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We present a framework for the inverse design of spatially graded phononic materials based on ray tracing. Spatial grading of phononic materials allows the unit cell to vary smoothly in space. Compared to periodic architectures, spatial grading opens up a vast design space that promises new capabilities for manipulating elastic and acoustic waves. However, the use of spatial grading to control wave propagation has been limited to simple gradings, largely due to the bottleneck of modeling efficiency, and to the long-wavelength limit of low frequencies. In this work, ray tracing is exploited as an efficient alternative, around which we develop an optimization framework based on the adjoint state method toward the flexible inverse design of graded phononic materials. We demonstrate the design of graded mass-spring networks for objectives including focusing all directions of a point source, broadband focusing of a plane wave, and frequency sorting. These objectives are out of reach of periodic phononic materials, highlighting the high potential of spatially graded phononic materials. Moreover, our results demonstrate the importance of wave dispersion, which is classically neglected in the long-wavelength limit of elastodynamics. [ABSTRACT FROM AUTHOR]

In water-guided laser technology, the stability of water jets is crucial to ensure the efficient transmission of laser energy. However, the thermal effects generated when high-power lasers are coupled with water jets are bound to impact the stability of the water jets, thus becoming a critical issue that restricts the development of high-power water-guided laser technology. In addressing this issue, this paper establishes a temperature model for coupling high-power lasers with water jets. Subsequently, with validation of the model's effectiveness through experimental data, simulations are conducted to analyze the temperature distribution within the water jet. During the simulation process, lasers with different parameters were coupled with water jets to analyze the temperature variation law of the water jets. Additionally, the maximum laser power coupled with water jets of different lengths was solved. Based on the calculated temperature values of the water jet, simulate the evolution of its profile over time when it has an initial temperature gradient. Simultaneously, perform a three-dimensional reconstruction of the obtained perturbed profile and conduct ray tracing to analyze the laser's transmission losses within the perturbed profile. Finally, high-speed cameras are utilized to capture the profile of the water jet, validating the laser-induced fragmentation behavior in the water jet. The research findings will provide a significant reference value for selecting laser parameters and controlling thermal effects in water-guided high-power technology. [ABSTRACT FROM AUTHOR]

When quantum dot diffusion plates (QDDPs) are used as phosphor conversion materials for high-power lighting, transparent ceramics (TCs) can be used to prevent thermal damage of QDDPs. The spectral, suitable for diverse lighting environments, can be precisely calibrated by modifying their ratio. The temperature dependent photoluminescence spectra, fluorescence lifetime, Huang Rhys factor and activation energy of TCs were studied in detail. It was evident from the results that the intensity of TCs remained above 89% even at 423 K, while fluorescence lifetime remained stable, nearly 64 ns. Huang-Rhys factor and activation energy were consistently measured at 1.81 and 0.13 eV, respectively. The extraordinary luminescent stability of TCs revealed their integral role in providing reliable protection for QDDPs. The spectra of LEDs/LDs were successfully predicted using Monte Carlo ray tracing method. The service condition under high-energy laser was studied using finite element method. White light with Commission Internationale de l'Eclairage (CIE) of (0.38, 0.39) and (0.31, 0.34) and luminous efficiency of 58 and 150 lm/W were prepared by combining QDDPs/TCs with LEDs/LDs, and the Color Rendering Index (CRI) reached a remarkable 88.4 and 78.8. A detailed exploration of the proficient thermal management was accomplished using finite element analysis, with the simulated outcomes matching closely with the experimental results. [ABSTRACT FROM AUTHOR]

IOLs introduce a significant amount of peripheral defocus which affects peripheral retinal image quality in eyes implanted with IOLs. IOL peripheral defocus varies significantly with IOL power and design. Purpose: To quantify the angular dependence of monofocal intraocular lens (IOL) power. Setting: Ophthalmic Biophysics Laboratory, Kallam Anji Reddy campus, L V Prasad Eye Institute, Hyderabad, India. Design: Laboratory study. Methods: Experiments were performed on IOLs from 2 different manufacturers (APPALENS 207, Appasamy Associates and SN60WF, Alcon Laboratories, Inc.). IOL powers ranged from 17 to 25 diopters (D). The IOLs were mounted in a fluid-filled chamber, and the on-axis and off-axis powers were measured using a laser ray tracing system over the central 3 mm zone with delivery angles ranging from −30 to +30 degrees in 5-degree increments. The position of the best focus was calculated for each IOL at each angle. The angular dependence of IOL power was compared with theoretical predictions. Results: Peripheral defocus increased significantly with increasing incidence angle and power. The peripheral defocus at ±30 degrees increased from 5.8 to 8.5 D when the power increased from 17.5 to 24.5 D for APPALENS 207 and from 4.9 to 7.4 D when the power increased from 17 to 25 D for SN60WF. The mean difference between the measured and theoretical tangential power at ±30 degrees was 0.50 ± 0.16 D for the APPALENS 207 and −0.40 ± 0.10 D for the SN60WF, independent of IOL power. Conclusions: IOLs introduce a significant amount of peripheral defocus which varies significantly with IOL power and design. Given that peripheral defocus is related to lens power, replacement of the crystalline lens (approximately 24 D) with an IOL will produce a significant difference in peripheral defocus profile after surgery. [ABSTRACT FROM AUTHOR]

Two-dimensional tomographic forward modeling based on first arrivals requires the calculation of the minimum travel times of multiple emission points in a single iteration. The conventional method, which calculates each emission point one by one, produces many unuseful calculations and has low computational efficiency. To solve this problem, given the characteristic that the velocity distribution of a model does not change during a single iteration of forward modeling, an improved algorithm was proposed based on the reciprocity principle and Fermat's principle. The ray tracing results of a small number of emission points were used to constrain the calculation area of other emission points, which reduced the number of unuseful calculations and improved the calculation efficiency of a single-iteration tomographic forward modeling simulation. Theoretical analysis and numerical examples showed that for a homogeneous model, when the transmitting and receiving points were located on two long sides, three adjacent sides (i.e., two long sides and one short side), and four sides, the computational efficiency of the improved algorithm was about 2 times, 2 times, and 1.5 times, respectively, that of the conventional method. For heterogeneous models, the computational efficiency of the improved algorithm was usually more significant. [ABSTRACT FROM AUTHOR]

