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排序方式: 共有5877条查询结果,搜索用时 15 毫秒
1.
The author focusses on advances in equipment that offset physically functional limitations. He discusses how disabled and elderly people are using aids that enhance mobility (walking a certain distance, lifting a weight, or climbing stairs) as well as sensory faculties (seeing print, hearing conversation, and speaking intelligibly) 相似文献
2.
N. A. Sivov A. I. Martynenko G. N. Bondarenko M. P. Filatova E. Yu. Kabanova N. I. Popova A. N. Sivov E. B. Kruts’ko 《Petroleum Chemistry》2006,46(1):41-59
Structures and compositions of the monomers guanidine acrylate and guanidine methacrylate, their homopolymers, and copolymers with diallyldimethylammonium chloride enriched in acrylate comonomer units were determined. It was shown that ampholytic copolymers, owing to their ionic nature, contained comonomeric guanidine acrylate or methacrylate units and diallyldimethylammonium chloride units, as well as the acrylate comonomer with the diallyl counterion and polymeric acrylate and diallyl ion pairs. It follows from IR and 1H NMR data that guanidine methacrylate has the same structure (with two hydrogen bonds) in the solid state and in solutions. Guanidine acrylate structures in the solid state and in dimethylsulfoxide are identical and analogous to guanidine methacrylate structure in this solvent. In water, the guanidine acrylate structure has another type of hydrogen bonding (with one hydrogen bond, where the proton is shifted toward the guanidine group). These features of hydrogen bonding of guanidine acrylate and guanidine methacrylate are also retained in their homopolymers and copolymers with diallyldimethylammonium chloride. It was shown that the thermal stability of the copolymers was higher than that of their homopolymers, confirming the formation of intramolecular ion pairs of oppositely charged units of ampholytic copolymers. Moreover, the thermal stability of guanidine methacrylate-diallyldimethylammonium chloride copolymers is higher than that of guanidine acrylate-diallyldimethylammonium chloride copolymers. 相似文献
3.
I. A. Ovid’ko 《Journal of Materials Science》2007,42(5):1694-1708
An overview of experimental study, computer simulations and theoretical models of fracture of nanocrystalline materials is
presented. The key experimentally detected facts on ductile and brittle fracture processes are discussed. Special attention
is paid to computer simulations and theoretical models of nucleation and growth of nanocracks and nanopores in deformed nanocrystalline
materials. Also, we discuss mechanisms for fracture suppression in such materials showing good ductility or superplasticity. 相似文献
4.
The basic physicochemical principles of preparation of emulsion fuel compositions based on heavy and extra-heavy crude cuts
were analyzed with consideration of the nature and content of the phases constituting the emulsion, type of chemical additives
— emulsifiers and stabilizers, and type of equipment for production of emulsion fuels.
__________
Translated from Khimiya i Tekhnologiya Topliv i Masel, No. 5, pp. 51–56, September–October, 2007. 相似文献
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V. S. Bessmertnyi N. I. Min’ko P. S. Dyumina V. P. Krokhin S. V. Semenenko M. A. Lipko 《Glass and Ceramics》2005,62(11-12):386-387
A technology for the synthesis of synthetic minerals (using the example of spinels) using a low-temperature plasma flame is developed. The diagnostic properties of spinels are identified. 相似文献
8.
The relationship between teachers' judgments versus actual performance on curriculum-based measures in reading was examined. A total of 30 regular education teachers were asked to predict the oral reading fluency score of students along with a rating scale of reading subskills. Correlations between teacher judgment measures and student performance found that teachers were accurate reporters of student performance levels in reading. However, some questions were raised whether teachers were accurate at predicting the actual level of student oral reading fluency when effect sizes were used to compare teacher judgment and actual student performance. Recommendations for continued research in understanding the parameters of the accuracy of teacher judgment are made. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
9.
Victor Chabanenko Roman Puźniak Adam Nabiałek Sergei Vasiliev Vladimir Rusakov Loh Huanqian Ritta Szymczak Henryk Szymczak Jan Jun Janusz Karpiński Vitaly Finkel 《Journal of Low Temperature Physics》2003,130(3-4):175-191
We present a study of magneto-thermal instabilities in polycrystalline MgB2 superconductor, by magnetic hysteresis loop measurements and by investigations of magnetic flux dynamics with a miniature Hall probe. Temperature and magnetic field ranges where the flux jumps may be observed have been determined. On the basis of measurements of the magnetic flux dynamics, an average magnetic diffusivity describing the process of the flux jump is estimated. This parameter is compared with the thermal and magnetic diffusivities calculated on the basis of available data for thermal conductivity, heat capacity and resistivity. It is shown that the estimated value of the field of the first flux jump is influenced significantly by the field dependence of specific heat. In order to explain the observed phenomenon, the temperature reached by the sample during the flux jump at different magnetic fields is calculated. 相似文献
10.
L. P. Podenok L. I. Sharakhovskii V. D. Shimanovich O. I. Yas’ko 《Journal of Engineering Physics and Thermophysics》1997,70(1):95-99
The influence of heat transfer processes in arc discharges on the development of thermal instability is considered. A substantial
dependence of the process of destabilization on the plasma properties is shown by the example of argon and helium arcs.
Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 70, No. 1, pp. 93–98, January–February, 1997. 相似文献