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Sample records for adaptive ray tracing

  1. Adaptive sample map for Monte Carlo ray tracing

    NASA Astrophysics Data System (ADS)

    Teng, Jun; Luo, Lixin; Chen, Zhibo

    2010-07-01

    Monte Carlo ray tracing algorithm is widely used by production quality renderers to generate synthesized images in films and TV programs. Noise artifact exists in synthetic images generated by Monte Carlo ray tracing methods. In this paper, a novel noise artifact detection and noise level representation method is proposed. We first apply discrete wavelet transform (DWT) on a synthetic image; the high frequency sub-bands of the DWT result encode the noise information. The sub-bands coefficients are then combined to generate a noise level description of the synthetic image, which is called noise map in the paper. This noise map is then subdivided into blocks for robust noise level metric calculation. Increasing the samples per pixel in Monte Carlo ray tracer can reduce the noise of a synthetic image to visually unnoticeable level. A noise-to-sample number mapping algorithm is thus performed on each block of the noise map, higher noise value is mapped to larger sample number, and lower noise value is mapped to smaller sample number, the result of mapping is called sample map. Each pixel in a sample map can be used by Monte Carlo ray tracer to reduce the noise level in the corresponding block of pixels in a synthetic image. However, this block based scheme produces blocky artifact as appeared in video and image compression algorithms. We use Gaussian filter to smooth the sample map, the result is adaptive sample map (ASP). ASP serves two purposes in rendering process; its statistics information can be used as noise level metric in synthetic image, and it can also be used by a Monte Carlo ray tracer to refine the synthetic image adaptively in order to reduce the noise to unnoticeable level but with less rendering time than the brute force method.

  2. Laser ray tracing in a parallel arbitrary Lagrangian-Eulerian adaptive mesh refinement hydrocode

    NASA Astrophysics Data System (ADS)

    Masters, N. D.; Kaiser, T. B.; Anderson, R. W.; Eder, D. C.; Fisher, A. C.; Koniges, A. E.

    2010-08-01

    ALE-AMR is a new hydrocode that we are developing as a predictive modeling tool for debris and shrapnel formation in high-energy laser experiments. In this paper we present our approach to implementing laser ray tracing in ALE-AMR. We present the basic concepts of laser ray tracing and our approach to efficiently traverse the adaptive mesh hierarchy.

  3. High performance dosimetry calculations using adapted ray-tracing

    NASA Astrophysics Data System (ADS)

    Perrotte, Lancelot; Saupin, Guillaume

    2010-11-01

    When preparing interventions on nuclear sites, it is interesting to study different scenarios, to identify the most appropriate one for the operator(s). Using virtual reality tools is a good way to simulate the potential scenarios. Thus, taking advantage of very efficient computation times can help the user studying different complex scenarios, by immediately evaluating the impact of any changes. In the field of radiation protection, people often use computation codes based on the straight line attenuation method with build-up factors. As for other approaches, geometrical computations (finding all the interactions between radiation rays and the scene objects) remain the bottleneck of the simulation. We present in this paper several optimizations used to speed up these geometrical computations, using innovative GPU ray-tracing algorithms. For instance, we manage to compute every intersectionbetween 600 000 rays and a huge 3D industrial scene in a fraction of second. Moreover, our algorithm works the same way for both static and dynamic scenes, allowing easier study of complex intervention scenarios (where everything moves: the operator(s), the shielding objects, the radiation sources).

  4. ENZO+MORAY: radiation hydrodynamics adaptive mesh refinement simulations with adaptive ray tracing

    NASA Astrophysics Data System (ADS)

    Wise, John H.; Abel, Tom

    2011-07-01

    We describe a photon-conserving radiative transfer algorithm, using a spatially-adaptive ray-tracing scheme, and its parallel implementation into the adaptive mesh refinement cosmological hydrodynamics code ENZO. By coupling the solver with the energy equation and non-equilibrium chemistry network, our radiation hydrodynamics framework can be utilized to study a broad range of astrophysical problems, such as stellar and black hole feedback. Inaccuracies can arise from large time-steps and poor sampling; therefore, we devised an adaptive time-stepping scheme and a fast approximation of the optically-thin radiation field with multiple sources. We test the method with several radiative transfer and radiation hydrodynamics tests that are given in Iliev et al. We further test our method with more dynamical situations, for example, the propagation of an ionization front through a Rayleigh-Taylor instability, time-varying luminosities and collimated radiation. The test suite also includes an expanding H II region in a magnetized medium, utilizing the newly implemented magnetohydrodynamics module in ENZO. This method linearly scales with the number of point sources and number of grid cells. Our implementation is scalable to 512 processors on distributed memory machines and can include the radiation pressure and secondary ionizations from X-ray radiation. It is included in the newest public release of ENZO.

  5. Laser Ray Tracing in a Parallel Arbitrary Lagrangian-Eulerian Adaptive Mesh Refinement Hydrocode

    SciTech Connect

    Masters, N D; Kaiser, T B; Anderson, R W; Eder, D C; Fisher, A C; Koniges, A E

    2009-09-28

    ALE-AMR is a new hydrocode that we are developing as a predictive modeling tool for debris and shrapnel formation in high-energy laser experiments. In this paper we present our approach to implementing laser ray-tracing in ALE-AMR. We present the equations of laser ray tracing, our approach to efficient traversal of the adaptive mesh hierarchy in which we propagate computational rays through a virtual composite mesh consisting of the finest resolution representation of the modeled space, and anticipate simulations that will be compared to experiments for code validation.

  6. Thin Lens Ray Tracing.

    ERIC Educational Resources Information Center

    Gatland, Ian R.

    2002-01-01

    Proposes a ray tracing approach to thin lens analysis based on a vector form of Snell's law for paraxial rays as an alternative to the usual approach in introductory physics courses. The ray tracing approach accommodates skew rays and thus provides a complete analysis. (Author/KHR)

  7. Computer ray tracing speeds.

    PubMed

    Robb, P; Pawlowski, B

    1990-05-01

    The results of measuring the ray trace speed and compilation speed of thirty-nine computers in fifty-seven configurations, ranging from personal computers to super computers, are described. A correlation of ray trace speed has been made with the LINPACK benchmark which allows the ray trace speed to be estimated using LINPACK performance data. The results indicate that the latest generation of workstations, using CPUs based on RISC (Reduced Instruction Set Computer) technology, are as fast or faster than mainframe computers in compute-bound situations. PMID:20563112

  8. Anisotropic ray trace

    NASA Astrophysics Data System (ADS)

    Lam, Wai Sze Tiffany

    Optical components made of anisotropic materials, such as crystal polarizers and crystal waveplates, are widely used in many complex optical system, such as display systems, microlithography, biomedical imaging and many other optical systems, and induce more complex aberrations than optical components made of isotropic materials. The goal of this dissertation is to accurately simulate the performance of optical systems with anisotropic materials using polarization ray trace. This work extends the polarization ray tracing calculus to incorporate ray tracing through anisotropic materials, including uniaxial, biaxial and optically active materials. The 3D polarization ray tracing calculus is an invaluable tool for analyzing polarization properties of an optical system. The 3x3 polarization ray tracing P matrix developed for anisotropic ray trace assists tracking the 3D polarization transformations along a ray path with series of surfaces in an optical system. To better represent the anisotropic light-matter interactions, the definition of the P matrix is generalized to incorporate not only the polarization change at a refraction/reflection interface, but also the induced optical phase accumulation as light propagates through the anisotropic medium. This enables realistic modeling of crystalline polarization elements, such as crystal waveplates and crystal polarizers. The wavefront and polarization aberrations of these anisotropic components are more complex than those of isotropic optical components and can be evaluated from the resultant P matrix for each eigen-wavefront as well as for the overall image. One incident ray refracting or reflecting into an anisotropic medium produces two eigenpolarizations or eigenmodes propagating in different directions. The associated ray parameters of these modes necessary for the anisotropic ray trace are described in Chapter 2. The algorithms to calculate the P matrix from these ray parameters are described in Chapter 3 for

  9. Ray Tracing with Virtual Objects.

    ERIC Educational Resources Information Center

    Leinoff, Stuart

    1991-01-01

    Introduces the method of ray tracing to analyze the refraction or reflection of real or virtual images from multiple optical devices. Discusses ray-tracing techniques for locating images using convex and concave lenses or mirrors. (MDH)

  10. Ray Tracing in the Classroom.

    ERIC Educational Resources Information Center

    Majewski, Mirek

    1997-01-01

    Ray tracing is a method that allows the creation of photo-realistic images on a computer. This article describes a shareware ray tracing program called PovRay and includes some ideas on how PovRay can be used in teaching and in 3-D geometry, physics, and other high school and university subjects. (Author/AIM)

  11. Linearized ray-trace analysis

    NASA Technical Reports Server (NTRS)

    Redding, David C.; Breckenridge, William G.

    1990-01-01

    A new, coordinate-free version of the exact ray-trace equations for optical systems consisting of conic reflecting, refracting and reference surfaces is presented. These equations are differentiated to obtain closed-form optical sensitivity dyadics. For computation, the sensitivities are evaluated in a single global coordinate frame and combined in linearized ray-trace matrix difference equations that propagate the rays and the sensitivities from element to element. One purpose of this analysis is to create optical models that can be directly integrated with models of the instrument structure and control systems for dynamic simulation.

  12. Real ray tracing in anisotropic viscoelastic media

    NASA Astrophysics Data System (ADS)

    Vavryčuk, Václav

    2008-11-01

    Ray tracing equations applicable to smoothly inhomogeneous anisotropic viscoelastic media are derived. The equations produce real rays, in contrast to previous ray-theoretical approaches, which deal with complex rays. The real rays are defined as the solutions of the Hamilton equations, with the Hamiltonian modified for viscoelastic media, and physically correspond to trajectories of high-frequency waves characterized by a real stationary phase. As a consequence, the complex eikonal equation is satisfied only approximately. The ray tracing equations are valid for weakly and moderately attenuating media. The rays are frequency-dependent and must be calculated for each frequency, separately. Solving the ray tracing equations in viscoelastic anisotropy is more time consuming than in elastic anisotropy. The main difficulty is with determining the stationary slowness vector, which is generally complex-valued and inhomogeneous and must be computed at each time step of the ray tracing procedure. In viscoelastic isotropy, the ray tracing equations considerably simplify, because the stationary slowness vector is homogeneous. The computational time for tracing rays in isotropic elastic and viscoelastic media is the same. Using numerical examples, it is shown that ray fields in weakly attenuating media (Q higher than about 30) are almost indistinguishable from those in elastic media. For moderately attenuating anisotropic media (Q between 5-20), the differences in ray fields can be visible and significant.

  13. Reverse ray tracing for transformation optics.

    PubMed

    Hu, Chia-Yu; Lin, Chun-Hung

    2015-06-29

    Ray tracing is an important technique for predicting optical system performance. In the field of transformation optics, the Hamiltonian equations of motion for ray tracing are well known. The numerical solutions to the Hamiltonian equations of motion are affected by the complexities of the inhomogeneous and anisotropic indices of the optical device. Based on our knowledge, no previous work has been conducted on ray tracing for transformation optics with extreme inhomogeneity and anisotropicity. In this study, we present the use of 3D reverse ray tracing in transformation optics. The reverse ray tracing is derived from Fermat's principle based on a sweeping method instead of finding the full solution to ordinary differential equations. The sweeping method is employed to obtain the eikonal function. The wave vectors are then obtained from the gradient of that eikonal function map in the transformed space to acquire the illuminance. Because only the rays in the points of interest have to be traced, the reverse ray tracing provides an efficient approach to investigate the illuminance of a system. This approach is useful in any form of transformation optics where the material property tensor is a symmetric positive definite matrix. The performance and analysis of three transformation optics with inhomogeneous and anisotropic indices are explored. The ray trajectories and illuminances in these demonstration cases are successfully solved by the proposed reverse ray tracing method. PMID:26191770

  14. Validation of Ray Tracing Code Refraction Effects

    NASA Technical Reports Server (NTRS)

    Heath, Stephanie L.; McAninch, Gerry L.; Smith, Charles D.; Conner, David A.

    2008-01-01

    NASA's current predictive capabilities using the ray tracing program (RTP) are validated using helicopter noise data taken at Eglin Air Force Base in 2007. By including refractive propagation effects due to wind and temperature, the ray tracing code is able to explain large variations in the data observed during the flight test.

  15. A fast and efficient adaptive parallel ray tracing based model for thermally coupled surface radiation in casting and heat treatment processes

    NASA Astrophysics Data System (ADS)

    Fainberg, J.; Schaefer, W.

    2015-06-01

    A new algorithm for heat exchange between thermally coupled diffusely radiating interfaces is presented, which can be applied for closed and half open transparent radiating cavities. Interfaces between opaque and transparent materials are automatically detected and subdivided into elementary radiation surfaces named tiles. Contrary to the classical view factor method, the fixed unit sphere area subdivision oriented along the normal tile direction is projected onto the surrounding radiation mesh and not vice versa. Then, the total incident radiating flux of the receiver is approximated as a direct sum of radiation intensities of representative “senders” with the same weight factor. A hierarchical scheme for the space angle subdivision is selected in order to minimize the total memory and the computational demands during thermal calculations. Direct visibility is tested by means of a voxel-based ray tracing method accelerated by means of the anisotropic Chebyshev distance method, which reuses the computational grid as a Chebyshev one. The ray tracing algorithm is fully parallelized using MPI and takes advantage of the balanced distribution of all available tiles among all CPU's. This approach allows tracing of each particular ray without any communication. The algorithm has been implemented in a commercial casting process simulation software. The accuracy and computational performance of the new radiation model for heat treatment, investment and ingot casting applications is illustrated using industrial examples.

  16. Symplectic ray-tracing: a new approach for nonlinear ray tracings by Hamiltonian dynamics

    NASA Astrophysics Data System (ADS)

    Satoh, Tetsu R.

    2003-05-01

    This paper describes a method of symplectic ray tracing for calculating the flows of non-linear dynamical systems. Symplectic ray tracing method traces the path of photons moving along the orbit calculated by using Hamilton's canonical equation. Using this method, we can simulate non-linear dynamical systems with various dimensions, accurate calculation, and quick implementation of scientif visualization system. This paper also demonstrates some visualization results of non-linear dynamical systems computed by using symplectic ray tracing method.

  17. Improved backward ray tracing with stochastic sampling

    NASA Astrophysics Data System (ADS)

    Ryu, Seung Taek; Yoon, Kyung-Hyun

    1999-03-01

    This paper presents a new technique that enhances the diffuse interreflection with the concepts of backward ray tracing. In this research, we have modeled the diffuse rays with the following conditions. First, as the reflection from the diffuse surfaces occurs in all directions, it is impossible to trace all of the reflected rays. We confined the diffuse rays by sampling the spherical angle out of the reflected rays around the normal vector. Second, the traveled distance of reflected energy from the diffuse surface differs according to the object's property, and has a comparatively short reflection distance. Considering the fact that the rays created on the diffuse surfaces affect relatively small area, it is very inefficient to trace all of the sampled diffused rays. Therefore, we set a fixed distance as the critical distance and all the rays beyond this distance are ignored. The result of this research is that as the improved backward ray tracing can model the illumination effects such as the color bleeding effects, we can replace the radiosity algorithm under the limited environment.

  18. Tracing the X-Ray Trail

    MedlinePlus

    What you need to know about… Tracing the X-ray Trail If you’ve just completed an x-ray, computed tomography (CT), magnetic resonance (MR) Start here! or other diagnostic imaging procedure, you probably want to know when you will ... los rayos X Si acaba de hacerse una radiografía, tomografía ¡Empezar ...

  19. Birefringent Polarization Ray Tracing: Theory and Applications

    NASA Astrophysics Data System (ADS)

    McClain, Stephen Charles

    Birefringent polarization ray tracing is an extension of geometric ray tracing. In addition to calculating ray paths and phases, it also analyzes the state of polarization through birefringent devices. Some systems containing birefringent elements include optical computers, radiometers, optical isolators, bar code scanners, and optical data storage systems. This dissertation derives explicit algorithms for polarization ray tracing through anisotropic media, optically active media, and anisotropic optically active media, such as quartz. The objective was to go beyond the electromagnetic relations to establish algorithms in standard ray tracing format, ready for direct inclusion into lens design software. The algorithms, derived from Maxwell's equations, constitutive relations, and boundary conditions, calculate the wavevector, ray vector, optical path length, refractive index, and polarization state of a ray. Generalized Fresnel relations govern the division of energy at each interface into two transmitted and two reflected modes. The algorithms are applied to calculate the polarization aberrations of a variety of birefringent devices. In particular, it is established that the polarization properties of quartz vary significantly (>20%) over angles of only 5 degrees. This limits the useful field of view of quartz devices. Field of view aberrations of birefringent elements can critically affect the performance of optical systems. Also, design guidelines are presented for pseudodepolarizers. These devices spatially scramble the polarization. Inserted into an instrument, a depolarizer negates the polarization sensitivity of the elements which follow it. Presented in detail is the design and analysis of a depolarizer for use in a spectrometer on NASA's Earth Observing System (EOS).

  20. Birefringent polarization ray tracing: Theory and applications

    NASA Astrophysics Data System (ADS)

    McClain, Stephen Charles

    1992-06-01

    Birefringent polarization ray tracing is an extension of geometric ray tracing. In addition to calculating ray paths and phases, it also analyzes the state of polarization through birefringent devices. Some systems containing birefringent elements include optical computers, radiometers, optical isolators, bar code scanners, and optical data storage systems. This dissertation derives explicit algorithms for polarization ray tracing through anisotropic media, optically active media, and anisotropic optically active media, such as quartz. The objective was to go beyond the electromagnetic relations to establish algorithms in standard ray tracing format, ready for direct inclusion into lens design software. The algorithms, derived from Maxwell's equations, constitutive relations, and boundary conditions, calculate the wavevector, ray vector, optical path length, refractive index, and polarization state of a ray. Generalized Fresnel relations govern the division of energy at each interface into two transmitted and two reflected modes. The algorithms are applied to calculate the polarization aberrations of a variety of birefringent devices. In particular, it is established that the polarization properties of quartz vary significantly (greater than 20 percent) over angles of only 5 degrees. This limits the useful field of view of quartz devices. Field of view aberrations of birefringent elements can critically affect the performance of optical systems. Also, design guidelines are presented for pseudodepolarizers. These devices spatially scramble the polarization. Inserted into an instrument, a depolarizer negates the polarization sensitivity of the elements which follow it. Presented in detail is the design and analysis of a depolarizer for use in a spectrometer on NASA's Earth Observing System (EOS).

  1. AXAF FITS standard for ray trace interchange

    NASA Astrophysics Data System (ADS)

    Hsieh, Paul F.

    1993-07-01

    A standard data format for the archival and transport of x-ray events generated by ray trace models is described. Upon review and acceptance by the Advanced X-ray Astrophysics Facility (AXAF) Software Systems Working Group (SSWG), this standard shall become the official AXAF data format for ray trace events. The Flexible Image Transport System (FITS) is well suited for the purposes of the standard and was selected to be the basis of the standard. FITS is both flexible and efficient and is also widely used within the astronomical community for storage and transfer of data. In addition, software to read and write FITS format files are widely available. In selecting quantities to be included within the ray trace standard, the AXAF Mission Support team, Science Instruments team, and the other contractor teams were surveyed. From the results of this survey, the following requirements were established: (1) for the scientific needs, each photon should have associated with it: position, direction, energy, and statistical weight; the standard must also accommodate path length (relative phase), and polarization. (2) a unique photon identifier is necessary for bookkeeping purposes; (3) a log of individuals, organizations, and software packages that have modified the data must be maintained in order to create an audit trail; (4) a mechanism for extensions to the basic kernel should be provided; and (5) the ray trace standard should integrate with future AXAF data product standards.

  2. AXAF FITS standard for ray trace interchange

    NASA Technical Reports Server (NTRS)

    Hsieh, Paul F.

    1993-01-01

    A standard data format for the archival and transport of x-ray events generated by ray trace models is described. Upon review and acceptance by the Advanced X-ray Astrophysics Facility (AXAF) Software Systems Working Group (SSWG), this standard shall become the official AXAF data format for ray trace events. The Flexible Image Transport System (FITS) is well suited for the purposes of the standard and was selected to be the basis of the standard. FITS is both flexible and efficient and is also widely used within the astronomical community for storage and transfer of data. In addition, software to read and write FITS format files are widely available. In selecting quantities to be included within the ray trace standard, the AXAF Mission Support team, Science Instruments team, and the other contractor teams were surveyed. From the results of this survey, the following requirements were established: (1) for the scientific needs, each photon should have associated with it: position, direction, energy, and statistical weight; the standard must also accommodate path length (relative phase), and polarization. (2) a unique photon identifier is necessary for bookkeeping purposes; (3) a log of individuals, organizations, and software packages that have modified the data must be maintained in order to create an audit trail; (4) a mechanism for extensions to the basic kernel should be provided; and (5) the ray trace standard should integrate with future AXAF data product standards.

  3. Ray tracing through progressive ophthalmic lenses

    NASA Astrophysics Data System (ADS)

    Bourdoncle, Bernard; Chauveau, J. P.; Mercier, Jean-Louis M.

    1991-01-01

    Ray-tracing through Progressive Addition Lenses (PAL) has been performed. PAL is a deep non rotationally symmetric asp1ric lens used for the compensation of presbyopia. PAL and its mathematical model are presented. The special features of the ray-tracing program due to the model of the lens plus eye system are detailed. Typical results are presented showing in particular that computing conditions of contour-plots of power and astigmatism must be very strict and that coma must be taken into account for precise measurements of PAL. 1.

  4. Ray tracing on a networked processor array

    NASA Astrophysics Data System (ADS)

    Yang, Jungsook; Lee, Seung Eun; Chen, Chunyi; Bagherzadeh, Nader

    2010-10-01

    As computation costs increase to meet design requirements for computation-intensive graphics applications on today's embedded systems, the pressure to develop high-performance parallel processors on a chip will increase. Acceleration of the ray tracing computation has become a major issue as the computer graphics industry demands for rendering realistic images. Network-on-chip (NoC) techniques that interconnect multiple processing elements with routers are the solution for reducing computation time and power consumption by parallel processing on a chip. It is also essential to meet the scalability and complexity challenges for system-on-chip (SoC). In this article, we describe a parallel ray tracing application mapping on a mesh-based multicore NoC architecture. We describe an optimised ray tracing kernel and parallelisation strategies, varying the workload distribution statically and dynamically. In this work, we present results and timing performance of our parallel ray tracing application on a NoC, which are obtained through our cycle accurate multicore NoC simulator. Using a dynamic scheduling load balancing technique, we achieved a maximum speedup multiplier of 35.97 on an 8 × 8 networked processor array using a NoC as the interconnect.

  5. Tracing Rays In Laser-Fringe Anemometers

    NASA Technical Reports Server (NTRS)

    Owen, Karl

    1989-01-01

    "OPTMAIN" is simple ray-tracing computer code developed to quantify refractive effects that result when laser-fringe anemometer used to observe flows through window. Code calculates changes for four different types of windows: flat-plate windows, simple cylindrical windows, "general" axisymmetric windows, and smooth general-surface windows. Written in FORTRAN IV.

  6. Ray Traces Through Unsteady Jet Turbulence

    NASA Technical Reports Server (NTRS)

    Freund, J. B.; Fleischman, T. G.

    2002-01-01

    Results of an ongoing effort to quantify the role turbulence in scattering sound in jets are reported. Using a direct numerical simulation database to provide the flow data, ray paths traced through the mean flow are compared with those traced through the actual time evolving turbulent flow. Significant scattering by the turbulence is observed. The most notable effect is that upstream traveling waves that are trapped in the potential core by the mean flow, which acts as a wave guide, easily escape in the turbulent flow. A crude statistical estimate based on ray number density suggests that directivity is modified by the turbulence, but no rigorous treatment of non-uniformities in the high-frequency approximation is attempted.

  7. Testing the ray-tracing code GYOTO

    NASA Astrophysics Data System (ADS)

    Grould, M.; Paumard, T.; Perrin, G.

    2015-12-01

    In the next few years, the near-infrared interferometer GRAVITY will observe the Galactic Center. Astrometric data will be obtained with an expected accuracy of 10 μas. In order to analyze those future data, we have developed a code named GYOTO to compute orbits and ray-trace images. We want to assess the validity and accuracy of GYOTO in a variety of contexts, in particular for stellar astrometry in the Galactic Center.

  8. Special relativistic visualization by local ray tracing.

    PubMed

    Müller, Thomas; Grottel, Sebastian; Weiskopf, Daniel

    2010-01-01

    Special relativistic visualization offers the possibility of experiencing the optical effects of traveling near the speed of light, including apparent geometric distortions as well as Doppler and searchlight effects. Early high-quality computer graphics images of relativistic scenes were created using offline, computationally expensive CPU-side 4D ray tracing. Alternate approaches such as image-based rendering and polygon-distortion methods are able to achieve interactivity, but exhibit inferior visual quality due to sampling artifacts. In this paper, we introduce a hybrid rendering technique based on polygon distortion and local ray tracing that facilitates interactive high-quality visualization of multiple objects moving at relativistic speeds in arbitrary directions. The method starts by calculating tight image-space footprints for the apparent triangles of the 3D scene objects. The final image is generated using a single image-space ray tracing step incorporating Doppler and searchlight effects. Our implementation uses GPU shader programming and hardware texture filtering to achieve high rendering speed. PMID:20975164

  9. Nonlinear ray tracing for vessel enhanced visualization

    NASA Astrophysics Data System (ADS)

    Qiu, Feng; Hong, Wei

    2012-02-01

    3D visualization of angiography data is an important preprocessing step in diagnosis of vascular disease. This paper describes an efficient volume rendering method to emphasize feature-rich region (or focus) in the 3D angiography data. The method takes the input 3D angiography data and computes the focus with user specification or certain feature extraction algorithms. Then, a distance map is constructed based on the description of the focused region(s). While rendering the 3D angiography data, the nonlinear ray tracing method is used and the gradient of the distance volume is applied to guide ray marching. In the result image, the focused region(s) appears larger than in the normal ray-casting image, while the context (other regions of the volume) can be still preserved in the image (maybe displayed in a shrink size). This method avoids deforming the original volume to magnify focus regions, which is expensive to compute, thus improves the performance.

  10. Magnetospheric ray tracing studies. [Jupiter's decametric radiation

    NASA Technical Reports Server (NTRS)

    Six, N. F.

    1982-01-01

    Using a model of Jupiter's magnetized plasma environment, radiation raypaths were calculated with a three-dimension ray tracing program. It is assumed that energetic particles produce the emission in the planet's auroral zone at frequencies just above the electron gyrofrequencies. This radiation is generated in narrow sheets defined by the angle of a ray with respect to the magnetic field line. By specifying the source position: latitude, longitude, and radial distance from the planet, signatures in the spectrum of frequency versus time seen by Voyager 1 and 2 were duplicated. The frequency range and the curvature of the decametric arcs in these dynamic spectra are the result of the geometry of the radiation sheets (imposed by the plasma and by the B-field) and illumination of Voyager 1 and 2 as the rotating magnetosphere mimics a pulsar.

  11. Ray Tracing for Complex Astrophysical High-opacity Structures

    NASA Astrophysics Data System (ADS)

    Steinacker, J.; Bacmann, A.; Henning, T.

    2006-07-01

    We present a ray-tracing technique for radiative transfer modeling of complex three-dimensional (3D) structures that include dense regions of high optical depth, such as that in dense molecular clouds, circumstellar disks, envelopes of evolved stars, and dust tori around active galactic nuclei. The corresponding continuum radiative transfer problem is described, and the numerical requirements for inverse 3D density and temperature modeling are defined. We introduce a relative intensity and transform the radiative transfer equation along the rays to solve machine precision problems and to relax strong gradients in the source term. For the optically thick regions where common ray tracers are forced to perform small trace steps, we give two criteria for making use of a simple approximative solver crossing the optically thick region quickly. Using an example of a density structure with optical depth changes of 6 orders of magnitude and sharp temperature variations, we demonstrate the accuracy of the proposed scheme using a common fifth-order Runge-Kutta ray tracer with adaptive step-size control. In our test case, the gain in computational speed is about a factor of 870. The method is applied in order to calculate the temperature distribution within a massive molecular cloud core for different boundary conditions for the radiation field.

  12. Application of ray tracing in radiation heat transfer

    NASA Technical Reports Server (NTRS)

    Baumeister, Joseph F.

    1993-01-01

    This collection of presentation figures displays the capabilities of ray tracing for radiation propagation calculations as compared to an analytical approach. The goal is to introduce the terminology and solution process used in ray tracing, and provide insight into radiation heat transfer principles and analysis tools. A thermal analysis working environment is introduced that solves demanding radiation heat transfer problems based on ray tracing. This information may serve as a reference for designing and building ones own analysis environment.

  13. Powerful scriptable ray tracing package xrt

    NASA Astrophysics Data System (ADS)

    Klementiev, Konstantin; Chernikov, Roman

    2014-09-01

    We present an open source python based ray tracing tool that offers several useful features in graphical presentation, material properties, advanced calculations of synchrotron sources, implementation of diffractive and refractive elements, complex (also closed) surfaces and multiprocessing. The package has many usage examples which are supplied together with the code and visualized on its web page. We exemplify the present version by modeling (i) a curved crystal analyzer, (ii) a quarter wave plate, (iii) Bragg-Fresnel optics and (iv) multiple reflective and non-sequential optics (polycapillary). The present version implements the use of OpenCL framework that executes calculations on both CPUs and GPUs. Currently, the calculations of an undulator source on a GPU show a gain of about two orders of magnitude in computing time. The development version is successful in modelling the wavefront propagation. Two examples of diffraction on a plane mirror and a plane blazed grating are given for a beam with a finite energy band.

  14. Ray tracing in nuclear-pumped flowing gas lasers

    SciTech Connect

    Mat'ev, V Yu

    2003-06-30

    The ray tracing in the resonators of a nuclear-pumped flowing gas lasers is considered. The refractive index profile of the medium in a direction perpendicular to the optical axis in such lasers can be considered parabolic, but the steepness of the parabola is quite nonuniform along the ray trace, and the resonator stability condition (the absolute value of the ray matrix trace for a single trip of the ray in the resonator is smaller than two) is not sufficient to confine the ray within the resonator after a large number of trips. (lasers)

  15. Seismic ray tracing using linear traveltime interpolation

    SciTech Connect

    Asakawa, Eiichi; Kawanaka, Taku )

    1993-01-01

    A new ray-tracing method called linear traveltime interpolation (LTI) is proposed. This method computes traveltimes and raypaths in a 2D velocity structure more rapidly and accurately than other conventional methods. The LTI method is formulated for a 2D cell model, and calculations of traveltimes and raypaths are carried out only on cell boundaries. Therefore a raypath is considered to be always straight in a cell with uniform velocity. This approach is suitable to tomography analysis. The algorithm of LTI consists of two separate steps: step 1 calculates traveltimes on all cell boundaries; step 2 traces raypaths for all pairs of receivers and the shot. A traveltime at an arbitrary point on a cell boundary is assumed to be linearly interpolated between traveltimes at the adjacent discrete points at which traveltimes were calculated. Fermat's principle is used as the criterion for choosing the correct traveltimes and raypaths from several candidates routinely. The LTI method has been compared numerically with the shooting method and the finite-difference method (FDM) of the eikonal equation. The results show that the LTI method has great advantages of high speed and high accuracy in the calculation of both traveltimes and raypaths. The LTI method can be regarded as an advanced version of the conventional FDM of the eikonal equation because the formulae of FDM are independently derived from LTI. In the process of derivation, it is shown theoretically that LTI is more accurate than FDM. Moreover in the LTI method, they can avoid the numerical instability that occurs in Vidale's method where the velocity changes abruptly.

  16. Tracing Lifestyle Adaptation in Prokaryotic Genomes

    PubMed Central

    Altermann, Eric

    2012-01-01

    Lifestyle adaptation of microbes due to changes in their ecological niches or acquisition of new environments is a major driving force for genetic changes in their respective genomes. Moving into more specialized niches often results in the acquisition of new gene sets via horizontal gene transfer to utilize previously unavailable metabolites, while genetic ballast is shed by gene loss and/or gene inactivation. In some cases, larger genome rearrangements can be observed, such as the incorporation of whole genetic islands, providing a range of new phenotypic capabilities. Until recently these changes could not be comprehensively followed and identified due to the lack of complete microbial genome sequences. The advent of high-throughput DNA sequencing has dramatically changed the scientific landscape and today microbial genomes have become increasingly abundant. Currently, more than 2,900 genomes are published and more than 11,000 genome projects are listed in the Genomes Online Database‡. Although this wealth of information provides many new opportunities to assess microbial functionality, it also creates a new array of challenges when a comparison between multiple microbial genomes is required. Here, functional genome distribution (FGD) is introduced, analyzing the diversity between microbes based on their predicted ORFeome. FGD is therefore a comparative genomics approach, emphasizing the assessments of gene complements. To further facilitate the comparison between two or more genomes, degrees of amino-acid similarities between ORFeomes can be visualized in the Artemis comparison tool, graphically depicting small and large scale genome rearrangements, insertion and deletion events, and levels of similarity between individual open reading frames. FGD provides a new tool for comparative microbial genomics and the interpretation of differences in the genetic makeup of bacteria. PMID:22363326

  17. Tracing lifestyle adaptation in prokaryotic genomes.

    PubMed

    Altermann, Eric

    2012-01-01

    Lifestyle adaptation of microbes due to changes in their ecological niches or acquisition of new environments is a major driving force for genetic changes in their respective genomes. Moving into more specialized niches often results in the acquisition of new gene sets via horizontal gene transfer to utilize previously unavailable metabolites, while genetic ballast is shed by gene loss and/or gene inactivation. In some cases, larger genome rearrangements can be observed, such as the incorporation of whole genetic islands, providing a range of new phenotypic capabilities. Until recently these changes could not be comprehensively followed and identified due to the lack of complete microbial genome sequences. The advent of high-throughput DNA sequencing has dramatically changed the scientific landscape and today microbial genomes have become increasingly abundant. Currently, more than 2,900 genomes are published and more than 11,000 genome projects are listed in the Genomes Online Database. Although this wealth of information provides many new opportunities to assess microbial functionality, it also creates a new array of challenges when a comparison between multiple microbial genomes is required. Here, functional genome distribution (FGD) is introduced, analyzing the diversity between microbes based on their predicted ORFeome. FGD is therefore a comparative genomics approach, emphasizing the assessments of gene complements. To further facilitate the comparison between two or more genomes, degrees of amino-acid similarities between ORFeomes can be visualized in the Artemis comparison tool, graphically depicting small and large scale genome rearrangements, insertion and deletion events, and levels of similarity between individual open reading frames. FGD provides a new tool for comparative microbial genomics and the interpretation of differences in the genetic makeup of bacteria. PMID:22363326

  18. Some extensions of the Booker method of ray tracing

    NASA Astrophysics Data System (ADS)

    Budden, K. G.

    1989-10-01

    The Booker method of ray tracing is useful for tracing the paths of radio rays in a plane stratified magneto-plasma, and a brief summary is given. In its simplest form it is used for tracing a single ray, without taking account of the configuration of neighboring rays. Two extensions of the method are discussed. The first is the effect on the signal amplitude of the divergence or convergence of neighboring rays in a thin ray pencil. The second is the technique of complex rays and complex space, which are especially useful when electron collisions introduce attenuation of the waves. Some typical results for both extensions are presented. This paper is mainly a tutorial paper, but some new results are given, including a method for dealing with a singularity in the equations for the ray divergence effect.

  19. The vectorization of a ray tracing program for image generation

    NASA Technical Reports Server (NTRS)

    Plunkett, D. J.; Cychosz, J. M.; Bailey, M. J.

    1984-01-01

    Ray tracing is a widely used method for producing realistic computer generated images. Ray tracing involves firing an imaginary ray from a view point, through a point on an image plane, into a three dimensional scene. The intersections of the ray with the objects in the scene determines what is visible at the point on the image plane. This process must be repeated many times, once for each point (commonly called a pixel) in the image plane. A typical image contains more than a million pixels making this process computationally expensive. A traditional ray tracing program processes one ray at a time. In such a serial approach, as much as ninety percent of the execution time is spent computing the intersection of a ray with the surface in the scene. With the CYBER 205, many rays can be intersected with all the bodies im the scene with a single series of vector operations. Vectorization of this intersection process results in large decreases in computation time. The CADLAB's interest in ray tracing stems from the need to produce realistic images of mechanical parts. A high quality image of a part during the design process can increase the productivity of the designer by helping him visualize the results of his work. To be useful in the design process, these images must be produced in a reasonable amount of time. This discussion will explain how the ray tracing process was vectorized and gives examples of the images obtained.

  20. ROBAST: ROOT-based ray-tracing library for cosmic-ray telescopes

    NASA Astrophysics Data System (ADS)

    Okumura, Akira

    2016-03-01

    ROBAST (ROOT-based simulator for ray tracing) is a non-sequential ray-tracing simulation library developed for wide use in optical simulations of gamma-ray and cosmic-ray telescopes. The library is written in C++ and fully utilizes the geometry library of the ROOT analysis framework, and can build the complex optics geometries typically used in cosmic ray experiments and ground-based gamma-ray telescopes.

  1. Light ray tracing through a leaf cross section

    NASA Technical Reports Server (NTRS)

    Kumar, R.; Silva, L. F.

    1973-01-01

    A light ray, incident at about 5 deg to the normal, is geometrically plotted through the drawing of the cross section of a soybean leaf using Fresnel's equations and Snell's law. The optical mediums of the leaf considered for ray tracing are: air, cell sap, chloroplast, and cell wall. The ray is also drawn through the same leaf cross section with cell wall and air as the only optical mediums. The values of the reflection and transmission found from the ray tracing tests agree closely with the experimental results obtained using a Beckman Dk-2A Spectroreflector.

  2. Light ray tracing through a leaf cross section

    NASA Technical Reports Server (NTRS)

    Kumar, R.; Silva, L.

    1973-01-01

    A light ray, incident at about 5 deg to the normal, is geometrically plotted through the drawing of the cross section of a soybean leaf using Fresnel's equations and Snell's law. The optical mediums of the leaf considered for ray tracing are air, cell sap, chloroplast, and cell wall. The above ray is also drawn through the same leaf cross section considering cell wall and air as the only optical mediums. The values of the reflection and transmission found from ray tracing agree closely with the experimental results obtained using a Beckman DK-2A spectroreflectometer.

  3. Polarization ray tracing in anisotropic optically active media

    NASA Technical Reports Server (NTRS)

    Mcclain, Stephen C.; Chipman, Russell A.

    1992-01-01

    Procedures for performing polarization ray tracing through birefringent media are presented in a form compatible with the standard methods of geometric ray tracing. The birefringent materials treated include the following: anisotropic optically active materials such as quartz, non-optically active uniaxial materials such as calcite, and isotropic optically active materials such as mercury sulfide or organic liquids. Refraction and reflection algorithms are presented which compute both ray directions and wave directions. Methods for computing polarization modes, refractive indices, optical path lengths, and Fresnel transmission and reflection coefficients are also specified.

  4. Toward Adaptive X-Ray Telescopes

    NASA Technical Reports Server (NTRS)

    O'Dell, Stephen L.; Atkins, Carolyn; Button, Tim W.; Cotroneo, Vincenzo; Davis, William N.; Doel, Peer; Feldman, Charlotte H.; Freeman, Mark D.; Gubarev, Mikhail V.; Kolodziejczak, Jeffrey J.; Michette, Alan G.; Ramsey, Brian D.; Reid, Paul B.; Rodriguez Sanmartin, Daniel; Saha, Timo T.; Schwartz, Daniel A.; Trolier-McKinstry, Susan; Wilke, Rudeger H. T.; Willingale, Richard; Zhang, William W.

    2011-01-01

    Future x-ray observatories will require high-resolution (less than 1 inch) optics with very-large-aperture (greater than 25 square meter) areas. Even with the next generation of heavy-lift launch vehicles, launch-mass constraints and aperture-area requirements will limit the surface areal density of the grazing-incidence mirrors to about 1 kilogram per square meter or less. Achieving sub-arcsecond x-ray imaging with such lightweight mirrors will require excellent mirror surfaces, precise and stable alignment, and exceptional stiffness or deformation compensation. Attaining and maintaining alignment and figure control will likely involve adaptive (in-space adjustable) x-ray optics. In contrast with infrared and visible astronomy, adaptive optics for x-ray astronomy is in its infancy. In the middle of the past decade, two efforts began to advance technologies for adaptive x-ray telescopes: The Generation-X (Gen-X) concept studies in the United States, and the Smart X-ray Optics (SXO) Basic Technology project in the United Kingdom. This paper discusses relevant technological issues and summarizes progress toward adaptive x-ray telescopes.

