Study of field distribution,acoustical efficiency and harmonic generation for pseudo-interdigital surface-wave transducers by a finite-difference method

A pseudo-interdigital Rayleigh-wave transducer consists of an ordinary grating deposited on a quartz crystal surface and a counter electrode separated from the grating by a dielectric layer. The electric potential distribution from this transducer is calculated, in an isotropic approximation, under small piezoelectric coupling conditions, using a numerical relaxation technique (Frankel-Young's Method). Potential maps are given as the thickness e and permittivity ? of the dielectric layer are varied.A figure of merit is defined and its value as a function of e and ? are shown. Express ions for the spatial harmonic content are derived from the superficial potential distribution and compared to the case of interdigital combs (according to H. Engan). Some experiments on both types of transducer are given and the results obtained are consistent with theoretical calculations.     

Smectic islands in antiferroelectric nanofilms

Heterochiral islands, in which topological dipoles are oppositely directed, are observed in freestanding antiferroelectric (SmC _A ^*) films. The topological dipoles in films with a transverse electric polarization and a planar molecule orientation at island boundaries are coplanar with an electric field. The topological dipoles in films with a longitudinal polarization and a planar orientation at island boundaries are perpendicular to an electric field. For a radial director orientation at island boundaries, the topological dipoles in films with a longitudinal polarization are coplanar with a field. Changing the orientation of an electric field, we can control the position of a topological defect at an island boundary and the orientation of a topological dipole. Heterochiral islands can form dimers with an anomalously small interisland distance.     

Study of transitional odd-odd mass nuclei

The low lying high spin states in the transitional odd-odd mass nuclei are studied systematically in the framework of gamma deformed rotor model. The two odd particles, a proton and a neutron, are treated as the BCS quasi particles moving in a triaxially deformed field. The calculations are confined to smallβ-deformation which is typical of the transitional nuclei. Moreover, we consider only the case where two odd particles are in singlej-shells. Results for the excitation energy covering the various physical situations are presented as a function of theβ-deformation, the asymmetryγ, and the Fermi energiesλ _p andλ _n . Electromagnetic transitions and moments are also calculated. Certain features well known in the odd mass nuclei are shown to persist also in the odd-odd mass system. Trends in the level systematics and the electromagnetic properties are predicted for the case where both particles decouple or remain strongly coupled, and for the case where one decouples and the other couples strongly with the core. Measurements which are getting now available show encouraging agreement with the theoretical results.     

Possible applications of high temperature proton conductors (HTPCs)

First, the applications for HTPCs as suggested by Iwahara et al. are critically reviewed. In a second step the criteria for the application of HTPCs in SOFCs are outlined. 4 prominent HTPCs (doped Ba and Sr cerates, doped Ba and Sr zirconates and the mixed perovskite Ba₃Ca_1.18Nb_1.82O_9-δ) are critically examined for use as electrolytes in SOFCs. Generally, the following materials parameters are desirable: deviation from exact oxygen stoichiometry δ≈0.05; enthalpy of solution of water -ΔH_s≥1.5 eV; effective activation energy for proton transport E _H ^eff <=0.55 eV and proton transfer number t_H≈1. Third, the following applications are discussed: a) Introduction of hydrogen into a vacuum system; b) hydrogen charging of metals; c) a variable standard hydrogen leak; and d) a hydrogen partial pressure detector. Fourth, possible applications of HTPCs in tritium technology are presented. These compounds are potentially quite useful in glove-box atmosphere treatment, isotope separation, oxidation and reduction procedures and immobilization of tritium. Paper presented at the 3rd Euroconference on Soid State Ionics, Teulada, Sardinia, Italy     

Statistics of Stretching Fields in Experimental Fluid Flows Exhibiting Chaotic Advection

Stretching fields and their statistical properties are studied experimentally for four distinct two-dimensional time-periodic confined fluid flows exhibiting chaotic advection: a random vortex array for two different Reynolds numbers, a set of parallel shear layers, and a vortex lattice. The flows are driven electromagnetically, and they are studied by means of precise particle velocimetry. We find that for a given flow, the probability distributions of log S (where S is the local stretching in N cycles) can be nearly superimposed for different N when log S is rescaled using the geometrical mean of the stretching distribution. The rescaled stretching fields for a given flow at various N are highly correlated spatially when N is large. Finally, the scaled distributions for different flows are similar, though there are some differences connected to the degree of spatial symmetry and time-reversibility of the flows.     

