Equal-time commutators,fixed point theorems,superconvergency and PCAC in the Lee model

It is shown that some properties characteristic of the real physical theories can be illustrated in the standard Lee model, in particular fixed point theorems and superconvergency. The problem of equal time commutator has also been discussed. All “physical” results, both for the smeared and for the point source model depend on well defined and calculable quantities, the high energy behaviour of the scattering amplitude being in agreement with Bjorken's theorem. There is a particular “relativistic” generalisation of the model which allows for PCAC.     

Single crystal conductivity of bipyridine-TCNQ salts

The sharp contrast between the conductivity of complex TCNQ salts with symmetric and asymmetric bipyridine donors reveals the role played by the asymmetric molecules in well conducting organic salts. A highly anisotropic strongly correlated semiconductor is obtained when the donor molecule is symmetric, a smeared out “metal insulator” transition is found with the asymmetric donor modification.     

Vibrations of axially loaded stiffened cylindrical panels with elastic restraints

A method has been developed for analysis of the vibration and buckling of preloaded stiffened cylindrical panels with different boundary conditions along the straight edges, including elastic restraints. In the analysis linear, “smeared” stiffener, Flügge type theory is used. A computer program VIBUPAL has been developed. The method has been verified by comparison with results available for limited cases and very good agreement has been obtained.     

Topology, Holes and Sources

The Aharonov-Bohm effect is often called “topological.” But it seems no more topological than magnetostatics, electrostatics or Newton-Poisson gravity (or just about any radiation, propagation from a source). I distinguish between two senses of “topological.”     

A New Way of Looking at Nuclear Resonant Scattering

A new model for nuclear-resonant scattering of gamma radiation from resonant matter has been developed and is summarized here. This “coherent-path” model has lead to closed-form, finite-sum solutions for radiation scattered in the forward direction. The solution provides a unified microscopic picture of nuclear-resonant scattering processes. The resonant absorber or scatterer is modeled as a one-dimensional chain of “effective” nuclei or “effective” planes. The solution is interpreted as showing that the resonant radiation undergoes sequential scattering from one absorber “nucleus” or “plane” to another before reaching the detector. For recoil-free processes the various “paths” to the detector contribute coherently. The solution for this case gives calculated results that are indistinguishable from those using the classical optical model approach, although the forms of the solutions are completely different. The coherent-path model shows that the “speed-up” and “dynamical beating” effects are primarily a consequence of the fact that the single “effective” nuclear scattering processes are 180° out of phase with the incident radiation while the double nuclear scattering processes are in phase with the incident radiation. All multiple scattering paths are, and must be, included. The model can also treat the incoherent processes, i.e., processes involving gamma emission with recoil or conversion-electron emission. The source of the resonant gamma radiation can be from a radioactive source or from synchrotron radiation: both cases are treated. The model is used to explain and understand the results when each of the following experimental procedures is applied: time-differential Mössbauer spectroscopy, time-differential synchrotron radiation spectroscopy, enhanced-resolution resonant-detector Mössbauer spectroscopy, and the “gamma echo”.     

Influence of initial geometrical imperfections on vibrations of axially compressed stiffened cylindrical shells

The vibrations of stiffened cylindrical shells having axisymmetric or asymmetric initial geometrical imperfections and axial preload are analyzed. The analysis is based on a solution of the von Kárman-Donnell non-linear shell equations, an “exact” solution of the compatibility equation, and a first order approximation by the Galerkin method of the equilibrium equation. The stiffeners are closely spaced and “smeared” stiffener theory is employed. The results of an extensive parametric study carried out on shells similar to those used in vibration and buckling tests at the Technion show that stiffening of the shell will lower the imperfection-sensitivity of its free vibrations, but the decrease depends on the type of stiffening (stringers or rings), the mode shapes of the vibration and the imperfection, the stiffener strength and eccentricity. The imperfection-sensitivity decrease, caused by the stiffeners, is greater for vibration mode shapes with high imperfection-sensitivity than for other vibration mode shapes. The sensitivity differences between stringer and ring-stiffened shells depend especially on the vibration and the imperfection mode shapes, and on their coupling. Small imperfections change the natural frequencies of stiffened shells in the same directions as for isotropic shells, but to a smaller extent. The frequency dependence on the external load is also strongly affected by the imperfection mode shape. The results correlate well with earlier ones for isotropic shells.     

