• Journal of Soil and Groundwater Environment
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• v.9 no.2
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• pp.1-10
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• 2004

The purpose of this study is to evaluate a laboratory test on arsenic reduction efficiency for ARD (Acid Rock Drainage) using limestone and apatite, and to design an apatite drain system. As a result of the laboratory test, results of this study show that pH, arsenic removal ratio, and dissolution amount of limestone ＆ apatite are inversely proportional to flow rates, and apatite removes 100％ of arsenic at 0.6 ml/min/kg flow rate. It is supposed that dissolution rate of apatite is ten times higher than that of limestone. The arsenic compounds are assumed to be Johnbaumnite, and/or Ca-arsenic hydrate. According to the results of the laboratory test, apatite drain system is designed as follow; Sixty two tons of apatite will be needed per one year and six months, and the precipitates will be removed from the precipitation pond per 3 months.

• Journal of Korean Society of Environmental Engineers
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• v.29 no.12
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• pp.1345-1352
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• 2007

To predict the effects of nutrient releasing on the water quality of Namyang Reservoir, nutrient releasing rates from sediments in oxic and anoxic conditions were estimated in a small microcosm. Organics and nitrogens were not released. The releasing pattern of inorganic phosphate and total phosphorus was depend on the oxygen concentration. The releasing rate of inorganic phosphate and total phosphorus in oxic condition was $1.01\sim2.48$ and $2.14\sim3.54$ mg-P/$m^2$/day, respectively. It was high in the upstream sediments indicating the particles containing easily degradable organic compounds are flowed into the area. Because the depth of Namyang Reservoir at the downstream adjacent to the Dam is $7\sim14$ m, the condition of most area of sediment surface will be oxic. Based on these results, the appropriate counterplans are required to reduce phosphorus release in oxic conditions to control water pollution.

• Culinary science and hospitality research
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• v.15 no.1
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• pp.1-15
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• 2009

This study aims to analyze the difference of eating habits in accordance with Sasang Constitution types. For this study, 249 persons were interviewed and surveyed, classified into Taeyang(8.4%), Soyang (19.3%), Taeeum(26.5%), and Soeum(45.8%). As for taste preference, people of the Taeeum and Soyang body constitution types tended to prefer spicy tastes while those of the Taeyang and Soeum body constitution types preferred sweet tastes. For eating habits, people of the Taeeum and Soyang body constitution types stated that they eat food relatively quickly and eat food until they feel full. They also said they normally overeat when they get stressed. The eating habits for the four groups, there was a significant difference(p<0.05) between body constitution types and eating habits. We hope that our research will provide the food service industry with helpful and new information.

• Journal of IKEEE
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• v.24 no.1
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• pp.170-177
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• 2020

This paper presents an open-fault tolerance control method for active neutral point clamped (ANPC) inverter with high frequency/low frequency (HF/LF) modulation. By applying the ANPC inverter with SiC MOSFETs and Si IGBTs, the system efficiency and performance can be improved compared to a Si-based inverter. HF/LF modulation is used for a megawatt-scale inverter to minimize the commutation loop. The open-switch failure in megawatt-scale inverter causes severe damage to load and huge expenses when the inverter has been shut-down. The proposed tolerance control of open-switch failure provides continuous operation and improved reliability to the ANPC inverter. The effectiveness of the proposed fault tolerance control is verified by simulation results.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.15 no.1
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• pp.90-97
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• 2001

A high frequency resonant inverter consisting of iliree unit Half-Bridge serial resommt inverter used as power source of induction heatmg at high frequency is presented in this paper. As a output [Dwer control strategy, sequencial time-sharing gate contml methcd is applied. This methcd is TDM(Time Division Multiplexing), which is broadly used with digital and analog signals transmission in communication system 1be analysis of the proposed circuit is generally described by using the normalized pararmenters. Also, the principle of basic operating and the its characteristics are estimated by the parameters such as switching frequency, load resistance. Also, according to the calculated characteristics value, a method of the circuit design and operating characteristics of the inverter is proposed. This paper proves the validity of theoretical analysis through the Pspice. This proposed inverter show that it can be practically used in future as power source system for induction heating application, DC-DC converter etc. r etc.

