Three-dimensional Ray-tracing Model Research Articles

Modelling approaches to predict light absorption in gas-liquid flow photosensitized oxidations

The photosensitized production of singlet oxygen is a benchmark reaction for characterizing flow photoreactors. Light absorption is the driving force of the photooxidation reaction and modelling represents a fast and cost-efficient method for its prediction and optimization. In this study, we report two models of photon absorption in single- and two-phase flow. Firstly, a three-dimensional ray tracing model was developed and validated by experimental 9,10-dimethylanthracene (DMA) photooxidation in presence of Rose Bengal. By comparing the simulated and experimental DMA conversion, the flow and illumination conditions affected by mass transfer limitations in liquid and gas–liquid Taylor flows were identified. Furthermore, the ray tracing model was used to compare the light absorption in Taylor, annular, and two bubbly flow configurations. At a low attenuation coefficient of 2.3 cm−1 a minor difference between flow patterns was observed irrespective of liquid hold-up. At the same liquid hold-up and between 26 cm−1 and 200 cm−1, the relative volumetric absorbed photon flux strongly depends on the flow pattern. Secondly, the ray tracing model was used as reference to develop a simplified absorption model which only requires the geometry and optical properties of the multiphase flow. The novel predictive method is based on the geometrical approximation of the optical pathlength in the liquid slugs, the liquid film and the liquid volume next to the bubble caps. As it requires minimum computational power and provides good accuracy, the geometry-based model has the potential to assist future automated optimization of gas–liquid photooxidations.

Indoor WLAN Intelligent Target Intrusion Sensing Using Ray-Aided Generative Adversarial Network

An indoor target intrusion sensing technique has been used in many fields, such as smart home management, security monitoring, counter-terrorism, and disaster relief. At the same time, with the wide deployment of wireless local area network (WLAN) and general support of the IEEE 802.11 protocol by various mobile devices, the target intrusion sensing can be realized based on the existing WLAN infrastructure without requiring the target to carry any special device. However, the existing indoor WLAN target intrusion sensing approaches usually depend on the radio map construction with huge labor and time cost, which is the major barrier of current systems. In response to this compelling problem, we propose the new ray-aided generative adversarial model (RaGAM) to automatically construct the radio map, which is used for the indoor WLAN intelligent target intrusion sensing and localization. To achieve the low labor and time cost, the RaGAM uses the adaptive-depth ray tree based the quasi three-dimensional ray-tracing model to depict the difference of WLAN signals between the silence and intrusion environments with the purpose of constructing the synthetic radio map. Considering the gap between the synthetic and actual radio maps, we modify the conventional generative adversarial network by the joint synthetic and unsupervised learning (or called S+U learning) from the actual unlabeled received signal strength (RSS) data to improve the precision of the proposed ray-tracing model, and consequently obtain the refined radio map. After that, the statistical characteristics of the refined radio map are utilized to construct the training set for the probabilistic neural network (PNN), and then by using the well-trained PNN to classify the newly collected RSS data, the target intrusion sensing, and localization are achieved. The experimental results show that the proposed approach cannot only perform well in terms of computation cost and the ray-tracing accuracy, but also sense the target intrusion states accurately.

Comprehensive three-dimensional ray tracing model for three-mirror cavity-enhanced spectroscopy.

A 3D ray tracing model is used to simulate optical reinjection in a nonresonant optical cavity, for off-axis integrated cavity output spectroscopy. The optical cavities are optimized for maximum intensity enhancement factors via a grid search and a genetic algorithm. Intensity enhancement factors up to 1400 are found for short cavities (3cm) and up to 101 for long cavities (50cm). The model predicts that short absorption cells can be used, having a long effective path length and a high throughput power. This opens new opportunities in the field of ultrasensitive absorption spectroscopy and allows the design of compact optical gas sensors.

Development of a Three-Dimensional Ray-Tracing Model of Sugarcane Canopy Photosynthesis and Its Application in Assessing Impacts of Varied Row Spacing

Sugarcane has emerged as the second largest source of biofuel, primarily as ethanol produced in Brazil. Dual row planting using asymmetric spacing of rows can decrease damage to plants and soil structure from harvest equipment though potentially can cause some loss of productivity due to increased shading. Can we assess this loss, without experimental testing of the thousands of potential permutations of planting design and cultivar canopy form? Here we develop a computational framework which couples 3D canopy architectural information, a ray-tracing algorithm, and a steady-state C4 photosynthesis model to study this question. We demonstrate the utility of the model by comparing evenly spaced rows at 100 cm to alternating row spacing of 45 and 155 cm. Asymmetric planting caused a 9% decrease in predicted net canopy carbon uptake over the growing season for a major current cultivar. The loss was greater at lower leaf area indices, when leaves were more vertical and when rows were oriented east-west, suggesting agronomic approaches to minimize loss. This study demonstrates the utility of this computational framework, which could also be used to aid breeding by identifying ideotypes for different environments and objectives, and to assess impacts of environmental change.

Three-dimensional ray-tracing model for the study of advanced refractive errors in keratoconus.

