Influence Of Oblique Incidence Research Articles

Fragility Analysis of RC Frame Structures Subjected to Obliquely Incident Seismic Waves

Obliquely incident seismic waves have been habitually overlooked in fragility analysis. In this paper, a new approach to solving the equivalent loads on the infinite element boundary due to obliquely incident seismic waves is proposed. Based on the site conditions and structural characteristics in the Jiaxing area, the seismic response of a multi-story reinforced concrete (RC) frame structure has been fully investigated through the finite element method. Under obliquely incident SV waves (shear wave in the vertical x-z plane), the distribution of internal forces on the structure in the case of homogeneous foundation soil is significantly asymmetrical. Among the 3 obliquely incident angles investigated in this paper, the maximum inter-story displacement is smallest when the incident angle is 20° and largest when the angle equals 30°. For the structural fragility, the exceedance probability at each structural damage level is smallest when the incident reflection angle is 20° and largest when the angle equals 30°. When the structure is located in the silty valley, the influence of oblique incidence is attenuated and there is no obvious stress asymmetry on the structure due to the refraction of seismic waves on the interface.

Influence of Oblique Incidence on the Reflection Losses in a Multilayer Human Body Medium

Implantable antennas have many important healthcare applications. One key aspect for a successful communication process from the implantable device to the on or off-body receiver is the accurate evaluation of the in-body path losses. These losses include, mainly, the attenuation and the reflection losses. Usually, normal incidence is considered for the calculation of the reflection losses between the tissue layers. However, this is not very accurate as the incident wave may be oblique at the boundary between the tissue layers. Therefore, in this paper the influence of oblique incidence on the reflection losses in a multilayer human body model is investigated. The reflection losses at the bone/muscle, muscle/fat and fat/skin layers are calculated at 403 MHz considering the cases of parallel and perpendicular polarization oblique incidence. The results are analyzed and compared with those of normal incidence. They show that larger losses are obtained at some angles for the case of oblique incidence compared to those for the case of normal incidence (about 241.16% larger reflection loss is obtained at an incident angle of 85° for the case of oblique incidence/perpendicular polarization at the fat/skin interface in comparison with that for normal incidence). Hence, it is very important to take the oblique incidence into consideration to provide more accurate in-body path loss calculations.

基于二次相位超表面的大视场紧凑型全Stokes偏振测量方法

Polarization is one of the inherent characteristics of light, but the polarization information of electromagnetic waves is lost by traditional intensity and spectral detection technology. At the same time, not only the devices and technologies based on polarimetry have the problem of limited field of view, but also the measuring systems are complicated. In this paper, a compact large field-of-view polarimeter was designed based on dielectric metasurface, which realized the detection of the angle and polarization state of the incident light. The device was composed of 2×2 quadratic phase metasurfaces, each of which realized the symmetry transformation for a specific polarization, that is, the rotational symmetry of the incident angle was converted into the translational symmetry of focus in the focal plane. The theory of the symmetry transformation of the quadratic phase made it possible to characterize the angle of incidence by measuring the offset of the focus over a wide angle range (−40°—+40°). On this basis, the influence of oblique incidence on the measurement of Stokes parameters was elaborated, and the modified Stokes formula was obtained. The Stokes parameters of the incident light can be calculated by utilizing the intensities of the four focal points and the modified Stokes formula. The measured Stokes parameters agree well with the theoretical values, when the field-of-view is 0°, 20°, and 40°.

Phase modulation characteristics analysis of liquid crystal spatial light modulator under oblique incidence.

A correction method for obtaining the phase modulation curves of liquid crystal spatial light modulator (LCSLM) systems under oblique incidence is proposed. Considering the reflection and refraction of the interface, the influence of oblique incidence on the LCSLM phase modulation was simulated and analyzed by solving the extended Jones matrix. The polarization interference principle was applied to construct a phase modulation system, the phase modulation was measured at different incident angles, and the measured data were subjected to Fourier fitting. The phase modulation curve was corrected to a straight line using the inverse interpolation method, and the lookup table (LUT) for the gray level and phase was then generated through the line coordinates. The measured results revealed that a larger angle of oblique incidence led to a smaller range of phase modulation. For LCSLM to function over a range from 0 to 2π, the oblique incidence angle should be less than 45°. Experimental results using 25° as an example confirmed the validity of the LUT. The correlation coefficient R between the phase modulation curve and the ideal linear curve was 0.9893, and the root-mean-square error was 0.1888. At incident angles from 0° to 45°, the linearity of the corrected LUT was as good as that of the LUT for vertical incidence, thereby laying the foundation for high-precision beam pointing control.

