Effect Of Oblique Incidence Research Articles

Effects of Oblique Incidence on Aratosawa Landslide during the 2008 Iwate-Miyagi Earthquake

Effects of Oblique Incidence on Aratosawa Landslide during the 2008 Iwate-Miyagi Earthquake

Optical design of vertical edge Thomson scattering on HL-2M tokamak

A vertical edge Thomson scattering (ETS) diagnostic system on HL-2M tokamak has been designed. The ETS system collects the scattered light from Nd:YAG laser (1064 nm, 2 J, 30 Hz, 15 ns). The laser beam propagates vertically through the plasma region and the polarization is parallel to the toroidal magnetic field. A special designed Galileo-type telescope with long Rayleigh length is applied to focus the laser size and ensure collimation. A group of double-Gaussian collection lenses image the 600 mm vertical scattered region onto rectangular fiber arrays with a spatial resolution of 10 mm. The 2.20 mm × 2.86 mm fiber optic bundle consists of 130 low hydroxyl (OH) 200/220 μm (core/cladding) diameter fibers with numerical aperture NA = 0.22, carrying the light to remotely located multi-channel polychromators. Effect of oblique incidence on narrow band filter has been analyzed. The designed electron temperatures range from 5 to 1000 eV and electron densities from 5 × 1018 to 1 × 1020 m−3.

Hydroelastic Response to Oblique Wave Incidence on a Floating Plate with a Submerged Perforated Base

A hydroelastic model is developed of a floating flexible structure in the presence of a submerged perforated base connected with mooring lines under oblique wave action. Using the velocity decomposition method, the analytical solution of the referred model is obtained in finite water depth. The convergence of the analytical solution for different oblique wave incidences is examined, and the present results of deflection amplitude are compared with experimental datasets and the numerical results available in the literature. The effects of oblique wave incidence, along with various design parameters on the reflection, transmission, and dissipation coefficients, as well as structural displacements, are analysed through hydroelastic analysis. Further, the effect of oblique incidence angle on the free oscillation hydroelastic waves in two wave modes is investigated by deriving the free motion velocity potential in a wave basin.

Femtosecond pulsed laser ablation for paint removal at oblique illumination: Effect of the incidence angle

This research studies how the angle of incidence affects the ablation process when a pulsed femtosecond laser with a wavelength of 1040 nm and a high repetition rate is applied to spray paints used for graffiti. Flat test samples were painted using four different spray paints (red, blue, black and silver). All paints had an organic base but different physicochemical properties. For each paint, the ablation process was characterized using confocal microscopy, determining the threshold fluence and the penetration depth of the laser radiation at normal incidence. For different sample tilt angles in the range of 0°–60°, the effect of oblique incidence was analysed in terms of its effect on the ablation rate and the geometric properties (depth and width) of the ablation grooves on each paint. The results show a clear decrease in the ablation rate as the angle of incidence moves away from normal incidence. Moreover, it can also be observed that for a given angle, groove depth is the property most affected by beam tilt. These results represent a necessary step in addressing both cleaning and other laser ablation processes on non-flat surfaces in a controlled and reproducible manner.

Fast aerial image model for EUV lithography using the adjoint fully convolutional network

The effects of thick-mask and oblique incidence in extreme ultraviolet (EUV) lithography system make the aerial image calculation a challenging task. This paper develops a fast EUV lithography aerial image model based on a new kind of deep learning framework called adjoint fully convolutional network (AFCN). The AFCN consists of two adjoint data paths to respectively recover the real part and imaginary part of the complex mask diffraction-near-field (DNF). The feature-swapping technique is introduced to exchange the information between the real and imaginary data paths. The AFCN is trained based on a pre-calculated rigorous thick-mask DNF dataset. Given the estimated thick-mask DNF, the Abbe's method is used to calculate the aerial image of the partially coherent lithography system. Compared to the traditional non-parametric kernel regression method, the proposed model reduces the error by more than 80% and achieves 25-fold improvement in computational efficiency.

