Incidence Angle Of Rays Research Articles

Characterization of sound absorption by a foliage hedge at oblique incidence

Global warming requires public authorities to introduce legislation to protect urban air quality. Among existing environmental solutions, green walls meet this objective by reducing micro-particles, while improving biodiversity, sustainable development, thermal aspects and noise reduction. Numerous studies have demonstrated the noise-reducing benefits of vegetation. Despite the many published works on street modelling, most of them do not consider the effect of the incidence angle of rays on green walls. However, this can have very significant effects on wave absorption. The impact of the incidence angle of a sound wave passing through a foliage media on acoustic absorption is proposed in this paper by considering the Horoshenkov-Miki model. The effective parameters (density and compressibility) of a foliage sample for several leaves arrangements are first compared with those obtained experimentally by the transfer matrix method. These parameters are then used to map the absorption coefficient of this media as a function of the incidence angle.

Study on Characteristics of Epoxy Resin-Based Plastic Scintillators for Detectors with Simulation Using Monte Carlo Code

Abstract To determine the presence of radioactive materials emitting gamma rays entering or exiting nuclear facilities, ports, airports, international borders, or other strategic locations, radiation portal monitors (RPMs) capable of detecting such gamma radiation need to be installed in these places. National Research and Innovation Agency of Indonesia (BRIN) is currently developing RPMs with detector components made of plastic scintillator based on epoxy resin and augmented with aromatic fluorescent materials to produce visible light, which is the working range of the photomultiplier tube (PMT) or silicon photomultiplier (SiPM). This research aims to study the characteristics of the gamma photon radiation energy spectrum from Co-60, Cs-137, and Ir-192 sources in an epoxy resin plastic scintillator and study the absorbed dose of the scintillator to gamma photon radiation energy from Co-60, Cs-137, and Ir-192 sources as a function of source distance and incidence angle of gamma rays with simulations using the MCNPX code. The scintillator is modeled in the form of a cylinder with a diameter of 5 cm and a height of 5 cm. To simulate the gamma photon radiation energy spectrum in the scintillator, the F4 tally was used and to simulate the scintillator absorbed dose, the F6 tally was used. This simulation used gamma sources of Co-60, Cs-137, and Ir-192 of 1 mCi each. These characteristics of the epoxy resin plastic scintillator have been successfully simulated. Data on the characteristics of epoxy resin plastic scintillators is important to know and study as supporting data in making plastic detectors as part of the manufacture and development of RPM.

Seismic Anisotropy Tomography and Mantle Dynamics of Central‐Eastern USA

AbstractWe present high‐resolution 3‐D tomographic models of isotropic P‐wave velocity (Vp), azimuthal anisotropy, and radial anisotropy down to 1,300 km depth beneath the central and eastern United States (CEUS), which are obtained by inverting a great number of local and teleseismic data and making a whole‐mantle correction to teleseismic travel‐time data recorded by the USArray. Trade‐offs between azimuthal and radial anisotropies occur due to the correlation between the azimuthal and incidence angles of seismic rays, but the use of uniform and crisscrossing rays can reduce the trade‐off effect. Our tomographic images reveal the North American Craton with layered anisotropy and strong anisotropies in the lower mantle related to the deeply subducted Farallon slab and passage of the Bermuda hotspot. In the upper mantle, low‐velocity anomalies with significant seismic anisotropy are revealed beneath three intraplate seismic zones in New Madrid, East Tennessee, and South Carolina, suggesting that hot and wet mantle upwelling occurs under the seismic zones, and the related fluids affect the earthquake generation. The most important dynamic processes in the mantle beneath the CEUS are the deep subduction of the Farallon plate and the passage of the Bermuda hotspot, which have caused strong structural heterogeneities, seismic anisotropy, as well as thermal anomalies and fluids that contributed to the formation of intraplate seismic zones in the CEUS.

