上海质子医疗装置的涡流效应

 涡流效应是较快重复频率加速器必须考虑的问题。涡流效应引入的六极、四极、二极分量,以及发热效应都会对环的参数如色品、工作点、共振、能量漂移等产生影响。通过计算引入不同效应的强度,模拟了各种效应对环参数的影响,并针对不同升能曲线和升能频率引入涡流效应的计算和比较,得出了在目前考虑的频率范围内,对主环影响较大的效应为六极场,其它效应的影响需要较大的重复频率。并以此为依据选择了最终的工作曲线为半正弦,上升时间为0.7 s。     

Spin-flip transport in one-dimensional comb-like waveguide

The spin-flip transport of electron in one-dimensional comb-like waveguide structures is investigated theoretically including the Rashba and Dresselhaus effects. The spin-polarized transmission of electron oscillates with changing the length of stubs and/or electronic momentum, and depends sensitively on electron spin orientation injected from the ferromagnetic source. The spin-flip transmission induced by the Rashba and Dresselhaus effects can only be up to 25% in the case of one stub, and can be enhanced significantly by adding more stubs. The spin-flip transmission induced by the Dresselhaus effect is similar to what induced by the Rashba effect for the one stub case, but is quite different for multi-stub case. The interplay between the Rashba and Dresselhaus effects shortens the period of transmission oscillation and enhances the splitting of the transmission peaks.     

On second-order optical processes

It is shown that if the full significance of the algebra involved in the performance of time-dependent perturbation calculations is appreciated, it is possible to predict the existence of a range of effects. These include magnetic field-dependent effects which can also be Raman shifted at sum, difference and second harmonic frequencies. The advantages of using these effects in conducting media is pointed out as well as the possible application to surface studies. These effects are all advantageously inproved by using resonance effects and in double-rather than single-beam experiments.     

Generation of aperiodic tilings with fivefold symmetry by the method of intersecting decagons and diffraction from finite size tilings

A method for generating aperiodic tilings with five fold symmetry is discussed here. Basic patterns formed within decagons can be used to fill two dimensional space, by matching such suitable patterns. It appears to be possible to generate perfect tilings without retracing already established coordinates imposing conditions at the initial stages of generating them. Various possible ways to generate tilings, when perfectness is not required, are discussed. The calculated diffraction patterns for some representative finite size tilings are shown. There are subtle differences in the intensities of peaks in the diffraction patterns corresponding to different finite size tilings constructed using intersecting decagons. These effects persist for a larger number of scatterers in weak peaks than in strong peaks. They are unaffected by an introduction of systematic disorder. These effects could be termed as the finite size boundary effects. There are also small shifts in the peak positions owing to the finite size effects. The possibility of formation of large approximate square cells in large tilings is shown.     

Directly and Simultaneously Expressing Absolute and Relative Treatment Effects in Medical Data Models and Applications

Logistic regression is widely used in the analysis of medical data with binary outcomes to study treatment effects through (absolute) treatment effect parameters in the models. However, the indicative parameters of relative treatment effects are not introduced in logistic regression models, which can be a severe problem in efficiently modeling treatment effects and lead to the wrong conclusions with regard to treatment effects. This paper introduces a new enhanced logistic regression model that offers a new way of studying treatment effects by measuring the relative changes in the treatment effects and also incorporates the way in which logistic regression models the treatment effects. The new model, called the Absolute and Relative Treatment Effects (AbRelaTEs) model, is viewed as a generalization of logistic regression and an enhanced model with increased flexibility, interpretability, and applicability in real data applications than the logistic regression. The AbRelaTEs model is capable of modeling significant treatment effects via an absolute or relative or both ways. The new model can be easily implemented using statistical software, with the logistic regression model being treated as a special case. As a result, the classical logistic regression models can be replaced by the AbRelaTEs model to gain greater applicability and have a new benchmark model for more efficiently studying treatment effects in clinical trials, economic developments, and many applied areas. Moreover, the estimators of the coefficients are consistent and asymptotically normal under regularity conditions. In both simulation and real data applications, the model provides both significant and more meaningful results.     

Elastic scattering of 1-GeV protons by nuclei

The calculated elastic scattering of 1.04-GeV protons by ²⁰⁸Pb, ⁵⁸Ni, and ⁴⁰Ca is compared with experiment. The effects of the spin-orbit potential, Pauli and short-range correlations, variations in the ratio of the real to the imaginary part of the nucleon-nucleon scattering amplitude at 0° are found to have similar effects. Further experiments are required before these effects can be disentangled. Changes of the neutron density compared to the proton density can be distinguished. The proton polarization by elastic scattering by ²⁰⁸Pb and ⁴⁰Ca is calculated omitting the effects of correlations.     