Plasmaspheric density structures are considered to control the propagation trajectories of fast magnetosonic (MS) waves in the inner magnetosphere. However, whether the plasmaspheric plume can effectively alter the propagation of MS waves remains unknown. Based on the analytical model of plasma density, ray tracing simulations are performed to investigate the propagation of exactly perpendicular MS waves in the equatorial plane in the magnetosphere containing a plasmaspheric plume. We find that plasmatrough and plume MS waves propagating toward the plasmaspheric plume can be reflected into the plasmaspheric core by the plume, then potentially migrating globally and thus quasi‐trapped inside the plasmaspheric core. The simulations also indicate that lower‐frequency MS waves approaching the plasmaspheric plume are more easily reflected and quasi‐trapped inside the plasmaspheric core. Our findings illustrate a previously unexplored way that plasmatrough MS waves could access and be trapped inside the plasmaspheric core via azimuthal plasmaspheric density structures. Plain Language Summary: Fast magnetosonic (MS) waves are one of the most common and intense electromagnetic emissions observed both inside and outside the plasmasphere. Portions of MS waves observed inside the plasmasphere are supposed to come from the propagation of those waves outside the plasmasphere. It is well known that the radial plasmaspheric density structures can strongly alter the propagation trajectories of MS waves in the inner magnetosphere. However, a typical azimuthal plasmaspheric density structure, the plasmaspheric plume, can form in the magnetosphere during the geomagnetic disturbed times. How the plasmaspheric plume affects the propagation of MS waves remains unknown. Based on the ray tracing simulations, we show that MS waves generated outside the plasmapause and inside the plume can be reflected into the plasmaspheric core by the plasmaspheric plume and a few of the reflected waves can migrate globally inside the plasmaspheric core. Our findings provide a new potential way for MS waves to access and be trapped inside the plasmaspheric core. Key Points: Propagation of magnetosonic waves in the magnetosphere containing a plasmaspheric plume is examined using the ray tracing simulationsPlasmatrough and plume magnetosonic waves can be reflected into the plasmaspheric core by the plasmaspheric plumeThose reflected magnetosonic waves can be quasi‐trapped inside the plasmaspheric core or propagate radially down to low altitudes [ABSTRACT FROM AUTHOR]

This paper proposes a hyperspectral imaging simulation method based on a ray-tracing algorithm. The algorithm combines calculations based on solar and atmospheric visible light radiation as well as the spectral bidirectional reflection distribution function (BRDF) of the target surface material and can create its own scenarios for simulation calculations on demand. Considering the presence of multiple scattering between the target and background, using the ray-tracing algorithm enables the precise computation of results involving multiple scattering. To validate the accuracy of the algorithm, we compared the simulated results with the theoretical values of the visible light scattering intensity from a Lambertian sphere. The relative error obtained was 0.8%. Subsequently, a complex scene of engineering vehicles and grass was established. The results of different observation angles and different coating materials were calculated and analyzed. In summary, the algorithm presented in this paper has the following advantages. Firstly, it is applicable to geometric models composed of any triangular mesh elements and accurately computes the effects of multiple scattering. Secondly, the algorithm combines the spectral BRDF information of materials and improves the efficiency of multiple scattering calculations using nonuniform sampling. The computed hyperspectral scattering data can be applied to simulate airborne or space-borne remote sensing data. [ABSTRACT FROM AUTHOR]

People spend majority of their lifetime indoors making comfortable dwellings one of the major requirements otherwise it may primarily impact the occupant's health and productivity. Indoor temperature and relative humidity (RH) are the two major parameters for determining comfort level, whilst airflow and heat transfer are having an influential role in controlling these parameters. Since solar radiations are the primary source of heat inside a building and ceiling fans play a significant role in improving air circulation. The present study strives to develop a model for evaluating the thermal behavior of commercial space under the influence of solar radiations and ceiling fans. It involves "solar ray tracing" and "3D-Fan zone" models to assess their impact on indoor air quality and thermal comfort. The developed model is validated by comparing the simulated results of air velocity and temperature with experimental data accumulated from space. Further, the validated model is used to evaluate the impact of different levels of solar irradiation between 200 W/m2 and 1000 W/m2 on the indoor environment. Results revealed that an increment of 200 W/m2 irradiations is raising the mean indoor temperature by 0.2 °C, percentage dissatisfaction by 8% while a reduction in RH is reported to be 0.5%. [ABSTRACT FROM AUTHOR]

In real‐time rendering, optimizing the sampling of large‐scale candidates is crucial. The spatiotemporal reservoir resampling (ReSTIR) method provides an effective approach for handling large candidate samples, while the Generalized Resampled Importance Sampling (GRIS) theory provides a general framework for resampling algorithms. However, we have observed that when using the generalized multiple importance sampling (MIS) weight in previous work during spatiotemporal reuse, variances gradually amplify in the candidate domain when there are significant differences. To address this issue, we propose a new MIS weight suitable for resampling that blends samples from different sampling domains, ensuring convergence of results as the proportion of non‐canonical samples increases. Additionally, we apply this weight to temporal resampling to reduce noise caused by scene changes or jitter. Our method effectively reduces energy loss in the biased version of ReSTIR DI while incurring no additional overhead, and it also suppresses artifacts caused by a high proportion of temporal samples. As a result, our approach leads to lower variance in the sampling results. [ABSTRACT FROM AUTHOR]

Synthesising high‐quality views of dynamic scenes via path tracing is prohibitively expensive. Although caching offline‐quality global illumination in neural networks alleviates this issue, existing neural view synthesis methods are limited to mainly static scenes, have low inference performance or do not integrate well with existing rendering paradigms. We propose a novel neural method that is able to capture a dynamic light field, renders at real‐time frame rates at 1920× resolution and integrates seamlessly with Monte Carlo ray tracing frameworks. We demonstrate how a combination of spatial, temporal and a novel surface‐space encoding are each effective at capturing different kinds of spatio‐temporal signals. Together with a compact fully‐fused neural network and architectural improvements, we achieve a twenty‐fold increase in network inference speed compared to related methods at equal or better quality. Our approach is suitable for providing offline‐quality real‐time rendering in a variety of scenarios, such as free‐viewpoint video, interactive multi‐view rendering, or streaming rendering. Finally, our work can be integrated into other rendering paradigms, e.g., providing a dynamic background for interactive scenarios where the foreground is rendered with traditional methods. [ABSTRACT FROM AUTHOR]