We propose a numerical three-dimensional (3D) ray-tracing model for the analysis of advanced corneal refractive errors. The 3D modeling was based on measured corneal elevation data by means of Scheimpflug photography. A mathematical description of the measured corneal surfaces from a keratoconus (KC) patient was used for the 3D ray tracing, based on Snell's law of refraction. A model of a commercial intraocular lens (IOL) was included in the analysis. By modifying the posterior IOL surface, it was shown that the imaging quality could be significantly improved. The RMS values were reduced by approximately 50% close to the retina, both for on- and off-axis geometries. The 3D ray-tracing model can constitute a basis for simulation of customized IOLs that are able to correct the advanced, irregular refractive errors in KC.

Ray Tracing Simulation in Nonspherically Symmetric Atmosphere for GPS Radio Occultation

A three-dimensional ray tracing model with aiming algorithms for global positioning system (GPS) signal is proposed to make simulations conform to the realistic radio occultation (RO) signal propagation. The two aiming algorithms used in this study ensure the initial and end point ray trajectories are located in the prescribed region. In past studies, the ray tracing techniques applied to the RO signal simulation usually assumed a spherically symmetrical atmosphere for simplicity. The exact GPS and low earth orbit (LEO) satellite locations are not considered in the simulation. These two assumptions make the simulation unrealistic for GPS signal propagation in the RO technique. In the proposed model, the shape of the earth is assumed as an ellipse. The information from European Centre for Medium-Range Weather Forecasts (ECMWF) analysis is used to setup the atmosphere in the simulation. Two aiming algorithms are developed to determine the initial signal propagating direction to make the simulated signal start from the prescribed GPS satellite position and end in the close vicinity of the LEO satellite position. An ideal spherical symmetric atmospheric structure is used to verify the ray tracing model. The fractional difference between real and simulated refractivity results is less than 0.1%. Otherwise, the GPS and LEO satellite position in the Formosat-3/COSMIC observation and the ECMWF analysis, considering the earth’s flattening, is also used to verify the aiming algorithms. All of the simulated signals end in close vicinity to the LEO satellite position in the simulation results.

Efficient three-dimensional ray-tracing model for electromagnetic propagation prediction in complex indoor environments

A three-dimensional ray-tracing model for the use of the uniform theory of diffraction and geometrical optics in radio channel characterizations of indoor environments is presented in this paper. Based on the environment information chosen by the proposed modeling approach, the model is effectively applied by utilizing a technique in which multiple reflections, transmissions, and diffractions are considered via the ray-path classification into four different categories. Ray paths belonging to each ray category are determined by using different methods. Our theoretical results are compared with narrowband and wideband measurements. The good agreement with these measurements indicates that our prediction model works well for such indoor communication applications.

Inertia gravity waves associated with deep convection observed during the summers of 2005 and 2007 in Korea

[1] Characteristics of inertia gravity waves associated with convection are investigated in the lower stratosphere using high-resolution radiosonde data observed from 18 June to 15 July of 2005 and 2007 in Korea. Three-dimensional ray-tracing model and reanalysis data are used to investigate the propagation and the sources of the observed waves. The observed waves associated with convections are discriminated based on the existence of convections when and where the rays reach the average height range of convective clouds. Waves observed in 2005 and 2007 show similar spectral characteristics, but wave energy in 2007 is significantly larger than in 2005. The observed waves propagate from three source regions: the northeastern, southeastern, and western regions around Korea. They show preferential propagation directions based on their sources, and convections from the western region generate larger-amplitude gravity waves than the other two regions. The spectral characteristics of the observed waves are determined largely by those of the convective forcing, along with the wave propagation condition associated with background wind and stability. The significantly larger mean wave energy in 2007 occurs because more observed waves originate from the western region of Korea in 2007 than in 2005 where convective forcing is much larger than in the other source regions.

Characteristics and sources of inertia-gravity waves revealed in the KEOP-2007 radiosonde data

Characteristics and sources of inertia-gravity waves are investigated using high-resolution radiosonde data observed at ten stations in Korea during 15 June to 15 July 2007. The wave analyses are performed in the lower stratospheric region (Z = 17–30 km). The average intrinsic frequency, vertical wavelength, and horizontal wavelength for the observed waves are 2.77f (where f is the Coriolis parameter), 2.58 km, and 620.11 km, respectively. The average eastward and westward momentum fluxes are 0.005 m2 s−2 and −0.003 m2 s−2, respectively, and the average northward and southward momentum fluxes are 0.007 m2 s−2 and −0.002 m2 s−2, respectively. To understand the propagation and the sources of the observed gravity waves, a three-dimensional ray-tracing model is used. The observed gravity waves are classified into two groups based on the existence of convection when and where the rays reach altitudes of 6–13 km. Sources are mostly located in the northeast and southeast of the observation stations below Z = 5 km for the convection-related cases (CONV), while those for the other cases (NCONV) are located in the northeast and southeast of the observation stations above Z = 20 km. The average intrinsic frequency and vertical wavelength of the CONV cases are somewhat larger than those of the NCONV cases. The average potential, kinetic, and total wave energies of the CONV cases are less than those of the NCONV cases.

