• 대한전자공학회논문지SD
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• 제48권10호
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• pp.15-19
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• 2011

부스트 컨버터를 이용하여 열전소자의 전력을 전달하는 회로를 이용하여 최대전력점 추적회로를 제안하였다. 제안하는 최대 전력점 추적회로는 2개의 비교기를 사용하여 연속된 샘플링 전압을 비교하고 최대전력점을 갖는 입력 펄스 신호의 듀티비에서 열전 발전소자의 전력 구동회로가 동작하도록 하는 것이다. 시뮬레이션 결과에서는 두 클럭 이내에서 최대전력점을 찾았으며, 3 클럭 이내에서 최적의 PWM 신호를 만들었다. 제안한 최대전력점 추적회로는 0.18 um CMOS 공정으로 설계하였으며 제작중이다.

• 대한기계학회논문집B
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• 제27권7호
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• pp.845-852
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• 2003

Liquid desiccant dehumidification system can be used effectively to save energy consumed in air conditioning as an alternative compared with conventional air conditioning systems by reducing latent heat load. The dehumidifier and the regenerator from the heart of this system. The latent part of the cooling load is handled using liquid desiccant. In this study, the experimental regenerator has been designed to study the regeneration characteristics of the aqueous triethylene glycol(TEG) system. The performance factors of the regenerator with finned tube heat exchanger were evaluated by a series of experimental runs. The regeneration process is highly dependent on the liquid desiccant conditions, such as, temperature, concentration and flow rate. In addition, the effects of the inlet air temperature, humidity and flow rate were discussed. Data obtained are useful for design guidance and performance analysis of a regenerator, particularly for a liquid desiccant cooling system.

• 설비공학논문집
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• 제16권10호
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• pp.952-959
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• 2004

The hybrid liquid desiccant air conditioning system has been in use for many years, primarily in industrial process applications requiring dehumidification and humidity control. In this study, the hybrid dehumidifier has been designed to study the dehumidification characteristic of the aqueous triethylene glycol (TEG) solution. The experimental results show energy efficient characteristics of hybrid liquid desiccant air conditioning system compared with the refrigeration system in terms of energy use, the difference of pressure loss between hybrid liquid desiccant air conditioning system and refrigeration system. Data obtained are useful for design guidance and performance analysis of the hybrid air conditioning system.

• 설비공학논문집
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• 제16권7호
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• pp.630-638
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• 2004

Liquid desiccant dehumidification systems have the ability to provide efficient humidity and temperature control while saving the electrical energy requirement for air conditioning as compared to a conventional system. The dehumidifier and the regenerator form the heart of this system. The latent part of the cooling load is overcome using liquid desiccant. The model regenerator has been designed to study the absorption characteristic of the aqueous triethylene glycol (TEG) solution which is in the flow range from 20 to 50 LPM. Also, this system designed that was able to change the height of the regenerator and dehumidifier. Because the effect of performance have different result according the height. The effect of performance factors of the regenerator with inlet solution flow rate, air flow rate, solution concentration, solution temperature, brine temperature, air temperature and inlet air relative humidity have been analyzed. Data obtained are useful for design guidance and performance analysis of the hybrid air conditioning system.

• 한국임상수의학회지
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• 제36권1호
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• pp.42-45
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• 2019

Thromboelastography (TEG) analysis consists of ${\alpha}$, G, K, MA, and R types of values and tests the effectiveness of blood clotting, which can be assessed for platelet function, clotting strength, and fibrinolysis. Canine heartworm diseases caused by Dirofilaria immitis, a vascular nematode, can lead to hyperfibrinolysis and hypercoagulation. In this study, G and MA values showed a statistically significant decrease over time after treatment of heartworm disease. Additionally, the ${\alpha}-value$ showed a high correlation with G, K, MA, and R values. The G value showed a high correlation with K and MA values, while The K value showed a high correlation with MA and R values. This study clearly found a gradual decrease in G and MA values in dogs with heartworm disease over time, both before and after treatment. This suggests that the clot formation time is longer and that the intensity of clot formation is lowered and may improve the risk of thromboembolism in dogs with heartworm disease.

