In-flight and collisional dissipation as a mechanism to suppress Fermi acceleration in a breathing Lorentz gas

Some dynamical properties for a time dependent Lorentz gas considering both the dissipative and non dissipative dynamics are studied. The model is described by using a four-dimensional nonlinear mapping. For the conservative dynamics, scaling laws are obtained for the behavior of the average velocity for an ensemble of non interacting particles and the unlimited energy growth is confirmed. For the dissipative case, four different kinds of damping forces are considered namely: (i) restitution coefficient which makes the particle experiences a loss of energy upon collisions; and in-flight dissipation given by (ii) F=-ηV(2); (iii) F=-ηV(μ) with μ≠1 and μ≠2 and; (iv) F=-ηV, where η is the dissipation parameter. Extensive numerical simulations were made and our results confirm that the unlimited energy growth, observed for the conservative dynamics, is suppressed for the dissipative case. The behaviour of the average velocity is described using scaling arguments and classes of universalities are defined.     

Transition from direct tunneling to field emission in metal-molecule-metal junctions

Current-voltage measurements of metal-molecule-metal junctions formed from pi-conjugated thiols exhibit an inflection point on a plot of ln(I/V(2)) vs 1/V, consistent with a change in transport mechanism from direct tunneling to field emission. The transition voltage was found to scale linearly with the offset in energy between the Au Fermi level and the highest occupied molecular orbital as determined by ultraviolet photoelectron spectroscopy. Asymmetric voltage drops at the two metal-molecule interfaces cause the transition voltage to be dependent on bias polarity.     

Nanometer scale electronic reconstruction at the interface between LaVO3 and LaVO4

Electrons at interfaces, driven to minimize their free energy, are distributed differently than in bulk. This can be dramatic at interfaces involving heterovalent compounds. Here we profile an abrupt interface between V 3d2 LaVO3 and V 3d0 LaVO4 using electron energy loss spectroscopy. Although no bulk phase of LaVOx with a V 3d1 configuration exists, we find a nanometer-wide region of V 3d1 at the LaVO3/LaVO4 interface, rather than a mixture of V 3d0 and V 3d2. The two-dimensional sheet of 3d1 electrons is a prototypical electronic reconstruction at an interface between competing ground states.     

Second-order correction to the positronium ground-state energy in ionic crystals

Upper and lower bounds on the second-order correction to the positronium ground-state energy due to the influence of the crystalline field in an ionic crystal are obtained, and the corresponding formulas are derived. The approximation adopted in the numerical calculations is the model of a point-ion potential. It is shown that neglecting the contribution of states in the continuous energy spectrum of the electron—positron pair to the correction yields an unsatisfactory upper bound. V. I. Lenin Moscow State Pedagogical University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 37–41, April, 1998.     

A study of capacitance-voltage characteristics of lead zirconate titanate ferroelectric thin films and their usage to investigate polarization and coercive field

Capacitance-voltage (C-V) characteristics of lead zirconate titanate (PZT) thin films with a thickness of 130 nm were measured between 300 and 533 K. The transition between ferroelectric and paraelectric phases was revealed to be of second order in our case, with a Curie temperature at around 450 K. A linear relationship was found between the measured capacitance and the inverse square root of the applied voltage. It was shown that such a relationship could be fitted well by a universal expression of C/A = k(V+V(0))(-1/2) and that this expression could be derived by expanding the Landau-Devonshire free energy at an effective equilibrium position of the Ti/Zr ion in a PZT unit cell. By using the derived equations in this work, the free energy parameters for an individual material can be obtained solely from the corresponding C-V data, and the temperature dependences of both remnant polarization and coercive voltage are shown to be in quantitative agreement with the experimental data.     

First-Principles Investigation on the Fully Compensated Ferrimagnetic Behavior in Ti_2NbSb and TiZrNbSb

The electronic structures of Ti_2NbSb with Hg_2CuTi structure and TiZrNbSb with LiMgPdSn structure are investigated using first-principles calculations.The results indicate that Ti_2NbSb is a fully compensated ferrimagnetic spin-gapless semiconductor with an energy gap of 0.13 e V,and TiZrNbSb is a half-metallic fully compensated ferrimagnet with a half-metallic gap of 0.17 e V.For Ti_2NbSb,the total energy of the Hg_2CuTi structure is0.62 e V/f.u.higher than that of the L2_(1) structure,which is the ground state,and for TiZrNbSb,the total energy of the structure considered in this work is only 0.15 e V/f.u.larger than that of the ground state.Thus both of them may be good candidates for spintronic applications.     

