• Proceedings of the Plant Resources Society of Korea Conference
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• 2010.10a
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• pp.20-20
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• 2010

Panax ginseng C.A Meyer is frequently taken orally as a traditional herbal medicine in Asian countries. The major components of ginseng are ginsenoside, which are pharmaceutical activity. The six major ginsenosides, including Rb1, Rb2, Rc, Rd, Re and Rg1 account for 90% of total ginsenosides. Even though the minor ginsenosides, including Rg3, Rh2 and compound K has high pharmacetical activities, the price of minor ginsenosides is too high. Therefore we isolated the gypenoside V and made it converted to minor ginsenosides. In the plant Gynostemma pentaphyllum Makino, gypenosdie V was presented as dominant saponin (content about 2.4%), and was similar to protopanaxadol type ginsenosides such as ginsenoside Rb1. In this study, we confirmed that the coversion of gypenoside V to minor ginsenosides after using the various treatment such as heating, acid treatment, commercial edible enzyme, and lactobacillus. Consequently, we optimizied the transformation of gypenoside V to minor ginsenoside using Thin Layer Chromatography (TLC), High Performance Liquid Chromatography (HPLC), Time-of-flight Mass Spectrometry (LC/TOF/MS).

• Journal of the Korean institute of surface engineering
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• v.48 no.6
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• pp.297-302
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• 2015

Nanocrystalline diamond(NCD) coated aluminium plates were prepared and applied as heat sinks for LED modules. NCD films were deposited on 1 mm thick Al plates for times of 2 - 10 h in a microwave plasma chemical vapor deposition reactor. Deposition parameters were the microwave power of 1.2 kW, the working pressure of 90 Torr, the $CH_4/Ar$ gas ratio of 2/200 sccm. In order to enhance diamond nucleation, DC bias voltage of -90 V was applied to the substrate during deposition without external heating. NCD film was identified by X-ray diffraction and Raman spectroscopy. The Al plates with about 300 nm thick NCD film were attached to LED modules and thermal analysis was carried out using Thermal Transient Tester (T3ster) in a still air box. Thermal resistance of the module with NCD/Al plate was 3.88 K/W while that with Al plate was 5.55 K/W. The smaller the thermal resistance, the better the heat emission. From structure function analysis, the differences between junction and ambient temperatures were $12.1^{\circ}C$ for NCD/Al plate and $15.5^{\circ}C$ for Al plate. The hot spot size of infrared images was larger on NCD/Al than Al plate for a given period of LED operation. In conclusion, NCD coated Al plate exhibited better thermal spreading performance than conventional Al heat sink.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.7
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• pp.732-739
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• 2002

Performance of the applicator for hyperthermia is determined by both the degree of impedance matching and specific absorption rate(SAR) distribution in the surrounding tissue. In this paper, the coaxial-slot antenna using staircasing approximation in the FDTD is analyzed and the coaxial-slot antenna for the hyperthermia improving heating characteristics is designed. The SAR of the coaxial-slot antenna approximated to staircasing and square model is analyzed, and the SAR of staircasing model is compared with Saito's SAR measurement and square model. As a result, the SAR of proposed model exhibited agreement with the Saito's measurement of square model. Ig averaged SAR on the liver caused by proposed antenna in this paper is 195 W/kg, and is about 27.9 % higher than the Saito's antenna 152.5 W/kg, respectively.

• Journal of the Korean Institute of Intelligent Systems
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• v.23 no.2
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• pp.107-112
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• 2013

In the paper, velocity controller of switching module and temperature controller for the high-voltage static var compensator are proposed. Because of the continuous increase in demand for electric power, transmission and distribution facilities of power plant are required. There is a bottleneck problem of transportation routes according to new construction and expansion of power transmission facilities. Therefore there are researches to maximize the utilization of existing facilities and to increase transmission capacity without new construction. The previous static var compensator detects voltage of input circuit of power, switches the SCR directly and generates switching noise. The proposed method increases switching velocity and decreases noise using switching control based on the voltage between both sides of SCR. Also the proposed method enhance the stability using realtime temperature control for heating of the system from increase of switching velocity. We experiment the velocity and temperature control of the proposed high-voltage static var compensator in the real environment and verify the performance of the proposed system by applying in the real field.

• Korean Journal of Construction Engineering and Management
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• v.18 no.1
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• pp.27-36
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• 2017

Ministry of Land, Infrastructure and Transport established Heating and cooling energy conservation plan of apartment for 2017, reducing 90% compared to energy consumption of 1990. Also, at 2015 United Nations Climate Change Conference, the Ministry announced to reduce 37% of estimated $CO^2$ emission(850 million ton) at 2030. To satisfy this, it is urgent to reduce $CO^2$ emission due to the building, which takes majority amount of total $CO^2$ emission, and public interest for the commissioning of intensified building performance is uprising. However, the building commissioning at construction is not enacted, and not activated due to the lackness of promotion and will of general contractor. Furthermore, commissioning is not mandatory for obtaining G-SEED certification. Therefore, this paper describes effectiveness of commissioning with comparison of commissioning evaluation criteria of G-SEED with LEED and BREEAM, to propose making commissioning as mandatory process and drive changes in perception among stakeholders for activation of domestic building commissioning.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.5
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• pp.443-447
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• 2009

