Two-Stage Simulation for Coupling Schemes in the Device Communication using Ray Tracing and Beam Propagation Method

The authors report the design, fabrication and characterisation of a planar gradient index (GRIN) PECVD lens. The PECVD-based helicon plasma reactor was used to deposit graded layers onto a silicon wafer. Ray tracing and beam propagation methods were used to simulate the periodic refocussing of the nominally parabolic refractive index profile. Propagation characteristics were measured using a standard prism coupler and also by observing fluorescence from a specially doped thin polymer layer spun on to the top of the planar lens.

Prediction of urban sound propagation is an integral part for the assessment of noise levels in cities. Several propagation modeling methods exist to predict sound propagation in city environments including parabolic equation, diffusion equation, radiosity, ray tracing, image source, modal analysis, and transmission line matrix methods. For this study, adaptive beam tracing as a geometrical acoustic prediction method is applied in the context of predicting sound propagation in complex urban environments. Adaptive beam tracing is advantageous compared to the ray tracing and image source methods by eliminating aliasing errors and spurious image sources, respectively. A model of diffraction [Svensson et al., J. Acoust. Soc. Am. 106, 2331–2344 (1999)] is integrated with the adaptive beam tracing algorithm in order to enhance the prediction capability of the proposed method. The effects of facade roughness, street canyon shielding, and building spacing are investigated. Comparison of the proposed method is made with a ray tracing method. Computation times, as well as various geometric configurations, are compared between the proposed method and the ray tracing method.

The optical efficiencies of a solar trough concentrator are important to the whole thermal performance of the solar collector, and the outer surface of the tube absorber is a key interface of energy flux. So it is necessary to simulate and analyze the concentrated solar flux density distributions on the tube absorber of a parabolic trough solar collector for various sun beam incident angles, with main optical errors considered. Since the solar trough concentrators are linear focusing, it is much of interest to investigate the solar flux density distribution on the cross-section profile of the tube absorber, rather than the flux density distribution along the focal line direction. Although a few integral approaches based on the "solar cone" concept were developed to compute the concentrated flux density for some simple trough concentrator geometries, all those integral approaches needed special integration routines, meanwhile, the optical parameters and geometrical properties of collectors also couldn't be changed conveniently. Flexible Monte Carlo ray trace (MCRT) methods are widely used to simulate the more accurate concentrated flux density distribution for compound parabolic solar trough concentrators, while generally they are quite time consuming. In this paper, we first mainly introduce a new backward ray tracing (BRT) method combined with the lumped effective solar cone, to simulate the cross-section flux density on the region of interest of the tube absorber. For BRT, bundles of rays are launched at absorber-surface points of interest, directly go through the glass cover of the absorber, strike on the uniformly sampled mirror segment centers in the close-related surface region of the parabolic reflector, and then direct to the effective solar cone around the incident sun beam direction after the virtual backward reflection. All the optical errors are convoluted into the effective solar cone. The brightness distribution of the effective solar cone is supposed to be circular Gaussian type. Then a parabolic trough solar collector of Euro Trough 150 is used as an example object to apply this BRT method. Euro Trough 150 is composed of RP3 mirror facets, with the focal length of 1.71m, aperture width of 5.77m, outer tube diameter of 0.07m. Also to verify the simulated flux density distributions, we establish a modified MCRT method. For this modified MCRT method, the random rays with weighted energy elements are launched in the close-related rectangle region in the aperture plane of the parabolic concentrator and the optical errors are statistically modeled in the stages of forward ray tracing process. Given the same concentrator geometric parameters and optical error values, the simulated results from these two ray tracing methods are in good consistence. The two highlights of this paper are the new optical simulation method, BRT, and figuring out the close-related mirror surface region for BRT and the close-related aperture region for MCRT in advance to effectively simulate the solar flux distribution on the absorber surface of a parabolic trough collector.

