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World Congress on Medical Physics and Biomedical Engineering

作者： Zhou, Dong Zhang, Hui Ye, Peiqing Tsinghua Univ Dept Mech Engn Beijing Peoples R China

ISBN: (纸本)9783319193878;9783319193861

Rounded leaf end effect of multileaf collimator plays a role in penumbra characteristics of dose profile. It strongly influences dose target volume conformity and organ at risk sparing for radiation therapy. Previous studies have shown that parameters in virtual source model could be fitted using dose distribution results obtained from Monte Carlo simulation or dosimetric measurement. However, there is a lack of research in literature reporting on virtual source modeling with the rounded leaf end effect incorporated. In this study, we present an analytical method for virtual source modeling by evaluation of the rounded leaf end effect of multileaf collimator on dose profile. We confine our study to single source modeling, with source energy distribution of Gaussian shaped. ray tracing algorithm is introduced and parameter estimation is conducted to revise the source size. Model verification is performed with numerical simulation, which is conducted based on the Monte Carlo codes of EGSnrc/BEAMnrc. It is shown that ray tracing algorithm employing the focal spot size of photon source would result in reduced penumbra width, compared with the simulation counterpart. This observation is probably related to the aperture effect of multileaf collimator. In contrast, results of penumbra width and radiation field edge offset using revised source size obtained with parameter estimation agree well with Monte Carlo simulation. In summary, the method we propose could provide insight into virtual source modeling using ray tracing algorithm.

关键词： ray tracing algorithm Virtual source model Multileaf collimator Rounded leaf end effect Monte Carlo simulation

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A method to test HF ray tracing algorithm in the ionosphere by means of the virtual time delay

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ADVANCES IN SPACE RESEARCH 2011年第10期48卷 1600-1605页

作者： Bianchi, Cesidio Settimi, Alessandro Scotto, Carlo Azzarone, Adriano Lozito, Angelo Ist Nazl Geofis & Vulcanol I-00143 Rome Italy

It is well known that a 3D ray tracing algorithm furnishes the ray's coordinates, the three components of the wave vector and the calculated group time delay of the wave along the path. The latter quantity can be compared with the measured group time delay to check the performance of the algorithm. Simulating a perfect reflector at an altitude equal to the virtual height of reflection, the virtual time delay is assumed as a real time delay. For a monotonic electronic density profile we find a very small relative difference between the calculated and the virtual delay for both analytic and numerical 3D electronic density models. (C) 2011 COSPAR. Published by Elsevier Ltd. All rights reserved.

关键词： ray tracing algorithm Radio wave propagation Ionospheric models

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Application of ray tracing algorithm based on intersection optimization in 3D interior design

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JOURNAL OF INTELLIGENT & FUZZY SYSTEMS 2021年第4期40卷 5787-5794页

作者： Liu, YuHan Hunan City Univ Sch Arts Yi Yang Hunan Peoples R China

Aiming at the problem that the current algorithm of lighting effect cannot achieve a good effect in 3D interior design, this paper proposes an algorithm based on multi algorithm fusion to realize lighting effect in 3D interior design. The algorithm first optimizes the intersection of patch, sphere and rectangle based on ray tracing algorithm, and then optimizes the optimization algorithm and the algorithm of lighting shadow at the same time, it is applied to the realization of lighting effect of 3D interior design. The simulation results show that the algorithm based on multi algorithm fusion is more ideal for the realization of 3D interior design lighting effect than the existing algorithm.

关键词： Interior design lighting effect ray tracing algorithm intersection optimization lighting shadow algorithm

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Evaluation of the influence of tumor location and size on the difference of dose calculation between ray tracing algorithm and Fast Monte Carlo algorithm in stereotactic body radiotherapy of non-small cell lung cancer using CyberKnife

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JOURNAL OF APPLIED CLINICAL MEDICAL PHYSICS 2013年第5期14卷 68-78页

作者： Wu, Vincent W. C. Tam, Kwok-wah Tong, Shun-ming Hong Kong Polytech Univ Dept Hlth Technol & Informat Hong Kong Hong Kong Peoples R China Hong Kong Adventist Hosp Teresa Po CyberKnife Ctr Wan Chai Hong Kong Peoples R China

