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作者 Herke, Richard Alan
書名 Surface force studies on a smectic A liquid crystal
說明 165 p
附註 Source: Dissertation Abstracts International, Volume: 54-10, Section: B, page: 5198
Director: Noel A. Clark
Thesis (Ph.D.)--University of Colorado at Boulder, 1993
A force applied normal to the layers of a smectic A liquid crystal aligned between the two surfaces of a spherical wedge can induce the exclusion in compression or inclusion in dilation of a single smectic layer. This is evidenced by jumps in surface separation with the size of the smectic layers. This thesis reports the study of the dynamics of these events. A novel surface forces apparatus, in which distances are sensed capacitively, has been constructed and used for the examination of these layer events. These experiments reveal an interesting avalanche like yield characteristic. Though the majority of the surface separation change occurs in a jump of short duration, typically about a second, there is a slow precursor acceleration which may last a hundred seconds or more and a slowly decaying tail which may last several hundred seconds. Multiple layer events are also observed in which the individual layer jumps are separated by short periods of reduced separation change, and the duration of each succeeding jump becomes significantly longer. Computer modeling based on the movement of edge dislocations in the sample fails to simulate these events, however, a model based on the helical instability of screw dislocations does indeed reproduce the dynamic features. The picture which emerges is of a cascade of helical instabilities of screw dislocation lines moving out from the center of the spherical wedge
School code: 0051
Host Item Dissertation Abstracts International 54-10B
主題 Physics, General
Alt Author University of Colorado at Boulder
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