• Korean Journal of Soil Science and Fertilizer
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• v.24 no.4
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• pp.241-247
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• 1991

Electric charge characteristics of volcanic ash soils in Cheju Island were investigated. For this study, soils of toposequence distributed along the sourthern slope of Mt. Halla, and the major soil groups such as dark brown soils, very dark brown soils, black soils, and brown forest soils were collected and analyzed for extratable acidity, KCl ext. Al, CEC, base saturation, permanent charge and variable charge, etc.. Weolpyeong and Yongheung soils developed on the lower elevations have high $NH_4OAc$ ext. bases, permanent charge and base saturation, and relatively low ext. acidity, CEC and variable charge. For other soils, whose colloidal fractions are dominated by allophane or Al-humus complexes, ext. acidity, CEC, variable charge, and variable charge ratio were very high, and $NH_4OAc$ ext. bases, permanent charge, and base saturation were very low. These trends were especially prominant in the surface. horizons of black soils and brown forest soils dominated by Al-humus complexes. Ext. acidity, CEC($NH_4OAc$), CEC(sum of cations), and variable charge strongly correlated with pyrophosphate ext. carbon. Very dark brown soils and cinder cone soils dominated by allophane showed low KCl ext. Al and relatively high pH, despite their very low base saturation.

• International Commerce and Information Review
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• v.10 no.4
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• pp.513-532
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• 2008

The purpose of this study was to analyze which factors have had impacts on extension export insurance charge of Korean export insurance. In order to attainment of this study, an empirical study was proceeded. The export insurance charge was hired as the dependent variable and export insurance premium, insurance compensation charge, export insurance collection charge and export insurance fund were used as independent variables. Data was used for estimation are the annually data from 1969 to 2007. From results of this analysis, we find the hired variables have highly correlation among them and the most influential factor turns out to be export insurance fund. Main results of this study was as follows : i) The export insurance fund must be increased immediately. ii) It is necessary that Korea Export Insurance Corporation give their attention to the compensate amount of export insurance compensation on specific insurance item. iii) It is necessary that Korea Export Insurance Corporation extension the collection efforts of the export insurance. iv) A reasonable raising of export insurance premium need to be done.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.286-291
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• 2001

This paper describes an optimal scheduling for ice slurry systems for energy cost saving. The optimization technique applied in the study is the dynamic programming method, for which the state variable is the storage in the ice storage tank and the control variable is the state of chiller's on-off switching. Though the costs during charge period is included in optimization by taking the average cost of ice per hour for slurry making, the time horizon for the simulation is limited building cooling period because accurate charge rate from the ice maker into the ice storage tank cannot be estimated during the charge period. In the operating simulation after optimizing procedure, energy consumption and operating cost for the optimal control are calculated and compared with them for a conventional control with one case of cooling load profile.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.412-415
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• 2008

It is known that the address discharge delay time during an address period strongly depends on the wall charge leakage. It was observed that the wall charge leakage during an address period is related to both the address width and the ambient temperature. Accordingly, the effects of address electrode width on the address discharge and wall voltage variation during an address period were examined under variable temperatures.

• Proceedings of the KIPE Conference
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• 2016.07a
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• pp.337-338
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• 2016

This paper introduces a novel dual Full-Bridge LLC(FBLLC)resonant converter for CC/CV Charge of the Battery for Electric Vehicles. One full-bridge LLC resonant converter operates with a fixed-resonant network and the other operates with a variable-resonant network for CC and CV mode operations. The proposed converter can achieve ZVS for all the primary switches and exhibits a highefficiency characteristics like aconventional single FBLLC resonant converter. In addition, the variable-resonant network helps minimize the switching-frequency variation. The dual structure makes the proposed converter possible to achieve ZVS and nearly ZCS for all the primary switches in CC mode operation. Since the proposed converter can operate at a fixed frequency in CV mode, it can minimize the circulating current and achieve nearly ZCS. A 6.6 kW prototype converter is implemented to verify the validity of proposed converter and the maximum efficiency of 98.3% was achieved.

