• 전기전자학회논문지
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• 제16권3호
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• pp.251-257
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• 2012

본 연구에서는 중소규모 지상파 DTV 방송의 난시청지역 해소를 위한 특정소출력동일채널 DTV 중계기를 구현하였으며, 현장시험을 통하여 실효성을 입증하였다. 동일채널중계기 구현을 위한 설계요구조건들을 수신신호모델 및 이득전달모델을 이용하여 도출하여 시스템 설계에 적용하였다. 구현된 시스템은 출력 10mW/MHz 이하인 특정 소출력 DTV 방송중계용 무선기기로 1km 내외의 커버리지를 갖도록 설계하였다. 시험결과 기존 중계기에 비해 효율적으로 시스템을 구축할 수 있었으며, 수 km 미만의 중소규모 난시청 지역이 많이 발생하는 우리나라 DTV 수신환경 개선에 널리 사용될 수 있다.

• 한국정밀공학회지
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• 제27권4호
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• pp.14-19
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• 2010

In this paper, using interleaved power factor correction how to improve the inverter efficiency studied. Interleaved method can reduce the conduction losses and the inductor energy. Generally, critical conduction mode (CRM) boost PFC converter used low power level because of the high peak currents. if you use the interleaved mode, CRM PFC can be used medium or high power application. interleaved CRM PFC can reduce current ripple for higher system reliability and size of buck capacitor and EMI filter size. Interleaved CRM PFC that is installed in front of inverter can maintain the constant voltage regardless of the input voltage.

• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2009년도 춘계학술발표대회 논문집
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• pp.250-255
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• 2009

This study was analyzed the long term performance of the demonstration system for solar energy desalination in Jeju. we used a solar thermal system as heat source of the single-stage fresh water generator with plate-type heat exchangers and a photovoltaic power system as electric source for hydraulic pumps. The demonstration system was designed and installed at Jeju-island in 2006. The system was comprised of the desalination unit with daily fresh water capacity designed as $2m^3$ a $120m^2$ evacuated tubular solar collector to supply the heat, a $6m^3$ heat storage tank, and a 5kW photovoltaic power generation to supply the electricity of hydraulic pumps for the heat medium fluids. Through the operation during about 3 years, In a clear day more than $400W/m^2$, the daily fresh water showed to produce more than about 500liter, and from January, 2007 to March, 2009 for 3 years, solar irradiance daily averaged was measured $370W/m^2$, the daily fresh water yield showed that can be produced about 330liter.

• Journal of information and communication convergence engineering
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• 제12권4호
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• pp.199-207
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• 2014

A new cooperative MAC protocol called the busy tone cooperative medium access control (BT-COMAC) protocol is proposed to overcome the drawbacks and maximize the advantages of existing schemes. This scheme uses a new metric called decibel power to decide an appropriate helper node. Using received power strength is more efficient in selecting an appropriate helper node, especially in a densely populated network, than the effective transmission rates used in conventional schemes. All communication nodes in a communication service area are assumed to move independently. Two performance metrics are used: System throughput and channel access delay. A performance evaluation of the BT-COMAC protocol is conducted using a computer simulation over a slow fading wireless channel, and its performance results are compared with those of four existing schemes. The numerical results show that the BT-COMAC protocol improves the system throughput by approximately 15% as compared to the best existing scheme.

• Journal of Biosystems Engineering
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• 제23권5호
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• pp.491-498
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• 1998

Transplanting process during the tissue culture of potato seedlings is costly, since the cost of highly skilled labor working in the sanitary environment takes up about 60-70% of the production cost. The objective of this study was to develop a soft gripper of a transplanting robot system for the labor-saving tissue culture. The prototype of the soft gripper was consisted of power-transmitting part finger and plant contacts. The power transmitting part transformed the rotating motion of a step motor to the reciprocating motion of the finger. Plant stems used in the test were potato seedlings cultured for six weeks. The dimensional characteristics of cultured seedlings, the compressive strengths of the stems, the extractive force from the culture medium and the gripping force of the finger were measured. A proper gripping force was found to be 0.343N at the extractive force of 0.41N when the plant contacts were made of silicon. Sixteen plants out of 70 trials were tangled with others, resulting in the success rate of 77.1%.

