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김윤석,이선희,이영하 충남대학교 생물공학연구소 2007 생물공학연구지 Vol.13 No.-
Although conventional activated sludge process is the most widely used biological process for the treatment of domestic and industrial wastewater, this process generates a large amount of waste activated sludge (WAS) as the main by-product. The ultimate disposal of WAS is one of the major problems faced by wastewater treatment plants, accounting for 50 to 60% of the total operating costs of the plant. This problem is expected to increase with the expansion of population and industry and tightening of environmental regulations on sludge disposal, thus increased attention has been turned to look into potential technology for sludge reduction. One concept for decreasing sludge production involves the pretreatment of WAS by mechanical, thermal, chemical, ultrasonic, thermochemical and microbiological methods to disrupt microbial cells of WAS. Cell disruption by these pretreatments can accelerate the solubilization (hydrolysis) of WAS and reduce the particle size, which subsequently improves the anaerobic digestion. In addition, WAS solubilization units have been integrated into the conventional or advanced activated sludge process, in which the solubilized products are mineralized or used as an exogen organic carbon source for denitrification. This paper attempts to review some pretreatment techniques which are evaluated to be efficient and cost-effective for inducing cell lysis and solubilization of WAS.
김윤석 한국통신학회 2000 韓國通信學會論文誌 Vol.25 No.9
도래할 B-ISDN 환경하에서 중추적 역할을 할 ATM의 실현을 위해서는 다중매체의 통화유량을 최적하에 제어할 수 있는 방법이 제시되어야 한다. 그러나 다중매체 통화유량의 특성이 완전히 밝혀지지 못한 상태에서 ATM의 제어, 특히 최적한 폭주제어의 실현은 난제로 남아있다. 그러므로 본 논문에서는 다중매체 통화유량 모델을 시변비선형함수라 가정하고 이를 실시간 추정하기 위해 병렬로 연결된 3중의 신경망 모델을 제시하며 모의실험을 통해 시변비선형함수를 추정하여 ATM의 폭주제어에 이용될 수 있는 가능성을 보인다. In B-ISDN, to realize ATM, the optimum control method of multi-media traffic must be proposed. Because there is not the traffic model of multi-media to make clear, the realization of optimum ATM congestion control is very difficult. In this paper, the traffic model is assumed to be slowly time-variable non-linear function and for real-time prediction of it, new model which is composed with parallel triple neural networks is proposed. And the simulation to predict assumed ATM traffic is executed. From the result, it's capability is shown that the proposed neural network model can be used in ATM congestion control.
손실있는 실리콘 반도체위에 제작된 전송선로의 유한차분법을 이용한 해석
김윤석 한국통신학회 2000 韓國通信學會論文誌 Vol.25 No.9
MIS(도체-부도체-반도체) 구조로된 전송선로를 해석하기 위하여 기본적으로 특성임피던스와 전파상수의 추출에 기초한 일반적인 특성화 절차가 사용된다. 본논문에서는 Si와 Si02층 사이에 0전위를 가진 도체를 일정한 간격의 주기적인 배열로 고안된 새로운 모델의 MIS구조에 대한 유한차분법을 이용한 해석방법을 제안한다. 특히 전송선로에 대한 유전체의 영향을 줄이기 위하여 0전위를 가진 주기적인 결합의 도체로 이루어진 구조가 시간영역의 신호를 통해 시험된다. Quality factor 뿐만아니라 주파수 의존적인 추출된 전송선로 파라미터와 등가회로 파라미터가 주파수 및 0전위 도체 간격의 함수로서 나타내진다. 특히 전송선로의 Quality factor가 특성임피던스 및 유효유전 상수의 큰 변화없이 개선될수 있음을 볼 수 있다. Basically, a general characterization procedure based on the extraction of the characteristic impedance and propagation constant for analyzing a single MIS(Metal-Insulator-Semiconductor) transmission line is used. In this paper, an analysis for a new substrate shielding MIS structure consisting of grounded cross-bars at the interface between Si and SiO2 layer using the Finite-Difference Time-Domain (FDTD) method is presented. In order to reduce the substrate effects on the transmission line characteristics, a shielding structure consisting of grounded cross bar lines over time-domain signal has been examined. The extracted distributed frequency-dependent transmission line parameters and corresponding equivalent circuit parameters as well as quality factor have been examined as functions of cross-bar spacing and frequency. It is shown that the quality factor of the transmission line can be improved without significant change in the characteristic impedance and effectve dielectric constant.