The Implementation of Ray Tracing Algorithm with OpenMP Parallelization

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.

A rabies virus-based toolkit for efficient retrograde labeling and monosynaptic tracing

Analyzing the structure and function of the brain's neural network is critical for identifying the working principles of the brain and the mechanisms of brain diseases.Recombinant rabies viral vectors allow for the retrograde labeling of projection neurons and cell type-specific trans-monosynaptic tracing,making these vectors powerful candidates for the dissection of synaptic inputs.Although several attenuated rabies viral vectors have been developed,their application in studies of functional networks is hindered by the long preparation cycle and low yield of these vectors.To overcome these limitations,we developed an improved production system for the rapid rescue and preparation of a high-titer CVS-N2c-ΔG virus.Our results showed that the new CVS-N2c-ΔG-based toolkit performed remarkably:(1)N2cG-coated CVS-N2c-ΔG allowed for efficient retrograde access to projection neurons that were unaddressed by rAAV9-Retro,and the efficiency was six times higher than that of rAAV9-Retro;(2)the trans-monosynaptic efficiency of oG-mediated CVS-N2c-ΔG was 2–3 times higher than that of oG-mediated SAD-B19-ΔG;(3)CVS-N2c-ΔG could delivery modified genes for neural activity monitoring,and the time window during which this was maintained was 3 weeks;and(4)CVS-N2c-ΔG could express sufficient recombinases for efficient transgene recombination.These findings demonstrate that new CVS-N2c-ΔG-based toolkit may serve as a versatile tool for structural and functional studies of neural circuits.

Use of a tissue clearing technique combined with retrograde trans-synaptic viral tracing to evaluate changes in mouse retinorecipient brain regions following optic nerve crush

Successful establishment of reconnection between retinal ganglion cells and retinorecipient regions in the brain is critical to optic nerve regeneration.However,morphological assessments of retinorecipient regions are limited by the opacity of brain tissue.In this study,we used an innovative tissue cleaning technique combined with retrograde trans-synaptic viral tracing to observe changes in retinorecipient regions connected to retinal ganglion cells in mice after optic nerve injury.Specifically,we performed light-sheet imaging of whole brain tissue after a clearing process.We found that pseudorabies virus 724(PRV724)mostly infected retinal ganglion cells,and that we could use it to retrogradely trace the retinorecipient regions in whole tissue-cleared brains.Unexpectedly,PRV724-traced neurons were more widely distributed compared with data from previous studies.We found that optic nerve injury could selectively modify projections from retinal ganglion cells in the hypothalamic paraventricular nucleus,intergeniculate leaflet,ventral lateral geniculate nucleus,central amygdala,basolateral amygdala,Edinger-Westphal nucleus,and oculomotor nucleus,but not the superior vestibular nucleus,red nucleus,locus coeruleus,gigantocellular reticular nucleus,or facial nerve nucleus.Our findings demonstrate that the tissue clearing technique,combined with retrograde trans-synaptic viral tracing,can be used to objectively and comprehensively evaluate changes in mouse retinorecipient regions that receive projections from retinal ganglion cells after optic nerve injury.Thus,our approach may be useful for future estimations of optic nerve injury and regeneration.

Distinguishing the main components of submarine groundwater and estimating the corresponding fluxes based on radium tracing method—taking the Maowei Sea for example

Submarine groundwater discharge(SGD)is an important part in the land-sea interactions,which mainly contains three components:submarine fresh groundwater discharge(SFGD),tidal flat recirculated saline groundwater discharge(tidal flat RSGD)and subtidal recirculated saline groundwater discharge(subtidal RSGD).In order to make a more accurate assessment of the impact of SGD on coastal ecological environment,it is necessary to distinguish the main components of SGD.In this study,the Maowei Sea,located in the northern part of the Beibu Gulf,was selected as the study area.Based on the radium(Ra)tracing method,we present a new analytical method for distinguishing the three main components of SGD in this area combined with field data.The average daily flow along the coastline of the Maowei Sea of tidal flat RSGD was slightly higher than that of SFGD,and both two were on the magnitude of 1×10^(5)m^(3)/d.The average daily flow for the subtidal RSGD of the entire subtidal zone of the Maowei Sea reached to the magnitude of 1×10^(6)-1×10^(7)m^(3)/d.The long-term variation trend of terrestrial SGD is a valuable information for the study of the influence of terrigenous material on the coastal ecological environment.Based on the results of four sampling periods,it is found that the fluxes of SFGD and tidal flat RSGD in the Maowei Sea had good linear correlation with the net precipitation.As an example,January 2015 to August 2022 were selected as the study periods,and the variation trends of SFGD and tidal flat RSGD were calculated by linear function with net precipitation as the independent variable.The results showed that the flux of tidal flat RSGD was slightly higher than that of SFGD,and the difference between the two is larger in flood season while smaller in dry season.In general,in the coastal range of China,the total SGD flux in the Maowei Sea area is at a high level,and the SFGD flux is at a medium level.

