• Journal of the Korean Magnetic Resonance Society
• /
• v.4 no.2
• /
• pp.82-90
• /
• 2000

Photoinduced charge separation of alkylphenothiazines in molecular assemblies such as positively, negatively and neutrally charged micelle interface results in the paramagnetic phenothiazine cation radical. This was studied as a model system for the light energy conversion into chemical energy. The photoproduced phenothaizne cation radical was identified and its amount was quantized with electron spin resonance (ESR). The microenvironment of photoproduced cation radical was studied with pulsed-ESR. Such a charge separation is enhanced by the optimization of various structural factors of the molecular assemblies. The structural factors of molecular assemblies have focused on the interface charge, interface structure with different headgroups and interfacial perturbation by disolving interface active organic additives.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.4 no.4
• /
• pp.46-57
• /
• 1996

The direct injection stratified charge(DISC) engine enhances the fuel tolerance and the antiknock tendency. This enhanc3d antiknock tendency allows use of a higher compression ratio which results in higher thermal efficiency. But its actual utilization is prevented by high emission combustion time and wall quenching will be the main causes of increasing unburned hydrocarbons in DISC system. In order to solve this problem, small aount of hydrogen was added to the charging air or injected fuel. The effects of hydrogen addition were examined experimentally by radial fuel injection using a pancake-type constant volume bomb. In case of the hydrogen addition to the charge of air, the combustion the amount of hydrogen. In case of the hydrogen addition to the fuel, the combustion pressure was significantly increased.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.10 no.2
• /
• pp.66-72
• /
• 2002

A premixed charge compression ignition engine is experimentally investigated for the reduction of NOx and smoke emissions from diesel engines. In this study, the premixed fuel is injected into the intake manifold to form homogeneous pre-mixture in the combustion chamber and then this pre-mixture is ignited by small amount of diesel fuel directly injected into the cylinder. In the premixed charge compression ignition engine, NOx and smoke concentrations of the exhaust emissions were reduced simultaneously as compared with the conventional diesel engine. But HC emission was increased with the increase of premixed ratio. Also, when EGR system was applied to the PCCI diesel engine, the effect of EGR rate on the combustion characteristics and the exhaust gas emissions was discussed.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.10 no.2
• /
• pp.9-14
• /
• 2002

A homogeneous premixed charge compression ignition engine has been experimentally studied far the reduction exhaust emissions of diesel engines. In this study, the gasoline fuel is injected into the intake manifold to from homogeneous pre-mixture in the combustion chamber and then this pre-mixture is ignited by small amount of diesel fuel directly injected into the cylinder. In the premixed charge compression ignition engine, NOx and smoke concentration of the exhaust emissions were reduced simultaneously as compared with the conventional diesel engine. The combustion characteristics of premixed charged diesel engine such as the power output, the rate of heat release, and the other characteristics are discussed.

• Bulletin of the Korean Chemical Society
• /
• v.31 no.12
• /
• pp.3675-3678
• /
• 2010

In-situ X-ray absorption spectroscopy (XAS) was used to elucidate the structural variation of $\alpha-MoO_3$ electrode upon discharge/charge reaction in a lithium ion battery. According to the XAS analysis, hexavalent Mo atoms in $\alpha-MoO_3$ framework are reduced as the amount of intercalated lithium ions increases. As lithium de-intercalation proceeds, most of pre-edge peaks are restored again. However, according to the Fourier transforms of the extended X-ray absorption fine structure (EXAFS) spectra, lithium de-intercalation reaction is partially irreversible upon the charge reaction, which is one of the main reasons why the capacity of $\alpha-MoO_3$ electrode decreases upon successive discharge/charge cycles.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.15 no.8
• /
• pp.661-666
• /
• 2003

Constant area expansion devices such as capillary tubes, short tube orifices are being gradually replaced with electronic expansion valves (EEVs) because of increasing focus on comfort and energy conservation. In this study, the performance of a water-to-water heat pump as a function of refrigerant charge is investigated in steady state, cooling mode operation with expansion devices of a capillary tube and an EEV. The performance of the capillary tube system varies drastically according to the change of refrigerant charge amount and inlet temperature of the secondary fluid in the condenser. Cooling capacity and COP of the EEV system show little dependence on the refrigerant charge, while those are strongly dependent on the secondary fluid temperature at the condenser inlet. In general, for a wide range of operating conditions the EEV system shows much higher performance as compared with the capillary tube system. The performance of the EEV system can be optimized by adjusting EEV opening to maintain a constant superheat at all test conditions.

