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The Implementation of Ray Tracing Algorithm with OpenMP Parallelization
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作者 Noor Alnasser Raghad Alabssi +2 位作者 Batool Faran Latifah Alessa Naya Nagy 《Journal of Computer and Communications》 2024年第1期120-130,共11页
Ray tracing is a computer graphics method that renders images realistically. As the name suggests, this technique primarily traces the path of light rays interacting with objects in a scene [1], permitting the calcula... Ray tracing is a computer graphics method that renders images realistically. As the name suggests, this technique primarily traces the path of light rays interacting with objects in a scene [1], permitting the calculation of lighting and reflecting impact [2]. As ray tracing is a time-consuming process, the need for parallelization to solve this problem arises. One downside of this solution is the existence of race conditions. In this work, we explore and experiment with a different, well-known solution for this race condition. Starting with the introduction and the background section, a brief overview of the topic is followed by a detailed part of how the race conditions may occur in the case of the ray tracing algorithm. Continuing with the methods and results section, we have used OpenMP to parallelize the Ray tracing algorithm with the different compiler directives critical, atomic, and first-private. Hence, it concluded that both critical and atomic are not efficient solutions to produce a good-quality picture, but first-private succeeded in producing a high-quality picture. 展开更多
关键词 PARALLELIZATION ray tracing Parallel Computer Architecture OPENMP
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Point cloud-based environment reconstruction and ray tracing simulations for railway tunnel channels
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作者 Ziyi Qi Ruisi He +6 位作者 Mi Yang Xuejian Zhang Bo Ai Weiming Li Shaopeng Wang Wenpu Sun Lizhe Li 《High-Speed Railway》 2023年第4期241-247,共7页
Radio propagation environment plays a critical role in the performance of wireless communication systems,and understanding channel characteristics is vital for ensuring reliable communication links and optimizing syst... Radio propagation environment plays a critical role in the performance of wireless communication systems,and understanding channel characteristics is vital for ensuring reliable communication links and optimizing system performance.Ray tracing is an effective method to investigate propagation characteristics in a complex environment,and how to quickly and accurately obtain environmental information needs to be solved.This paper presents dynamic environment reconstruction and ray tracing simulation in railway tunnel environment based on Simultaneous Localization and Mapping(SLAM)algorithm and Poisson reconstruction algorithm.Accurate channel parameters are obtained and analyzed based on ray tracing simulation.Both straight and curved tunnels are considered and investigated,and the results show the channel characteristics in complex railway tunnel environments. 展开更多
关键词 Railway communication TUNNELS ray tracing Environment reconstruction Wireless channel
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X-ray在鱼体组织及微量元素检测中的应用
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作者 宋一帆 张胜茂 +4 位作者 张衡 唐峰华 张寒野 石永闯 崔雪森 《应用光学》 CAS 北大核心 2024年第1期166-176,共11页
鱼类硬质组织物,特别是骨骼支持鱼体和保护其体内器官的组织,对其进行特征检测分析是研究鱼类游泳运动、鱼类解剖、鱼体建模等的数据基础。随着X-ray技术的发展和国产设备的广泛应用,其仪器设备成本明显降低,使得X-ray在渔业研究与自动... 鱼类硬质组织物,特别是骨骼支持鱼体和保护其体内器官的组织,对其进行特征检测分析是研究鱼类游泳运动、鱼类解剖、鱼体建模等的数据基础。随着X-ray技术的发展和国产设备的广泛应用,其仪器设备成本明显降低,使得X-ray在渔业研究与自动化生产中的应用成为可能。首先介绍了X-ray技术的基本原理与其在鱼体组织检测中的应用,X-ray技术在鱼体组织及微量元素检测中的应用主要分为鱼类组织器官的无损检测和鱼体微量元素检测两部分,其中分别介绍了包括照相法、数字成像法、衍射技术和吸收光谱法等X-ray技术;然后综述其在鱼体组织器官建模、鱼骨检测、鱼类化石研究、鱼耳石分析和鱼体微量元素检测方面的应用,总结了Xray在渔业领域应用中存在的问题;最后对X-ray的渔业应用方向进行展望。 展开更多