Sound Propagation with Undulating Bottom in Shallow Water

An undulating bottom in shallow water has a significant effect on sound propagation. An acoustic propagation experiment was carried out in the East China Sea in 2020. Measurements along two separate propagation tracks with flat and undulating bottoms were obtained. Abnormal transmission losses (TLs) were observed along the track with the undulating bottom. By using the parabolic equation model RAM and ray theory, these abnormal TLs and the distribution of the sound field energy were analyzed. Numerical simulations indicate that under the shallow water condition with a negative thermocline and for a high frequency (1000 Hz), the incidence and reflection angles of sound rays on the sea bottom are changed due to the undulating sea bottom. The larger the inclination angle of the undulating bottom, the greater the grazing angle changes. These angles changes lead to different sound propagation paths for the undulating bottom and the flat bottom, resulting in the difference of TLs at a certain distance and depth. The undulating bottom will cause energy convergence in the mixed layer when the source and receiver locate above the thermocline.

A new range‐only measurement‐based glass line feature extraction method

This letter addresses a new range-only measurement-based glass line feature extraction method, which allows a low-cost light detection and ranging (LiDAR) sensor to detect glass-like objects without intensity and multi-echo data. The principle that the emitted LiDAR ray incidence angle with respect to a glass surface is close to 0° is concerned. The geometric relationship between the sensor and glass objects is also considered for successful glass feature extraction. The extracted features are accumulated and reformulated for the generation of glass line features using the RANdom SAmple Consensus algorithm (RANSAC). Two experiments with different robot paths were conducted in a glass environment. The results showed that the proposed method accurately represented glass objects without any false-positive glass feature.

Monte Carlo simulation of reflection effects of multi-element materials on gamma rays

To study the effects of the gamma reflection of multi-element materials, gamma ray transport models of single-element materials, such as iron and lead, and multi-element materials, such as polyethylene and ordinary concrete, were established in this study. Relationships among the albedo factors of the gamma photons and energies and average energy of the reflected gamma rays by material type, material thickness, incident gamma energy, and incidence angle of gamma rays were obtained by Monte Carlo simulation. The results show that the albedo factors of single-element and multi-element materials increase rapidly with an increase in the material thickness. When the thickness of the material increases to a certain value, the albedo factors do not increase further but rather tend to the saturation value. The saturation values for the albedo factors of the gamma photons, and energies and the reflection thickness are related not only to the type of material but also to the incident gamma energy and incidence angle of the gamma rays. At a given incident gamma energy, which is between 0.2 and 2.5 MeV, the smaller the effective atomic number of the multi-element material is, the higher the saturation values of the albedo factors are. The larger the incidence angle of the gamma ray is, the greater the saturation value of the gamma albedo factor, saturation reflection thickness, and average saturation energy of the reflected gamma photons are.

Factors Related to Successful Energy Transmission of Focused Ultrasound through a Skull : A Study in Human Cadavers and Its Comparison with Clinical Experiences.

ObjectiveAlthough magnetic resonance guided focused ultrasound (MRgFUS) has been used as minimally invasive and effective neurosurgical treatment, it exhibits some limitations, mainly related to acoustic properties of the skull barrier. This study was undertaken to identify skull characteristics that contribute to optimal ultrasonic energy transmission for MRgFUS procedures. MethodsFor ex vivo skull experiments, various acoustic fields were measured under different conditions, using five non-embalmed cadaver skulls. For clinical skull analyses, brain computed tomography data of 46 patients who underwent MRgFUS ablations (18 unilateral thalamotomy, nine unilateral pallidotomy, and 19 bilateral capsulotomy) were retrospectively reviewed. Patients' skull factors and sonication parameters were comparatively analyzed with respect to the cadaveric skulls. ResultsSkull experiments identified three important factors related skull penetration of ultrasound, including skull density ratio (SDR), skull volume, and incidence angle of the acoustic rays against the skull surface. In clinical results, SDR and skull volume correlated with maximal temperature (Tmax) and energy requirement to achieve Tmax (p<0.05). In addition, considering the incidence angle determined by brain target location, less energy was required to reach Tmax in the central, rather than lateral targets particularly when compared between thalamotomy and capsulotomy (p<0.05). ConclusionThis study reconfirmed previously identified skull factors, including SDR and skull volume, for successful MRgFUS; it identified an additional factor, incidence angle of acoustic rays against the skull surface. To guarantee successful transcranial MRgFUS treatment without suffering these various skull issues, further technical improvements are required.

