A study of the optical absorption and the hyperfine constant of the F-centre in alkali halides by means of the multiple scattering Xα method

The F-centre in several alkali halides has been investigated by means of the multiple scattering Xα method. The calculated values of the first absorption peak and the hyperfine splitting constant are compared to experimental results and other theoretical work. It is found that the results agree quite well with experimental values.     

Determination of equivalent salt deposit density using wind velocity for a contaminated insulator

This paper illustrates a new analytical model for determining equivalent salt deposit density (ESDD) on contaminated insulators using wind velocity. The analytical model is derived using the dimensional analysis technique. The values of ESDD from the analytical model are calculated using different values of wind velocity. These results are compared with the experimental results obtained from sites. The analytical results are also compared with the polynomial model output obtained via least-squares analysis of experimental data. It is found that the results obtained by the analytical model are quite consistent with the experimental results for different range of wind velocity.     

Experimental determination of the effective surface energy density in dynamic problems of fracture mechanics

Computational and experimental methods for determining the effective surface energy density under the dynamic loading conditions are proposed. The results are presented for two grades of steel and titanium alloy VT-6S in the submicrosecond range of the loading pulse duration. The resultant values of the effective surface energy density are compared with the results obtained by other authors.     

RC串联电路相移测量方法的研究

利用电压法、李萨茹图形法和双轨迹法分别测量了RC串联电路的相移,并将实验值与理论值进行了比较。研究表明,在所选择的频率波段内,这三种方法测量的实验值与理论值符合的很好,具有高精度、测量装置简单、操作方便等优点。通过对以上三种测量方法的研究,能够让学生从直观上更深入地理解对RC串联电路的特性。     

Analysis of the photoelastic effect in ionic crystals

An analysis of the photoelastic effect in ionic crystals has been presented within the framework of Clausius-Mossotti theory of the dielectric constant. The values of the strain derivative of the electronic dielectric constant have been calculated in alkali halides and MgO crystals by taking into account the variation of electronic polarizabilities with compressive stress. The results obtained are found closer to the experimental values. The photoelastic behaviour of MgO crystal is predicted to be of opposite nature to that of alkali halides, in conformity with the experimental observations.     

Effect of flow on the apparent transverse relaxation time in a microfluidic nuclear magnetic resonance chip

The detection of samples in a microfluidic nuclear magnetic resonance chip is generally performed under flow condition. To study the effect of sample flow on the apparent transverse relaxation time in a microfluidic nuclear magnetic resonance chip, theoretical calculations were performed on three microfluidic samples (including deionized water, absolute ethanol, and copper sulfate pentahydrate) for flow velocities in the range 1.7–25?mm/s. A microfluidic nuclear magnetic resonance device with a low cost microfluidic solenoid coil was fabricated to verify the theoretical calculations by experiments. The results show that the apparent transverse relaxation time of the sample is a monoexponential decay with respect to flow velocity. In addition, it was found that the experimental values and the theoretical values of the apparent transverse relaxation time are identical when the samples are prepolarized completely; but for the samples that are not prepolarized completely, all the experimental values are smaller than the theoretical values and their difference increases with the flow velocity of the sample. After further study, it was discovered that the relative error between the experimental values and the theoretical values is a monoexponential decay to the level of the sample to be prepolarized. This discovery is very useful, because it can be used to modify the theoretical calculation model of the apparent transverse relaxation time for the samples that are prepolarized incompletely, as well as improve the application of microfluidics on nuclear magnetic resonance.     

Carbon and oxygen 1s ionization energies of the carbonyl group of ketones

Carbon and oxygen 1s ionization energies for the carbonyl group have been measured in the gas phase for 18 ketones. The shifts in these measured ionization energies, together with similar data for aldehydes from the literature, are compared with the predictions of electronic structure calculations based on the equivalent-cores model. It is found that the ab initio results using the 6-31G^* basis set correlate linearly with the experimental results, but the slopes of the correlations are not 1. For oxygen the predicted shifts are 0.9 times the observed values and for carbon they are 1.3 times those observed. Oxygen 1s ionization energy shifts calculated using the semi-empirical AM1 method also correlate well with the experimental values, but with a slope of only 0.54. For the carbon 1s energies, the predictions of the semi-empirical calculations correlate only with the data for the ketones (slope of 0.63) and fail noticeably for the aldehydes.     

