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31.
Cubic boron nitride (c-BN) crystals were synthesized in conditions of high temperature and high pressure (HTHP) when different kinds of bonded water were respectively added into the system of h-BN–Mg. All bonded water used in this work could reduce the temperature of growing c-BN compared to that in the system of h-BN–Mg. The c-BN color could change from black to yellow when certain amounts of bonded water, such as NiSO4·6H2O and CuSO4·5H2O, Mg(OH)2, were added. However, c-BN color remained black no matter how much bonded water, such as NiCl2·6H2O, CuCl2·2H2O, and SnCl2·2H2O, was added. The bonded water can be classified into Chlorine-containing bonded water (Cl-BW) and Chlorine-free bonded water (ClF-BW) according to their different characters and effects on the synthesized c-BN color. 相似文献
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34.
矿井串联系统模糊可靠性理论的研究 总被引:1,自引:0,他引:1
矿井系统不仅具有随机性,而且同时也具有模糊性,在系统分析与设计过程中应同时考虑这两种不确定性因素的影响。文中提出了模糊故障、模糊功能、系统模糊运营状态和广义可靠度等概念,并在此基础上提出了求单元及串联系统的生产能力、营运费用、应急维修费用、修理时间和广义可靠度等指标的方法,建立了使系统平均生产能力最大的系统最优运营策略的数学模型。 相似文献
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36.
The frequency modulation response and tuning dynamics of a two-section DFB laser are determined by carrier and thermal modulation of the active layer refractive index. In response to a step change in the injection current for switching between channels in a wavelength division multiplexed system, the optical frequency changes rapidly due to the carrier effect, and then slowly drifts toward a steady state value due to the thermal effect. For wavelength switched applications with heterodyne detection, the drifting of the optical frequency broadens the spectrum of the IF signal and may impose a limit on the time that the signal remains within the IF passband (residency time). The IF spectral broadening and residency time are investigated theoretically and experimentally. Based upon a minimum mean square error fit between experimental and theoretical FM responses, the dependence of the spectral broadening and residency time on the bias condition of the laser and the optical frequency switching interval is characterized 相似文献
37.
The coal filter cake is a product of fine coal after floatation which has an ash content of 7-13%, water content of 30±2%, and a particle size of less than 1 mm. The ash content was measured by the intensity of the single backscattered gamma-ray, and its accuracy is mainly dependent on the energy of the gamma-ray. The 238Pu low energy photon source is selected in this work. The energy of its gamma-ray is 15 keV, which can result not only in the best sensitivity, but also in the lowest contribution to the environment radiation. The root mean square deviation of the ash measurement is±0.33% (±1σ). 相似文献
38.
This paper presents a novel process for the fabrication of pultruded polyurethane (PU) composites. The effects of the processing parameters on the mechanical properties (flexural strength and flexural modulus, etc.) and thermal properties (HDT) of the fibre reinforced PU composites by pultrusion have been studied. The processing parameters investigated include pulling rate (in-line speed), die temperature, filler type and content, and post-cure time and temperature. Results show that the composites possessed various optimum pulling rates at different die temperatures. On the basis of the DSC diagram, the swelling ratio, the mechanical properties and the thermal properties of composites, the optimum die temperature can be determined. It is found that the mechanical and thermal properties increase with filler content for various types of filler. The mechanical and thermal properties increase at a suitable post-cure temperature and time. Furthermore, the properties which decreased due to the degradation of composite materials for a long post-cure time will be discussed. 相似文献
39.
环境放射化学研究中几个问题的讨论 总被引:1,自引:0,他引:1
本文从辐射环境保护和公众辐射防护的角度,讨论了放射性核素在环境中的迁移行为,放射性核素与环境介质的相互作用和放射性核素在环境中的形态等涉及到环境放射化学研究方向的问题,并讨论了它们之间相互依存的关系。 相似文献
40.
Jian Ma 《Education, IEEE Transactions on》1996,39(3):388-393
Assessment is an important task in problem-based learning (PBL). It has a strong influence on students' approaches to learning and their outcomes. In order to provide an open and fair method of PBL assessment, a group decision support system (GDSS) has been developed. The system uses mathematical decision methods for collecting assessment criteria and their appropriate weights, and databases for storing students' details and data on the assessment criteria. It integrates databases with model bases in a cooperative decision-making environment and is implemented on a client-server platform using a relational database management system. The GDSS has been developed and used to improve the efficiency and quality of assessing students' PBL outcomes 相似文献