Directions Of Rays Research Articles

A novel method for measuring the direction and angle of central ray and predicting rotation centre via panorama phantom.

The aim of this study is to propose and evaluate a novel method for measuring the central ray direction and detecting the rotation centre of panoramic radiography using the panorama phantom. To determine the central ray direction, 2 points passing through the same x-coordinate in a panoramic radiograph were identified and connected. The angles formed by the central ray with the midline and the angle to the arch form were measured using mathematical calculations. Further, by analysing the continuous changes in the central ray obtained in this manner, the movement of the rotation centre was detected and visualized. The angle between the central ray and the midline exhibited a progressive decrease from the anterior to the posterior direction. With regards to the arch form, the angle of the central ray exhibited an increasing pattern as it moved from the anterior to the posterior direction, culminating in its peak value at the lower second premolar cusp region, followed by a consistent decrease. The rotation centre approximately started from the distolateral aspect of the coronoid process and then anteromedially moved to the midline in a curved line passing between the mandibular notch and coronoid process. By using the panorama phantom, we successfully obtained the central ray direction and detected the rotation centre of the panoramic radiography.

Analytical form of the refocused images from correlation plenoptic imaging

Correlation plenoptic imaging (CPI) is emerging as a promising approach to light-field imaging (LFI), a technique for concurrently measuring light intensity distribution and propagation direction of light rays from a 3D scene. LFI thus enables single-shot 3D imaging, offering rapid volumetric reconstruction. The optical performance of traditional LFI, however, is limited by a micro-lens array, causing a decline in resolution as 3D capabilities improve. CPI overcomes these limitation by measuring photon number correlations on two photodetectors with spatial resolution, in a lenslet-free design, so that the correlation function can be decoded in post-processing to reconstruct high-resolution images. In this paper, we derive the analytical expression of CPI images reconstructed through refocusing, addressing the previously unknown mathematical relationship between object shape and its final image. We show that refocused images are not limited by numerical aperture-induced blurring, as in conventional imaging. Rather, the image features of CPI can be explained through an analogy with imaging systems illuminated by spatially coherent light.

Properties of the hybrid solutions for a generalized (3 + 1)-dimensional KP equation

The Kadomtsev-Petviashvili (KP) equation is instrumental in characterizing nonlinear wave phenomena in fluid dynamics. With the incorporation of three-dimensional disturbances, the (3+1)-dimensional KP equation emerges. In this study, we employ the Hirota bilinear method to investigate a (3+1)-dimensional KP equation. We successfully derive both lump and lump-chain solutions for this equation. The characteristics of the resulting lump are thoroughly examined. It is observed that those lumps propagate along a specific ray direction, with the origin of these rays dependent on the imaginary part of σˆjk=σj−σk with 1≤j,k≤3 and j≠k. We have simultaneously obtained the propagation direction of these rays. The periodicity of those lumps is denoted as Tjk dependent on spectrum parameter. Furthermore, we explore two potential lines, including the characteristic line associated with the lumps, to gain a deeper understanding of the nonlinear waves controlled by this system.

A high-precision localization method for underwater targets incorporating direct path recognition and sound rays bending compensation

A high-precision localization method for underwater targets incorporating direct path recognition and sound rays bending compensation

Closing the Net on Transient Sources of Ultrahigh-energy Cosmic Rays

The arrival directions of ultrahigh-energy cosmic rays (UHECRs) observed above 4 × 1019 eV provide evidence of localized excesses that are key to identifying their sources. We leverage the 3D matter distribution from optical and infrared surveys as a density model of UHECR sources, which are considered to be transient. Agreement of the sky model with UHECR data imposes constraints on both the emission rate per unit matter and the time spread induced by encountered turbulent magnetic fields. Based on radio measurements of cosmic magnetism, we identify the Local Sheet as the magnetized structure responsible for the kiloyear duration of UHECR bursts for an observer on Earth and find that the turbulence amplitude must be within 0.5–20 nG for a coherence length of 10 kpc. At the same time, the burst-rate density must be above 50 Gpc−3 yr−1 for Local Sheet galaxies to reproduce the UHECR excesses and below 5000 Gpc−3 yr−1 (30,000 Gpc−3 yr−1) for the Milky Way (Local Group galaxies) not to outshine other galaxies. For the transient emissions of protons and nuclei to match the energy spectra of UHECRs, the kinetic energy of the outflows responsible for UHECR acceleration must be below 4 × 1054 erg and above 5 × 1050 erg (2 × 1049 erg) if we consider the Milky Way (or not). The only stellar-sized transients that satisfy both Hillas’ and our criteria are long-duration gamma-ray bursts.

