• Proceedings of the Korean Society of Propulsion Engineers Conference
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• v.y2005m4
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• pp.334-342
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• 2005

A numerical analysis is performed using two dimensional axisymmetric RANS (Reynolds Averaged Navier-Stokes) equations system on the transition sequence of the Integrated Rocket Ramjet and the unsteady reacting flow-field in a ramjet combustor during unstable combustion. The mode transition of an axisymmetric ramjet is numerically simulated starting from the initial condition of the boost end phase of the entire ramjet. The unsteady reacting flow-field within combustor is computed for varying injection area. In calculation results of the transition, the terminal normal shock is occurred at the downstream of diffuser throat section and no notable combustor pressure oscillation is observed after certain time of the inlet port cover open. For the case of a small injection area at the same equivalence ratio, periodic pressure oscillation in the combustor leads to the terminal shock expulsion from the inlet and hence the buzz instability occurred.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.54 no.10
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• pp.470-476
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• 2005

In this paper PU control scheme is presented. The proposed scheme has following features. The one is oft-starting method which is used for preventing to flow large current in motor phase winding when motor starts. The ther is the selection of the level of the over current. The first feature is implemented by increasing the PWM duty lowly, the second feature is implemented by limiting the magnitude of the phase current level by which the over heat f motor by copper losses and magnetic saturation decreases. By the analysis using FEM considering load condition, the peed of mode transition from PW to single pulse control is selected and confirmed by simulation that there is no ver current occurs during the mode transition. For the verification of proposed scheme, the simulation using MATLAB Simulink with considering non-linearity of inductance profile from FEM analysis is performed and the experiment with SRM drive system which has the DSP controller and single Phase SRM are peformed.

• The Bulletin of The Korean Astronomical Society
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• v.39 no.2
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• pp.40-40
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• 2014

Through KASI, Korean astronomers will have access to the Gemini Observatory starting in 2015. Gemini operates two optical/infrared 8m-class telescopes: one on the northern hemisphere in Hawaii, one on the southern hemisphere in Chile. Both are equipped with state of the art instruments and adaptive optics systems that will be presented. Gemini also offers the opportunity for instrument development and welcomes visiting instruments. In terms of operations, Gemini offers to its partners three ways of applying for time: through semester-basis calls for standard programs, through yearly calls for Large and Long Programs, and through monthly calls for fast turnaround programs. Gemini operates in queue mode (observing for the principal investigators and allowing flexibility in the time domain), as well as in the classical visitor mode (where principal investigators come to the telescope). I will explain the requirements and advantages of all these modes as well as a full update on the Gemini Observatory.

• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.571-574
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• 2003

Three ring type liquid crystalline compounds having 4-alklycyclohexyl group, 1,2-difluorobenzene and phenylisothiocyanate moieties as main skeleton were designed to have negative dielectricity. However, the compounds with 2,3,2'-trifluoro-3'-isothiocyanated biphenylcyclohexane core did not exhibit the nematic liquid crystalline phase because of two conformers by interaction of isothiocyanate and adjacent fluorine atoms. Also, 4-alkyl-2,2',3'-trifluoro-3-isothiocyanated biphenylcyclohexane core was designed expecting to have uniform conformers of isothiocyanate group. In the course of developing polyimides for VA mode LCD, we synthesized alkyl-3,5-diaminobenzene efficiently with various length of alkyl chains from commercially available di-t-butyl malonate and 3,5-dinitrobenzoyl chloride as starting material.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.53 no.7
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• pp.417-423
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• 2004

