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The interatomic potential of the system I-I at intermediate and small distances is calculated from atomic DFS electron densities within a statistical model. Structures in the potential, due to the electronic shells, are investigated. Calculations of the elastic differential scattering cross section for small angles and several keV impact energies shoe a detailed peak pattern which can be correlated to individual electronic shell interaction. 相似文献
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Z. A. Samoilenko N. N. Ivakhnenko E. I. Pushenko E. G. Pashinskaya V. N. Varyukhin A. V. Zavdoveev 《Technical Physics》2013,58(7):1011-1015
The atomic order in low-carbon steel strained by screw extrusion making the microstructure finer and changing the phase ratio in the material is studied by X-ray diffraction analysis. The steel is found to consist of multiscale structural fractions: a finely crystalline (300–600 Å) α-Fe matrix, nanodimensional (180–250 Å) Fe3C and Fe3Si or Fe5Si3 phases, and a fraction with randomly arranged atoms. A second-order order-disorder phase transition is revealed with order prevailing in the longitudinal (‖) section of the samples and disorder prevailing in their cross (⊥) section. Sets of “extended” and “compressed” planes are found to coexist in the structure for the first time, with extended planes prevailing in the (‖) section and compressed planes prevailing in the (⊥) one. 相似文献
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《Physica A》2002,303(1-2):119-132
The equilibrium state of a triangular pile of particles, interconnected by linear springs and subjected to the force of gravity, is explored algebraically. A subset of the springs is treated as weak in relation to the others and perturbation theory is used to obtain the zero order and first order expressions for the equilibrium positions of the particles. The zero order results prove to satisfy a thermodynamic limit. In contrast, the first order results fail to exhibit a thermodynamic limit because the perturbation expansion parameter proves to be a function of the number of rows of particles in the triangle. 相似文献
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Traian Mazilu M?d?lina Dumitriu Cristina Tudorache 《Journal of sound and vibration》2011,330(15):3729-3743
The paper herein deals with the study of the dynamic behaviour generated by the instability of the vibration of a loaded mass, uniformly moving along an Euler-Bernoulli beam on a viscoelastic foundation, induced by the anomalous Doppler waves excited in the beam. This issue is relevant for the case of modern trains travelling along a track with soft soil when the trains speed exceeds the phase velocity of the waves induced in the track. The model corresponds to a railway vehicle reduced to a loaded wheel running along a (half) track. The beam takes account of the bending stiffness of the rail and the mass of the track, including the mass of the rail, semi-sleepers and half of the ballast layer, where the viscoelastic foundation represents the subgrade. The model includes the wheel/rail Hertzian contact and it allows the simulation of the possibility of contact loss. The nonlinear equations of motion are integrated using a numerical approach based on the Green’s function method. When the vibration becomes unstable, the system evolution is a limit cycle characterised by a succession of shocks, due to the action of two opposite factors: the anomalous Doppler waves that pump energy at the interface between the moving mass and the beam, thus forcing the mass to take off, and the static load that push the mass downwards. The frequency of the shocks increases at higher velocity and the magnitude of the impact force decreases; the most dangerous velocity is the critical one, which represents the stability limit of the linear approximation of the motion equations. The transient behaviour that precedes the limit cycle appearance is being analysed. The Hertzian contact influences the time history of the limit cycle and the magnitude of the impact force and, therefore, it is essential to be included in the model. To the authors’ knowledge, this problem has never been dealt with. 相似文献
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Juan A. Navarro Gonzalez Juan B. Sancho de Salas 《Journal of Geometry and Physics》2003,44(4):595-622
We consider a smooth one-parameter family of four-dimensional manifolds X,≥0, each one endowed with a covariant metric g. It is assumed that g is a Lorentz metric for each >0, i.e., the signature of g is (+,−,−,−) for >0, while the limit metric g0 on X0 is assumed to be degenerated of rank 1, i.e., the signature of g0 is (+,0,0,0). We characterize when the limit manifold X0 inherits the geometric structure of a Newtonian gravitation. The limit manifold X0 is a Newtonian gravitation if and only if there exist the limits of the Levi-Civita connection , the curvature operator
and the contravariant Einstein tensor G2 as →0. Moreover, the existence of these limits is characterized in terms of the Taylor expansion of the family {g} with respect to the parameter . 相似文献
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利用传统的固相反应法在还原性气氛1200 ℃下分别制备出不同Nb掺杂量的Ti1-xNbxO2-δ陶瓷样品.样品的粉末X射线衍射(XRD)结果显示:Nb掺杂量x较低时样品为多相混合,当Nb掺杂量x>0.02时样品为单一的四方相金红石型结构.在室温到900 K的测试温区,测试了单相样品(x=0.02,0.03,0.04)的电导率、Seebeck系数和热导率.测试
