• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.3 s.174
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• pp.691-700
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• 2000

This paper presents a novel type of a semiactive damper featuring an electro-rheological(ER) fluid. Unlike conventional cylindrical ER damper, the proposed one has controllable orifices by the intensity of electric fields (We call it orifice type). The dynamic model of the orifice type ER damper is formulated by incorporating field-dependent Bingham properties of an arabic gum-based ER fluid. Design parameters such as electrode gap are subsequently determined on the basis of the dynamic model. After manufacturing the orifice type ER damper, field-dependent damping forces and damping force controllability are empirically evaluated. In the evaluation procedure, conventional cylindrical ER damper is adopted and its performance characteristics are compared with those of the orifice type ER damper. In addition, the proposed one is installed with a full-car model and its vibration control performance associated with a skyhook controller is investigated.

• Smart Structures and Systems
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• v.14 no.4
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• pp.541-558
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• 2014

This paper proposes a new design of shape memory alloy (SMA) wire actuated gripper for open mode operation. SMA can generate smooth muscle movements during actuation which make them potentially good contenders in designing grippers. The principle of the shape memory alloy gripper is to convert the linear displacement of the SMA wire actuator into the angular displacement of the gripping jaw. Steady state analysis is performed to design the wire diameter of the bias spring for a known SMA wire. The gripper is designed to open about an angle of $22.5^{\circ}$ when actuated using pulsating electric current from a constant current source. The safe operating power range of the gripper is determined and verified theoretically. Experimental evaluation for the uncontrolled gripper showed a rotation of $19.97^{\circ}$. Forced cooling techniques were employed to speed up the cooling process. The gripper is simple and robust in design (single movable jaw), easy to fabricate, low cost, and exhibits wide handling capabilities like longer object handling time and handling wide sizes of objects with minimum utilization of power since power is required only to grasp and release operations.

• Proceedings of the KIEE Conference
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• 2004.04a
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• pp.24-26
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• 2004

For past decade, medium voltage circuit breakers have used the spring-driven mechanical system for interrupting of electric power. However, these mechanisms have many disadvantages of high power consumption, mechanical control components and electrical switching ones for the coil current. Recently, the vacuum interrupter operated by permanent magnet actuator gives outlook on improved characteristic, higher reliability and cost price reduction as well as the feature of simple structure and few components. This paper deals with the dynamic characteristics of permanent magnet actuator used in the medium voltage distribution systems. Coupled finite element method is used to analysis the dynamic characteristics of permanent magnetic actuator and we compared with those of conventional ones.

• 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.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1999.10a
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• pp.425-431
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• 1999

Nowadays development of electric and optical devices needs precision more and more. This study focuses on hydrostatic journal bearing of grinding wheel spindle. It presents theoretical analysis about cylinder type self-controlled restrictor to control flux of oil flowing into pockets around the hydrostatic journal bearing. As a result of this analysis, optimal properties to maximize bearing stiffness such as initial cross distance, supply pressure, diameter of two supply holes, pre-load of spring and clearance between spindle and housing can be obtained. Therefore, by using them it is possible to estimate bearing stiffness and the performance of grinding wheel spindle can be improved.

• Proceedings of the Korea Information Processing Society Conference
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• 2017.11a
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• pp.211-213
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• 2017

최근 보안적 이슈에 따른 피해가 지속적으로 늘어남에 따라 사람들이 보안에 관심이 많아 지기 시작했다. 모의해킹 분야의 경우 기존에 문제 풀이 웹 사이트들이 존재하지만 회원 가입 단계로부터 입문자들이 시작하기에는 높은 진입장벽이 존재한다. 본 연구에서는 방 탈출 게임의 컨셉을 모의해킹에 적용하여 모의해킹 문제를 게임을 푸는 방식으로 접근하여 입문자들도 쉽게 모의해킹 분야를 시작할 수 있도록 하였다. 웹 서버는 오픈소스 웹 방화벽인 ModSecurity와 Spring Security로 서버보안을 강화하였다.

• 유공압시스템학회:학술대회논문집
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• 2010.06a
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• pp.1-6
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• 2010

Direct Drive Valves (DDV) with electric closed loop spool position control are suitable for electrohydraulic position, velocity, pressure or force control systems including those with high dynamic response requirements. The spool drive device is a permanent magnet linear force motor which can actively stroke the spool from its spring centered position in both directions. This basic study is carried out to drive the design parameters for developing a domestic DDV. The static and dynamic characteristics of DDV are examined. The simulation results are compared with data of manufacture's catalog to show the validity of the modelling.

• Proceedings of the KIEE Conference
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• 1999.07a
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• pp.357-359
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• 1999

It is necessary for the optimum design of switching devices to calculate repulsion forces acting on the closed electric contacts flowing over-current, e.g. inrush current and overload currents. In this paper, the forces generated by currents and flux densities at the contact point when circuit breakers are in closed position are obtained by using 3D finite element method. According to the analysis, the optimum configuration of wipe springs and arc extinguishing chambers are newly designed and consequently type tests show satisfactory results.

• Proceedings of the KIEE Conference
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• 2000.07b
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• pp.792-794
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• 2000

This paper describes the design and the analysis of electromagnetic system of Magnetic Switch using 2D parametric finite element method(EM-Pulse). Magnetic Switch is electrical equipment, which is widely used for switching on/off motors in industrial field. The transient state is simulated in order to calculate the response time of Magnetic Switch. The simulation is based upon a step-by-step integration of the electric circuit equations and the core movement. The contactor uses a permanent magnet for maintaining the closed state. The presented solution takes account of non-linear magnetic material property and spring force controlled by core position. The dynamic response of Magnetic Switch predicted by the simulation agrees closely with the required condition.

• Steel and Composite Structures
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• v.27 no.4
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• pp.465-477
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• 2018

In this research, vibration and smart control analysis of a concrete foundation reinforced by $SiO_2$ nanoparticles and covered by piezoelectric layer on soil medium is investigated. The soil medium is simulated with spring constants and the Mori-Tanaka low is used for obtaining the material properties of nano-composite structure and considering agglomeration effects. With considering first order shear deformation theory, the total potential energy of system is calculated and by means of Hamilton's principle in three displacement directions and electric potential, the six coupled equilibrium equations are obtained. Also, based an analytical method, the frequency of system is calculated. The effects of applied voltage, volume percent and agglomeration of $SiO_2$ nanoparticles, soil medium and geometrical parameters of structure are shown on the frequency of system. Results show that with applying negative voltage, the frequency of structure is increased.