Thermal dissipation effects of the entangled photon generated by four-wave mixing process in a nonlinear ring resonator

We firstly analyze the thermal dissipation effects of the entangled photons generated by a nonlinear optical ring resonator. To obtain the corresponding equation of motion of the entangled photons generated by a four-wave mixing process within the system, we propose the Markov approximation to repel the reservoir operators. The system master equation in the interaction picture for both degenerate and non-degenerate cases is analyzed and obtained. The established system can be used to characterize the optimum entangled photons in some cases where the thermal dissipation effects may be introduced noise into the system. In this work, the entangled photons can be generated into two forms, firstly, the two entangled photon states is generated, the other, the four entangled photon states can be easily obtained. Results obtained have shown that the optimum entangled photon in term of entangled photon visibility can be compensated (i.e. unchanged) under thermal dissipation effects.     

On microscopical derivation of Lorentz-Lorenz formula

Lorentz-Lorenz formula may be derived microscopically by the analytical inversion of the dielectric matrix (DM) in the limit of tightly bound electrons. Exchange and correlation effects are to be taken into account and atomic polarisability is to be defined correctly in terms of the atomic susceptibility instead of the polarization operator. A wrong definition was the origin of usual contradictions between microscopical calculations and classical formula. The inversion of the DM diminishes dielectric constant in comparison with the diagonal element of DM but this procedure takes into account only a part of the local field effects caused by rapidly oscillating fields. Another part is connected with exchange interaction and increases the diagonal element of DM in comparison with dielectric constant without any local field effects, hence all local field effects do increase the dielectric constant.     

The stability of cantilever panels in uniform incompressible flow

The stability of large aspect ratio cantilever panels in uniform incompressible flow is studied by employing linearized plate and potential flow theories together with asymptotic expressions for the generalized pressures. It is assumed that if the downstream wake effects on the panel stability are insignificant then the results will be almost independent of where these effects are neglected in the analysis. Accordingly two approximations for the pressure, corresponding to different ways of neglecting the wake effects, are compared, and it is concluded that such effects cannot be ignored when the mass ratio is large. The results also demonstrate that a two-dimensional analysis (infinite aspect ratio) may yield an overestimate of the critical flow velocity for finite width panels.     

Causality,Measurement, and Elementary Interactions

Signal causality, the prohibition of superluminal information transmission, is the fundamental property shared by quantum measurement theory and relativity, and it is the key to understanding the connection between nonlocal measurement effects and elementary interactions. To prevent those effects from transmitting information between the generating and observing process, they must be induced by the kinds of entangling interactions that constitute measurements, as implied in the Projection Postulate. They must also be nondeterministic as reflected in the Born Probability Rule. The nondeterminism of entanglement-generating processes explains why the relevant types of information cannot be instantiated in elementary systems, and why the sequencing of nonlocal effects is, in principle, unobservable. This perspective suggests a simple hypothesis about nonlocal transfers of amplitude during entangling interactions, which yields straightforward experimental consequences.     

Convolution effects in superconductive tunneling

The quasiparticle density of states (DOS) of superconductors can be obtained from tunneling spectroscopy. When the normal-state differential conductance varies on the voltage scale comparable to that of strong-coupling effects, the standard normalization rule to extract the DOS is invalid, and the DOS is related to the measured data via an integral equation. These effects are exemplified by studying the geometry effect on the DOS for simple BCS superconductors. We apply these considerations to UPd2Al3 tunnel data where the apparent strong-coupling effects, previously deduced by use of the normalization rule, can be quantitatively attributed to convolution effects.     

Theoretical calculation of strength at stress concentration

Summary The mechanism of stress and strain concentration at fatigue loading is governed by two fundamental effects. Within the yield range of ductile materials the macro-support effect predominates, which can be represented by the results of a nonlinear theory derived by the author [1, 2, 4]. Within the high-cycle fatigue range the micro-support effects predominate, which can be described by the author's theory of mean stress value originally derived in connection with the calculation of sharply curved notches [1, 3, 4]. This theory introduces a material constant of length dimension. Taking the two effects into account, an approximate preliminary calculation of the fatigue strength of notched construction parts is possible [4].     

INFLUENCE OF A LEVELNESS DEFECT IN A THRUST BEARING ON THE DYNAMIC BEHAVIOUR OF AN ELASTIC SHAFT

This paper examines the non-linear dynamic behaviour of a flexible shaft. The shaft is mounted on two journal bearings and the axial load is supported by a defective hydrodynamic thrust bearing at one end. The defect is a levelness defect of the rotor. The thrust bearing behaviour must be considered to be non-linear because of the effects of the defect. The shaft is modelled with typical beam finite elements including effects such as the gyroscopic effects. A modal technique is used to reduce the number of degrees of freedom. Results show that the thrust bearing defects introduce supplementary critical speeds. The linear approach is unable to show the supplementary critical speeds which are obtained only by using non-linear analysis.     

