실리카 입자를 함유한 광경화형 도료 물성

홍진후,주형태,김순기,김석찬 조선대학교 생산기술연구소 2004 生産技術硏究 Vol.26 No.1

We investigated the effects of nano-silica on the kinetic and film properties of UV curable coatings. Coating properties such as hardness, gloss, chemical and stain resistances and adhesion of the UV cured films containing various concentration of nano-silica were investigated. The matting, pencil hardness, chemical resistance, and abrasion resistances were apparently improved Via addition of nano-silica. Pendulum hardness was also enhanced with the increasing content of nano-silica up to 5 weight percent. However, the pendulum hardness and the adhesion decreased as nano-silica content increased above 10 weight percent. DPC analysis revealed that the presence of nano-silica in UV curable coating formulation enhanced photo curing. It was demonstrated that hardness. abrasion resistance, and chemical resistance of UV cured film can be increased without loss of optical properties through nanocomposite.

PWM인버터회로에서의 손실분석

洪淳瓚,金鍾九 단국대학교 1995 論文集 Vol.29 No.-

This paper deals with loss analysis in inverter circuits controlled by pulse width modulation method. The loss in inverter circuits may be produced in active switching elements, passive switching elements, and snubber circuit. The losses in active switching elements are classified into the conduction losses and switching losses, and can be reduced by the selection of elements with low saturation voltage and short turn-on/turn-off times. There are also conduction losses and switching losses in passive switching elements and these losses can be reduced by selecting the fast recovery diode with low forward voltage drop and short reverse recovery time. The loss in snubber circuit is relatively small and can be ignored. As an example, the loss calculation and analysis are carried out in the prototype three-phase VSI(Voltage Source Inverter) for electric vehicles.

인가전압제어에 의한 유도전동기의 효율향상에 관한 연구

洪淳瓚 단국대학교 1993 論文集 Vol.27 No.-

This paper deals with the algorithm and implementation that can improve the efficiency of three-phase induction motors by controlling the applied voltage. The algorithm is based on the characteristic analysis of induction motors. To improve the efficiency, the applied voltage should be reduced in proportion to the square root of the reduction rate of load and the rotating speed should be kept constant. Next, the system to implement simply the proposed algorithm was designed and experimented. The final target in this study was to save electrical energy, hence the principal object in design is not the accurate control but the economical efficiency. The experimental results shows that the efficiency of motors is remarkably increased in low load factor. In designing the system, the economical efficiency was considered in the first place. Therefore, the proposed system may have a marketability and it is expected that the electrical energy is really saved in industry by the easiness of practical use.

삼상 ICB회로의 설계기준에 관한 연구

洪淳瓚 단국대학교 1992 論文集 Vol.26 No.-

This paper deals with the design criteria of the three-phase ICB(Inductor Converter Bridge) circuit for phase difference control. To determine the voltage ratings of capacitors and thyristors, the peak values of voltage across the elements were derived as the function of related parameters and were analyzed for all the range of phase difference between the two converters. Also, the capacitance of capacitors was estimated and the current ratings and turn-off time of thyristors were analyzed. Finally, a three-phase ICB circuit was designed as an example. In the example, the loads were two superconductive coils with inductance L_s=L_L=L=0.422 [H] and stored energy E=0.5 [MJ] The resulting values in this paper are gheoretical values. Therefore, for the stability of practical system, it is necessary that the turn-off time is shorter than the theoretical value and the ratings of voltage and current should have 50 [%] margin.

상태변수평균화법에 의한 삼상 ICB 회로 해석

洪淳瓚 단국대학교 1989 論文集 Vol.23 No.-

In this paper, the time-averaged behavior of the three-phase ICB(Inductor-Converter-Bridge) circuit has been analyzed by using the state-space averaging method. The results are in closed form far from the results obtained by using the Fourter series. Therefore, the computational difficulties of the infinite Fourier series can be avoided and the results derived in this paper are available especially in real time control. Also, it was verified that the analysis by means of state space averaging method was more accurate and simple by comparison with the Fourier results. Unlike the SFC, S^4LCL, DFC and other circuits which have time varying switching intervals for a constant time-averaged value of coil voltage, the ICB circuits operate with a clock-driven sequence of gate pulses which have constant switching intervals.

