• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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• pp.893-899
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• 2014

X-band antenna has been widely used to effectively transmit the high resolution image data from the observation satellite to the ground station. To achieve above mission, X-band antenna is mainly composed of the 2-axis gimbal system using stepping motors and gears. However, the micro-vibration induced by the stepping motor actuation and the imperfect gear teeth alignment during this on-orbit operation is the main source of image quality degradation. In this paper, X-band antenna combined with a blade gear for micro-vibration isolation was suggested and investigated. The structural safety of the blade gear with low rotational stiffness was confirmed by structure analysis based on the derived torque budget. The isolation performance of the X-band antenna with the blade gear was verified through micro-vibration measurement test using the dedicated micro-vibration measurement device proposed in this study.

• 한국산업융합학회 논문집
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• 제16권3호
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• pp.95-102
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• 2013

It is indispensable to modern society metal processing since the industrialized rapidly, but it is a metalworking cutting fluid immediately. In addition, this means selecting a emulsion on the basis of quality criteria processing method, the material of the material, cutting depth, cutting speed, Djourou fence Liang, and surface roughness, cutting oil, the shape of the device based on the emulsion, I will be the structure of the tank, filtration equipment also changes. In particular, acting bacteria is now breeding in response to the passage of time due to metal ion degradation due to heat generated hydraulic fluid leakage, humidity tung, during processing, seep from processing material at the time of processing the water-soluble cutting oil for generating the malodor by dropping significantly the performance of the cutting oil to corruption from, sometimes by introducing various additives to suppress spoilage in advance. In this study, we expect the effect of the cost reduction in the extension of fluid replacement cycle through the application of the management apparatus and deep understanding in the management of cutting fluid, the working environment through the understanding and interest of workers in the production site more than anything I try to become useful for the improvement.

• 산업경영시스템학회지
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• 제30권3호
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• pp.103-108
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• 2007

This paper presents the conceptual framework for estimating and predicting system's susceptibility to failure as function of condition parameter value which is representing the current status of performance measure using on-line performance reliability. The performance of such system depends on one parameter with a probability distribution that degrades with time gracefully. Performance reliability represents the probability that physical performance will remain satisfactory over a finite period of time or usage cycles in the future. An empirical physical performance function is constructed to incorporate explanatory variables (operating and environmental conditions) over a time or usage dimension. This function enables one to model device performance and the associated classical reliability measures simultaneously, in the performance domain and time domain. The conditional performance reliability structure developed represents a tool to predict system performance over time or usage for next usage period. By enabling such a framework, it can bring us more efficient planning and execution in system's operation control as well as maintenance to reduce costs and/or increase profits.

• Corrosion Science and Technology
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• 제16권4호
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• pp.209-225
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• 2017

Development of high strength steel requires proper understanding of hydrogen behavior since the higher the steel strength the greater the susceptibility of hydrogen assisted cracking. This paper provides a brief but broad overview on hydrogen entry and transport behavior of high-strength ferritic steels. First of all, hydrogen absorption, diffusion and trapping mechanism of the steels are briefly introduced. Secondly, several experimental methods for analyzing the physical/chemical nature of hydrogen uptake and transport in the steels are reviewed. Among the methods, electrochemical permeation technique utilized widely for evaluating the hydrogen diffusion and trapping behavior in metals and alloys is mainly discussed. Moreover, a modified permeation technique accommodating the externally applied load and its application to a variety of steels are intensively explored. Indeed, successful utilization of the modified permeation technique equipped with a constant load testing device leads to significant academic progress on the hydrogen assisted cracking (HAC) phenomenon of the steels. In order to show how the external and/or residual stress affects mechanical instability of steel due to hydrogen ingress, the relationship among the microstructure, hydrogen permeation, and HAC susceptibility is briefly introduced.

• 한국표면공학회지
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• 제49권6호
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• pp.498-506
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• 2016

Electrochemical measurement using a LSCF6428 electrode was performed to estimate the oxygen potential gradient in the electrode layer and a long time stability test was performed by applied potential to learn the overpotential effect on the LSCF6428 electrode. By fitting the observed impedance spectra, it was obtained that the amount of faradic current decreased with distance from cathode/electrolyte interface. Oxygen potential gradient was estimated to occur within 1 um region from the cathode/electrolyte interface at an oxygen partial pressure of 10-1 bar. The segregation of cation rich phases in the LSCF6428 electrode suggests that kinetic decomposition took place. However, impedance response after applying the potential showed no changes in the electrode compared with before applying potential. The obtained results suggest that segregation of a secondary phase in a LSCF6428 cathode is not related to performance degradation for solid oxide fuel cells (SOFCs).

