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21.
Christine Di Massimo Paul A. Lant Aidan Saunders Gary A. Montague Ming T. Tham A. Julian Morris 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1992,53(3):265-277
The last decade has seen the development of a number of approaches for estimating those variables which are difficult to measure on-line in industrial process situations. Whilst a range of techniques is available, a common element is the use of process knowledge in the form of a system model. In the case of bioprocess systems, although a large range of models has been presented in the literature, their use in estimation schemes on an industrial scale has been limited. A number of reasons can be identified for their low level of utilisation. Of particular significance is the uncertainty which exists in quantifying system performance and the process-model mismatch which inevitably results. The level of ‘pre-defined model’ uncertainty, together with the knowledge gained during the course of the fermentation, serves to dictate estimator structure. The paper considers a range of estimation strategies and contrasts, through industrial applications, their performance characteristics and utility. 相似文献
22.
Judge Timothy A.; Jackson Christine L.; Shaw John C.; Scott Brent A.; Rich Bruce L. 《Canadian Metallurgical Quarterly》2007,92(1):107
The present study estimated the unique contribution of self-efficacy to work-related performance controlling for personality (the Big 5 traits), intelligence or general mental ability, and job or task experience. Results, based on a meta-analysis of the relevant literatures, revealed that overall, across all studies and moderator conditions, the contribution of self-efficacy relative to purportedly more distal variables is relatively small. Within moderator categories, there were several cases in which self-efficacy made unique contributions to work-related performance. For example, self-efficacy predicted performance in jobs or tasks of low complexity but not those of medium or high complexity, and self-efficacy predicted performance for task but not job performance. Overall, results suggest that the predictive validity of self-efficacy is attenuated in the presence of individual differences, though this attenuation does depend on the context. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
23.
Eric C. Biemiller
Stephen Fyfitch
Christine A. Campbell 《International Journal of Pressure Vessels and Piping》1994,60(3):259-269The Yankee Atomic Electric Company test irradiation program was implemented to characterize the irradiation response of representative Yankee Rowe reactor vessel beltline plate materials and to remove uncertainties in the analysis of existing irradiation data on the Yankee Rowe reactor vessel steel. Plate materials each containing 0·24 w/o copper, but different nickel contents at 0·63 w/o and 0·19 w/o, were heat treated to simulate the Yankee vessel heat treatment (austenitized at 982°C (1800°F)) and to simulate Regulatory Guide 1·99 database materials (austenitized at 871°C (1600°F)). These heat treatments produced different microstructures so the effect of microstructure on irradiation damage sensitivity could be tested. Because the nickel content of the test plates varied and the copper level was constant, the effect of nickel on irradiation embrittlement was also tested. Correlation monitor material, HSST-02, was included in the program to benchmark the Ford Nuclear Reactor (University of Michigan Test Reactor) which had never been used before for this type of irradiation program. Materials taken from plate surface locations (versus 1/4T) were included to test whether or not the improved toughness properties of the plate surface layer, resulting from the rapid quench, are maintained after irradiation. If the improved properties are maintained, pressurized thermal shock calculations could utilize this margin. Finally, for one experiment, irradiations were conducted at two irradiation temperatures (260°C and 288°C) to determine the effect of irradiation temperature on embrittlement. The preliminary results of the irradiation program show an average temperature effect of 38°C for a 28°C difference in irradiation temperature. The results suggest that for nickel bearing steels, the superior toughness of plate surface material is maintained after irradiation and for the copper content tested, nickel has little effect on irradiation response. No apparent microstructure effect on irradiation response was noted and the HSST-02 material's response to irradiation was similar to results from power reactor and other test reactor tests, thus qualifying the Ford Test Reactor for irradiation experiments such as those conducted for the Yankee Atomic program. 相似文献
24.
W. Klas U. Herpers M. Reich R. Michel R. Droste R. Holm E.-M. Horn G. Müller 《工业材料与腐蚀》1991,42(11):570-575
The radiotracer technique as a means to investigate the corrosion of zirconium, tantalum, and a Ta-40Nb alloy in fluoride containing azeotropic nitric acid Zirconium and tantalum as well as the tantalum 40% niobium alloy are of considerable technical importance due to their high corrosion resistance against numerous corrosive media. With respect to corrosion testing in analytically pure azeotropic nitric acid in the temperature range between 20 and 121°C, corrosion rates were determined for zirconium: 7 · 10?6 to 5 · 10?4 mm/y, for tantalum: 10?8 to 4 · 10?6 mm/y, and for the Ta-40Nb alloy: 2 · 10?7 to 8 · 10?6 mm/y [1]. These corrosion rates will be markedly increased by adding small amounts of fluorides or by fluoride impurities. The radiotracer method after neutron activation was applied to determine the corrosion rates in azeotropic fluoride containing nitric acid. Even minute additions of fluorides strongly affect the corrosion resistance of zirconium. In the range between 0.15 and 10 ppm F? and at a temperature of 108°C, corrosion rates between 5.3 · 10?3 and 3.1 mm/y were measured. It was impossible to establish a limit for the fluoride concentration, below which the corrosion rate of zirconium will not be adversely influenced. The corrosion rates of tantalum and the Ta-40Nb alloy are considerably increasing above a fluoride concentration of 10 ppm. The highest corrosion rates measured were between 8.4 · 10?3 mm/y at 50°C/280 ppm F? and 1.4 · 10?2 mm/y at 110°C/320 ppm F?. Within the range of this investigation, the corrosion resistance of tantalum was higher than that of the Ta-40Nb alloy by one order of magnitude. The corrosion resistance of zirconium and tantalum was not influenced by any treatment of the samples before testing. 相似文献
25.
