• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.117-117
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• 2012

반도체 및 디스플레이 공정등에서 고진공 및 급 배기 환경을 제공하기 위하여 사용되는 터보 분자펌프(Turbomolecular Pump, TMP)는 다층의 회전깃을 갖는 로터를 회전시켜 분자를 배출시키는 방식을 사용하는 진공펌프이다. 또한 최근에는 디스플레이 및 반도체 공정에서 높은 진공도뿐만 아니라, 높은 배기속도를 요구하는 추세에 따라, 터보 펌프와 드래그 펌프부분을 동시에 가지고 있어 상대적으로 작동 진공도 영역이 넓은 복합 분자펌프(Compound Turbomolecular Pump, CMP)의 활용도가 넓어지고 있다. 이러한 분자펌프가 장시간의 고속회전에 적합하고, 베어링에서의 오염을 없앨 수 있는 비접촉 방식인 자기부상 방식이 주로 적용된다. 자기베어링 시스템은 하드웨어와 소프트웨어로 나누어질 수 있는데, 하드웨어는 회전하게 되는 블레이드로터 및 자기베어링 로터, 모터 로터 등이 포함된 축과 고정되어 있는 자기베어링 코어와 코일, 변위센서 등의 펌프 하우징 부분, 또한 이를 제어하기 위한 전력 증폭 시스템 등의 기전적인 요소들이 이루어져 있다. 소프트웨어라 할 수 있는 제어시스템에 있어서 자기베어링이 불안정한 특성을 갖는 개루프계를 갖고 있으므로 안정화를 위한 능동제어 시스템이 필수적이며 진동 제어 등의 기능을 갖도록 적용된다. 따라서 이러한 복합분자펌프의 성능은 이러한 시스템을 구성하는 개별 요소의 성능과 이를 통합한 제어시스템의 성능이 결정한다고 할 수 있다. 본 논문에서는 현재 개발중인 2,500 l/s급의 자기부상형 고진공 복합분자펌프의 시작품에 대하여 고속회전의 안정성에 대한 연구를 수행한 내용을 보고하고 있다. 디지털 제어시스템을 적용한 시작품의 최대 26,000 rpm 까지의 고속회전시의 회전 응답 및 진동 특성을 측정 분석하였으며, 로터의 고유진동수 및 진동 모우드를 분석하였다. 또한 연속 작동시의 발열특성과 각 부분의 온도와 회전 안정성과의 관계를 평가하였다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.9
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• pp.789-794
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• 2014

The FPGA is used to the high speed digital satellite communication on the Digital Signal Process Unit of the next generation GEO communication satellite. The high capacity FPGA has the high power dissipation and it is difficult to satisfy the derating requirement of temperature. This matter is the major factor to degrade the equipment life and reliability. The thermal control at the equipment level has been worked through thermal conduction in the space environment. The FPGA of CCGA or BGA package type was mounted on printed circuit board, but the PCB has low efficient to the thermal control. For the FPGA heat dissipation, the heat sink was applied between part lid and housing of equipment and the performance of heat sink was confirmed via thermal vacuum test under the condition of space qualification level. The FPGA of high power dissipation has been difficult to apply for space application, but FPGA with heat sink could be used to space application with the derating temperature margin.

• Journal of Korea Foundry Society
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• v.38 no.2
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• pp.48-54
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• 2018

To improve the durability of the turbocharger, it is important to suppress cracking of the turbine housing; therefore, we investigated the initiation and growth of these cracks. First, we initiated a crack in the turbine housing using endurance experiments. After the endurance test, cracks mainly occurred in the valve seat, the nozzle area, and the scroll part of the turbine housing. The results of a fracture analysis of the cracks showed that cracks in the valve seat were initiated by fatigue fracture. This seems to be caused by the accumulation of mechanical and thermal stresses due to vibration of the turbine wheel and high-temperature exhaust gas. Also, cracks in nozzle and scroll area were initiated by intergranular corrosion due to the exhaust gas. Thus, although there are differences in the cause of initiation according to the site, a concentric waveform was observed in all fracture planes. This phenomenon indicates that cracks gradually grow due to repeated stress changes, and the main causes are the temperature difference of the exhaust gas and the vibration caused by the turbine shaft.