  5. Differential ray tracing analysis of the Schwarzschild objective

    NASA Astrophysics Data System (ADS)

    Prieto-Blanco, Xesús; Mouriz, Dolores; González Núñez, Héctor; Lopez Lago, Elena; de la Fuente, Raúl

    2011-05-01

    Differential Ray Tracing (DRT) is applied to optimize the design of a Schwarzschild objective with large aperture and for arbitrary object position. This optical system lacks of cylindrical symmetry about the non-paraxial base ray, causing astigmatism of a pencil of rays around this ray. The analysis determines the mirror radii ratio that makes the pencil anastigmatic, leading to an excellent image performance. In particular, the classical aplanatic Schwarzschild design is obtained in the limiting case where the base ray becomes paraxial. One example of a design, similar to a typical commercial objective for microscopy, is presented and the image quality is analyzed with an optical design program.

  6. On a combined adaptive tetrahedral tracing and edge diffraction model

    NASA Astrophysics Data System (ADS)

    Hart, Carl R.

    A major challenge in architectural acoustics is the unification of diffraction models and geometric acoustics. For example, geometric acoustics is insufficient to quantify the scattering characteristics of acoustic diffusors. Typically the time-independent boundary element method (BEM) is the method of choice. In contrast, time-domain computations are of interest for characterizing both the spatial and temporal scattering characteristics of acoustic diffusors. Hence, a method is sought that predicts acoustic scattering in the time-domain. A prediction method, which combines an advanced image source method and an edge diffraction model, is investigated for the prediction of time-domain scattering. Adaptive tetrahedral tracing is an advanced image source method that generates image sources through an adaptive process. Propagating tetrahedral beams adapt to ensonified geometry mapping the geometric sound field in space and along boundaries. The edge diffraction model interfaces with the adaptive tetrahedral tracing process by the transfer of edge geometry and visibility information. Scattering is quantified as the contribution of secondary sources along a single or multiple interacting edges. Accounting for a finite number of diffraction permutations approximates the scattered sound field. Superposition of the geometric and scattered sound fields results in a synthesized impulse response between a source and a receiver. Evaluation of the prediction technique involves numerical verification and numerical validation. Numerical verification is based upon a comparison with analytic and numerical (BEM) solutions for scattering geometries. Good agreement is shown for the selected scattering geometries. Numerical validation is based upon experimentally determined scattered impulse responses of acoustic diffusors. Experimental data suggests that the predictive model is appropriate for high-frequency predictions. For the experimental determination of the scattered impulse

  7. Numerical Ray-Tracing in Full Angle Spatial Compounding

    NASA Astrophysics Data System (ADS)

    Koch, Andreas; Koch, Ingo; Hansen, Christian; Lerch, Reinhard; Ermert, Helmut

    The assumption of straight-line wave propagation is common in medical ultrasound. While sufficient for unidirectional systems, it is the main cause for degenerated FASC (Full Angle Spatial Compounding) images, where B-mode data from different viewing angles around an object, e.g. the female breast, are superimposed. To overcome this, we have implemented an eikonal equation based algorithm to perform numerical ray-tracing in inhomogeneous speed of sound distributions. Results can be used to correct ray-paths prior to FASC. Our goal was to improve FASC image quality by using numerical ray-tracing. A tissue mimicking phantom with reservoirs filled with different concentrations of saline water and correspondingly different speeds of sound was imaged with a 2.5 MHz transducer. To evaluate the isotropy of the system's spatial resolution, seven fibers were included into the phantom and the reservoirs. We compared the full width at half maximum of line scatterer images in a FASC image corrected by ray-paths from the numerical ray-tracing with an uncorrected FASC image. Results show that numerical ray-tracing improves the image contrast, eliminates double line artifacts and improves the resolution and its isotropy in FASC.

  8. Studying the precision of ray tracing techniques with Szekeres models

    NASA Astrophysics Data System (ADS)

    Koksbang, S. M.; Hannestad, S.

    2015-07-01

    The simplest standard ray tracing scheme employing the Born and Limber approximations and neglecting lens-lens coupling is used for computing the convergence along individual rays in mock N-body data based on Szekeres swiss cheese and onion models. The results are compared with the exact convergence computed using the exact Szekeres metric combined with the Sachs formalism. A comparison is also made with an extension of the simple ray tracing scheme which includes the Doppler convergence. The exact convergence is reproduced very precisely as the sum of the gravitational and Doppler convergences along rays in Lemaitre-Tolman-Bondi swiss cheese and single void models. This is not the case when the swiss cheese models are based on nonsymmetric Szekeres models. For such models, there is a significant deviation between the exact and ray traced paths and hence also the corresponding convergences. There is also a clear deviation between the exact and ray tracing results obtained when studying both nonsymmetric and spherically symmetric Szekeres onion models.

  9. Ray-tracing-based reconstruction algorithms for digital breast tomosynthesis

    NASA Astrophysics Data System (ADS)

    Zhou, Weihua; Lu, Jianping; Zhou, Otto; Chen, Ying

    2015-03-01

    As a breast-imaging technique, digital breast tomosynthesis has great potential to improve the diagnosis of early breast cancer over mammography. Ray-tracing-based reconstruction algorithms, such as ray-tracing back projection, maximum-likelihood expectation maximization (MLEM), ordered-subset MLEM (OS-MLEM), and simultaneous algebraic reconstruction technique (SART), have been developed as reconstruction methods for different breast tomosynthesis systems. This paper provides a comparative study to investigate these algorithms by computer simulation and phantom study. Experimental results suggested that, among the four investigated reconstruction algorithms, OS-MLEM and SART performed better in interplane artifact removal with a fast speed convergence.

  10. Ray tracing a three dimensional scene using a grid

    DOEpatents

    Wald, Ingo; Ize, Santiago; Parker, Steven G; Knoll, Aaron

    2013-02-26

    Ray tracing a three-dimensional scene using a grid. One example embodiment is a method for ray tracing a three-dimensional scene using a grid. In this example method, the three-dimensional scene is made up of objects that are spatially partitioned into a plurality of cells that make up the grid. The method includes a first act of computing a bounding frustum of a packet of rays, and a second act of traversing the grid slice by slice along a major traversal axis. Each slice traversal includes a first act of determining one or more cells in the slice that are overlapped by the frustum and a second act of testing the rays in the packet for intersection with any objects at least partially bounded by the one or more cells overlapped by the frustum.

  11. Efficient ray tracing algorithms based on wavefront construction and model based interpolation method

    NASA Astrophysics Data System (ADS)

    Lee, Kyoung Jin

    Understanding and modeling seismic wave propagation is important in regional and exploration seismology. Ray tracing is a powerful and popular method for this purpose. Wavefront construction (WFC) method handles wavefronts instead of individual rays, thereby controlling proper ray density on the wavefront. By adaptively controlling rays over a wavefront, it efficiently models wave propagation. Algorithms for a quasi-P wave wavefront construction method and a new coordinate system used to generate wavefront construction mesh are proposed and tested for numerical properties and modeling capabilities. Traveltimes, amplitudes, and other parameters, which can be used for seismic imaging such as migrations and synthetic seismograms, are computed from the wavefront construction method. Modeling with wavefront construction code is applied to anisotropic media as well as isotropic media. Synthetic seismograms are computed using the wavefront construction method as a new way of generating synthetics. To incorporate layered velocity models, the model based interpolation (MBI) ray tracing method, which is designed to take advantage of the wavefront construction method as well as conventional ray tracing methods, is proposed and experimental codes are developed for it. Many wavefront construction codes are limited to smoothed velocity models for handling complicated problems in layered velocity models and the conventional ray tracing methods suffer from the inability to control ray density during wave propagation. By interpolating the wavefront near model boundaries, it is possible to handle the layered velocity model as well as overcome ray density control problems in conventional methods. The test results revealed this new method can be an effective modeling tool for accurate and effective computing.

  12. Ray tracing package through a lens system and a spectrometer

    SciTech Connect

    Zurro, B.; King, P.W.; Lazarus, E.A.

    1980-03-01

    To study the light collection optics of the ISX-B two-dimensional (2-D) Thomson scattering system, we have implemented in the Oak Ridge National Laboratory (ORNL) Fusion Energy Division (FED) PDP-10 two computer programs, LENS and SPECT, that trace rays through a lens system and a spectrometer, respectively. The lens package follows the path of any kind of ray (meridional or skew) through a centered optical system formed by an arbitrary number of spherical surfaces. The spectrometer package performs geometrical ray tracing through a Czerney-Turner spectrometer and can be easily modified for studying any other configuration. Contained herein is a description of the procedures followed and a listing of the computer programs.

  13. Modeling pyramidal sensors in ray-tracing software by a suitable user-defined surface

    NASA Astrophysics Data System (ADS)

    Antichi, Jacopo; Munari, Matteo; Magrin, Demetrio; Riccardi, Armando

    2016-04-01

    Following the unprecedented results in terms of performances delivered by the first light adaptive optics system at the Large Binocular Telescope, there has been a wide-spread and increasing interest on the pyramid wavefront sensor (PWFS), which is the key component, together with the adaptive secondary mirror, of the adaptive optics (AO) module. Currently, there is no straightforward way to model a PWFS in standard sequential ray-tracing software. Common modeling strategies tend to be user-specific and, in general, are unsatisfactory for general applications. To address this problem, we have developed an approach to PWFS modeling based on user-defined surface (UDS), whose properties reside in a specific code written in C language, for the ray-tracing software ZEMAX™. With our approach, the pyramid optical component is implemented as a standard surface in ZEMAX™, exploiting its dynamic link library (DLL) conversion then greatly simplifying ray tracing and analysis. We have utilized the pyramid UDS DLL surface-referred to as pyramidal acronyms may be too risky (PAM2R)-in order to design the current PWFS-based AO system for the Giant Magellan Telescope, evaluating tolerances, with particular attention to the angular sensitivities, by means of sequential ray-tracing tools only, thus verifying PAM2R reliability and robustness. This work indicates that PAM2R makes the design of PWFS as simple as that of other optical standard components. This is particularly suitable with the advent of the extremely large telescopes era for which complexity is definitely one of the main challenges.

  14. Ray tracing in discontinuous velocity model with implicit Interface

    NASA Astrophysics Data System (ADS)

    Zhang, Jianxing; Yang, Qin; Meng, Xianhai; Li, Jigang

    2016-07-01

    Ray tracing in the velocity model containing complex discontinuities is still facing many challenges. The main difficulty arises from the detection of the spatial relationship between the rays and the interfaces that are usually described in non-linear parametric forms. We propose a novel model representation method that can facilitate the implementation of classical shooting-ray methods. In the representation scheme, each interface is expressed as the zero contour of a signed distance field. A multi-copy strategy is adopted to describe the volumetric properties within blocks. The implicit description of the interface makes it easier to detect the ray-interface intersection. The direct calculation of the intersection point is converted into the problem of judging the signs of a ray segment's endpoints. More importantly, the normal to the interface at the intersection point can be easily acquired according to the signed distance field of the interface. The multiple storage of the velocity property in the proximity of the interface can provide accurate and unambiguous velocity information of the intersection point. Thus, the departing ray path can be determined easily and robustly. In addition, the new representation method can describe velocity models containing very complex geological structures, such as faults, salt domes, intrusions, and pinches, without any simplification. The examples on synthetic and real models validate the robustness and accuracy of the ray tracing based on the proposed model representation scheme.

  15. Ray Tracing Study of Magnetospheric ULF Wave Propagation.

    NASA Astrophysics Data System (ADS)

    Zhang, Xinbo

    1993-01-01

    A semi-empirical plasma density model and Mead -Fairfield magnetic field model are incorporated into a 3-D ray tracing code to study magnetospheric ULF wave propagation from the subsolar magnetopause. The ray-tracing of Pc3 compressional waves from the magnetosheath reveals that the magnetosphere can present a major propagation barrier to the penetration of these waves to the plasmasphere. This barrier is the ion-ion cutoff between the He^+ and O ^+ gyroresonances. As a result of the frequency -dependent location of this cutoff, the magnetosphere behaves like a filter for Pc3 compressional waves, and only the low frequency components can penetrate to the inner magnetosphere. These results are in agreement with previous satellite observations. This 'filter action' strongly depends on the relative concentration of He^+ and O^+ and is, therefore, sensitive to solar and magnetic activity. The study of the propagation characteristics of Pc3 transverse Alfven waves shows that these waves cannot penetrate to low Earth altitudes for wave frequencies above about approximately 0.03 hz. The configuration of the refractive index reveals an O^+-He^+ associated cutoff located between the assumed wave source in the equatorial magnetopause and the Earth. When the O^+ concentration is removed from the plasma composition, the barrier no longer exists, and waves with much higher frequencies than 0.03 Hz can penetrate to low altitudes. The result that the 0.03 Hz or lower frequency Alfven waves can be guided to the low altitudes agrees with ground-based power spectrum observations at high latitudes. The ray tracing study of Pc 1-2 waves reproduces earlier results (Rauch and Roux, 1982) for an H ^+-He^+ two-ion-species plasma, i.e. Pc 1-2 left hand polarized Alfven mode waves originating at equatorial geostationary orbit, below He ^+ gyrofrequency, are guided to the ground. However, our ray tracing study shows that previous Pc 1-2 ray tracing results are only valid in the absence of O

  16. Ray tracing reconstruction investigation for C-arm tomosynthesis

    NASA Astrophysics Data System (ADS)

    Malalla, Nuhad A. Y.; Chen, Ying

    2016-04-01

    C-arm tomosynthesis is a three dimensional imaging technique. Both x-ray source and the detector are mounted on a C-arm wheeled structure to provide wide variety of movement around the object. In this paper, C-arm tomosynthesis was introduced to provide three dimensional information over a limited view angle (less than 180o) to reduce radiation exposure and examination time. Reconstruction algorithms based on ray tracing method such as ray tracing back projection (BP), simultaneous algebraic reconstruction technique (SART) and maximum likelihood expectation maximization (MLEM) were developed for C-arm tomosynthesis. C-arm tomosynthesis projection images of simulated spherical object were simulated with a virtual geometric configuration with a total view angle of 40 degrees. This study demonstrated the sharpness of in-plane reconstructed structure and effectiveness of removing out-of-plane blur for each reconstruction algorithms. Results showed the ability of ray tracing based reconstruction algorithms to provide three dimensional information with limited angle C-arm tomosynthesis.

  17. A three-dimensional ray-tracing code dedicated to x-ray laser amplification simulation

    NASA Astrophysics Data System (ADS)

    Temporal, M.; Jacquemot, S.; Bonnet, L.; Decoster, A.

    2001-04-01

    A three-dimensional (3D) ray-tracing code has been developed to simulate the x-ray intensity produced in recent experiments where a silver target was driven by two laser beams. The code is used as a postprocessor of a detailed atomic physics code, which provides emissivities and opacities for inverted transitions. The hydrodynamics of the plasma is calculated with a 1D1/2 hydrocode where transverse profiles of temperature and density follow a self-similar solution. The 3D ray-tracing code accounts for progressive target illumination and calculates the x-ray laser output by solving the eikonal equation. Once 3D paths are determined, a steady-state transport solution is used to calculate the output intensity. The ray-tracing package is discussed first, then the present 3D results are compared with 2D calculations, as well as with collected experimental data.

  18. A Fast Ray-Tracing Using Bounding Spheres and Frustum Rays for Dynamic Scene Rendering

    NASA Astrophysics Data System (ADS)

    Suzuki, Ken-Ichi; Kaeriyama, Yoshiyuki; Komatsu, Kazuhiko; Egawa, Ryusuke; Ohba, Nobuyuki; Kobayashi, Hiroaki

    Ray tracing is one of the most popular techniques for generating photo-realistic images. Extensive research and development work has made interactive static scene rendering realistic. This paper deals with interactive dynamic scene rendering in which not only the eye point but also the objects in the scene change their 3D locations every frame. In order to realize interactive dynamic scene rendering, RTRPS (Ray Tracing based on Ray Plane and Bounding Sphere), which utilizes the coherency in rays, objects, and grouped-rays, is introduced. RTRPS uses bounding spheres as the spatial data structure which utilizes the coherency in objects. By using bounding spheres, RTRPS can ignore the rotation of moving objects within a sphere, and shorten the update time between frames. RTRPS utilizes the coherency in rays by merging rays into a ray-plane, assuming that the secondary rays and shadow rays are shot through an aligned grid. Since a pair of ray-planes shares an original ray, the intersection for the ray can be completed using the coherency in the ray-planes. Because of the three kinds of coherency, RTRPS can significantly reduce the number of intersection tests for ray tracing. Further acceleration techniques for ray-plane-sphere and ray-triangle intersection are also presented. A parallel projection technique converts a 3D vector inner product operation into a 2D operation and reduces the number of floating point operations. Techniques based on frustum culling and binary-tree structured ray-planes optimize the order of intersection tests between ray-planes and a sphere, resulting in 50% to 90% reduction of intersection tests. Two ray-triangle intersection techniques are also introduced, which are effective when a large number of rays are packed into a ray-plane. Our performance evaluations indicate that RTRPS gives 13 to 392 times speed up in comparison with a ray tracing algorithm without organized rays and spheres. We found out that RTRPS also provides competitive

  19. Auroral kilometric radiation source characteristics using ray tracing techniques

    NASA Astrophysics Data System (ADS)

    Schreiber, R.; Santolik, O.; Parrot, M.; Lefeuvre, F.; Hanasz, J.; Brittnacher, M.; Parks, G.

    2002-11-01

    3-D ray tracing to the presumed auroral kilometric radiation (AKR) source region has been performed using the input data from wave distribution function (WDF) based on the AKR waveforms recorded on board the Interball 2 satellite by the French wave experiment MEMO. Both the direction of the WDF maximum and the WDF form and angular size have been taken into account. Two instances of AKR emissions were observed on 28 January 1997 at 2037 and 2107 UT. Rays traced in R-X mode out of the s/c point toward two different active regions on the auroral oval (as seen with Polar UV imager after projection of the source region along the magnetic field lines down to the ionosphere level). Source region apparent angular sizes based on WDF are compatible with sizes estimated from signal modulation produced by electric antenna system rotation.

  20. Fast stereoscopic images with ray-traced volume rendering

    SciTech Connect

    Adelson, S.J.; Hansen, C.D.

    1994-05-01

    One of the drawbacks of standard volume rendering techniques is that is it often difficult to comprehend the three-dimensional structure of the volume from a single frame; this is especially true in cases where there is no solid surface. Generally, several frames must be generated and viewed sequentially, using motion parallax to relay depth. Another option is to generate a single spectroscopic pair, resulting in clear and unambiguous depth information in both static and moving images. Methods have been developed which take advantage of the coherence between the two halves of a stereo pair for polygon rendering and ray-tracing, generating the second half of the pair in significantly less time than that required to completely render a single image. This paper reports the results of implementing these techniques with parallel ray-traced volume rendering. In tests with different data types, the time savings is in the range of 70--80%.

  1. Stochastic ray tracing for simulation of high intensity focal ultrasound therapy.

    PubMed

    Koskela, Julius; Vahala, Erkki; de Greef, Martijn; Lafitte, Luc P; Ries, Mario

    2014-09-01

    An algorithm is presented for rapid simulation of high-intensity focused ultrasound (HIFU) fields. Essentially, the method combines ray tracing with Monte Carlo integration to evaluate the Rayleigh-Sommerfeld integral. A large number of computational particles, phonons, are distributed among the elements of a phase-array transducer. The phonons are emitted into random directions and are propagated along trajectories computed with the ray tracing method. As the simulation progresses, an improving stochastic estimate of the acoustic field is obtained. The method can adapt to complicated geometries, and it is well suited to parallelization. The method is verified against reference simulations and pressure measurements from an ex vivo porcine thoracic tissue sample. Results are presented for acceleration with graphics processing units (GPUs). The method is expected to serve in applications, where flexibility and rapid computation time are crucial, in particular clinical HIFU treatment planning. PMID:25190416

  2. Ray tracing homogenizing mirrors for synchrotron x-ray lithography

    NASA Astrophysics Data System (ADS)

    Homer, Michael; Rosser, Roy J.; Speer, R. J.

    1991-12-01

    Saddle toroid array mirrors (STAMs) are novel grazing-incidence mirrors. They have been proposed as the optical component that most efficiently matches synchrotron orbital radiation (SOR) to the needs of proximity x-ray lithography. However, STAMs have yet to be accepted by the synchrotron lithography community because of the lack of detailed data on their expected performance, due primarily to the difficulty of raytracing such mirrors using existing optical raytrace programs. A raytracing package written especially to study the design and optimization of these unusually shaped mirrors and the very encouraging results obtained with the package to date are described. The optimum STAM designs turn out to be the most effective way of homogeneously illuminating a rectangular proximity x-ray lithography mask, improving on existing scanning mirror systems by at least a factor of four. They have the added advantage of being stationary, which should lead to greater reliability--a quality of considerable value in the production environment these mirrors are intended for, namely the ultra-high vacuum of a synchrotron beamline. Based on the results of the raytracing, a prototype STAM has been constructed, and preparations are being made for an x-ray test of the device.

  3. 3D ultrasonic ray tracing in AutoCAD®

    NASA Astrophysics Data System (ADS)

    Reilly, D.; Leggat, P.; McNab, A.

    2001-04-01

    To assist with the design and validation of testing procedures for NDT, add-on modules have been developed for AutoCAD® 2000. One of the modules computes and displays ultrasonic 3D ray tracing. Another determines paths between two points, for instance a probe and a target or two probes. The third module displays phased array operational modes and calculates element delays for phased array operation. The modules can be applied to simple or complex solid model components.

  4. grtrans: Polarized general relativistic radiative transfer via ray tracing

    NASA Astrophysics Data System (ADS)

    Dexter, Jason

    2016-05-01

    grtrans calculates ray tracing radiative transfer in the Kerr metric, including the full treatment of polarised radiative transfer and parallel transport along geodesics, for comparing theoretical models of black hole accretion flows and jets with observations. The code is written in Fortran 90 and parallelizes with OpenMP; the full code and several components have Python interfaces. grtrans includes Geokerr (ascl:1011.015) and requires cfitsio (ascl:1010.001) and pyfits (ascl:1207.009).

  5. Ray tracing for point distribution in unstructured grid generation

    SciTech Connect

    Khamayseh, A.; Ortega, F.; Trease, H.

    1995-12-31

    We present a procedure by which grid points are generated on surfaces or within three-dimensional volumes to produce high quality unstructed grids for complex geometries. The virtue of this method is based on ray-tracing approach for curved polyhedra whose faces may lie on natural quadrics (planes, cylinders, cones, or spheres) or triangular faceted surfaces. We also present an efficient point location algorithm for identifying points relative to various regions with classification of inside/on/outside.

  6. grtrans: Polarized general relativistic radiative transfer via ray tracing

    NASA Astrophysics Data System (ADS)

    Dexter, Jason

    2016-05-01

    grtrans calculates ray tracing radiative transfer in the Kerr metric, including the full treatment of polarised radiative transfer and parallel transport along geodesics, for comparing theoretical models of black hole accretion flows and jets with observations. The code is written in Fortran 90 and parallelizes with OpenMP; the full code and several components have Python interfaces. grtrans requires Geokerr (ascl:1011.015), cfitsio (ascl:1010.001), and pyfits (ascl:1207.009).

  7. Ray tracing software application in VIP lamp design

    NASA Astrophysics Data System (ADS)

    Rehn, Henning

    2002-08-01

    In our contribution we demonstrate a wide variety of ray tracing software applications for the design of VIP short-arc discharge video projection lamps. On the basis of simulations we derive design rules for the lamp itself and for its optical environment. Light Tools software acts as a means to understand the collection efficiency of a VIP lamp with an elliptical reflector and as an instrument to prove the conclusions.

  8. Accelerated ray tracing algorithm under urban macro cell

    NASA Astrophysics Data System (ADS)

    Liu, Z.-Y.; Guo, L.-X.; Guan, X.-W.

    2015-10-01

    In this study, an ray tracing propagation prediction model, which is based on creating a virtual source tree, is used because of their high efficiency and reliable prediction accuracy. In addition, several acceleration techniques are also adopted to improve the efficiency of ray-tracing-based prediction over large areas. However, in the process of employing the ray tracing method for coverage zone prediction, runtime is linearly proportional to the total number of prediction points, leading to large and sometimes prohibitive computation time requirements under complex geographical urban macrocell environments. In order to overcome this bottleneck, the compute unified device architecture (CUDA), which provides fine-grained data parallelism and thread parallelism, is implemented to accelerate the calculation. Taking full advantage of tens of thousands of threads in CUDA program, the decomposition of the coverage prediction problem is firstly conducted by partitioning the image tree and the visible prediction points to different sources. Then, we make every thread calculate the electromagnetic field of one propagation path and then collect these results. Comparing this parallel algorithm with the traditional sequential algorithm, it can be found that computational efficiency has been improved.

  9. Three dimensional ray tracing of the Jovian magnetosphere in the low frequency range

    NASA Technical Reports Server (NTRS)

    Menietti, J. D.

    1984-01-01

    Ray tracing studies of Jovian low frequency emissions were studied. A comprehensive three-dimensional ray tracing computer code for examination of model Jovian decametric (DAM) emission was developed. The improvements to the computer code are outlined and described. The results of the ray tracings of Jovian emissions will be presented in summary form.

  10. Ray-tracing in a two-dimensional ionosphere

    NASA Astrophysics Data System (ADS)

    Labahn, R. W.

    1985-08-01

    The quasi-parabolic method is adapted to ray-track through a medium with horizontal gradients in electron density. The resulting method is applicable to any model ionosphere without the requirements for numerical derivatives. Example calculations are given for model ledges and troughs and an average worldwide ionospheric model.

  11. Graphical User Interface for Interactive Seismic Ray Tracing

    NASA Astrophysics Data System (ADS)

    Song, Jianli; ten Brink, Uri

    2005-03-01

    RayGUI 2.0 is a new version of RayGUI, a graphical user interface (GUI) to the seismic travel time modeling program of Zelt and Smith [1992]. It represents a significant improvement over the previous version of RayGUI (RayGUI 1.04; Loss et al. [1998a,1998b]). RayGUI 2.0 uses an updated Java version (1.3), and can run on various operating systems (UNIX, Linux, and Mac OS X). Several new functions have been incorporated, including executing the forward and inversion codes of Zelt and Smith [1992], creating models or adding new parts of models from an ASCII file, graphically adding layers or points, graphically pinching layers, changing the velocity value of a control point, reporting point location and velocity, importing travel-time lists, generating postscript files, exporting the velocity model into an ASCII file, generating 1-D velocity profiles at specified locations, calculating root-mean-square errors between observed and calculated arrivals for selected phases, and accessing the ray trace log, as well as several other new display features.

  12. Dynamic ray tracing and its application in triangulated media

    SciTech Connect

    Rueger, A.

    1993-07-01

    Hale and Cohen (1991) developed software to generate two-dimensional computer models of complex geology. Their method uses a triangulation technique designed to support efficient and accurate computation of seismic wavefields for models of the earth`s interior. Subsequently, Hale (1991) used this triangulation approach to perform dynamic ray tracing and create synthetic seismograms based on the method of Gaussian beams. Here, I extend this methodology to allow an increased variety of ray-theoretical experiments. Specifically, the developed program GBmod (Gaussian Beam MODeling) can produce arbitrary multiple sequences and incorporate attenuation and density variations. In addition, I have added an option to perform Fresnel-volume ray tracing (Cerveny and Soares, 1992). Corrections for reflection and transmission losses at interfaces, and for two-and-one-half-dimensional (2.5-D) spreading are included. However, despite these enhancements, difficulties remain in attempts to compute accurate synthetic seismograms if strong lateral velocity inhomogeneities are present. Here, these problems are discussed and, to a certain extent, reduced. I provide example computations of high-frequency seismograms based on the method of Gaussian beams to exhibit the advantages and disadvantages of the proposed modeling method and illustrate new features for both surface and vertical seismic profiling (VSP) acquisition geometries.

  13. Microseismic network design assessment based on 3D ray tracing

    NASA Astrophysics Data System (ADS)

    Näsholm, Sven Peter; Wuestefeld, Andreas; Lubrano-Lavadera, Paul; Lang, Dominik; Kaschwich, Tina; Oye, Volker

    2016-04-01

    There is increasing demand on the versatility of microseismic monitoring networks. In early projects, being able to locate any triggers was considered a success. These early successes led to a better understanding of how to extract value from microseismic results. Today operators, regulators, and service providers work closely together in order to find the optimum network design to meet various requirements. In the current study we demonstrate an integrated and streamlined network capability assessment approach. It is intended for use during the microseismic network design process prior to installation. The assessments are derived from 3D ray tracing between a grid of event points and the sensors. Three aspects are discussed: 1) Magnitude of completeness or detection limit; 2) Event location accuracy; and 3) Ground-motion hazard. The network capability parameters 1) and 2) are estimated at all hypothetic event locations and are presented in the form of maps given a seismic sensor coordinate scenario. In addition, the ray tracing traveltimes permit to estimate the point-spread-functions (PSFs) at the event grid points. PSFs are useful in assessing the resolution and focusing capability of the network for stacking-based event location and imaging methods. We estimate the performance for a hypothetical network case with 11 sensors. We consider the well-documented region around the San Andreas Fault Observatory at Depth (SAFOD) located north of Parkfield, California. The ray tracing is done through a detailed velocity model which covers a 26.2 by 21.2 km wide area around the SAFOD drill site with a resolution of 200 m both for the P-and S-wave velocities. Systematic network capability assessment for different sensor site scenarios prior to installation facilitates finding a final design which meets the survey objectives.

  14. Comment on "Improved ray tracing air mass numbers model"

    NASA Astrophysics Data System (ADS)

    van der Werf, Siebren Y.

    2008-01-01

    Air mass numbers have traditionally been obtained by techniques that use height as the integration variable. This introduces an inherent singularity at the horizon, and ad hoc solutions have been invented to cope with it. A survey of the possible options including integration by height, zenith angle, and horizontal distance or path length is presented. Ray tracing by path length is shown to avoid singularities both at the horizon and in the zenith. A fourth-order Runge-Kutta numerical integration scheme is presented, which treats refraction and air mass as path integrals. The latter may optionally be split out into separate contributions of the atmosphere's constituents.

  15. A complete ray-trace analysis of the Mirage toy

    NASA Astrophysics Data System (ADS)

    Adhya, Sriya; Noé, John W.

    2007-06-01

    The `Mirage' (Opti-Gone International) is a well-known optics demonstration (PIRA index number 6A20.35) that uses two opposed concave mirrors to project a real image of a small object into space. We studied image formation in the Mirage by standard 2x2 matrix methods and by exact ray tracing, with particular attention to additional real images that can be observed when the mirror separation is increased beyond one focal length. We find that the three readily observed secondary images correspond to 4, 6, or 8 reflections, respectively, contrary to previous reports.

  16. Ray tracing study for non-imaging daylight collectors

    SciTech Connect

    Wittkopf, Stephen; Oliver Grobe, Lars; Geisler-Moroder, David; Compagnon, Raphael; Kaempf, Jerome; Linhart, Friedrich; Scartezzini, Jean-Louis

    2010-06-15

    This paper presents a novel method to study how well non-imaging daylight collectors pipe diffuse daylight into long horizontal funnels for illuminating deep buildings. Forward ray tracing is used to derive luminous intensity distributions curves (LIDC) of such collectors centered in an arc-shaped light source representing daylight. New photometric characteristics such as 2D flux, angular spread and horizontal offset are introduced as a function of such LIDC. They are applied for quantifying and thus comparing different collector contours. (author)

  17. Photorealistic ray tracing to visualize automobile side mirror reflective scenes.

    PubMed

    Lee, Hocheol; Kim, Kyuman; Lee, Gang; Lee, Sungkoo; Kim, Jingu

    2014-10-20

    We describe an interactive visualization procedure for determining the optimal surface of a special automobile side mirror, thereby removing the blind spot, without the need for feedback from the error-prone manufacturing process. If the horizontally progressive curvature distributions are set to the semi-mathematical expression for a free-form surface, the surface point set can then be derived through numerical integration. This is then converted to a NURBS surface while retaining the surface curvature. Then, reflective scenes from the driving environment can be virtually realized using photorealistic ray tracing, in order to evaluate how these reflected images would appear to drivers. PMID:25401606

  18. Large thin adaptive x-ray mirrors

    NASA Astrophysics Data System (ADS)

    Doel, Peter; Atkins, Carolyn; Thompson, Samantha; Brooks, David; Yao, Jun; Feldman, Charlotte; Willingale, Richard; Button, Tim; Zhang, Dou; James, Ady

    2007-09-01

    This paper describes the progress made in a proof of concept study and recent results of a research program into large active x-ray mirrors that is part of the UK Smart X-ray Optics project. The ultimate aim is to apply the techniques of active/adaptive optics to the next generation of nested shell astronomical X-ray space telescopes. A variety of deformable mirror technologies are currently available, the most promising of which for active X-ray mirrors are probably unimorph and bimorph piezoelectric mirrors. In this type of mirror one or more sheets of piezoelectric material are bonded to or coated with a passive reflective layer. On the back or between the piezoceramic layer/layers are series of electrodes. Application of an electric field causes the piezoelectric material to undergo local deformation thus changing the mirror shape. Starting in 2005 a proof of concept active mirror research program has been undertaken. This work included modelling and development of actively controlled thin shell mirrors. Finite element models of piezo-electric actuated mirrors have been developed and verified against experimental test systems. This has included the modelling and test of piezo-electric hexagonal unimorph segments. Various actuator types and low shrinkage conductive bonding methods have been investigated and laboratory tests of the use of piezo-electric actuators to adjust the form of an XMM-Newton space telescope engineering model mirror shell have been conducted and show that movement of the optics at the required level is achievable. Promising technological approaches have been identified including moulded piezo-ceramics and piezo-electrics fibre bundles.

  19. Ray-tracing software comparison for linear focusing solar collectors

    NASA Astrophysics Data System (ADS)

    Osório, Tiago; Horta, Pedro; Larcher, Marco; Pujol-Nadal, Ramón; Hertel, Julian; van Rooyen, De Wet; Heimsath, Anna; Schneider, Simon; Benitez, Daniel; Frein, Antoine; Denarie, Alice

    2016-05-01

    Ray-Tracing software tools have been widely used in the optical design of solar concentrating collectors. In spite of the ability of these tools to assess the geometrical and material aspects impacting the optical performance of concentrators, their use in combination with experimental measurements in the framework of collector testing procedures as not been implemented, to the date, in none of the current solar collector testing standards. In the latest revision of ISO9806 an effort was made to include linear focusing concentrating collectors but some practical and theoretical difficulties emerged. A Ray-Tracing analysis could provide important contributions to overcome these issues, complementing the experimental results obtained through thermal testing and allowing the achievement of more thorough testing outputs with lower experimental requirements. In order to evaluate different available software tools a comparison study was conducted. Taking as representative technologies for line-focus concentrators the Parabolic Trough Collector and the Linear Fresnel Reflector Collector, two exemplary cases with predefined conditions - geometry, sun model and material properties - were simulated with different software tools. This work was carried out within IEA/SHC Task 49 "Solar Heat Integration in Industrial Processes".

  20. Ray Tracing Modeling of Gravity Wave Propagation and Dissipation

    NASA Astrophysics Data System (ADS)

    Vadas, Sharon; Crowley, Geoff

    In this paper, we describe a ray trace model which calculates the wavevector, location and phase of a gravity wave (GW) as it propagates in the lower atmosphere and thermosphere. If used for a discreet transient source (such as a deep convective plume), we describe how this model can calculate the body forcing and the heat/cooling that are created when the GWs within a wave packet dissipate in the thermosphere from kinematic viscosity and thermal diffusivity. Although the body force calculation requires only the divergence of the momentum flux, the heat/cooling calculation requires the reconstructed GW field (e.g., density, velocity perturbations), which in turn requires the GW dissipative polarization relations. We describe these relations. We then describe the results of a recent study involving GWs identified from TIDDBIT HF Doppler sounder data taken at Wallops Island, VI, USA. Using this ray trace model, we determine if the unusual neutral wind profile measured by a rocket experiment at high altitudes (~290-370 km) could have been caused by the propagation and dissipation of several waves observed by TIDDBIT at lower altitudes.

  1. Ray-traced tropospheric total slant delays for GNSS processing

    NASA Astrophysics Data System (ADS)

    Hobiger, T.; Ichikawa, R.; Hatanaka, Y.; Yutsudo, T.; Iwashita, C.; Miyahara, B.; Koyama, Y.; Kondo, T.

    2007-12-01

    Numerical weather models have undergone an improvement of spatial and temporal resolution in the recent years, which made their use for GNSS applications feasible. Ray-tracing through such models permits the computation of total troposphere delays and ray-bending angles. At the National Institute of Information and Communications Technology (NICT), Japan the so-called KAshima RAy-tracing Tools (KARAT) have been developed which allow to obtain troposphere delay corrections in real-time. Together with fine-mesh weather models from the Japanese Meteorological Agency (JMA) huge parts of the East Asian region, including Japan, Korea, Taiwan and East China, can be covered. The Japanese GEONET with its more than 1300 GNSS receivers represent an ideal test-bed for the evaluation of the performance of KARAT. In cooperation with the Geographical Survey Institute (GSI), Japan more than 1.6 billion observations, covering measurements from July 1st until August 31st, 2006, were processed and the corresponding troposphere delays were used to modify the original RINEX files by subtraction of code- and phase delays. These modified observations were processed by a dedicated analysis run of the GEONET operation center, taking advantage of the computer cluster at GSI. First results from this study, together with an in-depth discussion about the assets and drawbacks of the reduction of troposphere total slant delays will be given in this presentation. Additionally an overview about KARAT, the treatment of observational data and the impact of future refined numerical weather models on GNSS analysis will be included in this contribution.

  2. Ray Tracing to Predict Optical Behaviour of Shock Compressed Dielectrics

    NASA Astrophysics Data System (ADS)

    Tear, Gareth R.; Proud, William G.

    2015-06-01

    In order to investigate the optical response of dielectric materials under shock compression, a characteristics model has been combined with a three dimensional optical ray tracing model. A general biaxial optical model is used along with a first order photoelastic model which couples the characteristics component to the optical component. This optical model is three dimensional and as such can be used to investigate small deviations from the perfect one dimensional shock wave which is typically assumed in plate impact experiments. A detailed description of the model will be presented, and comparison to available literature as well as recent experiments on the optical behaviour of shock compressed a-cut calcite and a-cut sapphire. The authors would like to thank Dr D E Eakins and Dr D J Chapman for fruitful discussions. The Institute of Shock Physics acknowledges the continued support of AWE and Imperial College London.

  3. Ray tracing in FLRW flat space-times

    NASA Astrophysics Data System (ADS)

    Acquaviva, Giovanni; Bonetti, Luca; Cognola, Guido; Zerbini, Sergio

    2013-12-01

    In this work we take moves from the debate triggered by Melia et al. in [J. Cosmol. Astropart. Phys. 09 (2012) 029; Mon. Not. R. Astron. Soc. 421, 3356 (2012)] and followed by opposite comments by Lewis and Oirschot in [Mon. Not. R. Astron. Soc. Lett. 423, 26 (2012); 431, 25 (2013)]. The point in question regards the role of the Hubble horizon as a limit for observability in a cosmological setting. We propose to tackle the issue in a broader way by relating it to the causal character of the Hubble surface and to the tracing of null trajectories, focusing on both three-fluids and generalized Chaplygin gas models. The results should make clear that for quite reasonable and physically motivated models, light rays reaching a comoving observer at R(t0)=0 have never traveled a distance greater than the proper radius of the horizon until t0.

  4. Calculation of material properties and ray tracing in transformation media.

    PubMed

    Schurig, D; Pendry, J B; Smith, D R

    2006-10-16

    Complex and interesting electromagnetic behavior can be found in spaces with non-flat topology. When considering the properties of an electromagnetic medium under an arbitrary coordinate transformation an alternative interpretation presents itself. The transformed material property tensors may be interpreted as a different set of material properties in a flat, Cartesian space. We describe the calculation of these material properties for coordinate transformations that describe spaces with spherical or cylindrical holes in them. The resulting material properties can then implement invisibility cloaks in flat space. We also describe a method for performing geometric ray tracing in these materials which are both inhomogeneous and anisotropic in their electric permittivity and magnetic permeability. PMID:19529371

  5. Polarization Ray Trace Model of the MODIS Instrument

    NASA Technical Reports Server (NTRS)

    Waluschka, Eugene; Xiong, Jack; Esaias, Wayne E.; Voss, Kenneth; Souaidia, Nordine; Pellicori, Samuel; Moyer, David; Guenther, Bruce; Barnes, William

    2004-01-01

    Sunlight reflected from the earth is, to a certain extent, polarized. Radiometers, such as the MODIS instrument on board the TERRA and AQUA spacecraft, are to a certain extent polarizers. Accurate radiometric measurements must take into account both the polarization state of the scene and the polarization sensitivity of the measuring instrument. The measured polarization characteristics of the MODIS instruments are contained in various radiometric models. Continued use of these radiometric math models, over a number of years, have shown where these models can be improved. Currently a MODIS polarization ray trace model has been created which models the thin film structure on the optical elements. This approach is described and modeled and measured instrument polarization sensitivity results presented.