• Journal of Distribution Science
• /
• v.14 no.10
• /
• pp.93-107
• /
• 2016

Purpose - This study aims to derive directions and implications for improving performance in operating agrifood export organizations by identifying significant performance impact factors. Research design, data, and methodology - A seemingly unrelated regression (SUR) model was estimated using data from a survey conducted among 120 exporters including 16 leading export organizations. In the SUR estimation, the export volume and price are used as dependent variables and securing the quantity of products ordered and exported, quality management, and marketing activities are considered as explanatory variables for the operation performance. Results - The amount of farmer education, the manpower in charge of marketing, and the interaction terms between whether or not they belong to a leading export organization and the item dummy for mushrooms have a significant impact on the export volume where the export volume is specified as a dependent variable. The export volume is greater with a greater amount of farmer education and greater manpower in charge of marketing from the perspective of quality management. When the export price is estimated as a dependent variable, the manpower in charge of marketing is shown to have a significant impact on the export price. Conclusions - The government needs to strengthen its support of the performance of agrifood export organizations. The analysis indicates that the education of and consulting with farmers, and the manpower number in charge of marketing are key factors in the operation performance of export organizations. Therefore, supporting the export organizations in expanding their human resources in charge of marketing can increase the export volumes for agrifoods. Given, however, that the export volume associated with joint payments, human resources specialized in quality management, and the amount of participation in export exhibitions are not significant factors, it is essential to improve the supporting policies for those areas. The manpower in charge of marketing from the perspective of marketing has a significant impact on both the export volume and export price. Thus, we identify this as the most important category that should be supported to enhance performance in export organizations.

• International Journal of Air-Conditioning and Refrigeration
• /
• v.16 no.3
• /
• pp.77-82
• /
• 2008

For heat pumps used in a cold region, it is very important to obtain appropriate heating capacity. Several studies using a variable speed compressor and an additional heater have been performed to enhance heating capacity at low ambient temperatures. However, for outdoor temperature conditions below $-15^{\circ}C$, it is still difficult to obtain enough heating capacity above the rated value. In recent studies, the application of gas injection technique into a two-stage heat pump yielded noticeable heating performance improvement at low temperature conditions. In this study, the heating performance of a two-stage gas injection heat pump with a rated capacity of 3.5 kW was measured and analyzed by varying refrigerant charge amount and EEV opening at the standard heating condition. The heating performance of the two-stage gas injection heat pump was compared with that of a two-stage non-injection heat pump. The heating capacity and COP of the two-stage gas injection heat pump were improved by 2-10% at the optimal charging condition over those of the two-stage non-injection heat pump.

• Proceedings of the KIEE Conference
• /
• 2004.07c
• /
• pp.1661-1663
• /
• 2004

The effect of the triblock copolymer poly[styrene-b-(ethylene-co-butylene)-b-styrene](SEBS) on the formation of space charge of immiscible low density polyethylene/polystyrene(LDPE/PS) blends was investigated. The amount of charge accumulated in the 70/30(wt%) LDPE/PS blends decreased when the SEBS content increased up to 10 wt%. For compatibilzed and uncompatibilized blend, morphological observation showed that the addition of SEBS results in the domain size reduction of the dispersed PS phase and a better interfacial adhesion between LDPE and PS phases. The location of SEBS at a domain interface enables charges to migrate from one phase to the other via domain interface and therefore, results in a significant decrease in the amount of space charge for the LDPE/PS blends with SEBS.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.31 no.8
• /
• pp.694-701
• /
• 2007

The applications of a transcritical $CO_2$ cycle into water heaters show advantages over conventional systems in the respect of power consumption and heating efficiency because the $CO_2$ cycle has a high compressor discharge temperature. Besides, the heating performance of the transcritical $CO_2$ cycle can be improved by optimizing operating conditions. In this study, the heating performance of a variable speed $CO_2$ heat pump was measured and analyzed by varying refrigerant charge amount, EEV opening, compressor frequency and outdoor temperature. As a result, the optimum normalized charge for heating was 0.226. The COPs at the compressor frequencies of 40, 50 and 60 Hz were 2.94, 2.75 and 2.25, respectively. The heating performance of the $CO_2$ cycle with charge amount was more sensitive than the cooling performance. Moreover, the heating performance was improved significantly by optimizing of compressor frequency and EEV opening.