关键词:
氧化钛陶瓷
热电性能
氧空位 相似文献
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The evolution equation for the nonsinglet distribution of partons is solved in the leading order of perturbative QCD. It is shown that an exact analytic solution to the evolution equations can be found in the quasielastic limit. The Q 2 evolution of the structure function for x → 1 is in good agreement with experimental data. 相似文献
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L. A. Kornienko E. F. Dudarev V. E. Panin V. I. Sarrak V. A. Brovkov 《Russian Physics Journal》1975,18(3):327-331
The influences of alloy composition have been examined for the temperature dependence of the macroscopic elastic limit σ″ over the range 77–293?K for polycrystalline Fe-Si solid solutions. Various factors contribute to the temperature dependence of σ″, and it is found that the variation on alloying is determined by the interaction between dislocations and dissolved atoms (substitutional and interstitial), as well as by the resistance to dislocation motion due to the short-range order; furthermore, the effect on the temperature dependence of the limit on alloying iron with silicon is determined by the short-range forces between the dislocations in the silicon atoms. Interstitial impurities tend to segregate at grain boundaries, which weakens the temperature dependence of the limit. 相似文献
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Nitrogen ions were implanted into SiC ceramics by using ion implantation technology (N+-SiC). The surface structure and chemical bonds of N+-SiC ceramics were determined by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), and their nanohardness was measured by nanoindenter. The friction and wear properties of the N+-SiC/SiC tribo-pairs were investigated and compared with those of SiC/SiC tribo-pairs in water using ball-on-disk tribo-meters. The wear tracks on the N+-SiC ceramics were observed by non-contact surface profilometer and scanning electron microscope (SEM) and their wear volumes were determined by non-contact surface profilometer. The results show that the N+-SiC ceramics were mainly composed of SiC and SiCN phase and SiN, CC, CN and CN bonds were formed in the implantation layer. The highest hardness of 22.3 GPa was obtained as the N+-SiC ceramics implanted at 50 keV and 1 × 1017 ions/cm2. With an increase in nitrogen ion fluence, the running-in period of N+-SiC/SiC tribo-pairs decreased, and the mean stable friction coefficient decreased from 0.049 to 0.024. The N+-SiC ceramics implanted at 50 keV and 5 × 1017 ions/cm2 exhibited the excellent tribological properties in water. In comparison of SiC/SiC ceramic tribo-pairs, the lower friction coefficient and lower wear rate for the N+-SiC/SiC tribo-pairs were acquired. 相似文献
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Determination of the elastic limit in ferromagnetic materials using the mechanical barkhausen effect
Yu. N. Kharitonov 《Russian Physics Journal》1967,10(12):71-73
Conclusions The proposed method for finding the elastic limit in annealed ferromagnetic samples may be useful for investigating this and short samples, where other methods are inconvenient. In principle, it can also be used to find
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in unannealed samples, but in this case the mechanical Barkhausen effect is very weak, and the accuracy of measurement decreases. 相似文献
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We consider elastic dipoles in several two-dimensional geometries. Using Cauchy integral techniques and the image method, the state of elastic equilibrium under different boundary conditions can be determined. The results are used to find the ground state of systems of anisotropic dipoles via the simulated annealing method. Only in the case of fixed boundaries the ordering depends on the boundary condition. 相似文献
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U. Götz F. Rösel D. Trautmann H. Jochim 《Zeitschrift für Physik A Hadrons and Nuclei》1976,278(2):139-143
It is demonstrated that the Mott-Schwinger interaction must be taken into account when analyses of polarisation measurements in proton scattering at energies below the Coulomb barrier are to be performed with high accuracy. A treatment of the effect is worked out in perturbation theory, and the reliability of the method is demonstrated. It is shown how the resulting badly converging series for the “Mott-Schwinger amplitude” can conveniently be summed by means of Padé-approximation. Numerical results are presented for several representative cases. 相似文献
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A statistical approach including direct correlation functions is applied to study the influence of the surface confining the
nematic liquid phase on the Franck elastic coefficients. Specific calculations are made for a model system composed of ellipsoidal
molecules interacting by means of the Gay-Berne potential near the interacting surface.
Fiz. Tverd. Tela (St. Petersburg) 40, 1356–1359 (July 1998) 相似文献
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在孔穴塌缩模型的基础上,建立了计算泡沫态硅橡胶在不同初始密度下的冲击绝热线参数的理论方法。获得了泡沫态硅橡胶在两种不同初始密度下(0.52 g/cm3和0.92 g/cm3)的冲击绝热线,并与已有的实验数据进行对比分析。结果表明,建立的理论方法对于泡沫态硅橡胶的冲击绝热线计算是适用的。 相似文献