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991.
采用DFT方法和HF方法对CO在Cu/ZnO催化剂上的Zn(Ⅱ)和Cu(Ⅰ)表面位上的吸附行为进行了比较研究.结果表明:HF方法给出了较弱的M-CO(M=Zn(Ⅱ),Cu(Ⅰ))表面吸附键描述,但无法正确预测其强弱顺序,MP2方法与DFT方法则给出与实验事实一致的描述.文章还对CO/铜基催化剂吸附体系的IR光谱进行了合理的理论预测.  相似文献   
992.
A method combining glass electrode potentiometry and computer simulation of speciation is described and used to determine the solubility product for S,S′-ethylenediamine disuccinate (EDDS) (also known as ethylenediiminodibutanedioic acid). This previously unpublished constant is validated by re-measuring Ksp for isomeric EDTA4−·H4+ and by a linear free energy relationship. For EDDS4−·H4+, log Ksp=−25.75±0.30.  相似文献   
993.
The accuracy of trace gas abundances retrieved from spectrally resolved infrared limb emission measurements relies, among other things, on the appropriate modelling of radiative transfer through the actual atmosphere. We quantify the mapping of several commonly applied simplifications in radiative transfer modelling on the trace gas abundances retrieval error at the example of the Michelson interferometer for passive atmospheric sounding (MIPAS)/environmental satellite (ENVISAT) space borne Fourier transform infra-red limb emission experiment. The Karlsruhe optimized and precise radiative transfer algorithm (KOPRA) which was used as a tool for this study will be introduced. KOPRA supports accurate modelling of the particular instrument requirements of MIPAS and the observation scenarios during the ENVISAT mission, in particular with respect to its viewing direction and its altitude coverage of the atmosphere. We show that disregarding of horizontal temperature inhomogeneities and non-local thermodynamic equilibrium effects, insufficient accuracy in modelling of field-of-view and apodisation effects, and disregarding individual profiles of isotopic species play the key roles in radiative transfer modelling and lead to systematic retrieval errors which can by far exceed the expected random retrieval error caused by measurement noise.  相似文献   
994.
Summary From the continuum mechanics points of view, most of commercial fibre-reinforced composites (FRCs) can be considered to be anisotropic materials with one of the five material symmetries: transverse isotropy, orthotropy, tetratropy, hexatropy and octotropy, as illustrated in the preceding paper (Part I) [1]. No properly general formulation of constitutive equations for tetratropic, hexatropic and octoctropic types of FRC has been found in the literature. In this paper, the restriction to the admissible deformation of a FRC imposed by the failure strains of the fibres is investigated. The complete and irreducible two-dimensional tensor function representations regarding tetratropy, hexatropy and octotropy derived in Part I are applied to formulate constitutive equations for FRCs in plane problems of elasticity, yielding and failure in the present work, and of heat conduction, continuum damage and asymmetric elasticity in a continued work (Part III, forthcoming).The supports from the Alexander von Humboldt Foundation, Germany and the Research Foundation of Tsinghua University, P. R. China are acknowledged by the first author.  相似文献   
995.
The remarkable properties of shape memory alloys have increasing the interest in applications in different areas varying from biomedical to aerospace hardware. Despite the large number of applications, the modeling of SMA is the objective of many researches developed in order to describe all details of its thermomechanical behavior. The present contribution revisits a constitutive model presented by Savi et al. (2002), which is built up on the classical Fremond’s model, in order to contemplate the horizontal enlargement of the stress–strain hysteresis loop. Numerical simulations present qualitative agreement with experimental data, showing pseudoelastic, one-way and two-way shape memory effects.  相似文献   
996.
《Tetrahedron》2003,59(4):555-560
The difficulties to obtain convenient monocrystals of the important fungicide RPA 406194 have been overcome by a combination of solid state 13C NMR, X-ray powder diffraction and molecular modeling. The compound, a 3-aryl tautomer, crystallizes forming infinite chains of molecules bonded by N-H?N hydrogen bonds, leading to needle-shaped crystals. The tautomerism (equilibrium constant and energy barrier) of this compound in solution has been studied.  相似文献   
997.
Reliability is a critical word in industrial applications of Shape Memory Alloys. Accurate and reproducible transformation hysteresis cycles and internal loops were obtained in single crystals using a high resolution automatized equipment. From a mechanical model formulated for a single martensite plate, the shape of the hysteresis cycle is obtained by generalizing the representation toN plates. The observed time effects on the hysteresis loops related to diffusion processes were also taken into account. It allows to explain the martensite recoverable creep and the micromemory effects. Also, the room temperature effects on the parent phase (for instance, summer to winter) acting over the transformation temperature are quantified.Research carried out under the project NATO 920452. Partial support from CICYT is gratefully acknowledged. V. T. acknowledges Dir. Pol. Terr. (Generalitat of Catalonia) for useful support. Fruitful discussions with Drs. F. C. Lovey and J. L. Pelegrina of CAB-Argentina (EEC-ALA/MED contract) are acknowledged.  相似文献   
998.
A computational code has been developed based on a Eulerian–Lagrangian approach in order to model the combustion and the motion of perlite particles in a vertical expansion furnace. The expansion of a single particle, which takes place during its motion in the furnace, has been modeled by taking into account the perlite chemical composition and the gradual variation of the temperature distribution inside the grain. Experiments, performed in a perlite expansion plant, have been used to validate the computational results. The operational characteristics of a perlite expansion furnace have been measured and have served as inlet conditions for the numerical simulation of the combustion and perlite expansion processes.The good agreement between measurements and predictions indicates that the developed computational tool can be used to optimise the perlite expansion process leading to reduced fuel consumption with increased productivity.  相似文献   
999.
Modal reflection, transmission and loss of deeply etched Bragg waveguide gratings were modelled by six European laboratories using independently developed two-dimensional (2D) numerical codes based on four different methods, with very good mutual agreement. It was found that (rather weak) material dispersion of the SiO2/Si3N4 system does not significantly affect the results. The existence of lossless Floquet–Bloch modes in deeply etched gratings was confirmed. Based on reliable numerical results, the physical origin of out-of-plane losses of 1D or 2D photonic band gap structures in slab waveguides is briefly discussed.  相似文献   
1000.
We sketch out the basic properties of three novel exponentially fitted shape functions that generalize to two-dimensional triangular elements the one-dimensional functions used in the well-known Scharfetter-Gummel method. This scheme is widely employed in the finite element approximation of the drift-diffusion equations arising in semiconductor device modelling.  相似文献   
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