A way to apply the shortest path ray tracing (SPR) method to irregularly tetrahedralized velocity structure and its efficiency are described. SPR is the ray tracing method utilizing Dijkstra's shortest path algorithm in network graph theory. The tetrahedralization by Delaunay tessellation is one of the irregular parameterization of 3D velocity structure in travel time tomography. The irregular parameterization has great advantage of flexible expression of velocity structure though the computational costs in ray-tracing are relatively high. The hybrid ray tracing between SPR (for initialization) and pseudo-bending (for optimization) might be more economic. It has been known as the well proven scheme in the sense of the simplicity and robustness. Though SPR was originally developed under regular parameterization, it can easily be expanded to irregular parameterized structure without any theoretical modification. We propose a simple design of network for SPR that conforms the shape of tetrahedron. Generally, the cost and accuracy of SPR depends on the network design. In this paper, we have carried out a synthetic examination with a complex velocity model to assess the cost and accuracy of SPR with irregular network. Result reveals that the proposed ray tracing method is practically economic and accurate (almost the same accuracy as SPR under the regular cubic cell model). Further, it has potential to obtain more accuracy by lower costs due to the economical network integrated with flexible element size.

Analytic ray tracing is considerably less time consuming than numerical ray tracing. However, despite the advantage of speed, analytic ray tracing has a major limitation: the difficulty of including the effects on the ray path of horizontal gradients in electron density. In the past this difficulty has been addressed using ionospheric models whereby an effective tilt is introduced by displacing the center of the ionosphere from the center of the Earth. In this paper, ray equations for the ground range, phase path, group path, and divergent power loss are developed for a new two‐dimensional analytic ray tracing technique, known as the segmented method for analytic ray tracing (SMART), which is able to deal with horizontal gradients in electron density. Ray tracing using two tilting methods are compared with ray tracing using SMART. Further, these results are compared with a numerical ray tracing program known as homing‐in ray tracing (HIRT).

Optical lenses and systems have historically been of interest to the design and simulation community due to their extensive use in a variety of applications, including telecommunications and imaging. To simulate these systems, it is often possible to take advantage of symmetry or apply physical approximations, such as ray tracing and/or beam propagation, in order to avoid a rigorous solution of Maxwell's equations. However, in cases where these techniques are not applicable, such as when feature sizes become comparable to the wavelength of interest, full-wave electromagnetic simulations are required. Unfortunately, the time constraints and simulation sizes associated with many designs render this analysis infeasible or impractical, a problem that is aggravated by iterative design flows. Hence, a numerical platform capable of handling such computationally intense problems is necessary. In this paper, we present a hardware-based, full-wave simulation platform and demonstrate the advantages of hardware acceleration for the simulation of optical applications. Specifically, we will present a diffractive optical element (DOE) lens simulation, comparing results with previously published analytic and experimental data. We then modify the basic lens arrangement to produce an optical beam splitter. Because such a device cannot be analytically described using symmetry, this example will demonstrate the unique advantages of powerful hardware solvers for the analysis of DOE applications. Finally, we discuss how hardware-based solvers are critical for iterative designs by means of a 1-to-3 beam splitter example. This simulation system represents a new era in optical engineering, enabling the design of next-generation devices today.

Millimeter wave technology will be dominating the fifth-generation networks due to the clear advantage of higher frequency bands and hence wider spectrum. In this paper, the indoor radio wave propagation at 28 GHz is studied by developing an efficient three-dimensional ray tracing (ETRT) method. The simulation software based on the ETRT model has been verified by measurement data. The received signal strength indication and path loss have shown significant agreement between simulation and measurement. Compared with the conventional shooting bouncing ray tracing method, the proposed ETRT method has better agreement with measurement data.

The use of image and ray tracing methods (and variations thereof) for the computation of sound fields in rooms is relatively well developed. In their regime of validity, both methods work well for prediction in rooms with small amounts of diffraction and mostly specular reflection at the walls. While extensions to the method to include diffuse reflections and diffraction have been made, they are limited at best. In the fields of illumination and computer graphics the ray tracing and image methods are joined by another method called luminous radiative transfer or radiosity. In radiosity, an energy balance between surfaces is computed assuming diffuse reflection at the reflective surfaces. Because the interaction between surfaces is constant, much of the computation required for sound field prediction with multiple or moving source and receiver positions can be reduced. In acoustics the radiosity method has had little attention because of the problems of diffraction and specular reflection. The utility of radiosity in acoustics and an approach to a useful development of the method for acoustics will be presented. The method looks especially useful for sound level prediction in industrial and office environments. [Work supported by NSF.]

