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In this paper, blockage effects on high-frequency antennas are studied and their influence on the voltage standing wave ratio, gain, and radiation patterns is analysed. By simulating different blockage effects, the relationship between the antenna and the size of the blockage is clarified. It finds that radiation patterns are usually affected more seriously than other coefficients. The impact on the pattern is greater if the size or height of the blockage is larger than half of the wavelength. Two methods relating to the modification of the angle and height of the antenna are proposed that can reduce the influence of blockage effects. These are verified using a simulation and one is further demonstrated using a practical application. [ABSTRACT FROM AUTHOR]

This paper introduces the propagation properties and polarization characteristics of radially polarized partially coherent vortex beams in anisotropic plasma turbulence and discusses in detail the distribution of light intensity in such beams as a function of propagation distance. In addition, we analyze how the parameters of the anisotropic plasma turbulence affect the degree of polarization, polarization orientation angle, and degree of ellipticity of the beam. The results show that the degree of polarization of the radially polarized partially coherent vortex beam satisfies the modification of the central origin zero and the gradual increase with the radius during plasma turbulent propagation. At the same time, smaller turbulence eddies in the anisotropic plasma turbulence render, more obvious the irregular structure perpendicular to the vortex-stretching direction, the smaller the influence on the polarization characteristics of the radially polarized partially coherent vortex beam. It is advantageous to the research on optical communication and the study of anisotropic plasma turbulence. [ABSTRACT FROM AUTHOR]

Objective: Illegal parking in emergency lanes (paved highway shoulders) is becoming a serious road safety issue in China. The aim of this study was to (1) examine the utility of the theory of planned behavior (TPB) extended with descriptive norms, past behavior, facilitating and deterring circumstances, sensation seeking, and invulnerability in predicting Chinese drivers' intentions toward illegal emergency lane parking; (2) investigate whether respondents' demographic characteristics would impact their views toward the behavior and predictive patterns of intentions; and (3) identify significant predictors of intentions.Methods: In this cross-sectional study, eligible respondents were all qualified Chinese drivers. A self-administered questionnaire was employed to collect data, including demographic information, descriptive norms, past behavior, facilitating and deterring circumstances, sensation-seeking, and scenario-based invulnerability combined with TPB constructs. Descriptive statistics, multivariate analyses of variance (MANOVAs), and a series of hierarchical multiple linear regression analyses were conducted in SPSS.Results: A total of 435 qualified drivers (234 males and 201 females) with a mean age of 35.2 years (SD =10.3) were included in analysis. The descriptive analysis showed that most participants reported weak intentions (M = 2.35) to park illegally in emergency lanes with negative attitude (M = 3.19), low perceived support (M = 2.91), and high control (M = 5.08) over the behavior. The model succeeded in explaining 64% of the variance in intentions for the whole sample, and principal TPB components accounted for 21% of variance in intentions after demographic variables were controlled for. MANOVAs revealed that significant differences of respondents' opinions toward illegal emergency lane parking were only found between better educated drivers (with college education background) and less-educated ones. Separate regression analyses revealed that the predictive pattern of better educated participants also differed significantly from that of less-educated ones.Conclusion: The study revealed that perceived behavioral control, past behavior, facilitating circumstance, and invulnerability emerged as consistently significant predictors of Chinese drivers' intentions to park illegally in emergency lanes. Findings of this study may have some practical implications in developing multifaceted interventions or education processes for illegal emergency lane parking in China. [ABSTRACT FROM AUTHOR]

An efficient approach to analyze the electromagnetic (EM) scattering from coated objects above a three-dimensional (3-D) dielectric random rough surface is proposed in this paper. The electric and magnetic current densities on the sea surface are analytically realized using the semi-deterministic facet scattering model (SDFSM). Considering Fresnel reflection coefficient, a scheme combining the shooting and bouncing rays (SBR) and the physical theory of diffraction (PTD) is developed to calculate the scattering of the coated objects. Simulation results obtained with the combined method are verified by comparison with exact simulations using the multilevel fast multiple method (MLFMM). Scattering of large coated objects over sea surface composite model are too large and complex to be calculated using exact methods. With the asymptotic approach in this paper, the scattering performance can be analyzed with rather moderate computational efforts. Numerical results of composite scattering from an electric large three-dimensional model, e.g. an airplane target over a randomly rough surface with Pierson Moskowitz (PM) spectrum are presented and discussed. [ABSTRACT FROM AUTHOR]

