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SCAE와 SCAD를 이용한 광 CDMA시스템에서 간섭패턴 분석
강태구,최재경,박찬영,최영완,Kang, Tae-Gu,Choi, Jae-Kyong,Park, Chan-Young,Choi, Young-Wan 대한전자공학회 2000 電子工學會論文誌-SD (Semiconductor and devices) Vol.37 No.1
Series Coupler Access Encodler(SCAE)와 Series Coupler Access Decoder(SCAD)를 이용한 광CDMA(Code Division Multiple Access)시스템에서 광정합필터 특성을 삼차신호까지 고려하여 분석하였다. 기존의 연구에서는 SCAE 및 ACAD를 평가할 때, 일차신호만을 고려하여 시스템의 성능을 분석하여 성능평가가 정확하지가 않았다. SCAE 및 SCAD는 커플러 수를 증가함에 따라 여러 형태의 간섭신호들을 가지므로, 이러한 신호들이 자기상관과 상호상관 세기를 변화시킨다. 그러므로 좀 더 정확한 시스템 성능을 분석하기 위해서는 간섭신호들의 특성을 연구할 필요성이 있다. 본 논문에서는 복호화 되는 광신호를 삼차신호까지 수학적으로 해석하였고, 시스템의 자기상관과 상호상관에 미치는 영향을 모의실험을 통해 분석하였다. 커플러 수 증가에 따라 나타나는 삼차신호들이 간섭신호 형태가 되어 peak to side-lobe ratio를 감소키기는 요인으로 작용됨을 정량적으로 확인하였다. 간섭신호들의 크기는 ${\alpha}$(coupling coefficient)값이 커질수록 증가하였으며, 커플러 개수(N)=5, ${\alpha}$=0.5인 조건에서 삼차신호까지 고려한 peak to side-lobe ratio는 3.75 dB까지 열화됨을 밝혔다. 또한, 일차신호의 main-lobe세기에 의해 수신기의 임계레벨을 결정한다면, 삼차신호에 의해 증가된 side-lobes세기 때문에 SCAE와 SCAD를 이용한 광 CDMA system에 다중 접속할 수 있는 사용자 수가 제한됨을 알 수 있었다. We have analyzed optical matched filters considering the third order signals in the optical code division multiple access (CDMA) system based on optical series coupler access encoder (SCAE) and series coupler access decoder (SCAD). In previous studies, the performance evaluation of the optical CDMA system using SCAE and SCAD was not sufficiently accurate because they analyzed system performance only considering the first order signals. Since optical SCAE and SCAD intrinsically have high order signals of various patterns as the number of coupler increases, they change auto- and cross-correlation intensities. Thus, it is necessary to investigate properties of the third order signals so that we may analyze the exact performance of system. In this paper, we mathematically interpret the optical signals up to the third order, and analyzed the effects of th third order signals on auto- and cross-correlation intensities. In result, as ${\alpha}$(coupling coefficient) value increases, the intensity of the third order signals increases. It is found that the peak to side-lobe ratio considering the third order signals is degraded by 3.75 dB at N(coupler number)=5 and ${\alpha}$=0.5. Also if threshold value in receiver is set by main-lobe peak of the first order signals, it is found that the number of users in an optical CDMA system is limited because the intensity peak of side-lobes is raised by the third order signals.
가열 롤에서 플라즈마 TiO<sub>2</sub>-NiCr 용사피막의 특성
강태구,진민석,고영봉,김태형,조상흠,박정식,김종철,박경채,Kang, Tae-Gu,Jin, Min-Seok,Ko, Young-Bong,Kim, Tae-Hyung,Cho, Sang-Hum,Park, Jung-Sik,Kim, Jong-Chul,Park, Kyeung-Chae 대한용접접합학회 2007 대한용접·접합학회지 Vol.25 No.4
The heating unit of direct heating method manufactured as the plasma spray coating of $TiO_2/NiCr$ conductive heating material on the surface of heating unit in order to improve the disadvantages of indirect heating method. $TiO_2$ and NiCr (80wt.%Ni-20wt.%Cr) that had the properties of conduction and heating was chosen for the conductive heating material. The compositions of the composite powders were studied $TiO_2-30wt.%NiCr\;and\;TiO_2-10wt.%NiCr$. As the heating temperature was increased, the hardness of heating layer was increased because of the fine microstructure and the decrease of porosity. The adhesion strength was decreased for coarsening and connection of voids in the insulation layer, and the electrical resistivity of heating layer was increased for fine crack formation and growth. In this study, the best efficient sprayed coatings with heating unit was concluded as the plasma sprayed $TiO_2-10wt.%NiCr$ coatings that was heat treated at $300^{\circ}C$.
