• Journal of Electrical Engineering and Technology
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• v.5 no.4
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• pp.530-537
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• 2010

By development of renewable energy and more efficient facilities in an increasingly deregulated electricity market, the operation cost of distributed generation (DG) is becoming more competitive. International environmental regulations of the leaking carbon become effective to reinforce global efforts for a low-carbon paradigm. Through increased DG, operators of DG are able to supply electric power to customers who are connected directly to DG as well as loads that are connected to entire network. In this situation, a community energy system (CES) with DGs is a new participant in the energy market. DG's purchase price from the market is different from the DG's sales price to the market due to transmission service charges and other costs. Therefore, CES who owns DGs has to control the produced electric power per hourly period in order to maximize profit. Considering the international environment regulations, CE will be an important element to decide the marginal cost of generators as well as the classified fuel unit cost and unit's efficiency. This paper introduces the optimal operation of CES's DG connected to the distribution network considering CE. The purpose of optimization is to maximize the profit of CES. A Particle Swarm Optimization (PSO) will be used to solve this complicated problem. The optimal operation of DG represented in this paper would guide CES and system operators in determining the decision making criteria.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.157.3-157
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• 2001

In this paper, the optimal maintenance scheduling for turbine with considering maintenance replacement rate was proposed in order to reduce the maintenance cost during the whole period of operation, meanwhile keeping current reliability of turbine. The proposed method is only based on a few limited available data with various factors relating to maintenance replacement and repair of turbine. The proposed method will be adopted by Kyushu Electric Power Co., Inc. from April in 2002 to determine the maintenance schedule of thermal power plants.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.10a
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• pp.59-63
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• 2011

Friction damping is one of the attractive vibration control technique for space structures due to its simplicity and large damping capacity. However, passive approaches for friction damping have a limitation because energy is no longer dissipated at sticking. In order to overcome this problem, semi-active control methods to adjust normal force at frictional interface have been studied in previous researches. In this paper, two semi-active friction control method is compared by simulating SDOF model of truss structure. The first approach is on-off control to maximize rate of energy dissipation, whereas the second concept is variable friction force control to minimize amplitude ratio for each half period. The maximum friction force, control variable in on-off control method, is obtained to minimize 1% settling time, and is different from optimal friction force in passive control. Simulation results show that performance of on-off control is better than that of variable friction force control in terms of settling time and controlled friction force.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.10 s.241
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• pp.1430-1437
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• 2005

It is very important to achieve a high reproducibility in the ultrasonic measurement of bone mineral density. In this study, we examined number of sampling waveform, control of temperature, diameter of region of interest as factors to improve reproducibility. We decided the optimal number of waveforms to be converted to frequency domain as period of 1. We have minimized the effects of variable temperature and constrained generation of micro bubble by keeping temperature within a range of $32\pm0.5^{\circ}C$ with a precise temperature controlling algorithm. We also found the optimal diameter of region of interest to be 13mm. In this paper, we demonstrated the improved reproducibility by controlling various factors affecting the ultrasonic measurement of bone mineral density.

• Proceedings of the Korea Society for Simulation Conference
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• 2003.06a
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• pp.129-134
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• 2003

In this paper, we determine optimal reduction in the lead time and setup cost for some stochastic inventory models. And we propose more general model that allow the backorder rate as a control variable. We first assume that the lead time demand follows a normal distribution. And we assume that the backorder rate is dependent on the length of lead time through the amount of shortages. The stochastic models analyzed in this paper are the classical continuous and periodic review policy models with a mixture of backorders and lost sales. For each of these models, we provide a sufficient conditions for the uniqueness of the optimal operating policy. We also develop algorithms for solving these models and provide illustrative numerical examples.

• Korean Journal of Veterinary Service
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• v.23 no.3
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• pp.289-299
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• 2000