<Emphasis Type="Italic">R</Emphasis> soliton in the Wess-Zumino model

The Wess-Zumino model involving a renormalizable interaction potential and possessing R symmetry is considered. It is shown that an R soliton, which is a nontopological soliton state, is present in this model. Characteristic properties of the R soliton are discussed. Problems associated with the stability of the R soliton are considered. The results obtained by numerically calculating the energy and the charge of the R soliton are presented for several values of the model parameters. The scalar field configurations in this supersymmetric model are characterized by the presence of fermionic zero modes. Expressions for the fermionic zero modes of the R soliton are obtained, and some of their properties are considered.     

Possible effect of solar activity on variation of the tree-rings of a 500 a platycladus orientalis at the Mausoleum of Emperor Huang

The variation of the tree-ring’s index of a platycladus orientalis at the Mausoleum of Emperor Huang and of a long series of sunspots relative number during AD1470–1974 are analyzed by using the wavelet power spectrum method, and their variation characters are also discussed. It is determined that the tree-ring’s variation has cycles of approximate 2–7, 11, 93 and 150 a. Two data series are used for analyzing sunspot relative number (SSN) variation. First, the analysis of the annual average SSN during AD1700–1974 proved that variation cycles are about 11, 50, and 93 a; then, the data during AD1465–1975 obtained from the decadal average SSN train over 7000 a reconstructed on the geomagnetic data is analyzed and its variation cycles are about 50, 90, and 160 a. Besides the tree-rings cycle of 2–7 a is commonly considered to be related to ENSO, while 11 a cycle is related to solar Schwabe cycle; in addition, it is possible that the cycles of 90 and150 a are likely to be related to solar Gleissberg cycle and Suess cycle. The correlations between them are possibly due to the effect of solar activity on the climate and additionally on the tree’s growth. Supported by the National Natural Science Foundation of China (Grant No. 19373017)     

Characteristic parameters of electromagnetic signals from a human heart system

The electromagnetic field of a human heart system is a bioelectromagnetic field. Electrocardiography (ECG) and magnetocardiography (MCG) are both carriers of electromagnetic information about the cardiac system,and they are nonstationary signals. In this study,ECG and MCG data from healthy subjects are acquired; the MCG data are captured using a high-T c radio frequency superconducting quantum interference device (HTc rf SQUIDs) and the QRS complexes in these data are analysed by the evolutionary spectrum analysis method. The results show that the quality factor Q and the central frequency f z of the QRS complex evolutionary spectrum are the characteristic parameters (CHPs) of ECG and MCG in the time-frequency domain. The confidence intervals of the mean values of the CHPs are estimated by the Student t distribution method in mathematical statistics. We believe that there are threshold ranges of the mean values of Q and f z for healthy subjects. We have postulated the following criterion: if the mean values of CHPs are in the proper ranges,the cardiac system is in a normal condition and it possesses the capability of homeostasis. In contrast,if the mean values of the CHPs do not lie in the proper ranges,the homeostasis of the cardiac system is lacking and some cardiac disease may follow. The results and procedure of MCG CHPs in the study afford a technological route for the application of HTc rf SQUIDs in cardiology.     

Raman spectra of GaAs-AlxGa1-xAs superlattices

Systematic theoretical studies of Raman spectra of GaAs-Al_xGa_1-xAs superlattices are presented. The electronic states are described by an envelope-function method and the phonon modes are described in a microscopic rigid-ion model. Both resonant and nonresonant Raman scattering processes are considered. For resonant Raman scattering, the effects of discrete exciton states plus the continuum and the valence-band mixing are included via a k-space sampling method. Both the Fröhlich and deformation-potential mechanisms for electron-phonon coupling are considered. These two mechanisms are responsible for principal features in the z(x, x)z̄ and z(x, y)z̄ geometries, respectively. We find that the effects of exciton continuum states are quite important and the resonant Raman spectra so obtained are in much better agreement with experiment compared to those without including the exciton continuum states.     

