• Proceedings of the KIEE Conference
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• 1998.11c
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• pp.761-763
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• 1998

In this paper, Co-Cr thin films which are known for a excellent perpendicular magnetic recording media were prepared. Changing target- substrate distance, Ar gas pressure and arriving atoms, the incident angle and c-axis orientation properties by using the facing targets sputtering system. We evaluated the c-axis dispersion angle by measu ring half-height width with Micro area X-Ray Diffractometer, measured the thickness of thin film with Ellipsometer. The magnetic properties were compared measuring in-plane squareness and perpendicular coercivity with vibrating sample Magnetometer.

• Electrical & Electronic Materials
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• v.8 no.1
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• pp.13-20
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• 1995

To develope a high precision TiAIN thin film resistor, TiAIN films were deposited on A1$_{2}$03 substrates by reactive planar magnetron cosputtering from Ti and Al targets in an Ar-N$_{2}$ atmosphere. The characteristics of the TiAIN thin film were controlled by changing of the R.F. power on Ti and Al targets, and the N$_{2}$ partial pressure. The high precision TiAIN thin film resistor with TCR(Temperature Coefficient of Resistance) of less than 10ppm/.deg. C was obtained under the R.F. power condition of 160(w)/240(w) to Ti and Al targets at the N$_{2}$ partial pressure of 7*10$^{-5}$ Torr. The composition of these films were investigated by XRD, SEM and EDS.

• Journal of Ocean Engineering and Technology
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• v.12 no.2 s.28
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• pp.79-86
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• 1998

A three-dimensional WIG (Wing In Ground effect) moving above free surface is numerically studied by means of finite difference techniques. The air flow field around the WIG is analyzed by MAC (Marker & Cell) method, and interactions between WIG and the free surface are appeared as the variation of pressure distribution acting on the free surface. To analyze the wavemaking phenomena by those pressure distributions, the NS (Navier-Stokes) solver is employed in which nonlinearities of the free surface conditions can be included. Through the numerical simulation, Cp values and lift/drag ratio are carefully reviewed by changing the height/chord ratio. The section shape of model is NACA0012 with the span/chord ratio of 3.0. Through computational results, it is confirmed that the effect of free surface is small enough to treat it as a rigid wavy wall.

• 유체기계공업학회:학술대회논문집
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• 2000.12a
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• pp.285-292
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• 2000

Numerical calculation is applied to centrifugal pump at design condition by using commercial code STAR-CD and Tascflow, and these results are compared with experimental data at impeller outlet. Numerical analysis is also performed by changing turbulence model and discretization scheme at design condition using Tascflow. Turbulence model and discretization scheme used to Tascflow are k-$\epsilon$, k-$\omega$ turbulence model and upwind, modified linear profile scheme. W;th the same turbulence model and discretization scheme, two results of STAR-CD and Tascflow are very similar. But there is significant difference in numerical results near hub and shroud of impeller with different kinds of turbulent model and discretization scheme at design condition. And with k- $\omega$ turbulence model and modified linear profile scheme, it is showed that numerical results are very similar to experimental results of impeller outlet

• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.12
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• pp.961-967
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• 2009

A 3-dimensional numerical investigation of a WIG effect vehicle with DUP (direct underside pressurization) is performed to predict aerodynamic characteristics and the static height stability. DUP can considerably reduce take-off speed and minimize the hump drag while the vehicle accelerates on the water to take off. The DUP of the model vehicle, Aircat, consists of a propeller in the middle of the fuselage and an air chamber under the fuselage. The air accelerated by the propeller comes into the camber through the channel in the middle of fuselage and augments lift by changing its dynamic pressure to static pressure dramatically. However, the air accelerated by a propeller produces excessive drag and reduces static height stability.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.476-479
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• 1997

A Knowledge of friction force in pneumatic cylinders makes it possible to improve cylinder description during simulation and to asses performance under changing operating conditions more accurately. Such knowledge is particularly useful, for example, when modeling continuous pneumatic positioning systems or predicting the operating conditions under which stick slip may occur, as well as in establishing preventive maintenance procedures for pneumatic cylinders. Friction force depends on a number of factors, including operating pressure, seal running speed on the cylinder barrel and rod, barrel material and surface roughness, seal dimensions and profile, seal material, lubrication conditions, cylinder distortion during assembly, and the operating temperature of cylinder components. This paper shows a system for measuring the friction force caused by a seal used in pneumatic cylinders. Results of experimental tests show that seal friction forces for grease lubricated service are clearly dependent on speed and pressure and are les sensitivity to other parameter. i.e., barrel material and roughness, seal material, and profile.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.10 no.2
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• pp.64-72
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• 2001

Weld line is one of serious troubles which are observed in a plastic part manufactured by a injection molding process. This is caused by many process factors, which are molding pressure, temperature, velocity, location of a injection gate, mold geometry and material properties. investigation on the effects of these process factors to the appearance of a weld line was carried out using a finite element method. Filling and packing analyses were carried out by modifying both the configuration of the injection gates and cavity thickness. Proper locations of the injection gates could be determined by considering molding pressure, temperature, velocity and frozen layer, and whereby the weld line was controled. In order to make a weak appearance of the weld line, flow velocity and flow front in a cavity were also investigated by modifying a cavity thickness. As a result, flow front was extended around the corner in the cavity by changing the flow velocity and hence the appearance of the weld line was much weakened.

• Journal of the Korean Society for Precision Engineering
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• v.10 no.1
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• pp.114-125
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• 1993

Thermoelastoplastic analysis of a typical device consisting of fixed tube and movable case having an inital clearance in between, which is subjected to pressure and thermal load, has been carried out to examine the cause of malfunction mainly at high temperature condition, and to improve the design. Stresses, deformed shape, interface state and their effects on normal function of case are discussed by using finite element method. The extraction energy can be remarkably reduced by changing the configuration of tube from the present design (Parallel type) to the improved design (Tapered type). This effect has been proved by sustained cyclic function test.

• Journal of Advanced Marine Engineering and Technology
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• v.27 no.3
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• pp.388-394
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• 2003

Hydraulic system is difficult to obtain a suitable performance due to the nonlinearity load pressure change and system parameter variation. The requirement of control a1gorithm has been complex in order to satisfy the performance. The adaptive control is a control method which is suggested to achieve the control object under the plant characteristics change. In spite of the case that plant characteristics and the degree of variation are difficult to grasp. the adaptive control could keep the characteristics of closed-loop system generally. In this study. a method of combined generalized minimum variance adaptive control (GMVAC) and output error feedback is proposed, in order to solve the problem of non-minimum phase of plant and the vibration and overshoot in initial response. The control performance according to the variation of characteristics of plant is evaluated by changing the supply pressure. The experimental results show the effectiveness of the proposed scheme.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.783-788
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• 2000

Flow fields in two-dimensional plane channels with thin obstacles("baffles and blocks") mounted symmetrically in the vertical direction and periodically in the streamwise direction are studied numerically to understand how various geometric conditions influence the critical Reynolds number and pressure drop. Changing BR(the ratio of channel to baffle interval) from 1:1 to 1.5, we computed the critical Reynolds number and pressure drop. Especially when BR is 1:3, at which the critical Reynolds number turned out to be minimal, we added blocks in the geometry in order to study their destabiliting effects on the flows.