Laser sintering is a widely used process for producing complex shapes from particulate materials. However, understanding the complex interaction between the laser and particles is a challenge. This investigation provides new insights into the sintering process by simulating the laser source and the neck growth of particle pairs. First, a multi-physics discrete element method (DEM) framework is developed to incorporate temperature-dependent contact rheological and thermal properties, incorporating heat transfer and neck formation between the particles. Next, energy transport by ray tracing is added to allow for computing the amount of laser energy absorbed during sintering. The DEM model is calibrated and validated using experimental data on neck growth and temperature evolution of particle pairs made of polystyrene and Polyamide 12. The findings show that the proposed DEM model is capable of accurately simulate the neck growth during the laser sintering paving the way for better controlling and optimizing the process. [ABSTRACT FROM AUTHOR]

In high-precision space geodetic techniques data processing, the mapping function (MF) is a key factor in mapping the radio waves from the zenith direction down to the signal incoming direction. Existing MF products, either site-wise Vienna Mapping Function (VMF1 and VMF3) or grid-wise VMF1 and VMF3, are only available at the Earth surface. For overhead areas, height correction is always required, which is becoming increasingly important with growing airborne aircraft activity. In this contribution, we introduce a novel method aimed at providing a large number of MFs to the user in a simple and efficient manner, while minimizing the loss of precision. The approach effectively represents the vertical profile of the MFs from the Earth's surface up to altitudes of 14 km. In addition, the new model corrects for height in the assessment using the fifth generation of the European Centre for Medium-Range Weather Forecasts ReAnalysis (ERA5) ray tracing calculations for a global 5° × 5° grid with 54 layers in the vertical direction, a total of 8 azimuths in the plane, and 7 elevation angles, for each day in 2021. Specifically, for both polynomial and exponential model of order 2 and 3, the relative residuals are < 0.3% for the hydrostatic delay MF coefficient a h , and < 1% for the wet delay MF coefficient a w . The precision of the new model on the Earth’s surface is evaluated using site-wise VMF1 and VMF3 GNSS (Global Navigation Satellite System) products from Technische Universität Wien. The root mean square error of slant hydrostatic delay and slant wet delay at a 3° elevation angle is approximately 4–5 cm and 2–5 cm, respectively. [ABSTRACT FROM AUTHOR]

A new ray tracing algorithm based on the shortest path method was designed and optimized to model seismic rays. The workflow is based on Dijkstra's algorithm to find the shortest path iteratively on self-adapting random grids. These random grids adapt from one iteration to the next, storing in memory those nodes that minimize the traveltime in each iteration, consequently automatically densifying the grid in areas with significant velocity variations. Different data structures and grid geometries were studied, and it was confirmed that using a combination of a binary heap and random grids prevents systematic errors generated by using regular grids while keeping the computational times low. Since the nodes that minimize the traveltime are stored in each iteration, the memory requirements increase logarithmically, with the initial iterations having the most significant impact on the error minimization but plateauing afterwards. It was found that, albeit this increase in memory requirements, by focusing the densification of nodes in areas close to the actual trajectory of the rays, the error minimization requires fewer iterations than other implementations based on multiple realizations of random grids (requiring less than a tenth of the number of iteration of other methods). A function to handle extreme topographic variations was also designed, which uses a boolean test to reject rays crossing the topography, making the algorithm suitable for first arrival modelling in complex topography areas, such as the required for tomographic inversion of first arrivals in thrust-belt land seismic. [ABSTRACT FROM AUTHOR]

The ocean sound speed changes drastically with time and space. It is almost impossible to achieve centimeter-level-precision Global Navigation Satellite System (GNSS)-Acoustic (GNSS-A) positioning without regarding spatio-temporal variations of sound speed. Inspired by the atmospheric delay estimation, we define zenith acoustic delay (ZAD) as the zenith-direction ranging error sourced by the sound speed variations, and then it is decomposed into one temporal component and two horizontal components for the sound speed variations in time and space, respectively. We propose a network solution with the three ZAD components of each seafloor geodetic point as common parameters to be estimated, and then present a piece-wise estimation to characterize their time-varying nature. To remedy the ray bending effect this study is implemented in the context of the ray tracing algorithm based on a reference sound speed profile (SSP). Experimental tests show that the proposed network solution improves ZAD estimation and results in a better position determination as compared to the single-point positioning (SPP) solution. The proposed network solution for a single campaign can achieve a horizontal positioning precision better than 5 cm (1-sigma) for the seafloor geodetic array centroid. The temporal variation of ZAD is up to one meter while the horizontal variations vary within a few decimeters in the time domain and show an azimuthal asymmetry in space. [ABSTRACT FROM AUTHOR]

Efficient communication is crucial in reducing injuries and fatalities in coal mine accidents, necessitating the study of simulation methods for mine communication. When transceiver antennas are positioned close to the same side of the tunnel, the simulation results from the Ray Tracing (RT) method exhibit significant errors. Additionally, the Finite-Difference Time-Domain (FDTD) method demands substantial computational resources. In response to these challenges, we propose a RT-FDTD method, guided by the law of conservation of energy. This approach involves dividing the mine tunnel into a cuboidal region, using the RT method to calculate the electric field strength on the cuboid's surface, and then employing this as the excitation source for the FDTD method. Subsequently, the FDTD method is used to calculate the electric field strength within the cuboid. Experimental results demonstrate that the RT-FDTD method effectively mitigates the limitations of the RT and FDTD methods, enhancing both the efficiency and accuracy of simulations in underground mine. [ABSTRACT FROM AUTHOR]

AbstractAchieving a correct cooling in glass manufacturing is very important to obtain the desired level of stresses and to avoid breakage. Numerical simulations can be used to optimize the cooling parameters. Such simulations have to be multiphysical coupling thermics and mechanics. Moreover, since glass is a semitransparent material, radiative effects inside the glass have to be taken into account. The present paper is devoted to numerical study of the cooling of a glass square plate on a metallic frame. To this end, the commercial software Abaqus was used to model the thermomechanical behavior of glass using adapted subroutines and was combined with an in-house C++ tool developed to solve the Radiative Transfer Equation. During and at the end of the cooling, weak areas in the glass plate are revealed by the simulation. Depending on the case studied, taking accurately the radiative effects into account leads to difference of residual stresses which can reach 10 MPa in certain cases. [ABSTRACT FROM AUTHOR]

