Primary Rays Research Articles

Monte Carlo raytracing method for calculating secondary electron emission from micro-architected surfaces

Secondary electron emission (SEE) from inner linings of plasma chambers in electric thrusters for space propulsion can have a disruptive effect on device performance and efficiency. SEE is typically calculated using elastic and inelastic electron scattering theory by way of Monte Carlo simulations of independent electron trajectories. However, in practice the method can only be applied for ideally smooth surfaces and thin films, not representative of real material surfaces. Recently, micro-architected surfaces with micron-sized features have been proposed to mitigate SEE and ion-induced erosion in plasma-exposed thruster linings. In this paper, we propose an approach for calculating secondary electron yields from surfaces with arbitrarily-complex geometries using an extension of the ray tracing Monte Carlo (RTMC) technique. We study microfoam structures with varying porosities as representative micro-architected surfaces, and use RTMC to generate primary electron trajectories and track secondary electrons until their escape from the outer surface. Actual surfaces are represented as a discrete finite element meshes obtained from X-ray tomography images of tungsten microfoams. At the local level, primary rays impinging into surface elements produce daughter rays of secondary electrons whose number, energies and angular characteristics are set by pre-calculated tables of SEE yields and energies from ideally-flat surfaces. We find that these micro-architected geometries can reduce SEE by up to 50% with respect to flat surfaces depending on porosity and primary electron energy.

Hierarchical Visibility for Virtual Reality

We introduce a novel primary visibility algorithm based on ray casting that provides real time performance and a feature set well suited for rendering virtual reality. The flexibility provided by our approach allows for a variety of features such as lens distortion, sub-pixel rendering, very wide field of view, foveation and stochastic depth of field blur to be implemented and composed naturally while maintaining real time performance. In contrast, the current rasterization pipelines implemented in hardware require multiple passes and/or post processing to approximate these features and current highly optimized ray tracers, which primarily focus on Monte Carlo path tracing, do not achieve real time performance on current VR displays (1080x1200x2@90hz). Our approach uses a bounding volume hierarchy acceleration and a two level frustum culling/entry point search algorithm to optimize the traversal of coherent primary visibility rays. We introduce an adaptation of MSAA for raycasting that significantly lowers memory bandwidth, we leverage an AVX optimized CPU traversal to perform the majority of culling and an optimized CUDA GPU implementation for triangle intersection, multi-sample antialiasing, and shading. The implementation provides support for animation and physically-based shading and lighting. We believe this approach presents a concrete, viable alternative to rasterization that is significantly better suited to rendering for virtual and augmented reality. In order to engage the community, we have released our implementation under an open-source license.

A pipeline-based heterogeneous framework for efficient synthetic light field rendering

The research interest of real-time global illumination has increased due to the growing demand of graphics applications such as virtual reality. Recently, the design that combines Image-Based Rendering (IBR) and Ray-Tracing to create Synthetic Light Field (SLF) has been widely adopted to provide delicate visual experience for multiple viewpoints at an acceptable frame rate. However, despite its parallel characteristic, constructing a SLF is still inefficient on modern Graphics Processing Unit (GPU) due to the irregularities. For instance, the issues caused by branch divergence, early-termination and irregular memory access prolong the execution time that cannot be simply resolved by workload merging. In this paper, we proposed a Runtime framework that reorganizes the execution into a pipeline-based pattern with grouping of primary rays. The workloads are later distributed to all heterogeneous cores to increase the efficiency of the execution. With this approach, the number of valid rays can be maintained at a high level with less divergence of paths. Based on the experiment on a heterogeneous system, the maximum throughput for a single GPU becomes 3.12 times higher than the original on average and becomes even higher on systems with multiple heterogeneous cores.

A New Species of Simulium (Asiosimulium) (Diptera: Simuliidae) from Thailand.

