• Journal of Institute of Control, Robotics and Systems
• /
• v.18 no.9
• /
• pp.854-862
• /
• 2012

The optimal design of batch-storage network by using periodic square wave model provides analytical lot sizing equations for a complex supply chain network characterized as multi-supplier, multi-product, multi-stage, non-serial, multi-customer, cyclic system including recycling and/or remanufacturing. The network structure includes multiple currency flows as well as material flows. The processes are represented by multiple feedstock/product materials with fixed composition which are very suitable for production processes. In this study, transportation processes that carry multiple materials with unknown composition are added and the time frame is changed from single period into multiple periods in order to represent nonperiodic parameter variations. The objective function of the optimization involves minimizing the opportunity costs of annualized capital investments and currency/material inventories minus the benefit to stockholders in the numeraire currency. The expressions for the Kuhn-Tucker conditions of the optimization problem are reduced to a multiperiod subproblem for average flow rates and analytical lot-sizing equations. The multiperiod lot sizing equations are different from single period ones. The effects of corporate income taxes, interest rates and exchange rates are incorporated.

• Proceedings of the KIPE Conference
• /
• 2018.07a
• /
• pp.192-194
• /
• 2018

In this paper a new single-stage ac-dc converter with high frequency isolation and low components count is introduced. The proposed converter is constructed using two interleaved boost circuits in the grid side and non-regulating full bridge in the DC side. An optimized switching is implemented on the two interleaved boost circuits resulting in a ripple-free grid current without a ripple cancellation network; hence very small filter inductors are used. A simple and reliable closed-loop control system is easily implemented, since the phase-shift angle is the only independent variable. Moreover, current imbalance is avoided in the presented topology without current control loop in each phase. The proposed charger charges the battery with a sinusoidal-like current instead of a constant direct current. ZVS turn on of all switches is achieved throughout the operation in both directions of power flow without any additional components.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.23 no.5
• /
• pp.299-304
• /
• 2018

An ideal circuit breaker should supply electric power to loads without losses in a conduction state and completely isolate the load from the power source by providing insulation strength in a break state. Fault current is relatively easy to break in an Alternating Current (AC) circuit breaker because the AC current becomes zero at every half cycle. However, fault current in DC circuit breaker (DCCB) should be reduced by generating a high arc voltage at the breaker contact point. Large fire may occur if the DCCB does not take sufficient arc voltage and allows the continuous flow of the arc fault current with high temperature. A semiconductor circuit breaker with a power electronic device has many advantages. These advantages include quick breaking time, lack of arc generation, and lower noise than mechanical circuit breakers. However, a large load capacity cannot be applied because of large conduction loss. An extinguishing technology of DCCB with polymeric positive temperature coefficient (PPTC) device is proposed and evaluated through experiments in this study to take advantage of low conduction loss of mechanical circuit breaker and arcless breaking characteristic of semiconductor devices.

• Preventive Nutrition and Food Science
• /
• v.8 no.1
• /
• pp.7-12
• /
• 2003

This study examined the effect of pine needle distillate (Pinus densiflora Sieb. et Zucc) on the immune system and hematological parameters. C57BL/6 male mice weighing 20 ~21 g were divided into 3 groups and intraperitonially injected with either 200 $\mu$L of saline (control), 50% diluted (P50) or 100% pine needle distillate (P100) once a day for 24 days. At the end of the experiment, the mice were anesthetized by ether and peripheral blood was collected from the femoral artery and the spleen was excised. Spleen weight decreased significantly (p<0.001) in the pine needle groups compared to the control group. The blood was used for a complete blood count and flow cytometrical analysis after immunofluorescence staining. The pine needle distillate dose-dependently decreased the CD4$^{＋}$/CD8 sup ＋/ ratio (p <0.05), and showed a tendency to increase the mean FSC (forward scatter) values of the CD8$^{＋}$T cells, while decrease the values of the CD4$^{＋}$T cells. There were no significant differences in WBC, RBC and platelet counts among the three groups, but hemoglobin and hemoglobin-related parameters and platelet volume increased and red blood cell volumes decreased with the administration of the pine needle distillate. These results suggest that the pine needle distillate may have immunosuppressive effects.

• KIEE International Transactions on Power Engineering
• /
• v.5A no.3
• /
• pp.228-234
• /
• 2005

This paper presents the evaluation of reactive power pricing through the control of generator voltages under the assumption that the reactive power market has been transformed into the real power market. By applying the concept of economic dispatch, which minimizes the total cost of real power generation to reactive power generation, the algorithm for implementing reactive power pricing is proposed to determine the optimum voltage profiles of generators. It consists of reactive power voltage equation, the objective function that minimizes the total cost of reactive power generation, and linear analysis of inequality constraints in relation to the load voltages. From this algorithm, the total cost of the reactive power generation can be yielded to the minimum value within network constraints as the range of load voltages. This may provide the fair and reasonable price information for reactive power generation in the deregulated electricity market. The proposed algorithm has been tested on the IEEE 14-bus system using MATLAB.

• Journal of the Korean Society for Precision Engineering
• /
• v.14 no.5
• /
• pp.85-91
• /
• 1997

Air grinding time in grinding process has a great effect on its efficiency due to low feedrate. This paper presents a reduction methos of air grinding time in cylindrical plunge grinding operation. Tje reduction of air grinding time is accomplished by finding the distance between contact point and rising point of ultra- sonic signal of the grinding wheel to workpiece. It uses a variation of sound signal generated by the flow of coolant when the grinding wheel approaches to workpiece. The ultrasonic sensor with 23 kHz center fre- quency and 8 kHz bandwidth is used to find the nearest approaching point(NAP). Monitoring and control system of the grinding conditions is implemented with CNC controller to control feedrate override and ultrasonic sensor to find NAP. The experimental result shows that the ultrasonic signal is a good measure- ment to find NAP. But it needs the considerations for the effect of the relationship between flowrate of coolant and diameter of workpiece.