Purpose: To investigate and compare different strategies of corneal power calculations using keratometry, paraxial thick lens calculations and ray tracing. Setting: Tertiary care center. Design: Retrospective single-center consecutive case series. Methods: Using a dataset with 9780 eyes of 9780 patients from a cataractous population the corneal front (Ra/Qa) and back (Rp/Qp) surface radius/asphericity, central corneal thickness (CCT), and entrance pupil size (PUP) were recorded using the Casia 2 tomographer. Beside keratometry with the Zeiss (PKZ) and Javal (PKJ) keratometer index, a thick lens paraxial formula (PG) and ray tracing (PR) was implemented to extract corneal power for pupil sizes from 2 mm to 5 mm in steps of 1 mm and PUP. Results: With PUP PKZ/PKJ overestimates the paraxial corneal power PG in around 97%/99% of cases and PR in around 80% to 85%/99%. PR is around 1/6 or 5/6 diopters (D) lower compared with PKZ or PKJ. For a 2 mm pupil PR is around 0.20/0.91 D lower compared with PKZ/PKJ and for a 5 mm pupil PR is comparable with PKZ (around 0.03 D lower) but around 0.70 to 0.75 D lower than PKJ. Conclusions: "True" values of corneal power are mostly required in lens power calculations before cataract surgery, and overestimation of corneal power could induce trend errors in refractive outcome with axial length and lens power if compensated with the effective lens position. [ABSTRACT FROM AUTHOR]

Annual daylighting and point-in-time glare calculations depend on manipulating large matrices representing annual light levels and image pixels, respectively. Advances in computation speed have allowed modern green building standards like LEED, WELL, and EN 17037 to require annual daylighting calculations at a fine resolution across a building's floorplate. As parallel ray tracing speeds become faster and cameras increase in resolution, matrix manipulation itself has emerged as a bottleneck to delivering fast simulation results. This paper describes a how vectorized computation methods can be applied to annual daylighting simulation and high dynamic range (HDR) image processing. Vectorization allows a computer to perform simple operations on large amounts of data simultaneously. We use the NumPy library in Python to vectorize multiple steps in the calculation of spatial daylight autonomy and annual renderings for glare as example climate-based daylighting metrics, achieving a speedup of two orders of magnitude. We also show that NumPy can manipulate large HDR images with speedups for individual operations up to six orders of magnitude. [ABSTRACT FROM AUTHOR]

Optical systems have conventionally been evaluated by means of ray-tracing techniques, which can extract performance parameters such as aberration and spot size. However, current ray tracing methods in the field of optical design lack satisfactory methods for error analysis and improving its accuracy. Additionally, numerical calculations of large-scale, lengthy, and multi-scale ray tracing often result in inaccurate and even invalid outcomes due to round-off errors. In response to this challenge, we adopt the floating arithmetic theory to analyze the accumulative impact of round-off errors during the ray tracing process and develop a numerical error model for ray tracing. Using this model, we introduce compensation measures to achieve higher precision and then implemented a high-precision ray tracing algorithm. Finally, we conduct numerical experiments to validate our error model and high-precision algorithm, demonstrating their superior precision in comparison to the state-of-the-art authoritative optical design software, Zemax and CODE V. • Optical design demands higher precision in ray tracing algorithms. • The error model reveals the sources and constituents of errors in ray tracing. • Five measures are derived from the model to improve the precision of ray tracing. • Our approach excels beyond the state-of-the-art algorithms of Zemax and CODE V. [ABSTRACT FROM AUTHOR]

One of the approaches to solving the inverse problem of determining the parameters of ionospheric disturbances is the multiple solution of the two-point problem with the subsequent comparison of the simulation results with experimental data (ionograms). However, this approach is usually associated with significant calculation time costs, which makes it impossible to process large arrays of sounding data. The method described in this article makes it possible to quickly determine the horizontal velocity of the ionospheric disturbance by descent rate of an additional U-shaped trace moving to lower virtual heights on the vertical sounding ionograms: in order to calculate the velocity, it is proposed to use the results of the ray tracing obtained for the reference background profiles with disturbances superimposed on them. [ABSTRACT FROM AUTHOR]

Previous studies have shown that auroral kilometric radiation (AKR) can play an important role in the magnetosphere‐atmosphere coupling and has the right‐handed extraordinary (R‐X), left‐handed ordinary (L‐O) and left‐handed extraordinary (L‐X) modes. However, the L‐X mode has not been directly observed in the lower latitude magnetosphere yet, probably because of its very limited frequency range. Here, using observations of the Arase satellite on 6 September 2018, we present an AKR event with two distinct bands (8–20 and 300–1000 kHz) around the location: L = 8 and latitude = −37°. The low (high) band is identified as the L‐X (R‐X) mode based on the polarization and frequency ranges. Simulations of 3‐D ray tracing show that most of ray paths with 14 (11 and 18) kHz pass (miss) the location of Arase, basically consistent with observations. Our study provides direct evidence that the L‐X mode can propagate from high latitudes downward to lower latitudes. Plain Language Summary: Auroral kilometric radiation (AKR) is a widely existing radio emission with kilometric wavelength at the Earth, contributing to the magnetosphere‐atmosphere coupling. Similar emissions have been observed on all magnetic planets of the solar system. Previous studies have shown that AKR primarily occurs in the R‐X mode, with a small contribution in the L‐O and L‐X modes. The L‐X mode at lower latitudes has not been directly observed so far, most likely due to its extremely limited frequency range. Here, we present an L‐X mode (peak frequency ∼14 kHz) in the lower latitude magnetosphere observed by the Arase satellite. Using the 3‐D ray tracing method, we simulate ray paths with different initial wave parameters and source locations. Simulations show that ray paths with 14 (11 and 18) kHz pass (miss) the location of the Arase satellite and are highly dependent on initial wave parameters and the location of source. Our results provide a direct evidence that the L‐X mode from high latitude source regions can propagate downward to lower latitudes under suitable conditions. This study enriches the understanding of AKR propagation characteristics in the magnetosphere. Key Points: An auroral kilometric radiation (AKR) event with two distinct bands (8–20 kHz and 300–1000 kHz) is observed around the location: L = 8 and latitude = −37°Based on the polarization and frequency ranges, the low (high) band AKR is identified as the L‐X (R‐X) mode3‐D ray tracing simulations show that L‐X mode can propagate downward to lower latitudes, basically consistent with observations [ABSTRACT FROM AUTHOR]

