• Journal of Advanced Marine Engineering and Technology
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• v.19 no.3
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• pp.24-32
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• 1995

The scavenging characteristics have a great influence on the performance of a diesel engine, especially slow-speed two-stroke diesel engines which are usually used as a marine propulsion power plant, and they are greatly affected by the conditions in the cylinder, intake and exhaust manifolds, and the opening and closing timing of scavenging ports or exhaust valves during the gas exchange process. Besides, there are many other factors to affect the scavenging characteristics and these factors interact each other very complicatedly. Therefore the simulation program of the gas exchange process is very useful to improve and predict the scavenging characteristics, due to the high costs associated with redesign and testing. In this paper it was attenpted to investigate the effect of the variation of the pressure ratio of intake to exhaust manifolds, and the variation of the opening and closing timing of a exhaust valve by using a computational program for a three-zone scavenging model which was developed by authors. The computed results showed that the scavenging efficiency and delivery ratio increased considerably, but the trapping efficiency decreased with increasing of the pressure ratio of intake to exhaust manifolds. The scavenging efficiency, trapping efficiency, and th conditions of the cylinder gases were affected by the opening timing of the exhaust valve, but the delivery ratio by the closing timing.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.2
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• pp.658-661
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• 2005

Internet-based client/server architecture of Contents Delivery System suffers from frequent disconnections and security treats caused by dependency of the server or overload. But, We reached the limit to the increase of the server because a contents quality enhance and Internet user explosively increase. Therefore, a P2P based computing methods are used for sloving these issues. In this paper, We implement and design the Education Content Delivery System for cyber education system using idle Computing Power in P2P computing to share computing resources. We implement not only Internet infrastructure but also satellite infrastructure system, and designed to transfer real-time or non real-time contents.

• Proceedings of the KOSOMBE Conference
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• v.1996 no.11
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• pp.22-24
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• 1996

Small size DC motor control method for portable drug delivery system has been developed to be used for the actuator of insulins pump. The control method gives the controllabilities both in high speed(40-50 revolution per second(rps)) DC motor drive and also in low speed(0.5-1rps). In low speed mode DC motor is controlled to act like stepping motor and in high speed to optimize power consumption. To control both mode modified bang bang control is suggested. Using this method small size DC motor(spec.) speed is controlled from 0.2 rps to 50 rps. Experimental setup is developed using micro-processor(PIC16C73, Micro Chips co., USA), motor turns checking circuitry, small size DC motor for pager(SM1012, Samhong co., Korea) and gear box. Results from experiment meet need for vailable load condition which is require for portable drug delivery system.

• Journal of Power Electronics
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• v.17 no.1
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• pp.305-313
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• 2017

A novel interference isolation method is proposed by using several designed coils in capacitive power transfer systems as isolation impedances. For each designed coil, its stray parameters such as the inter-turn capacitance, coil resistance and capacitance between the coil and the core, etc. are taken into account. An equivalent circuit model of the designed coil is established. According to this equivalent circuit, the impedance characteristic of the coil is calculated. In addition, the maximum impedance point and the corresponding excitation frequency of the coil are obtained. Based on this analysis, six designed coils are adopted to isolate the interference from power delivery. The proposed method is verified through experiments with a power carrier frequency of 1MHz and a data carrier frequency of 8.7MHz. The power and data are transferred parrallelly with a data carrier attenuation lower than -5dB and a power attenuation on the sensing resistor higher than -45dB.

• Proceedings of the KAIS Fall Conference
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• 2009.12a
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• pp.834-836
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• 2009

The authors have been discussed the optimal voltage regulation method and on-line real time method using artificial neural networks in the distribution system interconnected with Distributed Generation and Storage(DSG) systems. However, these methods have difficulty in dealing with the random load variations and operation characteristics of a number of DSG systems. To overcome these problems, this paper shows the basic concepts of smart grid system which is considered as one of the power delivery system in the near future and presents an evaluation method on the impacts of customer voltages by the operation of smart grid system. The smart grid system can change the system configuration in a flexible manner by using the static switches and offer the different power qualities in power services through the power quality control centers.

• Proceedings of the KIEE Conference
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• 1992.07a
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• pp.51-54
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• 1992

Protection and control systems play a prominent part in avoiding power delivery interruptions and help to get a fast and secure restoration when a failure occurs. In order to meet the higher functional requirements on modern power system, protection speed, selectivity, sensitivity, dependability, and security are essential to ensure reliability. These functions on be satisfied by taking advantage of microprocessor and communication technologies, and digital protection relays (systems) have been developed and applied to real power system enhancing reliability and saving money. It is necessary to have a tool to analyze the functions and algorithms of digital relays for installing them to power system. The purpose of this study is to develop a digital relay simulation program to estimate digital relay performances during system faults. Components of digital protective relay including analog filter, sampling unit, digital filter, and relay logic are modeled in this program.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.22-23
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• 2015

As wireless power transfer (WPT) technology using strongly coupled electromagnetic resonators is a recently explored technique to realize the large power delivery and storage without any cable or wire, this technique is required for diffusion of electric vehicles (EVs) since it makes possible a convenient charging system. Typically, since the normal conducting coils are used as a transmitting coil in the CPT system, there is limited to deliver the large power promptly in the contactless EV charging system. From this reason, we proposed the combination CPT technology with HTS transmitting antenna, In this study, we examined the improvement of transmission efficiency and properties for HTS and copper antennas, respectively, at 30 cm distance. Thus, we obtained improved transfer efficiency with HTS antenna over 10% compared with copper antenna

• Journal of electromagnetic engineering and science
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• v.2 no.2
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• pp.68-74
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• 2002

In this paper, a pre-layout design approach for high-speed microprocessor is proposed. For multilayer PCB stark up configuration as well as selection and placement of decoupling capacitors, an effective solution for reducing SSN and EMI is obtained by modeling and simulation of complete power distribution system. The system model includes VRM, decoupling capacitors, multiple power and ground planes for core voltage, vias, as well as microprocessor. Finally, the simulation results are verified by measurements data.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.11a
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• pp.437-440
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• 2000

In this study, the interfacial dielectric breakdown phenomenon of interface between Epoxy and Rubber was discussed, which affects the stability of insulation system of power delivery devices. The breakdown strength of specimens are observed by applying high AC voltage at the room temperature. The breakdown times under the constant voltage below the breakdown voltage were gained. As constant voltage is applied, the breakdown time is proportion to the breakdown strength. The life exponent n is gained by inverse power law and the long time breakdown life time can be evaluated.

• Journal of Biomedical Engineering Research
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• v.17 no.4
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• pp.491-498
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• 1996

The development of a compact two-wavelength Nd:YAG laser for dental and ENT applications is presented. The Nd:YAG resonator generates either 1.06$\mu$m or 1.32$\mu$m. The wavelength selection is made at the control panel. The Nd:YAG laser parameters at 1.06$\mu$m are ; the maximum pulse duration of 150$\mu$s, repetition rates of I-100Hz, and the maximum average power of 25W. At 1.32$\mu$m, the pulse duration is the same where the repetition rates and the maximum average power are I-30Hz and lOW respectively. High voltage power supply consists of a simmer module and two identical high voltage DC converters. In order to make a complete medical laser system, an optical fiber delivery unit, foot pedal and water spray handpiece are also developed. The wavelength selection is reliable since no movement of optical or mechanical components is required. The high voltage power supply is compact, easy to be maintained and applicable for other laser systems due to its modular design.