Effects of Zr and V additions on the stability and migration of He in bcc W: A first-principles study

The effects of zirconium (Zr) and vanadium (V) on the dissolution, diffusion and trapping behaviors of helium (He) in body-centered cubic (bcc) tungsten (W) have been investigated using first-principles simulations. We found that Zr and V atoms usually prefer to disperse into W-rich region rather than aggregate in W host lattice. Energetically, the relatively stable position for an interstitial He remains the tetrahedral interstitial site in W with the presence of Zr/V atom. The solution energy of the He atom is reduced because of the attractive interaction between He and Zr/V atom. Compared to W with Zr, the stronger attractive interaction between V and He results in the lower He solution energy in W with V. Kinetically, the He atom diffusion to Zr/V has a lower energy barrier than that of He diffusion to W along the optimal diffusion path TIS–TIS. In addition, the existing Zr/V atom improves the ability of Zr/V-Vacancy complex to capture He atom. These results provide incontrovertible evidence that the existing Zr/V atom has great influence on the behavior of He atom in bulk W.     

High resolution EELS of Cu-V oxides: application to batteries materials

Although widely used, the most promising Li-based technologies still need to seek new materials concepts to satisfy the increasing demands for energy storage worldwide. We report a layered electrode material, Cu(2.33)V4O11, for which the valency of copper, vanadium and thus indirectly the oxygen stoichiometry need to be investigated during the electrochemical cycle. High-resolution electron energy loss spectroscopy (HREELS) allows us to perform these measurements at the nanometer scale.     

Radiative correction to the energy of a fermion in an external gauge field

The first radiative correction in g² to the energy of the ground state of a fermion in a constant uniform gauge (for the SU(2) group) field of magnetic type is calculated. The expression obtained contains an indication of instability of the ground state.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 102–104, November, 1982.The authors are grateful to V. R. Khalilov for a fruitful discussion of the work.     

A new method of calculating the spectrum and the self-consistent field of negative ions

A new method is suggested for negative ion calculations, based on perturbation theory with a model zeroth approximation and a polarization potential formalism. The binding energy of an electron in an Na^– ion is calculated as a test, and is found to agree with experiment.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 41–46, September, 1990.In conclusion, the author is grateful to E. P. Ivanova for her interest, to V. V. Flambaum and V. K. Ivanov for supplying preprints of [8, 9], and to V. V. Filatov for help in the numerical calculations.     

周期永磁环爆磁压缩发生器

首次提出了利用周期永磁环做初始能源的螺旋型爆磁压缩发生器,该结构由4节永磁环正反排到组成。阐述了这种周期永磁环爆磁压缩发生器的结构及其特点,并利用等效电路模型分析了轴线起爆周期永磁环爆磁压缩发生器的磁通变化规律和爆磁压缩过程,得到了基本的电流变化关系。 分析及数值计算结果表明：这种周期永磁环爆磁压缩发生器能够实现电流放大,在磁化电流为0.13 MA,磁化回路负载电感为1.0 μH条件下,最终输出电流可达0.16 MA。周期永磁环可以作为爆磁压缩发生器的初始能源,这种概念设计值得进行进一步的实验探索。     

Experimental studies of THGEM in different Ar/CO_2 mixtures

In this paper, the performance of a type of domestic THGEM (THick Gaseous Electron Multiplier) working in Ar/CO₂ mixtures is reported in detail. This kind of single THGEM can provide a gain range from 100 to 1000, which is very suitable for application in neutron detection. In order to study its basic characteristics as a reference for the development of a THGEM based neutron detector, the counting rate plateau, the energy resolution and the gain of the THGEM have been measured in different Ar/CO₂ mixtures with a variety of electrical fields. For the Ar/CO₂(90%/10%) gas mixture, a wide counting rate plateau is achieved from 720 V to 770 V, with a plateau slope of 2.4%/100 V, and an excellent energy resolution of about 22% is obtained at the 5.9 keV full energy peak of the ⁵⁵Fe X-ray source.     

Study of the (d, α) reaction applied to 50Cr and 52Cr

The reactions ⁵⁰Cr(d, α)⁴⁸V and ⁵²Cr(d, α)⁵⁰V have been carried out at an incident deuteron energy of 15 MeV to investigate the structure of the low-lying levels of ⁴⁸V and ⁵⁰V in the light of shell model expectations. Excitation energies and angular distributions have been measured for states up to about 1.5 MeV. For all resolved and strongly excited levels angular momentum transfers could be assigned by comparison with DWBA calculations. For ⁵⁰V spectroscopic factors have been extracted in relative units assuming pure configurations for the transferred pair of nucleons. The results indicate the existence of seniority and configuration mixing in the level structure of the ⁴⁸V and ⁵⁰V isotopes. In both reactions some transitions show characteristic deviations from the direct reaction mechanism. These deviations cannot be reproduced by the DWBA calculations.     

