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991.
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It is established that bismuth crystals under the simultaneous action of a constant magnetic field and current pulses exhibit a correlation between the microhardness and the mobility of twinning dislocations. It is shown that application of the external fields favors translation of the twinning dislocations along the twin-matrix boundaries. 相似文献
995.
A method of constructing the minimal stabilizing sequence for an interval linear system over the field of real numbers is designed. The problem is shown to be reducible to an interval system of linear algebraic equations. 相似文献
996.
997.
G. Straffelini A. Molinari D. Trabucco 《Metallurgical and Materials Transactions A》2002,33(3):613-624
The dry sliding behavior of a 304L austenitic stainless steel and a duplex 2205 austenitic-ferritic stainless was investigated.
The evolution of wear was characterized by the existence of a sliding-distance transition. In particular, wear passed from
delamination to tribo-oxidation, with a reduction in wear rate. The occurrence of such a transition was interpreted with reference
to a theory of sliding wear based on the formation, by subsurface plastic deformation, of a tribological layer and its detachment
during sliding. It has been found that the transition is controlled by the ability of the tribological system to form, on
its outer part, a protective oxide-rich scale. This introduces a kinetic limitation, which is particularly important in the
case of the duplex 2205, because of its lower ductility in comparison to the 304L steel. In this frame, the influence of sliding
velocity, the particular frictional behavior, the role of chromium in the oxidative wear, and the surface temperature evolution
during sliding could be explained. 相似文献
998.
Combined shape and sizing optimization of truss structures 总被引:1,自引:0,他引:1
In this paper, an evolutionary optimization method is presented for weight minimum problem of a 3-dimensional truss structure
in terms of nodal coordinates and element cross-sectional areas. The structure is subject to stress, local buckling and displacement
constraints. Two types of design variables with different natures are optimized separately: (1) a fully stressed design (FSD)
and scaling techniques are applied to sizing variables and (2) the evolutionary node shift method is applied to shape variables.
Alternating procedure is utilized to couple the two types of variables and to combine the results. The optimum solution is
achieved gradually from the initial configuration design. Two typical truss structures are examined to illustrate the validity
of the method.
Received: 22 October 2001 / Accepted: 04 June 2002
This research work is supported by the National Natural Science Foundation of China under the guarantees no. 10072050 and
10172072, respectively. 相似文献
999.
To improve a company's 'chopping' power it is necessary to apply systems engineering principles to 'project systems' and take the time to plan effectively, to reflect upon what it is that is being done and thereby improve the way things are done. This article takes a systems view of the project and applies systems engineering principles to project management. Projects (complex systems) are needed to create deliverables (which are also complex systems) and investing in the former will be more than paid back in the latter. It is our aim here to clear up some misunderstandings about systems engineering and its role within a complex project and to highlight the need for businesses to take time to improve their processes in the context of good systems engineering practice. 相似文献
1000.
Strain endurance experiments on a filled elastomer were performed at several temperatures. It was found that superimposed prestraining accelerated the ageing process. This process was caused by microstructural changes in the elastomer. In order to evaluate the mechanical properties of a filled elastomer it is necessary to take into consideration not only the ageing effects but also the loading history. 相似文献