A Green-Naghdi Model in a 2D Problem of a Mode I Crack in an Isotropic Thermoelastic Plate

In this article, the generalized thermoelastic theory under Green and Naghdi models are used to study the thermoelastic interaction in an isotropic material containing a finite crack inside the material. The crack boundary is due to a prescribed temperature and stress distribution. Based on the Green-Naghdi type II and type III models, the formulation is applied to generalized thermoelasticity with an appropriate choice of parameters. Numerical solutions of the displacement components, temperature, and stress components are obtained using the finite element method. The results have been verified numerically and are represented graphically. Comparisons were made with expected results from Green and Naghdi model of type III and Green and Naghdi model of type II.     

溴化镧探测器时间分辨率的测量

用60 Coγ源和搭建的电子学测量系统,测量了自制塑料闪烁探测器、3英寸的溴化镧探测器和电子学系统的时间分辨率,得到了圣戈班公司生产的3英寸溴化镧探测器的时间分辨率为(283.2±0.9)ps.     

Spatial Moments for the Nonstationary One-Velocity Problem of Transport Theory with Isotropic Scattering. 2. Plane Instantaneous Source

The spatial distribution of the density of particles emitted by a plane infinite isotropic source with a unit surface particle density is reconstructed for the nonstationary one-velocity problem of transport theory by the method of polynomial expansions with the use of Legendre and Hermite polynomials. The diffusion approximation is examined and the boundaries of the spatiotemporal region in which this approximation is valid are estimated.     

Time Evolution in Macroscopic Systems. I. Equations of Motion

Time evolution of macroscopic systems is re-examined primarily through further analysis and extension of the equation of motion for the density matrix (t). Because contains both classical and quantum-mechanical probabilities it is necessary to account for changes in both in the presence of external influences, yet standard treatments tend to neglect the former. A model of time-dependent classical probabilities is presented to illustrate the required type of extension to the conventional time-evolution equation, and it is shown that such an extension is already contained in the definition of the density matrix.     

Isotropic Space with Discrete Gravitational-Field Sources. On the Theory of a Nonhomogeneous Isotropic Universe

Existing cosmological theories are based on Einstein's law of gravitation (7). In this equation the average is taken only in the right-hand side by a substitution of the energy momentum tensor corresponding to uniform and continuous distribution of matter. In this paper a new cosmological equation (48), which is more correct from the physical and mathematical point of view, is obtained by space-time averaging of all the terms of Eq. (7) and taking into account the fluctuations of the gravitational field due to nonuniformities in the distribution of matter. An estimate of these fluctuations within the framework of Newton's approximation leads to the cosmological equations (51), (52) and (53) for flat space and positive and negative curvature. The solutions of these equations, in distinction from all the variants of Friedman's theory, do not have a singular point for some initial moment of time with an infinitely large density of matter. However, this result follows when the relations obtained are extrapolated beyond the range of their applicability, and therefore final conclusions can be made on the basis of the solutions of the new cosmological equations (48) when we go beyond the Newtonian approximation.     

时间相关单光子计数光谱方法：Ⅰ.时间统计特性

本文用随机点过程理论分析了微弱光场作用下光子检测计光电子时间统计特性。讨论了时间相关单光子计数理想工作条件，简述了实际ＴＣＳＰＣ系统若干不理想因素。     

The Problem of Time in Quantum Cosmology

It is shown that the incorporation of the Logunov coupling equations results in a nonzero Hamiltonian, which allows the problem of time of quantum gravitation theory to be solved outside the framework of traditional approaches.     

Time dependent Thomas Fermi approach to atomic collisions I.

A numerical solution of the time dependent Thomas-Fermi equations introduced by Bloch is presented for the case of the scattering of a proton from an argon atom. We discuss in detail the resulting time development of the many electron density distribution and velocity fields for proton bombarding energies of 0.4, 0.9 and 2.5 MeV. Possible foundations of the model, in particular the relation to the time dependent Hartree-Fock method are indicated.     

Application of the Block Element Method in a Certain Boundary Value Problem of Academician I.I. Vorovich

Doklady Physics - By the example of the boundary value problems—the vector problem (set of differential equations) and the scalar problem (single equation)—the features of their...     

A model of modulated diffusion. I. Analytical results

We introduce an integrable isochronous system and perturb its frequency by an external-deterministic or purely random-noise. Under the perturbation the action variable evolves in time: the corresponding diffusion coefficient is exactly computed and its dependence on the magnitude of the perturbation is carefully investigated. Different behaviors are found and justified: the quasilinear approximation, the superlinear regime, and the ballistic motion.     