• Journal of the Korean GEO-environmental Society
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• v.15 no.12
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• pp.5-13
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• 2014

In this study, exfoliated vermiculite (EV) coated with glycerol was tested for its abiility to remove phosphorus in aqueous solution. The glycerol modified vermiculite (GS) was prepared with EV/glycerol ratio of 1/4 where glycerol contained 4 mol% $H_2SO_4$ and heated until designated temperature. GS heated at $380^{\circ}C$ showed that the specific surface area was $53.1m^2/g$ and mass loss due to oxidation of carbon was maximum from TGA analysis. Removal of phosphorus using GS heated at $380^{\circ}C$ was well explained by Langmuir isotherm model and maximum sorption capacity of 714.3 mg/kg is comparable or greater than those of other clay orignated sorbents for phosphorus.

• The Transactions of the Korean Institute of Power Electronics
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• v.15 no.1
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• pp.52-59
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• 2010

The conventional CCFL (Cold Cathode Fluorescent Lamp) inverter used in the backlight unit for LCD-TV, composed of the three power stage, can degrade the whole power conversion efficiency. In this paper, a novel scheme to drive the CCFL, composed only of the two power stage without using a dc/dc power stage, is proposed to enhance the whole power conversion efficiency. By adopting the proposed "4-in-1 Transformer", the current balance and the simultaneous ignition among the four CCFL lamp are assured with the one inverter circuit. The proposed scheme features the simple circuit structure, which can save the volume and the cost in the LCD backlight unit. Design considerations are discussed and design procedures are derived. Experimental results of the proposed scheme for 40" LCD-TV are presented to confirm the theoretical analysis.

• Survey Research
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• v.10 no.1
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• pp.155-168
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• 2009

As an efficient sampling design, stratified random sampling is often used when auxiliary information is available at the designing stage. Although one - per - stratum design is an efficient design that can be used when many auxiliary variables are available, it does not provide any unbiased variance estimator. With a two - per - stratum sample in which two elements are selected from each stratum, it is possible to obtain an unbiased variance estimator. However the loss of efficiency could be significant if any important stratification variable is missed. In this study, we investigated a sampling design that uses the all given auxiliary information and also permits an unbiased variance estimator suggested by Park and Fuller(2008). Through a simulation study, we compared several stratified random sampling and systematic sampling design. We also applied the proposed stratified sampling designs to 2007 youth panel data.

• The Transactions of the Korean Institute of Power Electronics
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• v.3 no.1
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• pp.1-7
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• 1998

Due to the increase in capacity of auxiliary machinery in power plant, the importance of energy saving has been greatly emphasized. If the speed of fans or pumps is controlled in accordance with the variation of load, large electric energy can be saved. Large capacity inverter, 2MVA GTO inverter, has been developed by operating two of 1MVA unit inverters in parallel. The parallel operation of the unit inverter is accomplished through two output transformers of which the secondary windings are connected in series. The system is composed of one control cubicle, one rectifier cubicle and 2 unit inverter cubicles. This inverter system was applied to the sea water lift pump(SLP) driven by a 6.6KV 1500KW induction motor in Seo-Inchon power plant to save the electric energy. The parallel operation of inverters by 180 degrees apart in switching frequency helps to reduce the harmonic components.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.2
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• pp.75-81
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• 2005

The GNUnet in P2P system have solved an anonymous(publisher, storer, demander); a service of condition equal for peer. The GNUnet for an anonymous has separated a file and dispersed to the network. But, the 1Kbyte block size of the GNUnet is a creation of many additional block. I and R block has created with indirect point of D block The waste of I and R block appeared to 4% of the original file and the additional network traffic for the block transmission. To resolve the problems, this paper proposes an new scheme of file splitting distribution using P2P networks with the new GNUnet protocol, The GNUnet support minimization of the additional block and for a network traffic. It proposed an efficiency improvement of encording block and routing algorithm.