The role of incidence angle in the laser ablation of a planar target

The effect of the laser ray incidence angle on the mass ablation rate and ablation pressure of planar inertial confinement fusion (ICF) targets is explored. In this work, a modified version of the textbook model of laser ablation [Manheimer et al., Phys. Fluids 25, 1644 (1982)] is used to demonstrate that the mass ablation rate and ablation pressure scale with the 4/3 and 2/3 power of the cosine of the laser ray incidence angle relative to the target normal. Using an idealized planar model of ablation, it is demonstrated that constant irradiance is insufficient to produce similar velocities of a target when comparing cases driven at different incidence angles. Additionally, the effect of the incidence angle on the absorption fraction is demonstrated and it is shown that a longer duration is needed to achieve maximum absorption for greater angles. This further affects the mass ablation rate and ablation pressure in the first nanosecond of ablation. These results, when extrapolated, may provide insight into the variation of drive conditions encountered due to incidence in polar direct drive ICF.

Effects of deformation of cylindrical compound parabolic concentrator (CPC) on concentration characteristics

Compound parabolic concentrators (CPC) have immense potential for middle-and-low temperature heat collection of solar energy. In this study, the propagation process of solar radiation rays in a CPC–tubular solar collector was simulated using an in-house MATLAB code by the Monte Carlo ray tracing (MCRT) method. The effects of ray incidence angle, CPC concentration ratio, and truncation residual ratio on the heat flux distribution on the tubular heat receiver were analyzed. Moreover, the effects of CPC deformations on concentration characteristics were analyzed, involving the rotation and translation of the reflective surface, the truncation of the involute starting point, and the position offset of the heat receiver. The heat flux distribution exhibited two evident peaks on the heat receiver external surface due to the concentration effect of the CPC. A small internal rotation, a small internal or external translation of the reflective surface, and the truncation of the involute starting point had mere effect on the heat flux distribution on the heat receiver. Therefore, the reflective surface can be allowed to have certain translation and internal rotation when machining a CPC. The downward, rightward, and leftward offsets of heat receivers should be avoided in the assembly of heat receivers and CPCs.

A Theoretical Study on Performance and Design Optimization of Linear Dielectric Compound Parabolic Concentrating Photovoltaic Systems

To investigate solar leakage and effects of the geometry of linear dielectric compound parabolic concentrator with a restricted exit angle (DCPC-θa/θe) on the performance of DCPC-θa/θe -based photovoltaic systems (DCPV-θa/θe), a three-dimensional radiation transfer model based on solar geometry and vector algebra is suggested. Analysis shows that the annual radiation loss due to leakage is sensitive to the geometry of DCPCs and tilt-angle adjustment strategy, and the optimal θe,opt for minimizing annual leakage is the one that makes the incidence angle of solar rays on the plane wall equal to the critical incidence angle for total internal reflection at solar-noon in solstices and days when tilt-angle adjustment from site latitude is made for DCPV with the aperture’s tilt-angle being yearly fixed, and adjusted two and four times, respectively. It is found that annual radiation leakage is considerable small, for DCPVs with θe &lt; θe,opt, almost all leaked radiation comes from sky diffuse radiation, whereas for θe = 90°, most of leakage is attributed to direct sunlight. As compared to similar non-concentrating solar cells, more radiation arrives annually on solar cells of DCPV-θa/θe at small angles thanks to refraction of radiation on the aperture, hence, under same operation conditions, the annual average photovoltaic efficiency of solar cells for concentrated radiation is even higher. Analysis also shows that the power increase of DCPVs, being much less than the geometric concentration of DCPCs (Ct), is mainly attributable to optical loss due to absorption of solar rays on the way to the solar cells, and the power loss due to leakage of radiation is not significant. From the point of annual electricity generation, for full DCPVs with a given θa, DCPV-θa/90 are favorable, and for truncated DCPVs with given θa and Ct, DCPVs with θe &lt; 90 are favorable; whereas from the point of contribution per unit volume of dielectric to the annual electricity generation, the situation is reversed.