구형함수에 의한 단상 ICB 회로 해석

洪淳瓚 단국대학교 1988 論文集 Vol.22 No.-

This paper presents a new analysis method for rhe single phase ICB circuit, which belong to a new group of converters. Unlike the SFC, S^4LCL, DFC and other circuits which have time varying switching intervals for a constant time-averaged value of coil voltage, the ICB circuits operate with a clock-drived sequence of gate pulses which have constant switching intervals. This new method is a specialized method of analysis for calculating the dynamic functions of the ICB and the computational difficulties of the infinite Fourier series can be avoided. At first, quadrometric functions are newly defined in terms of the superposition of several unit step functions, and then single phase ICB circuit is analyzed by newly defined square function. By comparison with the Fourier resullt, it is verified that the analysis by means of square functions is more accurate and simple.

마이크로프로세서에 의한 직류전동기의 고효율 운전해석

洪淳瓚 단국대학교 1984 論文集 Vol.18 No.-

This paper describes a method to analyze the drive system which can improve the efficiency of dc motors. It is derived that the ratio of the armature current and the field current should be maintained constant to maximize the efficiency at a specified speed. The real time control is implemented by using a microprocessor. To increase the efficiency, the flux should be reduced. Reducing the flux may cause undesirable dynamic responses. In order to investigate the dynamic characteristics, the system equation is derived which consists of three equations of the dc motor and two equations of the controllers. Because the system equation is nonlinear, the small signal linearization is used. As the system is controlled by the microprocessor, the linearized system equation should be transformed into the difference equation. Based on this system equation, computer simulations are carried out. As a result, the dynamic response is satisfactory regardless of reducing the airgap flux.

지역사회 정신의학 전공의 교육과정 실태조사

홍진표,황순찬,이영문,이선형,신나리,이종일,박종익,장동원,정인원 大韓神經精神醫學會 2008 신경정신의학 Vol.47 No.1

Objectives : There is a increasing need to recruit and retain more psychiatrists who can plan and implement organized programs to work with chronic mentally ill patients in community settings. The aim of study is to discover what training is currently in place to prepare psychiatrist for work in "community" or "public" settings. Methods : Survey questionnaires were mailed to 85 residency training directors and 10 leaders of community mental health in 2005. Response rate was 75%. Results : Academic seminar about community mental health were not administered to residents in 63% of training hospitals. Forty one out of 64 training hospitals had community mental health rotation programs, Community mental health center (50%) and day hospital (36%) were the most common type of programs. Few general hospital had affiliation with community mental health programs. The amount of time for clinical rotation varied from less than three months part time to 6 months fulltime, with most frequent form of one day per week for three month in second or third year of psychiatry residents. Conclusion : Further steps are needed to improve residency training curricula and to encourage well qualified psychiatrist to choose careers in community psychiatry.

직렬공진형 컨버어터의 해석

洪淳瓚 단국대학교 1990 論文集 Vol.24 No.-

This paper deals with the operation analysis of the full-bridge series-resonant converter with considering the load short. For the analysis in steady state, both the continuous mode and the discontinuous mode were considered. With the results of analysis, the computer simulations were carried out to show the tendencies of the variables to the variations of α and Q. The variables includes the averages and rms values of resonant current, the average values of the current flowing through transistors and diodes, and the maximum values of resonant current and resonant capacitor voltage. If the load is short during steady operation, the short-circuit current in continuous mode may be very high enough to damage the main circuit. The maximum values of the resonant current and the resonant capacitor voltage in the case of load short were obtained by computer simulation. By the comparison between the maximum values of the resonant current in steady operation and those in the case of load short, the optimal operation region was obtained to limit the short-curcuit current. If the converter is operated in the optimal operation region derived in this paper, the short-circuit current can be limited even though the load is short during steady operation. This can enlarge the merits of the resonant converters in the viewpoint of weight, volume, and cost.

電子計算機에 의한 半導體回路의 解析

洪淳瓚 단국대학교 1980 論文集 Vol.14 No.-

In the earlier papers published on digital computation of semiconductor circuits, the different equivalent circuits that arise during the operation of the circuit were assumed. The differential equation corresponding to individual modes of operation were set up and can only applied to special circuits. In order to overcome the disadvantage, the method based on network topology was developed. In this method, the thyristors and the diodes are assumed to represent open circuit when they are off and a small resistance when they are on. The assumption requires a change in the topology of the original network from mode to mode. This paper deals with the computer aided analysis method for semiconductor circuit which rejects the disadvantage. The method is based on network topogy and semiconductors are considered as resistance elements which have different resistance depending on its mode. The advantage of this method is that the incidence matrix doesn't need to reconstruct regardless of mode change and the loop calculation is reduced in the program. As an example, this is applied to a single-phase full-wave controlled rectifier circuit with an RL load and the fow charts and the computed results are presented.