Interactive Volume Visualization via Multi-Resolution Hash Encoding Based Neural Representation.

Implicit neural networks have demonstrated immense potential in compressing volume data for visualization. However, despite their advantages, the high costs of training and inference have thus far limited their application to offline data processing and non-interactive rendering. In this article, we present a novel solution that leverages modern GPU tensor cores, a well-implemented CUDA machine learning framework, an optimized global-illumination-capable volume rendering algorithm, and a suitable acceleration data structure to enable real-time direct ray tracing of volumetric neural representations. Our approach produces high-fidelity neural representations with a peak signal-to-noise ratio (PSNR) exceeding 30 dB, while reducing their size by up to three orders of magnitude. Remarkably, we show that the entire training step can fit within a rendering loop, bypassing the need for pre-training. Additionally, we introduce an efficient out-of-core training strategy to support extreme-scale volume data, making it possible for our volumetric neural representation training to scale up to terascale on a workstation with an NVIDIA RTX 3090 GPU. Our method significantly outperforms state-of-the-art techniques in terms of training time, reconstruction quality, and rendering performance, making it an ideal choice for applications where fast and accurate visualization of large-scale volume data is paramount.

Combined Effects of Tetracycline and Copper Ion on Microorganisms During the Biological Phosphorus Removal.

Tetracycline and copper ion are common pollutants in wastewater, and the effects of mixed pollutants on microorganisms in wastewater biological treatment have been less studied. In order to reveal the effects of mixed pollutants of tetracycline and copper ion on the microorganisms during the biological phosphorus removal, three ratios of tetracycline and copper ions were designed by the direct equipartition ray method. The relative abundance and diversity of microbial community were investigated, and the microbial interactions were revealed through microbiological methods. The results demonstrated that, for three different ratios, the inhibitory effect of specific phosphorus uptake rate became more significant with the increase of the tetracycline-copper ions concentration and the reaction time. The microbial community decreased with the increase of the proportion of tetracycline in different ratios. The relative abundance of Acinetobacter decreased with the increase of the proportion of tetracycline, while the relative abundance of Ca.Competibacter was higher under the conditions of low mixtures concentrations. Positive interactions and symbiotic relationships among microorganisms were predominant for three different ratios. However, as the proportion of tetracycline increased, the community structure of microorganisms shifted from phosphate-accumulating organisms to glycogen accumulating organisms and denitrifying bacteria. This study can provide a reference for the effect of mixed pollutants on microorganisms and the mechanism of wastewater treatment.

Imaging Seafloor Features Using Multipath Arrival Structures

In this paper, we propose an imaging method for seafloor features based on multipath arrival structures. The bistatic sonar system employed consists of a vertical transmitting array and a horizontal towed array. The conventional back projection (BP) method, which considers the direct path from the source to the seafloor scatterer and then to the receiver, is used in this system. However, discrepancies between the calculated delay values and the actual propagation delay result in projection deviations and offsets in the seafloor features within sound intensity images. To address this issue, we analyze the multipath structures from the source to the scatterer and then to the receiver based on ray theory. The delay at each grid is calculated using different multipaths, considering the distances from the seafloor grids to the source and the receiver. In the direct zone, the delay is determined using the direct ray and the surface reflection ray, while in the bottom bounce area, the delay is calculated using the bottom–surface reflection ray and the surface–bottom–surface reflection ray. Numerical simulations and experimental results demonstrate that the proposed method rectifies the delay calculation issues inherent in the conventional method. This adjustment enhances the accuracy of the projection, thereby improving the imaging quality of seafloor features.

