서 창업효능감이 창업의지에 어떻게 영향을 미치는지에 대해 분석하였다. 창업지원제도인식은 정부창업지원정책과 대학창업지원사업으로 창업멘토링은 멘토링 기능(문제해결 기능, 네트워킹 기능, 의사소통 기능, 동기부여 기능)과 멘토 신뢰(인지적 신뢰, 정서적 신뢰)로 구분하였으며, 독립변수인 대학 창업교육 만족도, 창업지원제도인식, 창업멘토링과 종속변수인 창업의지 사이에서 창업효능감을 조절변수로 지정하여 실증분석을 실시하였다. 연구결과로는 첫째, 창업교육 만족도는 대학생의 창업의지에 영향을 미치는 것으로 나타났다. 둘째, 창업지원제도 중 대학창업지원사업은 대학생의 창업의지에 영향을 미치는 것으로 나타났다. 셋째, 창업효능감이 창업지원제도인식 중 대학창업지원사업과 대학생의 창업의지의 관계에 있어 조절작용을 하는지 검증한 결과, 창업효능감은 조절효과가 있는 것으로 나타났다. 본 연구의 분석결과를 토대로 다음의 시사점을 도출할 수 있다. 첫째, 창업교육의 만족도를 높일 수 있도록 창업교육에 대한 꾸준한 개선 노력이 필요할 것이다. 둘째, 대학생들의 창업의지를 극대화하고 실전창업으로 확산될 수 있도록 대학 내외 창업 관련 정보 제공, 창업아이템을 실체화 시킬 수 있는 프로그램의 연계, 창업아이템 검증, 창업멘토링 제공, 상시상담이 가능한 창업상담창구 구축 및 운영이 필요할 것이다. 대학 내 창업상담창구 운영을 통해 대학에서 지원하는 교육제도 및 창업의 간접경험을 수행할 수 있는 대학창업지원사업과 자금을 지원하는 정부창업지원정책을 인식할 수 있을 것이다. 셋째, 대학 내 교수, 직원, 선배창업자 등 창업 분야의 멘토와의 연결을 통해 창업멘토링을 제공할 수 있는 프로그램 개설이 필요할 것이다. 넷째, 창업의 준비과정에 대한 철저한 교육과 선배창업자의 창업실패경험을 간접적으로 체험할 수 있는 창업특강, 대학생의 전공별, 개인별 성향에 따른 맞춤형 창업교육의 프로그램 개발이 필요하다.

• Journal of Computing Science and Engineering
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• 제5권3호
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• pp.246-256
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• 2011

Due to the increasingly aging population, there is a rising demand for assistive living technologies for the elderly to ensure their health and well-being. The elderly are mostly chronic patients who require frequent check-ups of multiple vital signs, some of which (e.g., blood pressure and blood glucose) vary greatly according to the daily activities that the elderly are involved in. Therefore, the development of novel wearable intelligent systems to effectively monitor the vital signs continuously over a 24 hour period is in some cases crucial for understanding the progression of chronic symptoms in the elderly. In this paper, recent development of Wearable Intelligent Systems for e-Health (WISEs) is reviewed, including breakthrough technologies and technical challenges that remain to be solved. A novel application of wearable technologies for transient cardiovascular monitoring during water drinking is also reported. In particular, our latest results found that heart rate increased by 9 bpm (P < 0.001) and pulse transit time was reduced by 5 ms (P < 0.001), indicating a possible rise in blood pressure, during swallowing. In addition to monitoring physiological conditions during daily activities, it is anticipated that WISEs will have a number of other potentially viable applications, including the real-time risk prediction of sudden cardiovascular events and deaths.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.389-394
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• 2004

A Fuzzy Logic Sliding Mode Control or FLSMC for the uninterruptible power system (UPS) is presented, which is tracking a sinusoidal ac voltage with specified frequency and amplitude. The FLSMC algorithm combines feedforward strategy with the Variable Structure Control (VSC) or Sliding Mode Control (SMC) and fuzzy logic control. The control function is derived to guarantee the existence of a sliding mode. FLSMC has an advantage that the stability of FLSMC can be proved easily in terms of VSC. Furthermore, the rules of the proposed FLSMC are independent of the number of system state variables because the input of the suggested controller is fuzzy quantity sliding surface value. Hence the rules of the proposed FLSMC can be reduced. The simulation results illustrate that the purposed approach gives a significant improvement on the tracking performances. It has the small overshoot in the transient and the smaller chattering in the steady state than the conventional VSC. Moreover, its can achieve the requirements of robustness and can supply a high-quality voltage power source in the presence of plant parameter variations, external load disturbances and nonlinear dynamic interactions.