Simulium (Asiosimulium) saeungae sp. nov. (Diptera: Simuliidae) is described based on females, males, pupae, and mature larvae collected from Nan Province, Northern Thailand. It is characterized by the medium-long cerci in the female, enlarged hind basitarsus, and broad ventral plate with its posterior margin not deeply concave in the male, arborescent pupal gill with 42-56 filaments in the pupa and smaller number of primary rays of the labral fan (30-33) in the larva. This is the fifth species of the subgenus Asiosimulium, the second smallest among 10 subgenera in the Oriental Region. Taxonomic notes are given to distinguish this new species from the three known species from Thailand and one from Nepal.

Measurement of antiproton production in p–He collisions at LHCb to constrain the secondary cosmic antiproton flux

The flux of cosmic ray antiprotons is a powerful tool for indirect detection of dark matter. The sensitivity is limited by the uncertainty on the predicted antiproton flux from scattering of primary rays on the interstellar medium. This is, in turn, limited by the knowledge of production cross‐sections, notably in p–He scattering. Thanks to its internal gas target, the LHCb experiment performed the first measurement of antiproton production from collisions of LHC proton beams on He nuclei at rest. The results and prospects are presented.

Time Interval Ray Tracing for Motion Blur.

We introduce a new motion blur computation method for ray tracing that provides an analytical approximation of motion blurred visibility per ray. Rather than relying on timestamped rays and Monte Carlo sampling to resolve the motion blur, we associate a time interval with rays and directly evaluate when and where each ray intersects with animated object faces. Based on our simplifications, the volume swept by each animated face is represented using a triangulation of the surface of this volume. Thus, we can resolve motion blur through ray intersections with stationary triangles, and we can use any standard ray tracing acceleration structure without modifications to account for the time dimension. Rays are intersected with these triangles to analytically determine the time interval and positions of the intersections with the moving objects. Furthermore, we explain an adaptive strategy to efficiently shade the intersection intervals. As a result, we can produce noise-free motion blur for both primary and secondary rays. We also provide a general framework for emulating various camera shutter mechanisms and an artistic modification that amplifies the visibility of moving objects for emphasizing the motion in videos or static images.

Fuzzy Mutual Information-Based Intraslice Grouped Ray Casting

Abstract The traditional ray casting algorithm has the capability to render three-dimensional volume data in the viewable two-dimensional form by sampling the color data along the rays. The speed of the technique relies on the computation incurred by the huge volume of rays. The objective of the paper is to reduce the computations made over the rays by eventually reducing the number of samples being processed throughout the volume data. The proposed algorithm incorporates the grouping strategy based on fuzzy mutual information (FMI) over a group of voxels in the conventional ray casting to achieve the reduction. For the data group, with FMI in a desirable range, a single primary ray is cast into the group as a whole. As data are grouped before casting rays, the proposed algorithm reduces the interpolation calculation and thereby runs with lesser complexity, preserving the image quality.

MergeTree

Ray tracing is a computationally intensive rendering technique traditionally used in offline high-quality rendering. Powerful hardware accelerators have been recently developed that put real-time ray tracing even in the reach of mobile devices. However, rendering animated scenes remains difficult, as updating the acceleration trees for each frame is a memory-intensive process. This article proposes MergeTree, the first hardware architecture for Hierarchical Linear Bounding Volume Hierarchy (HLBVH) construction, designed to minimize memory traffic. For evaluation, the hardware constructor is synthesized on a 28nm process technology. Compared to a state-of-the-art binned surface area heuristic sweep (SAH) builder, the present work speeds up construction by a factor of 5, reduces build energy by a factor of 3.2, and memory traffic by a factor of 3. A software HLBVH builder on a graphics processing unit (GPU) requires 3.3 times more memory traffic. To take tree quality into account, a rendering accelerator is modeled alongside the builder. Given the use of a toplevel build to improve tree quality, the proposed builder reduces system energy per frame by an average 41% with primary rays and 13% with diffuse rays. In large ( > 500K triangles) scenes, the difference is more pronounced, 62% and 35%, respectively.