  6. A FORMALISM FOR COVARIANT POLARIZED RADIATIVE TRANSPORT BY RAY TRACING

    SciTech Connect

    Gammie, Charles F.; Leung, Po Kin

    2012-06-20

    We write down a covariant formalism for polarized radiative transfer appropriate for ray tracing through a turbulent plasma. The polarized radiation field is represented by the polarization tensor (coherency matrix) N{sup {alpha}{beta}} {identical_to} (a{sup {alpha}}{sub k} a*{sup {beta}}{sub k}), where a{sub k} is a Fourier coefficient for the vector potential. Using Maxwell's equations, the Liouville-Vlasov equation, and the WKB approximation, we show that the transport equation in vacuo is k{sup {mu}}{nabla}{sub {mu}} N{sup {alpha}{beta}} = 0. We show that this is equivalent to Broderick and Blandford's formalism based on invariant Stokes parameters and a rotation coefficient, and suggest a modification that may reduce truncation error in some situations. Finally, we write down several alternative approaches to integrating the transfer equation.

  7. Ray trace calculation of ionospheric propagation at lower frequencies

    NASA Astrophysics Data System (ADS)

    Reilly, Michael H.

    2006-10-01

    The Raytrace/Ionospheric Conductivity and Electron Density-Bent-Gallagher model has been revised to make it applicable to ionospheric propagation at low radio frequencies (0.5-5.0 MHz), where the ionosphere and magnetic anisotropy drastically alter propagation paths and provide a severe test of propagation model algorithms. The necessary revisions are discussed, and the model is applied to the problem of ionospheric penetration from a source below the ionosphere to a receiver above the ionosphere. It is necessary to include the electron collision frequency in the Appleton-Hartree index of refraction in order to permit ionospheric penetration for radio frequencies below the maximum plasma frequency (e.g., whistler modes). The associated reformulation of the ray trace equations for a complex index of refraction is straightforward. Difficulties with numerical methods are cited for the lowest frequencies, and future improvements are indicated.

  8. Ionospheric Plasma Drift Analysis Technique Based On Ray Tracing

    NASA Astrophysics Data System (ADS)

    Ari, Gizem; Toker, Cenk

    2016-07-01

    Ionospheric drift measurements provide important information about the variability in the ionosphere, which can be used to quantify ionospheric disturbances caused by natural phenomena such as solar, geomagnetic, gravitational and seismic activities. One of the prominent ways for drift measurement depends on instrumentation based measurements, e.g. using an ionosonde. The drift estimation of an ionosonde depends on measuring the Doppler shift on the received signal, where the main cause of Doppler shift is the change in the length of the propagation path of the signal between the transmitter and the receiver. Unfortunately, ionosondes are expensive devices and their installation and maintenance require special care. Furthermore, the ionosonde network over the world or even Europe is not dense enough to obtain a global or continental drift map. In order to overcome the difficulties related to an ionosonde, we propose a technique to perform ionospheric drift estimation based on ray tracing. First, a two dimensional TEC map is constructed by using the IONOLAB-MAP tool which spatially interpolates the VTEC estimates obtained from the EUREF CORS network. Next, a three dimensional electron density profile is generated by inputting the TEC estimates to the IRI-2015 model. Eventually, a close-to-real situation electron density profile is obtained in which ray tracing can be performed. These profiles can be constructed periodically with a period of as low as 30 seconds. By processing two consequent snapshots together and calculating the propagation paths, we estimate the drift measurements over any coordinate of concern. We test our technique by comparing the results to the drift measurements taken at the DPS ionosonde at Pruhonice, Czech Republic. This study is supported by TUBITAK 115E915 and Joint TUBITAK 114E092 and AS CR14/001 projects.

  9. Image transfer through cirrus clouds. I. Ray trace analysis and wave-front reconstruction.

    PubMed

    Landesman, B T; Kindilien, P J; Matson, C L; Caudill, T R

    2000-10-20

    A new technique for modeling image transfer through cirrus clouds is presented. The technique uses a ray trace to model beam propagation through a three-dimensional volume of polydisperse, hexagonal ice crystals. Beyond the cloud, the technique makes use of standard Huygens-Fresnel propagation methods. At the air-cloud interface, each wave front is resolved into a ray distribution for input to the ray trace software. Similarly, a wave front is reconstructed from the output ray distribution at the cloud-air interface. Simulation output from the ray trace program is presented and the modulation transfer function for stars imaged through cirrus clouds of varying depths is discussed. PMID:18354542

  10. General Relativistic Ray Tracing for X-ray Reverberation and Polarimetry Studies of Black Holes

    NASA Astrophysics Data System (ADS)

    Hoormann, Janie; Krawczynski, Henric

    2015-01-01

    We present the results of General Relativistic (GR) ray tracing calculations of the X-ray emission from mass accreting stellar mass and supermassive black holes. Our study aims at exploring the X-ray reverberation and X-ray polarimetry signatures of different accretion flow geometries and different spacetime backgrounds (GR and non-GR backgrounds). We present first results derived for the well-known lamp-post model, where a point source of continuum emission illuminates an accretion disk with high energy photons which are tracked by parallel transporting the photon wave and polarization vectors. The simulation code models the reprocessing and reflection by of photons impinging on the accretion disk. We study the degeneracy of astrophysical parameters (parametrizing the geometry of the accretion disk and the location and properties of the lamppost photon source) and the parameters describing the underlying metrics. We emphasize furthermore the difference of the observational signatures for stellar mass and supermassive black holes.

  11. RAY-RAMSES: a code for ray tracing on the fly in N-body simulations

    NASA Astrophysics Data System (ADS)

    Barreira, Alexandre; Llinares, Claudio; Bose, Sownak; Li, Baojiu

    2016-05-01

    We present a ray tracing code to compute integrated cosmological observables on the fly in AMR N-body simulations. Unlike conventional ray tracing techniques, our code takes full advantage of the time and spatial resolution attained by the N-body simulation by computing the integrals along the line of sight on a cell-by-cell basis through the AMR simulation grid. Moroever, since it runs on the fly in the N-body run, our code can produce maps of the desired observables without storing large (or any) amounts of data for post-processing. We implemented our routines in the RAMSES N-body code and tested the implementation using an example of weak lensing simulation. We analyse basic statistics of lensing convergence maps and find good agreement with semi-analytical methods. The ray tracing methodology presented here can be used in several cosmological analysis such as Sunyaev-Zel'dovich and integrated Sachs-Wolfe effect studies as well as modified gravity. Our code can also be used in cross-checks of the more conventional methods, which can be important in tests of theory systematics in preparation for upcoming large scale structure surveys.

  12. Generalized ray tracing method for the calculation of the peripheral refraction induced by an ophthalmic lens

    NASA Astrophysics Data System (ADS)

    Rojo, Pilar; Royo, Santiago; Caum, Jesus; Ramírez, Jorge; Madariaga, Ines

    2015-02-01

    Peripheral refraction, the refractive error present outside the main direction of gaze, has lately attracted interest due to its alleged relationship with the progression of myopia. The ray tracing procedures involved in its calculation need to follow an approach different from those used in conventional ophthalmic lens design, where refractive errors are compensated only in the main direction of gaze. We present a methodology for the evaluation of the peripheral refractive error in ophthalmic lenses, adapting the conventional generalized ray tracing approach to the requirements of the evaluation of peripheral refraction. The nodal point of the eye and a retinal conjugate surface will be used to evaluate the three-dimensional distribution of refractive error around the fovea. The proposed approach enables us to calculate the three-dimensional peripheral refraction induced by any ophthalmic lens at any direction of gaze and to personalize the lens design to the requirements of the user. The complete evaluation process for a given user prescribed with a -5.76D ophthalmic lens for foveal vision is detailed, and comparative results obtained when the geometry of the lens is modified and when the central refractive error is over- or undercorrected. The methodology is also applied for an emmetropic eye to show its application for refractive errors other than myopia.

  13. Fast Ray Tracing of Lunar Digital Elevation Models

    NASA Technical Reports Server (NTRS)

    McClanahan, Timothy P.; Evans, L. G.; Starr, R. D.; Mitrofanov, I.

    2009-01-01

    Ray-tracing (RT) of Lunar Digital Elevation Models (DEM)'s is performed to virtually derive the degree of radiation incident to terrain as a function of time, orbital and ephemeris constraints [I- 4]. This process is an integral modeling process in lunar polar research and exploration due to the present paucity of terrain information at the poles and mission planning activities for the anticipated spring 2009 launch of the Lunar Reconnaissance Orbiter (LRO). As part of the Lunar Exploration Neutron Detector (LEND) and Lunar Crater Observation and Sensing Satellite (LCROSS) preparations RI methods are used to estimate the critical conditions presented by the combined effects of high latitude, terrain and the moons low obliquity [5-7]. These factors yield low incident solar illumination and subsequently extreme thermal, and radiation conditions. The presented research uses RT methods both for radiation transport modeling in space and regolith related research as well as to derive permanently shadowed regions (PSR)'s in high latitude topographic minima, e.g craters. These regions are of scientific and human exploration interest due to the near constant low temperatures in PSRs, inferred to be < 100 K. Hydrogen is thought to have accumulated in PSR's through the combined effects of periodic cometary bombardment and/or solar wind processes, and the extreme cold which minimizes hydrogen sublimation [8-9]. RT methods are also of use in surface position optimization for future illumination dependent on surface resources e.g. power and communications equipment.

  14. Ray-tracing simulations of coupled dark energy models

    NASA Astrophysics Data System (ADS)

    Pace, Francesco; Baldi, Marco; Moscardini, Lauro; Bacon, David; Crittenden, Robert

    2015-02-01

    Dark matter and dark energy are usually assumed to couple only gravitationally. An extension to this picture is to model dark energy as a scalar field coupled directly to cold dark matter. This coupling leads to new physical effects, such as a fifth force and a time-dependent dark matter particle mass. In this work we examine the impact that coupling has on weak lensing statistics by constructing realistic simulated weak lensing maps using ray-tracing techniques through N-body cosmological simulations. We construct maps for different lensing quantities, covering a range of scales from a few arcminutes to several degrees. The concordance Λ cold dark matter (ΛCDM) model is compared to different coupled dark energy models, described either by an exponential scalar field potential (standard coupled dark energy scenario) or by a SUGRA potential (bouncing model). We analyse several statistical quantities and our results, with sources at low redshifts are largely consistent with previous work on cosmic microwave background lensing by Carbone et al. The most significant differences from the ΛCDM model are due to the enhanced growth of the perturbations and to the effective friction term in non-linear dynamics. For the most extreme models, we see differences in the power spectra up to 40 per cent compared to the ΛCDM model. The different time evolution of the linear matter overdensity can account for most of the differences, but when controlling for this using a ΛCDM model having the same normalization, the overall signal is smaller due to the effect of the friction term appearing in the equation of motion for dark matter particles.

  15. Trace metals and their relation to bacterial infections studied by X-ray microscopy

    NASA Astrophysics Data System (ADS)

    Maser, J.; Wagner, D.; Lai, B.; Cai, Z.; Legnini, D.; Moric, I.; Bermudez, L.

    2003-03-01

    Bacterial pathogens survive in different environments in the human host by responding with expression of virulence factors that enable them to adapt to changing conditions. Trace elements regulate the expression of many virulence genes in bacteria and are thus important for their survival in the host. Mycobacteria are intracellular pathogens that can cause diseases such as tuberculosis or secondary infections in immunocompromised patients. We have used a hard x-ray microprobe to study the trace element distribution in the mycobacterial phagosome after infection of macrophages. We have studied phagosomes with virulent (M. avium) and nonvirulent (M. smegmatis) mycobacteria. In this article, we will show that the iron concentration in phagosomes with macrophages infected with nonvirulent M. smegmatis is reduced 24 hours after infection but increased in phagosomes in cells infected with virulent M. avium. In addition, we will show the effect activation of macrophages with tumor necrosis factor (TNF-α) or interferon (IFN-γ) has on the iron concentration in M. avium.

  16. Reduction of discretization error for ray tracing of MOC through a correction on collision probabilities

    SciTech Connect

    Tabuchi, M.; Tatsumi, M.; Yamamoto, A.; Endo, T.

    2013-07-01

    A new correction model for ray tracing of the method of characteristics is proposed in order to reduce discretization error. As the ray tracing parameters such as azimuthal angle division, polar angle division and ray separation are considered in this study. In the method of characteristics, region average scalar fluxes can be implicitly expressed by collision probabilities, although these collision probabilities are not directly treated in the ordinary calculation scheme. From this viewpoint, difference between a coarse ray tracing condition and a detailed one can be interpreted as the difference in the estimation of collision probabilities. In other words, the discretization error for ray tracing can be recognized as a consequence of inaccurate collision probabilities caused by coarse ray tracing. This discussion suggests that accurate region average scalar flux can be obtained through an appropriate correction on collision probabilities. In this paper, a correction model on collision probabilities is theoretically derived based on the neutron balance equation, and its validity is confirmed through typical single assembly calculations. The effectiveness of the present correction method is also discussed in this paper. It is confirmed that discretization error for ray tracing can be significantly reduced by the present correction method in a multi-assembly calculation, though the correction factor is estimated in single assembly geometry. (authors)

  17. Three-dimensional ray tracing on Delaunay-based reconstructed surfaces.

    PubMed

    Ortiz, Sergio; Siedlecki, Damian; Remon, Laura; Marcos, Susana

    2009-07-10

    A method of ray tracing for free-form optical surfaces has been developed. The ray tracing through such surfaces is based on Delaunay triangulation of the discrete data of the surface and is related to finite-element modeling. Some numerical examples of applications to analytical, noisy, and experimental free-form surfaces (in particular, a corneal topography map) are presented. Ray-tracing results (i.e., spot diagram root-mean-square error) with the new method are in agreement with those obtained using a modal fitting of the surface, for sampling densities higher than 40 x 40 elements. The method competes in flexibility, simplicity, and computing times with standard methods for surface fitting and ray tracing. PMID:19593339

  18. Paraxial ray-tracing approach for the simulation of ultrasonic inspection of welds

    SciTech Connect

    Gardahaut, Audrey; Jezzine, Karim; Cassereau, Didier

    2014-02-18

    On-site inspection of bimetallic or austenitic welds can be very difficult to interpret owing to their internal structures. Skewing and splitting of the ultrasonic beam may occur due to the anisotropic and inhomogeneous properties of the welding material. In this paper, we present a ray-based method to simulate the propagation of ultrasonic waves in such structures. The formalism is based on dynamic ray tracing system in Cartesian coordinates along a reference ray. Standard ray tracing consists in the solution of a system of linear ordinary differential equations of the first order and is used to determine the trajectory of the ray. Likewise, dynamic ray tracing (DRT) also called paraxial ray tracing consists in the solution of an additional system of linear ordinary differential equations along the ray allowing paraxial quantities to be computed. It is used to evaluate the geometrical spreading and amplitude along the ray and in its vicinity. DRT is applied on a smooth representation of the elastic properties of the weld obtained thanks to an image processing technique applied on a macrograph of the weld. Simulation results are presented and compared to finite elements and experimental results.

  19. Paraxial ray-tracing approach for the simulation of ultrasonic inspection of welds

    NASA Astrophysics Data System (ADS)

    Gardahaut, Audrey; Jezzine, Karim; Cassereau, Didier

    2014-02-01

    On-site inspection of bimetallic or austenitic welds can be very difficult to interpret owing to their internal structures. Skewing and splitting of the ultrasonic beam may occur due to the anisotropic and inhomogeneous properties of the welding material. In this paper, we present a ray-based method to simulate the propagation of ultrasonic waves in such structures. The formalism is based on dynamic ray tracing system in Cartesian coordinates along a reference ray. Standard ray tracing consists in the solution of a system of linear ordinary differential equations of the first order and is used to determine the trajectory of the ray. Likewise, dynamic ray tracing (DRT) also called paraxial ray tracing consists in the solution of an additional system of linear ordinary differential equations along the ray allowing paraxial quantities to be computed. It is used to evaluate the geometrical spreading and amplitude along the ray and in its vicinity. DRT is applied on a smooth representation of the elastic properties of the weld obtained thanks to an image processing technique applied on a macrograph of the weld. Simulation results are presented and compared to finite elements and experimental results.

  20. CFSpro: ray tracing for design and optimization of complex fenestration systems using mixed dimensionality approach.

    PubMed

    Kostro, André; Geiger, Mario; Scartezzini, Jean-Louis; Schüler, Andreas

    2016-07-01

    Advanced optical ray tracing software, CFSpro, was developed for the study and optimization of complex fenestration systems (CFSs). Using an algorithm mixing 2D and 3D approaches, accurate computation of large numbers of rays in extruded geometries can be performed and visualized in real time. A thin film model was included to assess the spectral control provided by coatings. In this paper, the ray tracing model is described and validated. A novel glazing, engineered with this simulation tool, is presented. It combines the functions of daylight provision, glare protection, and seasonal thermal control while conserving a view to the outside at near normal incidence. PMID:27409200

  1. Ray tracing a three-dimensional scene using a hierarchical data structure

    DOEpatents

    Wald, Ingo; Boulos, Solomon; Shirley, Peter

    2012-09-04

    Ray tracing a three-dimensional scene made up of geometric primitives that are spatially partitioned into a hierarchical data structure. One example embodiment is a method for ray tracing a three-dimensional scene made up of geometric primitives that are spatially partitioned into a hierarchical data structure. In this example embodiment, the hierarchical data structure includes at least a parent node and a corresponding plurality of child nodes. The method includes a first act of determining that a first active ray in the packet hits the parent node and a second act of descending to each of the plurality of child nodes.

  2. SolTrace: A Ray-Tracing Code for Complex Solar Optical Systems

    SciTech Connect

    Wendelin, Tim; Dobos, Aron; Lewandowski, Allan

    2013-10-01

    SolTrace is an optical simulation tool designed to model optical systems used in concentrating solar power (CSP) applications. The code was first written in early 2003, but has seen significant modifications and changes since its inception, including conversion from a Pascal-based software development platform to C++. SolTrace is unique in that it can model virtually any optical system utilizingthe sun as the source. It has been made available for free and as such is in use worldwide by industry, universities, and research laboratories. The fundamental design of the code is discussed, including enhancements and improvements over the earlier version. Comparisons are made with other optical modeling tools, both non-commercial and commercial in nature. Finally, modeled results are shownfor some typical CSP systems and, in one case, compared to measured optical data.

  3. Signatures of Evolutionary Adaptation in Quantitative Trait Loci Influencing Trace Element Homeostasis in Liver.

    PubMed

    Engelken, Johannes; Espadas, Guadalupe; Mancuso, Francesco M; Bonet, Nuria; Scherr, Anna-Lena; Jímenez-Álvarez, Victoria; Codina-Solà, Marta; Medina-Stacey, Daniel; Spataro, Nino; Stoneking, Mark; Calafell, Francesc; Sabidó, Eduard; Bosch, Elena

    2016-03-01

    Essential trace elements possess vital functions at molecular, cellular, and physiological levels in health and disease, and they are tightly regulated in the human body. In order to assess variability and potential adaptive evolution of trace element homeostasis, we quantified 18 trace elements in 150 liver samples, together with the expression levels of 90 genes and abundances of 40 proteins involved in their homeostasis. Additionally, we genotyped 169 single nucleotide polymorphism (SNPs) in the same sample set. We detected significant associations for 8 protein quantitative trait loci (pQTL), 10 expression quantitative trait loci (eQTLs), and 15 micronutrient quantitative trait loci (nutriQTL). Six of these exceeded the false discovery rate cutoff and were related to essential trace elements: 1) one pQTL for GPX2 (rs10133290); 2) two previously described eQTLs for HFE (rs12346) and SELO (rs4838862) expression; and 3) three nutriQTLs: The pathogenic C282Y mutation at HFE affecting iron (rs1800562), and two SNPs within several clustered metallothionein genes determining selenium concentration (rs1811322 and rs904773). Within the complete set of significant QTLs (which involved 30 SNPs and 20 gene regions), we identified 12 SNPs with extreme patterns of population differentiation (FST values in the top 5% percentile in at least one HapMap population pair) and significant evidence for selective sweeps involving QTLs at GPX1, SELENBP1, GPX3, SLC30A9, and SLC39A8. Overall, this detailed study of various molecular phenotypes illustrates the role of regulatory variants in explaining differences in trace element homeostasis among populations and in the human adaptive response to environmental pressures related to micronutrients. PMID:26582562

  4. Signatures of Evolutionary Adaptation in Quantitative Trait Loci Influencing Trace Element Homeostasis in Liver

    PubMed Central

    Sabidó, Eduard; Bosch, Elena

    2016-01-01

    Essential trace elements possess vital functions at molecular, cellular, and physiological levels in health and disease, and they are tightly regulated in the human body. In order to assess variability and potential adaptive evolution of trace element homeostasis, we quantified 18 trace elements in 150 liver samples, together with the expression levels of 90 genes and abundances of 40 proteins involved in their homeostasis. Additionally, we genotyped 169 single nucleotide polymorphism (SNPs) in the same sample set. We detected significant associations for 8 protein quantitative trait loci (pQTL), 10 expression quantitative trait loci (eQTLs), and 15 micronutrient quantitative trait loci (nutriQTL). Six of these exceeded the false discovery rate cutoff and were related to essential trace elements: 1) one pQTL for GPX2 (rs10133290); 2) two previously described eQTLs for HFE (rs12346) and SELO (rs4838862) expression; and 3) three nutriQTLs: The pathogenic C282Y mutation at HFE affecting iron (rs1800562), and two SNPs within several clustered metallothionein genes determining selenium concentration (rs1811322 and rs904773). Within the complete set of significant QTLs (which involved 30 SNPs and 20 gene regions), we identified 12 SNPs with extreme patterns of population differentiation (FST values in the top 5% percentile in at least one HapMap population pair) and significant evidence for selective sweeps involving QTLs at GPX1, SELENBP1, GPX3, SLC30A9, and SLC39A8. Overall, this detailed study of various molecular phenotypes illustrates the role of regulatory variants in explaining differences in trace element homeostasis among populations and in the human adaptive response to environmental pressures related to micronutrients. PMID:26582562

  5. Can We Trace "Arbitrary" Rays to Locate an Image Formed by a Thin Lens?

    ERIC Educational Resources Information Center

    Suppapittayaporn, Decha; Panijpan, Bhinyo; Emarat, Narumon

    2010-01-01

    After learning how to trace the principal rays [Fig. 1(i)] through a thin lens in order to form the image in the conventional way, students sometimes ask whether it is possible to use other rays emanating from the object to form exactly the same image--for example, the two arbitrary rays shown in Fig. 1(ii). The answer is a definite yes, and this…

  6. Ray-tracing method for creeping waves on arbitrarily shaped nonuniform rational B-splines surfaces.

    PubMed

    Chen, Xi; He, Si-Yuan; Yu, Ding-Feng; Yin, Hong-Cheng; Hu, Wei-Dong; Zhu, Guo-Qiang

    2013-04-01

    An accurate creeping ray-tracing algorithm is presented in this paper to determine the tracks of creeping waves (or creeping rays) on arbitrarily shaped free-form parametric surfaces [nonuniform rational B-splines (NURBS) surfaces]. The main challenge in calculating the surface diffracted fields on NURBS surfaces is due to the difficulty in determining the geodesic paths along which the creeping rays propagate. On one single parametric surface patch, the geodesic paths need to be computed by solving the geodesic equations numerically. Furthermore, realistic objects are generally modeled as the union of several connected NURBS patches. Due to the discontinuity of the parameter between the patches, it is more complicated to compute geodesic paths on several connected patches than on one single patch. Thus, a creeping ray-tracing algorithm is presented in this paper to compute the geodesic paths of creeping rays on the complex objects that are modeled as the combination of several NURBS surface patches. In the algorithm, the creeping ray tracing on each surface patch is performed by solving the geodesic equations with a Runge-Kutta method. When the creeping ray propagates from one patch to another, a transition method is developed to handle the transition of the creeping ray tracing across the border between the patches. This creeping ray-tracing algorithm can meet practical requirements because it can be applied to the objects with complex shapes. The algorithm can also extend the applicability of NURBS for electromagnetic and optical applications. The validity and usefulness of the algorithm can be verified from the numerical results. PMID:23595326

  7. Real-time simulation of ultrasound refraction phenomena using ray-trace based wavefront construction method.

    PubMed

    Szostek, Kamil; Piórkowski, Adam

    2016-10-01

    Ultrasound (US) imaging is one of the most popular techniques used in clinical diagnosis, mainly due to lack of adverse effects on patients and the simplicity of US equipment. However, the characteristics of the medium cause US imaging to imprecisely reconstruct examined tissues. The artifacts are the results of wave phenomena, i.e. diffraction or refraction, and should be recognized during examination to avoid misinterpretation of an US image. Currently, US training is based on teaching materials and simulators and ultrasound simulation has become an active research area in medical computer science. Many US simulators are limited by the complexity of the wave phenomena, leading to intensive sophisticated computation that makes it difficult for systems to operate in real time. To achieve the required frame rate, the vast majority of simulators reduce the problem of wave diffraction and refraction. The following paper proposes a solution for an ultrasound simulator based on methods known in geophysics. To improve simulation quality, a wavefront construction method was adapted which takes into account the refraction phenomena. This technique uses ray tracing and velocity averaging to construct wavefronts in the simulation. Instead of a geological medium, real CT scans are applied. This approach can produce more realistic projections of pathological findings and is also capable of providing real-time simulation. PMID:27586490

  8. Optimizing detector geometry for trace element mapping by X-ray fluorescence

    SciTech Connect

    Sun, Yue; Gleber, Sophie -Charlotte; Jacobsen, Chris; Kirz, Janos; Vogt, Stefan

    2015-01-01

    We report that trace metals play critical roles in a variety of systems, ranging from cells to photovoltaics. X-Ray Fluorescence (XRF) microscopy using X-ray excitation provides one of the highest sensitivities available for imaging the distribution of trace metals at sub-100 nm resolution. With the growing availability and increasing performance of synchrotron light source based instruments and X-ray nanofocusing optics, and with improvements in energy-dispersive XRF detectors, what are the factors that limit trace element detectability? To address this question, we describe an analytical model for the total signal incident on XRF detectors with various geometries, including the spectral response of energy dispersive detectors. This model agrees well with experimentally recorded X-ray fluorescence spectra, and involves much shorter calculation times than with Monte Carlo simulations. With such a model, one can estimate the signal when a trace element is illuminated with an X-ray beam, and when just the surrounding non-fluorescent material is illuminated. From this signal difference, a contrast parameter can be calculated and this can in turn be used to calculate the signal-to-noise ratio (S/N) for detecting a certain elemental concentration. We apply this model to the detection of trace amounts of zinc in biological materials, and to the detection of small quantities of arsenic in semiconductors. In conclusion, we conclude that increased detector collection solid angle is (nearly) always advantageous even when considering the scattered signal. However, given the choice between a smaller detector at 90° to the beam versus a larger detector at 180° (in a backscatter-like geometry), the 90° detector is better for trace element detection in thick samples, while the larger detector in 180° geometry is better suited to trace element detection in thin samples.

  9. Optimizing detector geometry for trace element mapping by X-ray fluorescence

    DOE PAGESBeta

    Sun, Yue; Gleber, Sophie -Charlotte; Jacobsen, Chris; Kirz, Janos; Vogt, Stefan

    2015-01-01

    We report that trace metals play critical roles in a variety of systems, ranging from cells to photovoltaics. X-Ray Fluorescence (XRF) microscopy using X-ray excitation provides one of the highest sensitivities available for imaging the distribution of trace metals at sub-100 nm resolution. With the growing availability and increasing performance of synchrotron light source based instruments and X-ray nanofocusing optics, and with improvements in energy-dispersive XRF detectors, what are the factors that limit trace element detectability? To address this question, we describe an analytical model for the total signal incident on XRF detectors with various geometries, including the spectral responsemore » of energy dispersive detectors. This model agrees well with experimentally recorded X-ray fluorescence spectra, and involves much shorter calculation times than with Monte Carlo simulations. With such a model, one can estimate the signal when a trace element is illuminated with an X-ray beam, and when just the surrounding non-fluorescent material is illuminated. From this signal difference, a contrast parameter can be calculated and this can in turn be used to calculate the signal-to-noise ratio (S/N) for detecting a certain elemental concentration. We apply this model to the detection of trace amounts of zinc in biological materials, and to the detection of small quantities of arsenic in semiconductors. In conclusion, we conclude that increased detector collection solid angle is (nearly) always advantageous even when considering the scattered signal. However, given the choice between a smaller detector at 90° to the beam versus a larger detector at 180° (in a backscatter-like geometry), the 90° detector is better for trace element detection in thick samples, while the larger detector in 180° geometry is better suited to trace element detection in thin samples.« less

  10. Optimizing detector geometry for trace element mapping by X-ray fluorescence

    PubMed Central

    Sun, Yue; Gleber, Sophie-Charlotte; Jacobsen, Chris; Kirz, Janos; Vogt, Stefan

    2016-01-01

    Trace metals play critical roles in a variety of systems, ranging from cells to photovoltaics. X-Ray Fluorescence (XRF) microscopy using X-ray excitation provides one of the highest sensitivities available for imaging the distribution of trace metals at sub-100 nm resolution. With the growing availability and increasing performance of synchrotron light source based instruments and X-ray nanofocusing optics, and with improvements in energy-dispersive XRF detectors, what are the factors that limit trace element detectability? To address this question, we describe an analytical model for the total signal incident on XRF detectors with various geometries, including the spectral response of energy dispersive detectors. This model agrees well with experimentally recorded X-ray fluorescence spectra, and involves much shorter calculation times than with Monte Carlo simulations. With such a model, one can estimate the signal when a trace element is illuminated with an X-ray beam, and when just the surrounding non-fluorescent material is illuminated. From this signal difference, a contrast parameter can be calculated and this can in turn be used to calculate the signal-to-noise ratio (S/N) for detecting a certain elemental concentration. We apply this model to the detection of trace amounts of zinc in biological materials, and to the detection of small quantities of arsenic in semiconductors. We conclude that increased detector collection solid angle is (nearly) always advantageous even when considering the scattered signal. However, given the choice between a smaller detector at 90° to the beam versus a larger detector at 180° (in a backscatter-like geometry), the 90° detector is better for trace element detection in thick samples, while the larger detector in 180° geometry is better suited to trace element detection in thin samples. PMID:25600825

  11. A data distributed parallel algorithm for ray-traced volume rendering

    NASA Technical Reports Server (NTRS)

    Ma, Kwan-Liu; Painter, James S.; Hansen, Charles D.; Krogh, Michael F.

    1993-01-01

    This paper presents a divide-and-conquer ray-traced volume rendering algorithm and a parallel image compositing method, along with their implementation and performance on the Connection Machine CM-5, and networked workstations. This algorithm distributes both the data and the computations to individual processing units to achieve fast, high-quality rendering of high-resolution data. The volume data, once distributed, is left intact. The processing nodes perform local ray tracing of their subvolume concurrently. No communication between processing units is needed during this locally ray-tracing process. A subimage is generated by each processing unit and the final image is obtained by compositing subimages in the proper order, which can be determined a priori. Test results on both the CM-5 and a group of networked workstations demonstrate the practicality of our rendering algorithm and compositing method.

  12. Long gamma-ray bursts trace the star formation history

    SciTech Connect

    Dado, Shlomo; Dar, Arnon

    2014-04-10

    We show that if the broad-line supernova explosions of Type Ic (SNeIc) produce the bulk of the observed long duration gamma-ray bursts (LGRBs), including high- and low-luminosity LGRBs and X-ray flashes, and if the LGRBs have the geometry assumed in the cannonball model of LGRBs, then their rate, measured by Swift, and their redshift distribution are consistent with the star formation rate (SFR) over the entire range of redshifts where the SFR has been measured with sufficient accuracy.

  13. Ray Tracing Through Non-Rotationally Symmetrical Systems With A Desktop Computer

    NASA Astrophysics Data System (ADS)

    Mackay, R. M.; Busse lle, F. J.

    1986-10-01

    A general ray-trace program has been developed for use on a desktop computer which traces finite rays through any non-rotationally symmetrical system. In particular any combination of decentred, tilted and rotated surface has been considered. Surface types such as Conic sections with and without Aspherics, Toric surfaces, surfaces of S and T Cylindrical sections, and Axicons, may be ray-traced. Each surface is defined in terms of a local rectangular co-ordinate system and has a particular aperture shape attributed to it. Aperture shapes may be defined as circular, elliptical, rectangular or quadrilateral. Also the centre of any aperture shape may be displaced from its local coordinate origin to facilitate the tracing of off-axis paraboloids. Before transferring to the next surface, the local coordinates are referred back to an initial reference coordinate system. Finally a means of assessing aberrations has been included. The main task here was to get a mathematical model of a non-rotationally symmetrical finite ray-trace running on an inexpensive desk top computer. The program was written for the BBC MICRO in order to investigate devices such as scanning systems for modern Thermal Imagers etc.

  14. Magnetospheric Whistler Mode Ray Tracing with the Inclusion of Finite Electron and Ion Temperature

    NASA Astrophysics Data System (ADS)

    Maxworth, A. S.; Golkowski, M.

    2015-12-01

    Ray tracing is an important technique for the study of whistler mode wave propagation in the Earth's magnetosphere. In numerical ray tracing the trajectory of a wave packet is calculated at each point in space by solving the Haselgrove equations, assuming a smooth, loss-less medium with no mode coupling. Previous work on ray tracing has assumed a cold plasma environment with negligible electron and ion temperatures. In this work we present magnetospheric whistler mode wave ray tracing results with the inclusion of finite ion and electron temperature. The inclusion of finite temperature effects makes the fourth order dispersion relation become sixth order. We compare our results with the work done by previous researchers for cold plasma environments, using two near earth space models (NGO and GCPM). Inclusion of finite temperature closes the otherwise open refractive index surface near the lower hybrid resonance frequency and affects the magnetospheric reflection of whistler waves. We also asses the main changes in the ray trajectory and implications for cyclotron resonance wave particle interactions including energetic particle precipitation.

  15. Automatic creation of object hierarchies for ray tracing

    NASA Technical Reports Server (NTRS)

    Goldsmith, Jeffrey; Salmon, John

    1987-01-01

    Various methods for evaluating generated trees are proposed. The use of the hierarchical extent method of Rubin and Whitted (1980) to find the objects that will be hit by a ray is examined. This method employs tree searching; the construction of a tree of bounding volumes in order to determine the number of objects that will be hit by a ray is discussed. A tree generation algorithm, which uses a heuristic tree search strategy, is described. The effects of shuffling and sorting on the input data are investigated. The cost of inserting an object into the hierarchy during the construction of a tree algorithm is estimated. The steps involved in estimating the number of intersection calculations are presented.

  16. A boundary integral formalism for stochastic ray tracing in billiards

    SciTech Connect

    Chappell, David J.; Tanner, Gregor

    2014-12-15

    Determining the flow of rays or non-interacting particles driven by a force or velocity field is fundamental to modelling many physical processes. These include particle flows arising in fluid mechanics and ray flows arising in the geometrical optics limit of linear wave equations. In many practical applications, the driving field is not known exactly and the dynamics are determined only up to a degree of uncertainty. This paper presents a boundary integral framework for propagating flows including uncertainties, which is shown to systematically interpolate between a deterministic and a completely random description of the trajectory propagation. A simple but efficient discretisation approach is applied to model uncertain billiard dynamics in an integrable rectangular domain.

  17. Odyssey: Ray tracing and radiative transfer in Kerr spacetime

    NASA Astrophysics Data System (ADS)

    Pu, Hung-Yi; Yun, Kiyun; Younsi, Ziri; Yoon, Suk-Jin

    2016-01-01

    Odyssey is a GPU-based General Relativistic Radiative Transfer (GRRT) code for computing images and/or spectra in Kerr metric describing the spacetime around a rotating black hole. Odyssey is implemented in CUDA C/C++. For flexibility, the namespace structure in C++ is used for different tasks; the two default tasks presented in the source code are the redshift of a Keplerian disk and the image of a Keplerian rotating shell at 340GHz. Odyssey_Edu, an educational software package for visualizing the ray trajectories in the Kerr spacetime that uses Odyssey, is also available.

  18. An Energy Conservative Ray-Tracing Method With a Time Interpolation of the Force Field

    SciTech Connect

    Yao, Jin

    2015-02-10

    A new algorithm that constructs a continuous force field interpolated in time is proposed for resolving existing difficulties in numerical methods for ray-tracing. This new method has improved accuracy, but with the same degree of algebraic complexity compared to Kaisers method.

  19. Comparing TID simulations using 3-D ray tracing and mirror reflection

    NASA Astrophysics Data System (ADS)

    Huang, X.; Reinisch, B. W.; Sales, G. S.; Paznukhov, V. V.; Galkin, I. A.

    2016-04-01

    Measuring the time variations of Doppler frequencies and angles of arrival (AoA) of ionospherically reflected HF waves has been proposed as a means of detecting the occurrence of traveling ionospheric disturbances (TIDs). Simulations are made using ray tracing through the International Reference Ionosphere (IRI) electron density model in an effort to reproduce measured signatures. The TID is represented by a wavelike perturbation of the 3-D electron density traveling horizontally in the ionosphere with an amplitude that varies sinusoidally with time. By judiciously selecting the TID parameters the ray tracing simulation reproduces the observed Doppler frequencies and AoAs. Ray tracing in a 3-D realistic ionosphere is, however, excessively time consuming considering the involved homing procedures. It is shown that a carefully selected reflecting corrugated mirror can reproduce the time variations of the AoA and Doppler frequency. The results from the ray tracing through the IRI model ionosphere and the mirror model reflections are compared to assess the applicability of the mirror-reflection model.

  20. GPU-based ray tracing algorithm for high-speed propagation prediction in typical indoor environments

    NASA Astrophysics Data System (ADS)

    Guo, Lixin; Guan, Xiaowei; Liu, Zhongyu

    2015-10-01

    A fast 3-D ray tracing propagation prediction model based on virtual source tree is presented in this paper, whose theoretical foundations are geometrical optics(GO) and the uniform theory of diffraction(UTD). In terms of typical single room indoor scene, taking the geometrical and electromagnetic information into account, some acceleration techniques are adopted to raise the efficiency of the ray tracing algorithm. The simulation results indicate that the runtime of the ray tracing algorithm will sharply increase when the number of the objects in the single room is large enough. Therefore, GPU acceleration technology is used to solve that problem. As is known to all, GPU is good at calculation operation rather than logical judgment, so that tens of thousands of threads in CUDA programs are able to calculate at the same time, in order to achieve massively parallel acceleration. Finally, a typical single room with several objects is simulated by using the serial ray tracing algorithm and the parallel one respectively. It can be found easily from the results that compared with the serial algorithm, the GPU-based one can achieve greater efficiency.

  1. A General Relativistic Ray-tracing Method for Estimating the Energy and Momentum Deposition by Neutrino Pair Annihilation in Collapsars

    NASA Astrophysics Data System (ADS)

    Harikae, Seiji; Kotake, Kei; Takiwaki, Tomoya; Sekiguchi, Yu-ichiro

    2010-09-01

    Bearing in mind the application to the collapsar models of gamma-ray bursts (GRBs), we develop a numerical scheme and code for estimating the deposition of energy and momentum due to the neutrino pair annihilation (ν + {\\bar{ν}} → e^{-} + e^{+}) in the vicinity of an accretion tori around a Kerr black hole. Our code is designed to solve the general relativistic (GR) neutrino transfer by a ray-tracing method. To solve the collisional Boltzmann equation in curved spacetime, we numerically integrate the so-called rendering equation along the null geodesics. We employ the Fehlberg (4,5) adaptive integrator in the Runge-Kutta method to perform the numerical integration accurately. For the neutrino opacity, the charged-current β-processes, which are dominant in the vicinity of the accretion tori, are taken into account. The numerical accuracy of the developed code is certified by several tests in which we show comparisons with the corresponding analytical solutions. In order to solve the energy-dependent ray-tracing transport, we propose that an adaptive-mesh-refinement approach, which we take for the two radiation angles (θ, phi) and the neutrino energy, is useful in reducing the computational cost significantly. Based on the hydrodynamical data in our collapsar simulation, we estimate the annihilation rates in a post-processing manner. Increasing the Kerr parameter from 0 to 1, it is found that the GR effect can increase the local energy deposition rate by about one order of magnitude, and the net energy deposition rate by several tens of percent. After the accretion disk settles into a stationary state (typically later than ~9 s from the onset of gravitational collapse), we point out that the neutrino-heating timescale in the vicinity of the polar funnel region can be shorter than the dynamical timescale. Our results suggest that the neutrino pair annihilation is potentially as important as the conventional magnetohydrodynamic mechanism for igniting the GRB

  2. Tracing Chromospheric Evaporation in Radio and Soft X-rays

    NASA Technical Reports Server (NTRS)

    Aschwanden, Markus J.

