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21.
This second article deals with using the Comsis software for a particular application. Simulation is used to determine the maximum channel density in presence of crosstalk. In a first part, the modelling of the system is described. The simulation parameters of different optical elements are given. The results show that in the case of channels modulated at 500 Mbitls using fsk modulation format, and a direct detection operation at 1,5 μm, a minimum spacing of 6 GHz can be obtained with a 2 dB penalty. Thus if only the bandwidth of the erbium doped fibre amplifier is taken into account, the maximum number of channels which can be used is 250. However if the fsr (free spectral range) of optical filter is taken into account, the maximun number of channels is limited to 30.  相似文献   
22.
This study addresses the removal of humic acid (HA) dissolved in an aqueous medium by a photoelectrocatalytic process. UV254 removal and the degradation of color (Vis400) followed pseudo‐first order kinetics. Rate constants were 1.1 × 10?1 min?1, 8.3 × 10?2 min?1 and 2.49 × 10?2 min?1 (R2 > 0.97) for UV254 degradation and 1.7 × 10?1 min?1, 6.5 × 10?2 min?1 and 2.0 × 10?2 min?1 for color removal from 5 mg dm?3, 10 mg dm?3 and 25 mg dm?3 HA respectively. Following a 2 h irradiation time, 96% of the color, 98% of the humic acid and 85% of the total organic carbon (TOC) was removed from an initial 25 mg dm?3 HA solution in the photoanode cell. Photocatalytic removal on the same photoanode was also studied in order to compare the two methods of degradation. Results showed that the photoelectrocatalytic method was much more effective than the photocatalytic method especially at high pH values and with respect to UV254 removal. The effect of other important reaction variables, eg pH, external potential and electrolyte concentration, on the photoelectrocatalytic HA degradation was also studied. Copyright © 2003 Society of Chemical Industry  相似文献   
23.
This paper introduces a new mathematical model of the master-slave architecture for distributed evolutionary computations (EC). This model is validated using a concrete implementation based on the Distributed BEAGLE C++ framework. Results show that contrary to (current) popular belief, master-slave architectures are able to scale well over local area networks of workstations using off-the-shelf networking equipment. The main properties of the master-slave are also compared with those of the more mainstream island-model.  相似文献   
24.
Conducted a reliability and validity study of the French version of E. L. Deci and R. M. Ryan's (1985) General Causality Orientations Scale (GCOS), which measures the extent to which people are oriented toward the autonomy, control, and impersonal aspects of the initiation and regulation of behavior. Findings support the psychometric and construct validity of the French version of the GCOS; suggestions for its use in French-Canadian psychological research are discussed. (English abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
25.
A family of energy/economic/environmental (E3) models is presented as a mechanism for analysing national policy issues. The family consists of discrete models which are designed to be run in an integrated manner. The outputs of certain models provide the inputs to the next. This structure allows the analyst to readily incorporate an understanding of regional factors such as local energy prices, concerns over air quality, water availability, or attitudes towards construction of new energy facilities, into national assessments of energy policies. This paper reviews the analytic framework within which energy policy issues are currently addressed. The initial family of E3 models is described with the emphasis on the data linkages and feedback which are provided when these models are run sequentially. The ongoing MITRE research programme with the E3 family of models is presented and plans and opportunities for future work are outlined.  相似文献   
26.
Thermodynamic analysis of solar photovoltaic cell systems   总被引:1,自引:0,他引:1  
The thermodynamic characteristics of solar photovoltaic (PV) cells are investigated from a perspective based on exergy. A new efficiency is developed that is useful in studying PV performance and possible improvements. Exergy analysis is applied to a PV system and its components, and exergy flows, losses and efficiencies are evaluated. Energy efficiency is seen to vary between 7% and 12% during the day. In contrast, exergy efficiencies, which incorporate the second law of thermodynamics and account for solar irradiation exergy values, are lower for electricity generation using the considered PV system, ranging from 2% to 8%. Values of “fill factors” are determined for the system and observed to be similar to values of exergy efficiency.  相似文献   
27.
Audiological tests were conducted on 34 patients before and after undergoing an operation in spinal anaesthesia. One of these patients developed a considerable unilateral hearing loss in the low-frequency range, which persisted until an epidural blood-patch was given. Unexpectedly, we also found a general small but significant threshold shift at 500 Hz, which has never before been described in the literature. The biological mechanism is discussed, and the results suggest that the explanation of the hearing loss could be a condition similar to endolymphatic hydrops, resulting from perilymphatic hypotension due to loss of liquor during and after the spinal anaesthesia.  相似文献   
28.
This paper describes how various characterisation methods can be used to investigate the physicochemical and spectral properties of gold films in contact with glass or ceramic. The interface between the metal and substrate has been given special attention. The examples chosen to illustrate this include: liquid gold films (decorated and fired) or inlayed gold layers on ceramic wares and “sandwich” gold foils between two glass sheets for mosaic application. Characterisation methods include: microanalytical scanning electron microscopy, X-ray diffraction, ion beam analyses (PIXE: particle induced X-ray emission; RBS: Rutherford back-scattering spectrometry), photo-spectrometry and colorimetry. The adhesion mechanism and colour behaviour of the coated objects is discussed.  相似文献   
29.
这个综合学校包括一个主建筑,一个体育馆和各种户外设施,朝向一片处在前军事基地上的住宅开发区。整个主建筑沿纵向被一个由顶部采光的回廊从中间分开,由此可以进入两侧的教室,回廊局部变宽的部分构成一个公共空间。这个构想与将城市设计理论运用于建筑内部设计的概念相符合:街道、广场和建筑被看成了建筑内部空间部分。虽然这个建筑从外部看来是个大体块,但内部空间却设计流畅,通道有的通向楼层的各个角落,也有的依着倾斜的地势因势而建。由墙面反射的散射光线加强了内部空间的肃穆和厚重感。在具有宗教感的整体风格下,整个学校的设计和装饰也显得古香古色,如一部宽阔的观光楼梯、两个塔形和壁炉形的建筑构成元素等。不同历史风格建筑的叠加给这个校区带来一种复杂的味道,堪比阿尔多·罗西(Aldo Rossi)的设计或泰辛(Tessin)新理性主义的代表作。  相似文献   
30.
Abstract. A sufficient condition for the invertibility of univariate periodic moving-average models has been given by Cipra and Ghysels and Hall. We show that this condition is not a necessary one, and provide a necessary and sufficient condition for the general m -variate, d -periodical moving-average MA( q ) case.  相似文献   
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