• ETRI Journal
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• 제27권6호
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• pp.691-696
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• 2005

In asynchronous transfer mode (ATM) networks, fixed length cells of 53 bytes are transmitted. A cell may be discarded during transmission due to buffer overflow or a detection of errors. Cell discarding seriously degrades transmission quality. The quality degradation can be reduced by employing efficient forward error control (FEC) to recover discarded cells. In this paper, we present the design and implementation of decoding equipment for FEC in ATM networks based on a single parity check (SPC) product code using very-large-scale integration (VLSI) technology. FEC allows the destination to reconstruct missing data cells by using redundant parity cells that the source adds to each block of data cells. The functionality of the design has been tested using the Model Sim 5.7cXE Simulation Package. The design has been implemented for a $5{\times}5$ matrix of data cells in a Virtex-E XCV 3200E FG1156 device. The simulation and synthesis results show that the decoding function can be completed in 81 clock cycles with an optimum clock of 56.8 MHz. A test bench was written to study the performance of the decoder, and the results are presented.

• 조명전기설비학회논문지
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• 제23권2호
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• pp.82-88
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• 2009

전력용 커패시터는 유도성 부하의 낮은 역률을 보상하기 위해 설치하는 경우가 많지만, 전력변환장치에서 발생하는 고조파를 줄이기 위해 수동형 필터로서 리액터와 함께 사용되는 경우도 있다. 수동형 필터는 커패시터와 리액터를 직렬로 연결하여 사용한다. 필터는 비선형 부하에서 발생하는 고조파를 흡수하는 역할을 하기 때문에 전압 및 전류 스트레스를 받아 소손 또는 열화되어 정상적인 수명을 보장받지 못하는 경우가 많다. 본 논문에서는 PWM 인버터의 전원측에 설치된 수동형 필터가 고조파를 저감할 때 받는 영향을 해석하였다.

• Journal of Power Electronics
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• 제6권1호
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• pp.18-28
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• 2006

The Electric Power Subsystem (EPS) is one of the most critical systems on any satellite because nearly every subsystem requires power. This makes the choice of power systems the most important task facing satellite designers. The main purpose of the Satellite EPS is to provide continuous, regulated and conditioned power to all the satellite subsystems. It has to withstand radiation, thermal cycling and vacuums in hostile space environments, as well as subsystem degradation over time. The EPS power characteristics are determined by both the parameters of the system itself and by the satellite orbit. After satellite separation from the launch vehicle (LV) to its orbit, in almost all situations, the satellite subsystems (attitude determination and control, communication and onboard computer and data handling (OBC&DH)), take their needed power from a storage battery (SB) and solar arrays (SA) besides the consumed power in the EPS management device. At this point (separation point, detumbling mode), the satellite's angular motion is high and the orientation of the solar arrays, with respect to the Sun, will change in a non-uniform way, so the amount of power generated by the solar arrays will be affected. The objective of this research is to select satellite EPS component types, to estimate solar array illumination parameters and to determine the efficiency of solar arrays during both detumbling and normal operation modes.

• 한국전기전자재료학회논문지
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• 제13권10호
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• pp.822-827
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• 2000

The Si-SiO$_2$interface trap and nitride bulk trap distribution of SONOSFET(polysilicon-oxide-nitride-oxide-semiconductor field effect transistor) NVSM (nonvolatile semiconductor memory) cell is investigated by single junction charge pumping method. The device was fabricated by 0.35㎛ standard logic fabrication process including the ONO stack dielectrics. The thickness of ONO dielectricis are 24$\AA$ for tunnel oxide, 74 $\AA$ for nitride and 25 $\AA$ for blocking oxide, respectively. By the use of single junction charge pumping method, the lateral profiles of both interface and memory traps can be calculated directly from experimental charge pumping results without complex numerical simulation. The interface traps were almost uniformly distributed over the whole channel region and its maximum value was 7.97$\times$10$\^$10/㎠. The memory traps were uniformly distributed in the nitride layer and its maximum value was 1.04$\times$10$\^$19/㎤. The degradation characteristics of SONOSFET with write/erase cycling also were investigated.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 추계학술대회 논문집
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• pp.17-20
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• 2001

Nonvolatile semiconductor memory devices with reoxidized nitrided oxide(RONO) gate dielectric were fabricated, and nitrogen distribution and bonding species which contributing memory characteristics were analyzed. Also, memory characteristics of devices according to anneal temperatures were investigated. The devices were fabricated by 0.35$\mu\textrm{m}$ retrograde twin well CMOS processes. The processes could be simple by in-situ process of nitridation anneal and reoxidation. The nitrogen distribution and bonding state of gate dielectric were investigated by Dynamic Secondary Ion Mass Spectrometry(D-SIMS), Time-of-Flight Secondary ton Mass Spectrometry(ToF-SIMS), and X-ray Photoelectron Spectroscopy(XPS). Nitrogen concentrations are proportional to nitridation anneal temperatures and the more time was required to form the same reoxidized layer thickness. ToF-SIMS results show that SiON species are detected at the initial oxide interface and Si$_2$NO species near the new Si-SiO$_2$ interface that formed after reoxidation. As the anneal temperatures increased, the device showed worse retention and degradation properties. These could be said that nitrogen concentration near initial interface is limited to a certain quantity, so excess nitrogen are redistributed near the Si-SiO$_2$ interface and contributed to electron trap generation.