• 전기학회논문지
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• 제58권6호
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• pp.1146-1150
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• 2009

Cadmium telluride (CdTe) is one of the most attractive photovoltaic materials due to its low cost, high efficiency and stable performance in physical, optical and electronic properties. Few researches on the influences of uniform surface on the photovoltaic characteristics in large-area CdTe solar cell were not reported. As the preceding study of the effects of thickness-uniformity on the photovoltaic characteristics for the large-area CdTe thin film solar cell, chemical mechanical polishing (CMP) process was investigated for an enhancement of thickness-uniformity. Removal rate of CdTe thin film was 3160 nm/min of the maximum value at the 200 $gf/cm^2$ of down force (pressure) and 60 rpm of table speed (velocity). The removal rate of CdTe thin film was more affected by the down force than the table speed which is the two main factors directly influencing on the removal rate in CMP process. RMS roughness and peak-to-valley roughness of CdTe thin film after CMP process were improved to 96.68% and 85.55%, respectively. The optimum process condition was estimated by 100 $gf/cm^2$ of down force and 60 rpm of table speed with the consideration of good removal uniformity about 5.0% as well as excellent surface roughness for the large-area CdTe solar cell.

• 한국산학기술학회논문지
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• 제12권4호
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• pp.1867-1875
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• 2011

이 논문에서는 저면적 256-point FFT 구조를 제안한다. 저면적 구현을 위하여 CSD(Canonic Signed Digit) 곱셈기 방식을 채택하여 구현하였다. CSD 곱셈기 방식을 효율적으로 적용하기 위해서는 곱셈연산의 가지 수가 적어야 하는데, 여러 알고리즘을 조사한 결과 Radix-$4^2$ 알고리즘이 곱셈연산의 가지 수가 적음을 발견하였다. 따라서 제안 구조는 Radix-$4^2$ DIF 알고리즘과 CSD 곱셈기 방식을 사용하였다. 즉 Radix-$4^2$ 알고리즘을 사용하여 4개의 스테이지에서 사용되는 곱셈연산의 가지 수를 최소화한 후에 각각의 곱셈연산 블록은 CSD 곱셈기를 사용하여 구현하였다. CSD 곱셈기 구현에서 공통패턴을 공유하여 덧셈기의 수를 줄일 수 있는 CSS(Common Sub-expression Sharing) 기술을 사용하여 구현면적을 더욱 감소시켰다. 제안된 FFT 구조를 Verilog-HDL 코딩 후 합성하여 구현한 결과, Radix-4를 사용한 구조와 비교하여 복소 곱셈기 부분의 29.9%의 cell area 감소를 보였고 전체적인 256-point FFT 구조에 대한 비교에서는 12.54% cell area 감소를 보였다.

• 한국군사과학기술학회지
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• 제21권2호
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• pp.225-234
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• 2018

In this paper, we consider a problem of partitioning a search area into smaller rectangular regions, so that multiple platforms can conduct search operations independently without requiring unnecessary coordination among themselves. The search area consists of cells where each cell has some prior information regarding the probability of target existence. The detection probability in particular cell is evaluated by multiplying the observation probability of the platform and the target existence probability in that cell. The total detection probability within the search area is defined as the cumulative detection probability for each cell. However, since this search area partitioning problem is NP-Hard, we decompose the problem into three sequential phases to solve this computationally intractable problem. Additionally, we discuss a special case of this problem, which can provide an optimal analytic solution. We also examine the performance of the proposed approach by comparing our results with the optimal analytic solution.

• Carbon letters
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• 제4권3호
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• pp.121-125
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• 2003

The Pt-Ru/Carbon as an anode catalyst supported on the commercial activated carbon (AC) having high surface area and micropore was characterized for application of Direct Methanol Fuel Cell (DMFC). The Pt-Ru/AC anode catalyst used in this experiment showed the performance of $600\;mA/cm^2$ current density at 0.3 V. The borohydride reduction process using $NaBH_4$, denoted as a process A, showed much higher current and power densities than process B prepared by changing the reduction and washing process of process A. The particle sizes are strongly affected by the reduction process than the specific surface area of raw active carbon and the sizes are almost constant when the specific surface area of carbon are over than the $1200\;m^2/g$. Smaller particle size of catalyst and more narrow intercrystalite distance increased the performance of DMFC.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 D
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• pp.1544-1546
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• 1999

The fabrication process for ceramic fuel cell with a large electrode area was investigated. A cofired cell of two layer, electrolyte/anode, yielded a power of $200mW/cm^2$. Its performance loss was mainly due to iR drop in the anode side. The performance of the cofired of three layer. cathode/electrolyte/ anode, was much lower than that of two layer, which resulted from the large iR drop and overvoltage at the cathode side. Also a flat cell with a large area of $7.7{\times}10.8cm^2$ was fabricated successfully and tested using ceramic and metallic interconnectors. The large cell with metallic interconnectror showed a good performance of 0.6 V, 4.5 A.