Graph CA: Learning From Graph Counterfactual Augmentation for Knowledge Tracing

With the popularity of online learning in educational settings, knowledge tracing(KT) plays an increasingly significant role. The task of KT is to help students learn more effectively by predicting their next mastery of knowledge based on their historical exercise sequences. Nowadays, many related works have emerged in this field, such as Bayesian knowledge tracing and deep knowledge tracing methods. Despite the progress that has been made in KT, existing techniques still have the following limitations: 1) Previous studies address KT by only exploring the observational sparsity data distribution, and the counterfactual data distribution has been largely ignored. 2) Current works designed for KT only consider either the entity relationships between questions and concepts, or the relations between two concepts, and none of them investigates the relations among students, questions, and concepts, simultaneously, leading to inaccurate student modeling. To address the above limitations,we propose a graph counterfactual augmentation method for knowledge tracing. Concretely, to consider the multiple relationships among different entities, we first uniform students, questions, and concepts in graphs, and then leverage a heterogeneous graph convolutional network to conduct representation learning.To model the counterfactual world, we conduct counterfactual transformations on students’ learning graphs by changing the corresponding treatments and then exploit the counterfactual outcomes in a contrastive learning framework. We conduct extensive experiments on three real-world datasets, and the experimental results demonstrate the superiority of our proposed Graph CA method compared with several state-of-the-art baselines.

A Novel Contour Tracing Algorithm for Object Shape Reconstruction Using Parametric Curves

Parametric curves such as Bézier and B-splines, originally developedfor the design of automobile bodies, are now also used in image processing andcomputer vision. For example, reconstructing an object shape in an image,including different translations, scales, and orientations, can be performedusing these parametric curves. For this, Bézier and B-spline curves can be generatedusing a point set that belongs to the outer boundary of the object. Theresulting object shape can be used in computer vision fields, such as searchingand segmentation methods and training machine learning algorithms. Theprerequisite for reconstructing the shape with parametric curves is to obtainsequentially the points in the point set. In this study, a novel algorithm hasbeen developed that sequentially obtains the pixel locations constituting theouter boundary of the object. The proposed algorithm, unlike the methods inthe literature, is implemented using a filter containing weights and an outercircle surrounding the object. In a binary format image, the starting point ofthe tracing is determined using the outer circle, and the next tracing movementand the pixel to be labeled as the boundary point is found by the filter weights.Then, control points that define the curve shape are selected by reducing thenumber of sequential points. Thus, the Bézier and B-spline curve equationsdescribing the shape are obtained using these points. In addition, differenttranslations, scales, and rotations of the object shape are easily provided bychanging the positions of the control points. It has also been shown that themissing part of the object can be completed thanks to the parametric curves.

Establishment and Error Analysis of Model of Interference Fringe Contrast for Laser Tracing Measurement Optical System

A method was proposed to analyze the influences of the non-ideal spectroscopic performance of optical components and orientation errors of a laser tracing measurement optical system on the tracing measurement performance.A comprehensive model of the interference fringe contrast based on the laser tracing system s measurement principle was established in this study.Simulation results based on ZEMAX verified the model.According to the simulation results,the placement angle of the analyzer had a direct influence on the interference fringe contrast.When the angle of the polarized light to the analyzer’s transmission axis increased from 65°to 85°,each contrast of the four-way interference fringes decreased from 0.9996 to 0.3528,the interference fringe contrast is decreased by 65%.Under the split ratio of beam splitters in the interference part(BS 1)of 5∶5,when the splitting ratio of BS 2 changed from 2∶8 to 8∶2,the fringe contrast of the interference signals received by the photodetectors increased,but the injection light intensity onto the PSD reflected by BS 2 decreased.The significant influence of the tracing performance was verified by the experiments.When splitting ratio of BS 2 increased,the contrast of the interference fringes increased.Due to the weakening of the incident light intensity of the PSD caused by the change of BS 2 splitting ratio,the response time of the tracing system is increased by 23.7 ms.As a result,the tracing performance of the laser tracing measurement optical system was degraded.An important theoretical basis was provided to evaluate and improve the accuracy and reliability of laser tracing measurement systems.

Point cloud-based environment reconstruction and ray tracing simulations for railway tunnel channels

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.

A minimum traveltime ray tracing global algorithm on a triangular net for propagating plane waves

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.

