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김기만,차일환,Kim, Gi-Man,Cha, Il-Hwan 한국음향학회 1996 韓國音響學會誌 Vol.15 No.6
실제 환경에서 배열은 비정상적으로 동작하는 소자를 가질 확률이 높다. 결함 소자는 출력이 없거나 정상인 것에 비해 크게 감소된 이득을 갖는다. 이는 빔의 부엽 레벨을 높이고, 적응 빔 형성기에서 간섭 신호를 제거하지 못하도록 한다. 이 논문에서는 결함 소자들을 갖는 배열을 위한 빔 형성 방법을 제안하였다. 이상적인 경우 배열 출력 자료들로부터 계산된 자기 상관 행렬은 Toeplitz 행렬이다. 그러나 결함 소자를 갖는 배열로부터 게산된 자기 상관 행렬은 결함 행렬이다. 따라서 이 행렬의 대각항들을 평균하여 얻어진 값들로 새로운 자기 상관 행렬을 구성하고, 새로 구성된 자기 상관 행렬을 빔형성 방법에 적용한다. 제안된 방법의 성능을 고찰하기 위해 컴퓨터 시뮬레이션을 수행하였다. 그 결과 제안된 방법은 기존의 부분 처리 기법의 단점이었던 자유도 문제를 해결할 수 있었다. An array often has faulty elements in real operation. The faulty elements, producing no output or highly reduced gain than other normal elements, cause an elevated sidelobe level and fail to reject the interference signals in an adaptive beamformer. In this paper we have presented the beamforming algorithm for arrays with faulty elements. In the ideal case, an autocorrelation matrix computed from array output data is the toeplitz. However, the inverse of the autocorrelation matrix computed from array with faulty elements can not be obtained due to deficient values of matrix. To overcome this problem, an adaptive beamforming algorithm using the average values of the diagonal terms of matrix is proposed. The computer simulations have been performed to study the performance of the presented method. We have been able to solve the degrees-of-freedom problem that is the drawback of the previous subaperture processing technique.
결함소자를 갖는 어레이를 위한 방향 탐지 기법에 관한 연구
김기만,윤대희,차일환,Kim, Ki-Man,Youn, Dae-Hee,Cha, Il-Whan 한국음향학회 1997 韓國音響學會誌 Vol.16 No.4
In this paper, some problems that occur from faulty elements in a direction finding system composed of the linear array are studied and the method which improves the performance is proposed. The fault element means the sensor that has no output or highly reduced gain than other normal sensors. In the case of the presence of faulty elements, the performance of the conventional the spatial spectrum subject to a constraint. The corrected spatial spectrum is obtained by this vector. The computer simulations have been performed to study the performance of the proposed method. We have compared the proposed method with the subaperture processing method of one of the previous works. 이 논문에서는 선형 어레이로 구성된 방향 탐지 시스템에서 결함 소자가 발생하였을 경우 발생되는 문제점들을 제시하고, 시스템의 성능을 개선하기 위한 방법을 제안하였다. 여기서 결함 소자란 센서의 출력이 없거나 정상적으로 동작하는 센서에 비해 그 이득이 크게 감쇄되어 미세한 출력을 얻는 현상을 의미한다. 결함 소자 발생시에 기존의 방향 탐지 방법들의 성능은 크게 저하된다. 제안된 방법에서는 제한 조건을 만족하면서 공간 스펙트럼 값을 최대화하는 방향으로 보정 벡터값을 구하며, 이 보정 벡터를 이용하여 개선된 성능을 갖는 공간 스펙트럼을 얻는다. 제안된 방법의 성능을 고찰하기위해 컴퓨터 시뮬레이션을 수행하였으며 기존의 결함 소자 문제 해결 방법중의 하나인 부분 처리 방법과 비교하였다.
SiC foam에 코팅된 상용 촉매에서의 집광된 태양열을 이용한 메탄 수증기개질 반응 연구
김기만,한귀영,서태범,강용혁,Kim, Ki-Man,Han, Gui-Young,Seo, Tae-Beom,Kang, Yong-Heack 한국태양에너지학회 2007 한국태양에너지학회 논문집 Vol.27 No.1
Steam reforming of methane using Xe-arc solar simulator was studied for the application of concentrated solar energy into chemical reaction. The reactor, a volumetric absorber, consisted of a porous ceramic foam disk coated with commercial reforming catalyst. Operating temperature was in the range of $450\;-\;550^{\circ}C$ and the excess steam ratio to methane was from 3.0 to 5.0. At the steady-state condition, the conversion of methane Increased with temperature in the range of 15 % - 30 % and the experimentally determined conversion was found to be close to theoretical equilibrium conversion. It was also found that the CO selectivity slightly decreased with excess steam ratio. Finally, the conversion of methane decreased significantly with space velocity of reactants.
Release Characteristics of Terbutaline Sulfate Sustained-Release Beads In Vitro
김기만,김영일,홍순억,Kim, Ki Man,Kim, Young Il,Hong, Soon Uk Korean College Of Clinical Pharmacy 1991 한국임상약학회지 Vol.1 No.1
The sustained-release beads containing terbutaline sulfate (TBS) were prepared by rotogranulation method. The drug was dusted on the non-pareil seeds in a CF-granulator. The sustained-release beads were obtained by coating the active beads with ethylcellulose or $Eudragits^{(R)}$, using in any case the same granulator employed for active beads preparation. The release characteristics of sustained-release beads were examined in vitro by rotating basket method applied to $Bricanyl^{(R)}$ durules which is a sustained-release TBS matrix tablet. The release of terbutaline from the beads in vitro was first-order, and the release rate was dependent on both the coat weight ratio and membrane hydrophilicity. Both surfaces of the beads before and after dissolution were smooth. The drug release pattern from the beads could be thought the diffusion through the polymer membrane. The release rate and the surface of the beads stored for 3 years at room temperature were the same with those of the initial beads.
김기만(K . M . Kim),김현수(H . S . Kim),김승인(S . I . Kim),김영일(Y . I . Kim) 한국약제학회 1987 Journal of Pharmaceutical Investigation Vol.17 No.4
Rifampicin sustained-release micropellets were prepared by spray congealing micropelleting technique using gelatin as the embedding matrix. The pellets were hardened by treating with formalin-isopropanol mixture. The in vitro release rates of rifampicin from the gelatin micropellets which were prepared with the different concentrations of formalin solution were determined in the following dissolution media for 8 hours; a) pH 1.2 buffer solution(USP XXI). b) distilled water. c) pH 7.4 buffer solution(USP XXI). d) pH 1.2 buffer solution for 1.5 hours and pH 7.4 for 6.5 hours thereafter. From the results of the dissolution study, following results were obtained; 1) It was observed that the rate of drug release from the prepared micropellts followed first-order release kinetics. 2) It was found that the change of the release rates was not dependent on the drug-gelatin ratio, but on the concentration of formalin and the time of hardening. 3) It could also be noticed that the increase in the release rates was more pronounced in pH 7.4 of dissolution medium rather than in pH 1.2. This fact might be attributed to the swelling property of gelatin in the dissolution medium.