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1.
The melting mechanism of polymer crystals is proposed. It is assumed that the melting happens due to forming supervacancies. This mechanism leads the appearance of anisotropic phase of a melt. It is shown that two phases—anisotropic and isotropic—can exist in polymer melts. 相似文献
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It has been shown that, apart from classical vacancies formed as a result of the thermal fluctuations, a crystal can contain
so-called nonclassical vacancies of nonfluctuation nature. The latter vacancies appear when the temperature exceeds a critical
value T
C
. The factor responsible for their formation is a mechanical instability of an ideal crystal. The temperature T
C
is a second-order phase transition point. The vacancies formed as a result of this phase transition are joined together into
small clusters with sizes of the order of several atoms. The above transition makes a substantial contribution to the premelting
process observed experimentally. 相似文献
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Certain guidelines were formulated for conducting mechanical and electronic design, calibration and installation of steel
or aluminum transducers, which may be utilized to monitor internal forces in selected elements of a redundant structure, directly
and independently, without a need for analysis.
Two different transducers are discussed as examples. These were implemented in reinforced-concrete test structures at U.C.
Berkeley, and revealed significant information regarding actual force responses. It is assessed that this information could
not have been analytically predicted or experimentally measured in any other manner. Possible practical applications of such
force transducers, in addition to their potential in experimental research, are suggested. 相似文献
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It is shown that an equilibrium vacancy concentration can be noticeable even at a temperature close to absolute zero. This will be the case if the volume deformation of a crystal is higher than a critical value, which is a second-order phase transition point. 相似文献
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Bridge-condition assessment by modal flexibility 总被引:16,自引:0,他引:16
A bridge-condition assessment method for evaluating the global state of health is formulated based on modal flexibility directly
obtained by processing modal test data, complemented by structural identification. The method is proven and the experimental
and analytical tools that have been developed for implementation are demonstrated on a three-span reinforced-concrete high-way
bridge.
Paper was presented at the 1993 SEM Spring Conference on Experimental Mechanics held in Dearborn, MI on June 7–9. 相似文献
8.
Nesip Aktan Mustafa Yildirim Cengizhan Murathan 《Mediterranean Journal of Mathematics》2014,11(2):775-787
The purpose of this paper is to study a new class of contact manifolds. Such manifolds are called almost f-cosymplectic manifolds. Several tensor conditions are studied for such type of manifolds. We conclude our results with two examples of almost f-cosymplectic manifolds. 相似文献
9.
This paper describes the concept, design, development, and testing and evaluation of a hybrid energy-dissipation device, the
active slip bracing device (ASBD). The device is a Coulomb-friction-based energy dissipater. It consists of multiple friction
surfaces and an active clamping (normal) force mechanism. The ASBD is installed as part of the structural bracing in buildings.
It will activate under low amplitude vibrations for assuring human comfort, and also under large amplitudes to avoid or reduce
damage to the building, and to enhance the safety and comfort level of its occupants during high winds and earthquakes. The
device was tested in a uniaxial testing frame. Experimental results reveal that the ASBD is a viable device with linear friction
and energy-dissipation characteristics. The prototype device has proven to be reliable and durable. 相似文献
10.
The conditions for the existence of supervacancies in oligomer crystals—defects typical of chain systems-are studied. These
vacancies are shown to be nucleated when the temperature exceeds a certain critical threshold T
cr. The equilibrium concentration of supervacancies is calculated. Temperature T
cr is found to be the point of the second-order phase transition. The equation relating transition temperature T
cr and chain length is derived. 相似文献