• Journal of Power Electronics
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• v.2 no.2
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• pp.77-87
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• 2002

The purpose of this paper is to improve power conversion efficiency of three-phase soft-switching voltage-source inverter with an auxiliary resonant dc link (ARDCL) snubber circuit. Firstly, the operation principle of ARDCL snubber circuit is described. Secondly, this paper proposes an effictive generation method of zero voltage vector for three-phase voltage-source soft-switching inverter in power losses in which power losses in the ARDCL snubber circuit can be reduced. In particular, zero voltage holding interval in the inverter DC busline can be controlled due to the new generation scheme of zero voltage vector. Thirdly, a simulator for power loss analysis for power loss characteristics based on actual system, is developed. the validity of developed. The validity of developed simulator of proved with experimental results. Finally, power efficency of three-phase inverter is estimated according to high carrier frequency by using the simulatior.

• The Journal of the Korea institute of electronic communication sciences
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• v.16 no.2
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• pp.241-246
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• 2021

In this paper, hydrogenated amorphous silicon(a-Si:H) grating coupler with distributed Bragg reflector(DBR) is proposed to achieve high-efficiency nanophotonic radiator for Light Detection and Ranging(LiDAR) application. The DBR reduces downward leakage of the optical field below the grating region. As a result, the far-field intensity shows about 1.4 times stronger, compared to the common grating coupler without the DBR.

• Journal of the Korean Society for Precision Engineering
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• v.10 no.2
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• pp.178-189
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• 1993

Engineering ceramics have some excellent properties as the material for the mechanical components. It is, however, very difficult to grind ceramics with high efficiency because of their high strength, hardness and brittleness. In this paper experiments are carried out to obtain the effect of "In-process dressing" to grind the Engineering ceramics with high efficiency. To save running time for dressing process and obtain restraint effect of diamond grain wear, "In-process dressing" system usint WA stick type honing stone is proposed. Representative High Strength Engineering ceramics A1$_{2}$O$_{3}$ and Si$_{3}$N$_{4}$are ground with diamond wheel. Also bending strengrh test is carried out to check upward tendancy of mecahnical properties as the result of machining defact restraint through the grinding maching method using "In-process dressing" process. Some results obtained in this study provide useful information to attain the high efficency grinding and the high mechanical properties of Engineering ceramics.rties of Engineering ceramics.

• Journal of Korea Water Resources Association
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• v.32 no.5
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• pp.525-535
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• 1999

An optimal unit commitment model for efficient management of water and energy resources in a basin using combined mixed integer programming is developed. The combined mixed integer programming model is able to solve the inconsistency problem that may occur from mixed integer programming models. The technique which enables the use of conditional constraints and either-or constraints in the linear programming is also suggested. As a result of applying the combined mixed integer programming model to Lower Colorado River Basin in United States. the basin efficiency is decreased by 1.53% from the results of the mixed integer programming, while it is increased by 0.67% from the results of the historical operation. It is found that the decreased allowable error between power supplies and demands in the combined mixed integer programming causes the decreased basin efficiency.

• The Korean Journal of Food And Nutrition
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• v.13 no.4
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• pp.312-318
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• 2000

This study was conducted to investigate the effects of soybean germ of Glycin max Merrill on the improvement of lipids in the serum of cholesterol supplemented diet induced dietary hyperlipidemic rats fed for 4 weeks. The experiment diet was mixed with 0.75% cholesterol recieved a basic diet mixed with 0.75% cholesterol. No significance differences in efficency of food, liver kidney and heart. Concentration of total cholesterol and LDL cholesterol in serum was significantly lower in the methanol extracts of soybean sprout than the cholesterol supplemented diet group. In the ratio of HDL-cholesterol concentration to total cholesterol concentration, the methanol extracts of soybean sprout administration group was higher percentage than the ocher groups. Atherosclerotic index was lower in the methanol extracts of soybean sprout group than in the cholesterol group. Concentration of phospholipid in serum was more decreased in the methanol extracts of soybean sprout group than in the cholesterol diet group. From these results, the methanol extracts of soybean sprout were effective on the improvement of the lipid compositions in the serum of high fat diet induced dietary hyperlipidemic rats.

• THE JOURNAL OF KOREAN ORIENTAL ONCOLOGY
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• v.2 no.1
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• pp.75-90
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• 1996

This experiment was designed to study the antitumor effects and Activity of Natural Killer Cell of semen Tiglii plus Rhizoma Rhei. The cytotoxic and antitumor effects were evaluated on human cell lines(A549, Caki-1, LL2, Sarcoma 180, NIH/3T3) after exposure to prebrewed Semen Tiglii plus Rhizoma Rhei water extract 0.1, 0.2, 0.4, 0.8, 1.6mg/ml using in MTT assay, LDH, colony forming efficency and SRB assay which were regarded as a valuable method for cytotoxic and antitumor effects of unknown compound on tumor cell lines. The results obtained in this studies were as follows. 1. From the result of MTT assay, the cytotoxicity of ST(生巴豆霜), ST+RR(生巴豆霜加大黃) were concentration-dependently increased in both group of the ST and ST+RR, the cytotoxicity of ST+RR(生巴豆霜加大黃) was similar to that of ST(生巴豆霜). 2. From the result of LDH, the cytotoxicity of ST, ST +RR were concentrati -on-dependently increased in both group of the ST and ST+RR, the cytotoxicity of ST+RR was similar to that of ST. 3. The antitumor effect on A549 tumor cell from the result of colony forming efficiency showed the inhibitory effect on the growth in both group of the ST and ST+RR, the inhibitory effect on growth was low slightly in the ST+RR. 4. From the result of SRB assay, the antitumor effect on caki-1 tumor cell of ST, ST+RR showed the inhibitory effect on the growth in both group of the ST and ST+RR, the antitumor effect of ST+RR was similar to that of ST. 5. Median survival time and increased life span were increased slightly in both group of the ST and ST+RR. 6. The inhibitory effect on the growth of Sarcoma 180 and Lewis lung carcinoma tumor cell were increased slightly in both group of the ST and ST+RR. 7. The activity of NK cell was increased in the ST+RR.