• 한국시뮬레이션학회논문지
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• 제10권4호
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• pp.11-20
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• 2001

In the IMT-2000 networks, the model of micro/pico cell is suggested for transmission of multimedia service. Hence, the efficient method is required for processing of mobile calls in micro/pico cell. In the central urban area, mobile calls may be dynamically increased because of many mobile users. And microcel]/picocell size has small size, handover calls will be more increased. Therefore, many of mobile calls is occurred at a cell in the central urban area, so channel requests for these calls will be increased in the call. In this paper, we propose a scheme, FTC(Fault Tolerant Channel allocation) which is the channel management method for hard handover and new call in a mobile cell of central urban area. When available channels in the cell are consumed, the FTC investigates channel states of neighbor cells in the RNC(Radio Network Controller) or BSC (Base Station Center), and provide available channel for mobile call. The ]no scheme is analyzed and compared with existing channel management method by simulation.

• 분석과학
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• 제27권1호
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• pp.27-33
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• 2014

This study described about preparation of the cross-linked silk fibroin (SF) film by ${\gamma}$-irradiation of the casted SF film, which is fabricated from aqueous solution regenerated via fibers of cocoons and their application as supports for human cell culture. The properties of cross-linked SF film were evaluated by FT-IR spectroscopy, contact angle, solubility to water, thermal analysis, surface area analyzer, and morphology via scanning electron microscopy (SEM). The cross-linked SF films were not dissolved in water and exhibited the rough surface morphology, large surface area, and good thermal properties. The human fibroblast cell (CCD-986sk) and embryo kidney-ft cell were well growed on the surface of cross-linked SF film supports prepared by ${\gamma}$-irradiation. The cross-linked SF film prepared by ${\gamma}$-irradiation can be used as biomaterials for human cell culture.

• Advances in Energy Research
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• 제8권4호
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• pp.253-264
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• 2022

This paper deals with the effects of design (active area, current density, membrane conductivity) and operating parameters (temperature, relative humidity) on the performance of hydrogen-fuelled proton exchange membrane (PEM) fuel cell. The design parameter of a PEM fuel cell with the active area of the single cell considered in this study is 25 cm² (5 × 5). The operating voltage and current density of the fuel cell were 0.7 V and 0.5 A/cm² respectively. The variations of activation voltage, ohmic voltage, and concentration voltage with respect to current density are analyzed in detail. The membrane conductivity with variable relative humidity is also analyzed. The results show that the maximum activation overpotential of the fuel cell was 0.4358 V at 0.21 A/cm² due to slow reaction kinetics. The calculated ohmic and concentrated overpotential in the fuel cell was 0.01395 V at 0.76 A/cm² and 0.027 V at 1.46 A/cm² respectively.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2007년도 춘계학술대회
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• pp.305-308
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• 2007

The field of dye-sensitized solar cell (DSC) is being researched actively at present. Because DSC has several advantages to pass the limits of Si solar cells such as a low manufacturing expense, a simple manufacturing process and its transparency. A lot of researches are underway about materials and processes in the field of dye-sensitized solar cell but its structure has been fixed up as the sandwich structure that both edges are used as positive and negative terminals. But the structure as of present is a factor of decreasing efficiency because the more electrons are recombined the further distance from terminal, considering about the characteristic of dye-sensitized solar cell that electrons generated inside cell are moved by diffusion. In this study, we made experiment on expanding the terminal to shorten internal moving distance of electron and compared the results according to the variation of active area to find out the effect of this trial. As a result, we achieved about 15.5% improvement of maximum power and 0.5% improvement of efficiency from terminal-expanded dye-sensitized solar cell of $2cm^{2}$ active area and concluded that the increasing rate of efficiency is raised as the active area becomes wider.

• Nuclear Engineering and Technology
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• 제56권8호
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• pp.2916-2922
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• 2024

\\In memory semiconductors such as a static random access memory (SRAM), a common problem is soft errors under radiation environment. These soft errors cause bit flips, which are referred to as single event upsets (SEUs). Some radiation-hardened SRAM cells such as a Quatro SRAM, we-Quatro SRAM, and DICE SRAM cells have been reported for years. However, these designs have the disadvantage of taking up more area than a conventional 6T SRAM cell. Thus, we propose a radiation-hardened SRAM cell design that we named capacitor-static random access memory (C-SRAM) without area overhead. The C-SRAM is formed by simply adding a capacitor to the conventional 6T SRAM. It was designed to mitigate the radiation effect using the conservation law of electrical charge. Moreover, it has the same cell size as the conventional 6T SRAM cell. Its static noise margins (SNMs), which are indicators of operational stability, are equal to the conventional 6T SRAM values of 530 mV, 220 mV, and 860 mV in hold, read, and write modes, respectively. The results of the SEU simulation test showed that it had 4.761 times better flipping tolerance than the conventional 6T SRAM with a charge value of 247.494 fC. In addition, irradiation experiments also confirmed that the C-SRAM cell was more tolerant than the 6T SRAM cell. The conventional 6T SRAM and C-SRAM were fabricated using a standard 0.18 ㎛ CMOS process.