3D TRACING——和平纪念:第一次世界大战停战百年设计竞赛方案,法国加莱地区

2018年11月11日是第一次世界大战停战100周年纪念日。为此,和平纪念设计竞赛要求参赛者在法国加莱地区自选地段,通过创新设计来纪念一战停战100周年。竞赛任务书指出,一战结束时,面对被摧毁的满目疮痍的城市,影响至今的现代建造方式——预制混凝土技术横空出世;今天,预示未来的3D打印技术在建筑上的应用初现端倪。

An advanced segmentation using area and boundary tracing technique in extraction of lungs region

A new method is presented for the segmentation of pulmonary parenchyma. The proposed method is based on the area calculation of different objects in the image. The main purpose of the proposed algorithm is the segment of the lungs images from the computer tomography(CT) images. The original image is binarized using the bit-plane slicing technique and among the different images the best binarized image is chosen. After binarization, the labeling is done and the area of each label is calculated from which the next level of binarized image is obtained. Then, the boundary tracing algorithm is applied to get another level of binarized image. The proposed method is able to extract lung region from the original images. The experimental results show the significance of the proposed method.

Application of Chemical Tracing Experiment Technique in Leakage Detection of Hydraulic Engineering

[Objective] The research aimed to study the application of chemical tracing experiment technique in leakage detection of hydraulic engineering.[Method] According to the current situation of Sanyuan Western Suburb Reservoir in Xianyang City of Shaanxi Province,three sections （L1,L2 and L3） were set.KI was selected as the chemical tracer to carry out the tracing and detection research.[Result] There was no obvious leakage phenomenon in L1,L2 and L3 sections.The impermeability of rock in some dam abutments was bad.[Conclusion] The leakage reason of Western Suburb Reservoir was that the impermeability of rock in some dam abutments couldn’t satisfy seepage requirement.After the reservoir was put into operation,the water level in front of dam rose,and the ground water level of dam abutment also rose.The penetration water pressure correspondingly increased,and the water content of bank slope at the downstream of dam increased.

Studies on GIS Based Tracing and Traceability of Safe Crop Product in China

The safety of safe crop products （SCP） is critical to maintain people＇s health and living standard. With the global efforts on the improvement of the traceability of food products, it is inevitable to establish corresponding traceability systems to monitor the safety of crop products in China. In this article, the supply chain pattern of SCP in China has been analyzed and its spatial characters have been described in detail. The study deals with on how to relate traceability technology with GIS, and on how to trace and retrace the safety of SCP using the function of excellent spatial representation, spatial locating, and spatial analysis provided in GIS, which has been discussed from several aspects, such as coding technique of traceability information, transferring technique of traceability information, spatialization of traceability information, and application integration of traceability system. A pilot study was carried out to present the basic functions of the system, which provided an efficient and credible way to trace and retrace the safety of SCP in a real supply chain. An innovative idea has been brought forward for how to establish an efficient, credible, applied traceability system of SCP.

Lineage tracing of direct astrocyte-to-neuron conversion in the mouse cortex

Regenerating functional new neurons in the adult mammalian central nervous system has been proven to be very challenging due to the inability of neurons to divide and repopulate themselves after neuronal loss.Glial cells,on the other hand,can divide and repopulate themselves under injury or diseased conditions.We have previously reported that ectopic expression of NeuroD1 in dividing glial cells can directly convert them into neurons.Here,using astrocytic lineage-tracing reporter mice(Aldh1l1-CreERT2 mice crossing with Ai14 mice),we demonstrate that lineage-traced astrocytes can be successfully converted into NeuNpositive neurons after expressing NeuroD1 through adeno-associated viruses.Retroviral expression of NeuroD1 further confirms that dividing glial cells can be converted into neurons.Importantly,we demonstrate that for in vivo cell conversion study,using a safe level of adeno-associated virus dosage(10^10–10^12 gc/mL,1μL)in the rodent brain is critical to avoid artifacts caused by toxic dosage,such as that used in a recent bioRxiv study(2×10^13 gc/mL,1μL,mouse cortex).For therapeutic purpose under injury or diseased conditions,or for non-human primate studies,adeno-associated virus dosage needs to be optimized through a series of dose-finding experiments.Moreover,for future in vivo gliato-neuron conversion studies,we recommend that the adeno-associated virus results are further verified with retroviruses that mainly express transgenes in dividing glial cells in order to draw solid conclusions.The study was approved by the Laboratory Animal Ethics Committee of Jinan University,China(approval No.IACUC-20180330-06)on March 30,2018.