Reflective and transmissive cross-polarization converter for terahertz wave in a switchable metamaterial

Utilizing the phase transition characteristic of vanadium dioxide, we present a metamaterial configuration to achieve both reflective and transmissive cross-polarization converters. When vanadium dioxide is metal, the design behaves as a reflective cross-polarization converter. It consists of metallic grating, topas spacer, and vanadium dioxide film. Polarization conversion ratio is more than 90% in the frequency range from 4.80 THz to 13.13 THz. When vanadium dioxide is insulator, the design behaves as a transmissive cross-polarization converter using cascaded metallic gratings with rotation angle 45°. High-efficiency broadband cross-polarization wave conversion is achieved in the frequency band of 0.50–4.75 THz. Effect of oblique incidence is studied on polarization conversion. Results tell that cross-polarization conversion is better when incident angle is in the range of 0°–40°. The designed metamaterial may have a certain inspiration for the research of terahertz multifunctional polarization converter.

Surface dose and build-up region depth dose measurements in non-standard beams of Cyberknife and tomotherapy systems.

The purpose of this study was to measure the surface dose and build-up region depth dose characteristics of 6 MV photon beams in Cyberknife and helical tomotherapy (HT) systems for non-standard small fields using parallel plate chambers (Roos and Markus), Gafchromic EBT3 films, and nanoDot optically stimulated luminescence dosimeters (OSLDs), as well as to investigate the effect of oblique incidence on the surface dose of the beam. All measurements were conducted in a virtual water phantom under machine-specific reference conditions. The Roos and OSLDs overestimated the surface dose when compared with the Markus chamber and EBT3 films by 20%. We applied water equivalent thickness (WET) correction to account for the intrinsic build-up thickness of the detectors from their effective point of measurement (EPOM). With WET correction, a reasonably close surface dose estimate was obtained for all detectors, within 1.9% agreement for the 60mm collimator of Cyberknife and 3.1% agreement for the HT system, with a 5 × 10 cm2 field size. The surface dose increased from the normally incident Cyberknife and HT fields with increasing angle of incidence. The surface dose increased to twice its value at normal incidence for highly oblique angles of incidence above 55°. For the tested fields, a reasonable surface dose estimate could be measured with the detectors if the correction for intrinsic buildup thickness was applied. Nevertheless, the use of Roos chambers with large dimensions and nanoDot OSLDs is not recommended for estimating the surface dose for small fields.

Wave energy extraction for an array of dual-oscillating wave surge converter with different layouts

Array configuration of oscillating wave surge converter (OWSC) devices in nearshore is a preferable option for realizing a cost-balance of extracting wave energy and reducing installation expense due to closer installed place to coastline. The goal of the present work is to assess energy extraction of an array of dual-OWSC system with different layout schemes in comparison with an isolated OWSC, which can be regarded as a guideline for multi-array configuration in realistic wave farm. The coupled three-dimensional (3-D) hydrodynamic model is established based on the potential flow theory with fully nonlinear boundary condition in time domain. A non-dimensional approach is conducted to focusing on the accurate effects of multi-body interaction, wave nonlinearity, wave resonance, mechanical damping, layout scheme and oblique incidence as optimization design. For a front-back array system, wave resonance in dual-module gap enhances significantly the energy extraction of the front OWSC but does not contribute much to that of the back OWSC. Furthermore, wave resonance in wide gap has a positive effect on the capture efficiency in large wave periods. An in-line array system has a beneficial performance in small wave periods, while a staggered array system realizes more energy extraction in resonance region. A strong wave disturbance between flap sides of an in-line and staggered system, leads to the increase of energy extraction for the back OWSC with imposing small incident wave heading. Therefore, the combination of multi-triple-array OWSC with different gap distances will provide a desirable configuration which is independent on oblique wave conditions.

Characteristics of thermophotovoltaic emitter based on 2D cylindrical gear grating

A novel wavelength-selective thermophotovoltaic (TPV) emitter is proposed and analyzed with high emissivity. The suggested TPV emitter is based on cylindrical gear grating of tungsten with SiO2 spacer. The design geometry is studied to maximize its emissivity up to wavelength of 2.0 μm. The effect of oblique incidence at different polarizations on the design emissivity is also introduced. Additionally, the inductor-capacitor (LC) model is used to elucidate the behavior of magnetic resonance of the proposed grating. The reported TPV emitter exhibits high emissivity properties over large spectra range from ultraviolet to mid-infrared with spectral efficiency of 74% and 95% at 1000 and 2000 K, respectively. Further, high emissivity is achieved over a wide range of incident angles from 0 to 65° for the two polarized waves. The achieved perfect emissivity is due to the coupling between surface plasmon polariton, magnetic polariton and intrinsic loss of the tungsten material.