Distinctive wood anatomy of the root-parasitic family Lennoaceae (Boraginales)

The four species of Lennoaceae have strands of primary plus secondary xylem in a background of starch-rich parenchyma. These strands constitute a cylinder with large primary rays. The wood within these strands is markedly different from that of other families in the crown group of Boraginales such as Cordiaceae and Ehretiaceae, most of which are woody. Lennoaceae differ because they lack fibrous cells (libriform fibers), lack rays within the vascular strands, and have markedly elliptical vessel-to-vessel pits without vestures. Lennoaceae have secondary xylem with short, wide vessel elements with thick walls, horizontally elongate elliptical pits, simple perforation plates much narrower than the vessel lumen; variously uneven vessel wall thickenings; and axial parenchyma. The wood of Lennoaceae shows resemblances to unrelated succulents such as Kalanchoe (Crassulaceae) and Lithops (Aizoaceae). The vessel features also suggest adaptation to high water tensions as root parasites in desert areas, whereas the lack of imperforate tracheary elements may relate to support of the underground stem portions by sand or rock detritus. Habit and ecology are more important in the architecture of lennoaceous xylem than systematic affinities. The four species of Lennoaceae differ from each other in minor xylary features.

Construction of bounding volume hierarchies with SAH cost approximation on temporary subtrees

Advances in research on quality metrics for bounding volume hierarchies (BVHs) have shown that greedy top-down SAH builders construct BVHs with superior traversal performance despite the fact that the resulting SAH values are higher than those created by more sophisticated builders. Motivated by this observation we examine three construction algorithms that use recursive SAH values of temporarily constructed SAH-built BVHs to guide the construction and perform an extensive evaluation. The resulting BVHs achieve up to 37% better trace performance for primary rays and up to 32% better trace performance for secondary diffuse rays compared to standard plane sweeping without applying spatial splits. Allowing spatial splits still achieves up to 18% resp.15% better performance. While our approach is not suitable for real-time BVH construction, we show that the proposed algorithm has subquadratic computational complexity in the number of primitives, which renders it usable in practical applications. Additionally, we describe an approach for improving the forecasting abilities of the SAH-EPO ray tracing performance predictor which also increases its relevance for primary rays.

Stray light in cone beam optical computed tomography: II. Reduction using a convergent light source

Optical cone beam computed tomography (CBCT) using a broad beam and CCD camera is a fast method for densitometry of 3D optical gel dosimeters. However, diffuse light sources introduce considerable stray light into the imaging system, leading to underestimation of attenuation coefficients and non-uniformities in CT images unless corrections are applied to each projection image. In this study, the light source of a commercial optical CT scanner is replaced with a convergent cone beam source consisting of almost exclusively image forming primary rays. The convergent source is achieved using a small isotropic source and a Fresnel lens. To characterize stray light effects, full-field cone beam CT imaging is compared to fan beam CT (FBCT) using a 1 cm high fan beam aperture centered on the optic axis of the system. Attenuating liquids are scanned within a large 96 mm diameter uniform phantom and in a small 13.5 mm diameter finger phantom. For the uniform phantom, cone and fan beam CT attenuation coefficients agree within a maximum deviation of (1 ± 2)% between mean values over a wide range from 0.036 to 0.43 cm−1. For the finger phantom, agreement is found with a maximum deviation of (4 ± 2)% between mean values over a range of 0.1–0.47 cm−1. With the convergent source, artifacts associated with refractive index mismatch and vessel optical features are more pronounced. Further optimization of the source size to achieve a balance between quantitative accuracy and artifact reduction should enable practical, accurate 3D dosimetry, avoiding time consuming 3D scatter measurements.

МОРФОЛОГО-АНАТОМІЧНЕ ДОСЛІДЖЕННЯ БЕДРИНЦЮ ЛОМИКАМЕНЕВОГО (PIMPINELLA SAXIFRAGA L.)