Investigation on underwater positioning stochastic model based on acoustic ray incidence angle

High-precision underwater positioning requires more accurate stochastic model. The commonly used equal weight stochastic model (EWSM) cannot be effective in precise underwater positioning process under the assumption of equal-precision observation. In this paper, inaccurate stochastic model effect on the positioning precision is analyzed and a novel acoustic ray incidence angle stochastic model (IASM) is proposed by taking the ranging error and the uncorrected acoustic ray bending error into consideration to improve positioning accuracy. The performance of both EWSM and IASM involving four different forms (the general proportional form, the cosine form, the exponent form and the piecewise cosine form) is tested by the simulation and experiment. The simulation results show that positioning accuracy for underwater static objects is 0.386 m when adopting EWSM while positioning accuracy is 0.334 m, 0.196 m, 0.318 m and 0.091 m when adopting four forms of IASM respectively and sequentially. The experiment results show that the positioning accuracy can be superiorly improved from 1.187 m in EWSM scheme to 0.991 m based on IASM in piecewise cosine form. It’s obvious that the novel IASM can perform better than conventional EWSM in terms of positioning accuracy according to testing results.

Performance comparison of CPCs with and without exit angle restriction for concentrating radiation on solar cells

Abstract To perform this comparison, the compound parabolic concentrator with a restricted exit angle of 65° (CPC-65) and the one without exit angle restriction (CPC-90) were fabricated and tested for concentrating radiation on multi-crystalline solar cells. Both CPC-65 and CPC-90 are identical in the acceptance half-angle (20°) and geometrical concentration factor (2×). Theoretical calculations showed that CPC-90 based PV system (CPV-90) annually concentrated about 3–5% more radiation on solar cells as compared to CPC-65 based PV system (CPV-65). For CPV-65, all radiation would arrive on the solar cells at the incidence angle less than 65°, but for CPV-90, about 8–10% of annual collectible radiation would arrive on solar cells at the incidence angle larger than 65°. Measurements at outdoor conditions showed that the CPV-65 performed slightly better than CPV-90 in terms of short-circuit current and power output as the projection incidence angle of solar rays on the cross-section of CPC-troughs (θp) less than the acceptance half-angle, otherwise the CPV-90 did better. Compared to CPV-90, the power output at maximum power points from CPV-65 were slightly higher, and increases of 2.1%, 5.4% and 8.17% were measured for θp = 0°, 10° and 16°, respectively. Analysis indicated that effect of solar flux distribution over solar cells on power output of both CPVs was almost identical and insignificant, and the CPV-65 performed slightly but insignificantly better than the CPV-90 in terms of annual power output except in areas with poor solar resources where the annual power output from both systems was almost identical.

Optical performance of CPCs for concentrating solar radiation on flat receivers with a restricted incidence angle

In some applications of compound parabolic concentrators (CPCs), the incidence angle of solar rays on the absorber is restricted and must be less than a specified value (θe) for efficient energy conversion or transfer. For a flat receiver with a restricted incidence angle (RWARIA, in short), two ideal concentrators designed based on one-sided flat absorber can be employed for radiation concentration: one is the CPC without exit angle restriction (CPC-1), and another is the CPC with a restricted exit angle (CPC-2). In this work, the angular dependence of optical efficiency factor of both CPC-1 and CPC-2 for concentrating radiation on the RWARIA was derived, and a mathematical procedure to estimate daily radiation accepted by the RWARIA by using east-west oriented CPC-1 and CPC-2 was suggested based on the solar geometry and monthly horizontal radiation. Results by numerical calculations show that, for fixed full CPC-1 and CPC-2 with identical acceptance half-angle (θa), the CPC-2 is slightly more efficient than CPC-1 for concentration radiation on the RWARIA except periods of about 30 days before and after both equinoxes; whereas for fixed truncated CPC-1 and CPC-2 with identical geometric concentration factor (Ct) and θa, the CPC-2 is always more efficient. Results also indicate that, for the case of the tilt-angle of the aperture of CPCs being yearly adjusted four times at three tilts, full CPC-2 is less but truncated CPC-2 is more efficient than CPC-1 for concentrating radiation. In practical applications, CPCs are usually truncated due to less efficient of top portion of a CPC reflector for radiation concentration and less reflector material use, therefore, the CPC-2 is more favorable and advisable for concentrating radiation on the RWARIA.

