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排序方式: 共有423条查询结果,搜索用时 46 毫秒
51.
52.
Ajit B Shinde Nilesh B Shrigadi Shriniwas D Samant 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2003,78(12):1234-1238
The milling by‐product of rice, rice husk, constitutes a major waste of the agricultural industry. It is mainly used as a fuel additive for various purposes, leaving behind residual ash which is rich in silica (Biogenic silica). In the present project, rice husk silica was impregnated with Fe3+, Sb3+, Bi3+ and Al3+ from both their aqueous and organic solutions. The resultant catalysts were activated at 120 °C and 550 °C and used for the Friedel–Crafts benzylation of benzene using benzyl chloride. Copyright © 2003 Society of Chemical Industry 相似文献
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A volume integral equation method (VIEM) is used to calculate the elastostatic field in an isotropic elastic half-plane containing circular inclusions subject to remote loading parallel to the traction-free boundary. The material of the inclusions may be either isotropic or anisotropic and they are assumed to be distributed in square or hexagonal array. A detailed analysis of the stress field at the interface between the matrix and one of the inclusions is carried out for different distances between the inclusion and the surface of the half-plane. The results of the calculations are compared with available results. The VIEM is shown to be very accurate and effective for investigating the local stresses in the presence of multiple inclusions. The method can be applied to multiple inclusions of arbitrary geometry and elastic properties embedded in extended isotropic elastic media. 相似文献
55.
This paper presents the comparison of a three dimensional Computational Fluid Dynamics (CFD) analysis with empirical performance data of a 0.6 m impulse turbine with fixed guide vanes used for wave energy power conversion. Pro-Engineer, Gambit and Fluent 6 were used to create a 3-D model of the turbine. A hybrid meshing scheme was used with hexahedral cells in the near blade region and tetrahedral and pyramid cells in the rest of the domain. The turbine has a hub-to-tip ratio of 0.6 and results were obtained over a wide range of flow coefficients. The model yielded a maximum efficiency of approximately 54% as compared to a maximum efficiency of around 49% from experiment. A degree of insight into flow behaviour, not possible with experiment, was obtained. 相似文献
56.
In this communication, the stability of the double-diffusive solar ponds has been investigated in the linear approximation. The corresponding linearized system of equations of motion is reduced to a single integro-differential equation using the Green-function technique. In contrast to the conclusions of Veronis that, initially, the instability occurs as an oscillatory mode and at a value of RT (Rayleigh number for temperature) greater than RS the motion becomes steady, the present analysis shows that, initially, as RT increases from zero but remains considerably less than RS, exponentially growing and decaying modes (steady motion) occur first; for a value of RT more than a critical value RTc, the motion becomes oscillatory. This oscillatory motion may, due to the basic non-linear dynamics of the system, even become aperiodic. Further, for RS → ∞, the minimum value of RT for which steady motions can occur tends to , where where KS and KT are diffusivity coefficients for salt and temperature, respectively; as a contrast, according to Veronis, being the kinematic viscosity. 相似文献
57.
W. Jack Lackey John A. Hanigofsky Garth B. Freeman Regina D. Hardin Ajit Prasad 《Journal of the American Ceramic Society》1995,78(6):1564-1570
The feasibility of preparing small-diameter, high-strength, thermally stable silicon carbide fiber tows by the continuous chemical vapor deposition (CVD) of SiC onto carbon fiber tows was experimentally evaluated. Calculations of bending stresses and stresses caused by thermal expansion mismatch between the substrate and coating were used to evaluate the influence of coating thickness and substrate fiber diameter and type. Statistically designed and analyzed processing studies quantitatively showed the influence of key CVD process variables (temperature, pressure, and flow rates of CH3 SiCl3 and H2 ) on fiber attributes such as coating thickness and uniformity, surface roughness, percent agglomeration, and strength. Emphasis was given to conceiving and evaluating various fiber spreading devices in order to enhance coating uniformity and to minimize filament agglomeration within a tow. Uniform coatings and fiber tensile strengths as high as 4 GPa were achieved. 相似文献
58.
Water quality management of a stretch of river Yamuna: An interactive fuzzy multi-objective approach 总被引:2,自引:2,他引:0
This paper presents an Interactive Fuzzy Multi-Objective Linear Programming (IFMOLP) model for water quality management in
a river basin. The IFMOLP model formulated will first evaluate dissolved oxygen (DO) concentrations or DO deficits at a point
in different reaches depending on the overall Biochemical Oxygen Demand (BOD) concentration present in the respective drain.
Subsequently, the model incorporates the aspirations and conflicting objectives of the decision maker (DM) by taking into
consideration the aspects relevant for pollution control boards as well as dischargers responsible for generating wastewater.
The uncertainty associated with specifying the water quality criteria (based on DO concentration or DO deficit) and treatment
cost to remove pollution level is incorporated by interacting the decision maker. In this process DM is asked to specify the
reference aspiration levels of achievement for the values of all membership functions generated with respect to each objective.
This provides flexibility for the pollution control authorities and dischargers to specify their aspirations. IFMOLP model
developed herein is then used in a case study for the evaluation of optimal BOD removal in different drains located across
the river Yamuna at New Delhi, India. The presented model will simulate the allocation of waste load efficiencies with satisfactory
results which will indicate usefulness of the model in managing more complex river basins along with better flexible policies
of water management. 相似文献
59.
Ajit R. Dhamdhere Ajay P. Malshe William F. Schmidt William D. Brown 《Microelectronics Reliability》2003,43(2):287-295
As applications continue to demand increasingly higher optical output power and longer lifetime, thermo-mechanical stresses on dissimilar materials interfaced for packaging pose an ever-growing challenge for the realization of a durable system. Particularly important for an epitaxy-down configuration is the die-attachment interface, which is desired to be defect free and stress managed for reliable optical alignment. A knowledge of the changes in the physical defect density and magnitude of the thermo-mechanical stress present in the active region as a function of the fabrication process and aging is crucial to an understanding of the influence of the process parameters and operating conditions on device performance and reliability. In this study, we investigated high power laser diode array packages aged under various conditions. Microscopic defect analyses of the die attachment interface and device stress were carried out using primarily metallography, scanning electron microscopy, scanning acoustic microscopy, microhardness, and micro-Raman spectroscopy. It was noted that the intermetallic compounds and microscopic physical defects at the die attach interface are detrimental to transient heat transfer, and thus, overall package reliability. Using micro-Raman spectroscopy, we found that tensile stress near the bar-package interface increases with aging for the first few hundred hours and then decreases with further aging. 相似文献
60.
In a recent paper a method is described for constructing certain approximations to a general element in the closure of the convex hull of a subset of an inner product space. This is of interest in connection with neural networks. Here we give an algorithm that generates simpler approximants with somewhat less computational cost. 相似文献