• The Journal of the Korea Contents Association
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• v.20 no.3
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• pp.209-222
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• 2020

The purpose of this paper is to predict the future changes of housing through the Delphi technique. The targets to predict were set by housing type, housing space, housing demand, and architectural technology. The results were as follows: ① The influences of social and value perspectives on the change of housing type, space, and demand would be high, on the other hands, the influence of political perspective would be low. ② In terms of housing type, the increase in demand for downsizing housing for high-rise buildings and the possibility of realizing remote medical support services and homecare using big data are highly predicted. That is, ③ it is anticipated that IoTs will have a significant influences on future housing changes, and ④ enactment of co-housing and related laws by the sharing economy, services for maintenance through the supply of high-rise and high-density homes, housing support for residents, and advanced lease markets by developed architectural technology are expected as anticipated forms of future housing.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.10a
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• pp.910-912
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• 2015

In this paper, we designed the novel capacitive sensor and system for measuring the position of the piston in hydraulic cylinder. The magnetic or LVDT sensors have been widely used to measure the position of the piston because of its high accuracy, but these types of sensor are very expensive and have difficulty in use because of its complexity. To overcome these disadvantages, we studied the optimized non-contact capacitive sensor and designed detecting system for accurate measuring the location of piston in hydraulic cylinder. The proposed capacitive sensor and detecting system have the possibility of practical use for hydraulic cylinder through experiments.

• Journal of Satellite, Information and Communications
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• v.5 no.2
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• pp.82-86
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• 2010

In this paper, a power amplifier module for WCDMA base-station applications is designed and implemented using GaN field-effect transistors (FETs), which uses an envelope tracking bias system. The designed module consists of an high gain MMIC amplifier, a driver amplifier, a power amplifier, and bias circuits for envelope tracking applications. Especially, a FET bias sequencing circuit and two isolators are integrated for stable RF operations. All circuits are assembled within a single housing, so its dimension is just $17.8{\times}9.8{\times}2.0\;cm3$. Measured results show that the developed power amplifier module has good envelope tracking capability: the power-added efficiency of 35% at the output power range from 30dBm to 40dBm over a wide range of drain bias.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.2
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• pp.190-195
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• 2009

This paper introduces experimental investigates of an electrical accident of the distributing cable termination with simulated a shoddy construction. We prepared two termination kites, one is built-in type, the other is heat contraction type. Also, we manufactured cable termination that have simulated defect by badness construction and investigated their insulation characteristics such as ac (35[kV], 1[min]) and impulse (95[kV], $1.2{\times}50[{\mu}s]$) withstand test. The influence of defects such as thickness decrease, the gap between stress-con of housing and semiconductor and heating time on insulating properties of the termination have been studied. The thickness decrease of an insulator decreases ac breakdown strength suddenly and the breakdown traces of the insulator that is damaged by knife displayed elliptic shape. The gap of between stress-con and semiconductor deteriorates dielectric strength of insulator seriously. In heat contraction type, the ac breakdown voltage became low when the heating time is short.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.12
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• pp.2489-2497
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• 1994

This paper presents the development of a 10 W solid-state hybrid power amplifier(SSPA). operating over $7.7\sim8.5GHz$. The fabrication and measurement of this amplifier are performed with 3 sections, such as the front one for high gain, the middle one for driving, and high power one, to minimize the risk of failure and to increase the easiness of development. and then the final amplifier is realized by connecting 3 sections above mentioned, DC bias circuit, and temperature compensation circuit on one housing. Total small signal gain obtained is about $45\pm1dB$, the input and output return losses are 25 and 27 dB respectively. The output power measured at 1 dB gain compression point for 3 frequencies at 7.7, 8.1, and 8.5 GHz are $39.8\sim40.4dBm$, which is about 10 W. and the 3rd-order harmonic powers of 2 tones test are 13.34 dBc at output power 37.5 dBm. These obtained results satisfies the initially required specification. and the realized SSPA can be installed as a subsystem of the microwave transponder for telecommunication.

• Journal of the Institute of Electronics and Information Engineers
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• v.54 no.6
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• pp.117-122
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• 2017

Cabin noise due to the electric powertrain of electrical vehicle may consists of motor noise caused by electrical mismatch and gear noise coming from reduction gearbox. These sound may be considered rather small noise compared to those of internal combustion engine, but without masking effect, the noise can be more annoying for customer. Thus, this paper demonstrates the characteristics of electrical vehicle powertrain noise, and the effect of passive damping material for the noise reduction. The typical motor noise can be affected by the motor torque. Also, it is demonstrated that the reduction gearbox may be a weak point for the noise path compared to the motor housing. With vehicle test, it is shown that the damping patch is more effective for noise reduction with deceleration condition than with acceleration condition.

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• 2007.11a
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• pp.353-357
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• 2007

The Apartment resident's make-up of a family and residing preference are diversified by the change of lifestyle through the elevation of economy level and residing level. Accordingly, the remodeling and the early rebuilding for the satisfaction of a life cycle and a life style are increasing, and "Variability" that is the concept of Open Housing was emphasized as a central of residing plan in the apartment. Although apartments which select the space variability to the residing space are increasing gradually, the optimum composition structural system with space variability that satisfies the structure stability, the economical efficiency and the resident usability is not developed. The method of a study was progressed by a comparison and an analysis on each system with estimation elements through analyzing the development process and the special quality of existing composition structural system with space variability in the apartment. This paper offered the improvement direction on the current composition structural system with space variability for the development of modularizing system that is correct in domestic real condition.