• Journal of the Korean Society for Precision Engineering
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• v.29 no.1
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• pp.109-113
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• 2012

The LED failure rate greatly depends on the physical properties of packaging materials (epoxy). The glass transitions temperature (Tg) of the epoxy is one of the most important physical properties. Therefore, in the present study, various epoxies with high Tg were prepared and their failure shapes were analyzed. In addition, the failure shapes depending on the amount of epoxy and the wire bonding structure were measured. As a consequence, the lower failure rate was obtained with the smaller amount of epoxy. The safety of LED was improved with increasing the Tg of the epoxy.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.31B no.3
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• pp.60-68
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• 1994

In this paper, the multiplicative algorithm of two polynomials over finite field GF(($p^{m}$) is presented. Using the presented algorithm, the multiple-valued multiplier of the serial input-output modular structure by CCD is constructed. This multiple-valued multiplier on CCD is consisted of three operation units: the multiplicative operation unit, the modular operation unit, and the primitive irreducible polynomial operation unit. The multiplicative operation unit and the primitive irreducible operation unit are composed of the overflow gate, the inhibit gate and mod(p) adder on CCD. The modular operation unit is constructed by two mod(p) adders which are composed of the addition gate, overflow gate and the inhibit gate on CCD. The multiple-valued multiplier on CCD presented here, is simple and regular for wire routing and possesses the property of modularity. Also. it is expansible for the multiplication of two elements on finite field increasing the degree mand suitable for VLSI implementation.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.312-316
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• 2004

In this study, a spatial 3-dof haptic mechanism is implemented. The implemented mechanism does not employ the gear transmissions as velocity reducers for all three joints but uses wire-based transmissions, thereby it is able to minimize the frictions significantly. Also, by employing the structure of the four-bar mechanism to drive third joint from close to the base, the mechanism is able to minimize the inertia effect from the third actuator very effectively. Its kinematic analysis such as position and velocity analyses are performed first. Then, its operating software development, hardware implementation, and the related interfaces between a PC and the implemented Haptic device are completed. To evaluate its potential and its performance as a haptic device, a experiment generating a virtual constraint in a operational task space is conducted and preliminary results are discussed.

• Journal of Ocean Engineering and Technology
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• v.17 no.1
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• pp.33-40
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• 2003

기존 대부분의 진동제어법이 모드제어에 근거한 것인데 반면, 본 연구에서는 진동억제의 또다른 방법인 파동제어기법을 다루었다. 무반사조건을 만족하면서 진동에너지를 흡수하는 파동제어는 특히 1차원 구조계에 유용하게 사용될수 있으리라고 기대되는데, 현실적으론 제어알고리즘의 실현화에 그 어려움이 있다. 본 연구에서는 근사화된 무한구조계를 계산기내에 구축하여, 진동에너지가 근사 무한구조계에 흡수되는 조건을 제어기가 실현하는 제어수법을 개발하였다. 시뮬레이션과 실험을 통하여, 본 연구에서 제안한 파동제어기법에 의해 이동하는 현수체의 진동억제가 효율적으로 이루어짐을 확인할 수가 있었다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.05a
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• pp.359-362
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• 2003

Electrophoretic deposition (EPD) of alcohol YBCO suspensions on the Ag wire electrode is studied. Poly(ethylene glycol) was coordinated to a structure formed by the EPD process with YBCO particles. The suspension is characterized in terms of zeta potential and conductivity. The d.c electric fields of 200-300 V/cm are applied for 1-10 min. The optimal condition for the EPD allows modifying the properties and microstructure of the deposited films. Superconducting coatings with nanometer-sized pores and a preferred orientation along the c-axis were prepared from the result with chemically modified precursor solution. In contrast, YBCO coatings of submicrometer-sized pores and randomly orientated grains were prepared from the solution without PEG.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.12
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• pp.3148-3165
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• 1993

A cascade wind tunnel test for a turbine nozzle, which was designed for a small turbo jet engine in a previous study, has been conducted to evaluate its aerodynamic performance and losses. The large-scale blades were based on the mid-span profile of the nozzle. Oil film flow structure, and then 3-dimensional velocity components were measured in the flow passage with a 5-hold pressure probe, in addition to turbulent intensities at mid-span of cascade exit using a hot-wire anemometer. From this study, 3-dimensional growth of horseshoe and passage vortices in the downstream direction was clearly understood with near-wall flow phenomena. In addition, secondary flow and losses associated with the blade configuration were obtained in detail.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1087-1090
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• 2007

A wireless magnetic torque sensor is utilized to measure the torque generated in the rotating shaft in magnetic field without connecting to the shaft by any wire. In this study, a new wireless magnetic torque sensor was introduced. The structure of the sensor was explained detailed as well as its operation principle. Resulting from the torque measurement experiment results, the sensor was proven to measure the generated torque effectively. Compared with traditional contact torque sensor, the wireless one has low cost and good environment adaptation ability. Moreover, the intractable wrapping wires around the shaft are removed in this design. Hence the wireless torque sensor may be expected as a possible sensing device for many applications, such as the electric assisting rotation system in automobiles, the torque sensing system in motors, the arm rotation system in robotics and so on.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.25 no.1
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• pp.59-63
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• 2011

In small-power applications, variable-speed motors having high efficiency and controllability become more dominant than brushed DC motors. BLDC motors with permanent magnets in the rotor and SRMs directed by reluctance torque due to no permanent magnets have been strongly studied as a candidate. Compared to the BLDC motors, SRMs are more suitable for low-cost applications since the magnetic structure is simple, mechanically robust, and cheap due to no additional excitation in the rotor such as copper wire, aluminum, and permanent magnets. In addition, relatively small number of phases in single and two-phase SRMs allows more cost savings with regards to material in the motor and switching devices in the converter. In this paper, several 2 phase SRMs are compared to a 3 phase 6/4 SRM in terms of flux distribution in key parts of the motors.

• Journal of Biomedical Engineering Research
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• v.15 no.1
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• pp.1-8
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• 1994

Electrofusion of cabbage protoplasts was performed with a developed equipment which consists of a parallel wire electrode, a AC field generator, and a pulse generator. Exposure of protoplasts to an alternating current field of 450 KHz causes attraction to each other which leads to chains of protoplasts extending from the electrode. Intra-specific protoplast fusion was effectively induced within the pearl chains by the additional application of a single high-intensity DC square wave pulse of 1 KV/cm for 1-3 msec. To improve the performance, micro fusion electrode fabricated from the semiconductor technology and microcontroller based field an, d pulse generator was proposed. The viability of protoplasts after an application of electric field at optimum condition was reduced by only 5 % compared with that of pre-application. A prototype of fusion electrode, which consists of insulator-structure, was successfully fabricated by using photosensitive polyimide.

• Electrical & Electronic Materials
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• v.9 no.5
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• pp.483-489
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• 1996

Power transformer have many unsymmetrical structure and electric field is enhanced in that area. Those unsymmetrical area are not covered oftenly by solid insulating material which is used as a framework specially in gas transformer. By that result there is a possibility to decrease the total insulation class of the transformer. So in this study the electrical characteristic of $FC+SF_6$ mixture gas which is used as coolants for large power gas insulated transformer and its effects on electrical characteristics of structural material are investigated. Also breakdown characteristic with the tension of taping and curvature of the coil are studied which could be used as a design factor of large power transformer.