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《材料科学技术学报》2001,(3)
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On the basis of a survey of works, we demonstrate the priority of the Lviv school of mechanics in the field of creation and development of the deformation theory of limiting equilibrium of bodies with cracks known as the
k
-model. The theory is based on the criterion of crack opening displacement proposed by Leonov and Panasyuk and on the procedure of evaluation of this quantity by modeling the inelastic zones in front of the crack by cuts the edges of which are loaded by certain stresses 0 whose physical meaning is determined by the properties of the material. This method (known as the model of plastic strips) is also used for the determination of the development of plastic zones at the crack tip for various configurations of plates and loads and also in twisted bodies. The results of numerical calculations agree with the experimental data. 相似文献
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《Composites Part A》2003,34(8):689-694
An experimental investigation of the effect of nanotube length and aggregate size on the mechanical and electrical properties of the composites was reported. Three treatments, that affect mainly the length and aggregate size, were applied on the CVD MWNTs before they were added into a resin matrix. They had a very clear impact on the dielectric properties of the composites and on the improvement efficiency. There was an insulator-to-conductor transition with the as-prepared MWNTs at 0.5 wt%. Regarding the mechanical properties, the addition of MWNTs increased the Young's modulus and reduced the fracture strain. In that case, the pre-treatment on MWNTs, however, had a much more moderate effect on the improvement efficiency. 相似文献
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Edith Penrose’s Theory of the Growth of the Firm and the strategic management of multinational enterprises 总被引:1,自引:1,他引:0
– | This paper provides a formal model of Edith Penrose’s Theory of the Growth of the Firm which has important implications for the strategy of multinational enterprises. |
– | The model provides an analysis of the trade-off between product diversification and foreign market penetration. It also can account for the speed of entry into foreign markets. |
– | Formalizing Penrose’s Theory of the Growth of the Firm provides an account of internationalization incorporating geographical expansion patterns, sequential decision making and learning. |
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Evidence of the physical existence of the spatial coherence moiré is obtained by confronting numerical results with experimental results of spatially partial interference. Although it was performed for two particular cases, the results reveal a general behavior of the optical fields in any state of spatial coherence. Moreover, the study of the spatial coherence moiré deals with a new type of filtering, named filtering of classes of radiator pairs, which allows changing the power spectrum at the observation plane by modulating the complex degree of spatial coherence, without altering the power distribution at the aperture plane or introducing conventional spatial filters. This new procedure can optimize some technological applications of actual interest, as the beam shaping for instance. 相似文献
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Effects of the Composition of Electrodeposited Fe-Ni-P Alloy on the Thermostability and Magnetic Properties 总被引:4,自引:0,他引:4
The magnetic properties, structure defects of electrodeposited Fe-Ni-P alloys with various compositions and the thermostability at amorphous state have been studied by DSC, positron annihilation and electronic integrating instrument methods. The results show that the thermostability of amorphous Fe-Ni-P alloys increases with Fe content. Emergence and recrystallization of stable phases defer as the P content of the coating increases. The minimum Hc, Br and Ph occur at 9.4 P (wt pct) content. Maximum Hc, Br and Ph occur at the weight ratio of Fe to Ni equaling to 1/9. 相似文献
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《中国标准化(英文版)》2005,(5)
C hina is one of the countries suffering from them ost severe earthquake disasters.The death toll fromearthquakes in C hina is estim ated to be600,000,ac-counting for1/3of the global num ber.Tw enty-threeprovincial capitals in C hina and tw o thirds of its bigcities,each w ith a population over one m illion,are lo-cated at high risk areas w ith seism ic intensity overⅦdegrees.The tw o violent earthquakes in the w orld dur-ing the20th century,w hich both caused a death toll ofover200,000and o… 相似文献
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Marta Weiss 《History of Photography》2013,37(4):431-444
