• International Journal of Aeronautical and Space Sciences
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• v.3 no.2
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• pp.13-23
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• 2002

In this paper, we present a sliding mode control strategy for the re-orientation maneuver of rigid spacecraft containing rotating wheels. The wheels are considered as internal devices, and external inputs are employed for generation of control commands. The formulation is developed for a general case while particular example is applied to pitch bias momentum spacecraft with a single momentum wheel. The resultant control commands are used to take the gyroscopic effects into account which are caused by the rotating wheels. The controller designed demonstrates that the nutational motion of the pitch bias momentum spacecraft is effectively controlled. It is also assumed that the external control torque device is of on-off nature, and pulse width modulation technique is applied to construct proper control torque history.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.28 no.3
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• pp.78-83
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• 2014

To minimize the financial loss due to power facility malfunction, on-line diagnostic techniques are required to grasp any abnormal state of facilities in the live line as well as devices to diagnose abnormal states of power facility in an easy and prompt manner. This study aims to develop a portable UV detecting system by means of UV sensors for easier and efficient inspection of the degradation state of power facility in a long distance. Accordingly, it includes a simulation of corona discharges that may occur due to degradation of power facility and detection of ultraviolet pulse generation depending on the corona discharge intensity and measuring distance in application of UV sensors. Additionally, the optimal algorithm is determined for its application to the system's degradation diagnosis program based on the measured experiment data.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.9
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• pp.37-44
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• 2001

Ultrasonic testing has a characteristics such as excellent permeability, high-sensitivity to find defect and an almost exact measurement for position. size and direction of inner defect, which differ from other non-destructive testing. In the study, we developed program into optimal testing condition, to distinguish obstacle echo and defect position. This program shows generation and processing of ultrasonic pulse. We compared simulation with ultrasonic test in 45$^\circ$, 60$^\circ$and 70$^\circ$transducer. Test results were in accordance with simulation within 0.1~7.2%.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07a
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• pp.40-42
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• 2002

Electromigration is atomic diffusion driven by a momentum transfer from conducting electrons. With every new generation of intergrated circuits, interconnect line widths have been reduced and current densities in the interconnect have become higher. This leads to an increase in the threat to interconnect reliability due to electromigration. In this paper, we simulated stress evolution with changing temperature, duty factor(ratio of on time and pulse time), frequency under pulsed DC condition. As a result, we predict MTF(median time to failure) and found that exponent n is affected by changing temperature, duty factor.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.10
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• pp.914-920
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• 2002

This study investigates the mechanism of a dual mode probe that generates both of the longitudinal and shear waves simultaneously with a single FZT element. Most of conventional ultrasonic probes are constructed to generate either longitudinal or shear waves. After poling, PZT has the hexagonal 6mm crystal symmetry. All possible crystal cuts are checked to determine appropriate Euler transformation angles for efficient excitation of dual modes. For the selected cut, performance of the dual mode element is analyzed through numerical simulation and experiments. Results of the analysis determine the optimal crystal cut for simultaneous generation of P and S waves of equal strength.

• Proceedings of the KIEE Conference
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• 1999.07f
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• pp.2502-2504
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• 1999

In $CO_2$ arc welding, which is generally used for steel Panel of chassis parts, spatters cause many troubles. This paper represents the Pulse MAG arc welding to limit spatter generation, which is controlled output current instantaneously. And the system designed in this Paper is the digital controller using DSP.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.174.4-174
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• 2001

Vehicle stability control system can enhance the vehicle stability and handling in the emergency situations through the control of traction and braking forces at the individual wheels. To achieve the desired performance, the wheel slip controller manages the hydraulic braking system to generate the desired braking force at each wheel. In this study, we propose the wheel slip controller for the generation of the braking forces based on multiple sliding mode control theory with the pulse width modulation. The proposed controller follows to the slip ratio and the brake pressure the desired ones so that the vehicle stability controller can Intervene braking force at each wheel. We show the validity and usefulness of the proposed controller through computer simulations.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.774-779
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• 2003

Arc-shaped line array slits have been used for the laser generation of focused Lamb waves. The spatially expanded Nd:YAG pulse laser was illuminated through the arc-shaped line array slit on the surface of a sample plate to generate the Lamb waves of the same pattern as the slit. Then the generated Lamb waves were focused at the point of which distance from the slit position is dependent on the curvature of slit arc. The proposed method showed better spatial resolution than the conventional linear array slit in the detection of laser machined linear defect and drill machined circular defect on aluminum plates of 1mm thickness.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.118-123
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• 2001

The linear compressor have been widely used for pressure wave generation in the Stirling cryocooler and Stirling type pulse tube cryocooler for tactical purpose. The linear compressor has small and compact structure, and long life due to having non-contact sealing mechanism. and the pressure drop through regenerator was ver important role in the motion of displacer in the expander of the Stirling cryocooler. In this study, the characteristic of the linear compressor and the pressure drop through regenerator in the expander was experimentally investigated. The results show the resonance of the compressor is very important to get maximum performance. and the gas spring force in the compression space of the compressor has effect on the characteristic of reonance. and the results show the pressure drop through regenerator is very small than operating pressure change.

• Journal of the Korea Society for Simulation
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• v.10 no.1
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• pp.25-34
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• 2001

In this paper, we describe the generation method of interface logic which replace between IP & IP handshaking signal with asynchronous logic circuit. Especially, we suggest the new asynchronous sequential "Waveform to VHDL" code creation algorithm by flow chart conversion : Wave2VHDL - if only mixed asynchronous timing waveform is presented the level type input and pulse type input for handshaking, we convert waveform to flowchart and then replace with VHDL code according to converted flowchart. Also, we confirmed that asynchronous electronic circuits are created by applying extracted VHDL source code from suggest algorithm to conventional domestic/abroad CAD Tool, Finally, we assured the simulation result and the suggest timing diagram are identical.