    1997-01-01

    There are three publications in refereed journals and several presentations at scientific conferences resulted from this work, over a period of 6 months during 1995/1996. In the first paper, the discovery of the chromospheric evaporation process at radio wavelengths is described. In the second paper, the radio detection is used to quantify electron densities in the upflowing heated plasma in flare loops, which is then compared with independent other density measurements from soft X-rays, or the plasma frequency of electron beams originating in the acceleration region. In the third paper, the diagnostic results of the chromospheric evaporation process are embedded into a broader picture of a standard flare scenario. Abstracts of these three papers are attached.

  3. A comparison of three different ray trace programs for x-ray and infrared synchrotron beamline designs

    SciTech Connect

    Irick, S.C.; Jung, C.R.

    1997-07-01

    There are a number of ray trace programs currently used for the design of synchrotron beamlines. While several of these programs have been written and used mostly within the programmer`s institution, many have also been available to the general public. This paper discusses three such programs. One is a commercial product oriented for the general optical designer (not specifically for synchrotron beamlines). One is designed for synchrotron beamlines and is free with restricted availability. Finally, one is designed for synchrotron beamlines and is used primarily in one institution. The wealth of information from general optical materials and components catalogs is readily available in the commercial program for general optical designs. This makes the design of an infrared beamline easier from the standpoint of component selection. However, this program is not easily configured for synchrotron beamline designs, particularly for a bending magnet source. The synchrotron ray trace programs offer a variety of sources, but generally are not as easy to use from the standpoint of the user interface. This paper shows ray traces of the same beamline Optikwerks, SHADOW, and RAY, and compares the results.

  4. Ray tracing in a finite-element domain using nodal basis functions.

    PubMed

    Schrader, Karl N; Subia, Samuel R; Myre, John W; Summers, Kenneth L

    2014-08-20

    A method is presented for tracing rays through a medium discretized as finite-element volumes. The ray-trajectory equations are cast into the local element coordinate frame, and the full finite-element interpolation is used to determine instantaneous index gradient for the ray-path integral equation. The finite-element methodology is also used to interpolate local surface deformations and the surface normal vector for computing the refraction angle when launching rays into the volume, and again when rays exit the medium. The procedure is applied to a finite-element model of an optic with a severe refractive-index gradient, and the results are compared to the closed-form gradient ray-path integral approach. PMID:25321137

  5. Reverse Monte Carlo ray-tracing for radiative heat transfer in combustion systems

    NASA Astrophysics Data System (ADS)

    Sun, Xiaojing

    Radiative heat transfer is a dominant heat transfer phenomenon in high temperature systems. With the rapid development of massive supercomputers, the Monte-Carlo ray tracing (MCRT) method starts to see its applications in combustion systems. This research is to find out if Monte-Carlo ray tracing can offer more accurate and efficient calculations than the discrete ordinates method (DOM). Monte-Carlo ray tracing method is a statistical method that traces the history of a bundle of rays. It is known as solving radiative heat transfer with almost no approximation. It can handle nonisotropic scattering and nongray gas mixtures with relative ease compared to conventional methods, such as DOM and spherical harmonics method, etc. There are two schemes in Monte-Carlo ray tracing method: forward and backward/reverse. Case studies and the governing equations demonstrate the advantages of reverse Monte-Carlo ray tracing (RMCRT) method. The RMCRT can be easily implemented for domain decomposition parallelism. In this dissertation, different efficiency improvements techniques for RMCRT are introduced and implemented. They are the random number generator, stratified sampling, ray-surface intersection calculation, Russian roulette, and important sampling. There are two major modules in solving the radiative heat transfer problems: the RMCRT RTE solver and the optical property models. RMCRT is first fully verified in gray, scattering, absorbing and emitting media with black/nonblack, diffuse/nondiffuse bounded surface problems. Sensitivity analysis is carried out with regard to the ray numbers, the mesh resolutions of the computational domain, optical thickness of the media and effects of variance reduction techniques (stratified sampling, Russian roulette). Results are compared with either analytical solutions or benchmark results. The efficiency (the product of error and computation time) of RMCRT has been compared to DOM and suggest great potential for RMCRT's application

  6. Effective algorithm for ray-tracing simulations of lobster eye and similar reflective optical systems

    NASA Astrophysics Data System (ADS)

    Tichý, Vladimír; Hudec, René; Němcová, Šárka

    2016-06-01

    The algorithm presented is intended mainly for lobster eye optics. This type of optics (and some similar types) allows for a simplification of the classical ray-tracing procedure that requires great many rays to simulate. The method presented performs the simulation of a only few rays; therefore it is extremely effective. Moreover, to simplify the equations, a specific mathematical formalism is used. Only a few simple equations are used, therefore the program code can be simple as well. The paper also outlines how to apply the method to some other reflective optical systems.

  7. Effective algorithm for ray-tracing simulations of lobster eye and similar reflective optical systems

    NASA Astrophysics Data System (ADS)

    Tichý, Vladimír; Hudec, René; Němcová, Šárka

    2016-03-01

    The algorithm presented is intended mainly for lobster eye optics. This type of optics (and some similar types) allows for a simplification of the classical ray-tracing procedure that requires great many rays to simulate. The method presented performs the simulation of a only few rays; therefore it is extremely effective. Moreover, to simplify the equations, a specific mathematical formalism is used. Only a few simple equations are used, therefore the program code can be simple as well. The paper also outlines how to apply the method to some other reflective optical systems.

  8. Solar Proton Transport Within an ICRU Sphere Surrounded by a Complex Shield: Ray-trace Geometry

    NASA Technical Reports Server (NTRS)

    Slaba, Tony C.; Wilson, John W.; Badavi, Francis F.; Reddell, Brandon D.; Bahadori, Amir A.

    2015-01-01

    A computationally efficient 3DHZETRN code with enhanced neutron and light ion (Z is less than or equal to 2) propagation was recently developed for complex, inhomogeneous shield geometry described by combinatorial objects. Comparisons were made between 3DHZETRN results and Monte Carlo (MC) simulations at locations within the combinatorial geometry, and it was shown that 3DHZETRN agrees with the MC codes to the extent they agree with each other. In the present report, the 3DHZETRN code is extended to enable analysis in ray-trace geometry. This latest extension enables the code to be used within current engineering design practices utilizing fully detailed vehicle and habitat geometries. Through convergence testing, it is shown that fidelity in an actual shield geometry can be maintained in the discrete ray-trace description by systematically increasing the number of discrete rays used. It is also shown that this fidelity is carried into transport procedures and resulting exposure quantities without sacrificing computational efficiency.

  9. Exact ray tracing formulas based on a nontrigonometric alternative to Snell's law.

    PubMed

    Elagha, Hassan A

    2012-12-01

    In this work, Fermat's principle is applied to derive a simple exact formula for refraction (reflection) in terms of the lengths of the incident and refracted rays. This formula is a nontrigonometric alternative to Snell's law and is general for all optical surfaces. It is used to derive the paraxial optics equations in a more simple and direct way than that often used in the literature. It's also applied to derive a new single, exact ray tracing formula for the nonparaxial refraction (reflection) at a single optical surface. The obtained formulas are used to develop a simple ray tracing procedure for meridional refraction through systems of spherical surfaces without the need to use any form of Snell's law. Numerical examples are provided and discussed. PMID:23455919

  10. Runge-Kutta ray tracing technique for solving radiative heat transfer in a two-dimensional graded-index medium

    NASA Astrophysics Data System (ADS)

    Huang, Yong; Shi, Guo-Dong; Zhu, Ke-Yong

    2016-06-01

    This paper adopts the Runge-Kutta ray tracing method to obtain the ray-trajectory numerical solution in a two-dimensional gradient index medium. The emitting, absorbing and scattering processes are simulated by the Monte Carlo method. The temperature field and ray trajectory in the medium are obtained by the three methods, the Runge-Kutta ray tracing method, the ray tracing method with the cell model and the discrete curved ray tracing method with the linear refractive index cell model. Comparing the results of the three methods, it is found that the results by the Monte Carlo Runge-Kutta ray tracing method are of the highest accuracy. To improve the computational speed, the variable step-size Runge-Kutta ray tracing method is proposed, and the maximum relative error between the temperature field in the nonscattering medium by this method and the benchmark solution is less than 0.5%. The results also suggest that the Runge-Kutta ray tracing method would make the radiative transfer solution in the three-dimensional graded index media much easier.

  11. Trace metal content in aspirin and women's cosmetics via proton induced x-ray emission (PIXE)

    SciTech Connect

    Hichwa, B.P.; Pun, D.D.; Wang, D.

    1981-04-01

    A multielemental analysis to determine the trace metal content of generic and name-brand aspirins and name-brand lipsticks was done via proton induced x-ray (PIXE) measurements. The Hope College PIXE system is described as well as the target preparation methods. The trace metal content of twelve brands of aspirin and aspirin substitutes and fourteen brands of lipstick are reported. Detection limits for most elements are in the range of 100 parts per billion (ppb) to 10 parts per million (ppm).

  12. Modeling of micro cat's eye retroreflectors using a matrix-based three-dimensional ray tracing technique.

    PubMed

    Yang, Bing-jun; Chao, Keng-hsing; Tsai, Jui-che

    2012-09-01

    In this paper we develop a three-dimensional (3D) ray tracing tool based on the ABCD ray transfer matrices. With symmetric optical components and under paraxial approximation, two sets of 2×2 ABCD matrices, each for a two-dimensional subspace, can be used to describe the 3D ray propagation completely. Compared to commercial ray-tracing software packages, our tool requires no tedious drawing, and the results for various conditions, such as different device dimensions and incident angles, can be easily obtained by simply changing the parameter values used for the calculation. We have employed this matrix-based 3D ray tracing tool to model cat's eye retroreflectors. The cat's eye performance, including the retroreflection efficiency, acceptance angle (i.e., field of view), and beam divergence and deviation, is fully studied. The application of this 3D ray tracing technique can be further extended to other optical components. PMID:22945148

  13. Ionospheric differential error determination using ray tracing for a short baseline

    NASA Astrophysics Data System (ADS)

    Abdullah, M.; Strangeways, H. J.; Zulkifli, S. S. N.

    2010-11-01

    Since the United States government discontinued Selective Availability (SA) on 1 May 2000, ionospheric effects have been responsible for the largest errors in GPS systems. The standard Differential GPS (DGPS) method is incapable of completely eliminating the ionospheric error. This paper describes a new approach to determine the differential ionospheric error between geographically distributed receiver stations. The ray paths of GPS signals were simulated using a modified Jones 3D ray tracing programme that includes the effect of the geomagnetic field. A Nelder-Mead optimisation algorithm was embedded in the program to precisely determine the satellite-to-station path. A realistic ionospheric model is essential for accurate ray tracing results and for estimates of differential error that are accurate on sub-centimetre scales. Here, the ionospheric model used in the ray tracing programme was developed by fitting realistic ionosphere profiles with a number of exponential functions. Results were compared to the theoretical approach. Results show that the differential delay is about 1-5 cm at low elevation angles for a short baseline of 10 km, as reported in other literature. This delay is often neglected in DGPS application. The differential delay also shows a pattern similar to that predicted by the Klobuchar model. The method proposed here can be used to improve future GPS applications.

  14. Nonlinear teleseismic tomography at Long Valley caldera, using three-dimensional minimum travel time ray tracing

    SciTech Connect

    Weiland, C.M.; Steck, L.K.; Dawson, P.B.

    1995-10-10

    The authors explore the impact of three-dimensional minimum travel time ray tracing on nonlinear teleseismic inversion. This problem has particular significance when trying to image strongly contrasting low-velocity bodies, such as magma chambers, because strongly refracted/and/or diffracted rays may precede the direct P wave arrival traditionally used in straight-ray seismic tomography. They use a simplex-based ray tracer to compute the three-dimensional, minimum travel time ray paths and employ an interative technique to cope with nonlinearity. Results from synthetic data show that their algorithm results in better model reconstructions compared with traditional straight-ray inversions. The authors reexamine the teleseismic data collected at Long Valley caldera by the U.S. Geological Survey. The most prominent feature of their result is a 25-30% low-velocity zone centered at 11.5 km depth beneath the northwestern quandrant of the caldera. Beneath this at a depth of 24.5 km is a more diffuse 15% low-velocity zone. In general, the low velocities tend to deepen to the south and east. The authors interpret the shallow feature to be the residual Long Valley caldera magma chamber, while the deeper feature may represent basaltic magmas ponded in the midcrust. The deeper position of the prominent low-velocity region in comparison to earlier tomographic images is a result of using three-dimensional rays rather than straight rays in the ray tracing. The magnitude of the low-velocity anomaly is a factor of {approximately}3 times larger than earlier models from linear arrival time inversions and is consistent with models based on observations of ray bending at sites within the caldera. These results imply the presence of anywhere from 7 to 100% partial melt beneath the caldera. 40 refs., 1 fig., 1 tab.

  15. Improvements of the Ray-Tracing Based Method Calculating Hypocentral Loci for Earthquake Location

    NASA Astrophysics Data System (ADS)

    Zhao, A. H.

    2014-12-01

    Hypocentral loci are very useful to reliable and visual earthquake location. However, they can hardly be analytically expressed when the velocity model is complex. One of methods numerically calculating them is based on a minimum traveltime tree algorithm for tracing rays: a focal locus is represented in terms of ray paths in its residual field from the minimum point (namely initial point) to low residual points (referred as reference points of the focal locus). The method has no restrictions on the complexity of the velocity model but still lacks the ability of correctly dealing with multi-segment loci. Additionally, it is rather laborious to set calculation parameters for obtaining loci with satisfying completeness and fineness. In this study, we improve the ray-tracing based numerical method to overcome its advantages. (1) Reference points of a hypocentral locus are selected from nodes of the model cells that it goes through, by means of a so-called peeling method. (2) The calculation domain of a hypocentral locus is defined as such a low residual area that its connected regions each include one segment of the locus and hence all the focal locus segments are respectively calculated with the minimum traveltime tree algorithm for tracing rays by repeatedly assigning the minimum residual reference point among those that have not been traced as an initial point. (3) Short ray paths without branching are removed to make the calculated locus finer. Numerical tests show that the improved method becomes capable of efficiently calculating complete and fine hypocentral loci of earthquakes in a complex model.

  16. TIM, a ray-tracing program for METATOY research and its dissemination

    NASA Astrophysics Data System (ADS)

    Lambert, Dean; Hamilton, Alasdair C.; Constable, George; Snehanshu, Harsh; Talati, Sharvil; Courtial, Johannes

    2012-03-01

    TIM (The Interactive METATOY) is a ray-tracing program specifically tailored towards our research in METATOYs, which are optical components that appear to be able to create wave-optically forbidden light-ray fields. For this reason, TIM possesses features not found in other ray-tracing programs. TIM can either be used interactively or by modifying the openly available source code; in both cases, it can easily be run as an applet embedded in a web page. Here we describe the basic structure of TIM's source code and how to extend it, and we give examples of how we have used TIM in our own research. Program summaryProgram title: TIM Catalogue identifier: AEKY_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEKY_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: GNU General Public License No. of lines in distributed program, including test data, etc.: 124 478 No. of bytes in distributed program, including test data, etc.: 4 120 052 Distribution format: tar.gz Programming language: Java Computer: Any computer capable of running the Java Virtual Machine (JVM) 1.6 Operating system: Any; developed under Mac OS X Version 10.6 RAM: Typically 145 MB (interactive version running under Mac OS X Version 10.6) Classification: 14, 18 External routines: JAMA [1] (source code included) Nature of problem: Visualisation of scenes that include scene objects that create wave-optically forbidden light-ray fields. Solution method: Ray tracing. Unusual features: Specifically designed to visualise wave-optically forbidden light-ray fields; can visualise ray trajectories; can visualise geometric optic transformations; can create anaglyphs (for viewing with coloured "3D glasses") and random-dot autostereograms of the scene; integrable into web pages. Running time: Problem-dependent; typically seconds for a simple scene.

  17. Skeleton-based tracing of curved fibers from 3D X-ray microtomographic imaging

    NASA Astrophysics Data System (ADS)

    Huang, Xiang; Wen, Donghui; Zhao, Yanwei; Wang, Qinghui; Zhou, Wei; Deng, Daxiang

    A skeleton-based fiber tracing algorithm is described and applied on a specific fibrous material, porous metal fiber sintered sheet (PMFSS), featuring high porosity and curved fibers. The skeleton segments are firstly categorized according to the connectivity of the skeleton paths. Spurious segments like fiber bonds are detected making extensive use of the distance transform (DT) values. Single fibers are then traced and reconstructed by consecutively choosing the connecting skeleton segment pairs that show the most similar orientations and radius. Moreover, to reduce the misconnection due to the tracing orders, a multilevel tracing strategy is proposed. The fibrous network is finally reconstructed by dilating single fibers according to the DT values. Based on the traced single fibers, various morphology information regarding fiber length, radius, orientation, and tortuosity are quantitatively analyzed and compared with our previous results (Wang et al., 2013). Moreover, the number of bonds per fibers are firstly accessed. The methodology described in this paper can be expanded to other fibrous materials with adapted parameters.

  18. Real time adaptive filtering for digital X-ray applications.

    PubMed

    Bockenbach, Olivier; Mangin, Michel; Schuberth, Sebastian

    2006-01-01

    Over the last decade, many methods for adaptively filtering a data stream have been proposed. Those methods have applications in two dimensional imaging as well as in three dimensional image reconstruction. Although the primary objective of this filtering technique is to reduce the noise while avoiding to blur the edges, diagnostic, automated segmentation and surgery show a growing interest in enhancing the features contained in the image flow. Most of the methods proposed so far emerged from thorough studies of the physics of the considered modality and therefore show only a marginal capability to be extended across modalities. Moreover, adaptive filtering belongs to the family of processing intensive algorithms. Existing technology has often driven to simplifications and modality specific optimization to sustain the expected performances. In the specific case of real time digital X-ray as used surgery, the system has to sustain a throughput of 30 frames per second. In this study, we take a generalized approach for adaptive filtering based on multiple oriented filters. Mapping the filtering part to the embedded real time image processing while a user/application defined adaptive recombination of the filter outputs allow to change the smoothing and edge enhancement properties of the filter without changing the oriented filter parameters. We have implemented the filtering on a Cell Broadband Engine processor and the adaptive recombination on an off-the-shelf PC, connected via Gigabit Ethernet. This implementation is capable of filtering images of 5122 pixels at a throughput in excess of 40 frames per second while allowing to change the parameters in real time. PMID:17354937

  19. Combining ray tracing and CFD in the thermal analysis of a parabolic dish tubular cavity receiver

    NASA Astrophysics Data System (ADS)

    Craig, Ken J.; Marsberg, Justin; Meyer, Josua P.

    2016-05-01

    This paper describes the numerical evaluation of a tubular receiver used in a dish Brayton cycle. In previous work considering the use of Computational Fluid Dynamics (CFD) to perform the calculation of the absorbed radiation from the parabolic dish into the cavity as well as the resulting conjugate heat transfer, it was shown that an axi-symmetric model of the dish and receiver absorbing surfaces was useful in reducing the computational cost required for a full 3-D discrete ordinates solution, but concerns remained about its accuracy. To increase the accuracy, the Monte Carlo ray tracer SolTrace is used to perform the calculation of the absorbed radiation profile to be used in the conjugate heat transfer CFD simulation. The paper describes an approach for incorporating a complex geometry like a tubular receiver generated using CFD software into SolTrace. The results illustrate the variation of CFD mesh density that translates into the number of elements in SolTrace as well as the number of rays used in the Monte Carlo approach and their effect on obtaining a resolution-independent solution. The conjugate heat transfer CFD simulation illustrates the effect of applying the SolTrace surface heat flux profile solution as a volumetric heat source to heat up the air inside the tube. Heat losses due to convection and thermal re-radiation are also determined as a function of different tube absorptivities.

  20. Adapting an ant colony metaphor for multi-robot chemical plume tracing.

    PubMed

    Meng, Qing-Hao; Yang, Wei-Xing; Wang, Yang; Li, Fei; Zeng, Ming

    2012-01-01

    We consider chemical plume tracing (CPT) in time-varying airflow environments using multiple mobile robots. The purpose of CPT is to approach a gas source with a previously unknown location in a given area. Therefore, the CPT could be considered as a dynamic optimization problem in continuous domains. The traditional ant colony optimization (ACO) algorithm has been successfully used for combinatorial optimization problems in discrete domains. To adapt the ant colony metaphor to the multi-robot CPT problem, the two-dimension continuous search area is discretized into grids and the virtual pheromone is updated according to both the gas concentration and wind information. To prevent the adapted ACO algorithm from being prematurely trapped in a local optimum, the upwind surge behavior is adopted by the robots with relatively higher gas concentration in order to explore more areas. The spiral surge (SS) algorithm is also examined for comparison. Experimental results using multiple real robots in two indoor natural ventilated airflow environments show that the proposed CPT method performs better than the SS algorithm. The simulation results for large-scale advection-diffusion plume environments show that the proposed method could also work in outdoor meandering plume environments. PMID:22666056

  1. Adapting an Ant Colony Metaphor for Multi-Robot Chemical Plume Tracing

    PubMed Central

    Meng, Qing-Hao; Yang, Wei-Xing; Wang, Yang; Li, Fei; Zeng, Ming

    2012-01-01

    We consider chemical plume tracing (CPT) in time-varying airflow environments using multiple mobile robots. The purpose of CPT is to approach a gas source with a previously unknown location in a given area. Therefore, the CPT could be considered as a dynamic optimization problem in continuous domains. The traditional ant colony optimization (ACO) algorithm has been successfully used for combinatorial optimization problems in discrete domains. To adapt the ant colony metaphor to the multi-robot CPT problem, the two-dimension continuous search area is discretized into grids and the virtual pheromone is updated according to both the gas concentration and wind information. To prevent the adapted ACO algorithm from being prematurely trapped in a local optimum, the upwind surge behavior is adopted by the robots with relatively higher gas concentration in order to explore more areas. The spiral surge (SS) algorithm is also examined for comparison. Experimental results using multiple real robots in two indoor natural ventilated airflow environments show that the proposed CPT method performs better than the SS algorithm. The simulation results for large-scale advection-diffusion plume environments show that the proposed method could also work in outdoor meandering plume environments. PMID:22666056

  2. Analytical calculation of spectral phase of grism pairs by the geometrical ray tracing method

    NASA Astrophysics Data System (ADS)

    Rahimi, L.; Askari, A. A.; Saghafifar, H.

    2016-07-01

    The most optimum operation of a grism pair is practically approachable when an analytical expression of its spectral phase is in hand. In this paper, we have employed the accurate geometrical ray tracing method to calculate the analytical phase shift of a grism pair, at transmission and reflection configurations. As shown by the results, for a great variety of complicated configurations, the spectral phase of a grism pair is in the same form of that of a prism pair. The only exception is when the light enters into and exits from different facets of a reflection grism. The analytical result has been used to calculate the second-order dispersions of several examples of grism pairs in various possible configurations. All results are in complete agreement with those from ray tracing method. The result of this work can be very helpful in the optimal design and application of grism pairs at various configurations.

  3. Nonparaxial geometrical Ronchi test for spherical mirrors: an inverse ray-tracing approach.

    PubMed

    Juarez-Salazar, Rigoberto

    2016-08-01

    A geometrical model based on an inverse ray-tracing approach to describe the Ronchi test for a concave spherical mirror is presented. In contrast to the conventional ray-tracing method, which refers to information unavailable in ronchigrams, the proposed model provides an explicit relation between the available information in the ronchigram and the parameters of the setup (radius of the sphere, position of the source, position and orientation of the observation, and grating planes). This allows for extracting the parameters of interest by a simple fitting procedure, as demonstrated by an application. The derived model exhibits new unexplored potential applications of the Ronchi test, establishing it as a very useful, simple, and universal tool for optical evaluation. PMID:27505380

  4. Three-dimensional ray tracing of the Jovian magnetosphere in the low-frequency range

    NASA Technical Reports Server (NTRS)

    Menietti, J. D.; Green, J. L.; Gulkis, S.; Six, F.

    1984-01-01

    Three-dimensional ray tracing of the Jovian DAM emission has been performed utilizing the O-4 magnetic field model (Acuna and Ness, 1979) and a realistic plasma model. Minimal assumptions about the emission mechanism have been made that include radiation in the right-hand extraordinary mode, propagating nearly perpendicular to the field line at source points located just above the RX cutoff frequency along Io flux tubes. Ray tracing has been performed in the frequency range from 2-35 MHz from successive Io flux tubes separated by ten degrees of central meridian longitude for a full circumference of northern hemisphere sources. The results show unusual complexity in model arc spectra that is displayed in a constant Io phase format with many similarities to the Voyager PRA data. The results suggest much of the variation in observed DAM spectral features is a result of propagation effects rather than emission process differences.

  5. Ray-tracing code TRAVIS for ECR heating, EC current drive and ECE diagnostic

    NASA Astrophysics Data System (ADS)

    Marushchenko, N. B.; Turkin, Y.; Maassberg, H.

    2014-01-01

    A description of the recently developed ray-tracing code TRAVIS is given together with the theoretical background, results of benchmarking and examples of application. The code is written for electron cyclotron studies with emphasis on heating, current drive and ECE diagnostic. The code works with an arbitrary 3D magnetic equilibrium being applicable for both stellarators and tokamaks. The equations for ray tracing are taken in the weakly relativistic approach, i.e. with thermal effects taken into account, while the absorption, current drive and emissivity are calculated in the fully relativistic approach. For the calculation of ECCD, an adjoint technique with parallel momentum conservation is applied. The code is controlled through a specially designed graphical user interface, which allows the preparation of the input parameters and viewing the results in convenient (2D and 3D) form.

  6. Thermal radiation characteristics of nonisothermal cylindrical enclosures using a numerical ray tracing technique

    NASA Technical Reports Server (NTRS)

    Baumeister, Joseph F.

    1990-01-01

    Analysis of energy emitted from simple or complex cavity designs can lead to intricate solutions due to nonuniform radiosity and irradiation within a cavity. A numerical ray tracing technique was applied to simulate radiation propagating within and from various cavity designs. To obtain the energy balance relationships between isothermal and nonisothermal cavity surfaces and space, the computer code NEVADA was utilized for its statistical technique applied to numerical ray tracing. The analysis method was validated by comparing results with known theoretical and limiting solutions, and the electrical resistance network method. In general, for nonisothermal cavities the performance (apparent emissivity) is a function of cylinder length-to-diameter ratio, surface emissivity, and cylinder surface temperatures. The extent of nonisothermal conditions in a cylindrical cavity significantly affects the overall cavity performance. Results are presented over a wide range of parametric variables for use as a possible design reference.

  7. Mathematic models for a ray tracing method and its applications in wireless optical communications.

    PubMed

    Zhang, Minglun; Zhang, Yangan; Yuan, Xueguang; Zhang, Jinnan

    2010-08-16

    This paper presents a new ray tracing method, which contains a whole set of mathematic models, and its validity is verified by simulations. In addition, both theoretical analysis and simulation results show that the computational complexity of the method is much lower than that of previous ones. Therefore, the method can be used to rapidly calculate the impulse response of wireless optical channels for complicated systems. PMID:20721238

  8. Detection and quantification of trace elements in rice and rice products using x-ray fluorescence

    NASA Astrophysics Data System (ADS)

    Foran, Kelly A.; Fleming, David E. B.

    2015-12-01

    We used X-ray fluorescence (XRF) to examine the presence of arsenic (As) and other trace elements (manganese, iron, nickel, copper, and zinc) in rice and rice products. A portable XRF analyzer was used to test samples, and amplitudes for the analyzed elements were identified in the resulting data. The detection limit of the system was sufficiently low to detect As in some rice and rice product samples.

  9. Multiscale optical simulation settings: challenging applications handled with an iterative ray-tracing FDTD interface method.

    PubMed

    Leiner, Claude; Nemitz, Wolfgang; Schweitzer, Susanne; Kuna, Ladislav; Wenzl, Franz P; Hartmann, Paul; Satzinger, Valentin; Sommer, Christian

    2016-03-20

    We show that with an appropriate combination of two optical simulation techniques-classical ray-tracing and the finite difference time domain method-an optical device containing multiple diffractive and refractive optical elements can be accurately simulated in an iterative simulation approach. We compare the simulation results with experimental measurements of the device to discuss the applicability and accuracy of our iterative simulation procedure. PMID:27140556

  10. Reflectivity and imaging capabilities of spherically bent crystals studied by ray-tracing simulations

    NASA Astrophysics Data System (ADS)

    Lavrinenko, Ya S.; Morozov, I. V.; Pikuz, S. A.; Skobelev, I. Yu

    2015-11-01

    Spherically bent crystals are widely used in focusing monochromators, spectrometers and other x-ray optical systems. In particular, they are used in focusing spectrometers with spatial resolution, applied in high energy density diagnostics and warm dense matter studies. In this case, plasma parameters are obtained via measurements of relative intensities of characteristic spectral emission lines for multiply charged ions, which are affected by an instrumental function. Here we develop and use the ray-tracing computer simulations to study reflectivity properties of spherically bent crystals in a particular experimental conditions and to provide the method to adjust and validate the measured spectral line intensities on quantitative basis.

  11. A new kind of splines and their use for fast ray-tracing in reflective cavities

    NASA Astrophysics Data System (ADS)

    Pantelic, Dejan V.; Janevski, Zoran D.

    1989-08-01

    In this paper we are presenting a new kind of splines that are very effective in ray-tracing applications. They are designed in such a way to enable the fast and efficient computation of line-spline intersections (line representing the light ray, and spline representing the reflective cavity). These splines are piecewise parabolic polynomials, but with additional degrees of freedom. Polynomial sections of the spline can be rotated to a certain angle (each section has its own angle of rotation), enabling thus the continuity of the first derivative.

  12. Stress optical path difference analysis of off-axis lens ray trace footprint

    NASA Astrophysics Data System (ADS)

    Hsu, Ming-Ying; Chan, Chia-Yen; Lin, Wei-Cheng; Wu, Kun-Huan; Chen, Chih-Wen; Chan, Shenq-Tsong; Huang, Ting-Ming

    2013-06-01

    The mechanical and thermal stress on lens will cause the glass refractive index different, the refractive index of light parallel and light perpendicular to the direction of stress. The refraction index changes will introduce Optical Path Difference (OPD). This study is applying Finite Element Method (FEM) and optical ray tracing; calculate off axis ray stress OPD. The optical system stress distribution result is calculated from finite element simulation, and the stress coordinate need to rotate to optical path direction. Meanwhile, weighting stress to each optical ray path and sum the ray path OPD. The Z-direction stress OPD can be fitted by Zernike polynomial, the separated to sag difference, and rigid body motion. The fitting results can be used to evaluate the stress effect on optical component.

  13. Simulation and optimization of the NSLS-II SRX beamline combining ray-tracing and wavefront propagation

    SciTech Connect

    De Andrade V.; Thieme J.; Chubar O.

    2011-10-14

    The Sub-micron Resolution X-ray spectroscopy (SRX) beamline will benefit from the ultralow emittance of the National Synchrotron Light Source II to address a wide variety of scientific applications studying heterogeneous systems at the sub-micrometer scale. This work focuses on the KB branch ({Delta}E: 4.65-28 keV). Its main optical components include a horizontally focusing mirror forming an adjustable secondary source, a horizontally deflecting monochromator and two sets of Kirkpatrick-Baez mirrors as focusing optics of two distinct inline stations for operations requiring either high flux or high resolution. In the first approach, the beamline layout was optimized with ray-tracing calculations involving Shadowvui computer codes. As a result, the location and characteristics of optics were specified for achieving either the most intense or the smallest monochromatic beam possible on the target (10{sup 13} ph/s or 10{sup 12} ph/s respectively in a 500 nm or 65 nm focal spot). At the nanoprobe station, the diffraction limited focusing of X-rays is governed by the beam coherence. Hence, a classical geometric approach is not anymore adapted. To get reliable estimates of the Nanoprobe performances, a wavefront propagation study was performed using Synchrotron Radiation Workshop (SRW) code. At 7.2 keV, calculations show an intense (10{sup 12} ph/s) 67 nm wide diffraction limited spot achieved with actual metrological data of mirrors.

  14. Chorus wave-normal statistics in the Earth's radiation belts from ray tracing technique

    NASA Astrophysics Data System (ADS)

    Breuillard, H.; Zaliznyak, Y.; Krasnoselskikh, V.; Agapitov, O.; Artemyev, A.; Rolland, G.

    2012-08-01

    Discrete ELF/VLF (Extremely Low Frequency/Very Low Frequency) chorus emissions are one of the most intense electromagnetic plasma waves observed in radiation belts and in the outer terrestrial magnetosphere. These waves play a crucial role in the dynamics of radiation belts, and are responsible for the loss and the acceleration of energetic electrons. The objective of our study is to reconstruct the realistic distribution of chorus wave-normals in radiation belts for all magnetic latitudes. To achieve this aim, the data from the electric and magnetic field measurements onboard Cluster satellite are used to determine the wave-vector distribution of the chorus signal around the equator region. Then the propagation of such a wave packet is modeled using three-dimensional ray tracing technique, which employs K. Rönnmark's WHAMP to solve hot plasma dispersion relation along the wave packet trajectory. The observed chorus wave distributions close to waves source are first fitted to form the initial conditions which then propagate numerically through the inner magnetosphere in the frame of the WKB approximation. Ray tracing technique allows one to reconstruct wave packet properties (electric and magnetic fields, width of the wave packet in k-space, etc.) along the propagation path. The calculations show the spatial spreading of the signal energy due to propagation in the inhomogeneous and anisotropic magnetized plasma. Comparison of wave-normal distribution obtained from ray tracing technique with Cluster observations up to 40° latitude demonstrates the reliability of our approach and applied numerical schemes.

  15. A data distributed, parallel algorithm for ray-traced volume rendering

    SciTech Connect

    Ma, Kwan-Liu; Painter, J.S.; Hansen, C.D.; Krogh, M.F.

    1993-03-30

    This paper presents a divide-and-conquer ray-traced volume rendering algorithm and its implementation on networked workstations and a massively parallel computer, the Connection Machine CM-5. This algorithm distributes the data and the computational load to individual processing units to achieve fast, high-quality rendering of high-resolution data, even when only a modest amount of memory is available on each machine. The volume data, once distributed, is left intact. The processing nodes perform local ray-tracing of their subvolume concurrently. No communication between processing units is needed during this locally ray-tracing process. A subimage is generated by each processing unit and the final image is obtained by compositing subimages in the proper order, which can be determined a priori. Implementations and tests on a group of networked workstations and on the Thinking Machines CM-5 demonstrate the practicality of our algorithm and expose different performance tuning issues for each platform. We use data sets from medical imaging and computational fluid dynamics simulations in the study of this algorithm.

  16. Trace element abundance determinations by Synchrotron X Ray Fluorescence (SXRF) on returned comet nucleus mineral grains

    NASA Technical Reports Server (NTRS)

    Flynn, G. J.; Sutton, S. R.

    1989-01-01

    Trace element analyses were performed on bulk cosmic dust particles by Proton Induced X Ray Emission (PIXE) and Synchrotron X Ray Fluorescence (SXRF). When present at or near chondritic abundances the trace elements K, Ti, Cr, Mn, Cu, Zn, Ga, Ge, Se, and Br are presently detectable by SXRF in particles of 20 micron diameter. Improvements to the SXRF analysis facility at the National Synchrotron Light Source presently underway should increase the range of detectable elements and permit the analysis of smaller samples. In addition the Advanced Photon Source will be commissioned at Argonne National Laboratory in 1995. This 7 to 8 GeV positron storage ring, specifically designed for high-energy undulator and wiggler insertion devices, will be an ideal source for an x ray microprobe with one micron spatial resolution and better than 100 ppb elemental sensitivity for most elements. Thus trace element analysis of individual micron-sized grains should be possible by the time of the comet nucleus sample return mission.

  17. Ray tracing in the human eye: measurement and modeling of optical aberrations

    NASA Astrophysics Data System (ADS)

    Navarro, Rafael M.; Rodriguez, P.; Gonzalez, L.; Aporta, J.; Hdez-Matamoros, J. L.

    2004-10-01

    The rapid development of cataract and refractive surgery requires new methods to assess the optical quality of the eye. The optimized optical design of custom treatments to improve the optical performance of individual eyes requires, at least, to have the technology to (1) measure the geometry (anatomy) of the optics of the eye; (2) measure the optical performance (refractive state, aberrations, etc); (3) Build a custom optical and anatomical model of the individual eye to treat; (4) Optimal design of custom treatments. In this communication we will present the work carried out by our group to develop methods for measuring and modeling the optical performance of the eye. In particular, we will focus, first, on the Laser Ray Tracing method that we have developed to measure the optical aberrations of the eye, as a physical in vivo implementation of the classical numerical ray tracing used by optical designers; and second, on the development of custom optical models of the eye to perform that numerical ray tracing which predicts with a high fidelity experimental measurements. The methods developed have been applied to design both custom surgery and optical aids to improve optical performance.

  18. Ray-tracing and physical-optics analysis of the aperture efficiency in a radio telescope.

    PubMed

    Olmi, Luca; Bolli, Pietro

    2007-07-01

    The performance of telescope systems working at microwave or visible-IR wavelengths is typically described in terms of different parameters according to the wavelength range. Most commercial ray-tracing packages have been specifically designed for use with visible-IR systems and thus, though very flexible and sophisticated, do not provide the appropriate parameters to fully describe microwave antennas and to compare with specifications. We demonstrate that the Strehl ratio is equal to the phase efficiency when the apodization factor is taken into account. The phase efficiency is the most critical contribution to the aperture efficiency of an antenna and the most difficult parameter to optimize during the telescope design. The equivalence between the Strehl ratio and the phase efficiency gives the designer/user of the telescope the opportunity to use the faster commercial ray-tracing software to optimize the design. We also discuss the results of several tests performed to check the validity of this relationship that we carried out using a ray-tracing software, ZEMAX, and a full Physical Optics software, GRASP9.3, applied to three different telescope designs that span a factor of approximately 10 in terms of D/lambda. The maximum measured discrepancy between phase efficiency and Strehl ratio varies between approximately 0.4% and 1.9% up to an offset angle of >40 beams, depending on the optical configuration, but it is always less than 0.5% where the Strehl ratio is >0.95. PMID:17571151

  19. Inversion of anisotropic inner core structure from three dimensional ray tracing

    NASA Astrophysics Data System (ADS)

    Sun, X.; Song, X.

    2005-12-01

    Seismological studies have generally suggest that the Earth's inner core is anisotropic and the anisotropic structure change significantly both laterally and with depth. Previous body-wave studies of the inner core have relied on 1-D ray tracing or waveform modeling, which do not account fully the 3D anisotropic structure. Here we adopt a pseudo-bending ray tracing (PBR) method in spherical coordinates (Koketsu and Sekine, 1998) for seismic rays that traverse the inner core (PKP-DF phase). The method iteratively perturbs each discontinuity points and continuous segment of the ray through 3D (but isotropic) earth structure so that its travel time is minimum. Our implementation also includes a flexible scheme in calculating the velocity gradient needed to perturb the ray. A large volume is included in calculating the velocity gradient initially to find the global minimum, but a small volume surrounding the ray is used eventually to obtain the precise local velocity gradient that is sampled by the ray. Tests show that our implementation is very stable, reliable, and fast. We have traced the rays for over 3000 event-station pairs that we have differential PKP travel-time measurements using both the PBR method and a shooting method for a 1D model (AK135). The travel-time difference from the two methods is generally within 0.05 s with a few up to 0.07 s and the largest path difference is within 24 km; Even with a model of strong velocity gradient, the travel time difference is still less than 0.08s and the largest path difference is within 40km. Because the ray direction in the inner core does not change much (within 10 degrees even with a strong velocity gradient in the inner core), the 3D anisotropic structure of the inner core can be approximated to the first order as 3D heterogeneous (but isotropic) structure for a given ray, assuming the inner core anisotropy is axisymmetric. We are implementing the PBR method and B-spline interpolation to invert for 3D anisotropic

  20. Fast robust non-sequential optical ray-tracing with implicit algebraic surfaces

    NASA Astrophysics Data System (ADS)

    Greynolds, Alan W.

    2015-09-01

    The fastest, most robust, general technique for non-sequentially ray-tracing a large class of imaging and non-imaging optical systems is by geometric modeling with algebraic (i.e. polynomial) implicit surfaces. The basic theory of these surfaces with special attention to optimizing their precise intersection with a ray (even at grazing incidence) is outlined for an admittedly limited software implementation. On a couple of "tame" examples, a 64-bit Windows 7 version is significantly faster than the fastest commercial design software (all multi-threaded). Non-sequential ray-surface interactions approaching 30M/sec are achieved on a 12-core 2.67 GHz Mac Pro desktop computer. For a more exotic example of a 6th degree Wood's horn beam dump (light trap), a 32-bit Windows single thread version traces rays nearly 4 times faster than the commercial ASAP software's implicit algebraic surface and over 13 times faster than its equivalent NURBS surface. However, implicit surfaces are foreign to most CAD systems and thus unfortunately, don't easily fit into a modern workflow.

  1. Subhalo Tracing in Simulations and Subhalo Observation in Gamma-rays

    NASA Astrophysics Data System (ADS)

    Han, J. X.

