• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.1
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• pp.1-6
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• 2006

High performance $Si_{0.8}Ge_{0.2}$ heterostructure metal-oxide-semiconductor field effect transistors (MOSFETs) were fabricated using well-controlled delta-doping of boron and $Si_{0.8}Ge_{0.2}$/Si heterostructure epitaxal layers grown by reduced pressure chemical vapor deposition. In this paper, we report 1/f noise characteristics of the SiGe pMOSFETs measured under various bias conditions of the gate and drain voltages changing in linear operation regions. From the noise spectral density, we found that the gate and drain voltage dependence of the noise represented same features, as usually scaled with $f^{-1}$ However, 1/f noise was found to be much lower in the device with boron delta-doped layer, by a factor of $10^{-1}_10^{-2}$ in comparison with the device fabricated without delta-doped layer. 1/f noise property of delta-doped device looks important because the device may replace bipolar transistors most commonly embedded in high-frequency oscillator circuits.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2009.01a
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• pp.258-262
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• 2009

In this paper, we propose an effective memory reduction algorithm to reduce the amount of reference frame buffer and memory bandwidth in video encoder and decoder. In general video codecs, decoded previous frames should be stored and referred to reduce temporal redundancy. Recently, reference frames are recompressed for memory efficiency and bandwidth reduction between a main processor and external memory. However, these algorithms could hurt coding efficiency. Several algorithms have been proposed to reduce the amount of reference memory with minimum quality degradation. They still suffer from quality degradation with fixed-bit allocation. In this paper, we propose an adaptive block-based min-max quantization that considers local characteristics of image. In the proposed algorithm, basic process unit is $8{\times}8$ for memory alignment and apply an adaptive quantization to each $4{\times}4$ block for minimizing quality degradation. We found that the proposed algorithm could improve approximately 37.5% in coding efficiency, compared with an existing memory reduction algorithm, at the same memory reduction rate.

• Archives of Plastic Surgery
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• v.40 no.1
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• pp.57-61
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• 2013

Background Von Recklinghausen disease or neurofibromatosis type 1 is an autosomal dominant genetic disorder of chromosome 17q11.2. The most common characteristic findings of NF 1 include multiple and recurrent cutaneous neurofibromas associated with psychosocial distress. Methods Sixteen patients (9 female, 7 male; average age, 31 years; range, 16 to 67 years) with multiple cutaneous neurofibromas between March 2010 and February 2012 were included in the study. All patients were treated with radiosurgical ablation and excision under general anesthesia. Results All 16 patients were satisfied with the results, when questioned directly during the outpatient department follow-up. The only complaint from a few patients was minimal scarring, but acceptable results were obtained in the end. Conclusions The radiofrequency procedure is almost bloodless and quick, creating a smaller necrotizing zone. Therefore, instead of employing the time consuming traditional surgery, such as laser therapy and electrosurgical excision, that produces uncertain results and can affect normal adjacent tissue, treatment of neurofibromas with radiofrequency ablation and excision can be an alternative choice of treatment for patients with a large number of neurofibromas.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.132-132
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• 2010

In the nano-scale Si processing, patterning processes based on multilevel resist structures becoming more critical due to continuously decreasing resist thickness and feature size. In particular, highly selective etching of the first dielectric layer with resist patterns are great importance. In this work, process window for the infinitely high etch selectivity of silicon oxynitride (SiON) layers and silicon nitride (Si3N4) with EUV resist was investigated during etching of SiON/EUV resist and Si3N4/EUV resist in a CH2F2/N2/Ar dual-frequency superimposed capacitive coupled plasma (DFS-CCP) by varying the process parameters, such as the CH2F2 and N2 flow ratio and low-frequency source power (PLF). It was found that the CH2F2/N2 flow ratio was found to play a critical role in determining the process window for ultra high etch selectivity, due to the differences in change of the degree of polymerization on SiON, Si3N4, and EUV resist. Control of N2 flow ratio gave the possibility of obtaining the ultra high etch selectivity by keeping the steady-state hydrofluorocarbon layer thickness thin on the SiON and Si3N4 surface due to effective formation of HCN etch by-products and, in turn, in continuous SiON and Si3N4 etching, while the hydrofluorocarbon layer is deposited on the EUV resist surface.

• New & Renewable Energy
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• v.3 no.2 s.10
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• pp.60-67
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• 2007

This paper describes the design and integration of the wind-fuel cell hybrid system. The hybrid system components included a wind turbine, an electrolyzer (for generation of H2), a PEMFC (Proton Exchange Membrane Fuel Cell), hydrogen storage tank and BOP (Balance of Plant) system. The energy input is entirely provided by a wind turbine. A DC-DC converter controls the power input to the electrolyzer, which produces hydrogen and oxygen form water. The hydrogen used the fuel for the PEMFC. Hydrogen may be produced and stored in high pressure tank by hydrogen gas booster system. Wind conditions are changing with time of day, season and year. So, wind power is a variable energy source. The main purpose with these WT-FC hybrid system is to store hydrogen by electrolysis of water when wind conditions are good and release the stored hydrog en to supply the fuelcell when wind is low.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2011.11a
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• pp.506-509
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• 2011

압축공기 포는 공기포혼합기를 사용하여 약제와 물 그리고 압축공기를 혼합하여 방출하는 방식으로, 물의 확보가 곤란한 장소라도 소화 효율을 높이는 시스템으로서 주목되고 있으며, 현재 해외 선진국에서는 이미 개발되어 상용화 되어있다. 본 연구에서는 국제적 기준에 따른 압축공기포소화설비의 성능평가시험을 위해 미국, 캐나다 등에서 채택한 UL-162 시험방법을 적용하여 시험을 수행하였으며, 그 결과 기존의 포소화시스템과 압축공기포소화시스템의 성능비교시험을 통해 압축공기포가 기존의 포소화방식 보다 소화성능이 우수한 것으로 나타났다.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 1997.11a
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• pp.120-129
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• 1997

