Glycinium chlorochromate (GCC) supported onto silica gel was used as an effective oxidizing agent for the aromatization of 1,4‐dihydropyridines to corresponding pyridine. 相似文献
In this paper, we present numerical computational methods for solving the
fracture problem in brittle and ductile materials with no prior knowledge of the topology
of crack path. Moreover, these methods are capable of modeling the crack initiation.
We perform numerical simulations of pieces of brittle material based on global
approach and taken into account the thermal effect in crack propagation. On the other
hand, we alsopropose a numerical method for solving the fracture problem in a ductile
material based on elements deletion method and also using thermo-mechanical behavior
and damage laws. In order to achieve the last purpose, we simulate the orthogonal
cutting process. 相似文献
As a first endeavor, the buckling analysis of functionally graded (FG) arbitrary straight-sided quadrilateral plates rested
on two-parameter elastic foundation under in-plane loads is presented. The formulation is based on the first order shear deformation
theory (FSDT). The material properties are assumed to be graded in the thickness direction. The solution procedure is composed
of transforming the governing equations from physical domain to computational domain and then discretization of the spatial
derivatives by employing the differential quadrature method (DQM) as an efficient and accurate numerical tool. After studying
the convergence of the method, its accuracy is demonstrated by comparing the obtained solutions with the existing results
in literature for isotropic skew and FG rectangular plates. Then, the effects of thickness-to-length ratio, elastic foundation
parameters, volume fraction index, geometrical shape and the boundary conditions on the critical buckling load parameter of
the FG plates are studied. 相似文献
In this study, polysulfone/wood sawdust (PSf/WSD) mixed matrix membrane (MMM) was prepared as a novel substrate layer of thin‐film composite (TFC) membrane in water desalination. The main aim was to evaluate how different amounts of WSD (0‐5 wt%) and PSf concentrations (12‐16 wt%) in the porous substrate affect the properties of the final TFC membranes in the separation of organic and inorganic compounds. Morphological and wettability studies demonstrated that the addition of small amount of WSD (less than or equal to 1 wt%) in the casting solution resulted in more porous but similar hydrophobic substrates, while high loading (greater than or equal to 2 wt%) of WSD not only changed the substrate wettability and morphology but also increased and decreased the swelling and mechanical properties of substrate layer. Therefore, PA layer formed thereon displayed extensively varying film morphology, interfacial properties, and separation performance. Based on approximately stable permeate flux (ASPF) and apparent salt rejection efficiency (ASRE), the best TFC membrane was prepared over the substrate with 12 to 14 wt% of PSf and around 0.5 to 1 wt% of WSD. Although notable improvements in permeate flux were obtained by adding a small amount of sawdust, the results clearly indicate that the salt rejection mechanism of TFC membrane was different from the glycerin rejection mechanism. Furthermore, durability results of TFC membranes showed that in continuous operation for 30 days, TFC‐14/0.5 and TFC‐14/01 have the maximum plateau levels of stable permeate flux and salt rejection among the all TFC membranes. 相似文献
A mathematical model and the results of calculating the ignition and combustion of energetic condensed systems based on mono- and polydispersed aluminum diboride particles in air flows in constant-cross-section channels are reported. The kinetic characteristics of the transformations that separate aluminum diboride particles formed by gasification of energetic condensed systems undergo in a high-temperature oxidizing medium were determined using the dependences of the ignition induction period and combustion time on the air temperature and diameter and initial temperature of the particles. These dependences, in turn, were calculated using the model of parallel chemical reactions. The range of combustion conditions corresponding to the initial air temperatures from 300 to 2000 K and Mach numbers in the channel from 0.1 to 1.5 was considered. The influence of the aluminum diboride particle size and of the rate and initial temperature of the air flow on the combustion efficiency was demonstrated. The relationships between the combustion completeness factor of aluminum diboride particles at various initial parameters of the air flow and gasification products of energetic condensed systems at various fuel mixture equivalence ratios, corresponding to the diffusion and kinetic combustion, were determined. The conditions of the transition between the diffusion and kinetic control modes were found.
This paper presents the extension of a flexibility-based large increment method (LIM) for the case of cyclic loading. In the last few years, LIM has been successfully tested for solving a range of non-linear structural problems involving elastoplastic material models under monotonic loading. In these analyses, the force-based LIM algorithm provided robust solutions and significant computational savings compared to the displacement-based finite element approach by using fewer elements and integration points. Although in cyclic analysis a step-by-step solution procedure has to be adopted to account for the plastic history, LIM will still have many advantages over the traditional finite element method. Before going into the basic idea of this extension, a brief discussion regarding LIM governing equations is presented followed by the proposed solution procedure. Next, the formulation is specified for the treatment of the elastic perfectly plastic beam element. The local stage for the beam behavior is discussed in detail and the required improvement for the LIM methodology is described. Illustrative truss and beam examples are presented for different non-linear material models. The results are compared with those obtained from a standard displacement method and again highlight the potential benefits of the proposed flexibility-based approach. 相似文献
We construct an exact solution of the Friedmann equations with a phantom scalar matter field originating in string field theory
and show the absence of the big-rip singularity. The notable features of the model are a ghost sign of the kinetic term and
a special polynomial form of the effective tachyon potential. The constructed solution is stable under small fluctuations
of the initial conditions and special variations of the form of the potential.
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Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 148, No. 1, pp. 23–41, July, 2006.
An erratum to this article is available at . 相似文献
In this paper, we give the characterization of S-essential spectra, we define the S-Riesz projection and we investigate the S-Browder resolvent. Finally, we study the S-essential spectra of sum of two bounded linear operators acting on a Banach space. 相似文献