周期永磁环爆磁压缩发生器

 首次提出了利用周期永磁环做初始能源的螺旋型爆磁压缩发生器,该结构由4节永磁环正反排到组成。阐述了这种周期永磁环爆磁压缩发生器的结构及其特点,并利用等效电路模型分析了轴线起爆周期永磁环爆磁压缩发生器的磁通变化规律和爆磁压缩过程,得到了基本的电流变化关系。 分析及数值计算结果表明：这种周期永磁环爆磁压缩发生器能够实现电流放大,在磁化电流为0.13 MA,磁化回路负载电感为1.0 μH条件下,最终输出电流可达0.16 MA。周期永磁环可以作为爆磁压缩发生器的初始能源,这种概念设计值得进行进一步的实验探索。     

Luminescence yield of ruby with electron excitation

The emission spectra of ruby on electron excitation are investigated for various temperatures and current densities. The luminescence yield of ruby on excitation by an electron beam is determined. The effectiveness of excitation energy transfer from the lattice to the chromium ions is evaluated. The possibility of generation at the depth of electron beam penetration into the crystal is discussed.In conclusion, the authors wish to express their thanks to V. L. Levshin for taking an interest in their work, to V. N. Smorchkov for various suggestions and discussion of the results, and to A. V. Lavrov, V. P. Prokhorov, and Yu. V. Khrushchev for valuable assistance.     

Analysis of renewable energy sources and electric vehicle penetration into energy systems predominantly based on lignite

We consider an integration of renewable energy into transport and electricity sectors through vehicle to grid (V2G) technologies for an energy system that is predominantly based on lignite. The national energy system of Macedonia is modeled using EnergyPLAN which integrates energy for electricity, transport and heat, and includes hourly fluctuations in human needs and the environment. We show that electric-vehicles can provide the necessary storage enabling a fully renewable energy profile for Macedonia that can match the country’s growing demand for energy. Furthermore, a large penetration of electric vehicles leads to a dramatic reduction of 47% of small particles and other air pollutants generated by car traffic in 2050.     

Determination of the hole lifetime from photoemission: Ti 3d states in TiTe2

The electron hole spectral width Gamma(h) of Ti 3d states in layered TiTe2 and the inverse lifetime V(i) of the photoelectron final states are determined from experiment within the one-step theory of photoemission. The condition for the possibility of separating the effects of Gamma(h) and V(i) is a strongly non-free-electron character of the final states. The resulting drastic changes of the line shape with photon energy are experimentally observed and explained by an ab initio theory. A nonmonotonic dependence of V(i) on the final-state energy is observed; it is shown to reveal the real space structure of the complex electron self-energy.     

Application of group symmetry to spectral problems of quantum mechanics

On the basis of a representation of the SU(2) group, a multiparameter potential of the anharmonic oscillator is constructed. A method of finding its solutions is indicated, and in particular cases, explicit expressions for the wave function and the corresponding energy values are obtained.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No.5, pp. 90–94, May, 1988.In conclusion, the authors thank A. V. Borisov and V. Ch. Zhukovskii for useful discussion of some results of this paper.     

Structure of V thin films on Al(100) using XPD,LEED, and LEIS

We have used X-ray photoelectron diffraction (XPD), low energy electron diffraction (LEED), and low energy ion scattering (LEIS) to determine the atomic structure of V thin films grown on the Al(100) single crystal surface. For V film thicknesses ranging from 0.75 ML–7 ML, the LEED patterns show no significant changes from the p(1 × 1) symmetry of a clean Al(100) surface, other than becoming more diffuse for higher V coverage. XPD and LEIS spectra indicate that during the initial deposition (1–3 ML) V atoms diffuse into the Al lattice, and tend to accumulate at the surface during subsequent deposition. Strain associated with the lattice mismatch for V and Al is likely relieved by the formation of a surface alloy during the first few ML's of V deposition. For 7 ML V coverage, XPD and LEED showed that an ordered V structure is stabilized on the Al(100) surface. Due to the close resemblance of the V and Al XPD polar scans, we conclude that V and Al are occupying similar lattice sites in tetragonally distorted bcc lattice, although the specific lattice location of the V and Al atoms is not clear.