• Journal of Power Electronics
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• 제19권1호
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• pp.220-233
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• 2019

This work aims to study and analyze the various operating modes of universal power converter which is powered by solar and thermoelectric generators. The proposed converter is operated in a DC-DC (buck or boost mode) and DC-AC (single phase) inverter with high efficiency. DC power sources, such as solar photovoltaic (SPV) panels, thermoelectric generators (TEGs), and Li-ion battery, are selected as input to the proposed converter according to the nominal output voltage available/generated by these sources. The mode of selection and output power regulation are achieved via control of the metal-oxide semiconductor field-effect transistor (MOSFET) switches in the converter through the modified stepped perturb and observe (MSPO) algorithm. The MSPO duty cycle control algorithm effectively converts the unregulated DC power from the SPV/TEG into regulated DC for storing energy in a Li-ion battery or directly driving a DC load. In this work, the proposed power sources and converter are mathematically modelled using the Scilab-Xcos Simulink tool. The hardware prototype is designed for 200 W rating with a dsPIC30F4011 digital controller. The various output parameters, such as voltage ripple, current ripple, switching losses, and converter efficiency, are analyzed, and the proposed converter with a control circuit operates the converter closely at 97% efficiency.

• 대한한방내과학회지
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• 제31권2호
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• pp.346-355
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• 2010

Objectives : This study was performed in order to investigate the anti-fibrogenic effect of Acer tegmentosum Maxim. on r at hepatic stellate cell line T6. Materials and Methods : Hepatic stellate Cells (T6) were treated with various concentrations of distilled water Acer teg mentosum Maxim. extract for 24, 48, 72 hours. After the treatment, cell viability, proliferation, procollagen levels, mRNA of AS MA, MMP-2, collagen type 1a2 and IL-6 production were measured using MTT assay, BrdU assay, RT-PCR, procollagen typ e 1 C-peptide EIA kit and murine IL-6 ELISA development kit. Results : Cell viability of HSC-T6 decreased significantly in both 24 hours and 48 hours groups in a dose-dependant man ner. Proliferation of HSC also decreased in the same way. In the RT-PCR, mRNA expression of collagen type 1a2 and ASMA decreased in the groups which were treated with Acer tegmentosum Maxim. for 24 hours. The production of procollagen tended to decrease in a dose-dependant manner in the 24 hours treated group. IL-6 production increased under Acer tegmentosum trea tment in a dose-dependant manner in both 24 and 48 hours groups. Conclusion : These results show the possibility that Acer tegmentosum Maxim. can be an effective remedy for liver fibrosi s and liver cirrhosis.

• Nuclear Engineering and Technology
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• 제52권1호
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• pp.19-26
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• 2020

Small nuclear reactor features higher power capacity, longer operation life than conventional power sources. It could be an ideal alternative of existing power source applied for special equipment for terrestrial or underwater missions. In this paper, a 25kWe heat pipe cooled reactor power source applied for multiple use is preliminary designed. Based on the design, a thermal-hydraulic analysis code for heat pipe cooled reactor is developed to analyze steady and transient performance of the designed nuclear reactor. For reactor design, UN fuel with 65% enrichment and potassium heat pipes are adopted in the reactor core. Tungsten and LiH are adopted as radiation shield on both sides of the reactor core. The reactor is controlled by 6 control drums with B₄C neutron absorbers. Thermoelectric generator (TEG) converts fission heat into electricity. Cooling water removes waste heat out of the reactor. The thermal-hydraulic characteristics of heat pipes are simulated using thermal resistance network method. Thermal parameters of steady and transient conditions, such as the temperature distribution of every key components are obtained. Then the postulated reactor accidents for heat pipe cooled reactor, including power variation, single heat pipe failure and cooling channel blockage, are analyzed and evaluated. Results show that all the designed parameters satisfy the safety requirements. This work could provide reference to the design and application of the heat pipe cooled nuclear power source.

