共查询到20条相似文献,搜索用时 15 毫秒
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The theoretical and experimental design strategies of chiral polyurethanes with good second harmonic generation efficiencies are discussed. The noncentrosymmetry of the polymers was broken by means of chiral and chemical poling. Different varieties of main chain chiral polymers are obtained by varying the composition of chiral and amido diol monomers using DBTDL catalyst. The designed chiral polymer architecture gives rise to high molecular weight polymers by the polyaddition polymerization with good thermal stability, linear and nonlinear optical activity. The polymer with isomannide as chiral moiety and CED (obtained by the aminolysis of ε-Caprolactone with 1, 2 diamino ethane) as amido diol monomer is found to possess high second harmonic generation efficiency. Both theoretical and experimental studies based on second order nonlinearity indicated that the designed chiral polyurethanes are useful for various nonlinear optical applications. 相似文献
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The theory of the potentiostatic current transient for three-dimensional multiple nucleation with diffusion controlled growth is discussed. Reliable values of nuclear number densities and nucleation rates are obtained from the analysis of the current maximum, and good agreement is obtained with experimental data for nucleation in several electrochemical systems. The termination of the nucleation process by the expansion of diffusion fields is considered, as well as the deviations from randomness observed in the distribution of nuclei on the electrode surface. 相似文献
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为了更好地研究发射药的点火性能,在基于密闭爆发器原理的点火性能测试装置基础上增加了一个延迟点火部件,构建了一个新型点火性能模拟试验装置,根据该装置建立了简单的火药分层点火过程模型,模拟并对比了高能太根-18/1、双芳-3-18/1及NR11-18/1三种发射药的点火性能。结果表明,NR11-18/1发射药较易点火,双芳-3-18/1发射药最难点火,点火时间分别为19和45ms。增加延迟点火部件后,可将点火药的燃烧和发射药的燃烧阶段有效区分,不仅有利于对比点火性能差异较小的发射药之间的区别,还有助于分析发射药低压段的燃烧速度。随着延迟点火部件长度的增加,点火时间也增长。 相似文献
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H A Scheraga 《Chemical reviews》1971,71(2):195-217
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A study of the air flow characteristics is reported for a vortex chamber 122 cm in diameter consisting of an upper cylindrical section 61 cm high and of a lower conical section 108 cm high. Measurements were made with a five-channel pressure probe of the radial profiles of tangential and axial velocities, with varying inlet air velocity and axial distance from the top of the chamber. Measurements of the static pressure profiles were made simultaneously. Finally, the angle of flow of the air entering through the single tangential inlet could be adjusted, and its effects on the flow recorded. From these results and from a theoretical analysis, generalized expressions for the tangential velocity profiles were obtained for the two regions of flow, forced-vortex and quasi-free vortex, which prevail in a confined vortex chamber, as a function of the entrance air velocity and of the radius at the point considered only. The angle of entering air was found to have no effect on the tangential velocity and only a minor effect on the static pressure distribution. The outlet diameter of the chamber was found to have a large effect on the profile of the axial velocities, reflecting the influence of the chamber static pressure on the later. 相似文献
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A study of the air flow characteristics is reported for a vortex chamber 122 cm in diameter consisting of an upper cylindrical section 61 cm high and of a lower conical section 108 cm high. Measurements were made with a five-channel pressure probe of the radial profiles of tangential and axial velocities, with varying inlet air velocity and axial distance from the top of the chamber. Measurements of the static pressure profiles were made simultaneously. Finally, the angle of flow of the air entering through the single tangential inlet could be adjusted, and its effects on the flow recorded. From these results and from a theoretical analysis, generalized expressions for the tangential velocity profiles were obtained for the two regions of flow, forced-vortex and quasi-free vortex, which prevail in a confined vortex chamber, as a function of the entrance air velocity and of the radius at the point considered only. The angle of entering air was found to have no effect on the tangential velocity and only a minor effect on the static pressure distribution. The outlet diameter of the chamber was found to have a large effect on the profile of the axial velocities, reflecting the influence of the chamber static pressure on the latter. 相似文献
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R.F.T Stepto 《Polymer》1979,20(11):1324-1326
A survey of recent work on pre-gel intramolecular reaction and gelation in oxypropylene-triol and tetrol-based polyester and polyurethane network-forming systems is presented, and relationships between the properties of the networks formed at complete reaction and the product of extents of reaction at gelation (αc) are discussed. In contrast to that in corresponding linear reaction systems, the amount of pre-gel intramolecular reaction in the triol-based polyurethanes is never negligible, even in bulk. Kilb's model of RA2 + RBf type gelling systems has been reanalysed and a more accurate condition for gelation evaluated. The shear moduli and Tgs of dry networks are found to increase as αc increases, indicating that these properties are strongly dependent on the amount of pre-gel loop formation. Extrapolated values of the shear moduli indicate that perfect, affine rather than phantom networks would be formed by reaction systems having the ideal gel point [αc = (f ? 1)?1]. 相似文献
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模块装药点传火过程的数值模拟 总被引:5,自引:0,他引:5
在各种点传火方案试验研究工作的基础上,建立了一维两相流数学物理模型,采用MacCormack差分格式和龙格-库塔法模拟刚性组合装药点火过程,数值模拟结果与试验结果进行了对比分析。 相似文献
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SF-3发射药的等离子体点火中止燃烧试验 总被引:3,自引:3,他引:0
采用有剪切膜片控压的密闭爆发器分别在等离子体点火和常规点火条件下进行该发射药的燃烧性能和中止燃烧两种比较试验.用扫描电镜观测了SF-3发射药的燃面变化情况.结果显示,在底喷式等离子体发生器作用下,SF-3发射药的燃烧表面存在大量微坑,使燃烧表面积大大增加,并导致SF-3发射药等离子体点火燃烧在一定程度上偏离几何燃烧规律.在常规点火条件下,SF-3发射药中止燃烧表面的Cu、C、O三种元素的归一化质量分数分别为0.7%、30.0%、69.3%,而在等离子体点火条件下则分别为3.0%、35.5%、61.5%,表明等离子体发生器所产生的高温C颗粒和Cu颗粒对SF-3发射药的燃烧有显著影响. 相似文献