• Journal of Biomedical Engineering Research
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• v.16 no.2
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• pp.239-248
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• 1995

The method of increasing signal to noise ratio (SNR) in a Hadamard transform spectrometer (HTS) is multiplexing. The multiplexing is executed by a mask. Conventional masks are mechanical or electro-optical. A mechanical mask has disadvantages of jamming and misalignment. A stationary electro-optical mask has a disadvantage of information losses caused by spacers which partition mask elements. In this paper, a mixed-concept electro-optical mask (MCEOM) is developed by expanding the length of a spacer to that of lon-off mask element. An MCEOM is operated by stepping a movable mask. 2N measurements are required for N spectrum estimates. The average mean square error (AMSE) using MCEQM is equal to that using a stationary electro-optical mask without spacers for large N. The cost of manufacturing an MCEOM is lower than that of producing a conventional electro-optical mask because an MCEOM needs only (N + 1)/2 on-off mask elements whereas the con¬ventional electro-optical mask needs N on-off mask elements. There are no information losses in the spectrometers having an MCEOM.

• Journal of the Korean Society for Precision Engineering
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• v.33 no.6
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• pp.485-490
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• 2016

This study focused on developing an electro-discharge truing method for the ELID grinding process using a metal-bonded grinding wheel. The truing process in grinding plays important roles in enhancing the quality of the ground surface. In this study, a reference current in the electro-discharge truing process was confirmed to be a viable solution for efficient truing through performance experiments. Current and voltage variation experiments were carried out and the variation output data were collected with a monitoring program to understand the electrodischarge phenomenon that occurs between metal-bonded grinding wheels and copper electrodes. The experimental results showed that as the reference current decreased, the average electro-discharge energy decreased. Therefore, the reference current can be used as an indicator to estimate the size of the gap between the truer and grinding wheel.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.184-187
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• 2005

Physical changes in a structural system may cause changes in mechanical impedance of the system. Due to the electro-mechanical coupling effect in piezoelectric materials, this change can be monitoring by the electrical impedance of the piezoelectric sensor. In this paper, the variability of electro-mechanical impedance caused by temperature effect is assessed to adjust impedance data used for EMI based damage detection in beams. First experiments on beams are described. Next, experiments were performed under the temperature varying condition, in the range of $3^{\circ}C\;to\;23^{\circ}C$. Finally, the relationship between temperatures and impedance signatures is analyzed empirically temperature-frequency patten for the test structure.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.10a
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• pp.991-994
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• 1995

Recent trend in machine tools is pursuing the high precision and high speed facility and its architecture is being more complicated. With this tendency, it is required the more precise dynamic analysis of electro-mechanical system in machine tools. In this paper, the exact mathematical model of feed and spindle system of a typical machine tools was induced. The feed system is modeled as 7-mass system including the workpiece and the spindle system as 4-mass system. The simulation results show that the induced model depicts the characteristics of real system very well. The effects of each mechanical element to dynamic motion of a machine are analyzed by simulation with the induced model. It ia anticipated that the induced model can be used in the analysis of various machine architectures and in the design stage of new machine tools.

• Journal of Advanced Marine Engineering and Technology
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• v.21 no.2
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• pp.195-205
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• 1997

The propulsion marine diesel engine have been widely applied with a mechanical- hydraulic governor to control the ship speed for long time. But it was recently very difficult for the mechani¬cal - hydraulic governor to control the speed of engine under the condition of low speed and low load because of jiggling by rough fluctuation of rotating torque and hunting by dead time of Desiel engnie The performance improvement of mechanical - hydraulic governor is required to solve these problems of control system. The electro - hydraulic governor using PID algorithm is provided to compensate the faults of mechanical- hydraulic governor. In this paper, in order to analyze the ship speed control system, the transfer function was converted from the z tansformation to w transformation. The influence of dead time changing by engine speed which induces hunting phenomena was investigated by Nichols chart of w plane. As a method of performance improvement of mechanical hydraulic governor, a Eletro - hydraulic governor shows that fine control results can be obtained through optimal parameter tuning of PID