Impacts of polarization mode dispersion on the pulse-width with considering initial pulse chirp and fiber GVD

The impacts of polarization mode dispersion (PMD) on the pulse-width in linear systems have been investigated. The analytical solutions, including the effects of initial frequency chirp and group velocity dispersion (GVD), are derived. Analyses show that the pulse broadening effects induced by the second-order PMD depend on GVD and chirp parameter, which are different from those induced by the first-order PMD. An initially chirped Gaussian pulse is taken as an example, upon which analytical solutions of rms pulse-width are derived before and after the first-order PMD compensation. The first-order PMD compensator is also evaluated based on these solutions. The results show that the pulse broadening effects will be resisted efficiently by choosing appropriate GVD and chirp parameter; in general, the post-transmission compensation method will be less efficient than the PSP-transmission method.     

Initial condition effects for a Brownian particle in a harmonic chain

The influence of initial deviations from bath equilibrium on the motion of a Brownian particle in a harmonic chain is investigated by exact calculation. These initial condition effects, which are excluded by convention in standard projection operator treatments of relaxation processes, are found to be relatively long-lived, contrary to usual assumption. For weak, localized initial deviations from bath equilibrium these effects on the motion are small in magnitude and may be accounted for by a modified initial condition on the particle velocity. For initial deviations involving many bath particles these effects are more substantial and retention of their time dependence in the particle equation of motion is generally required.For a correction to Ref. 2a see Ref. 3.     

Three-dimensional free vibration of thick functionally graded annular plates in thermal environment

The free vibration analysis of functionally graded (FG) thick annular plates subjected to thermal environment is studied based on the 3D elasticity theory. The material properties are assumed to be temperature dependent and graded in the thickness direction. Considering the thermal environment effects and using Hamilton's principle, the equations of motion are derived. The effects of the initial thermal stresses are considered accurately by obtaining them from the 3D thermoelastic equilibrium equations. The differential quadrature method (DQM) as an efficient and accurate numerical tool is used to solve both the thermoelastic equilibrium and free vibration equations. Very fast rate of convergence of the method is demonstrated. Also, the formulation is validated by comparing the results with those obtained based on the first-order shear deformation theory and also with those available in the literature for the limit cases, i.e. annular plates without thermal effects. The effects of temperature rise, material and geometrical parameters on the natural frequencies are investigated. The new results can be used as benchmark solutions for future researches.     

The Study of MMW and MW Attenuation Considering Multiple Scattering Effect in Sand and Dust Storms at Slant Paths

The influence of sand and dust storms on modern MMW and satellite communication systems reliability have been paid more attention to. The attenuations induced by sand and dust storms are estimated by means of Mie-theory and Rayleigh approximation, in the case of the tenuous distribution of particles. With the particle density increasing, however, these method become inadequate, the multiple scattering effects then become dominant for attenuation estimation. The attenuations considering multiple scattering effects are estimated by Monte-Carlo and four fluxes method at horizontal paths. At slant paths, based on multi-layer media model, the attenuations considering multiple scattering effects are calculated by layered Monte-Carlo method at 100, 37, 24, and 14GHz. It is shown that the multiple scattering effects should be considered at the attenuation prediction in the sand and dust storm, which the visibility is about 0.5km and smaller than 0.5km and frequency is about 20GHz. Above 30GHz, the multiple scattering effects due to sand and dust particles should be considered, as visibility is about 1km and smaller than 1km at slant paths.     

Dynamic analysis of flexible linkage mechanisms under uniform temperature change

Deformation and stresses are produced not by mechanical forces alone, but by temperature variation as well. The additional stresses of a flexible mechanism caused by the temperature change should not be ignored. The generalized equations of motion for flexible linkage mechanisms, in which the thermal effects are taken into account, are developed by utilizing the virtual work method and the finite element theory in this paper. Since the determination of thermal stresses plays an important role in the design of mechanisms operating at elevated temperatures, the stress–strain relationship should include the effects of temperature. Based on the closed-form numerical algorithm, the equations are solved and the recursive scheme is proved to be efficient and converged in a few iterations for the cases examined. The Runge–Kutta method is also applied to study the transient response of the temperature change. Numerical solution results show that a small change of temperature will cause a significant change of the stresses of a flexible mechanism. The effects of temperature change should not be ignored when analyzing the dynamic performance of flexible mechanisms.     

库仑相互作用对相对论性电子束受激散射的影响

本文研究了库仑相互作用对相对论性电子束受激散射的影响,在单能电子束的情况下,得到了反射激光场的解析表达式,结果表明,表征库仑相互作用贡献的因子与电子密度平方成正比,如果电子密度比较高,而入射辐射强度比较低,则库仑力的贡献是重要的,它的影响是不能忽略的。 关键词：