• 한국경영과학회:학술대회논문집
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• 한국경영과학회 2001년도 추계학술대회 논문집
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• pp.362-365
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• 2001

Human, physical damage is happened frequently to consumer's safety accident by product defect on modern industrial society. Accordingly, advanced nation including the United States of America enforce product liability law and is protecting consumer more actively from danger of product defect. Our country(Korea) may enforce product liability law since July, 2002, and if business does not grope effective confrontation way about PL, capital strength weak smaller enterprise and venture business corporation's competitive power may affect much corporation's competitive power enfeeblement and survival. This research supplement based on induction and operating QMS in smaller enterprise essential factor that corporations must equip according to product liability law enforcement. And we present integration quality management system model of Product liability to do so that smaller enterprises may can cope effectively at force of Product liability law.

• 동력기계공학회지
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• 제8권2호
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• pp.53-58
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• 2004

In this paper, the semi active mount featuring Magneto rheological fluid(MR Fluid) is proposed. MR fluid is suspension of micro sized magnetizable particles in a fluid medium, and its apparent viscosity can be varied by the applied strength of magnetic field. When the controllable MR fluid is applied to mechanical devices, the devices provide simple, rapid response interfaces between electronic controls and mechanical systems. The MR fluid is applied in the conventional fluid mount for improving its performance of the mount's isolation effect. A appropriate size of the MR mount is designed and manufactured on the basis of Bingham model of MR fluid. In addition, the field dependent damping forces of MR mount are evaluated with respect to the input frequency variation.

• 동력기계공학회지
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• 제16권6호
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• pp.24-29
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• 2012

In this study, the numerical simulation has been performed to investigate the hydrodynamic evaluation between double plate steel rudder and newly designed foil type rudder for small fishing boat. The simulations are carried out in 2 speed ranges with 7 variations of flow's angle of attack which is at intervals of about 5 degree respectively. As the well-known commercial code, FLUENT and CATIA are used as the solver. The simulation results show that new designed foil type rudder is better than conventional double plate rudder in terms of Lift and Drag of running boat in the water.

• 동력기계공학회지
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• 제12권5호
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• pp.54-58
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• 2008

최근 열교환기의 향상을 위해 발포다공성매체의 적용이 증가하고 있다. 열교환기의 적용에 있어서 발포다공성매체의 이점을 살펴보기 위해 본 연구에서는 2가지 실험을 수행하였다. 첫 번째는 수력의 관점에서 투과계수 및 내부계수를 결정하는 것이고, 두 번째는 열교환의 관점에서 다공성매체의 유효전도율을 측정하는 것이다. 본 실험에서는 기공도는 거의 같으나 기공의 크기가 각각 20 ppi와 40 ppi인 구리 다공성매체를 사용하였다. 실험의 결과는 40 ppi 크기의 다공성매체가 수력과 열교환, 두가지 관점 모두에서 보다 높은 저항 효율을 나타낸다는 것을 보여준다.

• 동력기계공학회지
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• 제13권1호
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• pp.39-45
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• 2009

The attenuation of the fundamental non-torsional modes that propagate down buried steel water pipes has been studied. The mode shapes, mode attenuation due to leakage into the surrounding medium and the scattering of the modes as they interact with pipe joints and fittings have been investigated. In the low frequency region the mode predicted to dominate over significant propagation distances approximates a plane wave in the water within pipe. The established acoustic technique used to locate leaks in buried steel water pipes assumes that leak noise propagates as a single non-dispersive mode at a velocity related to the low frequency asymptote of this water borne mode.