• 한국수소및신에너지학회논문집
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• 제21권6호
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• pp.533-539
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• 2010

Ni-YSZ supported button cells were prepared by spray-coating YSZ and screen-printing YSZ-LSM powder as an electrolyte and oxygen electrode on Ni-YSZ cermet disks. In order to identify the polarization loss mechanism in high temperature electrolysis current-voltage characteristics coupled with electrochemical impedance spectroscopy were investigated as a function of temperature, current load, and the humidity. The effects of the different current collectors of platinum and silver for oxygen electrodes were compared. With Ag current collector two polarization losses were distinguished. The high frequency component was attributed to the Ni-YSZ cermet which was less susceptible to temperature variation but increasing in loss with humidity. The lower frequency component was attributed to the LSM electrode. Platinum current collector led to a much lower polarization loss.

• 한국통신학회논문지
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• 제30권9A호
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• pp.788-794
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• 2005

In this paper, we focus on the potential of dual polarized antennas in mobile system. thus, this paper designs exact dual polarized channel with Spatial Channel Model (SCM) and investigates the performance for certain environment. Using proposed the channel model; we know estimates of the channel capacity as a function of cross polarization discrimination (XPD) and spatial fading correlation. It is important that the MIMO channel matrix consists of Kronecker product dividable spatial and polarized channel. Through the channel characteristics, we propose an algorithm for the adaptation of transmit antenna configuration to time varying propagation environments. The optimal active transmit antenna subset is determined with equal power allocated to the active transmit antennas, assuming no feedback information on types of the selected antennas. We first consider a heuristic decision strategy in which the optimal active transmit antenna subset and its system capacity are determined such that the transmission data rate is maximized among all possible types. This paper then proposes singular values decision procedure consisting of Kronecker product with spatial and polarize channel. This method of singular value decision, which the first channel environments is determined using singular values of spatial channel part which is made of environment parameters and distance between antennas. level of correlation. Then we will select antenna which have various polarization type. After spatial channel structure is decided, we contact polarization types which have considerable cases It is note that the proposed algorithms and analysis of dual polarized channel using SCM (Spatial Channel Model) optimize channel capacity and reduce the number of transmit antenna selection compare to heuristic method which has considerable 100 cases.

• 한국산학기술학회논문지
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• 제10권11호
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• pp.3137-3143
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• 2009

본 논문에서는 한팔 나선 안테나(single arm spiral antenna)의 편파(polarization) 및 빔 틸트(beam tilt) 특성에 대하여 분석하였다. 한팔 나선 안테나는 나선 둘레 길이(spiral circumference length)가 한 파장 길이 이상 길어지면, 안테나의 최대방사 빔 방향이 안테나로부터 수직인 축빔(axial beam)으로부터 틸트되는 특성을 가지고 있다. 이때 나선 안테나의 급전위치(내부, 외부)에 따라 원형편파 (RHCP, LHCP)가 변화 하며, 안테나의 길이 변화에 따른 빔 틸트시 원형편파 특성에 따라 최대 방사 빔 방향이 서로 상이한 방향으로 틸트 됨을 검증하였다. 이러한 한팔 나선 안테나의 전기적인 특징을 이용하여, 단일 안테나로 이중 편파를 갖는 빔 포밍, 다이버시티, 또는 MIMO어플리케이션에 대한 적용 가능성을 확인하였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권8호
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• pp.4006-4020
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• 2018

In recent years, one of the most remarkable 5G technologies is massive multiple-input and multiple-output (MIMO) system which increases spectral efficiency by deploying a large number of transmit-antennas (eg. tens or hundreds transmit-antennas) at base station (BS). However, conventional massive MIMO system using single-polarized (SP) transmit-antennas increases the size of the transmit-array proportionally as the number of transmit-antennas increases. Hence, size reduction of large-scale transmit-array is one of the major concerns of massive MIMO system. To reduce the size of the transmit-array at BS, dual-polarized (DP) transmit-antenna can be the solution to halve the size of the transmit-array since one collocated DP transmit-antenna deploys vertical and horizontal transmit-antennas compared to SP transmit-antennas. Moreover, proposed DP massive MIMO system increases the spectral efficiency by not only in the space domain but also in the polarization domain whereas the conventional SP massive MIMO system increases the spectral efficiency by space domain only. In this paper, the comparative performance of DP and SP massive MIMO systems is analyzed by space division multiple access (SDMA) and space-polarization division multiple access (SPDMA) respectively. To analyze the performance of DP and SP massive MIMO systems, DP and SP spatial channel models (SCMs) are proposed which consider depolarized propagation channels between transmitter and receiver. The simulation results show that the performance of proposed 32 transmitter (Tx) DP massive MIMO system improves the spectral efficiency by about 91% for a large number of user equipments (UEs) compare to 32Tx SP massive MIMO system for identical size of the transmit-array.