    2014-05-01

    Current major observations of the Universe favor the concordant ΛCDM cosmology, in which the matter content is dominated by cold dark matter (CDM). In this CDM universe, small perturbations from the initial condition grow into clumps of virilized structure called dark matter haloes. Small haloes form early and later merge to form bigger haloes. As a result, dark matter haloes host plenty of substructures called subhaloes which are the self-bound remnants of their progenitor haloes. These subhaloes could be studied in detail with the help of numerical simulations, which then could provide input into theories of galaxy formation, and also influence the way dark matter could be detected. To find and trace dark matter subhaloes in simulations, we develop a new code, the Hierarchical Bound-Tracing (HBT for short) code, based on the merger hierarchy of dark matter haloes. Application of this code to a recent benchmark test of finding subhaloes demonstrates that HBT stands as one of the best codes to trace the evolutionary history of subhaloes. The success of this code lies in its careful treatment of the complex physical processes associated with the evolution of subhaloes, and in its robust unbinding algorithm with an adaptive source subhalo management. We keep a full record of the merger hierarchy of haloes and subhaloes, and allow growth of satellite subhaloes through accretion from its ``satellite-of-satellites'', hence allowing mergers among satellites. Local accretion of background mass is omitted, while rebinding of stripped mass is allowed. The justification of these treatments is provided by case studies of the lives of individual subhaloes, and by the success in finding the complete subhalo catalogue. We compare our result to other popular subhalo finders. It is shown that HBT is able to well resolve subhaloes in high density environment, and keep strict physical track of subhaloes' merger history. This code is fully parallelized, and freely available upon

  2. Subhalo Tracing in Simulations and Subhalo Observation in Gamma-rays

    NASA Astrophysics Data System (ADS)

    Han, J. X.

    2014-05-01

    Current major observations of the Universe favor the concordant ΛCDM cosmology, in which the matter content is dominated by cold dark matter (CDM). In this CDM universe, small perturbations from the initial condition grow into clumps of virilized structure called dark matter haloes. Small haloes form early and later merge to form bigger haloes. As a result, dark matter haloes host plenty of substructures called subhaloes which are the self-bound remnants of their progenitor haloes. These subhaloes could be studied in detail with the help of numerical simulations, which then could provide input into theories of galaxy formation, and also influence the way dark matter could be detected. To find and trace dark matter subhaloes in simulations, we develop a new code, the Hierarchical Bound-Tracing (HBT for short) code, based on the merger hierarchy of dark matter haloes. Application of this code to a recent benchmark test of finding subhaloes demonstrates that HBT stands as one of the best codes to trace the evolutionary history of subhaloes. The success of this code lies in its careful treatment of the complex physical processes associated with the evolution of subhaloes, and in its robust unbinding algorithm with an adaptive source subhalo management. We keep a full record of the merger hierarchy of haloes and subhaloes, and allow growth of satellite subhaloes through accretion from its ``satellite-of-satellites'', hence allowing mergers among satellites. Local accretion of background mass is omitted, while rebinding of stripped mass is allowed. The justification of these treatments is provided by case studies of the lives of individual subhaloes, and by the success in finding the complete subhalo catalogue. We compare our result to other popular subhalo finders. It is shown that HBT is able to well resolve subhaloes in high density environment, and keep strict physical track of subhaloes' merger history. This code is fully parallelized, and freely available upon

  3. Comparing FDTD and Ray-Tracing Models in Numerical Simulation of HgCdTe LWIR Photodetectors

    NASA Astrophysics Data System (ADS)

    Vallone, Marco; Goano, Michele; Bertazzi, Francesco; Ghione, Giovanni; Schirmacher, Wilhelm; Hanna, Stefan; Figgemeier, Heinrich

    2016-04-01

    We present a simulation study of HgCdTe-based long-wavelength infrared detectors, focusing on methodological comparisons between the finite-difference time-domain (FDTD) and ray-tracing optical models. We performed three-dimensional simulations to determine the absorbed photon density distributions and the corresponding photocurrent and quantum efficiency spectra of isolated n-on-p uniform-composition pixels, systematically comparing the results obtained with FDTD and ray tracing. Since ray tracing is a classical optics approach, unable to describe interference effects, its applicability has been found to be strongly wavelength dependent, especially when reflections from metallic layers are relevant. Interesting cavity effects around the material cutoff wavelength are described, and the cases where ray tracing can be considered a viable approximation are discussed.

  4. Comparing FDTD and Ray-Tracing Models in Numerical Simulation of HgCdTe LWIR Photodetectors

    NASA Astrophysics Data System (ADS)

    Vallone, Marco; Goano, Michele; Bertazzi, Francesco; Ghione, Giovanni; Schirmacher, Wilhelm; Hanna, Stefan; Figgemeier, Heinrich

    2016-09-01

    We present a simulation study of HgCdTe-based long-wavelength infrared detectors, focusing on methodological comparisons between the finite-difference time-domain (FDTD) and ray-tracing optical models. We performed three-dimensional simulations to determine the absorbed photon density distributions and the corresponding photocurrent and quantum efficiency spectra of isolated n-on- p uniform-composition pixels, systematically comparing the results obtained with FDTD and ray tracing. Since ray tracing is a classical optics approach, unable to describe interference effects, its applicability has been found to be strongly wavelength dependent, especially when reflections from metallic layers are relevant. Interesting cavity effects around the material cutoff wavelength are described, and the cases where ray tracing can be considered a viable approximation are discussed.

  5. Adaptive Gene Loss? Tracing Back the Pseudogenization of the Rabbit CCL8 Chemokine.

    PubMed

    van der Loo, Wessel; Magalhaes, Maria João; de Matos, Ana Lemos; Abrantes, Joana; Yamada, Fumio; Esteves, Pedro J

    2016-08-01

    Studies of the process of pseudogenization have widened our understanding of adaptive evolutionary change. In Rabbit, an alteration at the second extra-cellular loop of the CCR5 chemokine receptor was found to be associated with the pseudogenization of one of its prime ligands, the chemokine CCL8. This relationship has raised questions about the existence of a causal link between both events, which would imply adaptive gene loss. This hypothesis is evaluated here by tracing back the history of the genetic modifications underlying the chemokine pseudogenization. The obtained data indicate that mutations at receptor and ligand genes occurred after the lineage split of New World Leporids versus Old World Leporids and prior to the generic split of the of Old World species studied, which occurred an estimated 8-9 million years ago. More important, they revealed the emergence, before this zoographical split, of a "slippery" nucleotide motif (CCCCGGG) at the 3' region of CCL8-exon2. Such motives are liable of generating +1G or -1G frameshifts, which could, however, be overcome by "translesion" synthesis or somatic reversion. The CCL8 pseudogenization in the Old World lineage was apparently initiated by three synapomorphic point mutations at the exon2-intron2 boundary which provide at short range premature terminating codons, independently of the reading frame imposed by the slippery motif. The presence of this motif in New World Leporids might allow verifying this scenario. The importance of CCL8-CCR5 signaling in parasite-host interaction would suggest that the CCL8 knock-out in Old World populations might be related to changes in pathogenic environment. PMID:27306379

  6. Line shape and ray trace calculations in saturated X-ray lasers: Application to Ni-like silver

    NASA Astrophysics Data System (ADS)

    Benredjem, D.; Guilbaud, O.; Möller, C.; Klisnick, A.; Ros, D.; Dubau, J.; Calisti, A.; Talin, B.

    2006-05-01

    Longitudinal coherence length in X-ray lasers depends strongly on the shape of the amplified line. We have modelled an experiment performed at the LULI facility of Ecole Polytechnique. The experiment was devoted to the study of the temporal (longitudinal) coherence of the transient Ni-like silver 4d 4p transition X-ray laser at 13.9 nm. Accurate line shape calculations using PPP, a spectral line shape code, confirm that the Voigt profile is a good approximation for this X-ray laser line. This allows us to extensively use the Voigt shape in conditions where the amplifier, i.e. the plasma produced by the interaction of a high intensity laser with a slab target, is neither stationary nor homogeneous. Our calculations involve a ray trace code which is a post-processor to the hydrodynamic simulation EHYBRID. As the effect of saturation is important for the level populations and gains we include the interaction between the amplified beam and the medium using the Maxwell-Bloch formalism. While the FWHM of the spontaneous emission profile is ˜10 mÅ, the amplified X-ray line exhibits gain narrowing leading to the smaller width ˜3 mÅ. Comparison with experiment is discussed.

  7. Geodesic constant method: A novel approach to analytical surface-ray tracing on convex conducting bodies

    NASA Astrophysics Data System (ADS)

    Jha, R. M.; Wiesbeck, W.

    1995-04-01

    A generalized approach to analytical surface-ray tracing in three dimensions, and a review of its application to convex conducting bodies, is presented, using the Eisenhart Coordinate System. The ray-parameters so obtained, for quadric cylinders (QUACYLs) and surfaces of revolution (QUASORs), are in a one-parameter form for UTD mutual-coupling applications. The ray analysis is also extended to the hybrid QUACYLs (e.g., aircraft wings) and hybrid QUASORs (e.g., satellite-launch vehicles), by introducing Hertz's principle of particle dynamics to EM theory. This mathematical formulation is applicable even to other important non-Eisenhart surfaces, such as the ogive. A summary of the mathematical formulations is included.

  8. R-LODs: fast LOD-based ray tracing of massive models

    SciTech Connect

    Yoon, Sung-Eui; Lauterbach, Christian; Manocha, Dinesh

    2006-08-25

    We present a novel LOD (level-of-detail) algorithm to accelerate ray tracing of massive models. Our approach computes drastic simplifications of the model and the LODs are well integrated with the kd-tree data structure. We introduce a simple and efficient LOD metric to bound the error for primary and secondary rays. The LOD representation has small runtime overhead and our algorithm can be combined with ray coherence techniques and cache-coherent layouts to improve the performance. In practice, the use of LODs can alleviate aliasing artifacts and improve memory coherence. We implement our algorithm on both 32bit and 64bit machines and able to achieve up to 2.20 times improvement in frame rate of rendering models consisting of tens or hundreds of millions of triangles with little loss in image quality.

  9. A computer program to trace seismic ray distribution in complex two-dimensional geological models

    USGS Publications Warehouse

    Yacoub, Nazieh K.; Scott, James H.

    1970-01-01

    A computer program has been developed to trace seismic rays and their amplitudes and energies through complex two-dimensional geological models, for which boundaries between elastic units are defined by a series of digitized X-, Y-coordinate values. Input data for the program includes problem identification, control parameters, model coordinates and elastic parameter for the elastic units. The program evaluates the partitioning of ray amplitude and energy at elastic boundaries, computes the total travel time, total travel distance and other parameters for rays arising at the earth's surface. Instructions are given for punching program control cards and data cards, and for arranging input card decks. An example of printer output for a simple problem is presented. The program is written in FORTRAN IV language. The listing of the program is shown in the Appendix, with an example output from a CDC-6600 computer.

  10. GRay: A Massively Parallel GPU-based Code for Ray Tracing in Relativistic Spacetimes

    NASA Astrophysics Data System (ADS)

    Chan, Chi-kwan; Psaltis, Dimitrios; Özel, Feryal

    2013-11-01

    We introduce GRay, a massively parallel integrator designed to trace the trajectories of billions of photons in a curved spacetime. This graphics-processing-unit (GPU)-based integrator employs the stream processing paradigm, is implemented in CUDA C/C++, and runs on nVidia graphics cards. The peak performance of GRay using single-precision floating-point arithmetic on a single GPU exceeds 300 GFLOP (or 1 ns per photon per time step). For a realistic problem, where the peak performance cannot be reached, GRay is two orders of magnitude faster than existing central-processing-unit-based ray-tracing codes. This performance enhancement allows more effective searches of large parameter spaces when comparing theoretical predictions of images, spectra, and light curves from the vicinities of compact objects to observations. GRay can also perform on-the-fly ray tracing within general relativistic magnetohydrodynamic algorithms that simulate accretion flows around compact objects. Making use of this algorithm, we calculate the properties of the shadows of Kerr black holes and the photon rings that surround them. We also provide accurate fitting formulae of their dependencies on black hole spin and observer inclination, which can be used to interpret upcoming observations of the black holes at the center of the Milky Way, as well as M87, with the Event Horizon Telescope.

  11. GRay: A MASSIVELY PARALLEL GPU-BASED CODE FOR RAY TRACING IN RELATIVISTIC SPACETIMES

    SciTech Connect

    Chan, Chi-kwan; Psaltis, Dimitrios; Özel, Feryal

    2013-11-01

    We introduce GRay, a massively parallel integrator designed to trace the trajectories of billions of photons in a curved spacetime. This graphics-processing-unit (GPU)-based integrator employs the stream processing paradigm, is implemented in CUDA C/C++, and runs on nVidia graphics cards. The peak performance of GRay using single-precision floating-point arithmetic on a single GPU exceeds 300 GFLOP (or 1 ns per photon per time step). For a realistic problem, where the peak performance cannot be reached, GRay is two orders of magnitude faster than existing central-processing-unit-based ray-tracing codes. This performance enhancement allows more effective searches of large parameter spaces when comparing theoretical predictions of images, spectra, and light curves from the vicinities of compact objects to observations. GRay can also perform on-the-fly ray tracing within general relativistic magnetohydrodynamic algorithms that simulate accretion flows around compact objects. Making use of this algorithm, we calculate the properties of the shadows of Kerr black holes and the photon rings that surround them. We also provide accurate fitting formulae of their dependencies on black hole spin and observer inclination, which can be used to interpret upcoming observations of the black holes at the center of the Milky Way, as well as M87, with the Event Horizon Telescope.

  12. Ray-tracing simulation and SABER satellite observations of convective gravity waves

    NASA Astrophysics Data System (ADS)

    Kalisch, Silvio; Eckermann, Stephen; Ern, Manfred; Preusse, Peter; Riese, Martin; Trinh, Quang Thai; Kim, Young-Ha; Chun, Hye-Yeong

    Gravity waves (GWs) are known as a coupling mechanism between different atmospheric layers. They contribute to the wave-driving of the QBO and are also responsible for driving large scale circulations like the Brewer-Dobson circulation. One major and highly variable source of GWs is convection. Deep convection in the tropics excites GWs with prominent amplitudes and horizontal phase speeds of up to 90 m/s. These GWs propagate upward and, when breaking, release the wave's momentum, thus accelerate the background flow. Direction and magnitude of the acceleration strongly depends on wind filtering between the convective GW source and the considered altitude. Both, the generation mechanism of GWs close to the top of deep convective towers and the wind filtering process during GW propagation largely influence the GW spectrum found in the tropical middle atmosphere and therefore magnitude and direction of the acceleration. We present the results of GW ray-tracing calculations from tropospheric (convective) sources up to the mesosphere. The Gravity wave Regional Or Global RAy-Tracer (GROGRAT) was used to perform the GW trajectory calculations. The convective GW source scheme from Yonsei University (South Korea) served as the lower boundary condition to quantify the GW excitation from convection. Heating rates, cloud top data, and atmospheric background data were provided by the MERRA dataset for the calculation of convective forcing from deep convection and for the atmospheric background of the ray-tracing calculations afterwards. In order to validate our ray-tracing simulation results, we compare them to satellite measurements of temperature amplitudes and momentum fluxes from the SABER instrument. Therefore, observational constrains from limb-sounding instruments have been quantified. Influences of orbit geometry, the instrument's observational filter, and the wavelength shift in the observed GW spectrum are discussed. Geographic structures in the observed global

  13. Wolter X-Ray Microscope Computed Tomography Ray-Trace Model with Preliminary Simulation Results

    SciTech Connect

    Jackson, J A

    2006-02-27

    It is proposed to build a Wolter X-ray Microscope Computed Tomography System in order to characterize objects to sub-micrometer resolution. Wolter Optics Systems use hyperbolic, elliptical, and/or parabolic mirrors to reflect x-rays in order to focus or magnify an image. Wolter Optics have been used as telescopes and as microscopes. As microscopes they have been used for a number of purposes such as measuring emission x-rays and x-ray fluoresce of thin biological samples. Standard Computed Tomography (CT) Systems use 2D radiographic images, from a series of rotational angles, acquired by passing x-rays through an object to reconstruct a 3D image of the object. The x-ray paths in a Wolter X-ray Microscope will be considerably different than those of a standard CT system. There is little information about the 2D radiographic images that can be expected from such a system. There are questions about the quality, resolution and focusing range of an image created with such a system. It is not known whether characterization information can be obtained from these images and whether these 2D images can be reconstructed to 3D images of the object. A code has been developed to model the 2D radiographic image created by an object in a Wolter X-ray Microscope. This code simply follows the x-ray through the object and optics. There is no modeling at this point of other effects, such as scattering, reflection losses etc. Any object, of appropriate size, can be used in the model code. A series of simulations using a number of different objects was run to study the effects of the optics. The next step will be to use this model to reconstruct an object from the simulated data. Funding for the project ended before this goal could be accomplished. The following documentation includes: (1) background information on current X-ray imaging systems, (2) background on Wolter Optics, (3) description of the Wolter System being used, (4) purpose, limitations and development of the modeling

  14. An Efficient Ray-Tracing Method for Determining Terrain Intercepts in EDL Simulations

    NASA Technical Reports Server (NTRS)

    Shidner, Jeremy D.

    2016-01-01

    The calculation of a ray's intercept from an arbitrary point in space to a prescribed surface is a common task in computer simulations. The arbitrary point often represents an object that is moving according to the simulation, while the prescribed surface is fixed in a defined frame. For detailed simulations, this surface becomes complex, taking the form of real-world objects such as mountains, craters or valleys which require more advanced methods to accurately calculate a ray's intercept location. Incorporation of these complex surfaces has commonly been implemented in graphics systems that utilize highly optimized graphics processing units to analyze such features. This paper proposes a simplified method that does not require computationally intensive graphics solutions, but rather an optimized ray-tracing method for an assumed terrain dataset. This approach was developed for the Mars Science Laboratory mission which landed on the complex terrain of Gale Crater. First, this paper begins with a discussion of the simulation used to implement the model and the applicability of finding surface intercepts with respect to atmosphere modeling, altitude determination, radar modeling, and contact forces influencing vehicle dynamics. Next, the derivation and assumptions of the intercept finding method are presented. Key assumptions are noted making the routines specific to only certain types of surface data sets that are equidistantly spaced in longitude and latitude. The derivation of the method relies on ray-tracing, requiring discussion on the formulation of the ray with respect to the terrain datasets. Further discussion includes techniques for ray initialization in order to optimize the intercept search. Then, the model implementation for various new applications in the simulation are demonstrated. Finally, a validation of the accuracy is presented along with the corresponding data sets used in the validation. A performance summary of the method will be shown using

  15. Towards adaptive, streaming analysis of x-ray tomography data

    SciTech Connect

    Thomas, Mathew; Kleese van Dam, Kerstin; Marshall, Matthew J.; Kuprat, Andrew P.; Carson, James P.; Lansing, Carina S.; Guillen, Zoe C.; Miller, Erin A.; Lanekoff, Ingela; Laskin, Julia

    2015-03-04

    Temporal and spatial resolution of chemical imaging methodologies such as x-ray tomography are rapidly increasing, leading to more complex experimental procedures and fast growing data volumes. Automated analysis pipelines and big data analytics are becoming essential to effectively evaluate the results of such experiments. Offering those data techniques in an adaptive, streaming environment can further substantially improve the scientific discovery process, by enabling experimental control and steering based on the evaluation of emerging phenomena as they are observed by the experiment. Pacific Northwest National Laboratory (PNNL)’ Chemical Imaging Initiative (CII - http://imaging.pnnl.gov/ ) has worked since 2011 towards developing a framework that allows users to rapidly compose and customize high throughput experimental analysis pipelines for multiple instrument types. The framework, named ‘Rapid Experimental Analysis’ (REXAN) Framework [1], is based on the idea of reusable component libraries and utilizes the PNNL developed collaborative data management and analysis environment ‘Velo’, to provide a user friendly analysis and data management environment for experimental facilities. This article will, discuss the capabilities established for X-Ray tomography, discuss lessons learned, and provide an overview of our more recent work in the Analysis in Motion Initiative (AIM - http://aim.pnnl.gov/ ) at PNNL to provide REXAN capabilities in a streaming environment.

  16. A comprehensive ray tracing study on the impact of solar reflections from glass curtain walls.

    PubMed

    Wong, Justin S J

    2016-01-01

    To facilitate the investigation of the impact of solar reflection from the façades of skyscrapers to surrounding environment, a comprehensive ray tracing model has been developed using the International Commerce Centre (ICC) in Hong Kong as an example. Taking into account the actual physical dimensions of buildings and meteorological data, the model simulates and traces the paths of solar reflections from ICC to the surrounding buildings, assessing the impact in terms of hit locations, light intensity and the hit time on each day throughout the year. Our analyses show that various design and architectural features of ICC have amplified the intensity of reflected solar rays and increased the hit rates of surrounding buildings. These factors include the high reflectivity of glass panels, their upward tilting angles, the concave profile of the 'Dragon Tail' (glass panels near the base), the particular location and orientation of ICC, as well as the immense height of ICC with its large reflective surfaces. The simulation results allow us to accurately map the date and time when the ray projections occur on each of the target buildings, rendering important information such as the number of converging (overlapping) projections, and the actual light intensity hitting each of the buildings at any given time. Comparisons with other skyscrapers such as Taipei 101 in Taiwan and 2-IFC (International Finance Centre) Hong Kong are made. Remedial actions for ICC and preventive measures are also discussed. PMID:26646546

  17. Electron cyclotron ray tracing and absorption predictions for Compact Toroidal Hybrid plasmas using TRAVIS

    NASA Astrophysics Data System (ADS)

    Knowlton, S. F.; Hartwell, G. J.; Maurer, D. A.; Marushchenko, N. B.; Turkin, Y.; Bigelow, T.

    2015-11-01

    Plasmas in the Compact Toroidal Hybrid (CTH), a five field period, l = 2 torsatron (B0 = 0 . 5 T R0 = 0 . 75 m, ap ~ 0 . 2 m) will be heated by second harmonic X-mode electron cyclotron heating with power provided by a 28 GHz gyrotron capable of producing up to 200 kW. Ray-tracing calculations that will guide the selection of the launching position, antenna focal length, and beam-steering characteristics are performed with the TRAVIS code. Non-axisymmetric vacuum and current-carrying CTH equilibria for the ray tracing are modeled with the V3FIT code. The calculated absorption is highest for vertically propagating rays that traverse the region where a saddle of resonant field strength exists. However, the absorption for top-launched waves is more sensitive to variations in the magnetic equilibria than for a radial side launch where the magnetic field profile is tokamak-like. This work is supported by U.S. Department of Energy Grant No. DE-FG02-00ER54610.

  18. Photorealistic ray tracing of free-space invisibility cloaks made of uniaxial dielectrics.

    PubMed

    Halimeh, Jad C; Wegener, Martin

    2012-12-17

    The design rules of transformation optics generally lead to spatially inhomogeneous and anisotropic impedance-matched magneto-dielectric material distributions for, e.g., free-space invisibility cloaks. Recently, simplified anisotropic non-magnetic free-space cloaks made of a locally uniaxial dielectric material (calcite) have been realized experimentally. In a two-dimensional setting and for in-plane polarized light propagating in this plane, the cloaking performance can still be perfect for light rays. However, for general views in three dimensions, various imperfections are expected. In this paper, we study two different purely dielectric uniaxial cylindrical free-space cloaks. For one, the optic axis is along the radial direction, for the other one it is along the azimuthal direction. The azimuthal uniaxial cloak has not been suggested previously to the best of our knowledge. We visualize the cloaking performance of both by calculating photorealistic images rendered by ray tracing. Following and complementing our previous ray-tracing work, we use an equation of motion directly derived from Fermat's principle. The rendered images generally exhibit significant imperfections. This includes the obvious fact that cloaking does not work at all for horizontal or for ordinary linear polarization of light. Moreover, more subtle effects occur such as viewing-angle-dependent aberrations. However, we still find amazingly good cloaking performance for the purely dielectric azimuthal uniaxial cloak. PMID:23263067

  19. Spin tracking simulations in AGS based on ray-tracing methods - bare lattice, no snakes -

    SciTech Connect

    Meot, F.; Ahrens, L.; Gleen, J.; Huang, H.; Luccio, A.; MacKay, W. W.; Roser, T.; Tsoupas, N.

    2009-09-01

    This Note reports on the first simulations of and spin dynamics in the AGS using the ray-tracing code Zgoubi. It includes lattice analysis, comparisons with MAD, DA tracking, numerical calculation of depolarizing resonance strengths and comparisons with analytical models, etc. It also includes details on the setting-up of Zgoubi input data files and on the various numerical methods of concern in and available from Zgoubi. Simulations of crossing and neighboring of spin resonances in AGS ring, bare lattice, without snake, have been performed, in order to assess the capabilities of Zgoubi in that matter, and are reported here. This yields a rather long document. The two main reasons for that are, on the one hand the desire of an extended investigation of the energy span, and on the other hand a thorough comparison of Zgoubi results with analytical models as the 'thin lens' approximation, the weak resonance approximation, and the static case. Section 2 details the working hypothesis : AGS lattice data, formulae used for deriving various resonance related quantities from the ray-tracing based 'numerical experiments', etc. Section 3 gives inventories of the intrinsic and imperfection resonances together with, in a number of cases, the strengths derived from the ray-tracing. Section 4 gives the details of the numerical simulations of resonance crossing, including behavior of various quantities (closed orbit, synchrotron motion, etc.) aimed at controlling that the conditions of particle and spin motions are correct. In a similar manner Section 5 gives the details of the numerical simulations of spin motion in the static case: fixed energy in the neighboring of the resonance. In Section 6, weak resonances are explored, Zgoubi results are compared with the Fresnel integrals model. Section 7 shows the computation of the {rvec n} vector in the AGS lattice and tuning considered. Many details on the numerical conditions as data files etc. are given in the Appendix Section

  20. Fitting of NWM Ray-traced Slant Factors to Closed-form Tropospheric Mapping Functions

    NASA Astrophysics Data System (ADS)

    Urquhart, L.; Nievinski, F. G.; Santos, M. C.

    2009-05-01

    Ray-tracing in numerical weather models (NWM) is a promising solution for describing the elevation angle- and azimuth-dependence of tropospheric delay, especially at very low elevation angles, in an attempt to de- correlate vertical position and zenith tropospheric delay during GPS estimation. On the other hand, mapping functions expressed in closed form remain imperative, demanded by the need for (i) fast processing and (ii) convenient distribution to end-users, who employ a variety of third-party GPS processing packages. We investigate the fitting of ray-tracing results to closed-form expressions. We neglect the variation of the tropospheric delay with latitude, longitude, and height, offering a mapping function valid for a specific station site (similarly as done for VMF1-Site [Boehm et al., 1996]). We focus on the variation of the delay with time, elevation angle, and azimuth. For the time-dependence, we choose to work with slant factors instead of slant delays, because the former are more stable in time than the latter; that is a consequence of the normalization by zenith delays which removes the bulk of the variation with time. For the elevation angle-dependence we compare the continued form fraction of Yan and Ping [1995] with that of Marini [1972] (normalized to yield unity at zenith, as given by Herring [1992]). The latter is more commonly used, but the former is expected to provide a better fit at elevation angles below five degrees. Since the ray-tracing results do not necessarily assume azimuthal symmetry, we have to account for the azimuth-dependence. For that we compare the single-direction model of Davis et al. [1993] with the inclusion of secondary directions [Seko et al., 2004] and arbitrary spherical harmonics [Böhm and Schuh, 2001]). We also assess whether physically-oblivious models (i.e., not derived from analytical idealized atmospheric models), such spline or polynomials, as suggested by Rocken et al. [2001], are adequate.

  1. Modeling the effect of refraction on OCT imaging of lung tissue: a ray-tracing approach

    NASA Astrophysics Data System (ADS)

    Golabchi, Fatemeh N.; Golabchi, Ali; Brooks, Dana H.; Gouldstone, Andrew; DiMarzio, Charles A.

    2012-03-01

    Determining the structure of lung tissue is difficult in ex-vivo samples. Optical coherence tomography (OCT) can image alveoli but ignores optical effects that distort the images. For example, light refracts and changes speed at the alveolar air-tissue surface. We employ ray-tracing to model OCT imaging with directional and speed changes included, using spherical shapes in 2D. Results show apparent thickening of inter-aveolar walls and distortion of shape and depth. Our approach suggests a correction algorithm by combining the model with image analysis. Distortion correction will allow inference of tissue mechanical properties and deeper imaging.

  2. Modeling and analysis of novel laser weld joint designs using optical ray tracing.

    SciTech Connect

    Milewski, J. O.

    2002-01-01

    Reflection of laser energy presents challenges in material processing that can lead to process inefficiency or process instability. Understanding the fundamentals of non-imaging optics and the reflective propagation of laser energy can allow process and weld joint designs to take advantage of these reflections to enhance process efficiency or mitigate detrimental effects. Optical ray tracing may be used within a 3D computer model to evaluate novel joint and fixture designs for laser welding that take advantage of the reflective propagation of laser energy. This modeling work extends that of previous studies by the author and provides comparison with experimental studies performed on highly reflective metals. Practical examples are discussed.

  3. Ray tracing evaluation of a technique for correcting the refraction errors in satellite tracking data

    NASA Technical Reports Server (NTRS)

    Gardner, C. S.; Rowlett, J. R.; Hendrickson, B. E.

    1978-01-01

    Errors may be introduced in satellite laser ranging data by atmospheric refractivity. Ray tracing data have indicated that horizontal refractivity gradients may introduce nearly 3-cm rms error when satellites are near 10-degree elevation. A correction formula to compensate for the horizontal gradients has been developed. Its accuracy is evaluated by comparing it to refractivity profiles. It is found that if both spherical and gradient correction formulas are employed in conjunction with meteorological measurements, a range resolution of one cm or less is feasible for satellite elevation angles above 10 degrees.

  4. X-Ray fluorescence analysis of trace elements in fruit juice

    NASA Astrophysics Data System (ADS)

    Bao, Sheng-Xiang; Wang, Zhi-Hong; Liu, Jing-Song

    1999-12-01

    X-Ray fluorescence spectrometry is applied to the determination of trace elements in fruit juice characterized by a high content of sugar and other soluble solid substances. Samples are prepared by evaporation, carbonization and pressing into discs. The synthesis of standards is described in detail. All element concentrations are directly estimated from linear calibration curves obtained without any matrix correction. The results of the analysis are in good agreement with those given by inductively coupled plasma-atomic emission spectrometry and atomic absorption spectrometry techniques.

  5. Infrasonic ray tracing applied to mesoscale atmospheric structures: refraction by hurricanes.

    PubMed

    Bedard, Alfred J; Jones, R Michael

    2013-11-01

    A ray-tracing program is used to estimate the refraction of infrasound by the temperature structure of the atmosphere and by hurricanes represented by a Rankine-combined vortex wind plus a temperature perturbation. Refraction by the hurricane winds is significant, giving rise to regions of focusing, defocusing, and virtual sources. The refraction of infrasound by the temperature anomaly associated with a hurricane is small, probably no larger than that from uncertainties in the wind field. The results are pertinent to interpreting ocean wave generated infrasound in the vicinities of tropical cyclones. PMID:24180755

  6. Coupled Ray-tracing and Fokker-Planck EBW Modeling for Spherical Tokamaks

    NASA Astrophysics Data System (ADS)

    Urban, J.; Decker, J.; Peysson, Y.; Preinhaelter, J.; Taylor, G.; Vahala, L.; Vahala, G.

    2009-11-01

    The AMR (Antenna—Mode-conversion—Ray-tracing) code [1, 2] has been recently coupled with the LUKE [3] Fokker-Planck code. This modeling suite is capable of complex simulations of electron Bernstein wave (EBW) emission, heating and current drive. We employ these codes to study EBW heating and current drive performance under spherical tokamak (ST) configurations—typical NSTX discharges are employed. EBW parameters, such as frequency, antenna position and direction, are varied and optimized for particular configurations and objectives. In this way, we show the versatility of EBWs.

  7. Practical Considerations in Trace Element Analysis of Bone by Portable X-ray Fluorescence.

    PubMed

    Byrnes, Jennifer F; Bush, Peter J

    2016-07-01

    Forensic anthropologists are more often turning to nondestructive methods to assist with skeletal analyses, specifically for trace elemental analyses. Portable XRF (pXRF) instruments are versatile and are able to be used in diverse settings or for specimens of a shape and size that cannot be accommodated by laboratory-based instruments. Use of XRF requires knowledge of analysis parameters such as X-ray penetration and exit depth. Analysis depth was determined by examining pure elements through known thicknesses of equine bone slices. Correlation between the element's X-ray emission energy and the depth of reading was observed. Bone surfaces from a small unknown historic cemetery were analyzed before and after sanding of the periosteal surface to observe possible changes in XRF readings based on potential diagenesis. Results validate the pXRF device as a powerful and convenient instrument for nondestructive analysis, while highlighting limitations and considerations for the analysis of osseous materials. PMID:27093090

  8. Tracing X-rays through an L-shaped laterally graded multilayer mirror: a synchrotron application.

    PubMed

    Honnicke, Marcelo Goncalves; Huang, Xianrong; Keister, Jeffrey W; Kodituwakku, Chaminda Nalaka; Cai, Yong Q

    2010-05-01

    A theoretical model to trace X-rays through an L-shaped (nested or Montel Kirkpatrick-Baez mirrors) laterally graded multilayer mirror to be used in a synchrotron application is presented. The model includes source parameters (size and divergence), mirror figure (parabolic and elliptic), multilayer parameters (reflectivity, which depends on layer material, thickness and number of layers) and figure errors (slope error, roughness, layer thickness fluctuation Deltad/d and imperfection in the corners). The model was implemented through MATLAB/OCTAVE scripts, and was employed to study the performance of a multilayer mirror designed for the analyzer system of an ultrahigh-resolution inelastic X-ray scattering spectrometer at National Synchrotron Light Source II. The results are presented and discussed. PMID:20400833

  9. [Research on the X-ray fluorescence spectrometry method to determine trace elements in kimberlite].

    PubMed

    Zhang, Lei; Yan, Chuan-wei; Lu, Yi

    2003-04-01

    It is very important to detect trace elements for kilmberlite. Through improving the working conditions of X-ray fluorescence spectrometer and optimizing the analytical conditions, the determination method of trace elements, such as Sc, Cr, Ni, Y, Nb, La, in kimberlite was worked out. The method has been successfully applied to the determination of trace elements in over 2 thousand samples of kimberlite from Liaoning province. The detection limits of the method were relatively low (the detection limit of Sc droped from 9.54 to 2.83 micrograms.g-1 and the detection limit of La droped from 21.68 micrograms.g-1 to 9.18 micrograms.g-1), i.e. 2.83, 2.15, 2.20, 1.17, 1.05 and 9.18 micrograms.g-1 for Sc, Cr, Ni, Y, Nb and La, respectively. The precision of the method was very high with 2.10%-7.09% of RSD (n = 20). Compared with ICP spectrometry this method is satisfactory. The method has proven to be simple and rapid with low cost and high efficiency. PMID:12961906

  10. Trace element profiles in murine Lewis lung carcinoma by radioisotope-induced X-ray fluorescence.

    PubMed Central

    Frank, A. S.; Schauble, M. K.; Preiss, I. L.

    1986-01-01

    Trace element profiles of various body tissues and tumor were established during growth of the Lewis lung tumor (LLT) with the use of radioisotope-induced X-ray fluorescence (RIXRF) analysis. The LLT, a highly malignant experimental murine tumor, resembles its human counterpart, has a well-defined life cycle, and kills its host in 30 days. When compared with normal controls, Zn, Br, and Rb levels in lung, liver, and skeletal muscle and Zn and Sr levels in bone from tumor-bearing mice exhibited large fluctuations at critical points in the tumor life cycle. In addition, the 24-day primary tumor trace element profile resembled that of its tissue of origin, normal lung, and was quite different from other normal tissues studied. These findings indicate that trace element profiles may help in the diagnosis, staging, and monitoring of disease. RIXRF is an excellent technique for this purpose because it is sensitive and relatively nondestructive of samples and has multielement capabilities. Images Figure 1 p423-a PMID:3953767

  11. Accounting for partiality in serial crystallography using ray-tracing principles

    SciTech Connect

    Kroon-Batenburg, Loes M. J. Schreurs, Antoine M. M.; Ravelli, Raimond B. G.; Gros, Piet

    2015-08-25

    Serial crystallography generates partial reflections from still diffraction images. Partialities are estimated with EVAL ray-tracing simulations, thereby improving merged reflection data to a similar quality as conventional rotation data. Serial crystallography generates ‘still’ diffraction data sets that are composed of single diffraction images obtained from a large number of crystals arbitrarily oriented in the X-ray beam. Estimation of the reflection partialities, which accounts for the expected observed fractions of diffraction intensities, has so far been problematic. In this paper, a method is derived for modelling the partialities by making use of the ray-tracing diffraction-integration method EVAL. The method estimates partialities based on crystal mosaicity, beam divergence, wavelength dispersion, crystal size and the interference function, accounting for crystallite size. It is shown that modelling of each reflection by a distribution of interference-function weighted rays yields a ‘still’ Lorentz factor. Still data are compared with a conventional rotation data set collected from a single lysozyme crystal. Overall, the presented still integration method improves the data quality markedly. The R factor of the still data compared with the rotation data decreases from 26% using a Monte Carlo approach to 12% after applying the Lorentz correction, to 5.3% when estimating partialities by EVAL and finally to 4.7% after post-refinement. The merging R{sub int} factor of the still data improves from 105 to 56% but remains high. This suggests that the accuracy of the model parameters could be further improved. However, with a multiplicity of around 40 and an R{sub int} of ∼50% the merged still data approximate the quality of the rotation data. The presented integration method suitably accounts for the partiality of the observed intensities in still diffraction data, which is a critical step to improve data quality in serial crystallography.

  12. Integrated Ray Tracing (IRT) simulation of SCOTS measurement of GMT fast steering mirror surface

    NASA Astrophysics Data System (ADS)

    Choi, Ji Nyeong; Ryu, Dongok; Kim, Sug-Whan; Graves, Logan; Su, Peng; Huang, Run; Kim, Dae Wook

    2015-09-01

    The Software Configurable Optical Testing System (SCOTS) is one of the newest testing methods for large mirror surfaces. The Integrated Ray Tracing (IRT) technique can be applicable to the SCOTS simulation by performing non-sequential ray tracing from the screen to the camera detector in the real scale. Therefore, the radiometry of distorted pattern images are numerically estimated by the IRT simulation module. In this study, we construct an IRT SCOTS simulation model for the Fast Steering Mirror Prototype (FSMP) surface of the Giant Magellan Telescope (GMT). GMT FSMP is an off-axis ellipsoidal concave mirror that is 1064 mm in diameter and has PV 3.1 mm in aspheric departure. The surface error requirement is less than 20 nm rms. The screen is modeled as an array of 1366 by 768 screen pixels of 0.227 mm in pitch size. The screen is considered as a Lambertian scattering surface. The screen and the camera are positioned around 4390 mm away from the mirror and separated by around 132 mm from each other. The light source are scanning lines and sinusoidal patterns generated by 616,050 rays per one screen pixel. Of the initially generated rays, 0.22 % are received by the camera's detector and contribute to form distorted pattern images. These images are converted to the slope and height maps of the mirror surface. The final result for the height difference between input surface and reconstructed surface was 14.14 nm rms. Additionally, the simulated mirror pattern image was compared with the real SCOTS test for the GMT FSMP. This study shows applicability of using the IRT model to SCOTS simulation with nanometer level numerical accuracy.

