• 한국정보통신학회논문지
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• 제2권2호
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• pp.187-195
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• 1998

ITU-T T.120 시리즈에서 제시하는 회의 서비스 모델에 따라 회의 시스템을 구축하였다. 구축된 회의 서비스 시스템은 LAN상에서 마이크로소프트사의 넷미팅을 단말로 사용하였으며 단말사이의 통신을 위한 MCU 를 자체 개발하였다. 본 논문에서는 구축된 회의 서비스 시스템에서 다지점 통신 서비스를 지원하는 수송프로토콜 스택의 설계 및 구현 방안에 대하여 기술한다. 또한, 개발된 MCU와 단말로 사용하는 넷미팅사이의 상호운용성 시험에서 발생된 문제점과 이의 해결 방안에 대하여 기술한다.

• 반도체디스플레이기술학회지
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• 제9권2호
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• pp.21-25
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• 2010

In response to the industrial needs for automated handling of very thin solar cell wafers, this paper presents the design concept for the individual wafer separation from the stacked wafers by utilizing continuous water jet. The experimental apparatus for automated wafer separation was constructed and it includes the water jet system and the microprocessor controlled wafer stack advancing system. Through a series of tests, the performance of the proposed design is quantified into the success rate of single wafer separation and the rapidity of processing wafer stack. Also, the inclination angle of wafer equipped cartridge and the water jet flowrate are found to be important parameters to be considered for process optimization. The proposed design shows the concept for fast and efficient processing of wafer separation and can be implemented in the automated manufacturing of silicon based solar cell wafers.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 F
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• pp.2597-2600
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• 1999

Semiconductor devices can be series stacked for the application of high voltage switching. It can provide high reliability and long lifetime by the safe design with a reasonable margin. The equal voltage distribution at solid-state switches in series should be guaranteed. Static and dynamic voltage division, over current protection must be considered carefully in the design stage. A fast switching thyristor is a good candidate for the high power pulse applications. A high voltage switching module is designed and tested. Its specifications are working voltage of 70 kV, switching pulse width of 120${\mu}s$, peak switching current of 220A, maximum repetition rate of 200pps. The module can be series connected to get higher working voltage. This paper presents the design details and the test results are compared with expected circuit simulations.

• Journal of Power Electronics
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• 제16권2호
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• pp.786-797
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• 2016

This paper describes the design and development of a novel semiconductor-based solid-state switch for damped oscillating voltage test system. The proposed switch is configured as two identical series-connected switch stacks, each of which comprising 10 series-connected IGBT function units. Each unit consists of one IGBT, a gate driver, and an auxiliary voltage sharing circuit. A single switch stack can block 20 kV-rated high voltage, and two stacks in series are proven applicable to 30 kV-rated high voltage. The turn-on speed of the switch is approximately 250 ns. A flyback topology-based power supply system with a front-end power factor correction is built for the drive circuit by loosely inductively coupling each unit with a ferrite core to the primary side of a power generator to obtain the advantages of galvanic isolation and compact size. After the simulation, measurement, and estimation of the parasitic effect on the gate driver, a prototype is assembled and tested under different operating regimes. Experimental results are presented to demonstrate the performance of the developed prototype.

• Journal of Power Electronics
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• 제19권1호
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• pp.68-78
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• 2019

The emergence of high voltage conversion applications has resulted in a trend of using semiconductor device series associations. Series associations allow for operation at blocking voltages, which are higher than the nominal voltage for each of the semiconductor devices. The main challenge with these topologies is finding a way to guarantee the voltage balance between devices in both blocking and switching transients. Most of the methods that have been proposed to mitigate static and dynamic voltage unbalances result in increased losses within the device. This paper introduces a new series stack topology, where the voltage unbalances are reduced. This in turn, mitigates the switching losses. The proposed topology consists of a circuit that ensures the soft switching of each device, and one auxiliary circuit that allows for switching energy recovery. The principle for the topology operation is presented and experimental tests are performed for two modules. The topology performs excellently for switching transients on each of the devices. The voltage static unbalances were limited to 10%, while the activation/deactivation delay introduced by the lower module IGBT driver takes place in the dynamic unbalances. Thus, the switching losses are reduced by 40%, when compared to hard switching configurations.

• 한국정밀공학회지
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• 제33권1호
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• pp.17-22
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• 2016

In smart factories, the entire manufacturing process from design to the final product is simulated in a virtual manufacturing environment and optimized before starting production. Suppliers and customers make decisions based on the simulation results. Therefore, effective rendering of the information of the virtual products to suppliers and customers is essential for this manufacturing paradigm. In this study, a method of rendering the surface roughness of the virtual products using a tactile display is presented. A tactile display device comprising a $3{\times}3$ array of individually controlled piezoelectric stack actuators is constructed. The surface topology of the virtual products is rendered directly by controlling the piezoelectric stack actuators. A series of experiments is performed to evaluate the performance of the tactile display device. An electrical discharge machined surface is rendered using the proposed method.