• 한국재료학회지
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• 제15권8호
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• pp.536-542
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• 2005

Recently European Council(EU) published the RoHS(restriction of the use of certain hazardous substances in electrical and electronic equipment) which is prohibit the use of Pb, Hg, Cd, $Cr^{+6}$, PBB or PBDE in the electrical and electronic equipments. So EU member States shall ensure that, from 1 July 2006, new electrical and electronic equipment put on the market does not contain 6 hazardous substances. The one of the most important in electronics manufacturing process is soldering. Soldering process use the chemical substances which are applied in fluxing and cleaning processes and it can generate the malfunction of electronics caused by corrosion in the fields conditions. Therefore this study researched on the polarization and Tafel properties of Sn40Pb and Sn3.0Ag0.5Cu(SAC) solder based on the electrochemical theory. We prepared SnPb specimens which was aged in $150^{\circ}C,\;180^{\circ}C$ for 15 minutes ana Sn3.0Ag0.5Cu specimens that was aged in $180^{\circ}C,\;220^{\circ}C$ for 10 minutes. Experimental polarization curves were measured in distilled ionized water and $3.5 wt\%$, 1 mole NaCl electrolyte of $40^{\circ}C$, pH 7.5. Ag/AgCl and graphite were utilized by reference and counter electrode, respectively. To observe the electrochemical reaction, polarization test was conducted from -250 mV to +250 mV. From the polarization curves that were composed of anodic and cathodic curves, we obtained Tafel slop, reversible electrode potential(Ecorr) and exchange current density(Icorr). In these results, corrosion rate for two specimen were compared Sn3.0Ag0.5Cu with SnPb solders

• 한국통신학회논문지
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• 제28권8A호
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• pp.598-606
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• 2003

본 논문에서는 비동기 WCDMA 시스템의 빠른 셀 탐색을 위해 제안된 극성변조(PCM. Polarization Code Modulation) 셀 탐색 기법의 성능을 분석하고자 한다. 극성변조 셀 탐색 기법은 비동기 WCDMA 시스템의 표준 셀 탐색 알고리즘의 셀 탐색 시간을 단축하고 또한 수신기의 복잡도를 줄일 수 있는 기법으로, 홀드 코드를 이용하여 생성된 새로운 그룹 코드를 정의하고 이를 WCDMA P-SCH에 극성 변조하여, 기존 WCDMA의 2단계에서 사용되던 S-SCH의 그룹 코드(RS code)를 대체한다. 따라서 WCDMA 표준에 정의된 2개의 동기 채널을 하나로 줄일 수 있기 때문에 기존 WCDMA 셀 탐색 알고리즘에 비해 기지국 신호의 이득을 얻을 수 있는 기법이다. 본 논문에서는 극성변조 셀 탐색 알고리즘의 성능을 평가하기 긴하여 수학적 모델을 정의하고, 이를 통해 셀 탐색 성공 확률과 평균 탐색 시간을 이론적으로 분석하였다. 그 결과 극성변조 셀 탐색 알고리즘은 WCDMA 표준 셀 탐색 알고리즘의 성능에 비해 수신기 복잡도 측면과 셀 탐색 시간 측면에서 장점을 가지는 것을 확인할 수 있었다.

• 대한한의학회지
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• 제40권2호
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• pp.51-62
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• 2019

Objectives: This study was designed to evaluate the macrophages polarization of traditional Korean medicine on cardiac pain about Geum-Gwe-Yo-Ryak's two prescriptions including Kwaruhaebaekbanha-tang (KHB) and Kwaruhaebaekpaekju-tang (KHP). Materials and methods: Flow cytometry analysis was used to measure the changes in the ratio of M1 type and M2 type macrophages. Protein expression of nuclear factor-like 2 (Nrf2), heme oxygenase-1 (HO-1), inducible nitric oxide synthase (iNOS), and cyclooxygenase-2 (COX-2) were measured by Western Blot, and ABCA1 and SR-B1 were detected by real time PCR (RT-PCR). Intracellular lipid accumulation was measured by Oil Red O staining (ORO staining). Results: KHB and KHP increase anti-oxidative activity related protein levels including Nrf2 and HO-1. Furthermore, KHB and KHP inhibit lipid accumulation on intracellular levels through induction of ATP binding receptor cassette subfamily A member 1 (ABCA1) and scavenging receptor class B member 1 (SR-B1), respectively. Finally, KHB and KHP also blocked pro-inflammatory mediators including tumor necrosis factor-alpha ($TNF{\alpha}$) and interleukin-6 (IL-6), iNOS and COX-2 expression. Conclusion: This study suggests that KHB and KHP potently regulate the M1/M2 macrophage polarization.