关键词 X-ray 鱼体骨骼 鱼类耳石 鱼体建模 鱼体微量元素
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Fast X-ray imaging beamline at SSRF
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作者 Ke Li Hong-Lan Xie +5 位作者 Ya-Nan Fu Fei-Xiang Wang Guo-Hao Du Jian-Feng ji Biao Deng Ti-Qiao Xiao 《Nuclear Science and Techniques》 SCIE EI CAS CSCD 2024年第9期68-81,共14页
The fast X-ray imaging beamline(BL16U2)at Shanghai Synchrotron Radiation Facility(SSRF)is a new beamline that provides X-ray micro-imaging capabilities across a wide range of time scales,spanning from 100 ps toμs and... The fast X-ray imaging beamline(BL16U2)at Shanghai Synchrotron Radiation Facility(SSRF)is a new beamline that provides X-ray micro-imaging capabilities across a wide range of time scales,spanning from 100 ps toμs and ms.This beamline has been specifically designed to facilitate the investigation of a wide range of rapid phenomena,such as the deformation and failure of materials subjected to intense dynamic loads.In addition,it enables the study of high-pressure and high-speed fuel spray processes in automotive engines.The light source of this beamline is a cryogenic permanent magnet undulator(CPMU)that is cooled by liquid nitrogen.This CPMU can generate X-ray photons within an energy range of 8.7-30 keV.The beamline offers two modes of operation:monochromatic beam mode with a liquid nitrogen-cooled double-crystal monochromator(DCM)and pink beam mode with the first crystal of the DCM out of the beam path.Four X-ray imaging methods were implemented in BL16U2:single-pulse ultrafast X-ray imaging,microsecond-resolved X-ray dynamic imaging,millisecond-resolved X-ray dynamic micro-CT,and high-resolution quantitative micro-CT.Furthermore,BL16U2 is equipped with various in situ impact loading systems,such as a split Hopkinson bar system,light gas gun,and fuel spray chamber.Following the completion of the final commissioning in 2021 and subsequent trial operations in 2022,the beamline has been officially available to users from 2023. 展开更多
关键词 Multiple time-scale X ray imaging Single-pulse X ray imaging Dynamic 2D imaging Dynamic micro-CT
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Genetic Enhancement of Indigenous Cowpea with Gamma-Ray Induced Trait Variation
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作者 Mathurin Tiergnin Dabiré Minimassom Philippe Nikiéma +10 位作者 Djibril Yonli Safiatou Sanna Wossoguim Josué Gouba Siébou Palé Hamidou Traoré Joseph T. B. Batieno Varra Prasad Zacharia Stewart Jan B. Middendorf Abhishek Rathore Anupama J. Hingane 《American Journal of Plant Sciences》 CAS 2024年第8期651-676,共26页
Production of cowpea (Vigna unguiculata (L.) Walp.), a staple legume crop in Sub-Saharan Africa, faces challenges due to biotic and abiotic constraints. Induced mutagenesis was deployed to create genetic variation in ... Production of cowpea (Vigna unguiculata (L.) Walp.), a staple legume crop in Sub-Saharan Africa, faces challenges due to biotic and abiotic constraints. Induced mutagenesis was deployed to create genetic variation in two cowpea varieties (KVX396-4-5-2D and Moussa local). The radio-sensitivity tests led to determe the lethal dose 50 (LD50) corresponding to 230 Gy and 220 Gy for KVX396-4-5-2D and Moussa local varieties, respectively. Dried seeds (M0) of each variety were gamma-ray irradiated with LD50 − 50, LD50 and LD50 + 50. M1 seeds were advanced to generate M2, M3 and M4 mutants using the single-seed-descent method. M4 mutant lines were evaluated in rain-fed conditions using a randomized complete block design to assess phenotypic differences. Data on seven qualitative and eleven quantitative traits were collected. The results indicated that the mutation induced variability in three qualitative traits: in KVX 396-4-5-2D mutant lines, with flower and seed color frequencies at 2.61% and 0.56% respectively, and pod dehiscence at a frequency of 