From 1859 to 1878 the British sculptor Richard Cockle Lucas assembled at least sixteen albums containing photographs of himself in numerous guises, ranging from Shakespearean roles to embodiments of specific emotions. Lucas utilised the practice of dressing up in front of the camera in conjunction with the album format as an ongoing means of experimenting with photography’s capacity to convey human expression, and as an extension of his concerns as a sculptor. Lucas’s albums, which also include photographs of his work in sculpture, represent the first sustained pursuit of photographic self-depiction in such a wide range of roles. Read in conjunction with Lucas’s own writings on expression in photography and sculpture, the albums reveal how Lucas viewed photographic self-portraiture as a form of ‘living sculpture’ to be enacted before the camera. 相似文献
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A. K. Alekseev 《Journal of Engineering Physics and Thermophysics》2002,75(2):446-452
Consideration has been given to the employment of the conjugate problems of first and second orders, which are applied to solution of the inverse problems of heat exchange, to calculate the error of solution of the primal problem from the data on the error of the initial information. It has been shown that the algorithms of solution of the inverse problems of heat exchange in a variational formulation make it possible to directly determine the error of the corresponding primal problems by calculation of the Hessian range. 相似文献
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I. V. Andreiev I. O. Gnatenko S. O. Lysovenko V. G. Gargin 《Journal of Superhard Materials》2018,40(2):127-130
The results are presented of the barothermal treatment studies of a WC–6Co hard alloy at high pressure (7 GPa). It is shown that such a treatment of hard alloy leads to the deterioration of the basic physico-mechanical characteristics, specifically the strength at the contact, and the coercive force, which is stipulated by the increase of the defects amount in the structure of the carbide phase of the hard alloy. 相似文献
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S. P. Dodd M. Cankurtaran G.A. Saunders B. James 《Journal of Materials Science》2001,36(10):2557-2563
Ultrasonic wave velocity measurements have been used to determine the elastic stiffness moduli and related elastic properties of high-purity, dense -Si3N4 ceramic samples as functions of temperature in the range 150–295 K and hydrostatic pressure up to 0.2 GPa at room temperature. Due to its covalently bonded, rigid structural framework -Si3N4 is an elastically stiff material; the elastic stiffness moduli of the ceramic at 295 K are: C
L = 396 GPa, = 119 GPa, B
S = 238 GPa, E = 306 GPa, Poisson's ratio = 0.285. The longitudinal elastic stiffness C
L increases with decreasing temperature and shows a knee at about 235 K; the decrease in slope below the knee indicates mode softening. The shear elastic stiffness shows mode softening which results in a plateau centred at about 235 K and an anomalous decrease with further reduction in temperature. The hydrostatic-pressure derivatives of elastic stiffnesses at 295 K are (C
L/P)
P=0 = 4.5 ± 0.1, (B
S/P)
P=0 = 4.3 ± 0.1 and (/P)
P=0 = 0.17 ± 0.02 (pressure < 0.12 GPa). An interesting feature of the nonlinear acoustic behaviour of this ceramic is that, in the pressure range above 0.12 GPa, the values obtained for (/P)
P=0 and the shear mode Grüneisen parameter (S) are small and negative, indicating acoustic-mode softening under these higher pressures. Both the anomalous temperature and pressure dependences of the shear elastic stiffness indicate incipient lattice shear instability. The shear S(=0.005) is much smaller than the longitudinal L(=1.18) accounting for the thermal Grüneisen parameter th(=1.09): since the acoustic Debye temperature D(=923 ± 5 K) is so high, the shear modes play an important role in acoustic phonon population at room temperature. Hence knowledge of the elastic and nonlinear acoustic properties sheds light on the thermal properties of ceramic -Si3N4. 相似文献
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《Drug development and industrial pharmacy》2013,39(17):1831-1851
AbstractThe tableting properties of a number of commercially available β-cyclodextrins were characterized. Fluidity was insufficient for routine direct compression. Compactibility varied by source but was excellent. Lubrication requirements were minimal. An inclusion complex of β-cyclodextrin/Progesterone was formed and the tableting properties of the complex were compared to those of a physical mixture in both directly compressed and wet granulated products. Inclusion complexes spontaneously formed during wet granulation processing. Substantial differences in tableting properties were found as processing variables were changed. β-cyclodextrin exhibits considerable promise as a standard filler binder in tableting. 相似文献
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Yanruo HONG 《材料科学技术学报》1997,13(3):173-178
Four types of solid state electrochemical sensors and their general principles are introduced in the paper. The novel type-IV sensors developed in the last few years are emphasized to study hereafter. The ways to design new electrochemical sensors and the directions to develop new solid electrolytes for new electrochemical sensors are also discussed. 相似文献