Betti Numbers of a Class of Barely <Emphasis Type="Italic">G</Emphasis><Subscript>2</Subscript> Manifolds

We calculate explicitly the Betti numbers of a class of barely G ₂ manifolds - that is, G ₂ manifolds that are realised as a product of a Calabi-Yau manifold and a circle, modulo an involution. The particular class which we consider are those spaces where the Calabi-Yau manifolds are complete intersections of hypersurfaces in products of complex projective spaces from which they inherit all their (1, 1)-cohomology and the involutions are free acting.     

Experiment determination of after-operating gas compositions in a transverse-flow CW high power CO2 laser

For a high-power CO₂ laser with a close-confined structure, the compositions and ratios of gas mixtures are changed due to electron impacts during the laser-operating period. As a result, the laser performance is gradually degraded, even to non-lasing output. In this paper, three different methods (a chemiluminescence, a titration analysis and a thermal conductivity measurement) are utilized to determine both the compositions and the ratios, according to different thermal and chemical characteristics of the gases. Corresponding experiments are implemented to a typical transverse-flow high-power CO₂ laser after a long-term discharge (around 15 h) with the output power decreased from an initial 3 kW to final 2 kW. There is evidence in the experiments to indicate that CO₂ decreases by 13.2% comparing with an initially optimal content. Also, the produced impurities are mostly CO and O₂ molecules with noticeable concentrations, while nitrogen–oxygen complexes are little in the gas mixtures.     

Can a fourth lepton family exist without its quark counterpart?

Solely within the minimal standard model, we show that it is possible to have a fourth lepton familywithout its quark counterpart provided the Higgs sector is strongly coupled and can accommodate Skyrmion solutions. The triangle and Witten anomalies of the fourth lepton family are cancelled by those of the “weak” Skyrmions if the latter are quantized as fermions. Thus a fourth quark family is not needed to cancel the anomalies of the new leptons. If indeed such a family is discovered in the near future bye ⁺ e ^? machines and if no Higgs boson nor new quarks of masses less than 1TeV are found, this intriguing scenario can be a very viable one. Arguments are presented to show that if such a scheme is realized, it also implies that the Higgs fields are composite.     

矩形波导与圆柱波导或圆柱谐振腔间的小孔耦合

本文讨论了三种不同系统的小孔耦合的近似解法:矩形波导与圆柱波导的同轴耦合,矩形波导中的TE₁₀型波与圆柱谐振腔中的TM₁₂₀型波间的耦合和矩形波导中的TE₁₀型波与圆柱波导中的TM_mn型波间的耦合。通过这几个问题的解法,我们希望读者可以看到处理复杂微波元件问题时所需的从物理概念出发的灵活应用已有方法的必要性。这里提供的几个公式有着广泛的应用范围而是在现有文献中探讨得不够的。这里介绍的方法可以应用到其他新的微波网络问题中去。     

Electroweak Processes in Few-Nucleon Systems

 After a brief introduction into the basic ingredients of electroweak theory as a spontaneously broken local, non-Abelian gauge symmetry, the general properties of the electromagnetic current and two-photon operators are discussed. In particular, the consequences of gauge invariance and the resulting low-energy theorems are reviewed. The multipole decomposition of the current operators and the general Siegert theorem are presented. The specific forms of vector and axial one-nucleon currents are given, together with lowest-order π- meson exchange and isobar currents as well as meson production currents. A brief overview is given on the most important one- and two-boson processes. Electron scattering in the one-boson approximation is then considered in greater detail. Formal expressions of the cross section for inclusive and exclusive processes are given, including parity-violating contributions from γ-Z interference as well as from parity-violating components in the hadronic wave function. Specific electromagnetic reactions on the deuteron are then discussed with respect to the influence of meson exchange currents, isobar configurations in the deuteron ground state, relativistic contributions and the role of π-meson retardation. Furthermore, recent results on coherent and incoherent π- and η-photoproduction are presented as well as a discussion of the Gerasimov-Drell-Hearn sum rule and the effect of a parity-violating deuteron component on inclusive electron scattering off the deuteron for quasifree kinematics. The review closes with a summary and a brief outlook.     