<p><strong>MORPHOLOGICAL AND ANATOMICAL RESEARCH </strong></p><p><strong>OF </strong><strong>P</strong><strong>IMPINELLA SAXIFRAGA</strong><strong> L.</strong><strong></strong></p><p><strong>S.M.Marchyshyn, T.M. Hontova, E.A. Panasiuk</strong></p><p> </p><p>“I.Ya.HorbachevskyTernopilStateMedicalUniversityof the Ministry of Health ofUkraine” higher educational establishment</p><p>NationalPharmaceuticalUniversity</p><p><strong>Summary.</strong> The morphological and anatomical research of the herb and rhizome of pimpinella saxifrage l. has been made. Basic macro- and microscopic have been established to identify the raw material.</p><p><strong>Key words: </strong>pimpinella saxifrage l., herb, rhizome, macro- and microscopic features.</p><p><strong>Introduction. </strong>Pimpinella saxifraga L. Is a perennial herbaceous glabrous or puberulent plant of the Apiaceae family. It grows scattered on slopes, grass hills, forest glades, among the shrubs and along the roads on the entireterritory ofUkraine. For a long time pimpinella saxifrage l. has been used in folk medicine as an anti-spastic, ant-inflammatory, uretic, expectorant, anti-tussic, photosensitizing drug. The plant inUkraine is considered as non-officinal.</p><p><strong>The purpose</strong> of the research is to make a macro- and microscopic analysis of the herb and rhizome of pimpinella saxifrage l.</p><p><strong>Methods of the research. </strong>The micro-preparations were made of freshly collected raw material in the mixture of 96% ethanol – glycerol – purified water (1:1:1). The diagnostic microscopic features were studied by means of the microscope “Granum” with magnification power of x40, x100, x400. The photographs were taken with a camera Sony DSC-W80.</p><p><strong>Findings of the research. </strong>The macroscopic features of the rhizome of pimpinella saxifrage l. Spindle-shaped, longitudinally-wrinkled rhizomes up to5 cm in length and 2 –5 mm. in thickness. Grey-brown in colour, with uneven bend, yellowish-brown in colour, with yellow-brown spots. Strong, fragrant and acrid odour. Strong, bittersweet flavor.</p><p><strong>Microscopic features of the rhizome. </strong>The rhizome is covered with a thick layer of periderm. The cortical parenchyma is composed of parenchymal cells, small cells (phloem elements) are located lower. The phloem spreads evenly, in wide primary rays. The upper part of the cortical parenchyma contains oblong air vessels. The cortical parenchyma may have small schizogenous spaces; the parenchyma cells surrounding them contain starch. The central cylinder is clearly separated by the layer of cambium. The vessels are lined in oblong chains. The wood parenchyma accumulates starch. The rhizome center has a distinct lacune. </p><p><strong>Microscopic features of the herb. </strong>The stalks are thin-ribbed, branched and puberulent. The leaves are pinnated and macropodous; the margin is <a href="http://www.multitran.ru/c/m.exe?t=3157693_1_2&s1=%EF%E8%EB%FC%F7%E0%F2%EE-%E7%F3%E1%F7%E0%F2%FB%E9">serrate-dentate</a>. The flowers are small, pentapetalous and in compound umbel inflorescence. The fruit are small, egg-shaped mericarps. The blade is green on the upper part and light green on the lower part; the flowers are white. The odour is faint and pleasant. The flavor is spicy and bitterish.</p><p><strong>Microscopic analysis if herb. </strong>The stalk is multi-ribbed. The stalk epiderm is small-celled; the cellular membrane has straight and slightly thickened walls. The stomata are oval, large and rare. The stomatal mechanism is anomocytic and anysocytic. The epiderm is unevenly puberulent. The trichomes are long, bent and many-celled, with a small basilar cell and oblong main cells, cone-shaped, 2-celled, long 3-celled straight, erect with oblong apical cell.</p><p>The leaf is dorsiventral. Palisade mesophile, bilarious, cancellate mesophile – tetrastichous. The cells of the palisade mesophile are small, not distinct, cylinder-shaped or oval; the second-row cells of the inner layer are loose. The cells of the cancellate mesophile are small, round or horizontally oblong. The stomata on the lower epiderm are protruding. The upper epiderm is represented by the parenchymal cells of various shape – starting with multi-angled ones and finishing with isodiametric-shaped ones. The cells of the lower epiderm are parenchymal, thin-walled and with rather sinuated membranes. The stomata are multiple, they are large and oval. The stomatal mechanism is anomocytic and paracytic. The leaf is unevenly puberulent. There are more trichomes on the lower side.</p><p><strong>Conclusions. </strong>The morphological and anatomical features of pimpinella saxifrage l. have been studied, and the main macro- and microscopic diagnostic features of rhizome, stalks, flowers and leaves have been defined to be later used for standardization of the medical raw material and design of the project “Pimpinella herb” and “Pimpinella rhizome”.</p>