  13. Fast ray-tracing of human eye optics on Graphics Processing Units.

    PubMed

    Wei, Qi; Patkar, Saket; Pai, Dinesh K

    2014-05-01

    We present a new technique for simulating retinal image formation by tracing a large number of rays from objects in three dimensions as they pass through the optic apparatus of the eye to objects. Simulating human optics is useful for understanding basic questions of vision science and for studying vision defects and their corrections. Because of the complexity of computing such simulations accurately, most previous efforts used simplified analytical models of the normal eye. This makes them less effective in modeling vision disorders associated with abnormal shapes of the ocular structures which are hard to be precisely represented by analytical surfaces. We have developed a computer simulator that can simulate ocular structures of arbitrary shapes, for instance represented by polygon meshes. Topographic and geometric measurements of the cornea, lens, and retina from keratometer or medical imaging data can be integrated for individualized examination. We utilize parallel processing using modern Graphics Processing Units (GPUs) to efficiently compute retinal images by tracing millions of rays. A stable retinal image can be generated within minutes. We simulated depth-of-field, accommodation, chromatic aberrations, as well as astigmatism and correction. We also show application of the technique in patient specific vision correction by incorporating geometric models of the orbit reconstructed from clinical medical images. PMID:24713524

  14. MCViNE - An object oriented Monte Carlo neutron ray tracing simulation package

    NASA Astrophysics Data System (ADS)

    Lin, Jiao Y. Y.; Smith, Hillary L.; Granroth, Garrett E.; Abernathy, Douglas L.; Lumsden, Mark D.; Winn, Barry; Aczel, Adam A.; Aivazis, Michael; Fultz, Brent

    2016-02-01

    MCViNE (Monte-Carlo VIrtual Neutron Experiment) is an open-source Monte Carlo (MC) neutron ray-tracing software for performing computer modeling and simulations that mirror real neutron scattering experiments. We exploited the close similarity between how instrument components are designed and operated and how such components can be modeled in software. For example we used object oriented programming concepts for representing neutron scatterers and detector systems, and recursive algorithms for implementing multiple scattering. Combining these features together in MCViNE allows one to handle sophisticated neutron scattering problems in modern instruments, including, for example, neutron detection by complex detector systems, and single and multiple scattering events in a variety of samples and sample environments. In addition, MCViNE can use simulation components from linear-chain-based MC ray tracing packages which facilitates porting instrument models from those codes. Furthermore it allows for components written solely in Python, which expedites prototyping of new components. These developments have enabled detailed simulations of neutron scattering experiments, with non-trivial samples, for time-of-flight inelastic instruments at the Spallation Neutron Source. Examples of such simulations for powder and single-crystal samples with various scattering kernels, including kernels for phonon and magnon scattering, are presented. With simulations that closely reproduce experimental results, scattering mechanisms can be turned on and off to determine how they contribute to the measured scattering intensities, improving our understanding of the underlying physics.

  15. Three dimensional ray tracing Jovian magnetosphere in the low frequency range

    NASA Technical Reports Server (NTRS)

    Menietti, J. D.

    1982-01-01

    Ray tracing of the Jovian magnetosphere in the low frequency range (1+40 MHz) has resulted in a new understanding of the source mechanism for Io dependent decametric radiation (DAM). Our three dimensional ray tracing computer code has provided model DAM arcs at 10 deg. intervals of Io longitude source positions for the full 360 deg of Jovian system III longitude. In addition, particularly interesting arcs were singled out for detailed study and modelling. Dependent decametric radiation arcs are categorized according to curvature--the higher curvature arcs are apparently due to wave stimulation at a nonconstant wave normal angle, psi. The psi(f) relationship has a signature that is common to most of the higher curvature arcs. The low curvature arcs, on the other hand, are adequately modelled with a constant wave normal angle of close to 90 deg. These results imply that for higher curvature arcs observed for from Jupiter (to diminish spacecraft motion effects) the electrons providing the gyroemission are relativistically beamed.

  16. MCViNE- An object oriented Monte Carlo neutron ray tracing simulation package

    SciTech Connect

    Lin, J. Y. Y.; Smith, Hillary L.; Granroth, Garrett E.; Abernathy, Douglas L.; Lumsden, Mark D.; Winn, Barry L.; Aczel, Adam A.; Aivazis, Michael; Fultz, Brent

    2015-11-28

    MCViNE (Monte-Carlo VIrtual Neutron Experiment) is an open-source Monte Carlo (MC) neutron ray-tracing software for performing computer modeling and simulations that mirror real neutron scattering experiments. We exploited the close similarity between how instrument components are designed and operated and how such components can be modeled in software. For example we used object oriented programming concepts for representing neutron scatterers and detector systems, and recursive algorithms for implementing multiple scattering. Combining these features together in MCViNE allows one to handle sophisticated neutron scattering problems in modern instruments, including, for example, neutron detection by complex detector systems, and single and multiple scattering events in a variety of samples and sample environments. In addition, MCViNE can use simulation components from linear-chain-based MC ray tracing packages which facilitates porting instrument models from those codes. Furthermore it allows for components written solely in Python, which expedites prototyping of new components. These developments have enabled detailed simulations of neutron scattering experiments, with non-trivial samples, for time-of-flight inelastic instruments at the Spallation Neutron Source. Examples of such simulations for powder and single-crystal samples with various scattering kernels, including kernels for phonon and magnon scattering, are presented. As a result, with simulations that closely reproduce experimental results, scattering mechanisms can be turned on and off to determine how they contribute to the measured scattering intensities, improving our understanding of the underlying physics.

  17. MCViNE- An object oriented Monte Carlo neutron ray tracing simulation package

    DOE PAGESBeta

    Lin, J. Y. Y.; Smith, Hillary L.; Granroth, Garrett E.; Abernathy, Douglas L.; Lumsden, Mark D.; Winn, Barry L.; Aczel, Adam A.; Aivazis, Michael; Fultz, Brent

    2015-11-28

    MCViNE (Monte-Carlo VIrtual Neutron Experiment) is an open-source Monte Carlo (MC) neutron ray-tracing software for performing computer modeling and simulations that mirror real neutron scattering experiments. We exploited the close similarity between how instrument components are designed and operated and how such components can be modeled in software. For example we used object oriented programming concepts for representing neutron scatterers and detector systems, and recursive algorithms for implementing multiple scattering. Combining these features together in MCViNE allows one to handle sophisticated neutron scattering problems in modern instruments, including, for example, neutron detection by complex detector systems, and single and multiplemore » scattering events in a variety of samples and sample environments. In addition, MCViNE can use simulation components from linear-chain-based MC ray tracing packages which facilitates porting instrument models from those codes. Furthermore it allows for components written solely in Python, which expedites prototyping of new components. These developments have enabled detailed simulations of neutron scattering experiments, with non-trivial samples, for time-of-flight inelastic instruments at the Spallation Neutron Source. Examples of such simulations for powder and single-crystal samples with various scattering kernels, including kernels for phonon and magnon scattering, are presented. As a result, with simulations that closely reproduce experimental results, scattering mechanisms can be turned on and off to determine how they contribute to the measured scattering intensities, improving our understanding of the underlying physics.« less

  18. Ray-tracing simulations for the ultra-lightweight X-ray optics toward a future jupiter exploration mission

    NASA Astrophysics Data System (ADS)

    Mitsuishi, I.; Ezoe, Y.; Ogawa, T.; Sato, M.; Nakamura, K.; Numazawa, M.; Takeuchi, K.; Ohashi, T.; Ishikawa, K.; Mitsuda, K.

    2016-01-01

    To investigate a feasibility for in situ X-ray imaging spectrometer JUXTA (Jupiter X-ray Telescope Array) onboard a Japanese Jupiter exploration mission, we demonstrated the ideal performances, i.e., angular resolution, effective area and grasp, of our original, conically-approximated Wolter type-I MEMS-processed optics, by extending the previous ray-tracing simulator. The novel simulator enables us to study both on- and off-axis responses for our optics with two-stage optical configurations for the first time. The on-axis angular resolution is restricted to ∼ 13 μm corresponding to ∼ 10 arcsec on the detector plane without considering the diffraction effect and dominated by the diffraction effect below ∼ 1 keV (e.g., 13 arcsec at 1 keV). Si optics can achieve effective area of >700 mm2 and grasp of >1600 mm2 deg2 at our interesting energy of 600 eV. Larger effective area and grasp can be attained by employing Ni as a substrate material or Ir as a reflecting surface material. However, other factors produced in the fabrication processes such as the waviness on the mirror surface and the deformation error cause the significant performance degradation. Thus, we concluded that MEMS-processed optics can satisfy all the requirements of JUXTA only if the manufacturing accuracy can be controlled.

  19. Use of Synchrotron X-ray Fluorescence to Measure Trace Metal Distribution in the Brain

    NASA Astrophysics Data System (ADS)

    Linkous, D.; Flinn, J. M.; Lanzirotti, A.; Frederickson, C.; Jones, B. F.; Bertsch, P. M.

    2002-12-01

    X26A, National Synchrotron Light Source, was used to quantitatively evaluate the spatial distribution of trace metals, such as Zn and Cu, in brain tissue. X-ray microprobe techniques offer distinct advantages over other analytical methods by allowing analyses to be done in-situ with little or no chemical pretreatment and low detection limits (about 1 ppm). In the context of neuroscience, SXRF can provide non-destructive measurements of specific metal concentrations and distribution within nerve (brain) tissue. Neuronal tissue from organisms having undergone different normal or experimental conditions may be compared, with analytical capacities not limited by binding states of the metal (i.e., vesicular or enzymatic), as is the case with staining techniques.. Whole regions of tissue may be scanned for detectable trace metals at spatial resolutions of 10um or less using focused monochromatic x-ray beams. Here special attention has been given to zinc because it is the most common trace metal in the brain, and levels have been increasing in the environment. In this investigation, zinc concentrations present within the hilus of a rat hippocampus, and to a lesser extent in the cortex, have been shown to increase following long-term ingestion of zinc-enhanced drinking water that was associated with deficits in spatial memory. Concomitantly, copper concentrations in the internal capsule were comparatively lower. Other first order transition metals, Cr, V, Mn, and Co were not detected. In contrast, elevated levels of Zn, Cu, and Fe have been seen in amyloid plaques associated with Alzheimer's disease.

  20. A hybrid method for X-ray optics simulation: combining geometric ray-tracing and wavefront propagation

    PubMed Central

    Shi, Xianbo; Reininger, Ruben; Sanchez del Rio, Manuel; Assoufid, Lahsen

    2014-01-01

    A new method for beamline simulation combining ray-tracing and wavefront propagation is described. The ‘Hybrid Method’ computes diffraction effects when the beam is clipped by an aperture or mirror length and can also simulate the effect of figure errors in the optical elements when diffraction is present. The effect of different spatial frequencies of figure errors on the image is compared with SHADOW results pointing to the limitations of the latter. The code has been benchmarked against the multi-electron version of SRW in one dimension to show its validity in the case of fully, partially and non-coherent beams. The results demonstrate that the code is considerably faster than the multi-electron version of SRW and is therefore a useful tool for beamline design and optimization. PMID:24971960

  1. A hybrid method for X-ray optics simulation: combining geometric ray-tracing and wavefront propagation.

    PubMed

    Shi, Xianbo; Reininger, Ruben; Sanchez Del Rio, Manuel; Assoufid, Lahsen

    2014-07-01

    A new method for beamline simulation combining ray-tracing and wavefront propagation is described. The `Hybrid Method' computes diffraction effects when the beam is clipped by an aperture or mirror length and can also simulate the effect of figure errors in the optical elements when diffraction is present. The effect of different spatial frequencies of figure errors on the image is compared with SHADOW results pointing to the limitations of the latter. The code has been benchmarked against the multi-electron version of SRW in one dimension to show its validity in the case of fully, partially and non-coherent beams. The results demonstrate that the code is considerably faster than the multi-electron version of SRW and is therefore a useful tool for beamline design and optimization. PMID:24971960

  2. Ray tracing based path-length calculations for polarized light tomographic imaging

    NASA Astrophysics Data System (ADS)

    Manjappa, Rakesh; Kanhirodan, Rajan

    2015-09-01

    A ray tracing based path length calculation is investigated for polarized light transport in a pixel space. Tomographic imaging using polarized light transport is promising for applications in optical projection tomography of small animal imaging and turbid media with low scattering. Polarized light transport through a medium can have complex effects due to interactions such as optical rotation of linearly polarized light, birefringence, di-attenuation and interior refraction. Here we investigate the effects of refraction of polarized light in a non-scattering medium. This step is used to obtain the initial absorption estimate. This estimate can be used as prior in Monte Carlo (MC) program that simulates the transport of polarized light through a scattering medium to assist in faster convergence of the final estimate. The reflectance for p-polarized (parallel) and s-polarized (perpendicular) are different and hence there is a difference in the intensities that reach the detector end. The algorithm computes the length of the ray in each pixel along the refracted path and this is used to build the weight matrix. This weight matrix with corrected ray path length and the resultant intensity reaching the detector for each ray is used in the algebraic reconstruction (ART) method. The proposed method is tested with numerical phantoms for various noise levels. The refraction errors due to regions of different refractive index are discussed, the difference in intensities with polarization is considered. The improvements in reconstruction using the correction so applied is presented. This is achieved by tracking the path of the ray as well as the intensity of the ray as it traverses through the medium.

  3. Ray-tracing simulations vs. satellite observations of gravity waves forced by deep convection

    NASA Astrophysics Data System (ADS)

    Kalisch, Silvio; Trinh, Thai; Chun, Hye-Yeong; Ern, Manfred; Preusse, Peter; Eckermann, Stephen D.; Riese, Martin

    2015-04-01

    Gravity waves (GW) are a prominent coupling mechanism between their tropospheric sources and the upper stratosphere to mesosphere region. They contribute prominently to the wave driving of the Quasi-biennial-oscillation (QBO) in the tropics and other large scale circulations like the Brewer-Dobson circulation. One important dynamic source of GWs is convection. Convective GWs have considerable short horizontal wavelengths and are therefore not entirely observable by infrared limb-sounding satellite instruments. For this reason, we present the results of GW ray-tracing calculations from convective sources up to the mesosphere. We utilized the Gravity wave Regional Or Global RAy-Tracer (GROGRAT) to perform the GW trajectory calculations. The launch conditions for each GW were calculated using the convective GW source scheme from Yonsei University (South Korea) to quantify the excitation by deep convection. Heating rates, cloud data, and atmospheric background data were provided by the MERRA dataset for the estimation of convective forcing by deep convection and as the atmospheric background for the ray-tracing calculations afterwards. The resulting momentum flux distributions are in remarkable coincidence with typical geographic regions of deep convection in the tropics. Additionally, the momentum flux distributions of higher latitude regions are simulated using a standard launch distribution for GWs. In order to validate our findings we compare our simulation results with satellite measurements of temperature amplitudes and momentum flux from infrared limb-sounding satellite instruments. These validations are complemented with an in-depth analysis of the observational filter for two different satellite instruments (HIRDLS and SABER). Scanning geometry, limitations in the detection of short wavelengths, aliasing effects, and the detector sensitivity are taken into account to quantify the level of uncertainty in our results. This analysis finally shows a good agreement

  4. Thermal emissions of a two-dimensional graded-index medium solved using a high-precision numerical ray-tracing technique

    NASA Astrophysics Data System (ADS)

    Guo-Dong, Shi; Yong, Huang; Ke-Yong, Zhu

    2016-06-01

    A Runge-Kutta ray-tracing method for determining the thermal emissions of a two-dimensional semitransparent graded-index medium has been developed for this study. A backward ray-tracing method and a backward Monte Carlo method were employed in the calculations. The emission characteristics of a linear refractive index medium were investigated. The results of the Runge-Kutta ray-tracing method were shown to agree well with previously obtained exact solutions. The apparent emissivities of a radial refractive index medium obtained using the Runge-Kutta ray-tracing method fit the analytical solutions well. However, for a sinusoidally distributed nonlinear refractive index medium, the Runge-Kutta ray-tracing method revised emissivity results differed from the results of a linear refractive index bar model at certain angles. The results show that the Runge-Kutta ray-tracing method is effective in dealing with the radiative transfer problems of multidimensional graded index media.

  5. A new 3-D ray tracing method based on LTI using successive partitioning of cell interfaces and traveltime gradients

    NASA Astrophysics Data System (ADS)

    Zhang, Dong; Zhang, Ting-Ting; Zhang, Xiao-Lei; Yang, Yan; Hu, Ying; Qin, Qian-Qing

    2013-05-01

    We present a new method of three-dimensional (3-D) seismic ray tracing, based on an improvement to the linear traveltime interpolation (LTI) ray tracing algorithm. This new technique involves two separate steps. The first involves a forward calculation based on the LTI method and the dynamic successive partitioning scheme, which is applied to calculate traveltimes on cell boundaries and assumes a wavefront that expands from the source to all grid nodes in the computational domain. We locate several dynamic successive partition points on a cell's surface, the traveltimes of which can be calculated by linear interpolation between the vertices of the cell's boundary. The second is a backward step that uses Fermat's principle and the fact that the ray path is always perpendicular to the wavefront and follows the negative traveltime gradient. In this process, the first-arriving ray path can be traced from the receiver to the source along the negative traveltime gradient, which can be calculated by reconstructing the continuous traveltime field with cubic B-spline interpolation. This new 3-D ray tracing method is compared with the LTI method and the shortest path method (SPM) through a number of numerical experiments. These comparisons show obvious improvements to computed traveltimes and ray paths, both in precision and computational efficiency.

  6. GPU-based four-dimensional general-relativistic ray tracing

    NASA Astrophysics Data System (ADS)

    Kuchelmeister, Daniel; Müller, Thomas; Ament, Marco; Wunner, Günter; Weiskopf, Daniel

    2012-10-01

    This paper presents a new general-relativistic ray tracer that enables image synthesis on an interactive basis by exploiting the performance of graphics processing units (GPUs). The application is capable of visualizing the distortion of the stellar background as well as trajectories of moving astronomical objects orbiting a compact mass. Its source code includes metric definitions for the Schwarzschild and Kerr spacetimes that can be easily extended to other metric definitions, relying on its object-oriented design. The basic functionality features a scene description interface based on the scripting language Lua, real-time image output, and the ability to edit almost every parameter at runtime. The ray tracing code itself is implemented for parallel execution on the GPU using NVidia's Compute Unified Device Architecture (CUDA), which leads to performance improvement of an order of magnitude compared to a single CPU and makes the application competitive with small CPU cluster architectures. Program summary Program title: GpuRay4D Catalog identifier: AEMV_v1_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AEMV_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 73649 No. of bytes in distributed program, including test data, etc.: 1334251 Distribution format: tar.gz Programming language: C++, CUDA. Computer: Linux platforms with a NVidia CUDA enabled GPU (Compute Capability 1.3 or higher), C++ compiler, NVCC (The CUDA Compiler Driver). Operating system: Linux. RAM: 2 GB Classification: 1.5. External routines: OpenGL Utility Toolkit development files, NVidia CUDA Toolkit 3.2, Lua5.2 Nature of problem: Ray tracing in four-dimensional Lorentzian spacetimes. Solution method: Numerical integration of light rays, GPU-based parallel programming using CUDA, 3D

  7. KARAT-LAMBDA - frequency dependent ray-traced troposphere delays for space applications

    NASA Astrophysics Data System (ADS)

    Hobiger, Thomas; Baron, Philippe

    2014-05-01

    Space-geodetic microwave techniques work under the assumption that the only dispersive, i.e. frequency dependent delay contribution is caused by the ionosphere. In general, the refractivity, even for the troposphere, is a complex quantity which can be denoted as N = N0 + (N'(f) + i N''(f)) where N0 is a frequency independent term, and N'(f) and N''(f) represent the complex frequency dependence. Thereby, the imaginary part can be used to derive the loss of energy (absorption) and the real part can be assigned to the changes in the propagation velocity (refraction) and thus describes the delay of an electromagnetic wave which propagates through that medium. Although the frequency dependent delay contribution appears to be of small order, one has to consider that signals are propagating through few kilometers of troposphere at high elevations to hundredths of kilometers at low elevations. Therefore, the Kashima Ray-Tracing package (Hobiger et al., 2008) has been modified (and named KARAT-LAMBDA) to enable the consideration of a frequency dependent refractivity. By using this tool, it was studied if and to which extent future space geodetic instruments are affected from dispersive troposphere delays. Moreover, a semi-empirical correction model for the microwave link of the Atomic Clock Ensemble in Space (ACES) has been developed, based on ray-tracing calculations with KARAT-LAMBDA. The proposed model (Hobiger et al., 2013) has been tested with simulated ISS overflights at different potential ACES ground station sites and it could be demonstrated that this model is capable to remove biases and elevation dependent features caused by the dispersive troposphere delay difference between the up-link and down-link. References: T. Hobiger, R. Ichikawa, T. Kondo, and Y. Koyama (2008), Fast and accurate ray-tracing algorithms for real-time space geodetic applications using numerical weather models, Journal of Geophysical Research, vol. 113, iss. D203027, pp. 1-14. T. Hobiger, D

  8. Trace elements analysis in biological samples by radioisotopic x-ray fluorescence.

    PubMed

    Cesareo, R

    1976-01-01

    The X-ray fluorescence technique, induced by radioisotopic sources, provides a very simple method for the simultaneous analysis of trace elements in biological samples. For blood, serum, platelets, etc., samples of about 0.1 ml were deposited on filter paper disks, dried, and analyzed. In such a way the "thin specimen" approximation is realized, resulting in the following advantages: The X-ray intensity of a given element is a liner function of mass per unit area over several orders of magnitude. Interelement effects became negligible. The ratio of fluorescent X-rays to scattered radiation is increased. The sensitivity of the technique for elements with atomic number ranging from about 20-92 varies from some units to some tens of parts per million by weight in 100 s measuring time, by using a gas proportional counter, and from about some tenths to some parts per million by using an X-ray semiconductor detector, in a measuring time of 10(3)-10(4)s. In such a way and with the described features, the Cl, K, Ca, Fe, Cu, Zn, Br content of several speciments of blood and serum was determined. Measurements were further carried out in order to labelling blood components with stable tracers and to detect their concentration by means of the X-ray fluorescence technique. The life span of platelets was, for example, measured after labelling platelets with stable Selenocystine. The sensitivity of the XRF technique can further be enhanced by about three orders of magnitude by using a pre-enrichment step with ion-exchange resins and liquid volumes not lower than 500 ml. Urine analyses have been carried in such a way, and copper in about 20 ml serum after selective extraction. PMID:1017430

  9. On self-consistent ray-tracing and Fokker--Planck modeling of the hard x-ray emission during lower-hybrid current drive in tokamaks

    SciTech Connect

    Bizarro, J.P.; Peysson, Y.; Bonoli, P.T.; Carrasco, J.; de Wit, T.D.; Fuchs, V.; Hoang, G.T.; Litaudon, X.; Moreau, D.; Pocheau, C.; Shkarofsky, I.P. )

    1993-09-01

    A detailed investigation is presented on the ability of combined ray-tracing and Fokker--Planck calculations to predict the hard x-ray (HXR) emission during lower-hybrid (LH) current drive in tokamaks when toroidally induced ray stochasticity is important. A large number of rays is used and the electron distribution function is obtained by self-consistently iterating the appropriate power deposition and Fokker--Planck calculations. It is shown that effects due to radial diffusion of suprathermal electrons and to radiation scattering by the inner wall can be significant. The experimentally observed features of the HXR emission are fairly well predicted, thus confirming that combined ray-tracing and Fokker--Planck codes are capable of correctly modeling the physics of LH current drive in tokamaks.

  10. An x-ray microprobe beam line for trace element analysis

    SciTech Connect

    Gordon, B.M.; Hanson, A.L.; Jones, K.W.; Kwiatek, W.M.; Long, G.J.; Pounds, J.G.; Schidlovsky, G.; Spanne, P.; Rivers, M.L.; Sutton, S.R.

    1987-01-01

    The application of synchrotron radiation to an x-ray microprobe for trace element analysis is a complementary and natural extension of existing microprobe techniques using electrons, protons, and heavier ions as excitation sources for x-ray fluorescence. The ability to focus charged particles leads to electron microprobes with spatial resolutions in the sub-micrometer range and down to 100 ppM detection limits and proton microprobes with micrometer resolution and ppM detection limits. The characteristics of synchrotron radiation that prove useful for microprobe analysis include a broad and continuous energy spectrum, a relatively small amount of radiation damage compared to that deposited by charged particles, a highly polarized source which reduces background scattered radiation in an appropriate counting geometry, and a small vertical divergence angle of approx.0.2 mrad which allows for focussing of the light beam into a small spot with high flux. The features of a dedicated x-ray microprobe beam line developed at the National Synchrotron Light Source (NSLS) are described. 4 refs., 3 figs.

  11. Mapping gray-scale image to 3D surface scanning data by ray tracing

    NASA Astrophysics Data System (ADS)

    Li, Peng; Jones, Peter R. M.

    1997-03-01

    The extraction and location of feature points from range imaging is an important but difficult task in machine vision based measurement systems. There exist some feature points which are not able to be detected from pure geometric characteristics, particularly in those measurement tasks related to the human body. The Loughborough Anthropometric Shadow Scanner (LASS) is a whole body surface scanner based on structured light technique. Certain applications of LASS require accurate location of anthropometric landmarks from the scanned data. This is sometimes impossible from existing raw data because some landmarks do not appear in the scanned data. Identification of these landmarks has to resort to surface texture of the scanned object. Modifications to LASS were made to allow gray-scale images to be captured before or after the object was scanned. Two-dimensional gray-scale image must be mapped to the scanned data to acquire the 3D coordinates of a landmark. The method to map 2D images to the scanned data is based on the colinearity conditions and ray-tracing method. If the camera center and image coordinates are known, the corresponding object point must lie on a ray starting from the camera center and connecting to the image coordinate. By intersecting the ray with the scanned surface of the object, the 3D coordinates of a point can be solved. Experimentation has demonstrated the feasibility of the method.

  12. Determination of minor and trace elements in kidney stones by x-ray fluorescence analysis

    NASA Astrophysics Data System (ADS)

    Srivastava, Anjali; Heisinger, Brianne J.; Sinha, Vaibhav; Lee, Hyong-Koo; Liu, Xin; Qu, Mingliang; Duan, Xinhui; Leng, Shuai; McCollough, Cynthia H.

    2014-03-01

    The determination of accurate material composition of a kidney stone is crucial for understanding the formation of the kidney stone as well as for preventive therapeutic strategies. Radiations probing instrumental activation analysis techniques are excellent tools for identification of involved materials present in the kidney stone. In particular, x-ray fluorescence (XRF) can be very useful for the determination of minor and trace materials in the kidney stone. The X-ray fluorescence measurements were performed at the Radiation Measurements and Spectroscopy Laboratory (RMSL) of department of nuclear engineering of Missouri University of Science and Technology and different kidney stones were acquired from the Mayo Clinic, Rochester, Minnesota. Presently, experimental studies in conjunction with analytical techniques were used to determine the exact composition of the kidney stone. A new type of experimental set-up was developed and utilized for XRF analysis of the kidney stone. The correlation of applied radiation source intensity, emission of X-ray spectrum from involving elements and absorption coefficient characteristics were analyzed. To verify the experimental results with analytical calculation, several sets of kidney stones were analyzed using XRF technique. The elements which were identified from this techniques are Silver (Ag), Arsenic (As), Bromine (Br), Chromium (Cr), Copper (Cu), Gallium (Ga), Germanium (Ge), Molybdenum (Mo), Niobium (Nb), Rubidium (Rb), Selenium (Se), Strontium (Sr), Yttrium (Y), Zirconium (Zr). This paper presents a new approach for exact detection of accurate material composition of kidney stone materials using XRF instrumental activation analysis technique.

  13. Trace element abundances in single presolar silicon carbide grains by synchrotron X-ray fluorescence

    NASA Astrophysics Data System (ADS)

    Kashiv, Yoav

    2004-12-01

    Synchrotron x-ray fluorescence (SXRF) was applied to the study of presolar grains for the first time in this study. 41 single SiC grains of the KJF size fraction (mass-weighted median size of 1.86 μm) from the Murchison (CM2) Meteorite were analyzed. The absolute abundances of the following elements were determined (not every element in every grain): S, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Sr, Y, Zr, Nb, Mo, Ru, Os, Ir and Pt (underlined elements were detected here for the first time in single grains). There is good agreement between the heavier trace element abundances in the grains and s-process nucleosynthesis calculations. It suggests that smaller 13C pocket sizes are needed in the parent stars, a free parameter in the stellar models, than is deduced from isotopic analyses of s-, and s-mainly, elements, such as Zr and Mo. In addition, the data confirms the radiogenic nature of the Nb in the grains, due to the in situ decay of 93Zr (t 1/2 = 1.5 × 106 year). The data suggest that the trace elements condensed into the host SiC grains by a combination of condensation in solid solution and incorporation of subgrains. It seems that many of the trace elements reside mainly in subgrains of two solid solution: (1)a TiC based solid solution, and (2)a Mo-Ru carbide based solid solution. The presence of subgrains of an Fe-Ni alloy solid solution is suggested as well. Subgrains of all 3 solid solutions were observed previously in presolar graphite grains.* *This dissertation is a compound document (contains both a paper copy and a CD as part of the dissertation). The CD requires the following system requirements: Adobe Acrobat.

  14. Total reflection X-ray fluorescence analysis of trace-elements in candies marketed in Mexico

    NASA Astrophysics Data System (ADS)

    Martinez, T.; Lartigue, J.; Zarazua, G.; Avila-Perez, P.; Navarrete, M.; Tejeda, S.

    2010-06-01

    Trace metals concentrations in food are significant for nutrition, due either to their nature or toxicity. Sweets, including chewing gum and candies, are not exactly a food, but they usually are unwearied consumed by children, the most vulnerable age-group to any kind of metal contamination in the food chain. The presence of relatively high concentrations of heavy metals such as Lead elicits concern since children are highly susceptible to heavy metals poisoning. Trace-metals concentrations were determined for six different flavors of a Mexican candy by means of Total X-ray Fluorescence Spectrometry. Triplicate samples of the various candy's flavours (strawberry, pineapple, lemon, blackberry, orange and chilli) were digested in 8 mL of a mix of supra-pure HNO 3 and H 2O 2 (6 mL: 2 mL) in a microwave oven MARS-X. Results show the presence of essential and toxic elements such as Ti, Cr, Mn, Fe, Ni, Cu, Zn, Br, Rb, Sr, and Pb. All metal concentrations were higher and significantly different ( α = 0.05) in chilli candy, compared to other candy flavours. Lead concentration fluctuated in the range of 0.102 to 0.342 μg g - 1 . A discussion about risk consumption and concentration allowed by Mexican and International Norms is made. As a part of the Quality Control Program, a NIST standard of "Citrus Leaves" and a blank were treated in the same way.

  15. Trace element cartography of Globigerinoides ruber shells using particle-induced X-ray emission

    NASA Astrophysics Data System (ADS)

    Gehlen, M.; Bassinot, F.; Beck, L.; Khodja, H.

    2004-12-01

    Micro particle-induced X-ray emission (PIXE) is a nondestructive elemental analysis technique that can be used to map the distribution of elements with a spatial resolution of ±4 μm2 and a penetration depth of ±2 μm in a calcite matrix. To test its potential to improve our understanding of trace element distribution in foraminifera shells, we mapped the Mg distribution across individual chambers of the planktonic species Globigerinoides ruber. G. ruber shells were picked from equatorial Atlantic surface sediments (Sierra Leone Rise). They ranged from well-preserved to heavily dissolved tests. The mapping of trace elements across test chambers made it possible to discriminate between variability inherent to the shell material and heterogeneity linked to contaminant phases. Contaminating mineral phases were characterized by high Mg concentrations (Mg/Ca = 19.7 mmol/mol) and high levels of Si, Al, and Fe. Mg/Ca values of well-preserved shells ranged from 3.9 to 4.5 mmol/mol. The Mg to Ca ratios of partially dissolved shells varied between 1.8 and 3.4 mmol/mol between outer and inner chambers. Low and homogeneous Mg/Ca values of 2.0 and 2.3 mmol/mol were determined for chambers of a severely dissolved test.

  16. Glucose sensing using the Brewster reflection: polarimetric ray-tracing based upon an anatomical eye model

    NASA Astrophysics Data System (ADS)

    Bockle, Stefan; Rovati, Luigi; Ansari, Rafat R.

    2003-07-01

    In this paper we present theoretical analysis to support the polarimetric approach for glucose detection in the human eye applying Brewster reflection off the ocular lens. The theoretical eye model of Navarro, which is based upon anatomical data, was used to perform ray-tracing, whereas the electromagnetic and polarization parameters of light propagation through the eye-media were calculated. The errors in glucose concentration determination due to refraction and deviation from the ideal optical path were calculated under different conditions. Effects of using incident linearly and circularly polarized light and variation of intersection condition of the incoming light beam with the anterior corneal surface were taken into consideration. Calculations were performed for a wide spectral range by applying dispersion curves for the eye-media. These simulations show the potential and the limits of the proposed optical approach.

  17. Polarization property analysis of a periscopic scanner with three-dimensional polarization ray-tracing calculus.

    PubMed

    Yang, Yufei; Yan, Changxiang

    2016-02-20

    The polarization properties of a two-axis periscopic optical scanner constituted by a pair of rotating planar mirrors have been studied by using the three-dimensional polarization ray-tracing matrix method. The separate and cumulative matrices that define the transformation of the polarization state are obtained and expressed in terms of the rotation angles of two mirrors. The variations of diattenuation and retardance are investigated and graphically shown as functions of the rotation angles. On this basis, a further investigation about the cumulative polarization aberrations of three different metal-coated periscopic scanners is accomplished. Finally, the output polarization states of the three metal-coated scanners are calculated with the input beam of the arbitrary polarization states, and the results show that aluminum film is more appropriate than gold film or silver film for the polarization-maintaining periscopic scanner. PMID:26906587

  18. Introducing GAMER: A fast and accurate method for ray-tracing galaxies using procedural noise

    SciTech Connect

    Groeneboom, N. E.; Dahle, H.

    2014-03-10

    We developed a novel approach for fast and accurate ray-tracing of galaxies using procedural noise fields. Our method allows for efficient and realistic rendering of synthetic galaxy morphologies, where individual components such as the bulge, disk, stars, and dust can be synthesized in different wavelengths. These components follow empirically motivated overall intensity profiles but contain an additional procedural noise component that gives rise to complex natural patterns that mimic interstellar dust and star-forming regions. These patterns produce more realistic-looking galaxy images than using analytical expressions alone. The method is fully parallelized and creates accurate high- and low- resolution images that can be used, for example, in codes simulating strong and weak gravitational lensing. In addition to having a user-friendly graphical user interface, the C++ software package GAMER is easy to implement into an existing code.

  19. Simulation of radiation damping in rings, using stepwise ray-tracing methods

    NASA Astrophysics Data System (ADS)

    Méot, F.

    2015-06-01

    The ray-tracing code Zgoubi computes particle trajectories in arbitrary magnetic and/or electric field maps or analytical field models. It includes a built-in fitting procedure, spin tracking, many Monte Carlo processes. The accuracy of the integration method makes it an efficient tool for multi-turn tracking in periodic machines. Energy loss by synchrotron radiation, based on Monte Carlo techniques, had been introduced in Zgoubi in the early 2000s for studies regarding the linear collider beam delivery system. However, only recently has this Monte Carlo tool been used for systematic beam dynamics and spin diffusion studies in rings, including the eRHIC electron-ion collider project at the Brookhaven National Laboratory. Some beam dynamics aspects of this recent use of Zgoubi capabilities, including considerations of accuracy as well as further benchmarking in the presence of synchrotron radiation in rings, are reported here.

  20. Traz - An Interactive Ray-Tracing Computer Program Integrated With A Solid-Modeling CAD System

    NASA Astrophysics Data System (ADS)

    Dolan, Ariel

    1986-02-01

    The combination of an optical ray-tracing program with a solid modeling C.A.D. (computer-aided-design) system creates a very flexible tool for optical system analysis and evaluation. The program uses the CAD data-structure and user-friendly menus for creation, manipulation and visualization of the optical system. Furthermore, it is capable of dealing with problems which are impossible or difficult to handle by existing optical design programs, such as calculations of three-dimensional sensitivities, multiple reflections, multiple-surface apertures, specular stray radiation, image rotation and complex-prism design. It can also be used as an efficient tool for error-budget and error-analysis, and can be fully interfaced with a finite-elements analysis program, thus enabling the evaluation of the effects of mechanical or thermal loads on the optical performance.

  1. Simulation of radiation damping in rings, using stepwise ray-tracing methods

    DOE PAGESBeta

    Meot, F.

    2015-06-26

    The ray-tracing code Zgoubi computes particle trajectories in arbitrary magnetic and/or electric field maps or analytical field models. It includes a built-in fitting procedure, spin tracking many Monte Carlo processes. The accuracy of the integration method makes it an efficient tool for multi-turn tracking in periodic machines. Energy loss by synchrotron radiation, based on Monte Carlo techniques, had been introduced in Zgoubi in the early 2000s for studies regarding the linear collider beam delivery system. However, only recently has this Monte Carlo tool been used for systematic beam dynamics and spin diffusion studies in rings, including eRHIC electron-ion collider projectmore » at the Brookhaven National Laboratory. Some beam dynamics aspects of this recent use of Zgoubi capabilities, including considerations of accuracy as well as further benchmarking in the presence of synchrotron radiation in rings, are reported here.« less

  2. Simulation of radiation damping in rings, using stepwise ray-tracing methods

    SciTech Connect

    Meot, F.

    2015-06-26

    The ray-tracing code Zgoubi computes particle trajectories in arbitrary magnetic and/or electric field maps or analytical field models. It includes a built-in fitting procedure, spin tracking many Monte Carlo processes. The accuracy of the integration method makes it an efficient tool for multi-turn tracking in periodic machines. Energy loss by synchrotron radiation, based on Monte Carlo techniques, had been introduced in Zgoubi in the early 2000s for studies regarding the linear collider beam delivery system. However, only recently has this Monte Carlo tool been used for systematic beam dynamics and spin diffusion studies in rings, including eRHIC electron-ion collider project at the Brookhaven National Laboratory. Some beam dynamics aspects of this recent use of Zgoubi capabilities, including considerations of accuracy as well as further benchmarking in the presence of synchrotron radiation in rings, are reported here.

  3. A comparison of partially specular radiosity and ray tracing for room acoustics modeling

    NASA Astrophysics Data System (ADS)

    Beamer, C. Walter; Muehleisen, Ralph T.

    2005-04-01

    Partially specular (PS) radiosity is an extended form of the general radiosity method. Acoustic radiosity is a form of bulk transfer of radiant acoustic energy. This bulk transfer is accomplished through a system of energy balance equations that relate the bulk energy transfer of each surface in the system to all other surfaces in the system. Until now acoustic radiosity has been limited to modeling only diffuse surface reflection. The new PS acoustic radiosity method can model all real surface types, diffuse, specular and everything in between. PS acoustic radiosity also models all real source types and distributions, not just point sources. The results of the PS acoustic radiosity method are compared to those of well known ray tracing programs. [Work supported by NSF.

  4. Sun-, Earth- and Moon-integrated simulation ray tracing for observation from space using ASAP

    NASA Astrophysics Data System (ADS)

    Breault, Robert P.; Kim, Sug-Whan; Yang, Seul-Ki; Ryu, Dongok

    2014-09-01

    The Space Optics Laboratory at Yonsei University, Korea, in cooperation with Breault Research Organization (BRO) in Tucson, Arizona, have invested significant research and development efforts into creating large scale ray tracing techniques for simulating "reflected" light from the earth with an artificial satellite. This presentation describes a complex model that combines the sun, the earth and an orbiting optical instrument combined into a real scale nonsequential ray tracing computation using BRO's Advanced Systems Analysis Program, ASAP®. The Sun is simulated as a spherically emitting light source of 695,500 km in diameter. The earth also is simulated as a sphere with its characteristics defined as target objects to be observed and defined with appropriate optical properties. They include the atmosphere, land and ocean elements, each having distinctive optical properties expressed by single or combined characteristics of refraction, reflection and scattering. The current embodiment has an atmospheric model consisting of 33 optical layers, a land model with 6 different albedos and the ocean simulated with sun glint characteristics. A space-based optical instrument, with an actual opto-mechanical prescription, is defined in an orbit of several hundreds to thousands of miles in altitude above the earth's surface. The model allows for almost simultaneous evaluations of the imaging and radiometric performances of the instrument. Several real-life application results are reported suggesting that this simulation approach not only provides valuable information that can greatly improve the space optical instrument performance but also provides a simulation tool for scientists to evaluate all phases of a space mission.

  5. The P velocity within the Tonga Benioff Zone determined from traced rays and observations

    NASA Astrophysics Data System (ADS)

    Huppert, Lawrence N.; Frohlich, Cliff

    1981-05-01

    P waves with travel time residuals between 0 s and -12 s are observed at regional stations in Samoa (AFI) and Raoul Island (RAO) for 39 earthquakes in Tonga with focal depths between 70 km and 300 km. These anomalously large residuals apparently are produced because seismic phases travel along the strike of the Tonga Benioff zone within the high-velocity subducted lithosphere for up to 1200 km before arriving at AFI and RAO. To eliminate erroneous residuals caused by poor event locations, we selected 11 stations and reread the available P times at these stations for the 39 events. These arrivals and (pP-P) intervals were used to relocate the events using a variant of the joint hypocenter determination method. Then the pattern of residuals at AFI and RAO (not used in the relocation) was compared to the pattern of residuals expected for various models of the subducted lithosphere, as determined by ray tracing. The observed pattern of residuals at AFI is consistent with the ray-traced models if some of the first arrivals are produced by rays traveling directly along the strike of the subducting lithosphere, and if others are produced by rays which reflect once off the upper surface of the subducting lithosphere before arriving at AFI. The observed residuals can be explained by a model where the P velocity in the subducted lithosphere is 8% higher than the velocity in the Herrin model. The residuals are fit even better by a layered slab model in which the seismic velocity is about 6% higher than the Herrin velocity at the upper surface of the subducted lithosphere and about 9% higher at the bottom of the slab. These velocity contrasts could be produced if the temperature in the slab was 700°C cooler than the surrounding mantle, and if there were no partially melted material within the slab. The existence of these anomalously large residuals suggests that the high velocity region in the upper 300 km of the mantle beneath Tonga must be fairly continuous over distances

  6. Micro-trace fossils reveal pervasive reworking of Pliocene sapropels by low-oxygen-adapted benthic meiofauna

    NASA Astrophysics Data System (ADS)

    Löhr, S. C.; Kennedy, M. J.

