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71.
72.
We study non-linear behaviour in a model chemical reaction scheme (proposed by Sal?nikov), in which a single chemical species undergoes a two-stage, first-order decay process. The second stage is exothermic and has a temperature-dependent rate, and as a result, spontaneous oscillations in the temperature and the concentration of an intermediate chemical are known to be possible. An additional oscillation is imposed on the system by varying the ambient temperature in a sinusoidal manner. Primary resonance occurs when the forcing frequency coincides with the frequency of the natural oscillations in this scheme and an infinite sequence of super-and subharmonic resonances is also present. Chaos is possible for appropriate parameter values and may result either from the Feigenbaum period-doubling cascade, or else as a result of the Ruelle-Takens approach through quasi-periodicity. 相似文献
73.
The current study examined psychological and physical health outcomes of the written disclosure paradigm and the hypothesis that the principles of therapeutic exposure account for the beneficial effects of the paradigm. Participants were randomly assigned to either a written disclosure condition or a control condition. Reactivity to the writing sessions was examined using both subjective and physiological measures. Measures of psychological and physical health were completed before and 1 month after the sessions. Participants assigned to the disclosure condition reported fewer psychological and physical symptoms at follow-up compared with control participants, though reductions were clinically significant for only 1 outcome measure. Physiological activation to the 1st disclosure session was associated with reduced psychological symptoms at follow-up for disclosure participants. Subjective reports of emotional responding corresponded with physiological reactivity. Implications of these findings are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
74.
Brian McKenna 《Computer Fraud & Security》2004,2004(7):3
Public Key Infrastructure is staging a comeback, according to new research from European IT user association EEMA. 相似文献
75.
Brian Dipert 《电子设计技术》2003,10(8):52-62
DRAM供应商希望有朝一日一种产品大小规格能适应所有的应用要求,但各种各样的设备要求则与之相差甚远.DRAM用户也许更喜欢定制的芯片,但价格会格外昂贵.双方会在保持原则的同时作出足够的让步以达成顺利的交易么? 相似文献
76.
77.
Melamed Barbara G.; Matthews Karen A.; Routh Donald K.; Stabler Brian 《Canadian Metallurgical Quarterly》1986,5(3):181
This article introduces the current issue of Health Psychology. The call for early intervention to prevent adulthood health problems and the need to consider each period of children's lives within its developmental perspective are the main emphases in this special issue of the journal. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
78.
Effect of Dilution and Porosity on Self-Propagating High-Temperature Synthesis of Silicon Nitride 总被引:3,自引:0,他引:3
Irene G. Cano Inna P. Borovinskaya Miguel A. Rodriguez Vladimir V. Grachev 《Journal of the American Ceramic Society》2002,85(9):2209-2211
Self-propagating high-temperature synthesis is a very easy and low-cost method to synthesize Si3 N4 . The nitriding of silicon powder takes place in a self-sustained regime under high pressures of nitrogen with dilution of silicon by Si3 N4 . In this work effects of dilution and green-mixture porosity on combustion velocity and phase content of reaction products are studied. Results are compared with previous work of other authors and different behaviors are found. An explanation of these behaviors is given. 相似文献
79.
Vinh Q. Nguyen Jas S. Sanghera Brian Cole Pablo Pureza Frederic H. Kung Ishwar D. Aggarwal 《Journal of the American Ceramic Society》2002,85(8):2056-2058
Arsenic sulfide glass optical fibers typically possess extrinsic absorption bands in the infrared wavelength region associated with residual hydrogen and oxygen related impurities, despite using purified precursors. We report a purification process based on the addition of tellurium tetrachloride (TeCl4 ) to the glass. During melting, the chlorine from TeCl4 reacts with the hydrogen impurities to produce volatile products (e.g., HCl) that can be removed by subsequent dynamic distillation. The processing conditions have been modified accordingly to produce optical fibers with significantly reduced loss due to hydrogen sulfide impurity content (1.5 dB/m). 相似文献
80.
Mold-slag friction and fracture may cause heat-transfer variations in continuous casting, which leads to steel shell temperature
and stress variations, resulting in surface cracks. Analytical transient models of liquid slag flow and solid slag stress
have been coupled with a finite-difference model of heat transfer in the mold, gap, and steel shell to predict transient shear
stress, friction, slip, and fracture of the slag layers. The models are validated by comparing with numerical models and plant
measurements of mold friction. Using reported slag-fracture strength and time-temperature-transformation (TTT) diagrams, the
models are applied to study the effect of casting speed and mold-powder viscosity properties on slag-layer behavior between
the oscillating mold wall and the solidifying steel shell. The study finds that liquid-slag lubrication would produce negligible
stresses. A lower mold-slag consumption rate leads to high solid friction and results in solid-slag-layer fracture and movement
below a critical value. Crystalline slag tends to fracture near the meniscus and glassy slag tends to fracture near the mold
exit. A medium casting speed may be the safest to avoid slag fracture, due to its having the lowest critical lubrication consumption
rate. The high measured friction force in operating casters could be due to three sources: an intermittent moving solid slag
layer, excessive mold taper, or mold misalignment.
Other symbols are defined in Table I 相似文献