The fire protective coating can reduce certain damages in case of fire, also conserve energy by thermal insulation and prevent corrosion and errosion in normal daily life by means of blocking thermal transfer, that were generally made of organic, inorganic and metallic materials as adiabatic coating. In case of inorganic material such as soluble silicate, it produces less toxic substances which are exposed to Ore, and have a plenty of raw material. Also inorganic thermal insulator is good in heat resistance. To develope such a excellent inorganic thermal insulator, the study of fire protective coating using the alkali silicate is necessary The principle of intumescence for alkali silicate is from rapid evolution of water in the coating material, the quantity of water in it is of course influenced on the degree of intumescence. The phenomenon of intumescence in ternary silicate is increased as the radius of ion is bigger, and this is caused by evolution of so many kinds of water. The individual degree of intumescence is ordered like this ; $K^+$ > $Na^+$ > $Li^+$ . The best protection effect is similarity found to intumescence of ternary silicate. The result of X-ray diffraction analysis indicates that $KHSi_2O_5$ is an important ingredient in K-silicate.

• Journal of Korea Water Resources Association
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• v.39 no.8 s.169
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• pp.677-690
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• 2006

The LH-OAT (Latin Hypercube One factor At a Time) method for sensitivity analysis and SCE-UA (Shuffled Complex Evolution at University of Arizona) optimization method were applied for the automatic calibration of SWAT model in Bocheong-cheon watershed. The LH-OAT method which combines the advantages of global and local sensitivity analysis effectively identified the sensitivity ranking for the parameters of SWAT model over feasible parameter space. Use of this information allows us to select the calibrated parameters for the automatic calibration process. The performance of the automatic calibration of SWAT model using SCE-UA method depends on the length of calibration period, the number of calibrated parameters, and the selection of statistical error criteria. The performance of SWAT model in terms of RMSE (Root Mean Square Error), NSEF (Nash-Sutcliffe Model Efficiency), RMAE (Relative Mean Absolute Error), and NMSE (Normalized Mean Square Error) becomes better as the calibration period and the number of parameters defined in the automatic calibration process increase. However, NAE (Normalized Average Error) and SDR (Standard Deviation Ratio) were not improved although the calibration period and the number of calibrated parameters are increased. The result suggests that there are complex interactions among the calibration data, the calibrated parameters, and the model error criteria and a need for further study to understand these complex interactions at various representative watersheds.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.49 no.6
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• pp.57-62
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• 2012

In this paper, WCDMA indoor repeater antenna using an absorber based on metamaterial structure for high isolation is proposed. The proposed antenna consist of the main patch with the absorber based on metamaterial structure and parasitic patch. The WCDMA bandwidth is obtained by utilizing the coupling between the main and parasitic patches. The size of the absorber based on metamaterial structure is $13mm{\times}13mm$, the absorption is about 94 % at 2.18 GHz. The isolation characteristic of proposed WCDMA indoor repeater antenna between the service and donor antennas is improved by using a absorber based on metamaterial. The proposed WCDMA indoor repeater antenna has a gain higher than 6 dBi with a VSWR less than 2, and an isolation between the service and donor antennas greater than 85 dB over the WCDMA band from 1.92 GHz to 2.17 GHz. And size of the proposed antenna is $75mm{\times}75mm$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.410-410
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• 2009

현재 탄소나노튜브 (carbon nanotube, CNT)를 여러 분야에 응용하기 위해 다양한 연구가 진행되고 있다. 본 논문에서는 단일벽 CNT (single-walled CNT)를 여러 가지 계면활성제로 최적 분산시킨 수용액으로부터 제조한 투명 전도성 필름을 터치스크린이나 디스 플레이 소자에 응용할 목적으로 필름의 전기저항 및 광 투과도를 향상시키기 위한 연구를 수행하였다. 우선 계면활성제로 분산시킨 정량의 CNT 수용액을 알루미나 재질의 필터에서 진공 필터링하여 CNT 필름을 제조하였다. 알루미나 필터를 sodium hydroxide (NaOH) 수용액으로 용해시켜 제거하여 얻은 CNT 필름을 유리기판 위에 부착시켰다. 필름의 전기저항을 낮추기 위해 유리기판 위에 부착된 CNT 필름을 질산($HNO_3$) 용액으로 처리하였다. Scanning electron microscopy, UV-Vis spectroscopy를 이용하여 각각 필름의 형상과 광투과도를 분석하였고, 4-point probe로 면 저항을 측정하였다. 계면활성제로 분산시킨 대부분의 CNT 필름의 면 저항은 질산 처리에 의해 감소하였다. 이는 CNT 표면에 코팅되어 있던 계면활성제가 질산에 의해 제거되었기 때문인 것으로 예상된다. 그리고 anionic 계면활성제를 이용한 필름이 대체로 낮은 면 저항을 보였고, 그중 분산력이 가장 좋은 sodium dodecyl benzenesulfonate(SDBS)가 최저의 면 저항을 나타내었다. 질산처리에서 Polyvinyl pyrrolidone(PVP)과 cetyltrimethylammonium bromide(CTAB)를 사용하여 제조한 CNT 필름의 면 저항이 가장 뚜렷한 감소를 보였다.