Noise suppression and multiple attenuation using full-azimuth angle domain imaging: case studies

The EarthStudy 360 Imager is an advanced depth imaging system that first maps the full recorded seismic data into the subsurface grid points and then decomposes the data into local angle domain (LAD) bins. It is based on specially designed diffraction operators using bottom-up ray tracing. In this article, we focus on the ability of the EarthStudy 360 Imager to attenuate different types of wave characteristics considered as both random and coherent noise – in particular, different orders of multiples, and non-reflection seismic events such as Rayleigh, refraction, diffraction and ‘side’ waves. The method is based on internal implementation of local slant stack (LSS) operators optimally designed for each primary ray pair associated with a given source-image point-receiver path and the corresponding seismic data event. The LSS is applied in the direction of the horizontal slowness components of the arriving rays at the acquisition surface, where the size of the LSS (the number of traces involved) is computed independently for each ray pair from its first Fresnel zone. Thus, primary reflection events sharing the same traveltime and the same surface directivity as the traced ray pairs are emphasized (highly weighted), while all other events (considered as noise) are simultaneously attenuated. We demonstrate our method in four different land data examples with different levels of geological complexities.

Descriptions and comparison of two species closely resembling Simulium (Simulium) including a new species with an updated key to Korean Simuliidae (Diptera)

AbstractImmature stages of Simulium (Simulium) coreanum sp. nov. and morphologically similar Simulium (Simulium) nikkoense are described from Korea. Detailed descriptions are supplemented with photographs and habitat information. The new species can be distinguished from the latter by rectal papillae with 3 simple lobes and labral fan with 51–58 primary rays. Keys to larvae and pupae of all known Korean simuliid species are also provided.

Trimeridianellidae nov. fam., a Triassic spumellarian radiolarian family with simple initial skeleton and pyloniacean mode of growth

Based on several samples of Middle and Late Triassic age, the authors describe a new family of spumellarian Radiolaria – Trimeridianellidae Dumitrica and Tekin, characterized by a three-fold symmetry, a first shell of triangular prism type with 6 primary rays originated at the edges of two bases of the prism, or 3 meridian arches with 3 equatorial rays, and growth of pyloniacean type. The family comprises 4 monospecific new genera (Enneacladus Dumitrica, Endoprisma Dumitrica, Trimeridianella Dumitrica and Tekin, and Tristylopyle Dumitrica), 4 new species and one left in open nomenclature. In spite of their spotty occurrences and low diversity, the authors attempt to trace the evolution of the family, which is considered to be the result of heterochrony in ontogenetic growth, mostly of paedomorphic type. The family seems to be related to the Middle Triassic family Patruliidae Dumitrica with which it shares in common the simple microsphere with 6 primary rays and the pyloniacean mode of growth.

Using Monte Carlo Method For Simulation Of Electromagnetic Radiation Penetration In Bodys Tissues

According to the physical nature of the penetration of electromagnetic radiation, in different body's tissues, this process can be simulated with using Monte-Carlo (based on random number generation) methods. In this study penetration of ray in the muscle and bony tissues is simulated. With using Fortran90 code, the penetration of electromagnetic ray in the cube target was simulated. The curve of ray penetration in the muscle and bony tissues, for different ray energies (40, 60, 200, 500 KeV) is obtained. So change the output ray intensity is calculated per number of different primary rays. This calculation compared with experimental calculations in water, with comparing the results of code, that written by authors and experimental results, the results show good agreement with each other.