Focusing on the problem of unclear ray-traced spots and their distribution rules in the design process of the Herriott cell, first, the characteristics of long-optical-path gas absorption cells were analyzed, and the calculation method of basic cavity length and the effective optical path of Herriott gas absorber cells were studied. Second, according to the transmission characteristics of geometric optics, a physical model of light transmission in Herriott cells was established via the LightTools software. Finally, simulation analysis was performed on Herriott cells with 5- and 14.4-m optical paths separately, determining the quantitative relationship between d/f and the number of spots reflected on the concave mirror, and optimizing the effective optical path and output laser energy of the Herriott cells. Through research analysis, the sizes and distribution positions of concave mirror spots in the Herriott cells were identified, as well as the factors affecting the number of reflections. It was also found that the number of reflected spots gradually decreases as d/f increases, revealing the light-tracing results and its spot distribution rule on the mirror surface, as well as verifying the accuracy of the theory. The findings of this study provide a basis for the optical path system design and optimization for Herriott cells with different optical path lengths. [ABSTRACT FROM AUTHOR]

A direct variational method for solving the problem of finding ocean wave rays reflected from the coastline with given positions of the source and the point of observation is considered. It is shown that the original boundary value problem can be reduced to the direct search of stationary points of the functional equal to the time of wave propagation along the ray. Information about the objective function in the area of solutions to the ray tracing problem allows us to construct a systematic procedure for finding minima, saddle points, and maxima. A feature of the proposed approach is the optimization of the ray reflection point along a given coastline. [ABSTRACT FROM AUTHOR]

When photographing objects underwater, it is important to utilize an optical window to isolate the imaging device from the water. The properties of the entire imaging system will change, and the imaging quality will decrease due to the refraction impact of the water and the window. The theoretical calculation method for air imaging is no longer relevant in this context. To analyze the unique rule, this research derives the formulas for key parameters of underwater imaging systems under paraxial circumstances. First, the optical window is modeled, then the formula for the optical window's focal length in the underwater environment is derived, and the change rule for the focal length of various window forms underwater is condensed. For the ideal imaging system using a domed optical window, the equivalent two-optical group model of the imaging system is established, and the formula for calculating the focal length, working distance, and depth of field of the underwater imaging system is derived through paraxial ray tracing. The accuracy of the formula is verified through the comparative analysis of the formula calculation results and the Zemax modeling simulation results. It provides an important theoretical basis for the in-depth study of underwater imaging technology. [ABSTRACT FROM AUTHOR]

We report the first applications of the quasioptical (QO) code PARADE (PAraxial RAy DEscription) for modeling the electron cyclotron emission (ECE) diagnostic. Geometrical optics (GO) has been exploited to predict the ECE intensity received by an antenna, but is not sufficient since GO drops the information lying on the transverse cross section of the antenna sensitivity. Hence, we studied a QO model of ECE measurement based on the PARADE code. By introducing a weighting operator W ˆ , induced by the envelope profile of a wave beam virtually injected from an ECE receiving antenna, an integral equation, formally identical to the conventional GO model, is newly derived from the wave-action conservation law. A QO ECE prediction module −E3 is also newly developed, is applied to the JT-60SA tokamak, and shows that radiation temperature is corrected from conventional GO prediction. The −E3 module and the PARADE code are applicable to any fusion plasma devices. By using this ECE prediction package, more realistic calculations of radiation temperature are expected by taking the actual structure of an ECE receiving antenna and plasma parameters as well. [ABSTRACT FROM AUTHOR]

Addressing the challenge of real-time estimation of instantaneous sound speed profiles (SSP for short). We proposes a SSP inversion method based on the travel time of vertically launched sound waves from seafloor stations to the sea surface. The basic principles of the inversion method are introduced, followed by an investigation into the calculation of instantaneous SSP area considering tidal and wave effects. The proposed method is validated by using semi-experimental data, the results indicate that the accuracy of predictions is poor if the correcting for the tidal and wave influences are not taken. However, after applying the correction equation proposed in this study to adjust for travel time, the relative error in the prediction of SSP area difference is less than 4%. [ABSTRACT FROM AUTHOR]

Plasmaspheric hiss waves are important to shape the Earth's electron radiation belt. These waves are commonly envisioned to have a long lifetime which allows them to permeate the global plasmasphere from a spatially restricted source. However, this hypothesis has not been experimentally confirmed yet, because of the challenging observational requirements in terms of location and timing. With wave and particle measurements from five magnetospheric satellites and detailed modeling, we present the first report of long lifetime (∼42 s) hiss rays in the substorm‐disturbed plasmasphere. The low‐frequency hiss waves are found to originate from the middle piece of the plasmaspheric plume, bounce between two hemispheres, and eventually drift into the plasmaspheric core. These hiss rays can travel through ∼3 hr magnetic local time and ∼4 magnetic shell. Such a long‐time and large‐scale permeation of hiss rays could benefit from the ducting process by plasmaspheric field‐aligned density irregularities. Plain Language Summary: Earth's plasmasphere is populated by a type of whistler‐mode wave named plasmaspheric hiss which is able to shape the electron radiation belt. Hiss waves were commonly envisioned to have a long lifetime which allows them to permeate the global plasmasphere from a spatially restricted source. Although there have been numerous studies on the source of plasmaspheric hiss waves, the hypothesis regarding their long lifetime remains not experimentally confirmed yet because of the challenging observational requirements in terms of location and timing. On the basis of wave and particle measurements from five magnetospheric satellites covering the entire plasmasphere and detailed modeling, we show that the hiss rays can survive at least 42 s in the plasmasphere disturbed by substorms. Within the survival period, these hiss rays migrated from the middle piece of the plasmaspheric plume to the plasmaspheric core, whose path lengths reached 25 Earth radii. Such a long‐time and large‐scale permeation of hiss rays from the plasmaspheric plume to the plasmaspheric core could benefit from the ducting process by plasmaspheric field‐aligned density irregularities. Key Points: Low‐frequency hiss waves were excited by energetic electrons inside the dayside plasmaspheric plume following substormsLow‐frequency hiss rays survived at least 42 s, allowing themselves to migrate from the plasmaspheric plume to the plasmaspheric corePlasmaspheric density ducts facilitated the permeation of hiss rays from the plasmaspheric plume to the plasmaspheric core [ABSTRACT FROM AUTHOR]

We present trevr2 (Tree-based REVerse Ray Tracing 2), a fast, general algorithm for computing the radiation field, suitable for both particle and mesh codes. It is designed to self-consistently evolve chemistry for zoomed-in astrophysical simulations, such as cosmological galaxies with both internal sources and prescribed background radiation, rather than large periodic volumes. Light is propagated until absorbed, with no imposed speed limit other than those due to opacity changes (e.g. ionization fronts). trevr2 searches outward from receiving gas in discrete directions set by the healpix algorithm (unlike its slower predecessor trevr), accumulating optical depth and adding the flux due to sources combined into progressively larger tree cells with distance. We demonstrate N activelog2 N execution time with absorption and many sources. This allows multiband radiative transfer costs comparable to tree-based gravity and hydrodynamics, and the usual speed-up when active particles evolve on individual time-steps. Sources embedded in non-homogeneous absorbing material introduce systematic errors. We introduce transmission averaging instead of absorption averaging which dramatically reduces these systematic effects. We outline other ways to address systematics including an explicit complex source model. We demonstrate the overall performance of the method via a set of astrophysical test problems. [ABSTRACT FROM AUTHOR]