• Journal of the Korea Organic Resources Recycling Association
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• v.21 no.3
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• pp.74-81
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• 2013

In this study, the separation efficiency of wind power selector (the direction of the air flow of the air to perform gravity separation method) of municipal solid waste which was landfilled was investigated to reduce amount of waste that is designed to increase the recycling rate of wastes for the ANSYS CFX Program's numerical methods with wind through the separator. When a suction device designed to suction 1000mL of a plastic bag, the separation efficiency was 100% and when the wind speed was 0.9 m /sec or more and when the wind speed was 1.6 m / sec or more, the efficiency of plastic bottles in a mixture of 500mL and 1500mL plastic bottle waste was 100% and the aluminum screening efficiency of 250mL aluminum can was 100 % when the wind speed was 2.3 m / sec. In the last, 5mm thick compressed aluminum can efficiency was 90 % when the wind speed was 2.4 m / sec.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.501-504
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• 2011

In this study, structural design of the propeller blade for turboprop aircraft was performed. The propeller shall have high strength to get the thrust to fly at high speed. The high stiffness and strength carbon/epoxy composite material was used for the major structure and skin-spar-foam sandwich structural type was adopted for improvement of lightness. As a design procedure for the present study, firstly the structural design load was estimated through investigation on aerodynamic load and then flanges of spars from major bending loads and the skin from shear loads were preliminarily sized using the netting rule. In order to investigate the structural safety and stability, stress analysis was performed by finite element analysis code MSC. NASTRAN. Finally, it is investigated that designed blade have high efficiency and structural safety to analyze of aerodynamic and structural design results.

• Journal of Acupuncture Research
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• v.24 no.5
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• pp.113-125
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• 2007

Objectives : This research was performed to investigate the effect of herbal acupuncture(Raphanus sativus) at Bisu($BL_{20}$) on weight gain, food intake, food efficiency, serum of lipid concentrations, liver function and HDL to total cholesterol ratio of rats fed high fat diet for 5weeks. Methods : Experimental groups were divided into high fat diet group(Control), high fat diet and saline in $BL_{20}$ treated group(Saline), high fat diet and Raphanus sativus-herbal acupuncture in $BL_{20}$ treated group(RHA-1, 0.058mg/ml/g), high fat diet and Raphanus sativus-herbal acupuncture in $BL_{20}$ treated group(RHA-2, 0.029mg/ml/g), high fat diet and Raphanus sativus-herbal acupuncture in $BL_{20}$ treated group(RHA-3, 0.011mg/ml/g), Herbal acupuncture was bilaterally treated at 0.2cc per 4days, total 14 times in 56days. Results : Body weight and food efficiency were decreased in saline, RHA-1, RHA-2. Feed intake was increased in saline, RHA-1, RHA- 2, RHA- 3. The level of serum total cholesterol was decreased in saline, RHA-1. The level of serum HDL-cholesterol, LDL-cholesterol were not significant. The level of serum triglyceride, Total Bilirubin were decreased in saline, RHA-1, RHA-2, RHA-3.The level of serum AST was decreased in RHA-1. But the level of serum ALT was increased in RHA-1. The level of atherogenic index was decreased in saline, RHA-1. The level of HTR was increased in saline, RHA-1. Conclusions : Raphanus sativus-herbal acupuncture in Bisu($BL_{20}$) can control body weight, feed intake and feed efficency ratio, total cholesterol, total bilirubin, and prevention cardiovascular risk.

• Magazine of the Korea Concrete Institute
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• v.8 no.3
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• pp.187-195
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• 1996

A finite element formulation based on the CFT(Compression Field Theory), considering the effect of compression softening in cracked concrete, and macro-scopic and rotating crack models etc., was presented for the nonlinear behaviour of structural concrete. Considering the computational efficency and the ability of modelling the post-ultimate behaviour as major concerns, the Incremental displacement solution algorithm involving initial material stiffnesses and the relaxation procedure for fast convergence was adopted and formulated in a type of 8-noded quadrilateral isoparametric elements. The analysis program NASCOM(Non1inear Analysis of Structural Concrete by FEM : Monotonic Loading) developed in this way enables the predictions of strength and deformation capacities in a full range, crack patterns and their corresponding widths, and yield extents of reinforcement. As the verification purpose of NASCOM, the predictions were made for Bhide's Panel(PB21) and Leonhardt's deep beam tests. The predicted results shows somewhat stiff behaviour for the panel test, and vice versa for deep beam tests. More refining process would be necessary hereafter in terms of more accurately simulating the effects of tension-stiffening and compression softening in concrete.