0.24%. While in Moussa local mutants, a pod color changed at a frequency of 17%. ANOVA results revealed significant differences between mutants of both varieties for all quantitative traits, including photosynthetic parameters. Positive correlations were observed between leaf diameter and 100-seed weight, and between branch number and 100-seed weight. Hierarchical clustering revealed three clusters among KVX 396-4-5-2D mutants and six clusters among Moussa local mutants. Early maturity and high foliage were induced traits in Cluster 3 of KVX 396-4-5-2D mutants while high hundred-seed weight was induced in Cluster 6 of Moussa local mutants. 展开更多
关键词 COWPEA MUTAGENESIS Gamma rays Radio-Sensitivity PHENOTYPING
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Study on the Performance of the GRANDProto300 Particle Detector Array by Simulation
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作者 Fu-Lin Dai Quan-Bu Gou +1 位作者 Xiaoyuan Huang Yi-Qing Guo 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2024年第1期173-177,共5页
The Giant Radio Array for Neutrino Detection(GRAND)is a proposed large-scale observatory designed to detect cosmic rays,gamma-rays,and neutrinos with energies exceeding 100 Pe V.The GRANDProto300 experiment is propose... The Giant Radio Array for Neutrino Detection(GRAND)is a proposed large-scale observatory designed to detect cosmic rays,gamma-rays,and neutrinos with energies exceeding 100 Pe V.The GRANDProto300 experiment is proposed as the early stage of the GRAND project,consisting of a hybrid array of radio antennas and scintillator detectors.The latter,as a mature and traditional detector,is used to cross-check the nature of the candidate events selected from radio observations.In this study,we developed a simulation software called G4GRANDProto300,based on the Geant4 software package,to optimize the spacing of the scintillator detector array and to investigate its effective area.The analysis was conducted at various zenith angles under different detector spacings,including 300,500,600,700,and 900 m.Our results indicate that,for large zenith angles used to search for cosmic-ray in the GRAND project,the optimized effective area is with a detector spacing of 500 m.The G4GRANDProto300 software that we developed could be used to further optimize the layout of the particle detector array in future work. 展开更多
关键词 astroparticle physics instrumentation:detectors (ISM:)cosmic rays
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In-beam gamma rays of CSNS Back-n characterized by black resonance filter
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作者 Jin-Cheng Wang Jie Ren +68 位作者 Wei Jiang Xi-Chao Ruan Ying-Yi Liu Hao-Lan Yang Kuo-Zhi Xu Xin-Yi Pan Qi Sun Jie Bao Han-Xiong Huang Hao-Fan Bai Jiang-Bo Bai Ping Cao Qi-Ping Chen Yong-Hao Chen Wen-Hao Duan An-Chuan Fan Rui-Rui Fan Chang-Qing Feng Min-Hao Gu Chang-Cai Han Zi-Jie Han Guo-Zhu He Yong-Cheng He Yang Hong Yi-Wei Hu Zhi-Jie Jiang Ling Kang Chang-Lin Lan Bo Li Feng Li Qiang Li Xiao Li Yang Li Jie Liu Rong Liu Shu-Bin Liu Yi-Na Liu Guang-Yuan Luan Chang-Jun Ning Yi-Jia Qiu Wen-Kai Ren Zhi-Zhou Ren Zhao-Hui Song Kang Sun Zhi-Xin Tan Jing-Yu Tang Sheng-Da Tang Li-Jiao Wang Peng-Cheng Wang Zhao-Hui Wang Zhong-Wei Wen Xiao-Guang Wu Xuan Wu Ze-Peng Wu Cong Xia Li-Kun Xie Han Yi Tao Yu Yong-Ji Yu Guo-Hui Zhang Hang-Chang Zhang Qi-Wei Zhang Xian-Peng Zhang Yu-Liang Zhang Zhi-Yong Zhang Mao-Yuan Zhao Zhi-Hao Zhou Ke-Jun Zhu Chong Zou 《Nuclear Science and Techniques》 SCIE EI CAS CSCD 2024年第10期149-160,共12页