    2015-03-01

    Animal burrowers leave an indelible signature on the sedimentary record in most marine environments, with the seeming exception of low-oxygen environments. In modern sedimentary settings, however, sub-millimetre-sized benthic animals (meiofauna) are adapted to low oxygen and even sulfidic conditions. Almost nothing is known about their impact on ancient marine sediments because they leave few recognizable traces. Here we show, in classic Pliocene-aged anoxic facies from the Mediterranean, the first reported trace fossil evidence of meiofaunal activity and its relation to changing oxygenation. A novel approach utilizing electron imaging of ion-polished samples shows that meiofauna pervasively reworked sediment under oxygen-depleted conditions that excluded macrofauna, fragmenting organic laminae and emplacing 15- to 70-μm-diameter faecal pellets without macroscopically influencing the fabric. The extent of reworking raises the question: how pervasively altered are other sediments presently assumed to lack animal influence and how far into the geological record does this influence extend?

  7. A ray tracing study of shock leakage in a model supersonic jet

    NASA Astrophysics Data System (ADS)

    Shariff, Karim; Manning, Ted A.

    2013-07-01

    Recent work has described screech noise from a supersonic jet as being due to leakage of a wave that is otherwise trapped in the jet's interior. In that work, the simplest of many techniques used is ray tracing for a single shear-layer modeled as a row of Stuart vortices. In the present work, a lower row of vortices is added to form a plane jet. Instead of plotting ray paths, a technique of visualization analogous to streaklines is used that better corresponds to instantaneous density fields as observed, for instance, by the Schlieren method. This produces striking images that show leakage of waves at each internal reflection resulting in a row of acoustic sources as envisioned since the 1950s. However, the sources are not isotropic and each has a zone of silence in the downstream direction. Leakage creates a fold in the wave pattern internal to the jet which leads to fine scale features. Reported experiments have also observed fine scale features (described as splitting) in the shock-cell pattern; they may be related to those observed here. Internally reflected rays also undergo a diffusive process as they propagate down the jet. In particular, each successive internal reflection at an unsteady shear-layer scatters rays along a wider range of wave angle and makes them more susceptible to leakage at the next reflection. It also causes more downstream directivity for the more downstream sources. An important result is that as the Mach number Mj is varied, maxima in leakage rate and mean acoustic amplitude occur at (near) resonances between the Mach-wave and shear-layer periods. Maxima in sound pressure level versus Mj have also been reported for laboratory round jets. Finally, as the shear-layer thickness is increased, a minimum in the rate of leakage (correlated with a minimum in radiation amplitude) occurs due to the competing effects of increased shear-layer penetration versus reduced eddy passage frequency.

  8. Proposed additions to the SHADOW ray-tracing code for general-asymmetric perfect-crystal optics

    SciTech Connect

    Blasdell, R.C.; Macrander, A.T.

    1993-12-01

    The dynamical theory of the diffraction of X-rays from perfect crystals is traditionally expressed in terms of Maxwell`s equations using a semi-classical theory originally due to Ewald and von Laue. Combining the work of Batterman and Cole, Caticha and Caticha-Ellis, and Zachariasen, a formalism is obtained that treats the general asymmetric, thick and thin crystal, Laue and Bragg cases within the second order dispersion surface approximation. The authors have implemented this formalism with thick Bragg crystal E-field boundary value conditions in several routines they have added to one of the Advanced Photon Source (APS) versions of the SHADOW ray-tracing code in order to provide the ability to ray trace inclined double-crystal monochromators and high-resolution backscattering analyzers. These additions have been submitted to the University of Wisconsin Center for X-Ray Lithography for consideration for inclusion in the next version of SHADOW.

  9. Kashima RAy-Tracing Service (KARATS) for high accurate GNSS positioning

    NASA Astrophysics Data System (ADS)

    Ichikawa, R.; Hobiger, T.; Hasegawa, S.; Tsutsumi, M.; Koyama, Y.; Kondo, T.

    2010-12-01

    Radio signal delays associated with the neutral atmosphere are one of the major error sources of space geodesy such as GPS, GLONASS, GALILEO, VLBI, In-SAR measurements. We have developed a state-of-art tool to estimate the atmospheric path delays by ray-tracing through JMA meso-scale analysis (MANAL data) data. The tools, which we have named 'KAshima RAytracing Tools (KARAT)', are capable of calculating total slant delays and ray-bending angles considering real atmospheric phenomena. Numerical weather models such as MANAL data have undergone a significant improvement of accuracy and spatial resolution, which makes it feasible to utilize them for the correction of atmosphere excess path delays. In the previous studies for evaluating KARAT performance, the KARAT solutions are slightly better than the solutions using VMF1 and GMF with linear gradient model for horizontal and height positions. Based on these results we have started the web-based online service, 'KAshima RAytracing Service (KARATS)' for providing the atmospheric delay correction of RINEX files on Jan 27th, 2010. The KARATS receives user's RINEX data via a proper web site (http://vps.nict.go.jp/karats/index.html) and processes user's data files using KARAT for reducing atmospheric slant delays. The reduced RINEX files are archived in the specific directory for each user on the KARATS server. Once the processing is finished the information of data archive is sent privately via email to each user. If user want to process a large amount of data files, user can prepare own server which archives them. The KARATS can get these files from the user's server using GNU ¥emph{wget} and performs ray-traced corrections. We will present a brief status of the KARATS and summarize first experiences gained after this service went operational in December 2009. In addition, we will also demonstrate the newest KARAT performance based on the 5km MANAL data which has been operational from April 7th, 2009 and an outlook on

  10. The forms of trace metals in an Illinois basin coal by x-ray absorption fine structure spectroscopy

    USGS Publications Warehouse

    Chou, I.-Ming; Bruinius, J.A.; Lytle, J.M.; Ruch, R.R.; Huggins, Frank E.; Huffman, G.P.; Ho, K.K.

    1997-01-01

    Utilities burning Illinois coals currently do not consider trace elements in their flue gas emissions. After the US EPA completes an investigation on trace elements, however, this may change and flue gas emission standards may be established. The mode of occurrence of a trace element may determine its cleanability and Hue gas emission potential. X-ray Absorption Fine Structure (XAFS) is a spectroscopic technique that can differentiate the mode of occurrence of an element, even at the low concentrations that trace elements are found in coal. This is principally accomplished by comparing the XAFS spectra of a coal to a database of reference sample spectra. This study evaluated the technique as a potential tool to examine six trace elements in an Illinois #6 coal. For the elements As and Zn, the present database provides a definitive interpretation on their mode of occurrence. For the elements Ti, V, Cr, and Mn the database of XAFS spectra of trace elements in coal was still too limited to allow a definitive interpretation. The data obtained on these elements, however, was sufficient to rule out several of the mineralogical possibilities that have been suggested previously. The results indicate that XAFS is a promising technique for the study of trace elements in coal.

  11. A comparison on initial-value ray tracing and fast marching eikonal solver for VTI traveltime computing

    NASA Astrophysics Data System (ADS)

    Moussavi Alashloo, S. Y.; Ghosh, D. P.; Bashir, Y.; Yusoff, W. I. Wan

    2016-02-01

    The Earth's subsurface is an anisotropic medium where the velocity of seismic waves alters in different propagation angles. Omitting anisotropy in seismic imaging not only brings mis-positioning of migrated dipping events but also fails to retain dipping energy during dip-moveout. To account for the efficacy of seismic anisotropy in imaging, an anisotropic wave equation must be engaged. Seismic traveltime computing is fundamental of both Kirchhoff migration and tomography algorithms. Two main categories of traveltime computing involve traditional ray tracing methods and finite difference eikonal solvers. In this study, we present two techniques of initial-value ray tracing and fast marching eikonal solver in isotropic and vertical transverse isotropy (VTI) media, and a comparison between results is demonstrated for more evaluation. Although the ray tracing approach is able to compute multiple arrivals with great precision, the eikonal solver is faster and more robust for traveltime computation. Since the ray tracing result is not a deterministic solution and it depends on the initial circumstance, employing the eikonal solver method are more preferred and suggested.

  12. ROBAST: Development of a ROOT-based ray-tracing library for cosmic-ray telescopes and its applications in the Cherenkov Telescope Array

    NASA Astrophysics Data System (ADS)

    Okumura, Akira; Noda, Koji; Rulten, Cameron

    2016-03-01

    We have developed a non-sequential ray-tracing simulation library, ROOT-basedsimulatorforraytracing (ROBAST), which is aimed to be widely used in optical simulations of cosmic-ray (CR) and gamma-ray telescopes. The library is written in C++, and fully utilizes the geometry library of the ROOT framework. Despite the importance of optics simulations in CR experiments, no open-source software for ray-tracing simulations that can be widely used in the community has existed. To reduce the dispensable effort needed to develop multiple ray-tracing simulators by different research groups, we have successfully used ROBAST for many years to perform optics simulations for the Cherenkov Telescope Array (CTA). Among the six proposed telescope designs for CTA, ROBAST is currently used for three telescopes: a Schwarzschild-Couder (SC) medium-sized telescope, one of SC small-sized telescopes, and a large-sized telescope (LST). ROBAST is also used for the simulation and development of hexagonal light concentrators proposed for the LST focal plane. Making full use of the ROOT geometry library with additional ROBAST classes, we are able to build the complex optics geometries typically used in CR experiments and ground-based gamma-ray telescopes. We introduce ROBAST and its features developed for CR experiments, and show several successful applications for CTA.

  13. The Use of Pro/Engineer CAD Software and Fishbowl Tool Kit in Ray-tracing Analysis

    NASA Technical Reports Server (NTRS)

    Nounu, Hatem N.; Kim, Myung-Hee Y.; Ponomarev, Artem L.; Cucinotta, Francis A.

    2009-01-01

    This document is designed as a manual for a user who wants to operate the Pro/ENGINEER (ProE) Wildfire 3.0 with the NASA Space Radiation Program's (SRP) custom-designed Toolkit, called 'Fishbowl', for the ray tracing of complex spacecraft geometries given by a ProE CAD model. The analysis of spacecraft geometry through ray tracing is a vital part in the calculation of health risks from space radiation. Space radiation poses severe risks of cancer, degenerative diseases and acute radiation sickness during long-term exploration missions, and shielding optimization is an important component in the application of radiation risk models. Ray tracing is a technique in which 3-dimensional (3D) vehicle geometry can be represented as the input for the space radiation transport code and subsequent risk calculations. In ray tracing a certain number of rays (on the order of 1000) are used to calculate the equivalent thickness, say of aluminum, of the spacecraft geometry seen at a point of interest called the dose point. The rays originate at the dose point and terminate at a homogenously distributed set of points lying on a sphere that circumscribes the spacecraft and that has its center at the dose point. The distance a ray traverses in each material is converted to aluminum or other user-selected equivalent thickness. Then all equivalent thicknesses are summed up for each ray. Since each ray points to a direction, the aluminum equivalent of each ray represents the shielding that the geometry provides to the dose point from that particular direction. This manual will first list for the user the contact information for help in installing ProE and Fishbowl in addition to notes on the platform support and system requirements information. Second, the document will show the user how to use the software to ray trace a Pro/E-designed 3-D assembly and will serve later as a reference for troubleshooting. The user is assumed to have previous knowledge of ProE and CAD modeling.

  14. Accounting for partiality in serial crystallography using ray-tracing principles

    PubMed Central

    Kroon-Batenburg, Loes M. J.; Schreurs, Antoine M. M.; Ravelli, Raimond B. G.; Gros, Piet

    2015-01-01

    Serial crystallography generates ‘still’ diffraction data sets that are composed of single diffraction images obtained from a large number of crystals arbitrarily oriented in the X-ray beam. Estimation of the reflection partialities, which accounts for the expected observed fractions of diffraction intensities, has so far been problematic. In this paper, a method is derived for modelling the partialities by making use of the ray-tracing diffraction-integration method EVAL. The method estimates partialities based on crystal mosaicity, beam divergence, wavelength dispersion, crystal size and the interference function, accounting for crystallite size. It is shown that modelling of each reflection by a distribution of interference-function weighted rays yields a ‘still’ Lorentz factor. Still data are compared with a conventional rotation data set collected from a single lysozyme crystal. Overall, the presented still integration method improves the data quality markedly. The R factor of the still data compared with the rotation data decreases from 26% using a Monte Carlo approach to 12% after applying the Lorentz correction, to 5.3% when estimating partialities by EVAL and finally to 4.7% after post-refinement. The merging R int factor of the still data improves from 105 to 56% but remains high. This suggests that the accuracy of the model parameters could be further improved. However, with a multiplicity of around 40 and an R int of ∼50% the merged still data approximate the quality of the rotation data. The presented integration method suitably accounts for the partiality of the observed intensities in still diffraction data, which is a critical step to improve data quality in serial crystallography. PMID:26327370

  15. Accounting for partiality in serial crystallography using ray-tracing principles.

    PubMed

    Kroon-Batenburg, Loes M J; Schreurs, Antoine M M; Ravelli, Raimond B G; Gros, Piet

    2015-09-01

    Serial crystallography generates `still' diffraction data sets that are composed of single diffraction images obtained from a large number of crystals arbitrarily oriented in the X-ray beam. Estimation of the reflection partialities, which accounts for the expected observed fractions of diffraction intensities, has so far been problematic. In this paper, a method is derived for modelling the partialities by making use of the ray-tracing diffraction-integration method EVAL. The method estimates partialities based on crystal mosaicity, beam divergence, wavelength dispersion, crystal size and the interference function, accounting for crystallite size. It is shown that modelling of each reflection by a distribution of interference-function weighted rays yields a `still' Lorentz factor. Still data are compared with a conventional rotation data set collected from a single lysozyme crystal. Overall, the presented still integration method improves the data quality markedly. The R factor of the still data compared with the rotation data decreases from 26% using a Monte Carlo approach to 12% after applying the Lorentz correction, to 5.3% when estimating partialities by EVAL and finally to 4.7% after post-refinement. The merging R(int) factor of the still data improves from 105 to 56% but remains high. This suggests that the accuracy of the model parameters could be further improved. However, with a multiplicity of around 40 and an R(int) of ∼50% the merged still data approximate the quality of the rotation data. The presented integration method suitably accounts for the partiality of the observed intensities in still diffraction data, which is a critical step to improve data quality in serial crystallography. PMID:26327370

  16. Quantifying trace elements in individual aquatic protist cells with a synchrotron X-ray fluorescence microprobe.

    PubMed

    Twining, Benjamin S; Baines, Stephen B; Fisher, Nicholas S; Maser, Jörg; Vogt, Stefan; Jacobsen, Chris; Tovar-Sanchez, Antonio; Sañudo-Wilhelmy, Sergio A

    2003-08-01

    The study of trace metal cycling by aquatic protists is limited by current analytical techniques. Standard "bulk" element analysis techniques that rely on physical separations to concentrate cells for analysis cannot separate cells from co-occurring detrital material or other cells of differing taxonomy or trophic function. Here we demonstrate the ability of a synchrotron-based X-ray fluorescence (SXRF) microprobe to quantify the elements Si, Mn, Fe, Ni, and Zn in individual aquatic protist cells. This technique distinguishes between different types of cells in an assemblage and between cells and other particulate matter. Under typical operating conditions, the minimum detection limits are 7.0 x 10(-16) mol microm(-2) for Si and between 5.0 x 10(-20) and 3.9 x 10(-19) mol microm(-2) for Mn, Fe, Ni, and Zn; this sensitivity is sufficient to detect these elements in cells from even the most pristine waters as demonstrated in phytoplankton cells collected from remote areas of the Southern Ocean. Replicate analyses of single cells produced variations of <5% for Si, Mn, Fe, and Zn and <10% for Ni. Comparative analyses of cultured phytoplankton cells generally show no significant differences in cellular metal concentrations measured with SXRF and standard bulk techniques (spectrophotometry and graphite furnace atomic absorption spectrometry). SXRF also produces two-dimensional maps of element distributions in cells, thereby providing information not available with other analytical approaches. This technique enables the accurate and precise measurement of trace metals in individual aquatic protists collected from natural environments. PMID:14572047

  17. Quantifying trace elements in individual aquatic protist cells with a synchrotron x-ray fluorescence microprobe.

    SciTech Connect

    Twining, B. S.; Baines, S. B.; Fisher, N. S.; Maser, J.; Vogt, S.; Jacobsen, C.; Tovar-Sanchez, A.; Sanudo-Wihelmy, S. A.; Experimental Facilities Division; Stony Brook Univ.

    2003-01-01

    The study of trace metal cycling by aquatic protists is limited by current analytical techniques. Standard 'bulk' element analysis techniques that rely on physical separations to concentrate cells for analysis cannot separate cells from co-occurring detrital material or other cells of differing taxonomy or trophic function. Here we demonstrate the ability of a synchrotron-based X-ray fluorescence (SXRF) microprobe to quantify the elements Si, Mn, Fe, Ni, and Zn in individual aquatic protist cells. This technique distinguishes between different types of cells in an assemblage and between cells and other particulate matter. Under typical operating conditions, the minimum detection limits are 7.0 x 10{sup -16} mol {mu}m{sup -2} for Si and between 5.0 x 10{sup -20} and 3.9 x 10{sup -19} mol {mu}m{sup -2} for Mn, Fe, Ni, and Zn; this sensitivity is sufficient to detect these elements in cells from even the most pristine waters as demonstrated in phytoplankton cells collected from remote areas of the Southern Ocean. Replicate analyses of single cells produced variations of <5% for Si, Mn, Fe, and Zn and <10% for Ni. Comparative analyses of cultured phytoplankton cells generally show no significant differences in cellular metal concentrations measured with SXRF and standard bulk techniques (spectrophotometry and graphite furnace atomic absorption spectrometry). SXRF also produces two-dimensional maps of element distributions in cells, thereby providing information not available with other analytical approaches. This technique enables the accurate and precise measurement of trace metals in individual aquatic protists collected from natural environments.

  18. Threading Dislocation Characterization and Stress Mapping Depth Profiling via Ray Tracing Technique

    NASA Astrophysics Data System (ADS)

    Zhou, Tianyi

    Zinc oxide (ZnO) has been well known as a transparent, dielectric, piezoelectric and wide band gap material. The potential capabilities have been demonstrated for a wide range of applications such as piezoelectric transducer, gas sensor, optical waveguides and transparent electrode. It could also be applied as a substrate material for GaN-based devices. However, while some applications have already been realized, issues relating to crystalline defects remain a barrier to the successful realization of several others. In this thesis, the central focus of Chapter II is to characterize threading dislocations in hydrothermal grown ZnO substrates through simulation work as well as other techniques. The goal of this study is to find the origin of threading dislocations and design strategies to mitigate their negative effects by either reducing their densities or completely eliminating them. In Chapter III, the technique of SMART (stress mapping analysis via ray tracing) is discussed in detail to measure residue stress in packaged silicon circuits. Residual stress plays an important role in the performance and lifetime of single crystal device material. There are mainly two advantages of SMART compared with other techniques: (a) all six components of the stress tensor could be evaluated; (b) it is non-destructive and no damaging trace will be left on the sample. In this study, our goal is to build a relationship between stress distribution and depth. The concept of penetration depth is critically important in this study and its value may cause great changes for real space stress distribution. A new function is applied to get better fitting curves. Data in this study is obtained from various penetration depth, which represents exponentially decaying weighted average of actual stress value or in other words this stress profile is Laplace transform of real stress profile. Mathematical procedure is described to determine real stress profile from Laplace profile. Experiment

  19. Identification of Gravity wave Sources over Tropical Latitudes Using Reverse Ray Tracing technique

    NASA Astrophysics Data System (ADS)

    Venkat Ratnam, Madineni; Pramitha, M.

    2016-07-01

    Sources and propagation characteristics of high-frequency gravity waves (GWs) observed in the mesosphere using airglow emissions from Gadanki (13.5oN, 79.2oE) and Hyderabad (17.5oN, 78.5oE) are investigated using reverse ray tracing. Wave amplitudes are also traced back, including both radiative and diffusive damping. For this a climatological model of the background atmosphere for the Gadanki region has been developed using nearly 30 years of observations available from a variety of ground based (MST radar, radiosondes, MF radar) and rocket- and satellite-borne measurements. With the reverse ray-tracing method, the source locations for wave events could be identified to be in the upper troposphere. Uncertainty in locating the terminal points of wave events in the horizontal direction is estimated to be within 50-100 km and 150-300 km for Gadanki and Hyderabad wave events, respectively. This uncertainty arises mainly due to non-consideration of the day-to-day variability in the tidal amplitudes. Interestingly, large (~9ms-1 km-1) vertical shears in the horizontal wind are noticed near the ray terminal points (at 10-12 km altitude) and are thus identified to be the source for generating the observed high phase- speed, high-frequency GWs. We also tried to identify the sources for the GWs which are observed during Indo-French campaign conducted during May 2014. Uniqueness of the present study lies in using near-real time background atmosphere data from simultaneous radiosonde and meteor radar covering both source and propagation/dissipation regions of GWs. When we searched for the sources near the terminal points, deep convection is found to be a source for these events. We also tried to identify the sources of inertia-gravity waves (IGWs) that are observed in the troposphere and lower stratosphere during different seasons using long-term (2006-2014) high resolution radiosonde observations. In general, 50% of the waves observed over this location have convection as

  20. Separating Trace Mapping and Reactive Simulatability Soundness: The Case of Adaptive Corruption

    NASA Astrophysics Data System (ADS)

    Mazaré, Laurent; Warinschi, Bogdan

    Computational soundness is the research direction that aims to translate security guarantees with respect to Dolev-Yao models into guarantees with resepect to the stronger computational models of modern cryptography. There are essentially two different approaches that aim to achieve computational soundness. One approach is based on the so-called trace mapping theorems, and one based on reactive simulatability. In a recent paper, Backes, Dürthmuth, and Küsters have shown that the stronger requirements needed for reactive simulatability-based soundness imply that a trace mapping theorem also holds. It was left as an open problem whether there exists interesting settings where the simulatability framework breaks down but mapping theorems still exist.

  1. Solar proton exposure of an ICRU sphere within a complex structure part II: Ray-trace geometry.

    PubMed

    Slaba, Tony C; Wilson, John W; Badavi, Francis F; Reddell, Brandon D; Bahadori, Amir A

    2016-06-01

    A computationally efficient 3DHZETRN code with enhanced neutron and light ion (Z ≤ 2) propagation was recently developed for complex, inhomogeneous shield geometry described by combinatorial objects. Comparisons were made between 3DHZETRN results and Monte Carlo (MC) simulations at locations within the combinatorial geometry, and it was shown that 3DHZETRN agrees with the MC codes to the extent they agree with each other. In the present report, the 3DHZETRN code is extended to enable analysis in ray-trace geometry. This latest extension enables the code to be used within current engineering design practices utilizing fully detailed vehicle and habitat geometries. Through convergence testing, it is shown that fidelity in an actual shield geometry can be maintained in the discrete ray-trace description by systematically increasing the number of discrete rays used. It is also shown that this fidelity is carried into transport procedures and resulting exposure quantities without sacrificing computational efficiency. PMID:27345204

  2. Solar proton exposure of an ICRU sphere within a complex structure part II: Ray-trace geometry

    NASA Astrophysics Data System (ADS)

    Slaba, Tony C.; Wilson, John W.; Badavi, Francis F.; Reddell, Brandon D.; Bahadori, Amir A.

    2016-06-01

    A computationally efficient 3DHZETRN code with enhanced neutron and light ion (Z ≤ 2) propagation was recently developed for complex, inhomogeneous shield geometry described by combinatorial objects. Comparisons were made between 3DHZETRN results and Monte Carlo (MC) simulations at locations within the combinatorial geometry, and it was shown that 3DHZETRN agrees with the MC codes to the extent they agree with each other. In the present report, the 3DHZETRN code is extended to enable analysis in ray-trace geometry. This latest extension enables the code to be used within current engineering design practices utilizing fully detailed vehicle and habitat geometries. Through convergence testing, it is shown that fidelity in an actual shield geometry can be maintained in the discrete ray-trace description by systematically increasing the number of discrete rays used. It is also shown that this fidelity is carried into transport procedures and resulting exposure quantities without sacrificing computational efficiency.

  3. Dynamic vacuum analysis for APS high heat flux beamline front ends using optical ray-tracing simulation methods

    SciTech Connect

    Xu, S.; Nielsen, R.W.

    1992-01-01

    The high-power and high-flux x-ray beams produced by third generation synchrotron radiation sources such as the Advanced Photon Source (APS) can cause significantly high gas desorption rates on beamline front-end components if beam missteering occurs. The effect of this gas desorption needs to be understood for dynamic vacuum analysis. To simulate beam missteering conditions, optical ray-tracing methods have been employed. The results of the ray-tracing analysis have been entered into a system-oriented vacuum program to provide dynamic vacuum calculations for determination of pumping requirements for the beamline front-ends. The APS will provide several types of synchrotron radiation sources, for example, undulators, wigglers, and bending magnets. For the purpose of this study, the wiggler source was chosen as a worst case'' scenario due to its high photon flux, high beam power, and relatively large beam cross section.

  4. Dynamic vacuum analysis for APS high heat flux beamline front ends using optical ray-tracing simulation methods

    SciTech Connect

    Xu, S.; Nielsen, R.W.

    1992-09-01

    The high-power and high-flux x-ray beams produced by third generation synchrotron radiation sources such as the Advanced Photon Source (APS) can cause significantly high gas desorption rates on beamline front-end components if beam missteering occurs. The effect of this gas desorption needs to be understood for dynamic vacuum analysis. To simulate beam missteering conditions, optical ray-tracing methods have been employed. The results of the ray-tracing analysis have been entered into a system-oriented vacuum program to provide dynamic vacuum calculations for determination of pumping requirements for the beamline front-ends. The APS will provide several types of synchrotron radiation sources, for example, undulators, wigglers, and bending magnets. For the purpose of this study, the wiggler source was chosen as a ``worst case`` scenario due to its high photon flux, high beam power, and relatively large beam cross section.

  5. Characterization of Threading Dislocations in PVT-Grown AlN Substrates via x-Ray Topography and Ray Tracing Simulation

    NASA Astrophysics Data System (ADS)

    Zhou, Tianyi; Raghothamachar, Balaji; Wu, Fangzhen; Dalmau, Rafael; Moody, Baxter; Craft, Spalding; Schlesser, Raoul; Dudley, Michael; Sitar, Zlatko

    2014-04-01

    Threading dislocations in aluminum nitride boules grown by physical vapor transport method were systematically studied via synchrotron x-ray topography (white beam and monochromatic) in conjunction with ray tracing simulations. Two major types of threading dislocations were observed in the c-axis-grown boules: threading screw dislocations (TSDs) and threading edge dislocations (TEDs) with Burgers vectors along the [0001] and directions, respectively. TSDs were typically observed in the middle of the boule while TEDs were commonly observed to aggregate into arrays along the and directions in various parts of the boule on basal plane oriented wafers. By comparison with ray tracing simulations, the absolute Burgers vectors of both TSDs and TEDs in the arrays could be unambiguously determined. TEDs comprise over 90 % of all threading dislocations observed. The relationships between TED arrays and low angle grain boundaries and their possible formation mechanisms are discussed.

  6. Novel ray tracing method for stray light suppression from ocean remote sensing measurements.

    PubMed

    Oh, Eunsong; Hong, Jinsuk; Kim, Sug-Whan; Park, Young-Je; Cho, Seong-Ick

    2016-05-16

    We developed a new integrated ray tracing (IRT) technique to analyze the stray light effect in remotely sensed images. Images acquired with the Geostationary Ocean Color Imager show a radiance level discrepancy at the slot boundary, which is suspected to be a stray light effect. To determine its cause, we developed and adjusted a novel in-orbit stray light analysis method, which consists of three simulated phases (source, target, and instrument). Each phase simulation was performed in a way that used ray information generated from the Sun and reaching the instrument detector plane efficiently. This simulation scheme enabled the construction of the real environment from the remote sensing data, with a focus on realistic phenomena. In the results, even in a cloud-free environment, a background stray light pattern was identified at the bottom of each slot. Variations in the stray light effect and its pattern according to bright target movement were simulated, with a maximum stray light ratio of 8.5841% in band 2 images. To verify the proposed method and simulation results, we compared the results with the real acquired remotely sensed image. In addition, after correcting for abnormal phenomena in specific cases, we confirmed that the stray light ratio decreased from 2.38% to 1.02% in a band 6 case, and from 1.09% to 0.35% in a band 8 case. IRT-based stray light analysis enabled clear determination of the stray light path and candidates in in-orbit circumstances, and the correction process aided recovery of the radiometric discrepancy. PMID:27409848

  7. Spatial resolution recovery utilizing multi-ray tracing and graphic processing unit in PET image reconstruction

    NASA Astrophysics Data System (ADS)

    Liang, Yicheng; Peng, Hao

    2015-02-01

    Depth-of-interaction (DOI) poses a major challenge for a PET system to achieve uniform spatial resolution across the field-of-view, particularly for small animal and organ-dedicated PET systems. In this work, we implemented an analytical method to model system matrix for resolution recovery, which was then incorporated in PET image reconstruction on a graphical processing unit platform, due to its parallel processing capacity. The method utilizes the concepts of virtual DOI layers and multi-ray tracing to calculate the coincidence detection response function for a given line-of-response. The accuracy of the proposed method was validated for a small-bore PET insert to be used for simultaneous PET/MR breast imaging. In addition, the performance comparisons were studied among the following three cases: 1) no physical DOI and no resolution modeling; 2) two physical DOI layers and no resolution modeling; and 3) no physical DOI design but with a different number of virtual DOI layers. The image quality was quantitatively evaluated in terms of spatial resolution (full-width-half-maximum and position offset), contrast recovery coefficient and noise. The results indicate that the proposed method has the potential to be used as an alternative to other physical DOI designs and achieve comparable imaging performances, while reducing detector/system design cost and complexity.

  8. Visualization of thermal lensing induced image distortion using Zemax ray tracing and BTEC thermal modeling

    NASA Astrophysics Data System (ADS)

    Towle, Erica L.; Clark, Clifton D.; Aaron, Michelle T.; Dunn, Andrew K.; Welch, Ashley J.; Thomas, Robert J.

    2013-02-01

    In recent years, several studies have been investigating the impact of thermal lensing in ocular media on the visual function. These studies have shown that when near-infrared (NIR) laser energy (1319 nm) is introduced to a human eye, the heating of the eye can be sufficient to alter the index of refraction of the media leading to transient changes in the visible wavefront through an effect known as thermal lensing, while remaining at a safe level. One of the main limitations of experimentation with human subjects, however, is the reliance on a subject's description of the effect, which can vary greatly between individuals. Therefore, a computational model was needed that could accurately represent the changes of an image as a function of changes in the index of refraction. First, to model changes in the index of refraction throughout the eye, a computational thermal propagation model was used. These data were used to generate a comprehensive ray tracing model of the human eye using Zemax ( Radiant Zemax Inc, Redmond WA) via a gradient lens surface. Using this model, several different targets have been analyzed which made it possible to calculate real-world visual acuity so that the effect of changes in the index of refraction could be related back to changes in the image of a visual scene.

  9. Effects of urban microcellular environments on ray-tracing-based coverage predictions.

    PubMed

    Liu, Zhongyu; Guo, Lixin; Guan, Xiaowei; Sun, Jiejing

    2016-09-01

    The ray-tracing (RT) algorithm, which is based on geometrical optics and the uniform theory of diffraction, has become a typical deterministic approach of studying wave-propagation characteristics. Under urban microcellular environments, the RT method highly depends on detailed environmental information. The aim of this paper is to provide help in selecting the appropriate level of accuracy required in building databases to achieve good tradeoffs between database costs and prediction accuracy. After familiarization with the operating procedures of the RT-based prediction model, this study focuses on the effect of errors in environmental information on prediction results. The environmental information consists of two parts, namely, geometric and electrical parameters. The geometric information can be obtained from a digital map of a city. To study the effects of inaccuracies in geometry information (building layout) on RT-based coverage prediction, two different artificial erroneous maps are generated based on the original digital map, and systematic analysis is performed by comparing the predictions with the erroneous maps and measurements or the predictions with the original digital map. To make the conclusion more persuasive, the influence of random errors on RMS delay spread results is investigated. Furthermore, given the electrical parameters' effect on the accuracy of the predicted results of the RT model, the dielectric constant and conductivity of building materials are set with different values. The path loss and RMS delay spread under the same circumstances are simulated by the RT prediction model. PMID:27607495

  10. Ray-tracing analysis of the Wien velocity filter for protons

    NASA Astrophysics Data System (ADS)

    Kim, Jae Hong; Kim, Yu-Soek

    2015-02-01

    A Wien velocity filter employs a combination of crossed magnetic and electrostatic fields in order to select the desired velocity of ions. Several microscopes and spectrometers are used as filters to ensure the introduction of a pure ion fraction into the lens, deflecting unnecessary particles which have slightly different energies. The Wien filter is also considered to be a useful device to transport mono-energy protons from a source to an injection system. In its simplest form, the Wien filter has two flat parallel electrodes that are arranged between two flat magnet poles, creating homogeneous electric and magnetic fields which cross each other. However, this type of filter has no focusing effect in the direction of the magnetic field and has an unmatched field distribution, which causes deflections of protons at the entrance and the exit of the filter. At higher magnetic field strengs, for fast protons, the deflection of the trajectories becomes larger; thus, the transport efficiency is reduced. A low-aberration velocity filter is needed for high transport efficiency. Recently, a stigmatic focusing of the filter by using hyperbolic cylindrical magnet pole pieces, which produce an inhomogeneous magnetic field inside the ExB filter, has been suggested. In this research, three types of Wien filters were designed in order to investigate the geometry of the electrodes and the magnet poles, thus minimizing aberrations. Ray-tracing analyses were carried out to estimate the performance of the proposed Wien filters within a useful velocity selector.

  11. Forward ray-tracing for medium-scale gravity waves observed during the COPEX campaign

    NASA Astrophysics Data System (ADS)

    Paulino, I.; Takahashi, H.; Vadas, S. L.; Wrasse, C. M.; Sobral, J. H. A.; Medeiros, A. F.; Buriti, R. A.; Gobbi, D.

    2012-12-01

    Medium-scale gravity waves (MSGWs) observed during the Conjugate Point Experiment (COPEX) at Boa Vista (2.8°N; 60.7°S, dip angle 21.7°) have been ray-traced and studied based on zero wind and model wind conditions. Wind profiles have been used from the TIE-GCM and HWM-07 models. Temperature profiles were used from the NRLMSISE-00 and TIE-GCM models, and TIMED/SABER satellite data. Doppler up-shifted MSGWs, at ˜87km of altitude, propagated to higher altitudes into the thermosphere-ionosphere domain than waves that were un-shifted. Most MSGWs propagated upwards up to ˜140km of altitude and were seen to be unlikely candidates to trigger equatorial plasma bubbles (EPBs) at the F layer bottom side. However, three of them propagated up to heights close to the F layer bottom side, where it could act in the EPB seeding directly. Moreover, three MSGWs, which propagated equatorward, could act on EPB seeding by field-line-integrated effects.

  12. Spatial resolution recovery utilizing multi-ray tracing and graphic processing unit in PET image reconstruction.

    PubMed

    Liang, Yicheng; Peng, Hao

    2015-02-01

    Depth-of-interaction (DOI) poses a major challenge for a PET system to achieve uniform spatial resolution across the field-of-view, particularly for small animal and organ-dedicated PET systems. In this work, we implemented an analytical method to model system matrix for resolution recovery, which was then incorporated in PET image reconstruction on a graphical processing unit platform, due to its parallel processing capacity. The method utilizes the concepts of virtual DOI layers and multi-ray tracing to calculate the coincidence detection response function for a given line-of-response. The accuracy of the proposed method was validated for a small-bore PET insert to be used for simultaneous PET/MR breast imaging. In addition, the performance comparisons were studied among the following three cases: 1) no physical DOI and no resolution modeling; 2) two physical DOI layers and no resolution modeling; and 3) no physical DOI design but with a different number of virtual DOI layers. The image quality was quantitatively evaluated in terms of spatial resolution (full-width-half-maximum and position offset), contrast recovery coefficient and noise. The results indicate that the proposed method has the potential to be used as an alternative to other physical DOI designs and achieve comparable imaging performances, while reducing detector/system design cost and complexity. PMID:25591118

  13. Exploring Light's Interactions with Bubbles and Light Absorbers in Photoelectrochemical Devices using Ray Tracing

    SciTech Connect

    Stevens, John

    2013-12-01

    Ray tracing was used to perform optical optimization of arrays of photovoltaic microrods and explore the interaction between light and bubbles of oxygen gas on the surface of the microrods. The incident angle of light was varied over a wide range. The percent of incident light absorbed by the microrods and reflected by the bubbles was computed over this range. It was found that, for the 10 μm diameter, 100 μm tall SrTiO3 microrods simulated in the model, the optimal center-to-center spacing was 14 μm for a square grid. This geometry produced 75% average and 90% maximum absorbance. For a triangular grid using the same microrods, the optimal center-to-­center spacing was 14 μm. This geometry produced 67% average and 85% maximum absorbance. For a randomly laid out grid of 5 μm diameter, 100 μm tall SrTiO! microrods with an average center-­to-­center spacing of 20 μm, the average absorption was 23% and the maximum absorption was 43%. For a 50% areal coverage fraction of bubbles on the absorber surface, between 2%-20% of the incident light energy was reflected away from the rods by the bubbles, depending upon incident angle and bubble morphology.

  14. Ray-tracing studies for a whole-viewing-angle retroreflector

    SciTech Connect

    Yang, B.; Friedsam, H.

    2000-02-02

    The APS Survey and Alignment team uses LEICA laser trackers for the majority of their alignment tasks. These instruments utilize several different retroreflectors for tracking the path of the laser interferometer. Currently in use are open-air corner cubes with an acceptance angle of {+-}20{degree}, corner cube prisms with an acceptance angle of {+-}50{degree}, and a Cat's eye with an acceptance angle of {+-}60{degree}. Best measurement results can be achieved by using an open-air corner cube that eliminates the need for the laser beam to travel through a different medium before it returns to the instrument detector. However, the trade off is a small acceptance angle. In order to overcome the limitations of the small acceptance angles, Takatsuji et al. has proposed the creation of a full-viewing-angle retroreflector. Based on the notion that the radius R{sub 1} of a common Cat's eye is proportional to R{sub 2}, one can write: R{sub 1} = (n {minus} 1)R{sub 2}. In the case that n, the refractive index of glass, equals 2, the radii R{sub 1} and R{sub 2} are identical, and one can create a solid sphere Cat's eye. This design has the advantages that no adhesives are used to bond the two hemispheres together, misalignments between the hemispheres are not an issue, and most importantly, larger acceptance angles are possible. This paper shows the results of their ray tracing calculations characterizing the geometrical optics.

  15. Monte Carlo ray-tracing simulations of luminescent solar concentrators for building integrated photovoltaics

    NASA Astrophysics Data System (ADS)

    Leow, Shin Woei; Corrado, Carley; Osborn, Melissa; Carter, Sue A.

    2013-09-01

    Luminescent solar concentrators (LSCs) have the ability to receive light from a wide range of angles, concentrating the captured light onto small photo active areas. This enables greater incorporation of LSCs into building designs as windows, skylights and wall claddings in addition to rooftop installations of current solar panels. Using relatively cheap luminescent dyes and acrylic waveguides to effect light concentration onto lesser photovoltaic (PV) cells, there is potential for this technology to approach grid price parity. We employ a panel design in which the front facing PV cells collect both direct and concentrated light ensuring a gain factor greater than one. This also allows for flexibility in determining the placement and percentage coverage of PV cells during the design process to balance reabsorption losses against the power output and level of light concentration desired. To aid in design optimization, a Monte-Carlo ray tracing program was developed to study the transport of photons and loss mechanisms in LSC panels. The program imports measured absorption/emission spectra and transmission coefficients as simulation parameters with interactions of photons in the panel determined by comparing calculated probabilities with random number generators. LSC panels with multiple dyes or layers can also be simulated. Analysis of the results reveals optimal panel dimensions and PV cell layouts for maximum power output for a given dye concentration, absorbtion/emission spectrum and quantum efficiency.

  16. Analyzing luminescent solar concentrators with front-facing photovoltaic cells using weighted Monte Carlo ray tracing

    NASA Astrophysics Data System (ADS)

    Woei Leow, Shin; Corrado, Carley; Osborn, Melissa; Isaacson, Michael; Alers, Glenn; Carter, Sue A.

