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5-8 GHz 대역 ASK 변조기 MMIC 설계 및 제작
장미숙,하영철,허혁,문태정,황성범,송정근,홍창희,Jang, Mi-Sook,Ha, Young-Chul,Hur, Hyuk,Moon, Tae-Jung,Hwang, Sung-Beam,Song, Chung-Kun,Hong, Chang-Hee 한국통신학회 2001 韓國通信學會論文誌 Vol.26 No.11
본 논문에서는 ITS 서비스를 위해 개발된 5.8 GHz대역 근거리 전용 무선 통신을 이용한 자동게이트통관시스템의 차량탑재장치(OBE) 구성요소 중 ASK 변조기를 설계 및 제작하였다. 제안된 ASK 변조기는 인접채널간섭을 줄이기 위하여 3 V 단일전압 드레인 제어 변조회로로 설계되었으며 0.7 - 3 V의 넓은 선형변조영역과 40 dB 이상의 On/off Ratio 특성을 얻었다. 회로의 Layout과 공정은 ETRI 0.5$\mu\textrm{m}$ MESFET Library를 사용하였고 칩 면적은 1.0mm $\times$ 1.0mmn로 제작하였다. In this paper, we have desired and implemented of ASK modulator MMIC operating at 5.8 GHz for OBE used in AGPS(Automatic Gate Passing System). The proposed ASK modulator MMIC was implemented to apply a single supply voltage of 3 V to the drain in order to decrease ACP(Adjacent Channel Power). As a result, it is exhibits a broad linear modulation range from 0.7 V to 3 V and an On/off characteristic over 40 dB. The layouts of ASK modulator MMICs was designed and fabricated by using ETRI 0.57m MESFET library The chip size was 1.0mm $\times$x1.0mm.
공공서비스의 이질성 정도에 따른 고객마족혀엉과정 차이에 관한 연구
김영구,김경환,하영철,Kim, Young-Ku,Kim, Kyoung-Hwan,Ha, Young-Chul 한국마케팅과학회 2001 마케팅과학연구 Vol.8 No.-
Many customer satisfaction studies have accepted the confimation/disconfirmation paradigm, but the findings as the antecedents of consumer satisfaction are mixed. So rather than asking whether or not there is a direct effect of a certain variable on satisfaction, it is necessary asking when does a certain variable have a direct effect on satisfaction. According to this result, we assume that the situation has a direct effect on satisfaction. So this study has investigated the moderating role of perceived heterogeneity as a unit of situation, in the process of customer satisfaction formation, especially on public service. We have found such thing as follows. 1) situation has an effect on customer satisfaction. 2) perceived heterogeneity of the customers, as a situation variable, lets the process of their satisfaction formation differ. 3) through these studies, the confirmation/disconfirmation paradigm are able to extend on public services.
이철구(Cheol-gu Lee),하영철(Young-chul Ha),허재영(Jae-young Her) 한국유체기계학회 2003 유체기계 연구개발 발표회 논문집 Vol.- No.-
This study was experimentally performed in order to estimate the errors due to the leakage of transmitter gaugelines in the orifice flow meter for natural gas. It would be a serious problem in safety if a large quantity of leak was occurred at the tubes or fittings like valve. But in most cases the safety problems might be rarely happened because the gas leak detectors could be operated in advance and the various kinds of inspection would be also fulfilled periodically. If the leakage was occurred continuously with an undetectable amount at the gaugelines for measuring the pressure or the differential pressure(DP), the amount of leakage might be an error or an unaccounted flow(UAF). In addition if the measuring value of pressure or DP were affected by the leakage, it might also be a measurement error. The experiments were performed to estimate the amount of leakage and to check the DP changes if it exited. First, through the measurement of the air pressure changes in the airtight container connected to a transmitter with gaugelines as the time passed, the amount of leakage causing from the fittings of gaugelines was roughly estimated.<br/> As changing the leak position of the gaugeline, the leak was intentionally made to break out. The variance of DP was checked as controlling the extent of leakage and compared to no leak conditions. Consequently, under the normal maintenance conditions, the result represented that the amount of leakage causing from the gaugelines was insignificant and also the DP changes on leakage conditions were too small to cause the errors of measurements.
김홍민(Hong-Min Kim),김광용(Kwang-Yong Kim),허재영(Jae-Young Her),하영철(Young-Chul Ha) 한국유체기계학회 2001 유체기계 연구개발 발표회 논문집 Vol.- No.-
In this study, commercial CFD code, i.e, CFX-4.3 is used to analyze the flow field and to calculate pressure differences in an orifice flowmeter. Four numerical schemes and five turbulence models are tested. Hybrid scheme and Reynolds stress model show the best performance. Chosen scheme and turbulence model are applied to predict pressure differences through the orifice for the diameter ratios, 0.3, 0.5, and 0.7. And, the results are compared with the experimental data. The results show that the calculation error is inversely proportional to the diameter ratio, and is proportional to the mass flow rate.
상류 불균일 유동에 의한 오리피스 유량계의 계량오차 예측을 위한 삼차원 유동해석
김홍민(Hong-Min Kim),김광용(Kwang-Yong Kim),허재영(Jae-Young Her),하영철(Young-Chul Ha) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.5
Three-dimensional pipe flows with elbows and tees are calculated to estimate the effect of upstream flow<br/> distortion on measuring accuracy of orifice flow meter. Axisymmetric flows through orifice are calculated<br/> first to evaluate the performances of various numerical schemes and turbulence models. In three-dimensional<br/> calculations of the flow in pipe system, it is evaluated how the pressure difference across the orifice is<br/> dependent on the length of upstream straight pipe in a branch. From the results, it is found that, regardless of<br/> flow rate, the effect of the length can be neglected for the lengths larger than thirty diameters although there<br/> still remain significant swirl at the orifice.
윤두선(Yoon Doo Sun),이용원(Lee Yong Won),윤준용(Yoon Joon Yong),허재영(Heo Jae Young),하영철(Ha Young Chul) 한국유체기계학회 2007 유체기계 연구개발 발표회 논문집 Vol.- No.-
In this study, the natural gas pipe network system model was compared between the commercial program, named SynerGEE and the new developed program which adopted the Stoner model and inertia multiplier. Approximately the real value of pipe diameter and length was applied to the pipe system. The pressure at each location was calculated by SynerGEE and the developed program to find out the error rates by comparing the numerical results and measured results. Throughout this study, results verified not only the utility of two programs but also the pipe system model established originally.