The back-streaming white-neutron beamline(Back-n)of the China Spallation Neutron Source is an essential neutronresearch platform built for the study of nuclear data,neutron physics,and neutron applications.Many types ... The back-streaming white-neutron beamline(Back-n)of the China Spallation Neutron Source is an essential neutronresearch platform built for the study of nuclear data,neutron physics,and neutron applications.Many types of cross-sectional neutron-reaction measurements have been performed at Back-n since early 2018.These measurements have shown that a significant number of gamma rays can be transmitted to the experimental stations of Back-n along with the neutron beam.These gamma rays,commonly referred to as in-beam gamma rays,can induce a non-negligible experimental background in neutron-reaction measurements.Studying the characteristics of in-beam gamma rays is important for understanding the experimental background.However,measuring in-beam gamma rays is challenging because most gamma-ray detectors are sensitive to neutrons;thus,discriminating between neutron-induced signals and those from in-beam gamma rays is difficult.In this study,we propose the use of the black resonance filter method and a CeBr_(3) scintillation detector to measure the characteristics of the in-beam gamma rays of Back-n.Four types of black resonance filters,^(181)Ta,^(59)Co,^(nat)Ag,and^(nat)Cd,were used in this measurement.The time-of-flight(TOF)technique was used to select the detector signals remaining in the absorption region of the TOF spectra,which were mainly induced by in-beam gamma rays.The energy distribution and flux of the in-beam gamma rays of Back-n were determined by analyzing the deposited energy spectra of the CeBr_(3) scintillation detector and using Monte Carlo simulations.Based on the results of this study,the background contributions from in-beam gamma rays in neutron-reaction measurements at Back-n can be reasonably evaluated,which is beneficial for enhancing both the experimental methodology and data analysis. 展开更多
关键词 In-beam gamma rays Back-n CeBr_(3)scintillator Black filter resonance technique
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The 111-Years-Old Cosmic Ray Puzzle Has Been Solved?
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作者 Shlomo Dado Arnon Dar 《Journal of Modern Physics》 2024年第1期125-131,共7页
We show that recently multi-messenger astronomy has provided compelling evidence that the bulk of high energy cosmic rays (CRs) are produced by highly relativistic narrow jets of plasmoids launched in core collapse of... We show that recently multi-messenger astronomy has provided compelling evidence that the bulk of high energy cosmic rays (CRs) are produced by highly relativistic narrow jets of plasmoids launched in core collapse of stripped-envelope massive stars to neutron stars and stellar mass black holes. Such events produce also a visible GRB if the jet happens to point in our direction. This has been long advocated by the cannon ball (CB) model of high energy CRs and GRBs, but the evidence has been provided only recently by what were widely believed to be unrelated discoveries. They include the very recent discovery of a knee around TeV in the energy spectrum of high energy CR electrons, the peak photon energy in the “brightest of all time” GRB221009A, and the failure of IceCube to detect high energy neutrinos from GRBs, including GRB221009A. They were all predicted by the cannonball (CB) model of high energy CRs and GRBs long before they were discovered in observations, despite a negligible probability to occur by chance. 展开更多
关键词 Cosmic rays Gamma ray Bursts Neutrino Bursts
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Comparison of efficacy of lung ultrasound and chest X-ray in diagnosing pulmonary edema and pleural effusion in ICU patients: A single centre, prospective, observational study
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作者 Kunal Tewari Sumanth Pelluru +5 位作者 Deepak Mishra Nitin Pahuja Akash Ray Mohapatra Jyotsna Sharma Om Bahadur Thapa Manjot Multani 《Open Journal of Anesthesiology》 2024年第3期41-50,共10页