Irradiation Distribution on Solar Cells inside CPCs with a Restricted Exit Angle

In this work, irradiation distribution on the base of ideal two-dimensional CPCs with and without a restricted exit angle, to which solar cells are attached, are analyzed by the ray-tracing technique. Results show that, given an acceptance half-angle (Θa), for CPCs without a restricted exit angle (CPC-1), radiation flux distribution on the base depends on the incidence angle of solar rays (Θ ); whereas for CPCs with a restricted exit angle (CPC-2), the flux distribution depends on and the restricted exit angle (Θe). For both CPC-1 and 2 with identical geometric concentration factor (Ct=2) and acceptance half-angle ( Θa=20), the peak flux concentration ratio on the base of CPC-2 with =65o decreases about 43%, 30% and 49% for the radiation at the incident angle of 0o, 10o and 18o, respectively, as compared to CPC-1. This implies that solar flux distribution on the base of CPC-2 is more uniform, thus, more efficient for photovoltaic conversion as compared with CPC-1.

Optical efficiency study of PV Crossed Compound Parabolic Concentrator

Static solar concentrators present a solution to the challenge of reducing the cost of Building Integrated Photovoltaic (BIPV) by reducing the area of solar cells. In this study a 3-D ray trace code has been developed using MATLAB in order to determine the theoretical optical efficiency and the optical flux distribution at the photovoltaic cell of a 3-D Crossed Compound Parabolic Concentrator (CCPC) for different incidence angles of light rays. It was found that the CCPC with a concentration ratio of 3.6× represents an improved geometry compared to a 3-D Compound Parabolic Concentrator (CPC) for the use as a static solar concentrator. The CCPC has a maximum optical efficiency of 95%, in line with the optical efficiency of the 3-D CPC, with the added advantage of having a square entry and exit aperture. A series of preliminary experimental measurements were taken on a setup of nine solar cells. The experimental results provide validation of the MATLAB code developed, showing a deviation of 12±2% from the simulation results, thus confirming that the code can be used to investigate different concentration ratios of the CCPC.

Evaluation of global, photosynthetically active radiation and diffuse radiation transmission of agricultural screens

Transmittance of a material depends on the type of radiation impinging on the material (direct or diffuse), the angle of incidence of the sun’s rays (in direct radiation conditions) and the structure and characteristics of the material itself. The aim of this study was to evaluate the performance of nine agricultural screens of different densities, colours, thread diameters and porosities. A simple metal frame was used to quantify global, diffuse and photosynthetically active radiation (PAR) transmission to determine their transmittance values (as a function of the incidence angle of solar rays in direct radiation conditions) for global radiation and PAR, as well as the diffuse radiation transmitted characteristics of the screens (ratio of diffuse radiation to global radiation transmitted by screens). Non-coloured (translucent) screens contributed to a higher and more efficient proportion of diffuse radiation (Di/Gi ≈ 90%). The green screen behaved similarly to the non-coloured 20×10 type as far as global radiation was concerned, although the PAR transmittance values were lower (up to 12.4% at 15º). Variation in transmission according to diameter and density of the threads was greatest in the black screens. The non-coloured-thread screens may be the best option for maximising the transmission of diffuse radiation and the 6×6 green screen for vegetables cultivation during the summer in inland areas with latitudes close to 36ºN.