Evolutionary (frequency/time) spectral analysis of the response of vehicles moving on rough ground by using “covariance equivalent” modelling

In a number of physical problems such as the motion of vehicles travelling over rough ground or the noise emanating from a moving source, non-stationarity is induced by a non-linear time dilation (due to velocity variations or Doppler effects) of the source or excitation process so that the resulting process is “frequency modulated”. This is true even if the underlying process is homogeneous in another domain. Hitherto it has not been possible to apply the frequency/time analysis due to Priestley [1] to this class of problem but here, by introducing the concept termed “covariance equivalence” by the authors, this method can be seen to apply. An example of a vehicle moving with variable velocity on a rough surface is considered.     

Model independent features of the two-particle correlation function

The Hanbury-Brown Twiss correlation function for two identical particles is studied for systems with cylindrical symmetry. Its shape for small values of the relative momentum is derived in a model independent way. In addition to the usual quadratic “side”, “out” and “longitudinal” terms in the exponent of the correlator, a previously neglected “out-longitudinal” cross term is found and discussed. The model-independent expressions for the size parameters of the HBT correlation function are interpreted as lengths of homogeneity of the source, in distinction to its purely geometrical size. They are evaluated analytically and numerically for two specific thermal models featuring collective transverse and longitudinal flow. The analytic expressions derived allow one to establish qualitatively important connections between the space-time features of the source and the shape of the correlation function. New ways of parametrizing the correlation function and a new approach to the measurement of the duration of the emission process are suggested.     

Carbon as Reference for Normalizing Infrared Photoacoustic Spectra

Photoacoustic spectra of solids¹ are usually “source compensated,” i. e., normalized for differences in source emission at different wavelengths, and such compensation is done by comparing the photoacoustic spectrum of a sample to the emission spectrum of the source measured directly with, say, a photocell,² power meter,³ or photodiode,⁴ or to the photoacoustic spectrum of “carbon” recorded under the same conditions as that of the sample. A variety of carbons has been used for this purpose, including carbon black on silica,⁵ soot from a gas torch,⁶ and acatylene-sooted bakelite,⁷ such a reference substance being assumed to be a flat black absorber. That assumption appears to be valid, as indicated by the close     

Measurement of the four Stokes polarization parameters with a single circular polarizer

In this paper a method is developed to measure the four Stokes polarization parameters using a single circular polarizer. This is accomplished by measuring the first three Stokes parameters with the “circular” side of the polarizer facing the optical source and then flipping the polarizer to the “linear” side to determine the final Stokes parameter.     

Investigation of polyamorphism in compressed B<Subscript>2</Subscript>O<Subscript>3</Subscript> glass by the direct measurement of the density

Precise measurements of the relative volume change of vitreous B₂O₃ have been performed by the strain-gauge technique at hydrostatic pressures up to 9 GPa. The features of the strain-gauge technique are analyzed and the specificity of the measurements of “relaxed” and “unrelaxed” bulk moduli is discussed. Smeared anomalies of compressibility (at P > 0.5 GPa and P > 5 GPa) and logarithmic relaxation of the glass density are observed. A significant (by several times!) difference has been revealed between the relaxed bulk modulus of glass obtained from the volume measurements and the unrelaxed modulus estimated from the Brillouin spectroscopic data. The measurements of the relative volume change under compression together with the previous structure investigations and computer simulation results reveal the basic features of the phase transitions in B₂O₃ glass. Both direct and reverse transitions are smeared in pressure. The residual densification in glass is not associated with change in the short-range order.     

Maximum “focusing” of surface phonons

“Focusing” of surface phonons is studied in detail. Three types of surface phonon “focusing” are found. The asymptotic dependence of the amplitude u of surface wave on the distance r from a point source is obtained for every “focusing” type. The type of maximum “focusing” where $\text{u((r)～ O(r}{}^{\mathrm{<mtext>?1</mtext><mtext>4</mtext>}}\text{)}$ holds is picked out. The “focusing” type is shown to be changed as elastic anisotropy is altered.     

Can recent CERN experiments with 200 GeV/N O16 ions be explained by the independent NN collisions?

We argue that high energy nuclear collisions cannot be described by the “independent NN collision” models. In particular, secondary pions definitely should have multiple rescattering, and only by taking them into account, may one understand such observations as large “pion source” radius and the “cool component”, seen in the pion spectra at small p_⊥.     