Background and Aims While chest X-ray (CXR) has been a conventional tool in intensive care units (ICUs) to identify lung pathologies, computed tomography (CT) scan remains the gold standard. Use of lung ultrasound (LU... Background and Aims While chest X-ray (CXR) has been a conventional tool in intensive care units (ICUs) to identify lung pathologies, computed tomography (CT) scan remains the gold standard. Use of lung ultrasound (LUS) in resource-rich ICUs is still under investigation. The present study compares the utility of LUS to that of CXR in identifying pulmonary edema and pleural effusion in ICU patients. In addition, consolidation and pneumothorax were analyzed as secondary outcome measures. Material and Methods This is a prospective, single centric, observational study. Patients admitted in ICU were examined for lung pathologies, using LUS by a trained intensivist;and CXR done within 4 hours of each other. The final diagnosis was ascertained by an independent senior radiologist, based on the complete medical chart including clinical findings and the results of thoracic CT, if available. The results were compared and analyzed. Results Sensitivity, specificity and diagnostic accuracy of LUS was 95%, 94.4%, 94.67% for pleural effusion;and 98.33%, 97.78%, 98.00% for pulmonary edema respectively. Corresponding values with CXR were 48.33%, 76.67%, 65.33% for pleural effusion;and 36.67%, 82.22% and 64.00% for pulmonary edema respectively. Sensitivity, specificity and diagnostic accuracy of LUS was 91.30%, 96.85%, 96.00% for consolidation;and 100.00%, 79.02%, 80.00% for pneumothorax respectively. Corresponding values with CXR were 60.87%, 81.10%, 78.00% for consolidation;and 71.3%, 97.20%, 96.00% for pneumothorax respectively. Conclusion LUS has better diagnostic accuracy in diagnosis of pleural effusion and pulmonary edema when compared with CXR and is thus recommended as an effective alternative for diagnosis of these conditions in acute care settings. Our study recommends that a thoracic CT scan can be avoided in most of such cases. 展开更多
关键词 Chest X ray (CXR) CONSOLIDATION Pulmonary edema Pleural effusion Lung ultrasound (LUS) PNEUMOTHORAX
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Revisit of GeV Gamma-Ray Emission from Orion B with the Fermi Large Area Telescope
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作者 Wei Zeng Xiao-Na Sun +5 位作者 Rui-Zhi Yang Jia-Chun He Zhao-Dong Shi Ting-Ting Ge Yun-Feng Liang En-Wei Liang 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2024年第9期128-135,共8页
We revisit the γ-ray emission above 300 Me V towards the massive star-forming region of Orion B by adopting14 yr observations with the Fermi Large Area Telescope and utilizing the updated software tools.The extended ... We revisit the γ-ray emission above 300 Me V towards the massive star-forming region of Orion B by adopting14 yr observations with the Fermi Large Area Telescope and utilizing the updated software tools.The extended γ-ray emission region around Orion B is resolved into two components(region Ⅰ and region Ⅱ).The γ-ray spectrum of region I agrees with the predicted γ-ray spectrum assuming the cosmic ray(CR)density is the same as that of Alpha Magnetic Spectrometer(AMS-02)measured locally.Theγ-ray emissivity of region II appears to be deficit at low energy band(E<3 GeV).Through modeling we find that CR densities exhibit a significant deficit below 20 Ge V,which may be caused by a slow diffusion inside the dense region.This is probably caused by an increased magnetic field whose strength increases with the gas density. 展开更多
关键词 (ISM:)cosmic rays gamma-rays:ISM (Galaxy:)open clusters and associations:individual(NGC 2023 NGC 2024 NGC 2068 and NGC 2071)
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Transport in Astrophysics: VI. Ultra-High Energy Cosmic Rays
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作者 Lorenzo Zaninetti 《International Journal of Astronomy and Astrophysics》 2024年第1期65-84,共20页