Effects of zinc on cadmium uptake by spring wheat (Triticum aestivum, L.): long-time hydroponic study and short-time ^(109)Cd tracing study

To investigate effects of Zn on Cd uptake by spring wheat (Triticum aestivum, L.) in solution culture, long-time hydroponic experiment (1 month) (Experiment 1) and short-time Cd isotope (109Cd) tracing experiment (24 h) (Experiment 2) were conducted. In Experiment 1, spring wheat (cv. Brookton) was grown in nutrient solution at uniform cadmium concentration of 20μ mol/L and 10 zinc concentrations (0, 1, 5, 10, 20, 100, 200, 500, 1000, 2000 μ mol/L). In Experiment 2, spring wheat seedlings,pre-cultivated in complete nutrient solution, were treated with 109Cd of uniform activity and the same series of Zn concentrations as those in Experiment 1 for 24 h. Cd concentrations in shoots and roots in Experiment 1 increased marginally but not consistently with Zn increasing at Zn rates of 1～200 μmol/L, and then decreased significantly at high rates (＞200 μ mol/L). In Experiment 2, the response of 109Cd activities in shoots and roots to increasing Zn was greatly similar to the response of Cd concentrations to Zn increasing in Experiment 1. The results of the two experiments indicated that the short-time and long-time exposure of spring wheat to Zn had similar effects on Cd accumulation.

Tracing the provenance of aeolian loess in the Yangtze River Delta through zircon U–Pb age and geochemical investigations

Given the conflicts over the proposed formation mechanisms of Xiashu loess, the question of the provenance of sediments comprising the Xiashu loess in the Yangtze River Delta has not been satisfactorily resolved. In this study, the provenance of aeolian sediments of the Yangtze River Delta, China was examined by applying the detrial zircon U–Pb dating technique, Sr–Nd isotopic and trace element compositional analysis. U-Pb dating analysis was conducted on the Xiashu loess at three locations over the Yangtze River Delta, including Huangnishan(HNS) hill, Shengshan(SS) island and the Xuancheng(XC) area. The Xiashu loess and the sediments of the Yangtze River Valley share considerable similarity in their zircon U-Pb age spectra with the same main age peak and comparable age distribution. By contrast, significant differences in the age spectra, existbetween the Xiashu loess and loess deposits of Chinese Loess Plateau(CLP). Coarse grains of the Yangtze River Delta loess may have a proximal material source identical to the sediments from the Yangtze River valley. Sr–Nd isotopic values of the Xiashu loess match those from the northern margin of the Tibetan Plateau. Rare earth element ratios independent of grain size illustrate that the values from loess of the Yangtze River Delta mostly overlap with those of CLP loess. This feature implies that loess from the Yangtze River Delta has a dominant source of distant material similar as the CLP loess. As such, we conclude that multi-proxy analysis of sediments can shed new light on tracing the provenance of aeolian loess in the Yangtze River Delta.

Target-oriented Gaussian beam migration using a modif ied ray tracing scheme

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.

An improved ion-exchange/diffusion method for ～(15)N isotope tracing analysis of nitrate in surface waters from watersheds

An improved method,suitable for collecting nitrate from surface waters in the watershed for 15 N isotope tracing analysis,was developed on the basis of the anion exchange coupled with diffusion through systematic simulation and comparison experiments.The results showed that the nitrate could be separated and enriched from the waters efficiently by using the improved method.Being simple and practical in operation principle and procedures,cost-economic,and highly efficient in nitrate separation/enrichment,the method met the requirements of δ 15 N mass spectrum analysis and would lay a foundation for the application of 15 N isotope tracing approach to the research on non-point source pollution in watershed.

Marine Mobile Wireless Channel Modeling Based on Improved Spatial Partitioning Ray Tracing

In 5G era,it is expected to achieve wireless network coverage including offshore areas.Modeling of marine wireless channels is the basis of constructing a marine communication system.In this paper,a communication scene between an unmanned aerial vehicle(UAV)and a boat is simulated to study the marine wireless channel.Firstly,an improved spatial partitioning ray tracing algorithm is proposed to track the propagation path of electromagnetic waves at sea surface.Secondly,a mobile channel is simulated and modeled based on the track results.Finally,a loss measurement is carried out in the coastal waters based on the simple wireless channel loss measuring platform,and a path loss propagation model is built.Then we compare the actual measurement data with the simulation results and find that the two are have good consistency,which further verifies the reliability of the simulation.

Biotinylated dextran amine anterograde tracing of the canine corticospinal tract

In this study, biotinylated dextran amine （BDA） was microinjected into the left cortical motor area of the canine brain. Fluorescence microscopy results showed that a large amount of BDA-labeled pyramidal cells were visible in the left cortical motor area after injection. In the left medulla oblongata, the BDA-labeled corticospinal tract was evenly distributed, with green fluorescence that had a clear boundary with the surrounding tissue. The BDA-positive corticospinal tract entered into the right lateral funiculus of the spinal cord and descended into the posterior part of the right lateral funiculus, close to the posterior horn, from cervical to sacral segments. There was a small amount of green fluorescence in the sacral segment. The distribution of BDA labeling in the canine central nervous system was consistent with the course of the corticospinal tract. Fluorescence labeling for BDA gradually diminished with time after injection. Our findings indicate that the BDA anterograde tracing technique can be used to visualize the localization and trajectory of the corticospinal tract in the canine central nervous system.