• Journal of The Institute of Information and Telecommunication Facilities Engineering
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• v.2 no.4
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• pp.17-27
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• 2003

This paper presents the channel estimation method with STBC applied to IEEE802.11a. Tenacious channel estimation method for OFDM system, that generally uses STTC, has been presented once and massive amount of calculation was needed However, regarding this paper, the amount of calculation can be reduced by using Curve Fitting, and channel tracking performance improvement can be achieved Based on the estimation method, computer simulation was done for the performance analysis and delay spread Doppler frequency and many other group sizes and numbers were considered As a result of the testing, we found out that Doppler frequency deviation effects equally as frequency offset. Also compared to the existing technique, channel estimated performance confirmed that have 0.9dB SNR improvement than old method.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.118-119
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• 2009

This paper presents the feature profile evolution silicon deep trench etching, which is very crucial for the commercial wafer process application. The silicon deep trenches were etched with the SF6 gas & Hbr gas based process recipe. The optimized silicon deep trench process resulted in vertical profiles (87o~90o) with loading effect of < 1%. The process recipes were developed for the silicon deep trench etching applications. This scheme provides vertically profiles without notching of top corner was observed. In this study, the production of SF6 gas based silicon deep trench etch process much more strongly than expected on the basis of Hbr gas trench process that have been investigated by scanning electron microscope (SEM). Based on the test results, it is concluded that the silicon deep trench etching shows the sufficient profile for practical MOS FET silicon deep trench technology process.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.88-89
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• 2009

In this paper, we investigated about wet cleaning effect as deep trench formation methods for Power chip devices. Deep trench structure was classified by two methods, PSU (Poly Stick Up) and Non-PSU structure. In this paper, we could remove residue defect during wet. cleaning after deep trench etch process for non-PSU structure device as to change wet cleaning process condition. V-SEM result showed void image at the trench bottom site due to residue defect and residue component was oxide by EDS analysis. In order to find the reason of happening residue defect, we experimented about various process conditions. So, defect source was that oxide film was re-deposited at trench bottom by changed to hydrophobic property at substrate during hard mask removal process. Therefore, in order to removal residue defect, we added in-situ SCI during hard mask removal process, and defect was removed perfectly. And WLR (Wafer Level Reliability) test result was no difference between normal and optimized process condition.

• Design & Manufacturing
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• v.6 no.1
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• pp.39-44
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• 2012

Hot tool steel, in general, has not been used as a material in hot forging. However such a hot tool steel is recently applied to forging materials by recent forging technology. DH32 is known as a kind of hot tool steels, which is developed for characteristics of excellent strength and toughness in high temperature. Feasibility of DH32 to hot forging material has been researched to develop the hot forging technology of a plunger used for a large-sized marine fuel pump. Hot compression experimental works were performed to investigate the hot strain characteristic of DH32 and with the experimental results FE simulations were also conducted for the design of forging processes and preform. It is found out through the hot compression experimental works that DH32 has a hot brittleness at more than $1150^{\circ}C$.

• Proceedings of the KIEE Conference
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• 2008.10b
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• pp.337-338
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• 2008

2008년 현재 우리나라는 10%의 인구가 60세 이상인 이른바 고령사회에 접어들었다. 노인 인구의 증가로 인해 노인이 여가생활 또는 일반생활을 보조하기 위한 보행 보조기에 대한 관심이 증가되고 있다. 대부분 동력이 없는 보행보조기를 사용하고 있으며 이러한 기구는 경사로 공간 또는 힘이 약한 노인들에게 취약성을 가지고 있다. 이에 동력형 보행보조로봇에 관심이 증가하고 있다. 동력형 보행보조로봇 역시 경사로에 있어서 편리성과 안전성을 높이기 위한 연구가 필요한 실정이다. 이에 본 논문에서는 보행보조로봇이 경사로에 진입 하였을 경우 기울어진 경사로의 정도를 인식하여 모터를 제어 한다. TILT 센서를 이용하여 기울이짐 정도를 측정 하였고, 또한 로봇의 전류 실시간으로 체크하여 로봇의 안전성을 향상 하였다. 제어 시스템 구성은 사용자의 보행의지를 파악하기위해 FSR 센서를 부착하여 조향장치로 사용하였으며, 경사로를 인식하기 위해 Liquid 타입의 TILT 센서를 사용하였으며, 모션 제어를 위해 DSP를 사용하였다. 본 제어 시스템을 보조보행로봇에 적용하였을 때, 보행보조로봇이 오르막 경사로에 진입시 기존보다 힘을 적게 사용하여 경사로를 진행하였으며, 경사로에서 브레이크 작동속도가 향상 되었다. 또한 내리막 경사로에서는 모터의 힘을 적게 사용하고 중력의 힘을 사용하여 이를 통해 전류의 소비량을 개선 하였다.