$TiO_2$ 및 Ag 스퍼터링-$TiO_2$ 플라즈마 용사피막의 광전류 및 광분해 특성
강태구,장용호,박경채,Kang, Tae-Gu,Jang, Yong-Ho,Park, Kyeung-Chae 대한용접접합학회 2009 대한용접·접합학회지 Vol.27 No.2
In this study, we investigated photocatalytic ability of plasma sprayed $TiO_2$ and Ag sputtering $TiO_2$(Ag-$TiO_2$) coatings. A sputtering processes were adopted to coat the surface of $TiO_2$ with Ag(99.99%). Ag was sputtered at 10mA, 450V for $1{\sim}11$ seconds. $TiO_2$ and Ag-$TiO_2$ coatings were heat-treated at 250, 300, 350, $400^{\circ}C$ for $0{\sim}240$seconds. Photoelectrical conductivity was measured by four-point probe, and photodegradation was calculated by UV-V is spectrometer. Microstructure observation of $TiO_2$ and Ag-$TiO_2$ coatings were investigated by SEM. Crystal structure of $TiO_2$ and Ag-$TiO_2$ coatings were investigated by XRD. Qualitative analyses of $TiO_2$ and Ag-$TiO_2$ coatings were conducted by EDX. When $TiO_2$ coatings were heat-treated at $350^{\circ}C$ for 30 sec, photoelectrical conductivity and photodegradation were best. And in XRD analysis result, (101)/(110) relative intensity ratio of $TiO_2$(rutile) was comparably changed with photoelectrical conductivity. When Ag-$TiO_2$ coatings were heat-treated at $350^{\circ}C$ for 30 [sec] after sputtering Ag for 7 sec, Photoelectrical conductivity and photodegradation are best. Surface of coatings in such condition has very small and uniform Ag particles.
무증상 경동맥협착에서 관찰되는 망막신경섬유층의 두께 감소
강태구(Tae Gu Kang),배희원(Heewon Bae),강민주(Min Ju Kang),최상경(Sangkyung Choi) 대한안과학회 2021 대한안과학회지 Vol.62 No.2
목적: 망막신경섬유층의 두께와 경동맥의 죽상경화성 협착과의 연관성에 대해 알아보고자 하였다. 대상과 방법: 빛간섭단층촬영을 이용한 망막신경섬유층의 측정 및 경동맥초음파검사를 1년 이내 시행한 106명을 대상으로 망막신경섬유층을 4분면으로 구분하여 각각의 두께 및 총 평균 두께와 경동맥의 내막두께, 플라크의 유무 및 협착 정도를 비교하였다. 또한, 망막신경섬유층의 총 두께와 경동맥의 죽상경화성 협착과의 상관관계를 확인하기 위해 나이, 총콜레스테롤 수치를 통제한 다중회귀분석(multiple regression analysis)을 실시하였다. 결과: 망막신경섬유층의 총 두께의 감소가 총경동맥플라크의 유무와 유의한 연관성을 보였으며(p=0.039), 총경동맥플라크 유무에 따른 두 군은 경동맥내막두께, 콜레스테롤 수치를 제외한 나이 및 혈관질환의 위험인자 간의 차이는 없었다. 선형회귀분석(linear univariate regression analysis)을 통하여 망막신경섬유층의 두께와 나이, 총 콜레스테롤 수치와의 관련성을 확인하였다. 또한, 다중회귀분석(linear multivariate regression analysis) 결과, 나이와 총 콜레스테롤 수치를 통제한 상황에서 총경동맥플라크의 유무와 망막신경섬유층 총 두께의 유의한 상관관계를 확인하였다(p=0.026). 결론: 빛간섭단층촬영을 이용한 망막신경섬유층의 측정을 통하여 안과적 질환을 배제한 망막신경섬유층의 두께 감소가 있을 경우 경동맥검사의 필요성을 고려해 볼 수 있다. Purpose: To investigate the relationship between retinal nerve fiber layer (RNFL) thickness and carotid artery stenosis (CAS). Methods: We retrospectively reviewed the medical records of 106 patients who underwent both optical coherence tomography to determine RNFL and carotid artery sonography within 1 year. The RNFL was divided into four quadrants, and each quadrant’s RNFL thickness and average thickness were compared with the artery endothelial thickness, the presence of plaque, and the degree of CAS. A multiple regression analysis was performed to assess the relationship between RNFL and CAS. Results: The presence of carotid artery plaque had a significant association with a decrease in the average RNFL thickness (p = 0.039). There was no statistically significant difference in age or risk factors associated with vascular disease, with the exception of carotid endothelial thickness and the total cholesterol level in the two groups, depending on the presence of total carotid plaque. RNFL thickness was confirmed to be related to age and total cholesterol levels using linear univariate regression analysis. In a multivariable linear regression analysis, with age and total cholesterol levels controlled, the presence of carotid artery plaque was significantly associated with a decrease in average RNFL thickness (p = 0.026). Conclusions: Asymptomatic CAS may be associated with a decrease in average RNFL thickness. In patients with decreased RNFL thickness without any ophthalmic diseases, carotid artery examination should be considered.
연구논문 : 공간모형을 이용한 수질오염물질의 공간적 예측 및 평가에 대한 연구
강태구 ( Tae Gu Kang ),이혁 ( Hynk Lee ),강일석 ( Il Seok Kang ),허태영 ( Tae Young Heo ) 한국물환경학회(구 한국수질보전학회) 2014 한국물환경학회지 Vol.30 No.4
Spatial prediction methods have been useful to determine the variability of water quality in space and time due to difficulties in collecting spatial data across extensive spaces such as watershed. This study compares two kriging methods in predicting BOD concentration on the unmonitored sites in the Geum River Watershed and to assess its predictive performance by leave-one-out cross validation. This study has shown that cokriging method can make better predictions of BOD concentration than ordinary kriging method across the Geum River Watershed. Challenges for the application of cokriging on the spatial prediction of surface water quality involve the comparison of network-distance-based relationship and euclidean-distance-based relationship for the improvement in the predictive performance.