Two new solutions of the homogeneous diffusion equation in 1D are derived in the presence of losses and a trigonometric profile for a profile of density. A simulation for the ankle in the energy distribution of cosmic... Two new solutions of the homogeneous diffusion equation in 1D are derived in the presence of losses and a trigonometric profile for a profile of density. A simulation for the ankle in the energy distribution of cosmic rays (CRs) is provided in the framework of the fine tuning of the involved parameters. A theoretical image for the overall diffusion of CRs in galactic coordinates is provided. 展开更多
关键词 Cosmic rays Particle Diffusion Random Walks
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A minimum traveltime ray tracing global algorithm on a triangular net for propagating plane waves 被引量:1
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作者 于师建 刘润泽 程久龙 《Applied Geophysics》 SCIE CSCD 2010年第4期348-356,400,共10页
To address the problem of subdividing inflexible rectangular grid models and their poor definition of velocity interfaces,we propose a complex structure triangular net for a minimum traveltime ray tracing global algor... To address the problem of subdividing inflexible rectangular grid models and their poor definition of velocity interfaces,we propose a complex structure triangular net for a minimum traveltime ray tracing global algorithm.Our procedure is:(1) Subdivide a triangle grid based on the Delaunay triangular subdivision criterion and the relationships of the points,lines,and the surfaces in the subdividing area.(2) Define the topology relationships and related concepts of triangular unit ray tracing.(3) The source point and wave arrival points at any time compose the propagating plane wave and the minimum traveltime and secondary source positions are calculated during the plane wave propagation.We adopt the hyperbolic approximation global algorithm for secondary source retrieving.(4) By minimum traveltime ray tracing,collect the path from receiver to source points with the neighborhood point's traveltime and the direction of the secondary source.Numerical simulation examples are given to test the algorithm.The results show that the triangular net ray tracing method demonstrates model subdivision flexibility,precise velocity discontinuity interfaces,and accurate computations. 展开更多
关键词 triangular net ray tracing plane wave propagation secondary source
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A Fast Algorithm for Ray Tracing
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作者 Tang Gangdou and Zhong PengxiangBeijing Institute of Data Processing Technology 《Journal of Systems Engineering and Electronics》 SCIE EI CSCD 1992年第2期49-56,共8页
A fast algorithm for ray tracing is presented, with which the specular reflection term of global illumination model is improved. A hybrid technique combining hierarchical bounding volumes and constant size box partiti... A fast algorithm for ray tracing is presented, with which the specular reflection term of global illumination model is improved. A hybrid technique combining hierarchical bounding volumes and constant size box partitioning is presented and a fast box traversal algorithm is used. By this technique multiple ray intersections with objects that are in more than one box can be avoided. As a result, the speed of ray tracing is considerably increased. 展开更多
关键词 Global illumination model Hierarchical bounding volume Space partitioning ray tracing.
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射波刀Monte Carlo与Ray-Tracing算法在胰腺癌中的剂量学比较 被引量:4
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作者 曹洋森 于春山 +1 位作者 张火俊 孙永健 《中国医学物理学杂志》 CSCD 2016年第10期1008-1011,共4页