Effects of observed horizontal inhomogeneities within cirrus clouds on solar radiative transfer

[1] In situ microphysical and combined radar and radiometer measurements of 11 cirrus clouds from Central Equatorial Pacific Experiment (CEPEX), European Cloud and Radiation Experiment (EUCREX), investigation of Clouds by Ground-Based and Airborne Radar and Lidar (CARL), and First International Satellite Cloud Climatology Project (ISCCP) Regional Experiment (FIRE) are used to investigate effects of horizontal cloud inhomogeneities on solar radiative transfer. A three-dimensional ray-tracing model (GRIMALDI), based on the Monte Carlo method, is used to calculate upward and downward flux densities and absorption for the spectral range from 0.38 to 4.0 μm. Radiative flux densities are calculated using the inhomogeneous clouds derived from the observations and for horizontally and vertically averaged homogeneous clouds. Horizontally averaged values of radiative flux densities and absorption for heterogeneous clouds can differ by up to 30% from those calculated for the homogeneous clouds for convectively induced tropical cirrus clouds. The midlatitude cases examined tended to be more homogeneous, and hence differences between radiative properties for the homogeneous and heterogeneous clouds did not exceed 10%. For cirrus clouds with mean optical thicknesses smaller than 5 and with relative variances of optical thickness smaller than 0.2, errors caused by the homogeneous assumption are smaller than ±10%.

Two- and three-dimensional ray tracing applied to the land mobile satellite (LMS) propagation channel

This work examines the application of ray-tracing propagation models to system simulations for satellite mobile communications. A two-dimensional (2D) and a three-dimensional (3D) algorithm are outlined and compared using canonical propagation problems. Additional comparisons of both models with measurement campaigns are performed. The results show that two-dimensional models are suited for coverage and network planning. For system-design studies, however, three-dimensional ray tracing is mandatory. The novel three-dimensional ray-tracing model is able to predict time series of power delay profiles, Doppler and polarimetric information with high precision. It includes the time-variant correlation between the propagation channels of all visible satellites of an arbitrary satellite constellation. It therefore proves to be especially suited for system investigation of future LMS communication and navigation systems.

DETECTION OF CRACKS IN FRP BY USING EMBEDDED PLASTIC OPTICAL FIBER

Plastic optical fiber is a multi-mode optical fiber and used for short distance communication, illumination, etc. Plastic optical fibers can be also used as a damage sensor by measuring optical power loss. Plastic optical fibers are much cheaper and easier to connect than silica fibers, and suitable to be embedded in FRP because of the similarity of its elasticity and coefficients of thermal expansion. In this work, plastic optical fibers were embedded in three types of GFRP specimens including unidirectional and cross-ply laminates. The relations among the optical power, the strain and the number of cracks were studied. Cracks in GFRP lamintes were observed by a video microscope under tensile load. As the strain increased, the optical power decreased linearly before the initiation of cracks and nonlinearly after that. The optical power loss by a single crack was simulated by using a three-dimensional ray tracing model and the results were compared with the experimental results. Then, it was concluded that the nonlinearity of curve of the optical power loss was affected by the cracks and the plastic optical fiber has much potential to be used as a crack-detecting sensor for smart composites.

An iterative ray tracing model for ultrasonic nondestructive testing

This paper describes a three-dimensional ray tracing model for predicting ultrasonic energy propagation in anisotropic and inhomogeneous materials. The model has recently been developed to be an iterative tool, capable of calculating energy paths between specified start and end points. This two-point ray tracing is presented and its value for predicting energy paths between transducers and postulated defects is discussed. Applications of the model to problems of interest to ultrasonic nondestructive testing are presented. These include assessment of inspection methods for austenitic components, such as cladding and welds. In particular, defect location and sizing errors are calculated for underclad defects at a variety of depths below a layer of cladding, and for backwall breaking defects in and around a single V-weld. For the calculations considered, we find these errors generally to be small, except for defects close to the cladding layer, where significant underestimation of the distance between the top of the defect and the cladding occurs.

A layered media model for ray propagation in anisotropic inhomogeneous materials

We present a model for numerical discrete ray tracing in anisotropic inhomogeneous elastic materials. This model is an alternative to the full solution of the differential equations governing ray propagation. In the model, inhomogeneous materials are treated as layered, each layer being composed of a homogeneous, anisotropic material. We show how to choose these layers such that the exact ray solutions are obtained, illustrating this with reference to the mirage problem in isotropic materials. From this study we conclude that the layers within an inhomogeneous material should be chosen to be parallel to the local directions of constant ray group velocity magnitude. This direction can therefore depend both on the material being studied and on the ray mode and direction being considered. We discuss the incorporation of this choice into our three-dimensional ray tracing model, RAYTRAIM, and present results from this model.

Three-dimensional development of electron beam exposed resist patterns simulated by using ray tracing model

The three-dimensional ray tracing model has been used to simulate the development of electron beam exposed resist patterns. The absorbed energy density in resist film is calculated by using a three dimensional absorbed energy density function. The application of the development simulation computer program to the simulation of a single square image and a combination of four square images leads to a clear understanding of the Proximity effects.