Observation of changes of cambial domain patterns on the basis of primary ray development in Fagus silvatica L.

The high multiseriate primary rays that occur in young stems of <i>Fagus silvatica</i> L. undergo splitting during cambium development. Segments of the split primary rays remain close to each other and form characteristic strands. Within these strands, sections can be observed in which the rays are split in the same direction, either in configuration Z or S. The configuration of other cambial cellular events neighboring the primary rays under consideration is in agreement with the configuration of the splitting of these rays. The arrangement of the rays on the surface of the wood after debarking a young stem makes it possible to decipher the domain pattern on a surface of any given size. As the stem segment ages, the borders between domains migrate and new borders are formed, changing their course from longitudinal to transverse.

Comparative Analysis of the Morphometric Changes in Ussurian bullhead, Leiocassis ussuriensis, and Korean bullhead, Pseudobagrus fulvidraco, in the Early Period of Growth.

Morphometric changes in the Ussurian bullhead, Leiocassis ussuriensis, and the Korean bullhead, Pseudobagrus fulvidraco, were observed during the early period of growth. Yolk length, yolk height, and yolk volume in the two species decreased within 9 days post-hatching (DPH) (p<0.05). The body lengths and body heights of both species increased gradually to 150 and 130 DPH, respectively (p<0.05). The horizontal distance between the anteriormost extension of the head and the anterior insertion of the pectoral fin, the anteriormost extension of the head × the verticality position of the anterior insertion of the primary dorsal fin rays, and the anterior insertion of the primary dorsal fin × the anterior insertion of the pectoral fin were greater in the Korean bullhead than in the Ussurian bullhead (p<0.05). However, the relative sizes of the head region, pectoral fin, ventral fin, and anal fin were greater in the Ussurian bullhead than in the Korean bullhead (p<0.05), and relative body depth and the size of the outer-mandible barbel were greater in the Korean bullhead than in the Ussurian bullhead (p<0.05). The growth curves of the morphometric characteristics of both species were divided into three types.

High resolution sparse voxel DAGs

We show that a binary voxel grid can be represented orders of magnitude more efficiently than using a sparse voxel octree (SVO) by generalising the tree to a directed acyclic graph (DAG). While the SVO allows for efficient encoding of empty regions of space, the DAG additionally allows for efficient encoding of identical regions of space, as nodes are allowed to share pointers to identical subtrees. We present an efficient bottom-up algorithm that reduces an SVO to a minimal DAG, which can be applied even in cases where the complete SVO would not fit in memory. In all tested scenes, even the highly irregular ones, the number of nodes is reduced by one to three orders of magnitude. While the DAG requires more pointers per node, the memory cost for these is quickly amortized and the memory consumption of the DAG is considerably smaller, even when compared to an ideal SVO without pointers. Meanwhile, our sparse voxel DAG requires no decompression and can be traversed very efficiently. We demonstrate this by ray tracing hard and soft shadows, ambient occlusion, and primary rays in extremely high resolution DAGs at speeds that are on par with, or even faster than, state-of-the-art voxel and triangle GPU ray tracing.

Visibility-driven progressive volume photon tracing

In this paper, we present a novel approach to progressive photon-based volume rendering techniques. By making use of two Kd-trees (built in a preprocessing step) to store view beams (primary rays intersecting the medium) and visible points, our method allows to handle scenes with specular and refractive objects as well as homogeneous and heterogeneous participating media and does not require the storage of photon maps, which solves the memory management issue. These data structures are used to drive the photon shooting process by considering the photon visibility as an importance function (similarly to Hachisuka and Jensen in ACM Trans. Graph. 30(5):114:1---114:11, 2011) for scenes containing participating media. Finally, we demonstrate that our method can be easily combined with the most recent particle tracing approaches such as the one presented in Jarosz et al. (ACM Trans. Graph., vol. 30(6), 2011).