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51.
52.
《Journal of the European Ceramic Society》2005,25(9):1629-1636
Ultimate tensile strength of five different continuous fiber-reinforced ceramic matrix composites (CMCs), including SiCf/BSAS (two dimensional (2D), 2 types), SiCf/MAS (2D), SiCf/SiC (2D), and Cf/SiC (2D, 2 types), was determined as a function of test rate at 1100–1200 °C in air. All five CMCs exhibited a significant dependency of ultimate tensile strength on test rate such that the ultimate tensile strength decreased with decreasing test rate. The dependency of ultimate tensile strength on test rate, the applicability of preload technique, and the predictability of life from one loading configuration (constant stress-rate loading) to another (constant stress loading) all suggested that the overall, phenomenological delayed failure of the CMCs would be governed by a power-law type of slow crack growth. 相似文献
53.
Repetitive processes are a distinct class of 2D systems (i.e. information propagation in two independent directions) of both systems theoretic and applications interest. They cannot be controlled by direct extension of existing techniques from either standard (termed 1D here) or 2D systems theory. In this paper, we exploit their unique physical structure to show how two term, i.e. proportional plus integral (or PI) action, can be used to control these processes to produce desired behavior (as opposed to just stability). 相似文献
54.
55.
《Energy Policy》2005,33(2):133-150
In order to forecast the technological development and cost of wind turbines and the production costs of wind electricity, frequent use is made of the so-called experience curve concept. Experience curves of wind turbines are generally based on data describing the development of national markets, which cause a number of problems when applied for global assessments. To analyze global wind energy price development more adequately, we compose a global experience curve. First, underlying factors for past and potential future price reductions of wind turbines are analyzed. Also possible implications and pitfalls when applying the experience curve methodology are assessed. Second, we present and discuss a new approach of establishing a global experience curve and thus a global progress ratio for the investment cost of wind farms. Results show that global progress ratios for wind farms may lie between 77% and 85% (with an average of 81%), which is significantly more optimistic than progress ratios applied in most current scenario studies and integrated assessment models. While the findings are based on a limited amount of data, they may indicate faster price reduction opportunities than so far assumed. With this global experience curve we aim to improve the reliability of describing the speed with which global costs of wind power may decline. 相似文献
56.
《International Journal of Hydrogen Energy》2005,30(10):1053-1062
Photocatalytic activity of mesoporous titania supported nickel oxide photocatalyst synthesized by single-step sol–gel (SSSG) process combined with surfactant-assisted template method was investigated for hydrogen evolution from an aqueous methanol solution, in comparison with one prepared by conventional incipient wetness impregnation (IWI) method. In single-step sol–gel process, nickel precursor was introduced into the titania sol prepared with the aid of a surfactant template behaving as pore-controlling agent to attain meso-scaled pore. The single-step sol–gel photocatalyst was experimentally found to enhance the photocatalytic evolution of hydrogen rather than the impregnated one. The optimum level of nickel loading in photocatalytic activity test for single-step sol–gel method was slightly higher than that for incipient wetness impregnation method. Characterization results demonstrated the significant modification of physical characteristics of the single-step sol–gel photocatalyst, anticipated to relating to the observation of higher photocatalytic hydrogen evolution activity. 相似文献
57.
《International Journal of Heat and Mass Transfer》2007,50(15-16):3250-3263
58.
《Expert systems with applications》2007,32(2):560-570
With today’s keen competition, semiconductor market has changed from producer-oriented to customer-oriented. To be successful, companies need to consider both customer satisfaction in demand and the ultimate profit goal of companies. Semiconductor fabricators today must face an environment with multi-product types and multi-priority orders. Since semiconductor fabrication has a very complicated production process, the production planning of different products types and priority levels is an even more difficult task to experts. The objective of this study is to construct an analytical approach under a fuzzy subjective judgment environment, in which fuzzy analytic hierarchy process (AHP) method with entropy weight is utilized to deal with uncertainty, to generate performance ranking of different priority mixes. The results provide guidance to experts in a fab regarding strategies for accepting orders with the consideration of manufacturing efficiency in the aspects of product, equipment efficiency and finance. 相似文献
59.
《Food Control》2007,18(10):1322-1327
Through a mechanism called quorum sensing, bacteria are able to express specific genes in response to population density. Cell-to-cell communication in bacteria is mediated by signal molecules such as acylated homoserine lactones (AHLs). This work aimed to detect AHL production in Gram-negative psychrotrophic bacteria isolated from raw milk. A total of 84.9% of the bacteria were identified as AHL producers eliciting a diversity of responses in the AHL-monitor systems. These results demonstrate that AHL-production is common among psychrotrophic bacteria isolated from milk, and indicate that quorum sensing may play an important role in the spoilage of this product. 相似文献
60.
《Journal of power sources》2006,162(2):943-948
This paper describes a novel method of modelling an energy store used to match the power output from a wind turbine and a solar PV array to a varying electrical load. The model estimates the fraction of time that an energy store spends full or empty. It can also estimate the power curtailed when the store is full and the unsatisfied demand when the store is empty. The new modelling method has been validated against time–stepping methods and shows generally good agreement over a wide range of store power ratings, store efficiencies, wind turbine capacities and solar PV capacities.Example results are presented for a system with 1 MW of wind power capacity, 2 MW of photovoltaic capacity, an energy store of 75% efficiency and a range of loads from 0 to 3 MW average. 相似文献