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排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
R. S. Aleev V. G. Voronov Z. F. Ismagilova R. R. Safin F. R. Ismagilov 《Chemistry and Technology of Fuels and Oils》2002,38(4):260-265
Worsening of the environmental situation in many regions of Russia in recent decades is to a great degree due to production and refining of oil and gas with a high hydrogen sulfide content. Industrial methods of utilization of hydrogen sulfide are extremely irrational: it is either burned in flares or used for production of sulfur whose quality and quantity pose new problems related to its use. 相似文献
992.
The problem of efficient utilization of the frequency spectrum for satellite systems is investigated; one which results as a consequence of highly crowding adjacent channels. An analytical characterization of the resulting interference channel is introduced and then exploited for interference cancellation. Two classes of cancelers are investigated. The first approach does not benefit from the forward error control (FEC) coding information which limits the performance gain. This motivates the second approach where a joint implementation of interference cancellation and decoding is developed using soft-input-soft-output (SISO) modules along with the iterative structure. It is shown that iterative interference cancellation techniques can achieve significant gains compared with the single-user matched filter receiver 相似文献
993.
Yu. V. Drobyshevskii V. K. Ezhov E. A. Lobikov V. N. Prusakov V. F. Serik V. B. Sokolov 《Atomic Energy》2002,93(1):578-588
The exploding-wire method, the photochemical method of irradiation with a light flux from a high-pressure mercury lamp, a high-intensity spark discharge, and irradiation by a CO2 laser are used to reduce plutonium hexafluoride and to separate it from uranium hexafluoride. The dependence of the reduction of plutonium hexafluoride on the wire material, the mass of the reduced product, and the amount of input energy is investigated.It is shown that the methods presented for reducing plutonium hexafluoride and separating it from uranium hexafluoride can be used under static and dynamic conditions for preparative purposes and on a large scale. 相似文献
994.
The strength of case-hardened parts under cyclic loading can be determined in an experimental manner, but this can produce
a large amount of costs due to the expenditure of material and testing time. Therefore, a calculation method is developed,
that strongly reduces the number of experiments. The presented model is based on Weibull's weakest-link concept and allows
to compute the survival probability of a case-hardened part which is loaded close to the fatigue limit. The essential quantities
in this model are the distribution of Vicker's hardness of the material, the exponents of the Weibull distribution of the
volume and the surface, the residual stress state, the surface roughness and the surface oxidation depth. By integrating the
survival probabilities of the surface and the volume, the survival probability of the entire specimen or part can be calculated,
which allows to compute the fatigue limit. The necessary parameters have to be determined from reference specimens. The model
is successfully examined by comparing experimental and calculated results of smooth and notched case-hardened specimens under
alternating torsion, rotating bending, repeated tension and tension-compression.
Received 20 August 2001 / Accepted 11 November 2001 相似文献
995.
996.
This paper describes a conceptual and theoretical framework to allow better user control over data summarization for knowledge discovery. Basic to the approach is a measure of quality of summarization of data using categories provided by the hierarchical structure of concept ontology. This involves the modeling, using a fuzzy sets approach, of the four criteria implicit in a summarization imperative: minimum coverage, minimum relevance, succinctness, and usefulness. With these criteria modeled, a multicriteria approach is presented, using a decision function aggregating these criteria that provides an overall quality measure to guide the summarization of the data. The development of the theory is first presented for the simple case of a single attribute to clearly delineate the basic issues and approach and then extended to multiple attributes. Finally, approaches to provide a more user-oriented presentation of the summarized data are considered 相似文献
997.
V. Recarte R. B. Pérez-Sáez J. San Juan E. H. Bocanegra M. L. Nó 《Metallurgical and Materials Transactions A》2002,33(8):2581-2591
The martensitic transformation temperatures and the types of martensitic phases have been determined in a wide concentration
range of technological interest for Cu-Al-Ni shape-memory alloys (SMAs) A stability diagram of martensitic phases as a function
of alloy concentration has been determined. It is found that when the aluminum content increases, the transformation changes
from β
3 ⇒ β′3 to β
3 ⇒ γ′3, with an intermediate concentration range where both martensites coexist due to a β
3 ⇒ γ′3+β′3 transformation. On the other hand, an increase of nickel content stabilizes the martensite β′3, changing from a mixed β
3 ⇒ γ′3 + β′3 to a single β
3 ⇒ β′3 transformation. Furthermore, linear relationships between M
s
and Al and Ni concentrations have been obtained for all types of martensitic phases. 相似文献
998.
999.
Thrombin-induced platelet malondialdehyde (MDA) formation and plasma malondialdehyde-like material (MDA-LM) were evaluated
in 12 healthy subjects before and after 1 and 7 days from aspirin (1 g) ingestion. 24 hr after aspirin administration, platelet
MDA was almost abolished while MDA-LM showed a 23% decrease. Platelet MDA and plasma MDA-LM returned to baseline values 7
days after aspirin ingestion. These data suggest that platelet cyclooxygenase pathway affects only in part plasma MDA-LM.
The evaluation of plasma MDA-LM before and after aspirin could be useful for evaluating in vivo platelet cyclooxygenase activation. 相似文献
1000.