Calculation of Recombination and Ionization Coefficients in Argon

Various methods for calculating electron-ion recombination and ionization coefficients for argon (α and S) have been developed in the past. For given values of electron temperature and electron density, a large dispersion exists between the different results due to a great number of parameters. We have developed the method based on the collisional-radiative model to calculate α and S for limited conditions (atmospheric pressure; strong resonance radiation absorption) in order to obtain realistic values applicable in real cases such as arc plasmas. Influences of resonance radiation absorption and atom-atom collisions have been studied. The collisional-radiative recombination coefficient has been compared with results obtained by other calculation methods: the best agreement occurs with the “bottleneck” model for high values of electron density and temperature. Finally the comparison with available experimental results shows a good agreement between our computed values and experimental values when experimental and theoretical conditions are analogous.     

Determination of static dipole polarizabilities of Yb atom

We determine the static values of the scalar and tensor dipole polarizabilities of the ground, 6s6p~3P_0~o, and 6s6p~3P_1~o states of the Yb atom. These results can be useful in many experiments undertaken using this atom. We employed a combined configuration interaction(CI) method and a second-order many-body perturbation theory(MBPT) to evaluate energies and electric dipole(E1) matrix elements of many low-lying excited states of the above atom. These values are compared with the other available theoretical calculations and experimental values. By combining these E1 matrix elements with the experimental excitation energies, we estimate the dominant valence correlation contributions to the dipole polarizabilities of the above states. The core contribution is obtained from the finite field approach. We also compare these values with the other theoretical results as there are no precise experimental values that are available for these properties.     

Molecular dynamics study for the melting curve of MgO at high pressure

Shell-model molecular dynamics method is used to study the melting temperatures of MgO at elevated temperatures and high pressures using interaction potentials. Equations of state for MgO simulated by molecular dynamics are in good agreement with available experimental data. The pressure dependence of the melting curve of MgO has been calculated. The surface melting and superheating are considered in the correction of experimental data and the calculated values, respectively. The results of corrections are compared with those of previous work. The corrected melting temperature of MgO is consistent with corrected experimental measurements. The melting temperature of MgO up to 140GPa is calculated.     

A computational approach on the study of Franklin rod height impact on striking distance using a stochastic model

In the present paper, a new stochastic model is used for the simulation of an experimental procedure concerning the study of Franklin rod height impact on striking distance. The results obtained from the application of the stochastic model, which is developed for the simulation of lightning and breakdown in long air gaps, are compared with the experimental results obtained in the High Voltage Laboratory. Real values for voltage, space and time were introduced in the model. The comparison of the simulation with the experimental results, show that the stochastic model has given a good approximation in the case of large distances between the active electrode and the ground.     

Influence of Effective Tensor Forces on the Fission Barriers of Nuclei in the Uranium Region

The influence of effective tensor forces on the fission barriers of nuclei in the uranium region has been studied. A modified Fayans energy density functional (EDF) FaNDF⁰-a, which differs from the initial energy density functional FaNDF⁰ in the inclusion of strong effective tensor interaction, has been proposed. For the ²³⁶U and ²³⁸U isotopes, this results in a significant, about 1 MeV, reduction of the first barrier, approaching the values to the known experimental values. However, a noticeable, about the same order of magnitude, difference from these experimental values remains. Possible reasons for this remaining difference are discussed.     

Macroscopic theory of the electron work function in solids

The approach is based on the dielectric formalism theory. The relations for calculation of the electron work function in solids – metals, semiconductors and dielectrics, were obtained. The calculated results are in an agreement with experimental ones. This approach can be used for computation of work function values of numerous materials.     