• 청정기술
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• 제29권4호
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• pp.255-261
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• 2023

파워반도체는 전력의 변환, 변압, 분배 및 전력제어 등을 감당하는데 사용되는 반도체이다. 최근 세계적으로 고전압 파워반도체의 수요는 다양한 산업분야에 걸쳐 증가하고 있는 추세이며 해당 산업에서는 고전압 IGBT 부품의 최적화 연구가 절실한 상황이다. 고전압 IGBT개발을 위해서 wafer의 저항값 설정과 주요 단위공정의 최적화가 완성칩의 전기적특성에 큰 변수가 되며 높은 항복전압(breakdown voltage) 지지를 위한 공정 및 최적화 기술 확보가 중요하다. 식각공정은 포토리소그래피공정에서 마스크회로의 패턴을 wafer에 옮기고, 감광막의 하부에 있는 불필요한부분을 제거하는 공정이고, 이온주입공정은 반도체의 제조공정 중 열확산기술과 더불어 웨이퍼 기판내부로 불순물을 주입하여 일정한 전도성을 갖게 하는 과정이다. 본 연구에서는 IGBT의 3.3 kV 항복전압을 지지하는 ring 구조형성의 중요한 공정인 field ring 식각실험에서 건식식각과 습식식각을 조절해 4가지 조건으로 나누어 분석하고 항복전압확보를 위한 안정적인 바디junction 깊이형성을 최적화하기 위하여 TEG 설계를 기초로 field ring 이온주입공정을 4가지 조건으로 나누어 분석한 결과 식각공정에서 습식 식각 1스텝 방식이 공정 및 작업 효율성 측면에서 유리하며 링패턴 이온주입조건은 도핑농도 9.0E13과 에너지 120 keV로, p-이온주입 조건은 도핑농도 6.5E13과 에너지 80 keV로, p+ 이온주입 조건은 도핑농도 3.0E15와 에너지 160 keV로 최적화할 수 있었다.

• Restorative Dentistry and Endodontics
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• 제27권1호
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• pp.77-86
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• 2002

Current composites are made with dimethacrylate monomers and silane-treated silica microfillers, either alone or with silane treated glass fillers The main reasons for clinical failure of dental composites are secondary caries, wear and fracture. Most of practitioner want to get a composite which is more tougher under occlusal stress, less polymerization contraction, and better handling properties in application clinically. The aim of this study was to investigate the influence of resin matrix with various flows on the physical proper-ties such as fracture toughness and degree of conversion of the experimental resins. It was hypothesized that flexible or tough resin composites can be designed by judicious choice of monomer composition Various flow resin matrices containing Bis-GMA, UDMA, and TEG-DMA were made by altering the pro-portion of the monomers. After the unfilled resins were light-cured for different light intensity, the fracture toughness(K$_{1c}$) was measured according to ASTM standard using the single edge notched geometry, and degree of conversion(DC) was measured by FTIR. And experimental composites were formulated with variations in the proportion of silanated quartz and strontium glass fillers as 60, 75, and 77wt%. Also, the physical properties of composites with various filer contents were evaluated as same manner. All resulting data were compared by ANOVA/Tukeys test at 0.05 level. The results were as follows; 1. The degree of conversion of high flow resin containing less Bis-GMA was higher than that of low flow unfilled resin 2. While the degree of conversion of unfilled resin was increased according to light intensity for polymerization, there was no significant increase with moderate and high light intensity. Also, the fracture toughness was not increased by high light intensity. 3. The fracture toughness was high in the low flow unfilled resin containing higher contents of Bis-GMA. 4. There was a significant increase for fracture toughness and a tendency for degree of conversion to be reduced when the content of fillers was increased. 5. In the experimental composites, the flow of resin matrix did not affected on the fracture toughness, even, which was decreased as increase of viscosity. These results showed that the physical properties of a dental composite could be attributed to the flow of resin matrix with relative content of monomers. Specific combination of resin monomers should be designed to fulfil the needs of specific indication for use.