• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.1
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• pp.60-67
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• 2000

An experimental investigation on transient heat transfer phenomena of impinging diesel-spray on a flat plate in a pressurized chamber is carried out. A diesel spray is injected from a single-hole nozzle and impinges to a heated flat plate in the chamber. A fast-response thermocouple installed in the top surface of the plate measures the transient variation of surface temperature of the plate under various conditions of the chamber pressures. Utilizing the semi-infinite model, the temporal variation of the heat flux on the plate is determined. Effects of various parameters, such as vertical distances between the nozzle and the plate, radial distances from the injection-axis, and the chamber pressures, on the heat flux characteristics of impinging diesel-spray are studied.

• Journal of Ocean Engineering and Technology
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• v.6 no.2
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• pp.41-45
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• 1992

In this paper an application technique of moment equation method to solution of nonlinear rolling equation of motion of ships is investigated. The exciting moment in the equation of rolling motion of ships is described as non-white noise. This non-white exciting moment is generated through use of a shaping filter. These coupled equations are used to generate moment equations. The nonstationary responses of the nonlinear system are obtained. The results are compared with those of a linear system.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.3
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• pp.463-472
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• 1994

A method of stochastic response analysis of base-isolated fluid-filled pool structures subject to random ground excitations is studied. Fluid-structure interaction effects between the flexible walls and contained fluid are taken into account in the form of added mass matrix derived by FEM modeling of the contained fluid motion. The stationary ground excitation is represented by Modified Clough-Penzien spectral model and the nonstationary one is obtained by imposing an envelope function on the stationary one. The stationary and nonstationary response statistics of the two different isolation systems are obtained by solving the governing Lyapunov covariance matrix differential equations.

• Journal of the Korean Society of Propulsion Engineers
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• v.22 no.3
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• pp.28-39
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• 2018

In this study, numerical simulations were performed for steady and unsteady state characteristics of length effects on linear pintle nozzles using the overset grid method. Nozzles and pintles are created separately by an auto grid generation program to use the overset grid method. Appropriate turbulent models and numerical methods are selected for the validation of simulations. Pintle shapes are chosen from five types, with differences in the ratio of length and diameter. The longer the pintle length, the greater the thrust and thrust coefficient. The chamber pressure tendency of steady-state and unsteady-state are different for various pintle velocities. The thrust of the nozzle exit responds to changes in the nozzle throat in the unsteady-state, and the speed of pressure propagation wave generated by movement of the pintle is considered to predict the major factor of performance.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1997.10a
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• pp.345-351
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• 1997

The motion of an aircraft landing gear over rough runway at variable speed is nonstationary. hi this paper, a method for the computation of nonstationary response variance is presented which uses a state space form for the combination of landing gear and runway excitation. The dynamic characteristics of the landing gear under nonstationazy random excitations has also been analyzed using the proposed method. The formulation is for linear systems of arbitrary order and allows any deterministic velocity history.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.7
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• pp.959-965
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• 2002

It is intended to develop an algorithm for dynamic simulation of a fast-acting solenoid valve. The coupled equations of electric, magnetic, and mechanical systems should be solved simultaneously in a transient nonlinear manner. The transient nonlinear electromagnetic field is analyzed by the Finite Element Method (FEM), which is coupled with nonlinear electronic circuitry. The dynamic movement of the solenoid valve is analyzed at every time step from the force balance acting on the plunger, which includes the electromagnetic force calculated from the Finite Element analysis as well as the elastic force by a spring and the hydrodynamic pressure force along the flow passage. Dynamic responses of the solenoid valves predicted by this algorithm agree well with the experimental results including bouncing effects.