Zemax Modeling Of A Self-Aligned Focusing Schlieren System With Simulated Compressible Flow

A self-aligned focusing schlieren system is simulated in the ANSYS Zemax OpticStudio software environment. The model uses a custom scatter-defining dynamic link library on the retroreflective background in order to scatter rays in the direction of the incident ray rather than the specular ray. Simulated compressible flow refractive index fields are imported into Zemax by use of the grid gradient object and a workaround to the maximum point limit is introduced. The Ronchi ruling is built as a high resolution bitmap image in MATLAB and set in Zemax as a slide object allowing the bitmap image to either transmit or terminate rays at each line pair. The Zemax simulations are compared to computational numerical schlieren and experimental conventional, path-integrated schlieren results from a hypersonic stagnation point injection flow configuration and an experimental image of a shock wave from a laser-induced breakdown. In the stagnation point injection simulations, the Zemax schlieren images capture complex flow features such as the Mach disk, shear layers, contact surface, and bow shock well, but contains long, curved features (striations) between the model and the bow shock that are not present in the synthetic schlieren image from the CFD or the experimental image. The image from Zemax of the spark-induced shock wave captures the shape and curvature of the shock but appears blurry due to grid discretization in the computational data.

Spatial resolution measurement method for 3D displays from contrast modulation

Augmented Reality 3D head-up displays use a autostereoscopic 3D display as a panel. The 3D optical unit of autostereoscopic 3D displays controls the direction of the light rays in each pixel, allowing the users enjoy 3D world without glasses. However, these 3D optics cause image quality degradation. Deterioration of resolution has a serious impact on 3D image quality. Therefore, it is important to properly measure the 3D resolution according to 3D optics and analyze its impact. In this study, a method for measuring spatial resolution in 3D displays using contrast modulation is proposed. We describe a conventional 2D resolution measurement methods that are standardized. Based on the existing 2D resolution methods, we propose a 3D resolution method. The spatial and frequency signal responses of 3D displays were investigated. The first method is determined by the predominant frequency series. The second method is conducted by contrast modulation. Through experiments with 3D displays, 3D resolution was measured using the proposed method, and the relationship between the parameters and resolution of 3D optics was examined.

HF/HR VSP acquisition, processing, and interpretation in the deviated section of the high angle geothermal borehole of Grigny GGR5, targeting intra Dogger thin, porous beds.

Defining 5m thin, or even thinner, porous reservoir beds was the feasibility objective assigned to the High Frequency/High Resolution (HF/HR) look ahead VSP survey to be recorded in the deviated section of a geothermal production well drilled down to the top of the carbonate Dogger aquifer in the Paris basin, around 1500m in vertical depth, with a landing angle of 65°. The idea was to predict the depth of the first porous bed(s) to be drilled at high angle, and to determine the minimal DLS (Dog Leg Severity) to be applied by the driller after setting a production casing at the top Dogger level and changing the drilling fluid composition, so as to avoid directional drilling with sharp angles. A 50-100m vertical depth range was targeted for the acoustic impedance to be predicted below the top Dogger carbonate aquifer. Besides, a Pilot Hole (PH) was drilled prior to the high angle leg to assess with full reliability the depth of productive thin beds to be subsequently drilled at high angle. These actions were undertaken within a global R&D project named “SISMOSUB” aiming reservoir characterisation, conducted by the reservoir and drilling engineers of GEOFLUID/GPCIP, in a partnership with IFPEN, and partially financed by ADEME (French Agency for Ecological Transition). High Frequency (HF) VSP still represents a frontier seismic domain to investigate, for which technical difficulties are piling up: First, the surface fix source needs to be extremely repeatable and preferably deliver an increased amount of HF energy to compensate somehow for the higher loss of seismic amplitudes with high frequency. Second, downhole receiver tool or toolstring may not present constant vector fidelity of 3 component reception over the whole recording frequency range, mainly in high frequency, due to mechanical coupling characteristics of the VSP tool hardware and the open borehole ruggedness; in cased hole, the mechanical coupling of the VSP tool to the formation is insured by a good cementing quality between casing and borehole wall. Third, the physics of the seismic attenuation is not fully understood and depends on several factors, mainly viscoelasticity and heterogeneity, potentially variable in depth and laterally to the wellbore. Additionally, the geometrical spreading represents the main factor of amplitude decay, independent from frequency, and can be estimated at processing stage. Surprisingly, the VSP image produced underneath the deviated hole section evidenced a faulted structure. A remarkable abrupt amplitude loss of high frequencies above 120Hz occurs where the direct P-wave ray crosses one of the confirmed minor faults before reaching Total Depth (TD); secondary downgoing arrivals appear locally in depth, mainly in the high frequencies, which are not strictly parallel to the first P-wave arrival...