This study evaluated the extent of improvement in dose predication accuracy achieved by the Fast Monte Carlo algorithm (MC) compared to the ray tracing algorithm (RAT) in stereotactic body radiotherapy (SBRT) of non-small cell lung cancer (NSCLC), and how their differences were influenced by the tumor site and size. Thirty-three NSCLC patients treated with SBRT by CyberKnife in 2011 were recruited. They were divided into the central target group (n = 17) and peripheral target group (n = 16) according to the RTOG 0236 guidelines. Each group was further divided into the large and small target subgroups. After the computation of treatment plans using RAT, a MC plan was generated using the same patient data and treatment parameters. Apart from the target reference point dose measurements, various dose parameters for the planning target volume (PTV) and organs at risk (OARs) were assessed. In addition, the "Fractional Deviation" (FDev) was also calculated for comparison, which was defined as the ratio of the RAT and MC values. For peripheral lung cases, RAT produced significantly higher dose values in all the reference points than MC. The FDev of all reference point doses and dose parameters was greater in the small target than the large target subgroup. For central lung cases, there was no significant reference point and OAR dose differences between RAT and MC. When comparing between the small target and large target subgroups, the FDev values of all the dose parameters and reference point doses did not show significant difference. Despite the shorter computation time, RAT was inferior to MC, in which the target dose was usually overestimated. RAT would not be recommended for SBRT of peripheral lung tumors regardless of the target size. However, it could be considered for large central lung tumors because its performance was comparable to MC.

关键词： ray tracing algorithm Fast Monte Carlo algorithm CyberKnife lung cancer stereotactic body radiotherapy dose calculation

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An Improved ray tracing algorithm for Ultrasonic CT in Nondestructive Inspections

An Improved Ray Tracing Algorithm for Ultrasonic CT in Nonde...

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8th International Conference on Signal Processing

作者： Wang, Bo Takatsubo, Junji Toyama, Nobuyuki Akimune, Yoshio Zhao, Mingying Agcy Ind Sci & Technol Res Inst Instrumentat Frontier 1-1-3 Higashi Tsukuba Ibaraki 3058568 Japan Xidian Univ Sch Mech Elect Engn Xian 710071 Peoples R China

ISBN: (纸本)9780780397361

Ultrasonic computerized tomography (CT) is becoming more important than C-scans in nondestructive inspection due to its rapid scanning ability. However ultrasonic CT poses challenges due to ray-bending in anisotropic media. This paper proposes an improved ray-tracing algorithm. Based on this algorithm, a bend-ray Multiplicative Algebraic Reconstruction Technique (MART) algorithm has been presented. This algorithm has been verified by numerical simulation and used for our nondestructive inspection work.

关键词： ray tracing algorithm ultrasonic CT nondestructive inspection

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Optimization of ray tracing algorithm for Laser Radar Cross Section calculation based on material Bidirectional Reflection Distribution Function

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OPTICS COMMUNICATIONS 2021年 500卷 127207-127207页

作者： Cao, Yisen Cao, Yunhua Li, Wenbo Bai, Lu Wu, Zhensen Wang, Zhe Xidian Univ Sch Phys & Optoelect Engn Xian 710071 Peoples R China

This paper studied the Laser Radar Cross Section (LRCS) of the target scale model by using the Bidirectional Reflection Distribution Function (BRDF) of materials and the Monte Carlo method for reverse ray tracing. The results of the research are shown through data from the satellite scale model. On the basis of the classification of the roughness of different materials and in conjunction with probability density distribution, we adopted a non-uniform sampling method to improve the split-ray collection method in the spatial distribution of scattering energy in the reverse ray tracing algorithm. By conducting the typical Monte Carlo simulation of a simple dihedron and comparing the theoretical calculation results, we tested and verified the correctness of the proposed method. We analyzed the difference between the primary and secondary scattering results of the target LRCS with different conditions. The calculation results show that for rough materials, if only primary scattering is considered in a plurality of detection directions, a large calculation error will occur, so the influence of the secondary scattering must be considered;and the contribution of the diffuse reflection component to the secondary scattering is more significant. Finally, we compared the secondary scattering of different rough materials to describe the circumstances of secondary scattering in which diffuse reflection conditions need to be considered. In addition, the inverse Monte Carlo method used in this paper to calculate the multiple scattering of the LRCS of the target can effectively improve the calculation speed of the acquisition processing. This improves the reliability of the calculation results while taking into account the estimated speed.

关键词： Laser Radar Cross Section Secondary scattering ray tracing algorithm

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An Improved ray tracing algorithm for Ultrasonic CT in Nondestructive Inspections

An Improved Ray Tracing Algorithm for Ultrasonic CT in Nonde...

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2006 8th International Conference on Signal Processing

作者： Bo Wang JUNJI Takatsubo Nobuyuki Toyama Yoshio Akimune Mingying Zhao Research Institute of Instrumentation Frontier AISTTsukuba 305-8568Japan School of Mechano-Electronic Engineering Xidian University

Ultrasonic computerized tomography(CT) is becoming more important than C-scans in nondestructive inspection due to its rapid scanning ***,ultrasonic CT poses challenges due to ray-bending in anisotropic *** paper proposes an improved ray-tracing *** on this algorithm,a bend-ray Multiplicative Algebraic Reconstruction Technique(MART) algorithm has been *** algorithm has been verified by numerical simulation and used for our nondestructive inspection work.