• Journal of Bio-Environment Control
• /
• v.28 no.4
• /
• pp.366-375
• /
• 2019

This experiment aims to determine the proper irrigation scheduling based on a whole-substrate capacitance using a newly developed device (SCMD) by comparing with the integrated solar radiation automated irrigation system (ISR) and sap flow sensor automated irrigation system (SF) for the cultivation of tomato (Solanum lycopersicum L. 'Hoyong' 'Super Doterang') during spring to winter season. For the SCMD system, irrigation was conducted every 10 minutes after the first irrigation was started until the first run-off was occurred, of which the substrate capacitance was considered to be 100%. When the capacitance threshold (CT) was reached to the target point, irrigation was re-conducted. After that, when the target drain volume (TDV) was occurred, the irrigation stopped. The irrigation volume per event for the SCMD was set to 50, 75, or 100 mL at CT 0.9 and TDV 100 mL during the spring to summer cultivation, and the CT was set to 0.65, 0.75, 0.80, or 0.90 in the winter cultivation. When the irrigation volume per event was set to 50, 75, or 100 mL, the irrigation frequency in a day was 39, 29, and 19, respectively, and the drain rate was 3.04, 9.25, and 20.18%, respectively. When the CT was set to 0.65, 0.75, or 0.90 in winter, the irrigation frequency was about 6, 7, 15 times, respectively and the drain rate was 9.9, 10.8, 35.3% respectively. The signal of stem sap flow at the beginning of irrigation starting time did not correspond to that of solar irradiance when the irrigation volume per event was set to 50 or 75 mL, compared to that of 100 mL. In winter cultivation, the stem sap flow rate and substrate volumetric water content at the CT 0.65 treatment were very low, while they were very high at CT 0.90 was high. All the integrated data suggest that the proper range of irrigation volume per event is from 75 to 100 mL under at CT 0.9 and TDV 100 mL during the spring to summer cultivation, and the proper CT seems to be higher than 0.75 and lower than 0.90 under at 75 mL of the irrigation volume per event and TDV 70 mL during the winter cultivation. It is going to be necessary to investigate the relationship between capacitance value and substrate volumetric water content by determining the correction coefficient.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.20 no.4
• /
• pp.25-32
• /
• 2012

Cold start driving cycles exhibit an increases in friction losses due to the low temperatures of metal components and media compared to the normal operating engine conditions. These friction losses are adversely affected to fuel economy. Therefore, in recent years, various techniques for the improvement of fuel economy at cold start driving cycles have been introduced. The main techniques are the upward control of coolant temperature and the fast warm-up techniques. In particular, the fast warm-up techniques are implemented with the coolant flow-controlled water pump and the WHRS (waste heat recovery system). This paper deals with an effect of fast ATF (automatic transmission fluid) warm-up on fuel economy using a recovery system of EGR gas waste heat in a diesel engine. On a conventional diesel engine, two ATF coolers have been connected in series, i.e., an air-cooled ATF cooler is placed in front of the condenser of air conditioning system and a water-cooled one is embedded into the radiator header. However, the new system consists of only a water-cooled heat exchanger that has been changed into the integrated structure with an EGR cooler to have the engine coolant directly from the EGR cooler. The ATF cooler becomes the ATF warmer and cooler, i.e., it plays a role of an ATF warmer if the temperature of ATF is lower than that of coolant, and plays a role of an ATF cooler otherwise. Chassis dynamometer experiments demonstrated the fuel economy improvement of over 2.5% with rapid increase in the ATF temperature.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.63 no.10
• /
• pp.1328-1336
• /
• 2014

This paper proposes Power System Health Index(PSHI) newly. The paper describes several kind of power system health indices based on two main categories, which are adequacy and security. In adequacy, four kinds of health indices of Frequency, Voltage, Reserve(Operating Reserve Power and Frequency Regulation Reserve Power) and Overload of lines and transformers are proposed. In security, four kinds of health indices of Voltage(154kV, 345kV and 765kV), Overload of lines and transformers, Power flow constraint among areas and SPS are proposed. All indices are mapped with three domains, which are indicated as Health, Margin and Risk, defined with expert interview. While domains of health, margin and risk is defined similar with the conventional well being analysis of power system. The criterion of the domains is proposed using an interview with expert operators and practical reliability codes in Korea. The several kinds of health index functions, which are linear ratio, piecewise linear ration and reverse ratio function etc. are developed in this paper. It will be expected that the developed health indices can help operators to control power system more successfully and also prevent power system from accident as like as black out in future because operator can make a decision immediately based on more easily visual information of system conditions from too much indices acquisition of complex power system.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.41 no.7
• /
• pp.435-443
• /
• 2017

The Characteristics of the flowfields of a square prism having a small square prism were investigated by measuring of lift and drag on the square prism and visualizing the flowfield using PIV. The experimental parameters were the width ratios(H/B=0.2~0.6) of small square prisms to the prism width and the gap ratios (G/B=0~3) between the prism and the small square prism. The drag reduction rate of the square prism initially increased and then decreased with the G/B ratio for the same H/B ratio, and increased with the H/B ratio for the same G/B ratio. The maximum drag reduction rate of 98.0% was observed at H/B=0.6 and G/B=1.0. The lift reduction rate of the square prism was not affected by the width and gap ratios; the total average value was approximately 66.5%. In case of a square prism having a small square prism, the stagnation regions were represented in the upstream and downstream sides of the square prism.