Coupling effects of aureomycin and zinc ion on nitrification process and nitrification enzymes during the biological nitrogen removal

Aureomycin and Zinc ion (Zn2+) are common antibiotics and heavy metals that exist in livestock wastewater. The coupling effects of Aureomycin and Zn2+ on the nitrification process and nitrification function enzymes are crucial for controlling nitrogen removal in livestock wastewater. However, rare studies were focused on the coupling effects of Aureomycin and Zn2+ on nitrification. This study employed a direct equipartition ray method to investigate the coupling effects of Aureomycin and Zn2+ on nitrification. The results suggested three different ratios of Aureomycin and Zn2+ affected nitrification performance differently. Ratio 1 and Ratio 2 exhibited a promotion effect with low concentrations and an inhibition effect with high concentrations on nitrification performance. The critical concentration for Ratio 1 and Ratio 2 were 5.00 mg L−1 and 1.90 mg L−1, respectively. Ratio 3 exhibited both time-dependent and concentration-dependent inhibitory effects on nitrification performance. The maximum inhibitory efficiency on nitrification performance was 90.0%, with a concentration of 34.5 mg L−1 at 96.0 h. The effects of binary mixture on nitrogen removal performance were attributed to the effects of binary mixture on nitrite oxidase activity. The qualitative evaluation of the concentration addition model and independent action model indicated Aureomycin and Zn2+ showed a synergistic effect with strong concentration-dependent and time-dependent in the whole concentration area. The synergistic effect of Aureomycin and Zn2+ on nitrite oxidase activity mainly depended on the concentration of Aureomycin. This study offers new insights into the effects of antibiotics and heavy metals on the biological nitrogen removal process.

Propagation of elastic waves in fibrous composite with general anisotropy from two families of obliquely inclined fibers

AbstractAn isotropic elastic solid reinforced with two families of aligned fibres behaves anisotropic to any deformation. For arbitrary orientation of fibres in either family, one set of fibres may be inclined obliquely to the aligned fibres in other family. A plane that contains the two families of aligned fibres becomes the plane of symmetry for composite material to exhibit monoclinic anisotropy. For this fibrous anisotropy, a fourth‐order elastic tensor is derived to define the constitutive relations between stress tensor and strain tensor. Components of this elastic tensor involve two Lame's moduli, eight fibroelastic coefficients and the angular deviation between two obliquely inclined fibre‐families. The velocities of bulk waves are calculated for propagation along general direction in this anisotropic composite. Propagation of surface wave is considered along the stress‐free plane boundary of anisotropic elastic half‐space. In a coordinate system with coordinate planes deviating from the plane boundary of the medium and/or plane of anisotropic symmetry, the fibrous composite is treated as triclinic for mathematical convenience. Mathematical model is derived to calculate the phase velocity of the surface wave, which varies with direction on the plane boundary. Horizontal energy flux at the boundary is calculated to determine the group velocity and ray direction of the surface wave. Effects of fibre‐orientations are analysed, numerically, on the wave velocities and ray direction of surface wave.