A novel expression based on conventional Non-Uniform Rational B-Splines surfaces is proposed to model a scatterer, which can be used to overcome the deficiencies of conventional modeling method and can also be combined perfectly with the stationary phase method (SPM). Furthermore, we propose a fast and accurate algorithm to locate inner critical points and boundary critical points of physical optics (PO) integrals, as well as to locate stationary points of edge-diffracted integrals. The terahertz (THz) scattering field from an electrically large scatterer is evaluated by the physical theory of diffraction and SPM (PTD-SPM), which consists of four parts, including the PO scattering field from inner critical points, boundary critical points, corner points of PO integrals, and edge-diffracted field from the stationary points of edge-diffracted integral. Moreover, the order of magnitude of each part contribution is derived. Numerical results demonstrate that PTD-SPM is a valid and efficient algorithm for analyzing THz scattering from an electrically large scatterer. [ABSTRACT FROM AUTHOR]

Polarimetric scattering model of second-order small-slope approxi-mation combined with “choppy wave" model (CWM) for describing nonlinear hydrodynamic interactions between ocean waves is utilized in this paper to investigate the influence of sea surface nonlinearities on backscattering coefficient as well as Doppler spectrum signatures including Doppler shift and spectral bandwidth. Simulation results show that at moderate to large incidence angles the Doppler shift and spectral bandwidth of the CWM nonlinear sea surfaces are significantly larger than those of linear sea surfaces, in particular at low grazing angles. In addition, Doppler signatures show distinct polarization dependence, and most importantly the cross-polarized Doppler signatures significantly differ from the co-polarized ones. It is also indicated that co-polarized Doppler shift increases obviously with wind speed increasing, whereas the cross-polarized Doppler shift looks less sensitive to wind speed variations. The difference of Doppler signatures between co- and cross-polarization is potentially valuable for ocean remote sensing applications, especially for observing very high winds. [ABSTRACT FROM PUBLISHER]

This paper is aimed at applying the multiregion model to the composite EM scattering from a dielectric target and a dielectric rough surface. In the multiregion model, the rough surface is divided into multiple regions, the method of moment (MoM) is only adopted in the dominant region. Hence, this model can markedly reduce the number of unknowns. Firstly, we derived the single integral equation (SIE) in which the number of unknowns is half of those in the conventional MoM and the equations will be easier to deal with. Then the multiregion model is extended by SIE. With the multiregion model, one can obtain the accurate equivalent currents on the dominant region and accurate bistatic scattering coefficient in small and moderate scattering angles with much less time and memory requirement. [ABSTRACT FROM AUTHOR]

The high-power microwave easily causes the air breakdown in the near-field region of an antenna that is one of major factors to limit the enhancement of the radiation power at present. We study the maximum radiation power of a circular aperture antenna at which the maximum electric field in the near-field region equals the breakdown electric field in air, by using the field equivalent principle along with the global model. Results show that, with the pulse width increasing, the maximum radiation power decreases. The larger the antenna radius, the higher power can be radiated. The field distribution on the aperture has an obvious impact on the maximum radiation power. [ABSTRACT FROM AUTHOR]

Debye series expansion is employed to the analysis of radiation pressure force exerted on a spherical particle induced by an axicon-generated Bessel beam. The beam shape coefficients for Bessel beams are calculated using analytical expressions obtained by the integral localized approximation, and the scattering coefficients are expanded using Debye series. The effect of different parameters (beam center location, radius of particle, half-cone angle, etc.) on radiation pressure force is studied. The contributions of different scattering processes on radiation pressure force are isolated for better understanding of physical mechanism of various features of radiation pressure force. [ABSTRACT FROM PUBLISHER]

The shift operator finite difference time domain (SO-FDTD) method is developed to deal with a hybrid dispersive media model. First, we prove that the complex permittivity of the hybrid dispersive media model can be described by a rational polynomial fraction with respect to jω. Then, the relation between electric displacement D and electric field strength E is derived in the time domain by introducing zt as a shift operator. The constitutive relation in the discretized time domain and the recursive formulation of D and E available for FDTD computation are obtained. Finally, the reflection of the hybrid dispersive slab is computed. The computed results are in good agreement with that obtained by analytic method. This illustrates the generalization and the feasibility of the presented scheme. [ABSTRACT FROM AUTHOR]