The study was performed to investigate the distributions of swine pleuropneumonia in Kyongbuk western area by the enzyme-linked immunosorbent assay (ELISA). Sera collected from 400 slaughtered pigs in 3 slaughter houses during the period from May 1999 to october 1999 were tested to detect antibodies against A pleuropneumonie serotype 2 and 5. The optimal dilution of CBE antigen, conjugate and serum for this ELISA were determined 1 : 400, 1 : 20,000, 1 100, respectively. The optimal dilution of OW antigen, conjugate and serum for this ELISA were determined 1 : In, 1 : 20,000, 1 : 200, respectively. Cut-off value in this ELISA was determined by mean absorbance (at 492 nm) of negative control sera added with the triple value of the standard deviation. Cut-off value in ELISA by CBE and OMP antigen were 1.134 and 1.217, respectively. By the ELISA, positive reaction rates to A pleuropneumoniae serotype 2 and 5 for CBE antigen were 38.8% and 18.8%, and for OMP antigen were 42.8% and 23.5% of the 400 samples, respectively.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.1
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• pp.331-343
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• 2015

We propose a distributed medium access control protocol for cognitive radio networks to opportunistically utilize multiple channels. Under the proposed protocol, cognitive radio nodes forecast and rank channel availability observing primary users' activities on the channels for a period of time by time series analyzing using smoothing models for seasonal data by Winters' method. The proposed approach protects primary users, mitigates channel access delay, and increases network performance. We analyze the optimal time to sense channels to avoid conflict with the primary users. We simulate and compare the proposed protocol with the existing protocol. The results show that the proposed approach utilizes channels more efficiently.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.06a
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• pp.527-533
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• 1998

An optimized PWM switching strategy for an induction motor voltage control is developed and demonstrated. Space vector modulation in voltage source inverter offers improved DC-bus utilization and reduced commutation losses, and has been therefor recognizedas the perfered PWM method, especially in the case of digital implementation. Three-phase invertor voltage control by space vector modulation consists of switching between the two active and one zero voltage vector by using the proposed optimal PWM algorithm. The prefered switching sequence is defined as a function of the modulation index and period of a carrier wave. The sequence is selected by suing the inverter switching losses and the current ripple as the criteria. For low and medium power application, the experimental results indicate that good dynamic response and reduced harmonic distortion can be achieved by increasing switching frequency.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.60.1-60
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• 2001

In recent years, distributed control systems(DCS) using fieldbus such as CAN have been being applied to process systems but it is very difficult to design the DCS in order to guarantee the given end-to-end constraints such as precedence constraints, time constraints, and periods and priorities of tasks and messages. This paper presents a scheduling method to guarantee the given end-to-end constraints. The presented scheduling method is the integrated one considering both tasks executed in each node and messages transmitted via the network and is designed to be applied to a general DCS that has multiple loops with several types of constraints, where each loop consists of ...

• Journal of Animal Science and Technology
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• v.48 no.6
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• pp.897-906
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• 2006

This study was conducted to determine effects of different supplementation periods (2, 3 and 4 months) of spent composts of Se-enriched mushrooms (Se-SMC) on plasma glutathione peroxidase (GSH-Px) activity and selenium deposition of finishing Hanwoo steers for the optimal supplementing period determination in order to produce Se-fortified Hanwoo beef. In the present study, 30 Hanwoo steers were allotted to treatments in six groups of five steers per pen. Treatments were separated into control and Se-SMC for each supplementation period. Dietary selenium contents were 0.1 and 0.9 ppm for control and Se-SMC treatments, respectively. At the end of each supplementation period, steers by periods were slaughtered to collect hind leg and liver samples for their selenium analyses. Blood samples were taken to analyze whole blood Se concentration and plasma GSH-Px activity at the last day of each supplementation period. Dry matter intakes were unaffected by Se-SMC and supplementation periods. In addition, average daily gain was not different between control and Se-SMC treatments and among supplementation periods. There was no difference for total body weight gain between control and Se-SMC treatments within each supplementation period. The supplementation of Se-SMC significantly (P<0.001) increased whole blood Se concentration, but whole blood selenium concentration was not affected by the supplementation period. Furthermore, plasma GSH-Px activity showed similar trend as shown in the pattern of whole blood Se concentration, but no difference by supplementation periods was observed. Selenium contents in hind legs significantly (P<0.05) increased with increasing supplementation periods, and also they were significantly (P<0.001) higher for Se-SMC supplementation groups in comparison to controls. However, there was no difference for selenium contents of hind legs between three and four months supplementation. Selenium contents in livers tended to slightly increase with increasing supplementation periods with no significant difference, but they were significantly (P<0.01) higher for Se-SMC supplementation groups compared with controls within the same period. The results indicated that the optimal Se-SMC supplementation period for the selenium deposition in Hanwoo steers might be around two or three months when we considered selenium contents in hind legs and livers.