Light field imaging technology for virtual reality content creation: A review

AbstractThe light field (LF) imaging technique can capture 3D scene information in 4D by recording both 2D intensity and 2D direction of incoming light rays. Due to this capability, LF has shown a great interest in virtual reality (VR) and augmented reality (AR) for enhanced immersion, improved depth perception and reconstruction of realistic 3D environments. This paper presents a comprehensive review of LF imaging technology and other approaches used for VR content creation. The applications of LF technology beyond VR and AR are also discussed. The challenges and limitations of other approaches for VR content creation are examined. State‐of‐the‐art research has focused on how VR experiences benefit from LF technology and identified the challenges to creating comfortable, immersive and realistic VR content such as (1) image size and resolution, (2) processing speed, (3) precise calibration and (4) depth reconstruction. Recommendations that can be considered for creating immersive VR content are provided to enhance user experience. These recommendations aim to contribute to developing more comfortable and realistic VR content, extending the potential applications of LF imaging technology in diverse fields.

Synthesis and characterization of Fe-doped CuO nanoparticles: Catalytic efficiency in crystal violet dye degradation and exploration of electrical properties

In recent times, environmental pollution has become a pressing issue. Different methods have been developed to detach hazardous materials from H2O bodies. Among these techniques, photo-catalysis has emerged as a low-cost and advanced method. However, finding a potent photocatalyst has been a topic of considerable research. Our study prepared CuO from copper acetate using hydrothermal treatment in an autoclave at 170 ºC for 14 hours. We introduced various quantities of Fe by adding FeSO4 mixture to Cu (CH3COO)2, following the identical method for preparing CuO. The resulting precipitate was cleaned with deionized H2O and dried at 100 °C. The prepared substance was then heated at 450 ºC in a muffle furnace for 60 minutes. We characterized the manufacture of photocatalysts utilizing various techniques such as Ultraviolet (UV), FT-IR, SEM, EDX, and XRD. Our Ultraviolet (UV) spectrum analysis helped us recognize the adsorption spectroscopic analysis of un-doped and doped CuO with various ratios of Fe. FTIR spectroscopic analysis helped us identify functional groups in CuO NPs. Our XRD study showed the monoclinic composition of copper oxide nanoparticles. The SEM picture suggested that NPs exist in a spherical shape. We studied the catalytic activity of synthesized NPs concerning crystal violet (CV) colorant degradation below a direct ray of light irradiation. Our results showed that the degradation productiveness, as compared to CV colorant, was about 93.52% in 180 min. This research is of great importance in the quest for effective and sustainable solutions to environmental problems. The examination of electrical properties highlighted the promising aspects of Fe-doped CuO, particularly at 6% doping. This variant demonstrated superior dielectric parameters, lower tangent loss, semiconductor-like impedance behavior, and enhanced electrical conductivity, emphasizing its potential for applications in electrical and energy storage domains.

Spherical full-parallax light-field display using a ball of fly-eye mirror

Creating a spherical full-parallax light-field display is challenging because it is difficult to curve conventional structures, although the spherical surface is suitable for displaying 3D images with a wide viewing area. Here, we present a spherical full-parallax light-field display that consists of a specially designed disco-ball-like spherical reflective screen (a ball mirror) and a high-speed projector. The ball mirror uniaxially rotates to change the ray direction, and the synchronized projector controls the ray color. By speeding up the rotation and employing time multiplexing, the system acts as a full-parallax light-field display. We designed the system mathematically and analyzed the image quality through computer simulations. In addition, the prototype successfully displays colored 3D images and has smooth parallax in both vertical and horizontal directions.

DHR+S: distributed hybrid rendering with realistic real-time shadows for interactive thin client metaverse and game applications

Distributed hybrid rendering (DHR) is a real-time rendering approach that incorporates cloud-based ray tracing with locally rasterized graphics for interactive thin client metaverse and game applications. With cloud assistance, DHR can generate high-fidelity ray-traced graphics contents remotely and deliver them to thin clients with low graphics capability, including standalone extended reality devices and mobile phones, while maintaining interactive frame rates for users under adverse network conditions. DHR can already achieve the effect of ray-traced hard shadows that form with the occlusion of direct illumination. We enhance the realism of these shadows by softening their edges with the direction of rays traced and approximating the occlusion of indirect illumination by reconstructing ray-traced ambient occlusion with a modified version of spatiotemporal variance-guided filtering. Our technique uses only 20–30% of the bandwidth of remote rendering and is also tolerant of delays of up to 200 ms with only slight distortion to the shadows along object edges.