Effects of oblique incidence and colliding pulses on laser-driven proton acceleration from relativistically transparent ultrathin targets

The use of ultrathin solid foils offers optimal conditions for accelerating protons to high energies from laser–matter interactions. When the target is thin enough that relativistic self-induced transparency sets in, all of the target electrons get heated to high energies by the laser, which maximizes the accelerating electric field and therefore the final ion energy. In this work, we first investigate how ion acceleration by ultraintense femtosecond laser pulses in transparent CH $_2$ solid foils is modified when turning from normal to oblique ( $45^\circ$ ) incidence. Due to stronger electron heating, we find that higher proton energies can be obtained at oblique incidence but in thinner optimum targets. We then show that proton acceleration can be further improved by splitting the laser pulse into two half-pulses focused at opposite incidence angles. An increase by ${\sim }30\,\%$ in the maximum proton energy and by a factor of ${\sim }4$ in the high-energy proton charge is reported compared to the reference case of a single normally incident pulse.

On the specially designed fractal metasurface-based dual-polarization converter in the THz regime

A specially designed fractal metasurface-based structure was investigated as a dual-polarization converter operating in the terahertz (THz) band. The proposed converter has the ability to perform both the linear-to-cross (LX) and linear-to-circular (LC) polarization conversions. In the former kind of operation, it exhibits three unity polarization conversion ratio (PCR) peaks at 1.10 THz, 2.13 THz and 3.46 THz frequencies, whereas in the latter situation, the conversion was achieved over three operating bands, namely 1.2–1.83 THz, 2.52–3.10 THz and 3.78–3.90 THz. The effect of oblique incidence on the performance of metasurface (used in designing the converter) was also studied, and fairly stable operation could be determined. The obtained results indicate the proposed converter to have possible potentials in imaging, antenna engineering and certain other photonic devices used in the fields of medical diagnostics, sensing, and other related measurements.

A High-Efficiency Conformal Transmitarray Antenna Employing Dual-Layer Ultrathin Huygens Element

A high-efficiency conformal transmitarray with ultrathin dual-layer Huygens element is developed. The element consists of “I” shape patches for magnetic response and “T” shape stubs for electric response printed on two metal layers of a single substrate with only 0.5 mm thickness (λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> /60 at 10 GHz). By tuning the magnetic and electric responses, the transmitting phase of the element can be changed. Eight elements are designed to cover quantized 360° phase range with a maximal 1.67 dB loss. Then, the proposed elements are employed in a small conformal transmitarray design. To improve the antenna efficiency, the elements' dimensions are calculated by considering the oblique incidence effects. Finally, a cylindrically conformal transmitarray with a larger aperture size is simulated, fabricated, and measured. It can achieve a measured gain of 20.6 dBi with a 47% aperture efficiency.

Effects of Oblique Incidence of SV Waves on Nonlinear Seismic Response of a Lined Arched Tunnel

The incident direction of earthquake motion is an important factor affecting the seismic response of underground structures. In this study, a three-dimensional (3D) oblique incidence method of SV waves is proposed and the effects of incident angles of SV waves on the seismic response of a lined arched tunnel are evaluated. Based on wave field decomposition principle and equivalent node force method and together with viscous-spring artificial boundary, the oblique incidence method of SV waves is implemented by transforming seismic wave field into the equivalent nodal forces acting on the artificial boundaries. By deriving the distance of the incident waves and the reflected wave on free surface to artificial boundaries, this method can comprehensively consider the phase difference of the seismic wave propagation and the influence of the damping effect of the rock medium on the seismic wave propagation. The method is programed into a dynamic finite element program and its effectiveness is examined by a numerical example. Consequently, the oblique incidence method is applied to evaluate the seismic behaviors of the tunnel. The numerical results reveal that (1) the oblique incidence of the seismic wave results in a larger seismic response; (2) the response amplitudes of the stress and displacement increase with the increase of incident angles and reaching the maximum in the case of 30° incident angle; (3) the damage extent increases with an increase in the incident angles, and the oblique incidence of the seismic wave is believed to increase the spatial difference of damage distribution.