Ultra-sharp metamagnetic transition in manganite Pr0.6Na0.4MnO3

We report the magnetic and electrical transport properties of manganite Pr_0.6Na_0.4MnO₃. At the temperature of 2 K, a field-induced steplike magnetization and resistivity transition are observed. The step transitions of magnetization and resistivity are shifted to higher fields as a result of field cooling, and transformed to a smooth broad one when the cooling field is higher than 20 kOe. Moreover, in a magnetic field slightly below the critical field, the magnetic and resistive relaxation exhibits a spontaneous step after a long incubation time when both the temperature and magnetic field are constant. Such steplike transitions are discussed in terms of a martensiticlike transformation associated with phase separation.     

Q-dependent stoner factors and reformulated spin-fluctuation enhancements: V and Pd

Spin-polarized self-consistent LMTO band calculations are performed for supercells containing induced, “frozen” spin-waves. Momentum dependent Stoner factors S(q) are obtained as the local ratio between induced and applied spin splitting. The results are used to calculate the spin-fluctuation enhancement λ_sp on a similar basis as a calculation of the electron phonon coupling. The methods are tested on vanadium and palladium. For the latter a strong reduction of S(q) is found for large q. Obtained values for λ_sp are of reasonable magnitude.     

三光子纠缠W态隐形传输令牌总线网的保真度计算

计算了三光子W态隐形传输令牌总线网的保真度.通过计算发现在整个量子网络通信过程中,对于给定的分析角θ,保真度仅与系数|a|2有关|随着分析角θ的增加,保真度出现最大值所对应的系数|a|2相应减小,取θ=π/4、π/2、3π/4时可使保真度达最大值1,此时对应的|a|2分别为0.724、0.5和0.276.对于给定的系数|a|,保真度仅与分析角θ有关|若|a|=0,则无论θ为何值,保真度始终为0|若|a|=|b|=0.707 1,则当θ=π/2、3π/2时保真度达最大值1.     

Dilatonic effects on a falling test mass in scalar-tensor theory

Effects of a 4d dilaton field on a falling test mass are examined from the Einstein frame perspective of scalar-tensor theory. Results are obtained for the centripetal acceleration of particles in circular orbits, and the radial acceleration for particles with pure radial motion. These results are applied to the specific case of nonrelativistic motion in the weak field approximation of Brans–Dicke theory, employing the exact Xanthopoulos–Zannias solutions. For a given parameter range, the results obtained from Brans–Dicke theory are qualitatively dramatically different from those of general relativity. Comments are made concerning a comparison with the general relativistic results in the limit of an infinite Brans–Dicke parameter.     

Reformulation of general relativity as a gauge theory

The starting point is a spinor affine space-time. At each point, two-component spinors and a basis in spinor space, called “spin frame,” are introduced. Spinor affine connections are assumed to exist, but their values need not be known. A metric tensor is not introduced. Global and local gauge transformations of spin frames are defined with GL(2) as the gauge group. Gauge potentials B_μ are introduced and corresponding fields F_μν are defined in analogy with the Yang-Mills case. Gravitational field equations are derived from an action principle. Incases of physical interest SL(2, C) is taken as the gauge group, instead of GL(2). In the special case of metric space-times the theory is identical with general relativity in the Newman-Penrose formalism. Linear combinations of B_μ are generalized spin coefficients, and linear combinations of F_μν are generalized Weyl and Ricci tensors and Ricci scalar. The present approach is compared with other formulations of gravitation as a gauge field.     

Path integral methods for inelastic scattering

Corrections to the primitive semi-classical amplitude for multiple inelastic scattering are obtained from a path integral formulation of scattering theory. The path integrals are calculated by making an expansion about a classical orbit describing elastic scattering. Terms are collected to give a series in inverse powers of the reduced mass m of relative motion of the target and projectile. The leading term is the primitive semi-classical amplitude for multiple excitation and explicit formulae are given for the corrections of order $\text{1}\text{m}$. These are calculated in detail for a one-dimensional model. It is shown that some, but not all, of the corrections can be included by evaluating the primitive amplitude with a symmetrized orbit.