关键词： ray tracing algorithm Ultrasonic CT Nondestructive inspection

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Enhancement Approach of ray-tracing algorithm for Propagation prediction at the MM-Wave Band

Enhancement Approach of Ray-tracing Algorithm for Propagatio...

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35th International Conference on Infrared, Millimeter and Terahertz Waves

作者： Jung, Myoung-Won Kim, Jongho Yoon, YoungKeun Kim, Jeong-Wook Kim, Seong-Cheol ETRI Radio Technol Anal Dept Taejon 305700 South Korea Seoul Natl Univ DoEE Seoul 151742 South Korea Seoul Natl Univ INMC Seoul 151742 South Korea

ISBN: (纸本)9781424466573

The reflection characteristics of building materials at the millimeter (MM) wave band are needed for development MM-wave application such as Giga-bytes indoor communication systems. Because reflection characteristics in the MM-wave band is dependent on the condition of measurement environments and has so little measurement data. To enhance these problems, we have studied propagation characteristics in the MM-wave band. In this paper, we set up the measurement system and measured the propagation characteristics of samples with periodic and random rough surfaces. Their results compared with measurement and simulation results at the 60 GHz. We have numerical simulation for dependence of electrical property. Also, the energy estimation of scattered reflection according to the rough surfaces simulated. Finally, we propose the simple approach (2 ray path model) for ray-tracing algorithm. This approach can be directly applied to the estimation of multipath signal strength in ray tracing by weighting factor for propagation prediction.

关键词： Giga-bytes indoor communication system MM-wave band building materials electrical property energy estimation measurement system millimeter wave band millimetre waves multipath signal strength numerical simulation propagation prediction ray tracing ray tracing algorithm rough surface

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Massive MIMO Channel Modeling Using Map based ray tracing Method 7

Massive MIMO Channel Modeling Using Map based Ray Tracing Me...

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7th IEEE International Symposium on Microwave, Antenna, Propagation, and EMC Technologies (MAPE)

作者： Yao, Junliang Ren, Haipeng Liu, Qing Xian Univ Technol Shaanxi Key Lab Complex Syst Control & Intelligen Xian 710048 Shaanxi Peoples R China

ISBN: (纸本)9781509059294

Massive multiple-input multiple-output (MIMO), with giant array size and multi-dimension array structure, has been widely considered as a key physical layer technique in future wireless communications. With regarding the large number of antenna elements, some new challenges and issues are arising, e.g. modeling the near-field effects in MIMO channel and the high computational complexity. To solve these problems, a statistical channel model is proposed based on the cluster delay line (CDL) framework. The proposed model focuses on the spherical wavefront theory, thus can he applied to the massive MIMO system. Furthermore, the map-based ray tracing algorithm with low complexity is used to compute the statistical parameters, such as pathloss, delay spread, etc., The numerical analysis results show that the proposed channel model is enable to describe the main characteristics of massive MIMO channel.

关键词： large scale MIMO wireless channel modeling ray tracing algorithm path loss delay spread

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Physics of humping formation in laser powder bed fusion

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INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER 2020年第0期149卷 119172-000页

作者： Tang, C. Le, K. Q. Wong, C. H. Nanyang Technol Univ Singapore Ctr 3D Printing Sch Mech & Aerosp Engn 50 Nanyang Ave Singapore 639798 Singapore

Despite of the promising attributes of laser powder bed fusion, part quality such as porosity and surface roughness remains a critical issue for industrial applications. Humping is a surface defect that may greatly deteriorate the mechanical performances of as-built components. However, current understanding of humping formation remains vague and unclear. In this respect, laser powder bed fusion of stainless steel 316 L single tracks was simulated by using computational fluid dynamics. With the same linear energy density, the simulated tracks exhibit irregular humps at high scanning velocities, which is validated against experiments. In addition, flow kinetics was analyzed to elucidate the physical origins of humping formation during printing process. The study reveals the various effects of surface tension, Marangoni shear force, viscous force and recoil pressure on the humping phenomenon in laser powder bed fusion. At relatively high scanning speed, a swelling with large contact angle is formed due to the competition between surface tension and flow inertia. Capillary instability divides the swelling into separated regions, which is responsible for the humping formation during printing process. (C) 2019 Elsevier Ltd. All rights reserved.

关键词： ray tracing algorithm Laser powder bed fusion Additive manufacturing Humping Computational fluid dynamics Surface morphology

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