Consideration of Oblique Incidence in 3-D Imaging of a Planar Interface With a Circular Dipole Array in an Air-Filled Borehole

We consider the effects of oblique incidence of a wave on the creation of a 3-D image of a planar interface with an array-type directional borehole radar. In this study, we focus on the situation where the radar probe is close to the planar interface. In such circumstances, the reflected wave from the planar interface may be incident on the receiving array antenna at very steep elevation angles. As a result, borehole effects cause differences in the arrival times of the wave at the array elements, and consequently some errors emerge in imaging the planar interface. Observing the arrival time differences, we present an algorithm to compensate those errors in creating a 3-D image of a planar interface. Computer simulations predict that the errors may occur when the circular dipole array antenna is in an air-filled borehole in rock. Numerical simulations show that our proposed algorithm generates a 3-D image of an interface around an exact position, whereas conventional methods produce some spurious images opposite to the correct position (i.e., out of position by 180°). We then applied the proposed method to analyze reflected waves from a real-world fault in rock. A 3-D image of the fault could be successfully created, which was not possible using the conventional method.

Effect of oblique incidence on the optical engine of extinction ratio

The optical engine (OE) is the core component of a projection optical system. The extinction ratio (EO) directly affects imaging contrast. A three-dimensional EO calculation and analysis method, based on traditional EO theory, is proposed to obtain the optimal incidence angle range and solve the problem of ignoring the oblique incidence’s influence on the EO’s existing research process. The method is simulated and verified by LightTools. Results show that, when the incident azimuth half angle is less than4.7∘, and the spatial half angle is less than180∘, the EO is 0.016, distribution is uniform, and the stray light is effectively suppressed.

Wideband Inhomogeneous-Polarizer Loaded Circularly Polarized SIW Horn Antenna for Broadband Millimeter-Wave Applications

An inhomogeneous-polarizer loaded substrate integrated waveguide (SIW) horn antenna is proposed to obtain wideband circularly polarized (CP) radiation. First, by introducing extended substrate and extra dielectric slabs around the horn radiating aperture, broadband impedance matching of the SIW horn can be realized. Then, a pure dielectric near-field CP polarizer is designed and placed in front of the horn to obtain broadband CP radiation. The polarizer is designed to feature inhomogeneous property for different polarization orientation illuminations. With this property, 90° phase difference for a pair of orthogonal linearly polarized waves can be realized. Two methods are utilized to analyze the inhomogeneous property of the polarizer and to provide detailed parameter estimation steps/formulas. The effects of polarizer size and oblique incidence are also studied, and a very wide 3 dB axial-ratio beamwidth of 104° is achieved. Measured results indicate that the proposed CP SIW horn can obtain a matching bandwidth greater than 40% (22–34 GHz) and a CP radiation bandwidth of 30% (22–29.8 GHz). Simple structure and wideband CP performance make it an attractive candidate for broadband millimeter-wave applications.

The reflection and absorption characteristics of one-dimensional ternary plasma photonic crystals irradiated by TE and TM waves

The present study is aimed to investigate the reflection and absorption of electromagnetic waves propagating through one-dimensional ternary plasma photonic crystals (TPPCs) using transfer matrix method. Two different configurations of ternary plasma photonic crystal structures are considered. In the first configuration, unit cells contain plasma1-dielectric-plasma2 layers (P1DP2); while the second configuration is composed unit cells included of dielectric1-plasma-dielectric2 layers (D1PD2). In this structure the plasma is considered cold collisional.The effects of normal and oblique incidence of the monochromatic electromagnetic waves on photonic band gap of the TPPC, will be presented. In addition, the reflectance and absorbance coefficients of electromagnetic wave incident to the TPPC have been calculated. We will show plasma photonic crystal presented in this work, has the great potential to change the optical properties. By varying different parameters, the reflection, absorption and number and width of band gaps change. The results indicate that photonic band gap can be tuned in a desirable frequency range by adjusting the properties of plasma such as collision frequency and plasma frequency and structural characteristics of the TPPC including plasma-filling factor, the number of the cells and also permittivity of dielectric layer.