Christine Bernardi Frédéric Hecht 《Computer Methods in Applied Mechanics and Engineering》2007,196(8):1554-1573
Darcy’s equations model the flow of a viscous incompressible fluid in a rigid porous medium. One of the parameters of the system depends on the permeability of the medium and, when this medium is not homogeneous, the variations of the parameter could be very high. To handle this phenomenon, we propose a discretization of the model that relies on the mortar finite element method. Indeed, the idea is to construct a decomposition of the domain such that the permeability is constant on each element of the partition and to use independent meshes on the different subdomains. We perform the a priori and a posteriori analysis of this discretization and present some numerical experiments which are in good coherency with the results of the analysis. 相似文献
26.
27.
A. J. Seebregts L. W. M. M. Rademakers B. A. van den Horn 《Microelectronics Reliability》1995,35(9-10)
Wind turbines are being designed in accordance with deterministic design rules. As wind turbines increase in size and power, these rules may not be adequate to ascertain a safe and well balanced design. Wind turbine industry can take advantage of the safety and reliability practices in e.g. aerospace, nuclear and offshore industry. These practices include System Reliability (such as FMECA, Event Sequence Analysis and Fault Tree Analysis) and Structural Reliability methods. The approach to introduce Probabilistic Safety Assessment (PSA) which incorporates these reliability methods into wind turbine engineering will be described. By means of two recent case studies, the applicability, benefits, and limitations of these methods will be illustrated. 相似文献
28.
M Steinhardt HH Thielscher T von Horn R von Horn K Ermgassen D Smidt 《Canadian Metallurgical Quarterly》1996,103(4):136-141
Dairy calves and their dams from the dairy herd of the institute were used for this investigation. Calvings were watch carefully and jugular venous blood samples taken immediately after delivery from the cow and the calf and in the calf at 24 hours and at 48 hours of postnatal age as well were analyzed for T4, FT4, T3 and FT3 by luminescence enzyme immunoassay (LEIA). Higher thyroid values in calves than in their dams could be found increasing short after birth and reaching their highest level within 24 hours of postnatal life. The individual thyroid hormone values at birth and at 24 hours and at 48 hours of age are well correlated meaning the changes during the first days are specific for each calf. Strong correlation between the thyroid hormone values of the cows and those of the calves could be found. Mean values of thyroid hormones were significantly higher in female than in male calves all time but not different in the dams of these calves. 相似文献
29.
U. Lembke K. Grosse R. Pascova I. Gutzow O. Becker L. Horn 《Journal of Materials Science》1996,31(16):4333-4346
The kinetics of silver chloride cluster formation in a sodium borate glass heat treated isothermally at different temperatures above the glass transition temperature has been studied with small-angle X-ray scattering (SAXS). It is established that the size distributions of particle number and particle volume have bimodal shapes, i.e. the system of AgCl droplets consists of two populations with significantly different mean radii. The bimodality of the size distribution functions is confirmed by results of transmission electron microscopy (TEM) even if different techniques of sample preparation are used. The resolution limits of the TEM techniques applied amount to 2 nm and are comparable with the smallest particle diameters detectable by the SAXS method. The evolution of the size distributions is discussed in the framework of the theories of nucleation, growth and Ostwald ripening. 相似文献
30.
Christine Hine 《Journal of Computer-Mediated Communication》2007,12(2):618-634
E-science comprises diverse sites, connected in complex and heterogeneous ways. While ethnography is well established as a way of exploring the detail of the knowledge production process, some strategic adaptations are prompted by this spatial complexity of e-science. This article describes a study that focused on the biological discipline of systematics, exploring the ways in which use of a variety of information and communication technologies has become a routine part of disciplinary practice. The ethnography combined observation and interviews within systematics institutions with mailing list participation, exploration of web landscapes, and analysis of expectations around information and communications technologies as portrayed in policy documents. Exploring connections among these different activities offers a means of understanding multiple dimensions of e-science as a focus of practice and policy. It is important when studying e-science to engage critically with claims about the transformative capacity of new technologies and to adopt methodologies that remain agnostic in the face of such claims: A connective approach to ethnography offers considerable promise in this regard. 相似文献