Yielding behavior of glassy polymers. I. Free-volume model

Rigid, glassy polymers show a diversity of tensile behavior-ranging from apparently brittle to ductile. To delineate some of the factors that control the toughness or impact resistance of these polymers, the yielding behavior of poly (methyl methacrylate) (PMMA) was studied. Results of other workers have shown that the cold flow exhibited by many glassy polymers can be explained qualitatively by a free-volume model. The treatment assumes that molecular flow is permitted when the free volume increase, resulting from the dilatational component of the applied stress, is sufficient to bring the total free volume to that characteristic of the polymer liquid. The present study refines this approach by introducing an “effective temperature,” defined as that hypothetical temperature at which the glass would have an equilibrium free volume equal to the total free volume of the nonequilibrium glass at temperature T. Equations are derived which more satisfactorily describe the temperature and strain-rate dependences of the tensile yield strain of PMMA glass from -10° to 90°C at rates between 0.015 and 120%/sec.     

Mean lifetimes of excited levels of Ar II. I. Time correlation measurements

Mean Lifetimes of excited levels of Ar II have been measured using the method of time-correlated photons in cascade. The following results were obtained: for 4p⁴S^°_{$\text{3}\text{2}$}, τ = 7·2±0·3ns; for 4p′²F^°_{$\text{7}\text{2}$}, τ = 8·8±0·2 ns; for 4p′²F^°_{$\text{5}\text{2}$}, τ = 8·0±0·2 ns. These results are compared with experimental and theoretical values.     

High resolution fourier transform spectroscopy using infrared synchrotron radiation: I. Instrumentation

A compact high resolution (.002 cm^–1) vacuum Fourier transform spectrometer for use with far infrared synchrotron radiation was constructed at the National Synchrotron Light Source at Brookhaven National Laboratory. The spectrometer may be operated using a gas cell of path length of 2 m and a He cooled bolometer with NEP of 10^–13. The pure rotational spectrum of Ammonia was used to test the spectrometer.     

Phase determination by wavelength-modulated diffraction. I. Centrosymmetric case

Wavelength-modulated diffraction was developed by Iwasaki, Yurugi & Yoshimura [Acta Cryst. (1999), A55, 864-870] as a method for phase determination, in which the intensity of Bragg reflections is recorded using radiation whose wavelength is changing continually over a range in the vicinity of the absorption edge of an atom in the crystal. Using a ferrocene derivative crystal (chemical formula C36H32O7Fe, space group P2(1)/a) with the Fe atoms chosen as anomalous scatterers, measurements were made of the intensity gradient dI/d lambda of the reflections with an imaging plate as a detector on a synchrotron radiation source at Ritsumeikan University. In the case of a centrosymmetric crystal, the phase of the structure factor could be derived by measuring only the sign of dI/d lambda at one wavelength in the range. Of 104 reflections measured, the correct phase was assigned to 101 reflections. A discussion is given on the errors involved and on the limits of application of the method.     

Corner transfer matrices of the eight-vertex model. II. The Ising model case

In a previous paper certain corner transfer matrices were defined. It was conjectured that for the zero-field, eight-vertex model these matrices have a very simple eigenvalue spectrum. In this paper these conjectures are verified for the case when the eight-vertex model reduces to two independent and identical square-lattice Ising models. The Onsager-Yang expression for the magnetization follows immediately.     

Isotropic and nematic phase N.M.R. spectra of tellurophen

In molecular beam experiments the preferred spatial orientation or polarization of the rotational angular momentum of reactively scattered molecules can be determined by deflection in an inhomogeneous electric field. The apparatus, experimental method, and analysis procedure are described and illustrated with data obtained for the K + HBr, Cs + HBr, and Cs + HI reactions. The experiments employ a new field design which eliminates the non-adiabatic change of quantization axis that handicapped a previous polarization study. A simple normalization procedure provides ‘reduced deflection profiles’ which are very insensitive to substantial variations in the experimental parameters, including the deflection field strength, beam position in the field, collimating slit widths, dipole moment, and distributions of rotational and translational energy. These reduced profiles yield 2 x> and 4 x>, the first two moments of the probability distribution of polarization, where x is the angle between the rotational angular momentum and the initial relative velocity vector. The experimental results indicate marked polarization, corresponding to 2 x> < 0·10, and agree well with theoretical moments calculated from a statistical phase-space treatment.     

High resolution spectroscopy of rydberg states in indium I

Two-photon laser spectroscopy in a dense indium vapour allowed to investigatenp ² P _{1/2, 3/2} states (n=27–35) for^{113, 115}In with a thermionic diode. Precise data on the fine structure splitting of these states and the isotope shift of the two photon transitions have been obtained. The fine structure splitting shows a hydrogenic behaviour. By using the result of our isotope shift measurement in combination with literature values, level isotope shifts with reference to the ionization limit are deduced and analysed with respect to the different contributions.