Single and multi-band electromagnetically induced transparency-like effects with a four-fold symmetric metamaterial design

In this study classical analogues of single and multi-band electromagnetically induced transparency in metamaterials are numerically and experimentally demonstrated. The unit cells of the two single-band electromagnetically induced transparency-like metamaterials are composed of a Jerusalem cross resonator and four spiral resonators, acting as bright and quasi-dark resonator, respectively. Polarization independent slow light response with transparencies exceeding 80% and group indices more than 100 and 50 are obtained for the proposed first and second electromagnetically induced transparency-like metamaterials, respectively. Supercell method is adopted to achieve polarization independent dual-band electromagnetically induced transparency-like behaviour by combining the unit cells of the designed two electromagnetically induced transparency-like metamaterials in four-fold symmetry. High group indices at the three transmission peaks are obtained with group index values of 114, 127 and 46. Since the third transmission band is not due to classical analogue of electromagnetically induced transparency, a comparison of slow light feature between two transmission bands of different origin is given. The effect of oblique incidence is also investigated and it has been found that the bandwidth and group index properties show opposite behaviour under orthogonal polarizations. Numerical results are supported with experimental measurements for the single and dual-band electromagnetically induced transparency-like metamaterials. The results may be important for practically designing multi-band polarization independent electromagnetically induced transparency-like metamaterials, which have potential applications in multi-frequency filtering, enhanced sensing and multi-band slow light devices.

Study on dynamic response of slope under obliquely incident SV-wave

The change of the incident angle of the seismic wave will lead to the change of the mode of action of the earthquake, which will affect the dynamic response of the slope.In order to study the effect of oblique incidence of seismic SV wave on the dynamic response of rock slope, the problem of seismic fluctuation is transformed into wave source problem. The author uses the viscoelastic artificial boundary to simulate the scattering wave field and applys the equivalent loads to the boundary nodes, which realize the fluctuation input of obliquely incident seismic wave. The semi-infinite space numerical example verifies the validity and accuracy of the method. The results show that the angle of incidence and slope angle has a great impact on seismic dynamic response of slope surface. When the SV wave is incident obliquely, the peak ground acceleration of the rock slope gradually increases with the incident angle increasing, and the peak ground acceleration near the top of the slope increases with the increase of slope angle. The results of this paper can provide important reference for seismic stability analysis of slope.

Energy losses and transition radiation in graphene traversed by a fast charged particle under oblique incidence

We perform fully relativistic calculations of the energy loss channels for a charged particle traversing a single layer of graphene under oblique incidence in a setting pertinent to a scanning transmission electron microscope (STEM), where we distinguish between the energy deposited in graphene in the form of electronic excitations (Ohmic loss) and the energy emitted in the far field in the form of transition radiation (TR). Our formulation of the problem uses a definition of two in-plane, dielectric functions of graphene, which describe the longitudinal and transverse excitation processes that contribute separately to those two energy loss channels. Using several models for the electric conductivity of graphene as the input in those dielectric functions enables us to discuss the effects of oblique incidence on several processes in a broad range of frequencies, from the terahertz (THz) to the ultraviolet (UV). In particular, at the THz frequencies, we demonstrate that the nonlocal effect in the graphene's conductivity is not important in the retarded regime, and we show that the longitudinal and transverse contributions to the emitted TR spectra exhibit strongly anisotropic angular patterns that are readily distinguishable in a cathodoluminescence measurement in a STEM. Moreover, we explore the possibility of exciting the so-called transverse mode in the optical response of graphene at the mid-infrared (MIR) range of frequencies by means of a fast charged particle under oblique incidence. Finally, we demonstrate that, aside from the usual high-energy peaks in the longitudinal contribution to the Ohmic energy loss in the MIR to the UV frequency range, there may arise strongly directional features in the in-plane distribution of the transverse contribution to the Ohmic energy loss for an oblique trajectory, which could be possibly observed via momentum- and angle-resolved electron energy loss spectroscopy of graphene in STEM.