Bismuth-antimony-telluride based thermoelectric thin film materials were prepared by metal organic vapor phase deposition using trimethylbismuth, triethylantimony and diisopropyltelluride as metal organic sources. A planar type thermoelectric device has been fabricated using p-type $Bi_{0.4}Sb_{1.6}Te_3$ and n-type $Bi_{2}Te_{3}$ thin films. Firstly, the p-type thermoelectric element was patterned after growth of $5{\mu}m$ thickness of $Bi_{0.4}Sb_{1.6}Te_3$ layer. Again n-type $Bi_{2}Te_{3}$ film was grown onto the patterned p-type thermoelectric film and n-type strips are formed by using selective chemical etchant for $Bi_{2}Te_{3}$. The top electrical connector was formed by thermally deposited metal film. The generator consists of 20 pairs of p- and n-type legs. We demonstrate complex structures of different conduction types of thermoelectric element on same substrate by two separate runs of MOCVD with etch-stop layer and selective etchant for n-type thermoelectric material. Device performance was evaluated on a number of thermoelectric devices. To demonstrate power generation, one side of the device was heated by heating block and the voltage output was measured. The highest estimated power of 1.3 ${\mu}m$ is obtained at the temperature difference of 45 K.

• Journal of Bio-Environment Control
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• v.27 no.4
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• pp.294-301
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• 2018

In winter, thermal screens are widely used to reduce heat loss from greenhouse to save energy. Unfortunately, not much data are available to the farmer to compare thermal screens while selecting the one that meets their specific requirements. Thus, there is a need to investigate the thermal performance of thermal screens. To address this issue, the Building Energy Simulation (BES) model of a hot box was used to calculate the overall heat transfer coefficient (U-value) of the thermal screens. To validate the model, computed and experimental U-values of single-and double-layered polyethylene (PE) material were compared. This validated model was used to predict the U-values of the selected thermal screens under defined weather conditions. We quantified the U-values of each selected material and significant changes in their U-values were noted in response to different weather conditions. Notably, the thermal properties of the tested screens were taken from the previous literature to calculate U-values using the BES model. The U-values of the thermal screens can help researchers and farmers evaluate their screens and make pre-design decisions that suit their investment capabilities.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.11
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• pp.1051-1059
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• 2004

Two phase thermosyphone loop for electronics cooling are designed and manufactured to test its performance under the partial load and low environment temperature conditions. The thermosyphone device has six evaporators connected parallel for the purpose of cooling six power amplifier units (PAU) independently. The heater modules for simulating PAUs are adhered with thermal pad to the evaporator plates to reduce the contact resistance. There are unbalanced distributions of liquid refrigerant in the differently heated evaporators due to the vapor pressure difference. To reduce the vapor pressure differences caused by partial heating, two evaporators are connected each other using the copper tube. The pressure regulation tube successfully reduces these unbalances and it is good candidates for a field distributed systems. Under the low environment temperature operating condition, such as $-30^{\circ}C$, there may be unexpected subcooling in condenser. It leads the very low saturation pressure, and under this condition there exists explosive boiling in evaporator. The abrupt pressure rise due to the explosive boiling inhibits the supplement of liquid refrigerant to the evaporator for continuous cooling. Finally the cooling cycle will be broken. For the normal circulation of refrigerant there may be an optimum cooling air flow rate in condenser to adjust the given heat load.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.703-712
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• 2004

A variant of the magnetoplasma jet engine (magjet) is here proposed for airbreathing flight in the hypersonic regime. As shown in Figure 1, the engine consists of two distinct ducts: the high-speed duct, in which power is added electromagnetically to the incoming air by a momentum addition device, and the fuel cell duct in which the flow stagnation temperature is reduced by extracting energy through the use of a magnetoplas-madynamic (MPD) generator. The power generated is then used to accelerate the flow exiting the fuel cells with a fraction bypassed to the high-speed duct. The analysis is performed using a quasi one-dimensional model neglecting the Hall and ion slip effects, and fix-ing the fuel cell efficiency to 0.6. Results obtained show that the specific impulse of the magjet is at least equal to and up to 3 times the one of a turbojet, ram-jet, or scramjet in their respective flight Mach number range. Should the air stagnation temperature in the fuel cell compartment not exceed 5 times the incoming air static temperature, the maximal flight Mach number possible would vary between 6.5 and 15 for a magnitude of the ratio between the Joule heating and the work interaction in the MPD generator varied between 0.25 and 0.01, respectively. Increasing the mass flow rate ratio between the high speed and fuel cell ducts from 0.2 to 20 increases the engine efficiency by as much as 3 times in the lower supersonic range, while resulting in a less than 10% increase for a flight Mach number exceeding 8.

• Solar Energy
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• v.11 no.3
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• pp.44-52
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• 1991

The benefits of thermal stratification in sensible heat storage systems has been considered and studying by several investigators. In this paper, the basic data which is hard to obtain normally through the experiment were obtainable through the computer simulation. The major objectives of the study were to assess the benefits of stratified storage in residential solar water heating application and to suggest the optimum design parameters. From the computer simulation, following results were obtained. 1. The solar load fraction increases with increasing the number of tank segments. In these simulation, the magnitude of the improvement was about 10%. 2. The solar load fraction increases when the ratio of diameter to height of the tank(H/D) increases to 3, but H/D exceed 3 then, the solar load fraction decreases. In these simulation, the magnitude of the improvement was about 3%. 3. Increasing the collector flow rate slightly improved the performance of the mixed storage system(Node=1). But, for the stratified storage system(Node=N), the solar load fraction increases with decreasing flow rate until the point is reached at which the collector outlet temperature reaches the boiloff limit of $100^{\circ}C$ over some portion of the simulation period.