Experimental and numerical study of swirling subcooled flow boiling of water in a vertical annulus

In this paper, the effect of making swirling flow inside an annulus on the subcooled boiling heat transfer has been studied and discussed both experimentally and numerically. The Eulerian-Eulerian model and control volume technique have been used for numerical modeling of the problem. The experimental results show that the critical heat flux values are enhanced by making swirling flow. The experimental and numerical results also indicate that by making swirling flow inside the annulus, the subcooled boiling heat transfer coefficients are increased. Moreover, the experimental and numerical values of the boiling heat transfer coefficients show good agreement with each other.     

α-decay half-lives of superheavy nuclei and general predictions

The generalized liquid drop model (GLDM) and the cluster model have been employed to calculate the α-decay half-lives of superheavy nuclei (SHN) using the experimental α-decay Q values. The results of the cluster model are slightly poorer than those from the GLDM if experimental Q values are used. The prediction powers of these two models with theoretical Q values from Audi et al. (Qaudi) and Muntian et al. (QM) have been tested to find that the cluster model with Qaudi and QM could provide reliable results for Z>112 but the GLDM with Qaudi for Z≤112. The half-lives of some still unknown nuclei are predicted by these two models and these results may be useful for future experimental assignment and identification.     

Absolute measurements of rayleigh factor in some pure organic liquids

An absolute light scattering determination method is described. Experimental results are presented for seven organic liquids at 23°C for two wavelengths 4416 Å and 6328 Å. The experimental data are compared with those calculated by theoretical formulas using experimental values of Landau-Placzek ratios and adiabatic compressibilities. A good agreement between experimental and calculated data confirms the validity of “low” values of light scattering factor.     

On the causes of negative source impedance in the measurement of intake and exhaust noise sources

In order to evaluate the acoustic field within a duct system some knowledge is required about the acoustic source, which is characterized by frequency-dependent values of both strength and impedance. However, in using various experimental techniques for various types of source to obtain these values, negative real parts of the source impedance have been measured. Negative source resistance is physically implausible. In some instances, one measurement method gives positive values of source resistance where another gives negative values. This paper reviews the possible causes of the problem, with reference to experimental and theoretical results, in an attempt to clarify the issue. Various possible origins of a negative source resistance have been investigated. It is noted that, for the time being, the violation of the assumption of a time-invariant source and the defect in the inherent algorithm of the load method are the most probable origins of the negative source resistance.     

Determination of low-energy parameters of neutron-proton scattering on the basis of modern experimental data from partial-wave analyses

The triplet and singlet low-energy parameters in the effective-range expansion for neutron-proton scattering are determined by using the latest experimental data on respective phase shifts from the SAID nucleon-nucleon database. The results differ markedly from the analogous parameters obtained on the basis of the phase shifts of the Nijmegen group and contradict the parameter values that are presently used as experimental ones. The values found with the aid of the phase shifts from the SAID nucleon-nucleon database for the total cross section for the scattering of zero-energy neutrons by protons, σ ₀ = 20.426 b, and the neutron-proton coherent scattering length, f = ?3.755 fm, agree perfectly with experimental cross-section values obtained by Houk, σ ₀ = 20.436 ± 0.023 b, and experimental scattering-length values obtained by Houk and Wilson, f = ?3.756 ± 0.009 fm, but they contradict cross-section values of σ ₀ = 20.491 ± 0.014 b according to Dilg and coherent-scattering-length values of f = ?3.7409 ± 0.0011 fm according to Koester and Nistler.     

Collisional-Radiative Recombination in Argon Plasmas

On the basis of the realistic argon atom model consisting of 65 discrete effective levels numerical results for the collisional-radiative volume recombination, ionization and decay coefficients are obtained. The computations are carried out without any approximations of integral functions. The presented comparison of theoretical and experimental results for the decay coefficient shows that the values calculated by us are in much better agreement with experimental values than those obtained by Desai and Corcoran on the assumption that the argon atom is hydrogen-like.