目的:对比射波刀Monte Carlo(MC)算法与Ray-Tracing(RT)算法在胰腺癌中的剂量学差异。方法:回顾分析50例射波刀治疗的胰腺癌患者,行CT模拟定位并勾画靶区和危及器官。分别使用RT算法和MC算法进行剂量计算和评估。比较两种算法计算的靶... 目的:对比射波刀Monte Carlo(MC)算法与Ray-Tracing(RT)算法在胰腺癌中的剂量学差异。方法:回顾分析50例射波刀治疗的胰腺癌患者,行CT模拟定位并勾画靶区和危及器官。分别使用RT算法和MC算法进行剂量计算和评估。比较两种算法计算的靶区剂量、适形指数(CI)、新适形指数(n CI)、均匀指数(HI)和危及器官受量。结果:两种算法计算出PTV D_(90)的差异很小,没有统计学意义。使用MC算法精算后CI和n CI比RT算法平均减小了0.01,胃、十二指肠、空回肠、脊髓的体积剂量分别降低了0.61、0.53、0.60、0.68、1.10 Gy,差异均具有统计学意义。结论:胰腺癌射波刀治疗计划中MC算法与RT算法在PTV D_(90)的差异不大,RT算法比MC算法高估了胃、十二指肠、空回肠、脊髓的剂量。 展开更多
关键词 射波刀 射线追踪 蒙特卡罗 剂量分布 胰腺癌
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基于Ray Tracing的数字植株冠层光照分布研究 被引量:1
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作者 张晶 师翊 +3 位作者 胡少军 张志毅 刘斌 耿楠 《农机化研究》 北大核心 2019年第1期26-33,共8页
针对植株冠层光照模型精度不高、采集效率低的问题,提出了一种基于Ray Tracing的数字植株冠层光照分布计算方法。首先,通过Kinect 2.0获取两种盆栽植株的三维点云,对其进行预处理和三维重建;其次,通过改进的光线跟踪技术模拟植株冠层光... 针对植株冠层光照模型精度不高、采集效率低的问题,提出了一种基于Ray Tracing的数字植株冠层光照分布计算方法。首先,通过Kinect 2.0获取两种盆栽植株的三维点云,对其进行预处理和三维重建;其次,通过改进的光线跟踪技术模拟植株冠层光照分布;然后,分析了不同时刻模拟植株累计光强与真实植株实际光照强度之间的关系。实验结果表明:两种植株的模拟光强与真实光强的RMSE分别为0.187 2和0.118 5,因此该方法具有实时性和可行性,可以为植株提供较为科学合理的整形和修剪参考。 展开更多
关键词 植株冠层 点云获取 点云重建 光线跟踪 光照分布
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基于Ray Tracing理论的海洋信道分析方法
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作者 赵华 郭平文 +1 位作者 李传岗 戴树良 《舰船电子工程》 2009年第5期127-129,160,共4页
ray tracing理论源于几何光学,将其引入海洋传输信道分析,在约当算法、帐篷定律等算法的支撑下,较好地解决了海洋环境与海洋信道的关系问题,为海上用频装备的合理使用提供了便利条件。
关键词 射线跟踪理论 海洋信道 信道分析
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Target-oriented Gaussian beam migration using a modif ied ray tracing scheme 被引量:5
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作者 Rui Zhang Jian-Ping Huang +1 位作者 Su-Bin Zhuang Zhen-Chun Li 《Petroleum Science》 SCIE CAS CSCD 2019年第6期1301-1319,共19页
For large-scale 3D seismic data,target-oriented reservoir imaging is more attractive than conventional full-volume migration,in terms of computation efficiency.Gaussian beam migration(GBM)is one of the most robust dep... For large-scale 3D seismic data,target-oriented reservoir imaging is more attractive than conventional full-volume migration,in terms of computation efficiency.Gaussian beam migration(GBM)is one of the most robust depth imaging method,which not only keeps the advantages of ray methods,such as high efficiency and flexibility,but also allows us to solve caustics and multipathing problems.But conventional Gaussian beam migration requires slant stack for prestack data,and ray tracing from beam center location to subsurface,which is not easy to be directly applied for target-oriented imaging.In this paper,we modify the conventional Gaussian beam migration scheme,by shooting rays from subsurface image points to receivers to implement wavefield back-propagation.This modification helps us to achieve a better subsurface illumination in complex structure and allows simple implementation for target reservoir imaging.Significantly,compared with the wavefi eld-based GBM,our method does not reconstruct the subsurface snapshots,which has higher efficiency.But the proposed method is not as efficient as the conventional Gaussian beam migration.Synthetic and field data examples demonstrate the validity and the target-oriented imaging capability of our method. 展开更多
关键词 Gaussian beam migration Target-oriented imaging ILLUMINATION ray tracing
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Influence of Cy berKnife Prescription Isodose Line on the Discrepancy of Dose Results Calculated by the Ray Tracing and Monte Carlo Algorithms for Head and Lung Plans: A Phantom Study 被引量:2
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作者 Jing YANG Gang LIU +5 位作者 Hong-yuan LIU Xin NIE Zhi-yong YANG Jun HAN Sheng ZHANG Zhi-wen LIANG 《Current Medical Science》 SCIE CAS 2020年第2期301-306,共6页
