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51.
With the evolution of QoS-capable 3G wireless networks, the wireless community has been increasingly looking for a framework that can provide effective network-independent end-to-end QoS control. In this article we first construct such a framework and then describe how dynamic SLA-based control can be used to achieve end-to-end QoS in a wired and wireless (UMTS) environment. The proposed framework, which is an extension to the IST CADENUS project, offers effective wired-wireless QoS translation, efficient QoS control and management, and dynamic SLA policy-based QoS provisioning. 相似文献
52.
The dielectric modulus spectra of glasses in the system V2O5-TeO2 have been studied as a function of frequency in the temperature range 230 to 330K. A heterogeneous conductor model developed
recently with the assumption of a sinusoidally varying local conductivity in the conducting phase has been successfully applied
to analyse the data in this glass system. The Kohlrausch-Williams-Watts (KWW) stretched exponential function has also been
used to fit the measured modulus spectra. The exponentβ is found to be correlated to the conductivity fluctuation in the conducting phase as assumed in the heterogeneous model. 相似文献
53.
Self-diffusion coefficients of sodium in the temperature range 300 to 375° C have been measured for glasses in the system Na2O-B2O3-Bi2O3-SiO2, by using a radioactive tracer technique. All these glasses have a two-phase structure. The d.c. resistivities of these glasses were also measured over the temperature range 30 to 375° C. The correlation factors,f, of all the samples have been calculated by using the diffusion coefficients and d.c. resistivity values for temperatures above 300° C. The anomalously largef values in the case of Bi2O3-containing glasses are thought to be due to a distribution of sodium ions in the dispersed as well as the continuous phases in these systems. 相似文献
54.
Das S Basu S Majumdar G Chakravorty D Chaudhuri S 《Journal of nanoscience and nanotechnology》2007,7(12):4402-4411
Sol-gel synthesized SnO2 nanoparticles with an average size of 2.0 nm obtained at 373 K were gradually annealed to 673 K in air for 25 minutes. Sequentially taken transmission electron microscopy (TEM) images showed that particle agglomeration of these non-matrix SnO2 nanocrystals was a very slow process. The blue shifts of the band gap (approximately 2.3 eV) obtained from the optical absorbance spectra were matched with the theoretical results of the size related excitonic binding energies. These calculations also supported the observed slow grain growth. The depth sensitive hardness measurements of the thin films indicated hardness in the range of 5.03 GPa to 6.79 GPa. These undoped and non-matrix SnO2 nanoparticles were also investigated with the X-ray photoelectrons spectroscopy (XPS), atomic force microscope (AFM), X-ray diffraction spectroscopy (XRD), and ac impedance analyzer. 相似文献
55.
Dr. C. R. Chakravorty Dr. M. Chakraborty 《International Journal of Cast Metals Research》2013,26(1):37-42
AbstractMetal-mould reactions in casting Al-Li alloys in sodium-silicate-bonded sand moulds have been studied by the modified Gertsman technique. Molten Al-2.7% Li alloy was poured into a bottom-gated vertical cylindrical mould cavity (150 mm x 50 mm dia) made from no-bake organic-binder-based sands. At the bottom of the mould cavity, a standard AFS three-ram sodium-silicate-bonded sand sample (the test sample) was placed vertically to provide the necessary interface for investigation. After cooling, the reaction products formed at the interface and samples from the bottom portion of the castings were collected for investigation. These were analysed to find Li loss from the casting as a result of metal-mould reactions. The casting was vertically sectioned and visually observed for appearance of blow holes, if any, while the sub-surface was studied for microhardness variation. The as-cast surface and the reaction products were also studied by SEM and X-ray diffraction analysis.The study reveals that the Li in the molten alloy enters into vigorous chemical reaction with the sodium silicate resulting in the release of metallic sodium and formation of reaction products containing αLithium aluminium meta silicate. Li is thus lost from near the surface of the casting. Probably, the sodium released causes the gas blow holes in the sub-surface of castings due to its high vapour pressure at the working temperature. 相似文献
56.
57.
Non-broken filament length (NBFL) is one of the most important quality parameter of silk cocoon because it is directly proportional to reeling speed. Due to excessive breaks during withdrawal of filament from tasar cocoons, the average NBFL ranges from 150 to 175 m. The average NBFL of muga cocoon is at par with tasar cocoons because of lower filament length. In case of mulberry silk cocoons, the average NBFL is above 450 m due to higher filament length and occurrence of very few breaks during reeling. The statistical term skewness denotes the asymmetry in distribution of data. The maximum frequency i.e. mode value for NBFL of tasar and muga cocoons is lower than median and average and hence the skewness is positive. In case of mulberry varieties, negative value of skewness is observed as the mode value is higher than median and average. This parameter establishes the reason for higher reeling speed about 100 m/min for mulberry cocoons as against only 25 m/min in case of tasar and muga cocoons. 相似文献
58.
In practical civil engineering, the necessity of covering large column free open areas with shell surfaces is often an issue. Such areas in medicinal plants and automobile industries prefer entry of north light through the roofing units. Doubly curved singly ruled conoidal shells are stiff and easy to fabricate as surfaces and fit excellently to the above-mentioned industrial requirements. Today, the engineers intend to use laminated composites to fabricate these shell forms. Engineers are also concerned with the performance evaluation of different stacking sequences to maximize the stiffness for a given quantity of material consumption. First ply failure load analysis of composite plates appears abundantly in the literature, but on composite shells, only a few papers are found (though not on conoidal shells). This paper addresses an important issue with which the practical engineers are often concerned regarding performance evaluation of different laminations (including antisymmetric and symmetric cross and angle plies) in terms of first ply failure load of composite conoids. The paper uses the finite element method as the mathematical tool and concludes logically to a set of inferences of practical engineering significance. 相似文献
59.
Twenty-one patients between the ages of 68 and 89 years with osteoarthrosis of hips and/or knee joints wre studied. One group was treated with fenoprofen 300 mg t.d.s. for 5 days, and the other group with 600 mg t.d.s. for 5 days. No therapeutic advantage was found with the higher dose, and the side-effects were minimal on either dosage. Treatment of elderly patients with the smaller dose is recommended. 相似文献
60.