• Bulletin of the Korean Chemical Society
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• 제27권2호
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• pp.281-285
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• 2006

Microbial fuel cells (MFC) stacked with bipolar plates have been constructed and their performance was tested. In this design, single fuel cell unit was connected in series by bipolar plates where an anode and a cathode were made in one graphite block. Two types of bipolar plate stacked MFCs were constructed. Both utilized the same glucose oxidation reaction catalyzed by Gram negative bacteria, Proteus vulgaris as a biocatalyst in an anodic compartment, but two different cathodic reactions were employed: One with ferricyanide reduction and the other with oxygen reduction reactions. In both cases, the total voltage was the mathematical sum of individual fuel cells and no degradation in performance was found. Electricity from these MFCs was stored in a supercapacitor to drive external loads such as a motor and electric bulb.

• Smart Structures and Systems
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• 제21권2호
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• pp.195-205
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• 2018

Research on Lamb wave-based damage identification in plate-like structures depends on precise knowledge of dispersive wave velocity. However, boundary reflections with the same frequency of interest and greater amplitude contaminate direct waves and thus compromise measurement of Lamb wave dispersion in different materials. In this study, non-reflecting boundaries were proposed in both numerical and experimental cases to facilitate time-frequency characterization of Lamb wave dispersion. First, the Lamb wave equations in isotropic and laminated materials were analytically solved. Second, the non-reflecting boundaries were used as a series of frames with gradually increased damping coefficients in finite element models to absorb waves at boundaries while avoiding wave reflections due to abrupt property changes of each frame. Third, damping clay was sealed at plate edges to reduce the boundary reflection in experimental test. Finally, the direct waves were subjected to the slant-stack and short-time Fourier transformations to calculate the dispersion curves of phase and group velocities, respectively. Both the numerical and experimental results suggest that the boundary reflections are effectively alleviated, and the dispersion curves generated by the time-frequency analysis are consistent with the analytical solutions, demonstrating that the combination of non-reflecting boundary and time-frequency analysis is a feasible and reliable scheme for characterizing Lamb wave dispersion in plate-like structures.

• 대한조선학회논문집
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• 제45권3호
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• pp.288-295
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• 2008

Passive-type control devices such as resilient mounts and wire rope isolators are generally used for protecting the shipboard equipment from shock loading and for suppressing the mechanical vibration of the equipment in naval ships. To improve the performance of the control device, a new hybrid mount is under development in this study. This mount consists of a passive-type rubber element and an active-type piezo-stack element. It can be expected that the mount has enhanced performance of about 20 dB or more with respect to transmissibility through a series of performance tests of prototype mount.

• KEPCO Journal on Electric Power and Energy
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• 제2권4호
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• pp.589-593
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• 2016

미생물연료전지(Microbial Fuel Cell; MFC)는 전기화학활성미생물로 불리는 미생물을 촉매로 이용하여, 유/무기물의 산화환원 반응을 통해서 전기에너지를 생산할 수 있는 장치이다. 단일 MFC에서 발생하는 낮은 전기생산량을 극복하기 위해, 다수의 형태의 MFC를 직렬 또는 병렬로 연결하는 방법이 연구되고 있다. 본 연구에서는 6개의 단위 막전극접합체(Separator Electrode Assembly; SEA)로 구성된 침지평판형과 직립평판형 MFC 스택을 운전하였다. 단위 MFC와 MFC 스택의 전기발생량을 비교하였으며, 이를 통해서 MFC의 최적 스택기술을 확보하기 위한 기초자료로 활용하고자 하였다. 모든 SEA가 산화전극부를 공유하고 있는 침지평판형 MFC의 경우, 직렬과 병렬을 함께 사용할 경우, 단일 연결 방식을 사용하는 것보다 전압의 손실이 더 크게 나타났으며, 단일 연결방법 중 병렬연결 하는 것이 손실을 최소화 할 수 있는 것으로 나타났다. 직립평판형 MFC의 경우, 산화전극부를 공유하고 있는 SEA만 직렬 연결할 경우에는 전압의 손실이 크게 나타났으며, 산화전극부를 공유하고 있는 SEA간에 병렬 연결 후, 병렬 연결된 SEA를 직렬연결하는 방식이 전압의 손실을 최소화 할 수 있을 것으로 나타났다.