• 공업화학
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• 제22권6호
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• pp.703-710
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• 2011

분리막 모듈 내 스페이서는 용액의 원활한 흐름을 위한 공간 확보와 더불어 유체의 난류를 형성시키므로 농도분극화 현상을 감소시키고 막 표면에 축적되는 오염물을 용액 내로 혼합하여 높은 투과유속과 분리막 모듈을 장기간 운전하는데 도움을 준다. 본 연구에서는 분리막 모듈 내 원형, 십자형, 다이아몬드형 및 육각형 단면의 스페이서와 스페이서의 배열 각도, 용질 배제율 및 투과유속에 대한 농도 변화를 "COMSOL Multiphysics" 프로그램으로 수치 해석하여 최적화하였다. 4가지 형태의 스페이서 중에서 십자형 단면 스페이서를 포함한 모듈의 경우가 분리막 표면 농도를 가장 낮게 유지하였으며 스페이서의 배열 각도는 $30^{\circ}$가 효율적이었다. 스페이서가 없는 모듈 출구에서 분리막 표면의 농도는 입구보다 약 2.09배까지 증가하였으나 가장 효율적인 십자형 스페이서를 $30^{\circ}$로 배열할 경우 약 1.29배로서 최대 37% 낮았다. 또한 투과유속이 증가할수록 십자형 스페이서의 농도분극 감소효과는 급격히 증가하였다.

• 지구물리와물리탐사
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• 제24권4호
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• pp.164-170
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• 2021

주파수 및 시간영역 유도분극 탐사는 지하 매질의 분광 정보를 포함하고 있다. 분광 특성의 분석은 주로 주파수영역 유도분극 탐사에서 연구되어 왔으나, 근래에 시간영역 유도분극에서도 연구가 활발하게 이루어지고 있다. 이 연구에서는 반무한 균질 공간을 가정하고 측정된 2차 전위 및 전기비저항으로부터 Cole-Cole 변수를 추정하는 역산법을 개발하였다. 충전성, 완화시간 및 주파수 승수로 구성되는 Cole-Cole 변수들은 비독립적이기 때문에 통상적인 비선형 역산을 적용할 경우 느린 수렴속도, 적정 초기 모델 설정의 어려움, 지역 극소점, 발산 위험 등의 다양한 문제점이 발생한다. 이 연구에서는 격자 탐색법을 도입하여 참 모델에 근접한 초기 모델을 설정하는 효과적인 역산법을 개발하였다. 마지막으로 다양한 역산 실험을 통하여 개발된 역산법의 타당성을 검증하였다.

• Journal of Electrochemical Science and Technology
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• 제13권2호
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• pp.213-226
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• 2022

In the present study, the corrosion behavior of aluminum Al-7075 tempered (T-6 condition) alloy was evaluated by immersion testing and electrochemical testing in 1.75% and 3.5% NaCl environment at acidic, neutral and basic pH. The data obtained by both immersion tests and electrochemical corrosion tests (potentiodynamic polarization and electrochemical impedance spectroscopy tests) present that the corrosion rate of the alloy specimens is minimum for the pH=7 condition of the solution due to the formation of dense and well adherent thin protective oxide layer. Whereas the solutions with acidic and alkaline pH cause shift in the corrosion behavior of aluminum alloy to more active domains aggravated by the constant flux of acidic and alkaline ions (Cl^- and OH^-) in the media which anodically dissolve the Al matrix in comparison to precipitated intermetallic phases (cathodic in nature) formed due to T6 treatment. Consequently, the pitting behavior of the alloy, as observed by cyclic polarization tests, shifts to more active regions when pH of the solutions changes from neutral to alkaline environment due to localized dissolution of the matrix in alkaline environment that ingress by diffusion through the pores in the oxide film. Microscopic analysis also strengthens the results obtained by immersion corrosion testing and electrochemical corrosion testing as the study examines the corrosion behavior of this alloy under a systematic evaluation in marine environment.