• Industrial Engineering and Management Systems
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• v.11 no.2
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• pp.183-187
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• 2012

In this paper, we study the fixed charge transportation problem with uncertain variables. The fixed charge transportation problem has two kinds of costs: direct cost and fixed charge. The direct cost is the cost associated with each source-destination pair, and the fixed charge occurs when the transportation activity takes place in the corresponding source-destination pair. The uncertain fixed charge transportation problem is modeled on the basis of uncertainty theory. According to inverse uncertainty distribution, the model can be transformed into a deterministic form. Finally, in order to solve the uncertain fixed charge transportation problem, a numerical example is given to show the application of the model and algorithm.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.1
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• pp.38-47
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• 2001

The operation characteristics of variable conductance heat pipe(VCHP) were numerically investigated by using 1-dimensional diffuse-front model. For different boundary conditions, the amount of non-condensible gas charge and dimension of gas reservoir were obtained by iterative calculation. It is found that the amount of non-condensible gas charge and dimensions of gas reservoir have an effect on the temperature control of condenser for the given operating condition of VCHP. The numerical results show that VCHP has an excellent capability of temperature control when subjected to a change in the heat input.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.7
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• pp.833-839
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• 2018

This paper presents an analysis and the methodology of optimal operation strategy of the ESS(Energy Storage System) for reduce electricity charges. Electricity charges consist of a basic charge based on the contract capacity and energy charge according to the power usage. In order to use electrical energy at minimal charge, these two factors are required to be reduced at the same time. QP(Quadratic Programming) is appropriate for minimization of the basic charge and LP(Linear Programmin) is adequate to minimize the energy charge. However, the integer variable have to be introduced for modelling of different charge and discharge efficiency of ESS PCS(Power Conversion System), where MILP(Mixed Integer Linear Programming) can be used. In this case, the extent to which the peak load savings is accomplished should be assumed before the energy charge is minimized. So, to minimize the electricity charge exactly, optimization is sequentially performed in this paper, so-called the Two Stage Hybird optimization, where the extent to which the peak load savings is firstly accomplished through optimization of basic charge and then the optimization of energy charge is performed with different charge and discharge efficiency of ESS PCS. Finally, the proposed method is analyzed quantitatively with other optimization methods.

• New & Renewable Energy
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• v.7 no.4
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• pp.30-36
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• 2011

The objective of this study is to investigate the effects of the refrigerant charge amount on the performance of a water-to-water ground source heat pump with a variation of compressor speed and the secondary fluid flow rate. The water-to-water ground source heat pump was tested by varying refrigerant charge amount from -40% to 20% of full charge. Compressor speed was changed from 30 Hz to 75 Hz and the secondary fluid flow rate was adjusted from 6 LPM to 14 LPM. For all test conditions, EWTs of an indoor heat exchanger and an outdoor heat exchanger were maintained at standard conditions of ISO 13256-2. The slope of the COP with the variation of charge amount is much steeper at undercharged conditions than that at overcharged conditions. For all compressor speed, the variation of the system performance according to charge amounts showed the similar trends. However, the optimum charge amount of the system increased a little with an increment of compressor speed. When the secondary fluid flow rate decreased, the system was optimized at higher refrigerant charge amount conditions.

• Journal of Biosystems Engineering
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• v.31 no.2 s.115
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• pp.108-114
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• 2006

This study was conducted to design and fabricate a controller for variable-rate application of granular fertilizer based on physical and chemical information, to analyze the performance of the controller and characteristics of a discharger. The result of the study are summarized as follows: 1. The charge ratios of discharger by accumulation heights of fertilizer in hopper were examined, and the variations in charge ratio were $72.58{\sim}93.33%$ and $63.14{\sim}94.42%$ for the fertilizers Super 21 and Sinsedae, respectively. The charge ratio also decreased as the rotational speed of discharger increased. 2. The coefficient of variation of discharge amount by rotational speed and discharge time of discharger were in the range of $2.94{\sim}11.23%$ and $2.82{\sim}10.80%$ for the fertilizer of Super 21 and Sinsedae. Except the rotational speed of 12 rpm, the coefficient of variation for discharge amount were relatively small with 4% more or less 3. In order to evaluate the rotational speed of discharger, the control signal in the range of $0{\sim}5V$ was subdivided into the 50 steps by 0.1V. The regression equation for the rotational speed of discharger was Y=55.984X-79.174(X: input voltage, V, Y: discharger speed, RPM) and the $R^2$ was 0.99. 4. In order to evaluate the performance of the controller for variable-rate application of granular fertilizer, settling time to unit step input was examined. The settling time varied from 0.8sec to 1.4 sec.