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951.
Qi-Chang He 《Comptes Rendus Mecanique》2002,330(10):691-696
Using a physically-based constitutive law for imperfect interfaces, this work deals with the problem of embedding a three-dimensional elastic inclusion in a uniformly stressed elastic matrix without changing the initial stress field of the latter. Necessary and sufficient conditions are deduced for the existence of such a neutral inclusion. When the constituent materials of the matrix and inclusion are isotropic, these conditions are firstly specified and then illustrated by two simple examples. To cite this article: Q.-C. He, C. R. Mecanique 330 (2002) 691–696. 相似文献
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Submarine warfare continues to pose a threat in present-day military operations. Visual displays play a dominant role for operator detection and classification of underwater and surface targets. However, the visual modality is ineffective for the detection of transient signals. In spite of quieter submarines, transient sounds such as hull popping are difficult to disguise, which makes them more likely to be detected via an auditory display. Operators tend to use auditory displays less often because several factors can impede effective aural processing. In this paper, the sonar problem is reviewed followed by some proposed techniques for making more effective use of the auditory modality for the presentation of sonar signals as a means of further improving operator detection and classification of targets. Some recommendations for augmenting the aural presentation of sonar signals over headphones are then discussed. Key research areas include: (1) a reduction of the sound level of the ambient noise in noisy environments should improve the likelihood that the operator will detect weak signals; (2) the provision to replay sound bites of interest and to compare these against a library of known archetypes should lead to increased accuracy in target classification; (3) the ability to present sonar beams in a three-dimensional auditory display where the spatial position of each sonar beam corresponds to the actual position of the source in the ocean should enable the operator to monitor multiple beams and increase his/her situational awareness. Ultimately, the viability of an auditory display is dependent on operator hearing acuity. 相似文献
954.
A novel method, designated the holographic spectrum reconstruction (HSR) method, is proposed for achieving simultaneous display of the spectrum and image of an object in a single plane. A study of the scaling behaviour of both the spectrum and the image has been carried out and based on this study, it is demonstrated that a lensless coherent optical processor can be realized. 相似文献
955.
The microwave heating of three-dimensional blocks, by the transversemagnetic waveguide mode TM11, is considered in a long rectangularwaveguide. The governing equations are the forced heat equationand a steady-state version of Maxwell's equations, while theboundary conditions take into account both convective and radiativeheat loss. Semi-analytical solutions, valid for small thermalabsorptivity, are found using the Galerkin method. The electricalconductivity and the thermal absorptivity are assumed to betemperature dependent, while both the electrical permittivityand magnetic permeability are taken to be constant. Both a quadraticrelation and an Arrhenius-type law are used for the temperaturedependency. As the Arrhenius-type law is not amenable analytically,it is approximated by a rationalcubic function. A multivaluedsteady-state temperature versus power relationship is foundto be possible for both types of temperature dependency. Atthe critical power level thermal runaway occurs when the temperaturejumps from the lower (cool) temperature branch to the upper(hot) temperature branch of the solution. The semi-analyticalsolutions are compared with numerical solutions of the governingequations for various special cases such as the limits of smalland large heat loss at the edges of the block. An excellentcomparison is obtained between the semi-analytical and numericalsolutions, on both temperature branches for the Arrhenius-typelaw. For the quadratic temperature dependency the comparisonis excellent on the low branch but the semi-analytical theorysignificantly underpredicts the temperature on the upper solutionbranch. 相似文献
956.
K. A. Krasnov V. G. Kartsev A. S. Gorovoi V. N. Khrustalev 《Chemistry of Natural Compounds》2002,38(5):450-457
The three-dimensional structure of 1,3-dimethyl-5-(4-allyloxybenzyl)-5-cytisylmethylbarbituric acid was found by x-ray structure analysis. A conformation with proximal cytisine and 2,4,6-trioxopyrimidine moieties was observed. Analogous structures for other synthesized 1,3-dimethyl-5-arylmethyl-5-cytisylmethylbarbituric acids and their 2-thio analogs were proved and the intramolecular effects caused by mutual magnetic shielding of spatially proximal groups were studied using PMR. 相似文献
957.
Improvement in refractive-index change in LiNbO3:Ce:Cu by applying an external electric field 下载免费PDF全文
By jointly solving two-centre material equations with a nonzero external electric field and coupled-wave equations, we have numerically studied the dependence of the non-volatile holographic recording in LiNbO3:Ce:Cu crystals on the external electric field. The dominative photovoltaic effect of the non-volatile holographic recording in doubly doped LiNbO3 crystals is directly verified. And an external electric field that is applied in the positive direction along the c-axis (or a large one in the negative direction of the c-axis) in the recording phase and another one that is applied in the negative direction of the c-axis in the fixing phase are both proved to benefit strong photorefractive performances. Experimental verifications are given with a small electric field applied externally. 相似文献
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960.
Jiayi Xu Yahui Zhang Menghan Wang Prof. Yu Gao Prof. Haijun Chen 《European journal of organic chemistry》2023,26(40):e202300833
Organic fluorophores with highly efficient luminescence in both solution and solid states have attracted significant attention due to their ability to circumvent the limitations of aggregation-caused quenching and aggregation-induced emission type molecules. However, their development and wide-range applications are hampered by extremely complex synthetic methodologies and limited frameworks with dual-state emission (DSE) structural characteristics. In sharp contrast to the reported luminogens with big and planar π systems or highly conjugated and twisted structures, we discovered novel three-dimensional scaffolds in one molecule to achieve DSE. These molecules allowing for rapid access showed completely different molecular packing manners from those of planar conjugated molecules and exhibited excellent optoelectronic properties with diminished intermolecular π−π stacking interactions due to steric hindrance. Our findings should open new avenues for designing DSE molecules with new frameworks, which will enable more successful development of dual-state emitters for their broad applications in the future. 相似文献