Current architectural trends on supercomputers have dramatic increases in the number of cores and available computational power per die, but this power is increasingly difficult for programmers to harness effectively. High-level language constructs can simplify programming many-core devices, but this ease comes with a potential loss of processing power, particularly for cross-platform constructs. Recently, scientific visualization packages have embraced language constructs centering around data parallelism, with familiar operators such as map, reduce, gather, and scatter. Complete adoption of data parallelism will require that central visualization algorithms be revisited, and expressed in this new paradigm while preserving both functionality and performance. This investment has a large potential payoff: portable performance in software bases that can span over the many architectures that scientific visualization applications run on. With this work, we present a method for ray tracing consisting of entirely of data parallel primitives. Given the extreme computational power on nodes now prevalent on supercomputers, we believe that ray tracing can supplant rasterization as the work-horse graphics solution for scientific visualization. Our ray tracing method is relatively efficient, and we describe its performance with a series of tests, and also compare to leading-edge ray tracers that are optimized for specific platforms. We find that our data parallel approach leads to results that are acceptable for many scientific visualization use cases, with the key benefit of providing a single code base that can run on many architectures.

We present a method suitable for ray tracing in a three-dimensional structure composed of several zones. This is a method extended from two-dimensional ray tracing and is characterized by a small number of calculation steps for a ray. Applying this method to four events occurring around Hokkaido and off the east coast of Kyushu, we investigate the anomalous structure in the upper mantle beneath Japan. P velocities of 8.05 and 7.50km/s are estimated as a model in the uppermost parts of the high and low velocity zones, respectively; the velocity difference of 6.8 percent is comparable with those in the studies made to date. At the lower boundary of the high velocity lithosphere, the velocity contrast is suggested to be lower than 2 percent, while it is over 2 to 3 percent at the upper boundary.

The graded-index (GRIN) media have been widely used in modern optical systems, such as imaging lenses, optical beam delivery components, and beam shaping elements. Accurate and efficient modeling of electromagnetic fields propagating in GRIN media is essential for developing innovative and high-quality optical products. It is the goal of this thesis. We first give an overview of several existing modeling techniques, including the rigorous ones to model symmetric GRIN structures, e.g., Mie theory (spherically symmetric) and several beam propagation methods (BPMs) with approxiamations to model general GRIN structures, which are numerically more efficient than rigorous methods. However, many of BPMs are limited by considering only a small variance of the refractive index. To overcome the limitations, we develop a unified field solver, known as the Runge-Kutta (RK) k-domain field propagation method. It can be used to calculate general input fields propagating through an arbitrary GRIN medium, accurately, without physical approximations, such as the scalar field approximation or the paraxial approximation. We convert Maxwells equations in spatial (x-) domain into ordinary differential equations (ODEs) in the spatial-frequency (k-) domain, which can be solved iteratively using the RK method. In our numerical calculation, taking advantage of the convolution theorem, the total numerical effort is linear in the number of sampling points. As many GRIN components are modeled or designed using ray tracing techniques, the field passing through the GRIN components must show negligible diffraction, which satisfies the geometric field assumption. By substituting geometric field ansatz into the ODEs of RK k-domain field propagation method and Maxwells equations, we obtain two ODEs in x-domain. After solving them by using again RK method, the RK x-domain field propagation method is established.