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.1010-1015
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• 2008

The rapid wear rate of cutting tools due to high cutting temperature is a critical problem to be solved in machining of hardened steel. Application of cutting fluid influences the performance of machining because of its lubrication and cooling actions. But, the environmental concerns call for the reduced use of cutting fluids in machining operations. Near-dry machining such as minimum quantity lubrication is regarded as one of the solutions to this difficulty. In the present work, cutting fluid was applied as a high velocity jet at the machining zone continuously at an extreme low rate using a fluid application system developed namely Electro Static Lubrication (ESL) during drilling of hardened steel. The performance of ESL has been compared with that of dry and MQL (minimum quantity lubrication) machining.

• Smart Structures and Systems
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• v.26 no.5
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• pp.631-640
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• 2020

In this paper, nonlinear vibration behaviors of multi-phase Magneto-Electro-Elastic (MEE) doubly-curved nanoshells have been studied employing Jacobi elliptic function method. The doubly-curved nanoshell has been modeled by using nonlocal elasticity and classic shell theory. An exact estimation of nonlinear vibrational behavior of smart doubly-curved nanoshell has been obtained via Jacobi elliptic function method. This method can incorporate the influences of higher order harmonics leading to an exact estimation of nonlinear vibration frequency. It will be indicated that nonlinear vibrational frequency of doubly-curved nanoshell relies on nonlocal effect, material composition, curvature radius, center deflection and electro-magnetic field.

• Journal of Drive and Control
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• v.11 no.4
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• pp.1-7
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• 2014

This paper presents the development of a compact position generator to be used for industrial purposes based on a pump controlled Electro-Hydraulic Actuator (EHA), which is closed-loop controlled by an embedded based Iterative PID controller. The controller is designed by combining the PID controller and the iterative learning scheme to perform tracking control for periodically desired references. Control algorithm is implemented on an embedded computer (AD 7011-EVA) which makes the implementation and application in industrial environments easier.

• Proceedings of the KIPE Conference
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• 2003.07a
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• pp.430-433
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• 2003

IGBTS are widely used for the industrial inverters in the mid power range at low voltage (440V$\~$660V) application. Advantageous features of the device are simple gate drive and high speed switching capability. Due to these advantages the application of IGBTS is enlarging into the high power application. However, to increase the power handling capacity at lower input voltage level, the current rating in each bridge arm must be enlarged. Therefore the parallel operation of IGBT devices is essentially needed. This paper describes the feasible parallel structures of the power circuit for the mid & the high power inverters and introduces the important design condition for the parallel operation of IGBT devices. To verify feasibility of the IGBT parallel operation, the feature of several IGBT devices (EUPEC, SEMIKRON's IGBT) are investigated and the power stacks are implemented and tested with these devices. The experimental results show the good characteristics for the parallel operation of IGBTS.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.798-799
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• 2011

온라인 전기버스용 전동기는 차량의 운전특성을 고려하여 가속성 향상을 위한 높은 기동토크가 요구되며, 넓은 속도영역 운전을 위한 약계자 제어성능이 우수해야 한다. 특히 전동기의 최대 동작속도가 배터리 전압에 의해 결정되므로, 고속 운전영역 확보를 위해 전압제한을 고려한 전기설계가 필요하다. 본 연구에서는 정격속도 대비 최대속도의 비가 1:4로서 넓은 약계자 영역이 요구되는 온라인 전기버스용 전동기에 대해 개념설계를 진행하여 Active Part의 치수를 산출하고, 고정자 권선의 턴수 및 회전자 형상 변화에 따른 전압 및 출력특성을 비교 분석하여, 온라인 전기버스용 전동기에 요구되는 약계자 제어특성을 만족하도록 설계안을 도출하였다. 또한 전동기의 고속 동작시 주 손실인 철손에 의한 온도상승을 고려하여 영구자석의 감자안정성을 분석하였으며, 전자장 FEM 해석을 적용하여 설계결과의 타당성을 검증하였다.