Incorporation of the Monte Carlo(MC)algorithm in optimizing CyberKnife(CK)plans is cumbersome,and early models unconfigured MC calculations,therefore,this study investigated algorithm-based dose calculation discrepanc... Incorporation of the Monte Carlo(MC)algorithm in optimizing CyberKnife(CK)plans is cumbersome,and early models unconfigured MC calculations,therefore,this study investigated algorithm-based dose calculation discrepancies by selecting different prescription isodose lines(PIDLs)in head and lung CK plans.CK plans were based on anthropomorphic phantoms.Four shells were set at 2-60 mm from the target,and the constraint doses were adjusted according to the design stratcgy.After optimization,30%-90%PIDL plans were generated by ray tracing(RT).In the evaluation module,CK plans were recalculated using the MC algorithm.Therefore,the dosimetric parameters of different PIDL plans based on the RT and MC algorithms were obtained and analyzed.The discrepancies(mean+SD)were 3.72%+0.31%,3.40%+0.11%,3.47%+0.32%,0.17%+0.11%,0.64%+3.60%,7.73%+1.60%,14.62%+3.21%and 10.10%+1.57%for Djs,Dmeam),Dys,and coverage of the PTV,DGI,V,,V;and V,in the head plans and-6.32%+1.15%,-13.46%+0.98%,-20.63%+2.25%,-34.78%+25.03%,12248%+175.60%,-12.92%+5.41%,3.19%+4.67%and 7.13%+1.56%in the lung plans,respectively.The following parameters were significantly correlated with PIDL:dp98%at the 0.05 level and dpal,dys and dv3 at the 0.01 level for the head plans;dp98e%at the 0.05 level and do1e%,dpmeam,Ccoweange,dool,dvs and dv;at the 0.01 level for the lung plans.RT may be used to calculate the dose in CK head plans,but when the dose of organs at risk is close to the limit,it is necessary to refer to the MC results or to further optimize the CK plan to reduce the dose.For lung plans,the MC algorithm is recommended.For early models without the MC algorithm,a lower PIDL plan is recommended;otherwise,a large PIDL plan risks serious underdosage in the target area. 展开更多
关键词 CYBERKNIFE prescription isodose line Monte Carlo ray tracing PHANTOM
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Fast ray tracing method in 3-D structure and its proof of positive definiteness 被引量:2
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作者 高尔根 Uk HAN 滕吉文 《Journal of Central South University of Technology》 EI 2007年第1期100-103,共4页
Based on Fermat’s principle, two-point ray tracing method was studied in three-dimensional structure. By means of first order Taylor’s incomplete series expansion (i.e. no expansion to the length of the ray), a symm... Based on Fermat’s principle, two-point ray tracing method was studied in three-dimensional structure. By means of first order Taylor’s incomplete series expansion (i.e. no expansion to the length of the ray), a symmetry block tridiagonal matrix equation set was deduced. Further, the positive definiteness of coefficient matrix was discussed, and the positive definiteness was accurately proved in a mathematical way. It assured that the algorithm was well-posed. Associated with iterative method, the solution to ray tracing can be got through step-by-step linearized iteration of the nonlinear problem. An algorithm of the whole path iterative ray tracing method in three-dimensional velocity structure was obtained. This method shows a clear and simple as well as explicit computation formula, which makes ray tracing computation easily applicable in practice. The correction vector is obtained through finding the solution to the positive definite block tridiagonal equation set, which ensures the method is robust convergence. This study offers a new kind of feasible and efficient ray tracing method for three dimensional seismic migration and tomography. Meanwhile, it also provides the prerequisite guarantee to design a fast algorithm. 展开更多
关键词 Fermat's principle ray tracing ray path POSITIVITY seismic migration TOMOGRAPHY
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基于Phong和Fresnel的Ray Tracing模型的研究与应用
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作者 李尚林 杨柳青 《湘南学院学报》 2012年第5期55-59,92,共6页
初步探讨使用Phong模型渲染物体表面,并用Fresnel算法的思想实现折射处理的光线跟跟踪模型,并尝试使用全屏抗锯齿对渲染效果进行优化,最后给出该模型的测试数据与性能分析.
关键词 光线跟踪 Phong FRESNEL 全屏抗锯齿
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