The images of Sagittarius A* published by the Event Horizon Telescope (ETH) Collaboration in 2022 present features that were associated with an emission ring consistent with what is expected from an accretion disc surrounding the supermassive black hole at the centre of our Galaxy. Here, we generate images of Sgr A* across different configurations of a simple accretion disc model that became successful, in our previous work, in reproducing the main features observed in M87*. Their best image, here reproduced in Fig.  1 , suggests a geometric configuration of an inclined disc with three bright regions; which we have considered as our first configuration. Since we were not convinced with the results of this first configuration, we also explore in detail the case of nearly edge-on orientations which are a priori the expected geometry for a relaxed disc, as seen from the plane of the Galaxy. We have produced simulated images using an efficient ray tracing and geodesic deviation methodology that allows to account for deformation, relativistic, and magnification effects. We compare our synthetic images with the EHT images reconstructed with data from April 6 and 7 of 2017. We found that, although the EHT Collaboration seems to discard the image from April 6, our best suggested image resembles the output from the themis pipeline for April 6; which for us gives support for the edge-on configuration. [ABSTRACT FROM AUTHOR]

This paper provides a comprehensive overview of approaches to the determination of isocontours and isosurfaces from given data sets. Different algorithms are reported in the literature for this purpose, which originate from various application areas, such as computer graphics or medical imaging procedures. In all these applications, the challenge is to extract surfaces with a specific isovalue from a given characteristic, so called isosurfaces. These different application areas have given rise to solution approaches that all solve the problem of isocontouring in their own way. Based on the literature, the following four dominant methods can be identified: the marching cubes algorithms, the tessellation-based algorithms, the surface nets algorithms and the ray tracing algorithms. With regard to their application, it can be seen that the methods are mainly used in the fields of medical imaging, computer graphics and the visualization of simulation results. In our work, we provide a broad and compact overview of the common methods that are currently used in terms of isocontouring with respect to certain criteria and their individual limitations. In this context, we discuss the individual methods and identify possible future research directions in the field of isocontouring. [ABSTRACT FROM AUTHOR]

Multi‐bounce, pure specular light paths produce complex lighting effects, such as caustics and sparkle highlights, which are challenging to render due to their sparse and diverse nature. We introduce a learning‐based method for the efficient rendering of pure specular light transport. The key idea is training a neural network to model the distribution of all specular light paths between pairs of endpoints for one specular object. To achieve this, for each object, our method models the distribution of sparse and diverse specular light paths between two endpoints using smooth 2D maps of ray directions from one endpoint and represents these maps with a 2D convolutional network. We design a training scheme to efficiently sample specular light paths from the scene and train the network. Once trained, our method predicts specular light paths for a given pair of endpoints using the network and employs root‐finding‐based algorithms for rendering the specular light transport. Experimental results demonstrate that our method generates high‐quality results, supports dynamic lighting and moving objects within the scene, and significantly enhances the rendering speed of existing techniques. [ABSTRACT FROM AUTHOR]

This paper introduces a hybrid method that leverages the advantages of both the window-based separate algorithm and the regularization-based unifying algorithm to refine the three-dimensional refractive index field measured by the background-oriented schlieren (BOS) tomography. Two image-warping approaches, under paraxial and non-paraxial ray-tracing assumption, are developed as a connecting link between coarse and refined reconstruction. An orthogonal test is conducted to examine the influence of various factors on the reconstruction fields in the hybrid approach, providing insights into the impact of factors such as the ray-tracing assumption, initial value for refractive index iteration, and image displacement algorithm. Various synthetic and real BOS cases demonstrate that our hybrid method reconstructs a more detailed and robust field, outperforming conventional BOS reconstruction methods in scenarios with small or large density gradients, as well as laminar or turbulent structures. [ABSTRACT FROM AUTHOR]

Purpose: To identify the equivalent K-readings and total keratometry zones that is optimally suitable for calculating the IOL spheroequivalent according to 7 formulas. Methods: The study included 40 patients (40 eyes) who underwent uneventful femtosecond laser-assisted cataract surgery and refractive lens exchange (RLE) with implantation of a trifocal diffractive IOL (PanOptix, Alcon inc.). Targeted emmetropia was achieved in all patients, no distance and near correction was needed. Retrospective IOL calculations were performed utilizing 7 formulas (SRK/T, Holladay 1 and 2, Haigis, Hoffer Q, Barrett Universal 2, Olsen) and Pentacam keratometry data: Holladay equivalent K-readings, total optical power by ray tracing (TCRP) centered on the apex and pupil in 10 zones (from 0.5 to 5 mm in 0.5 mm increments). For each formula/zone/map combination: postoperative predicted refraction (PPRs), mean absolute errors (MAEs), and median absolute errors (MedAEs) were analyzed. Results: According to EKR, the Haigis formula showed the lowest error in the central zones up to 3.5 mm, the TCRP zone for Holladay I and II formulas 4.0–4.5 mm, for HofferQ and SRK/T formulas 4.5–5.0 mm, and for Olsen and Barrett II Universal—5 mm. Conclusion: The use of keratometry data (EKR, TCRP) in the formulas adapted to SimK, with the correct choice of the evaluation zone of keratometric data, will increase the chance of hitting the refractive target. [ABSTRACT FROM AUTHOR]

Sonic boom propagation over land is being studied to ensure a minimal impact on the population in the event that supersonic flight over land becomes permissible. Sonic boom behavior in and around urban areas is particularly important due to the high density of people residing in cities and the increased probability of impacting large numbers of people if urban areas lie in the flight path. This study models sonic booms around urban canyons using a combined ray tracing/radiosity method. The impacts of several parameters, such as diffusion, arrival angle, building heights, and canyon width, on the sound field were explored. The results showed that without diffusion, there was no real trend as the canyon height and width and arrival angles were varied. There were strong shadow zones where no sound was detected as this model does not include diffraction. In other locations, between one and four boom events were received. The resulting perceived level in dB (PLdB) varied from 0 in the shadow zones to 94 dB. Diffuse reflections was the parameter that had the greatest impact on the resulting signatures. Parameters that caused an increased number of reflections showed significant changes in the signature shape and a dramatic reduction in the PLdB. [ABSTRACT FROM AUTHOR]