• Journal of the Korean Society for Heat Treatment
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• v.17 no.2
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• pp.101-105
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• 2004

After extrusion, cold rolling and T-6 treatment, texture development of 7x1x Al-alloy with 0.1% Sc is studied. During extrusion the very strong <111>+weak <100> fiber texture is developed, which is Influenced on the formation of rolling texture. The texture after 80% cold rolling can be described by strong{112}<111>(Cu)+{123}<634>(S) component in the cross section of the extruded rod, the strong -fiber+weak{110}<001>(Goss) components in the longitudinal section, and the strong {110}<112>(Bs)+weak{001}<100>(Cube) components in the transverse section. The components of rolling texture are remained after T-6 treatment, but the maximum density of ODF is higher. The calculated mean r-values and the planar anisotropy are relatively high, which are dependent on the texture. After T-6 treatment, recrystallized equiaxed grains with average grain size of $1{\sim}2{\mu}m$ are obtained.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.5 no.11
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• pp.1891-1908
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• 2011

Cyber-physical systems (CPSs) are an emerging discipline that involves engineered computing and communicating systems interfacing the physical world. The widespread applications of CPSs still face enormous challenges because of the lack of theoretical foundations. In this technical survey, we review state-of-the-art design techniques from various angles. The aim of this work is to provide a better understanding of this emerging multidisciplinary methodology. The features of CPSs are described, and the research progress is analyzed using the following aspects: energy management, network security, data transmission and management, model-based design, control technique, and system resource allocation. We focus on CPS resource optimization, and propose a system performance optimization model with resource constraints. In addition, some classic applications (e.g., integrating intelligent road with unmanned vehicle) are provided to show that the prospects of CPSs are promising. Furthermore, research challenges and suggestions for future work are outlined in brief.

• The Journal of Asian Finance, Economics and Business
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• v.7 no.1
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• pp.37-46
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• 2020

The paper examines the dynamic relationship of domestic credit and stock market liquidity on the economic growth of the Philippines from 1995 to 2018 applying the autoregressive distributed lag (ARDL) bounds testing approach to cointegration, together with Granger causality test based on vector error correction model (VECM). The ARDL model indicated a long-run relationship of domestic credit and stock market liquidity on GDP growth. When the GDP per capita is the dependent variable there is weak cointegration. Also, the Johansen cointegration test confirmed the existence of long-run relationship of domestic credit and stock market liquidity both on GDP growth and GDP per capita. The VECM concludes a long-run causality running from domestic credit and stock market liquidity to GDP growth. At levels, domestic credit has significant short-run causal relationship with GDP growth. As for stock market liquidity at first lag, has significant short-run causal relationship with GDP growth. With regards to VECM for GDP per capita, domestic credit and stock market liquidity indicates no significant dynamic adjustment to a new equilibrium if a disturbance occurs in the whole system. At levels, the results indicated the presence of short-run causality from stock market liquidity and GDP per capita. The CUSUMSQ plot complements the findings of the CUSUM plot that the estimated models for GDP growth and GDP per capita were stable.

• Tribology and Lubricants
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• v.20 no.2
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• pp.97-101
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• 2004

This paper reports the studies on the wear-corrosion behavior of Al-Mg alloy in various pH environments. In various pH of sea water, corrosion and wear-corrosion loss of Al-Mg alloy were investigated. Also, the polarization test of Al-Mg alloy using potentiostat/galvanostat was carried out. And the rubbed surface of Al-Mg alloy using scanning electron micrographs after wear-corrosion test was examined in various pH values of sea water. The main results are as following : The polarization resistance of Al-Mg alloy in pH 4 solution is higer than that in pH 6.7 solution, and the corrosion current density in pH 4 is controlled than in pH 6.7 solution. The wear-corrosion loss of Al-Mg alloy with lowering pH becomes sensitive. As the oxide product of Al-Mg alloy appears granular structure and exholiation phenomenon, wear-corrosion loss of Al-Mg alloy increases.

• Journal of the Korean Society for Heat Treatment
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• v.15 no.6
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• pp.255-259
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• 2002

Effect of martensite on the mechanical properties of austempered ductile cast iron was investigated after obtained the martensite by subzero treatment. Retained austenite was transformed to martensite by subzero treatment, and with decreasing subzero treatment temperature, volume fraction of martensite was increased. With increasing of the volume fraction of martensite, tensile strength was increased and elongation was decreased, ratio of increasing of strength and decreasing of elongation was higher in case of specimens with lot's of Cu contents. With increasing of the volume fraction of martensite, hardness slowly increased until only about 5% and it rapidly increased in a straight proportion when it is above 5%, while impact value was rapidly decreased until about 7% but it had a little change when it is above 7%.