• The Korean Journal of Financial Management
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• v.17 no.1
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• pp.307-332
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• 2000

본 연구는 총 26개의 시중은행과 지방은행을 대상으로 설문조사를 통해 국내 은행의 위험관리 실태를 분석하였다. 나아가 정상은행과 경고은행 및 퇴출은행의 위험관리 행태에 차이가 있는 지를 살펴보았다. 조사 결과, 최고경영자나 임원이 위험관리 부서의 책임자로 있는 경우는 없고, 금융파생상품의 사용 등 관련사항의 보고가 효과적으로 이루어지지 않고, 감사위원회 역시 외부전문가를 둔 은행이 전혀 없는 것으로 조사되어 경영층의 위험관리 인식에 문제가 있는 것으로 나타났다. 위험관리에 관한 평가나 최고경영자에 대한 보고주기도 일정하지 않은 경우가 많았다. 위험 유형별로는 신용위험, 시장위험 및 유동성위험을 잘 인식하고 있는 반면, 운영위험이나 법적 위험에 대한 인식은 부족하였다. 위험관리 담당자의 교육 주기가 비정기적으로 이루어지고 있다고 응답한 경우가 60%로 가장 높았으며, 40%의 은행이 법적 위험 발생 시 책임소재가 분명하지 않다고 응답하였다. 시장위험 관리에 있어서도 매일 VaR값과 실제 손익을 정기적으로 비교한다고 응답한 경우는 15%에 불과하여 취약성을 드러냈다. 절반 정도의 은행은 금융파생상품을 전혀 이용하지 않고 있었다. 흥미롭게도 정상은행과 비정상은행 간 또는 비퇴출은행과 퇴출은행 간에 일부 항목을 제외하고는 행태 차이가 없었다. 결론적으로, 국내 은행의 위험관리는 전반적으로 미흡하여 체계적인 위험관리 시스템의 구축이 요구된다고 하겠다. 특히, 위험관리에 대한 최고경영층의 인식 제고가 요망되며, 합리적 은행구조조정을 위해서는 당해 은행의 위험관리 실태와 그에 따른 경영책임을 파악해야 할 것이다.

• Convergence Security Journal
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• v.7 no.1
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• pp.63-75
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• 2007

Most of computer systems to be connected to network have been exposed to some network attacks and became to targets of system attack. System managers have established the IDS to prevent the system attacks over network. The previous IDS have decided intrusions detecting the requested connection packets more than critical values in order to detect attacks. This techniques have False Positive possibilities and have difficulties to detect the slow scan increasing the time between sending scan probes and the coordinated scan originating from multiple hosts. We propose the port scan detection rules detecting the RST/ACK flag packets to request some abnormal connections and design the data structures capturing some of packets. This proposed system is decreased a False Positive possibility and can detect the slow scan, because a few data can be maintained for long times. This system can also detect the coordinated scan effectively detecting the RST/ACK flag packets to be occurred the target system.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.2
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• pp.243-250
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• 2003

The extinction behavior and the unsteady response of augmented reduced mechanism(ARM) have been investigated by adopting an OPPDIF code and a numerical solver for the flamelet equations. By comparing the performance of the ARM based on Miller and Bowman's mechanism(MB-ARM) with that of the ARM based on GRI-Mech 3.0(GRI-3.0-ARM), it is identified that the MB-ARM is more suitable for the unsteady calculation because it is relatively less stiff than GRI-3.0-ARM during an ignition process. The steady results using the MB-ARM, which is modified to predict reasonably the extinction point of experiment, are in excellent agreement with those from full mechanism. Under the sinusoidal transient disturbances of scalar dissipation rate, the unsteady responses of the flame temperature and species concentrations using a modified MB-ARM show in very close agreement with those from full mechanism. It is presumed that above modified MB-ARM is very suitable for the unsteady simulation of turbulent flames because it gives not only a low computational cost but also a good prediction performance for flame structure, extinction point and unsteady response.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2009.10a
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• pp.305-309
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• 2009

This paper operate with variable line impedance equipment consist of resister and reactor, when connect to 3phase induce motor present solve problem appear grid interconnection before/after about voltage transient of pv inverter through test and analysis solve problem.