Errors in GNSS radio occultation data: relevance of the measurement geometry and obliquity of profiles

Abstract. Atmospheric profiles retrieved from GNSS (Global Navigation Satellite System) radio occultation (RO) measurements are increasingly used to validate other measurement data. For this purpose it is important to be aware of the characteristics of RO measurements. RO data are frequently compared with vertical reference profiles, but the RO method does not provide vertical scans through the atmosphere. The average elevation angle of the tangent point trajectory (which would be 90° for a vertical scan) is about 40° at altitudes above 70 km, decreasing to about 25° at 20 km and to less than 5° below 3 km. In an atmosphere with high horizontal variability we can thus expect noticeable representativeness errors if the retrieved profiles are compared with vertical reference profiles. We have performed an end-to-end simulation study using high-resolution analysis fields (T799L91) from the European Centre for Medium-Range Weather Forecasts (ECMWF) to simulate a representative ensemble of RO profiles via high-precision 3-D ray tracing. Thereby we focused on the dependence of systematic and random errors on the measurement geometry, specifically on the incidence angle of the RO measurement rays with respect to the orbit plane of the receiving satellite, also termed azimuth angle, which determines the obliquity of RO profiles. We analyzed by how much errors are reduced if the reference profile is not taken vertical at the mean tangent point but along the retrieved tangent point trajectory (TPT) of the RO profile. The exact TPT can only be determined by performing ray tracing, but our results confirm that the retrieved TPT – calculated from observed impact parameters – is a very good approximation to the "true" one. Systematic and random errors in RO data increase with increasing azimuth angle, less if the TPT is properly taken in to account, since the increasing obliquity of the RO profiles leads to an increasing sensitivity to departures from horizontal symmetry. Up to an azimuth angle of 30°, however, this effect is small, even if the RO profiles are assumed to be vertical. For applications requiring highest accuracy and precision it is advisable to exclude RO profiles with ray incidence angles beyond an azimuth of 50°. Errors in retrieved atmospheric profiles decrease significantly, by up to a factor of 2, if the RO data are exploited along the retrieved TPT. The tangent point trajectory of RO profiles should therefore be exploited whenever this is possible.

An Overview of Ultra-Wide-Band Systems With MIMO

Ultra-wide-band (UWB) technology combined with multiple transmit and receive antennas (MIMO) is a viable way to achieve data rates of more than 1 Gb/s for wireless communications. UWB is typically applied to short-range and therefore mainly indoor communications in environments characterized usually by dense multipath propagation. For this type of environment, MIMO systems allow for a substantial increase of spectral efficiency by exploiting the inherent array gain and spatial multiplexing gain of the systems. In this paper, we provide a brief overview for UWB-MIMO wireless technology. The overview covers channel capacity, space-time coding (STC), and beamforming. It is shown that the spectral efficiency is increased logarithmically and linearly <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">,</i> respectively, for single transmit and multiple receive antennas (SIMO) and MIMO systems. For multiple transmit and single receive antenna (MISO) systems, a threshold for the data transmission rate exists such that the spatial multiplexing gain can be obtained if the data rate is lower than this threshold, but it is not beneficial to deploy multiple transmit antennas if the required data rate is higher than the threshold. Two STC schemes for UWB-MIMO are briefly discussed, and their performance comparison is presented. A discussion about antenna selection is also presented, and the performance comparison between antenna selection and equal gain combiner is provided showing the diversity gain for some scenarios. For the beamforming, it is shown that the optimal beamformer is obtained if all the weighting filters in each antenna branch are identical. About the optimal beamformer, it is found that the amplitude of the side lobe is independent of the ray incidence angle, and the amplitude of the main lobe is increased by a fold of the element number in the array. Three kinds of beam patterns are defined, and the beamwidth of the main lobe is given. Experimental results based on an offline testbed are provided to verify some analytical results presented in this paper. Since UWB-MIMO is still in its research infancy, the aim of this paper is to present some first results on spatial multiplexing, STC, and beamforming to illustrate the potential of UWB-MIMO.

Aberration-free imaging for light and electrons

The equations for refraction of either the extraordinary wave of light or the wavefunction of an electron at a planar boundary between two misoriented uniaxially anisotropic materials are shown via raytracing to yield a transverse displacement of the object point. The displacement is independent of ray incidence angle and is thus free from spherical aberration, yielding a perfect virtual image which can have applications in birefringent optics. The general conditions for this aberration-free imaging are found to be identical to those required for amphoteric total refraction.

Transmission coefficient of the transparent insulation of flat diffuse solar radiation heating systems

A method is proposed for calculating the transmission coefficient of the transparent insulation of the diffuse solar radiation heating systems in terms of the equivalent value of the direct solar radiation ray incidence angle.