We propose a method for fast analytical ray tracing on a heterogeneous sphere for surface waves. We first select the specific coordinates of orbital motion which have action/angle properties. We then apply the Lie perturbation approach and, when the square of the slowness is expanded in spherical harmonics, we obtain an analytical formula for the perturbed parameters of the ray. These expressions are sensitive to both the odd and even parts of the expansion. Traveltimes are computed by perturbation, while geometrical spreading is estimated numerically between two nearby perturbed rays. For the ‘Gulf of Alaska’ earthquake of November 1987, the analytical ray follows the same deviations with respect to the great circle as the numerical one, when we use the phase velocity model of Montagner & Tanimoto (1990) at period of 167 s. The agreement is excellent for traveltime computations. When the numerical ray tracing predicts a focus/defocusing effect, the perturbed ray tracing gives the same trend. Moreover, variations of the shooting angles between trains can be as high as 20° which might modify the radiation pattern seen by the station for different trains. When the perturbed ray deviates too strongly, a reinitialization technique will guarantee a given accuracy. This reinitialization, which is not required for long periods (>150 s), is probably necessary at shorter periods.

Ray tracing and modal methods are widely used for modeling RF propagation in tunnels. In this letter, we show that the two methods are mathematically equivalent and yield the same results. We also compare the theoretical predictions from both methods to field measurements at different frequencies (455, 915, 2450, and 5800 MHz) and find good agreement.

As the world keeps advancing, the need for automated interconnected devices has started to gain significance; to cater to the condition, a new concept Internet of Things (IoT) has been introduced that revolves around smart devicesʼ conception. These smart devices using IoT can communicate with each other through a network to attain particular objectives, i.e., automation and intelligent decision making. IoT has enabled the users to divide their household burden with machines as these complex machines look after the environment variables and control their behavior accordingly. As evident, these machines use sensors to collect vital information, which is then the complexity analyzed at a computational node that then smartly controls these devicesʼ operational behaviors. Deep learning‐based guessing attack protection algorithms have been enhancing IoT security; however, it still has a critical challenge for the complex industries’ IoT networks. One of the crucial aspects of such systems is the need to have a significant training time for processing a large dataset from the networkʼs previous flow of data. Traditional deep learning approaches include decision trees, logistic regression, and support vector machines. However, it is essential to note that this convenience comes with a price that involves security vulnerabilities as IoT networks are prone to be interfered with by hackers who can access the sensor/communication data and later utilize it for malicious purposes. This paper presents the experimental study of cryptographic algorithms to classify the types of encryption algorithms into the asymmetric and asymmetric encryption algorithm. It presents a deep analysis of AES, DES, 3DES, RSA, and Blowfish based on timing complexity, size, encryption, and decryption performances. It has been assessed in terms of the guessing attack in real‐time deep learning complex IoT applications. The assessment has been done using the simulation approach and it has been tested the speed of encryption and decryption of the selected encryption algorithms. For each encryption and decryption, the tests executed the same encryption using the same plaintext for five separate times, and the average time is compared. The key size used for each encryption algorithm is the maximum bytes the cipher can allow. To the comparison, the average time required to compute the algorithm by the three devices is used. For the experimental test, a set of plaintexts is used in the simulation—password‐sized text and paragraph‐sized text—that achieves target fair results compared to the existing algorithms in real‐time deep learning networks for IoT applications.

Readily available RGB-D cameras in smart phones and improving 3D scanning technologies have made it possible to produce detailed point cloud and point-based models of real world objects even in real time. Rendering such models in high quality and at satisfactory frame rates is needed for realistic <italic>extended reality</italic> (XR) applications. This publication reviews real-time photorealistic point cloud rendering methods which directly ray trace or rasterize point cloud models, with an emphasis on ray tracing and real-time performance. We found that real-time direct point cloud ray tracing research has been focused on static non-animated content, and thus, open research possibilities include adapting modern dedicated ray tracing hardware for increased performance for animated and live captured scenes, and adding path tracing techniques to increase photorealistic effects in the rendering result. A categorization and discussion on the capabilities of state-of-the-art photorealistic point cloud rendering methods is presented by surveying both real-time and offline methods, which are assumed to become real-time capable with the advances in near-future hardware. Challenges and future trends are derived by comparing different rasterization and ray tracing methods as well as acceleration structures for point clouds in terms of produced rendering effects and speed.