频移阴影莫尔法

提出了一种新的莫尔条纹解调技术即频移法，它改变了莫尔条纹分布的频率，而相移莫尔法只是改变了莫尔条纹的相位。从阴影莫尔图分布的基本公式出发，借助于相移阴影莫尔法的思想推导并得出了频移阴影莫尔法的公式，在此基础上给出了特定条件下的产和公式。     

Modeling of the dolphin’s clicking sound source: The influence of the critical parameters

A physical and a mathematical models of the dolphin’s source of echolocation clicks have been recently proposed. The physical model includes a bottle of pressurized air connected to the atmosphere with an underwater rubber tube. A compressing rubber ring is placed on the underwater portion of the tube. The ring blocks the air jet passing through the tube from the bottle. This ring can be brought into self-oscillation by the air jet. In the simplest case, the ring displacement follows a repeated triangular waveform. Because the acoustic pressure gradient is proportional to the second time derivative of the displacement, clicks arise at the bends of the displacement waveform. The mathematical model describes the dipole oscillations of a sphere “frozen” in the ring and calculates the waveform and the sound pressure of the generated clicks. The critical parameters of the mathematical model are the radius of the sphere and the peak value and duration of the triangular displacement curve. This model allows one to solve both the forward (deriving the properties of acoustic clicks from the known source parameters) and the inverse (calculating the source parameters from the acoustic data) problems. Data from click records of Odontocetes were used to derive both the displacement waveforms and the size of the “frozen sphere” or a structure functionally similar to it. The mathematical model predicts a maximum source level of up to 235 dB re 1 μPa at 1-m range when using a 5-cm radius of the “frozen” sphere and a 4-mm maximal displacement. The predicted sound pressure level is similar to that of the clicks produced by Odontocetest.     

大尺寸化学Ni源金属诱导晶化多晶硅的研究

用无电电镀的化学方法，在VHF-PECVD沉积获得的非晶硅薄膜表面形成镍诱导源，在550℃下退火若干小时，可以诱导产生微米量级的多晶硅晶粒.用此法形成的镍源可以均匀地分布在非晶硅薄膜的表面.非晶硅薄膜上形成晶核的数量取决于镍溶液的浓度、pH值和无电电镀的时间等参量.当成核密度比较低时可以观察到径向晶化现象.用VHF-PECVD非晶硅薄膜作为晶化前驱物，晶化后多晶硅的最大晶粒尺寸可达到90μm.用此多晶硅试制的TFT，获得了良好的器件特性. 关键词： 金属诱导晶化 化学源 多晶硅 薄膜晶体管     

Propagation of a high-pressure microwave discharge in prebreakdown fields: Formation of plasma structures

A 3D model is developed, which describes the propagation of an initiated high-pressure microwave discharge in a linearly polarized wave beam. The equations for the electric field amplitude are solved self-consistently with the set of equations of plasmochemical kinetics. Plasma structures of the experimentally observed “snake” and “chain” types are obtained using this model. The calculation results enable one to determine the conditions of formation of one or another spatial structure, as well as the parameters of the plasmoids being formed. The results of calculation of the discharge propagation toward the radiation source are compared with the available experimental data.     

On the role of the shear term in jet noise

Increasing attention is being focused on Lilley's convected wave equation for the analysis of flow noise. It has the capability, not found in Lighthill's equation, of being able to deal with refraction. The other chief difference stems from the shift of a “source” term (shear noise) from the right-hand side of Lighthill's equation to the left-hand side to become a “propagation-amplification” term. It is argued herein, supported by comparative calculations according to theories of Mani and of Ri brier, that the alternative roles of the shear term have roughly equivalent effects on jet noise prediction outside the “refraction valley”. In either role certain mean flow “shrouding effects” are accounted for.     

Cosmic-ray muon and atmospheric neutrino fluxes at very high energies

Estimates of cosmic-ray muon and atmospheric neutrino fluxes at TeV energies are obtained taking into account a “prompt” production of muons and neutrinos through charmed-particle decays and a “direct” lepton-pair production through the Drell-Yan mechanism and resonances. It is found that the contribution of charmed particles to the muon flux is equal to that from the conventional sources (pion and kaon decays) at 60 TeV, and the same equality can take place at 10 and 1 TeV for muon and electron neutrinos, respectively (for particles coming to sea level in the vertical direction). This “direct” production contribution to muon and neutrino fluxes is estimated very arbitrarily, but it cannot be excluded that this contribution is equal to that from the conventional source at energies of 0.5 and 0.05 PeV for muons and muon neutrinos, respectively. Currently, the estimates of the “prompt” and the “direct” contributions to cosmic-ray muons and atmospheric neutrinos are only qualitative. This is true especially for the “direct” contribution. Nevertheless, it seems reasonable to attract attention to these potentially important sources of atmospheric muons and neutrinos.