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21.
Crystallography Reports - The features of growth of single crystals of cadmium and zinc tungstates by the low thermal gradient Czochralski technique have been investigated. The effect of change in...  相似文献   
22.
Methods were developed to measure longitudinal and transverse sound velocities in porous materials — various Zn-S mixtures and KBr samples. It is shown that, on exposure to ultrasound with a wavelength far exceeding the pore size in pressed samples, a porous body behaves as a continuous medium. Sound velocity in a porous material was found to depend on the quantitative ratio of vacuum, air, and toluene in the pores. Bulk sound velocities estimated using an additive method agree with experimental data within an error not more than 10%. It was found that removal of moisture traces from porous samples led to significant absorption of sound waves. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 50, No. 4, pp. 121–127, July–August, 2009.  相似文献   
23.
The possibility of growing germanium single crystals under low temperature gradients in order to produce a dislocation-free material has been studied. Germanium crystals with a dislocation density of about 100–200 cm?2 have been grown in a system with a weight control of crystal growth at maximum axial gradients of about 1.5 K/cm.  相似文献   
24.
In the present work, we consider a model with a fermionic field that is non-minimally coupled to gravity in the framework of teleparallel gravity. In order to determine the forms of the coupling and potential function of fermionic field for the considered model, we use the Noether symmetry approach. By applying this approach, for the Friedman–Robertson–Walker metric, we obtain the respective potential and coupling functions as a linear and power-law form of the bilinear \(\Psi \) . Furthermore, we search for the exact cosmological solution of the model. It is shown that the fermionic field plays the role of dark energy.  相似文献   
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