The headway in Korean national railway normally runs from 6 to 10 minutes. It turns out that the current signal system can not decrease the running headway of the High Speed trains, which are scheduled to set out in April, 2004, between Seoul and Daejeon, since both the existing classical trains and the High Speed ones run on the section. Thus, a new signal system is to be introduced to secure safe and reduced headway. The present paper attempts to analyze the headway between this particular section Seoul-Daejeon of the classical line, where we expect the most severe bottleneck situation to occur. We employed two modes in our analysis : the Ground Signal mode and the On-board Signal mode. which are to be adopted starting from 2006.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2006.05a
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• pp.395-398
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• 2006

this paper provides a novel method to start the linear engine coupled linear generator from dead stop to its final steady state operation. This method depends mainly to use the linear generator mounted on the shaft of the linear engine to provide the required thrust force to move and oscillate the linear engine from bottom to top dead centers. It is a cost effective approach to start the internal linear combustion engine using its coupled tubular permanent magnet linear generator proposed here. This linear generator operates in this case in motoring mode, providing the required thrust force by feeding this linear generator phases with currents by using a three phase PWM inverter controlled by position feedback scheme. In order to provide the desired thrust force with specific value and direction, a position feedback is required to control the free piston engine motion through controlling the inverter switches using PWM control scheme.

• Transactions of the Korean Society of Automotive Engineers
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• v.17 no.4
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• pp.72-78
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• 2009

The regulation for $CO_2$ emissions from vehicles have become much more stringent in recent years. These more stringent regulations request vehicle manufacturers to develop alternative fuels to reduce exhaust emissions. In this paper, $CO_2$ emission of gasoline, diesel and LPG vehicles in the CVS-75mode is analyzed. The experimental results indicated that the cold starting acceleration period of $CO_2$ emission was much longer compared to the hot start acceleration period. For example, gasoline vehicle and LPG fuel vehicle had 21% higher $CO_2$ emission and diesel vehicle had 34% higher $CO_2$ emission.

• Journal of the Korean Society of Safety
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• v.31 no.2
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• pp.10-17
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• 2016

The purpose of this paper is to deduct components that are in the group of highest risk(top 10%). the group is conducted for classification into groups by values according to risk priority through risk priority number(RPN) of FMEA(Failure modes and effects analysis) sheet. Top 10% of failure mode among total potential failure modes(72 failure modes) of ESS included 5 BMS(battery included) failure modes, 1 invert failure mode, and 1 cable connectors failure mode in which BMS was highest. This is because ESS is connected to module, try, and lack in the battery part as an assembly of electronic information communication and is managed. BMS is mainly composed of the battery module and communication module. There is a junction box and numerous connectors that connect these two in which failure occurs most in the connector part and module itself. Finally, this paper proposes RPN by each step from the starting step of ESS design to installation and operation. Blackouts and electrical disasters can be prevented beforehand by managing and removing the deducted risk factors in prior.

• The Transactions of the Korean Institute of Power Electronics
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• v.18 no.2
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• pp.138-144
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• 2013

Most of the DC loads have had the sensitive characteristics electrically for input voltage. In this system, power converter is operated after connecting with DC loads to minimize the overshoot of the control voltage that may occur during connection of the loads. But whenever starting the power converter, parameters in circuit are different because power converter has been connected with diverse load types at each startup time. This is cause of a disadvantage to PI controller design of power converter. In this paper, the novel voltage control method using sliding mode control theory has proposed. This control method minimizes the overshoot of control voltage at startup of power converter. Despite the variations of the system parameters, the proposed voltage controller has fast response and robustness characteristics such as PI and sliding mode controllers. The proposed controller was applied to the three-phase AC/DC converter and each performance of controller was verified.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.12
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• pp.1729-1734
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• 2018

Recently, interest in environmentally friendly transportation systems has been increasing, and study on railway systems has been aggressively conducted. Therefore, lots of studies have been done in railway advanced countries to improve performance of PWM converter. The research on the PWM converter for railway vehicle was mainly carried out on the converter mounted on railway vehicle such as the high-speed railway and metropolitan railway. In also, a lot of study has been carried out to improve converter performance installed in the ground. The high-capacity transform used in this paper converted from AC 22.9kV to AC 590V. The converter changed from AC 590V to DC 950V. In general, in the case of rectifier, the DC power supply system has a negative impact on inverter control characteristics because it can not avoid the pulsating component. In this study, it was performed current control for high-capacity converter using Matlab Simulink. The PWM converter is normally performed through the voltage and current at starting mode, powering mode, and braking mode. In the light-load test and the on-line test, we have studied for the PWM converter characteristics. Using this research, we have founded that the converter has excellent performance.