Determination of the slowness vector and the homogeneous ray-velocity vector is critical for seismic ray tracing in a viscoelastic anisotropic medium. Three formulae, the traditional g-Hamiltonian, newly developed conjugate real ray tracing (C-RRT) and innovative g*-Hamiltonian, are employed to calculate the ray-velocity vectors with the determined slowness vectors in a viscoelastic anisotropic medium. We demonstrate the forward and reverse searching procedures to determine the ray-velocity vectors' slowness vectors. The former implements either a linear search or an optimization method to find the slowness vectors that lead to homogeneous complex ray-velocity vectors (its real and imaginary parts are parallel). The latter is based on a new generalized cost function and applies an optimization method to find the slowness vector for a known ray direction. Using sandstone as an example material, we compare the accuracies and efficiencies of the three formulae and the two searching procedures. Our examples show that the forward searching procedure with the traditional g-Hamiltonian formula and the linearly searching method may generate unphysical solutions for qSV wave due to its cusps or triplication, but using the optimization method may not only mitigate the influence of the cusps and triplication but also significantly improve the accuracies and efficiencies almost two orders higher. For the reverse searching procedure, we propose a general form of the cost function valid for all the formulae of the ray-velocity vector and easily solved by an optimization method. The examples demonstrate that the solutions yielded by the forward and reverse searching procedures coincide well for all three body waves (qP, qSV and qSH), except for the triplication of the qSV wave. In particular, the optimization method combined with the novel g*-Hamiltonian formula may completely overcome the issues of spurious solutions and the qSV -wave cusp and triplication. [ABSTRACT FROM AUTHOR]

Experiments examining the amount of specular reflection (or "glint") within hohlraums containing different gas fill densities have recently been performed. Simulations of these experiments are presented that show using a single flux limiter cannot explain the decrease in glinted power with increasing gas fill density. The hypothesis that flow-induced beam deflection alters laser absorption is presented. A model is proposed that can be implemented into a ray tracing description of the laser commonly used in radiation hydrodynamic codes. It is shown that simulations using this model capture the trend with gas fill density improving agreement with measurements. This formulation is then applied to an ensemble of laser-driven inertial confinement fusion experiments performed at the National Ignition Facility. The proposed model shows little impact on the total x-ray drive on the capsule but a large impact on the resulting implosion symmetry. [ABSTRACT FROM AUTHOR]

A soft x-ray varied-line-spacing (VLS) laminar-type spherical grating with a super-mirror-type (SMT) multilayer was designed for a soft x-ray high resolution flat-field spectrograph in a region of 2–4 keV. The effective groove density of the designed VLS grating is 3200 lines/mm, and the local groove density varies from 2700 to 3866 lines/mm. The geometrical imaging property was evaluated by numerical calculations. The resolving power estimated by means of ray tracing was up to ∼103. For the evaluation of diffraction efficiency, the SMT multilayer structure designed for 3200 lines/mm in our previous work, Koike et al., Rev. Sci. Instrum. 94, 045109 (2023), was employed, and the numerical calculation was performed considering the local groove density of VLS grooves and the local incidence angle being affected by the curvature of the spherical surface and the geometrical relation between the source and incidence point on the grating. The results showed that the SMT multilayer-coated grating exhibited about an order of magnitude higher diffraction efficiency compared with an Au-coated grating. [ABSTRACT FROM AUTHOR]

Reducing structural shocks propagated as elastic waves in thin plate-like structures is of paramount importance in diverse engineering applications. In this study, a shock reduction method using elastic patches that deflect bending waves through wave refraction, while maintaining the structural stiffness and strength is presented. Elastic patches with gradual thickness variation were designed and thoroughly investigated both numerically and experimentally. Two types of triangular elastic patches, flat and pyramid-shaped, were utilized to refract and attenuate transient bending waves at different incident angles. All results from ray tracing, finite element analysis, and experiments consistently demonstrated the effective reduction of passing waves in areas behind the attached patches. Moreover, the influence of gradual thickness variation was thoroughly discussed. The proposed method provides a practical approach to mitigate transient shock responses in specific target areas across various structural applications without compromising structural stiffness and strength. [ABSTRACT FROM AUTHOR]

This study delves into the polarization properties of various hair colors using several techniques, including polarization ray tracing, full Stokes, and Mueller matrix imaging. Our analysis involved studying hair in both indoor and outdoor settings under varying lighting conditions. Our results demonstrate a strong correlation between hair color and the degree of linear polarization. Specifically, light-colored hair, such as white and blond, exhibits high albedo and low DoLP. In contrast, dark hair, like black and brown hair, has low albedo and high DoLP. Our research also revealed that a single hair strand displays high diattenuation near specular reflections but high depolarization in areas with diffuse reflections. Additionally, we investigated the wavelength dependency of the polarization properties by comparing the Mueller matrix under illumination at 450 nm and 589 nm. Our investigation demonstrates the impact of hair shade and color on polarization properties and the Umov effect. [ABSTRACT FROM AUTHOR]

An important prerequisite for process simulations of laser beam welding is the accurate depiction of the surface energy distribution. This requires capturing the optical effects of the laser beam occurring at the free surface. In this work, a novel optics ray tracing scheme is proposed which can handle the reflection and absorption dynamics associated with laser beam welding. Showcasing the applicability of the approach, it is coupled with a novel surface detection algorithm based on smoothed particle hydrodynamics (SPH), which offers significant performance benefits over reconstruction‐based methods. The results are compared to state‐of‐the‐art experimental results in laser beam welding, for which an excellent correspondence in the case of the energy distributions inside capillaries is shown. [ABSTRACT FROM AUTHOR]

We investigate the propagation of light signals across multiple gravitational lenses, with particular emphasis on the "communication bridge" scenario of two lenses with collinear source and observer. The lenses are assumed to be non-coplanar, far enough from one another for each lens to be treated independently as thin lenses in the limit of weak gravity. We analyze these scenarios using several different tools, including geometric optics, photon mapping, wave optics and ray tracing. Specifically, we use these tools to assess light amplification and image formation by a two-lens system. We then extend the ray tracing analysis to the case of multiple non-coplanar lenses, demonstrating the complexity of images that are projected even by relatively simple lens configurations. We introduce a simple simulation tool that can be used to analyze lensing by non-coplanar gravitational monopoles in the weak gravity limit, treating them as thin lenses. [ABSTRACT FROM AUTHOR]