Combined effect of zinc and cadmium ions on nitrification performance during the biological nitrogen removal of simulated livestock breeding wastewater.

Zinc and cadmium ions are usually found in livestock breeding wastewater, and the mixed ions will have an impact on the biological nitrogen removal. Nitrification performance plays an important role in biological nitrogen removal. In order to investigate the combined effect of zinc and cadmium ions on nitrification performance and to reveal the interactions between zinc and cadmium ions, three concentration ratios of zinc and cadmium ions, as well as 18 different concentration gradients were designed with the direct equipartition ray and the dilution factor method. The effect of pollutants on the nitrification performance of biological nitrogen removal was analyzed by the nonlinear regression equation, and the concentration-addition model was conducted to probe into the relationship between the mixed pollutants and the nitrification performance. The results showed that the effect on nitrification performance increased significantly with the increase of reaction duration and pollutant concentration, which indicated that the effects are concentration-dependent and time-dependent. The concentration-addition model suggested that the interactions between zinc and cadmium ions with different concentration ratios were mainly antagonistic, and as the percentage of cadmium ions in the mixtures increased, the antagonism between the mixtures became stronger. This study will provide a relevant theoretical basis for the regulation of the ratios and concentrations of heavy metal ions during the biological treatment of livestock breeding wastewater.

Living Outside with the Sun

This paper reflects upon the history of design of outdoor living spaces, a typology that blends interior directly with landscape. In Australasia, outdoor living is a symbol of contemporary life style but it must adapt to the danger of over-exposure to the sun’s ultraviolet rays. Tempering openness to the summer sky is not just a choice but rather a survival strategy. The relationship of European descendents to the Antipodean sun has fluctuated over time. In Victorian times, hats, copious clothing and villa verandahs protected prized pale complexions. Tanned skin branded the labouring classes and the native population. In the 1920s, the ancient Greek practice of heliotherapy was hailed as beneficial for the treatment of tuberculosis. Concurrently architecture clipped verandahs and proposed open sun terraces, sometimes scantily clad by a pergola. The negative consequences of this sun-worship were not known until the 1980s when the relation between ultraviolet rays and skin cancer was made and the recognition that one in three Australasians will be affected. Living outside with the sun therefore requires modification. Sunscreen is prescribed for application every two hours; hats, clothing and sun-glasses protect the body but hinder communication between people and their surroundings. Traditional solid shade shields direct rays, but deny the warmth of the sun, which is often so welcome in temperate New Zealand. Open shade sails fail to acknowledge the fact that ultraviolet rays scatter. Living well outside is not simple.

Ultra-high-energy Cosmic-Ray Sources Can Be Gamma-Ray Dim

Ultra-high-energy cosmic rays (UHECRs), accelerated hadrons that can exceed energies of 1020 eV, are the highest-energy particles ever observed. While the sources producing UHECRs are still unknown, the Pierre Auger Observatory has detected a large-scale dipole anisotropy in the arrival directions of cosmic rays above 8 EeV. In this work, we explore whether resolved gamma-ray sources can reproduce the Auger dipole. We use various Fermi Large Area Telescope catalogs as sources of cosmic rays in CRPropa simulations. We find that in all cases, the simulated dipole has an amplitude significantly larger than that measured by Auger, even when considering large extragalactic magnetic field strengths and optimistic source weighting schemes. Our result implies that the resolved gamma-ray sources are insufficient to account for the population of sources producing the highest-energy cosmic rays, and there must exist a population of UHECR sources that lack gamma-ray emission or are unresolved by the current-generation gamma-ray telescopes.