Negative refraction characteristics of a kind of concave metamaterial

This paper proposed a metamaterial with a high trough, high bandwidth, and high quality negative refraction band. It is composed of an axisymmetric concave sheet metal, an annular coil, and two parallel planar metal wires, and has passed the classical triangle verification. The influence of oblique incidence on the performance of the device was analyzed, and the relationship between plasma frequency and cell size was studied. By using an ingenious test scheme, the free space measurement of electromagnetic parameters was completed.

Effects of tissue surface curvature and incident light angle on diffuse correlation spectroscopy

Diffuse correlation spectroscopy is an emerging technique for the continuous, non-invasive monitoring of blood flow in biological tissues. However, the influence of oblique incidence and surface curvature has not been fully discussed. In this paper, we study the effects of the incident angle and surface curvature on diffuse correlation spectroscopy measurement and the blood flow index (BFI). For semi-infinite plane with lower absorption, oblique incidence angle has slightly stronger influence. Larger incident angles lead to high values and a reduced decay rate of the normalized electric field temporal autocorrelation. When the radius of curvature is more than 10 cm, the BFI estimation error reduced to less than 5% and very close to semi-infinite plane case. Besides, for the surface with small radius of curvature, larger incident angles sometimes may cause smaller estimated errors of the BFI. This work may help improve BFI estimation accuracy from diffuse correlation spectroscopy.

Seismic response analysis of GRPS embankment under oblique incident P wave

In order to investigate the seismic performance of geosynthetic reinforced and pile supported (GRPS) embankment under seismic loads, an input method for three-dimensional oblique incidence of P wave was proposed. This method is based on the explicit finite element method while considering the viscous-spring artificial boundary (VSAB) condition. Using the proposed method, a numerical study was conducted, and the influence of oblique incidence on the seismic response of GRPS embankment under the oblique incident P waves was analyzed. The results indicate that in comparison with vertical incidence, the oblique incidence can significantly increase the displacement, velocity and acceleration of key locations in the GRPS embankment. The existence of geosynthetics can alleviate the impact of seismic load on the response of the embankment to a certain degree. Moreover, the number of reinforcement layers and modulus of geogrid also greatly influence the seismic performance of GRPS embankment.

Influence of Oblique Incidence on Transmission Grating Diffraction in Soft X-Ray Region

Influence of Oblique Incidence on Transmission Grating Diffraction in Soft X-Ray Region

Influence of impact ionisation detection methods on determination of dust particle flux in space

Results are presented for a series of experiments investigating effects which can influence the interpretation of data from ionisation-based dust detectors carried on spacecraft. First, the variation of the impact ionisation yield with angle of impact was studied for impacts of iron microparticles onto gold at speeds of 1– 75 km s −1 . The angle of incidence was from 0° (normal incidence) to 80° (glancing incidence). Little or no variation was observed at angles up to 60°, but at 80° the total impact ionisation signal was around an order of magnitude lower than at smaller angles. In addition, the fast rising component of the ionisation signal rise time showed no variation with impact angle, but the total signal rise time showed a steady decrease. The effect of secondary impact ionisation resulting from particle impacts on detector side walls was also studied. Iron microparticles were fired on to an aluminium target at various angles, and the impact ionisation signal on a nearby gold target was measured. It was found that ionisation signals were observed on the gold target, and that these were very similar in appearance to those observed in direct impacts. The effect of reduction in particle charge on an impact ionisation signal was investigated. Iron microparticles were fired on to a gold target after passing through a thin film which reduced the charge which was used to accelerate them. It was found that there was a measurable drop in ionisation signal in the reduced-charge case. The empirical relation I IONISATION=1.67×10 −9 Q PARTICLE 0.35 (units of C) was found. This implies there is a component in the observed ionisation signal that is not related to the impact. To test this, charged tungsten carbide particles were dropped at very low velocity onto a replica of a dust detector used in space whilst placed in a vacuum chamber. Ionisation signals were frequently recorded by the detector. It was concluded that this signal originated from the incident particle charge. In the final section of work, as an example, the influence of oblique incidence, side-wall impacts and particle charge effects on data collected by the Gorid dust detector in Earth orbit were investigated. Corrections were applied to the mass and velocity distributions derived from Gorid data. In extremis, oblique incidence effects were found to shift the mass distribution down by an order of magnitude, and the velocity distribution up by a factor of two to three. If all the data had come from unrecognised side-wall impacts, the mass distribution would be shifted downwards to lower masses by three orders of magnitude, and the velocity distribution upwards by a factor of five. Possible particle charge effects were found to shift the mass distribution down by 30%, and did not alter the velocity distribution. Overall we have investigated a variety of impact-related phenomena and conclude that these can affect the interpretation of data from instruments deployed in space.