Purpose: To investigate toric monofocal intraocular lens (TIOL) rotation and associated changes in cylinder power caused by Nd: YAG laser capsulotomy performed due to posterior capsule opacification (PCO). Setting: Ekol Eye Hospital, Izmir, Turkey. Design: Prospective case series. Methods: 41 eyes of 20 women and 21 men were included in the study. Before and 1 month after Nd:YAG laser capsulotomy, TIOL tilt and decentration were determined with Scheimpflug camera, and TIOL axial rotation and the change in cylinder power induced by this rotation were measured by ray tracing aberrometry. The time interval between cataract surgery and Nd:YAG laser capsulotomy was noted. Results: Rotational misalignment of the TIOL was measured as 4.65 ± 2.75 degrees (range 0 to 11 degrees) before vs 6.97 ± 2.92 degrees (range 0 to 13 degrees) after capsulotomy, and absolute rotation was 2.75 ± 1.94 degrees (range 0 to 7 degrees, P = .028). Before and after Nd:YAG laser capsulotomy, cylinder power was 0.24 ± 0.70 diopter (D) (range 0.00 to 0.63 D) vs 0.56 ± 0.77 D (range 0.02 to 0.91 D), respectively, with an absolute change in cylinder power of 0.34 ± 0.22 D (range 0.01 to 0.90 D, P = .001). After capsulotomy, there was a significant decrease in IOL tilt in the horizontal and vertical planes and an increase in decentration (P < .05). Time interval (33.02 ± 12.9 months) and IOL horizontal decentration were independent factors affecting IOL rotation after capsulotomy (P < .05). Conclusions: Nd:YAG laser capsulotomy may cause TIOL rotation as well as tilt and decentration, resulting in a change in the TIOL's corrective effect on corneal astigmatism. Although this change was clinically insignificant, it may be beneficial to consider that TIOL rotational misalignment may occur in patients undergoing early capsulotomy. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the impact of both static and dynamic effects of motion on Underwater visible light communication (UVLC) channels. While previous studies have focused on static channel modeling, we argue that dynamic channel modeling is crucial for accurate UVLC analysis. To model static and dynamic UVLC channels, we use the Monte Carlo ray tracing (MCRT) method in Zemax Optics Studio; a reliable and practical setup simulator that produces results similar to experimental data. We evaluate the effect of channel coding on system performance by comparing nine different combinations and using Goodness-of-Fit (GoF) tests to determine the best-fit distribution. Our results reveal that the static case outperforms the dynamic case in terms of raw performance without any coding. However, we also show that the bit error rate (BER) is severely impacted in various realistic scenarios for a dynamic environment. To improve the BER and achieve adequate received signal quality, we recommend using convolutional codes. This paper emphasizes the importance of dynamic channel modeling in UVLC and provides practical solutions to enhance the UVLC performance in dynamic environments. The findings of our study provide valuable insights into the performance of UVLC systems and emphasize the need for researchers and designers to account for the dynamic realistic behavior in the underwater channel to achieve optimal performance in UVLC systems for underwater communication applications. [ABSTRACT FROM AUTHOR]

To demonstrate the results of ray tracing higher- and lower-order aberrations in pseudophakic eyes with rotationally asymmetrical segment multifocal lenses, total high- and low-order aberrations, measured by root mean square value (RMS), refraction, uncorrected distance and uncorrected near visual acuity (UCDVA and UCNVA), and tear break-up time, were measured at scotopic size in 42 eyes of patients implanted with bifocal refractive Mplus15/Mplus30 IOL with +1.5 dpt near addition (42 eyes of patients implanted with Mplus15)/+3.0 dpt near addition (91 eyes of patients implanted with Mplus30), and 107 eyes of control group. No significant differences were noticed between the examined groups concerning UCDVA, UCNVA, and tear break-up time (p < 0.001). Coma and total high-order aberrations were significantly higher for the Mplus30 lens in comparison to the Mplus15 lens and the control group (Coma, Trefoil p < 0.001, Secondary Astigmatism p = 0.002). The spherical aberrations were significantly higher in the lower-addition lens (p = 0.016) in comparison to the control group and to the higher-addition lens group (p < 0.001). Both intraocular lens models were successful at reaching refractive aim, good distance, and near function with the lower higher-order aberrations for the low-addition lens. [ABSTRACT FROM AUTHOR]

A deep learning based method is proposed to predict the urban air mobility (UAM) noise propagation in the urban environment. This method aims to efficiently estimate the noise impact of UAM flights on the complex urban area. The noise hemisphere was created via the comprehensive multirotor noise assessment framework to determine the noise level of UAM. The noise propagation to a randomly generated three-dimensional (3D) urban area was then calculated using the ray tracing method, including atmospheric attenuation and multiple reflections. 45 000 two-dimensional noise maps were used to train and evaluate the modified convolutional neural network. The results demonstrated high accuracy, with a root mean square error of only 2.56 dB compared to the ray tracing method, while reducing computation time by more than 1800 times. This model was applied to analyze the noise impact of various UAM flight conditions and landing scenarios at a vertiport. This deep learning approach is a fast method with adequate accuracy for predicting UAM noise impact in 3D urban environments. Also, it can inform the development of noise based strategies for UAM operations. [ABSTRACT FROM AUTHOR]

Precise navigation for fully autonomous driving—especially in dense urban areas—requires periodic precise position estimates. Global Navigation Satellite System (GNSS) technology has the potential to provide absolute positioning accuracy at a centimeter level. However, buildings in urban environments cause signal distortions and signal reflections—the so-called multipath—which are the most challenging parts in the GNSS error budget. Hence, we developed a scalable real-time multipath simulator for mitigating potential multipath receptions. The simulator uses three-dimensional (3D) building information, satellite, and user positions. The key drivers of latency are the calculation of reflection, diffraction, and line-of-sight, as well as the response time of the 3D building model database. The memory manager of the graphic processing units (GPUs) in combination with a dedicated load balancer enables fast and efficient multipath analysis. Selected case studies demonstrate the simulator's potential to significantly improve the position accuracy of the processing engine. The use of the multipath simulator reduces the error in 61% of the error measurements in a stress test scenario to less than half of the non-multipath processing. The scalability of the simulator is demonstrated by combining the multipath simulator with a traffic simulator. Furthermore, we present a novel methodology for the detection of walls using GNSS signals to better account for incomplete or erroneous 3D building information in GNSS signal processing. [ABSTRACT FROM AUTHOR]