    2013-06-01

    Luminescent solar concentrators (LSC) collect ambient light from a broad range of angles and concentrate the captured light onto photovoltaic (PV) cells. LSCs with front-facing cells collect direct and indirect sunlight ensuring a gain factor greater than one. The flexible placement and percentage coverage of PV cells on the LSC panel allow for layout adjustments to be made in order to balance re-absorption losses and the level of light concentration desired. A weighted Monte Carlo ray tracing program was developed to study the transport of photons and loss mechanisms in the LSC to aid in design optimization. The program imports measured absorption/emission spectra of an organic luminescent dye (LR305), the transmission coefficient, and refractive index of acrylic as parameters that describe the system. Simulations suggest that for LR305, 8-10 cm of luminescent material surrounding the PV cell yields the highest increase in power gain per unit area of LSC added, thereby determining the ideal spacing between PV cells in the panel. For rectangular PV cells, results indicate that for each centimeter of PV cell width, an additional increase of 0.15 mm to the waveguide thickness is required to efficiently transport photon collected by the LSC to the PV cell with minimal loss.

  17. Infrasonic ray tracing applied to small-scale atmospheric structures: thermal plumes and updrafts/downdrafts.

    PubMed

    Jones, R Michael; Bedard, Alfred J

    2015-02-01

    A ray-tracing program is used to estimate the refraction of infrasound by the vertical structure of the atmosphere in thermal plumes, showing only weak effects, as well as in updrafts and downdrafts, which can act as vertical wave guides. Thermal plumes are ubiquitous features of the daytime atmospheric boundary layer. The effects of thermal plumes on lower frequency sound propagation are minor with the exception of major events, such as volcanoes, forest fires, or industrial explosions where quite strong temperature gradients are involved. On the other hand, when strong, organized vertical flows occur (e.g., in mature thunderstorms and microbursts), there are significant effects. For example, a downdraft surrounded by an updraft focuses sound as it travels upward, and defocuses sound as it travels downward. Such propagation asymmetry may help explain observations that balloonists can hear people on the ground; but conversely, people on the ground cannot hear balloonists aloft. These results are pertinent for those making surface measurements from acoustic sources aloft, as well as for measurements of surface sound sources using elevated receivers. PMID:25697997

  18. Intraocular lens power estimation by accurate ray tracing for eyes underwent previous refractive surgeries

    NASA Astrophysics Data System (ADS)

    Yang, Que; Wang, Shanshan; Wang, Kai; Zhang, Chunyu; Zhang, Lu; Meng, Qingyu; Zhu, Qiudong

    2015-08-01

    For normal eyes without history of any ocular surgery, traditional equations for calculating intraocular lens (IOL) power, such as SRK-T, Holladay, Higis, SRK-II, et al., all were relativley accurate. However, for eyes underwent refractive surgeries, such as LASIK, or eyes diagnosed as keratoconus, these equations may cause significant postoperative refractive error, which may cause poor satisfaction after cataract surgery. Although some methods have been carried out to solve this problem, such as Hagis-L equation[1], or using preoperative data (data before LASIK) to estimate K value[2], no precise equations were available for these eyes. Here, we introduced a novel intraocular lens power estimation method by accurate ray tracing with optical design software ZEMAX. Instead of using traditional regression formula, we adopted the exact measured corneal elevation distribution, central corneal thickness, anterior chamber depth, axial length, and estimated effective lens plane as the input parameters. The calculation of intraocular lens power for a patient with keratoconus and another LASIK postoperative patient met very well with their visual capacity after cataract surgery.

  19. First results and planned experiments with the INFN-LNS ray-tracing magnetic spectrometer MAGNEX

    SciTech Connect

    Cunsolo, A.; Cappuzzello, F.; Cavallaro, M.; Orrigo, S. E. A.; Foti, A.; Rodrigues, M. R. D.; Borello-Lewin, T.; Petrascu, H.; Carbone, D.

    2010-05-21

    The MAGNEX large-acceptance ray-tracing magnetic spectrometer has recently been used with beams from the INFN-LNS Tandem accelerator. After an accurate commissioning, the instrument has started an ambitious experimental program. In the first experiment the {sup 19}F({sup 7}Li,{sup 7}Be){sup 19}O charge-exchange reaction was studied at 52 MeV incident energy. The {sup 19}O excitation energy spectrum was reconstructed and the angular distributions measured. The second experiment was aimed at the study of the {sup 15}C via the {sup 13}C({sup 18}O,{sup 16}O){sup 15}C reaction at 84 MeV incident energy. The ejectiles where detected at forward angles and mass identified by means of an innovative technique. The {sup 15}C excitation energy spectra up to about 20 MeV were obtained with a 250 keV FWHM energy resolution. In addition to several known states, the spectra show two unknown resonant-like structures at 11.4 and 14.0 MeV. The strong population of these structures, together with the measured widths, could indicate the collective nature of these states associated to a correlated neutron pair transfer. Besides the first results of physical interest from these two experiments, future experiments with MAGNEX are briefly outlined.

  20. Image Comparisons of Black Hole vs. Neutron Dark Star by Ray Tracing

    NASA Astrophysics Data System (ADS)

    Froedge, D. T.

    2015-04-01

    In previous papers we have discussed the concept of a theory of gravitation with local energy conservation, and the properties of a large neutron star resulting when the energy of gravitation resides locally with the particle mass and not in the gravitational field. A large neutron star's surface radius grows closer to the gravitational radius as the mass increases. Since the localization of energy applies to the photon, they do not decrease energy rising in a gravitational field, and can escape. Photon trajectories in a strong gravitational field can be investigated by the use of ray tracing procedures. Only a fraction of the blackbody radiation emitted from the surface escapes into space (about 0.00004% for Sag A*). Because of the low % of escaping radiation, the heavy neutron stars considered in this paper will be referred to as a Neutron Dark Star (NDS). In contrast to the Black Hole (BH) which should be totally dark inside the photon shadow, the NDS will appear as a fuzzy low luminosity ball. For Sag A* a full width half maximum diameter is about 3.85 Schwarzschild radii inside the shadow. (http://www.arxdtf.org/css/Image%20Comparisons.pdf). The Event Horizon Telescope should be able to distinguish the difference between the theories.

  1. Internal and external stray radiation suppression for LWIR catadioptric telescope using non-sequential ray tracing

    NASA Astrophysics Data System (ADS)

    Zhu, Yang; Zhang, Xin; Liu, Tao; Wu, Yanxiong; Shi, Guangwei; Wang, Lingjie

    2015-07-01

    A long wave infrared imaging system operated for space exploration of faint target is highly sensitive to stray radiation. We present an integrative suppression process of internal and external stray radiation. A compact and re-imaging LWIR catadioptric telescope is designed as practical example and internal and external stray radiation is analyzed for this telescope. The detector is cryogenically cooled with 100% cold shield efficiency of Lyot stop. A non-sequential ray tracing technique is applied to investigate how the stray radiation propagates inside optical system. The simulation and optimization during initial design stage are proceeded to avoid subversive defect that the stray radiation disturbs the target single. The quantitative analysis of stray radiation irradiance emitted by lenses and structures inside is presented in detail. The optical elements, which operate at room-temperature due to the limitation of weight and size, turn to be the significant stray radiation sources. We propose a method combined infrared material selection and optical form optimization to reduce the internal stray radiation of lens. We design and optimize mechanical structures to achieve a further attenuation of internal stray radiation power. The point source transmittance (PST) is calculated to assess the external radiation which comes from the source out of view field. The ghost of bright target due to residual reflection of optical coatings is simulated. The results show that the performance of stray radiation suppression is dramatically improved by iterative optimization and modification of optomechanical configurations.

  2. Sensitivity of power and RMS delay spread predictions of a 3D indoor ray tracing model.

    PubMed

    Liu, Zhong-Yu; Guo, Li-Xin; Li, Chang-Long; Wang, Qiang; Zhao, Zhen-Wei

    2016-06-13

    This study investigates the sensitivity of a three-dimensional (3D) indoor ray tracing (RT) model for the use of the uniform theory of diffraction and geometrical optics in radio channel characterizations of indoor environments. Under complex indoor environments, RT-based predictions require detailed and accurate databases of indoor object layouts and the electrical characteristics of such environments. The aim of this study is to assist in selecting the appropriate level of accuracy required in indoor databases to achieve good trade-offs between database costs and prediction accuracy. This study focuses on the effects of errors in indoor environments on prediction results. In studying the effects of inaccuracies in geometry information (indoor object layout) on power coverage prediction, two types of artificial erroneous indoor maps are used. Moreover, a systematic analysis is performed by comparing the predictions with erroneous indoor maps and those with the original indoor map. Subsequently, the influence of random errors on RMS delay spread results is investigated. Given the effect of electrical parameters on the accuracy of the predicted results of the 3D RT model, the relative permittivity and conductivity of different fractions of an indoor environment are set with different values. Five types of computer simulations are considered, and for each type, the received power and RMS delay spread under the same circumstances are simulated with the RT model. PMID:27410335

  3. Tracing Two Apprentices' Trajectories toward Adaptive Professional Expertise in Fingerprint Examination

    ERIC Educational Resources Information Center

    Mustonen, Virpi; Hakkarainen, Kai

    2015-01-01

    The purpose of this study is to analyse the development of two apprentices' adaptive expertise in fingerprint examination across a two-year training program. The apprentices were selected from a large number of candidates to be trained at the Forensic Laboratory of the Finnish National Bureau of Investigation. The problem addressed was how the…

  4. Evaluation of simulation alternatives for the brute-force ray-tracing approach used in backlight design

    NASA Astrophysics Data System (ADS)

    Desnijder, Karel; Hanselaer, Peter; Meuret, Youri

    2016-04-01

    A key requirement to obtain a uniform luminance for a side-lit LED backlight is the optimised spatial pattern of structures on the light guide that extract the light. The generation of such a scatter pattern is usually performed by applying an iterative approach. In each iteration, the luminance distribution of the backlight with a particular scatter pattern is analysed. This is typically performed with a brute-force ray-tracing algorithm, although this approach results in a time-consuming optimisation process. In this study, the Adding-Doubling method is explored as an alternative way for evaluating the luminance of a backlight. Due to the similarities between light propagating in a backlight with extraction structures and light scattering in a cloud of light scatterers, the Adding-Doubling method which is used to model the latter could also be used to model the light distribution in a backlight. The backlight problem is translated to a form upon which the Adding-Doubling method is directly applicable. The calculated luminance for a simple uniform extraction pattern with the Adding-Doubling method matches the luminance generated by a commercial raytracer very well. Although successful, no clear computational advantage over ray tracers is realised. However, the dynamics of light propagation in a light guide as used the Adding-Doubling method, also allow to enhance the efficiency of brute-force ray-tracing algorithms. The performance of this enhanced ray-tracing approach for the simulation of backlights is also evaluated against a typical brute-force ray-tracing approach.

  5. NVIDIA OptiX ray-tracing engine as a new tool for modelling medical imaging systems

    NASA Astrophysics Data System (ADS)

    Pietrzak, Jakub; Kacperski, Krzysztof; Cieślar, Marek

    2015-03-01

    The most accurate technique to model the X- and gamma radiation path through a numerically defined object is the Monte Carlo simulation which follows single photons according to their interaction probabilities. A simplified and much faster approach, which just integrates total interaction probabilities along selected paths, is known as ray tracing. Both techniques are used in medical imaging for simulating real imaging systems and as projectors required in iterative tomographic reconstruction algorithms. These approaches are ready for massive parallel implementation e.g. on Graphics Processing Units (GPU), which can greatly accelerate the computation time at a relatively low cost. In this paper we describe the application of the NVIDIA OptiX ray-tracing engine, popular in professional graphics and rendering applications, as a new powerful tool for X- and gamma ray-tracing in medical imaging. It allows the implementation of a variety of physical interactions of rays with pixel-, mesh- or nurbs-based objects, and recording any required quantities, like path integrals, interaction sites, deposited energies, and others. Using the OptiX engine we have implemented a code for rapid Monte Carlo simulations of Single Photon Emission Computed Tomography (SPECT) imaging, as well as the ray-tracing projector, which can be used in reconstruction algorithms. The engine generates efficient, scalable and optimized GPU code, ready to run on multi GPU heterogeneous systems. We have compared the results our simulations with the GATE package. With the OptiX engine the computation time of a Monte Carlo simulation can be reduced from days to minutes.

  6. Usage of CO2 microbubbles as flow-tracing contrast media in X-ray dynamic imaging of blood flows.

    PubMed

    Lee, Sang Joon; Park, Han Wook; Jung, Sung Yong

    2014-09-01

    X-ray imaging techniques have been employed to visualize various biofluid flow phenomena in a non-destructive manner. X-ray particle image velocimetry (PIV) was developed to measure velocity fields of blood flows to obtain hemodynamic information. A time-resolved X-ray PIV technique that is capable of measuring the velocity fields of blood flows under real physiological conditions was recently developed. However, technical limitations still remained in the measurement of blood flows with high image contrast and sufficient biocapability. In this study, CO2 microbubbles as flow-tracing contrast media for X-ray PIV measurements of biofluid flows was developed. Human serum albumin and CO2 gas were mechanically agitated to fabricate CO2 microbubbles. The optimal fabricating conditions of CO2 microbubbles were found by comparing the size and amount of microbubbles fabricated under various operating conditions. The average size and quantity of CO2 microbubbles were measured by using a synchrotron X-ray imaging technique with a high spatial resolution. The quantity and size of the fabricated microbubbles decrease with increasing speed and operation time of the mechanical agitation. The feasibility of CO2 microbubbles as a flow-tracing contrast media was checked for a 40% hematocrit blood flow. Particle images of the blood flow were consecutively captured by the time-resolved X-ray PIV system to obtain velocity field information of the flow. The experimental results were compared with a theoretically amassed velocity profile. Results show that the CO2 microbubbles can be used as effective flow-tracing contrast media in X-ray PIV experiments. PMID:25178007

  7. The adaptive function of melanin-based plumage coloration to trace metals

    PubMed Central

    Chatelain, M.; Gasparini, J.; Jacquin, L.; Frantz, A.

    2014-01-01

    Trace metals produced by anthropogenic activities are of major importance in urban areas and might constitute a new evolutionary force selecting for the ability to cope with their deleterious effects. Interestingly, melanin pigments are known to bind metal ions, thereby potentially sequestering them in inert body parts such as coat and feathers, and facilitating body detoxification. Thus, a more melanic plumage or coat coloration could bring a selective advantage for animals living in polluted areas. We tested this hypothesis by investigating the link between melanin-based coloration and zinc and lead concentrations in feathers of urban feral pigeons, both at capture time and after one year of captivity in standardized conditions. Results show that differently coloured pigeons had similar metal concentrations at capture time. Metal concentrations strongly decreased after one year in standardized conditions, and more melanic pigeons had higher concentrations of zinc (but not lead) in their feathers. This suggests that more melanic pigeons have a higher ability to store some metals in their feathers compared with their paler counterparts, which could explain their higher success in urbanized areas. Overall, this work suggests that trace metal pollution may exert new selective forces favouring more melanic phenotypes in polluted environments. PMID:24671830

  8. Measurement of Trace Constituents by Electron-Excited X-Ray Microanalysis with Energy-Dispersive Spectrometry.

    PubMed

    Newbury, Dale E; Ritchie, Nicholas W M

    2016-06-01

    Electron-excited X-ray microanalysis performed with scanning electron microscopy and energy-dispersive spectrometry (EDS) has been used to measure trace elemental constituents of complex multielement materials, where "trace" refers to constituents present at concentrations below 0.01 (mass fraction). High count spectra measured with silicon drift detector EDS were quantified using the standards/matrix correction protocol embedded in the NIST DTSA-II software engine. Robust quantitative analytical results for trace constituents were obtained from concentrations as low as 0.000500 (mass fraction), even in the presence of significant peak interferences from minor (concentration 0.01≤C≤0.1) and major (C>0.1) constituents. Limits of detection as low as 0.000200 were achieved in the absence of peak interference. PMID:27329308

  9. X-ray telescope onboard Astro-E. III. Guidelines to performance improvements and optimization of the ray-tracing simulator.

    PubMed

    Misaki, Kazutami; Hidaka, Yasuhiro; Ishida, Manabu; Shibata, Ryo; Furuzawa, Akihiro; Haba, Yoshito; Itoh, Kei; Mori, Hideyuki; Kunieda, Hideyo

    2005-02-20

    We present a detailed study of the performance of the Astro-E x-ray telescope (XRT) onboard the Astro-E satellite. As described in preceding papers the ground-based calibrations of the Astro-E XRT revealed that its image quality and effective area are somewhat worse than that expected from the original design. Conceivable causes for such performance degradation are examined by x-ray and optical microscopic measurements at various levels, such as individual reflectors, sectors, and quadrants of the XRT and their alignments. We can attribute, based on detailed measurements, the degradation of the image quality to a slope error in the individual reflectors and the positioning error of reflectors. As for the deficit of the effective area, the shadowing of x rays within the XRT body is the dominant factor. Error budgets for the performance degradation of the Astro-E XRT are summarized. The ray-tracing simulator, which is needed to construct the response function for arbitrary off-axis angles and spatial distributions of any celestial x-ray sources, has been developed and tuned based on the results of detailed measurements. The ray-tracing simulation provides results that are consistent within 3% with the real measurement except for large off-axis angles and higher energies. We propose, based on knowledge obtained from all the measurements and simulations, several plans for future developments to improve the performance of the nested thin-foil mirrors. PMID:15751683

  10. Ray tracing simulations for the wide-field x-ray telescope of the Einstein Probe mission based on Geant4 and XRTG4

    NASA Astrophysics Data System (ADS)

    Zhao, Donghua; Zhang, Chen; Yuan, Weimin; Willingale, Richard; Ling, Zhixing; Feng, Hua; Li, Hong; Ji, Jianfeng; Wang, Wenxin; Zhang, Shuangnan

    2014-07-01

    Einstein Probe (EP) is a proposed small scientific satellite dedicated to time-domain astrophysics working in the soft X-ray band. It will discover transients and monitor variable objects in 0.5-4 keV, for which it will employ a very large instantaneous field-of-view (60° × 60°), along with moderate spatial resolution (FWHM ˜ 5 arcmin). Its wide-field imaging capability will be achieved by using established technology in novel lobster-eye optics. In this paper, we present Monte-Carlo simulations for the focusing capabilities of EP's Wide-field X-ray Telescope (WXT). The simulations are performed using Geant4 with an X-ray tracer which was developed by cosine (http://cosine.nl/) to trace X-rays. Our work is the first step toward building a comprehensive model with which the design of the X-ray optics and the ultimate sensitivity of the instrument can be optimized by simulating the X-ray tracing and radiation environment of the system, including the focal plane detector and the shielding at the same time.

  11. Micro-trace fossils reveal pervasive reworking of Pliocene sapropels by low-oxygen-adapted benthic meiofauna.

    PubMed

    Löhr, S C; Kennedy, M J

    2015-01-01

    Animal burrowers leave an indelible signature on the sedimentary record in most marine environments, with the seeming exception of low-oxygen environments. In modern sedimentary settings, however, sub-millimetre-sized benthic animals (meiofauna) are adapted to low oxygen and even sulfidic conditions. Almost nothing is known about their impact on ancient marine sediments because they leave few recognizable traces. Here we show, in classic Pliocene-aged anoxic facies from the Mediterranean, the first reported trace fossil evidence of meiofaunal activity and its relation to changing oxygenation. A novel approach utilizing electron imaging of ion-polished samples shows that meiofauna pervasively reworked sediment under oxygen-depleted conditions that excluded macrofauna, fragmenting organic laminae and emplacing 15- to 70-μm-diameter faecal pellets without macroscopically influencing the fabric. The extent of reworking raises the question: how pervasively altered are other sediments presently assumed to lack animal influence and how far into the geological record does this influence extend? PMID:25762504

  12. An analysis of options available for developing a common laser ray tracing package for Ares and Kull code frameworks

    SciTech Connect

    Weeratunga, S K

    2008-11-06

    Ares and Kull are mature code frameworks that support ALE hydrodynamics for a variety of HEDP applications at LLNL, using two widely different meshing approaches. While Ares is based on a 2-D/3-D block-structured mesh data base, Kull is designed to support unstructured, arbitrary polygonal/polyhedral meshes. In addition, both frameworks are capable of running applications on large, distributed-memory parallel machines. Currently, both these frameworks separately support assorted collections of physics packages related to HEDP, including one for the energy deposition by laser/ion-beam ray tracing. This study analyzes the options available for developing a common laser/ion-beam ray tracing package that can be easily shared between these two code frameworks and concludes with a set of recommendations for its development.

  13. Three-dimensional ray tracing of electrostatic cyclotron harmonic waves and Z mode electromagnetic waves in the magnetosphere

    NASA Astrophysics Data System (ADS)

    Hashimoto, K.; Yamaashi, K.; Kimura, I.

    1987-08-01

    Three-dimensional ray tracing is performed for electrostatic electron cyclotron harmonic waves and Z mode electromagnetic waves in the earth's magnetosphere using the hot dispersion relation. Propagation characteristics of cyclotron harmonic waves under the electrostatic approximation are considered, and it is noted that waves starting near the equator can propagate over a long distance without damping. Ray tracing without the electrostatic approximation confirms mode conversion from cyclotron harmonic waves to Z mode electromagnetic waves, and the conditions for the conversion are clarified. It is suggested that further conversion to the L-O mode continuum radiation is possible under strict constraints. The present results are not inconsistent with the conversion mechanism for the generation of escaping continuum radiation in the magnetosphere.

  14. Patellar segmentation from 3D magnetic resonance images using guided recursive ray-tracing for edge pattern detection

    NASA Astrophysics Data System (ADS)

    Cheng, Ruida; Jackson, Jennifer N.; McCreedy, Evan S.; Gandler, William; Eijkenboom, J. J. F. A.; van Middelkoop, M.; McAuliffe, Matthew J.; Sheehan, Frances T.

    2016-03-01

    The paper presents an automatic segmentation methodology for the patellar bone, based on 3D gradient recalled echo and gradient recalled echo with fat suppression magnetic resonance images. Constricted search space outlines are incorporated into recursive ray-tracing to segment the outer cortical bone. A statistical analysis based on the dependence of information in adjacent slices is used to limit the search in each image to between an outer and inner search region. A section based recursive ray-tracing mechanism is used to skip inner noise regions and detect the edge boundary. The proposed method achieves higher segmentation accuracy (0.23mm) than the current state-of-the-art methods with the average dice similarity coefficient of 96.0% (SD 1.3%) agreement between the auto-segmentation and ground truth surfaces.

  15. Fokker-Planck/Ray Tracing for Electron Bernstein and Fast Wave Modeling in Support of NSTX

    SciTech Connect

    Harvey, R. W.

    2009-11-12

    This DOE grant supported fusion energy research, a potential long-term solution to the world's energy needs. Magnetic fusion, exemplified by confinement of very hot ionized gases, i.e., plasmas, in donut-shaped tokamak vessels is a leading approach for this energy source. Thus far, a mixture of hydrogen isotopes has produced 10's of megawatts of fusion power for seconds in a tokamak reactor at Princeton Plasma Physics Laboratory in New Jersey. The research grant under consideration, ER54684, uses computer models to aid in understanding and projecting efficacy of heating and current drive sources in the National Spherical Torus Experiment, a tokamak variant, at PPPL. The NSTX experiment explores the physics of very tight aspect ratio, almost spherical tokamaks, aiming at producing steady-state fusion plasmas. The current drive is an integral part of the steady-state concept, maintaining the magnetic geometry in the steady-state tokamak. CompX further developed and applied models for radiofrequency (rf) heating and current drive for applications to NSTX. These models build on a 30 year development of rf ray tracing (the all-frequencies GENRAY code) and higher dimensional Fokker-Planck rf-collisional modeling (the 3D collisional-quasilinear CQL3D code) at CompX. Two mainline current-drive rf modes are proposed for injection into NSTX: (1) electron Bernstein wave (EBW), and (2) high harmonic fast wave (HHFW) modes. Both these current drive systems provide a means for the rf to access the especially high density plasma--termed high beta plasma--compared to the strength of the required magnetic fields. The CompX studies entailed detailed modeling of the EBW to calculate the efficiency of the current drive system, and to determine its range of flexibility for driving current at spatial locations in the plasma cross-section. The ray tracing showed penetration into NSTX bulk plasma, relatively efficient current drive, but a limited ability to produce current over the whole

  16. 3-D TECATE/BREW: Thermal, stress, and birefringent ray-tracing codes for solid-state laser design

    SciTech Connect

    Gelinas, R.J.; Doss, S.K.; Nelson, R.G.

    1994-07-20

    This report describes the physics, code formulations, and numerics that are used in the TECATE (totally Eulerian code for anisotropic thermo-elasticity) and BREW (birefringent ray-tracing of electromagnetic waves) codes for laser design. These codes resolve thermal, stress, and birefringent optical effects in 3-D stationary solid-state systems. This suite of three constituent codes is a package referred to as LASRPAK.

  17. Measurements of slant and vertical TEC using data from FORTE and the TRACKER ray-tracing code

    SciTech Connect

    Massey, R.S.

    1997-12-12

    In a previous informal report, the author described the FORTE satellite and the analysis techniques used to extract a slant TEC from measurements of the dispersion of a signal transmitted from and EMP generator at Los Alamos. In this report he reports on the use of a ray-tracing/ionospheric model code to deduce the vertical TEC to 800 km from the FORTE measurements.

  18. A Generalized Planetary Acoustic, Ray-tracing Model with Example Application to Bolide Detection on Mars

    NASA Astrophysics Data System (ADS)

    Williams, J.; McEwan, I. J.

    2002-12-01

    Planetary acoustics has been relatively unexplored on planets other than Earth yet has the potential to provide equally convenient remote measurement techniques and to yield equally rich scientific data sets. We present the first generalized planetary acoustic, ray-tracing model which takes into account environmental conditions and viscous, thermal, and molecular relaxation of multi-gas atmospheres. We show a specific Martian application to making use of terrestrial techniques for bolide detection and influx estimates, and introduce concepts for identifying and tracking general sound sources such as dust devils. Meteors penetrating deep into the terrestrial atmosphere are known to generate large well-characterized acoustics signals. Similar explosive events provide acoustic sources in the Martian atmosphere that should be detectable by sensors on the surface. We present an end-to-end comparison between Earth and Mars of a meteor event from the bolide's entry, through detonation and acoustic transmission of the shockwave, to what is heard by ground detectors (this includes intensity, frequency response, and region of detectability). With the use of an array of detectors detonation events can be spatially localized. We place constraints on the practicality of an instrument and compare with equivalent seismic meteor detection. This analysis leads to a measurement method for estimating bolide influx rates in the Martian atmosphere. This rate is currently highly uncertain and significantly affects results of modeled absolute crater retention ages. Pending work includes the application of similar acoustic localization techniques to develop an instruments concept for the detection and tracking of dust devils such as those observed in both Pathfinder and Mars Global Surveyor images. Further, with minimal reconfiguration, our model and the above analysis can also be applied to Venus and Titan.

  19. Gamma-Ray Bursts Trace UV Metrics of Star Formation over 3 < z < 5

    NASA Astrophysics Data System (ADS)

    Greiner, J.; Fox, D. B.; Schady, P.; Krühler, T.; Trenti, M.; Cikota, A.; Bolmer, J.; Elliott, J.; Delvaux, C.; Perna, R.; Afonso, P.; Kann, D. A.; Klose, S.; Savaglio, S.; Schmidl, S.; Schweyer, T.; Tanga, M.; Varela, K.

    2015-08-01

    We present the first uniform treatment of long duration gamma-ray burst (GRB) host galaxy detections and upper limits over the redshift range 3-15.6 mag, and with extrapolations of the assumed Schechter-type LF well beyond this range. We review proposed astrophysical and observational biases for our sample, and find that they are for the most part minimal. We therefore conclude, as the simplest interpretation of our results, that GRBs successfully trace UV metrics of cosmic SF over the range 3

  20. Ray tracing technique for global 3-D modeling of ionospheric electron density using GNSS measurements

    NASA Astrophysics Data System (ADS)

    Alizadeh, Mohamad Mahdi; Schuh, Harald; Schmidt, Michael

    2015-06-01

    For space geodetic techniques, operating in microwave band, ionosphere is a dispersive medium; thus, signals traveling through this medium are in the first approximation, affected proportional to the inverse of the square of their frequencies. This effect allows gaining information about the parameters of the ionosphere in terms of total electron content (TEC) or the electron density (Ne). Making use of this phenomenon, space geodetic techniques have turned into a capable tool for studying the ionosphere in the last decades. Up to now, two-dimensional (2-D) models of Vertical TEC (VTEC) have been widely developed and used by different communities; however, due to the fact that these models provide information about the integral of the whole electron content along the vertical or slant raypath, these maps are not useful when information about the ionosphere at different altitude is required. This paper presents a recent study which aims at developing a global 3-D model of the electron density, using measurements from Global Navigation Satellite Systems and by applying the ray tracing technique to the upper atmosphere. The developed modeling approach represents the horizontal variations of the electron density, with two sets of spherical harmonic expansions of degree and order 15. The height dependency of the electron density is represented by a multilayered Chapman profile function for the bottomside and topside ionosphere, and an appropriate model for the plasmasphere. In addition to the geodetic applications of the developed models, within this study, the 3-D models of electron density can include geophysical parameters like maximum electron density and its corresponding height. High-resolution modeling of these parameters allows an improved geophysical interpretation, which is essential in all studies of the upper atmosphere, space weather, and for the solar-terrestrial environment.

  1. HF "Swishers" Observed with a Recent Sounding Rocket: A Ray Tracing Study

    NASA Astrophysics Data System (ADS)

    Colpitts, C. A.; Yoon, P.; Samara, M.

    2005-12-01

    The sounding rocket SIERRA (Sounding of the Ion Energization Region: Resolving Ambiguities) was launched duing a rocket campaign at the Poker Flat, Alaska, rocket range (65.13° W) on January 14, 2002. It reached an apogee of 735 km at approximately 500 s into the flight. A high frequency electric field instrument (HFE) provided by Dartmouth College was included in the payload. The HFE continuously measured the full electric field waveform up to 5 MHz and transmitted it to the ground via a wide band analog telemetry. Among the wavesforms detected by the HFE was a new signature that we term "swishers," time-dispersed signals at 1.2 to 1.6 MHz in which the higher frequencies were observed first and the lower frequencies observed delayed by tens of milliseconds. Several dozen of these waveforms were detected during a 20 second span on the upleg of the flight, when the rocket was in an underdense region (fpeRay tracing calculations will be done to test this hypothesis and attempt to constrain the modes of the waves and determine the size, location, and motion of their sources.

  2. OFFSET - RAY TRACING OPTICAL ANALYSIS OF OFFSET SOLAR COLLECTOR FOR SPACE STATION SOLAR DYNAMIC POWER SYSTEM

    NASA Technical Reports Server (NTRS)

    Jefferies, K.

    1994-01-01

    OFFSET is a ray tracing computer code for optical analysis of a solar collector. The code models the flux distributions within the receiver cavity produced by reflections from the solar collector. It was developed to model the offset solar collector of the solar dynamic electric power system being developed for Space Station Freedom. OFFSET has been used to improve the understanding of the collector-receiver interface and to guide the efforts of NASA contractors also researching the optical components of the power system. The collector for Space Station Freedom consists of 19 hexagonal panels each containing 24 triangular, reflective facets. Current research is geared toward optimizing flux distribution inside the receiver via changes in collector design and receiver orientation. OFFSET offers many options for experimenting with the design of the system. The offset parabolic collector model configuration is determined by an input file of facet corner coordinates. The user may choose other configurations by changing this file, but to simulate collectors that have other than 19 groups of 24 triangular facets would require modification of the FORTRAN code. Each of the roughly 500 facets in the assembled collector may be independently aimed to smooth out, or tailor, the flux distribution on the receiver's wall. OFFSET simulates the effects of design changes such as in receiver aperture location, tilt angle, and collector facet contour. Unique features of OFFSET include: 1) equations developed to pseudo-randomly select ray originating sources on the Sun which appear evenly distributed and include solar limb darkening; 2) Cone-optics technique used to add surface specular error to the ray originating sources to determine the apparent ray sources of the reflected sun; 3) choice of facet reflective surface contour -- spherical, ideal parabolic, or toroidal; 4) Gaussian distributions of radial and tangential components of surface slope error added to the surface normals at

  3. Troposphere delay modeling using ray-traced delays around Tsukuba during a 14-days typhoon period in September 2007

    NASA Astrophysics Data System (ADS)

    Pany, A.; Boehm, J.; Hobiger, T.; Schuh, H.

    2009-04-01

    Accurate modeling of the tropospheric delay of microwave signals is of great importance for space geodetic techniques, such as Very Long Baseline Interferometry (VLBI) and the Global Navigation Satellite Systems (GNSS). In state-of-the-art VLBI analysis tropospheric zenith delays are estimated using mapping functions, and gradients are applied in order to account for azimuthal asymmetries. Monte Carlo simulations carried out within the International VLBI Service for Geodesy and Astrometry (IVS) to design the next generation VLBI system, VLBI2010, have clearly shown that the tropospheric delay is the limiting factor in VLBI analysis and that a simple gradient model, as currently applied, might be insufficient for VLBI2010 which will provide a much higher observation density. The Japan Meteorological Agency (JMA) provides high resolution numerical weather models. With KARAT, the Kashima Ray-Tracing Tools, we computed tropospheric slant delays around the VLBI site in Tsukuba for a 14-days typhoon period in September 2007. The resolution of these ray-traced delays is 1° in both azimuth and elevation, and three hours in time. The delays exhibit significant azimuthally asymmetric characteristics. We fit spherical harmonic functions of different degrees and orders to the ray-traced delays in order to test their ability of modeling the spatial structures of the troposphere, and we investigate whether further continuation of the continued fraction form, i.e. estimating more coefficients, might improve troposphere modeling.

  4. Ray-tracing simulations of free-space optical channels for impulse response studies of indoor data links

    NASA Astrophysics Data System (ADS)

    Karppinen, Mikko; Aikio, Sanna M.; Maekinen, Jukka-Tapani; Rajaniemi, Hannu; Karioja, Pentti

    2000-04-01

    Free-space optical transmission provides large bandwidth, small size, lightweight, low cost and good security. Diffuse IR link configuration is also rather robust against shadowing. Its disadvantages are, however, bandwidth degradation due to multipath dispersion, sensitivity to ambient light and limited transmission distance due to the limitations of optical power budget. To specify the bandwidth and power budget requirements of the diffuse link, we performed ray-trace simulations for different room geometries and dimensions, and different transmitter and receiver locations. We considered both diffuse and specular reflections as well as shadowing and reflection effects due to blocking objects, such as furniture. The simulations were verified by analytically calculating the impulse response in simple diffuse reflection geometry. We also analyzed stray light induced shot noise effects. Furthermore, we simulated some properties of a quasi-diffuse link comprising of multi- beam transmitters with restricted beam divergences as well as detectors with narrow fields of view. Based on the study, novel Monte Carlo ray-tracing software packages, such as ASAP, can be used for diffuse link multipath dispersion and optical power path loss analysis. Ray tracing can also be used for parallel channel crosstalk and stray light analysis. Potential applications for these system are high- bit-rate wireless LANs and free-space optical interconnects.

  5. Magnetic smart material application to adaptive x-ray optics

    NASA Astrophysics Data System (ADS)

    Ulmer, M. P.; Graham, Michael E.; Vaynman, Semyon; Cao, J.; Takacs, Peter Z.

    2010-09-01

    We discuss a technique of shape modification that can be applied to thin walled ({100-400 micron thickness) electroformed replicated optics or slumped glass optics to improve the near net shape of the mirror as well as the midfrequency ripple. The process involves sputter deposition of a magnetic smart material (MSM) film onto a permanently magnetic material. The MSM material exhibits strains about 400 times stronger than ordinary ferromagnetic materials. The deformation process involves a magnetic write head which traverses the surface, and under the guidance of active metrology feedback, locally magnetizes the surface to impart strain where needed. Designs and basic concepts as applied to space borne X-ray optics will be described.

  6. Trace metal determinations by total-reflection X-ray fluorescence analysis in the open Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Schmidt, Diether; Gerwinski, Wolfgang; Radke, Ina

    1993-02-01

    The Intergovernmental Oceanographic Commission (IOC), as a major component of its programme "Global Investigation of Pollution in the Marine Environment" (GIPME), maintains a long-standing project on "Open Ocean Baseline Studies of Trace Contaminants". Initially, the Atlantic Ocean and trace metals were selected. A first cruise with the RVMeteor to the eastern parts of the south and north Atlantic Ocean was successfully organized, in March and April 1990, from Cape Town (South Africa) to Funchal (Madeira, Portugal). Thirteen scientists from laboratories in Europe and North America participated with the first author as coordinator. Four deep-water stations in the Cape Basin, Angola Basin, Cape Verde Abyssal Plain and Seine Abyssal Plain were regularly sampled for at least 36 depths. Additional samples were taken between stations. Samples were distributed to participants and a similar number of additional laboratories. As a central part of our own contribution to the project, we determined the trace heavy metals manganese, nickel, copper, zinc and lead and the lighter selenium by total-reflection X-ray fluorescence analysis. Additional methods applied, interalia, were anodic stripping voltammetry for lead and cadmium and graphite furnace atomic absorption spectrometry (GFAAS) for cadmium, using two different extraction procedures. For the TXRF, the pre-enrichment of the trace metals and the separation from the salt matrix were performed by complexation with sodium dibenzyldithiocarbamate and reverse-phase chromatography. Generally, very low levels of trace elements were found in filtered and unaltered water samples from these remote areas of the open Atlantic Ocean. Typical examples of the distributions of trace metal concentrations on depth profiles from the four deep-water stations as well as intercomparisons between the stations are presented.

  7. Cerebral Arteries Extraction using Level Set Segmentation and Adaptive Tracing for CT Angiography

    SciTech Connect

    Zhang Yong; Zhou Xiaobo; Srinivasan, Ranga; Wong, Stephen T. C.; Young, Geoff

    2007-11-02

    We propose an approach for extracting cerebral arteries from partial Computed Tomography Angiography (CTA). The challenges of extracting cerebral arteries from CTA come from the fact that arteries are usually surrounded by bones and veins in the lower portion of a CTA volume. There exists strong intensity-value overlap between vessels and surrounding objects. Besides, it is inappropriate to assume the 2D cross sections of arteries are circle or ellipse, especially for abnormal vessels. The navigation of the arteries could change suddenly in the 3D space. In this paper, a method based on level set segmentation is proposed to target this challenging problem. For the lower portion of a CTA volume, we use geodesic active contour method to detect cross section of arteries in the 2D space. The medial axis of the artery is obtained by adaptively tracking along its navigation path. This is done by finding the minimal cross section from cutting the arteries under different angles in the 3D spherical space. This method is highly automated, with minimum user input of providing only the starting point and initial navigation direction of the arteries of interests.

  8. Non-destructive trace element microanalysis of as-received cometary nucleus samples using synchrotron x ray fluorescence

    NASA Technical Reports Server (NTRS)

    Sutton, S. R.

    1989-01-01

    The Synchrotron X ray Fluorescence (SXRF) microprobe at the National Synchrotron Light Source (NSLS), Brookhaven National Laboratory, will be an excellent instrument for non-destructive trace element analyses of cometary nucleus samples. Trace element analyses of as-received cometary nucleus material will also be possible with this technique. Bulk analysis of relatively volatile elements will be important in establishing comet formation conditions. However, as demonstrated for meteorites, microanalyses of individual phases in their petrographic context are crucial in defining the histories of particular components in unequilibrated specimens. Perhaps most informative in comparing cometary material with meteorites will be the halogens and trace metals. In-situ, high spatial resolution microanalyses will be essential in establishing host phases for these elements and identifying terrestrial (collection/processing) overprints. The present SXRF microprobe is a simple, yet powerful, instrument in which specimens are excited with filtered, continuum synchrotron radiation from a bending magnet on a 2.5 GeV electron storage ring. A refrigerated cell will be constructed to permit analyses at low temperatures. The cell will consist essentially of an air tight housing with a cold stage. Kapton windows will be used to allow the incident synchrotron beam to enter the cell and fluorescent x rays to exit it. The cell will be either under vacuum or continuous purge by ultrapure helium during analyses. Several other improvements of the NSLS microprobe will be made prior to the cometary nucleus sample return mission that will greatly enhance the sensitivity of the technique.

  9. One-time ray-tracing optimization method and its application to the design of an illuminator for a tube photo-bioreactor.

    PubMed

    Chu, Shu-Chun; Yang, Hai-Li; Liao, Yi-Hong; Wu, Hong-Yu; Wang, Chi

    2014-03-10

    This study details a one-time ray-tracing optimization method for the optimization of LED illumination systems [S.-C. Chu and H.-L. Yang, "One-time ray-tracing method for the optimization of illumination system," in Proceedings of International Conference on Optics in Precision Engineering and Nanotechnology (icOPEN, 2013), 87692M]. This method optimizes the performance of illumination systems by modifying the light source's radiant intensity distribution with a freeform lens, instead of modifying the illumination system structure. Because illumination system structures are unchanged in the design process, a designer can avoid the common problems faced when designing illumination systems, i.e., the repeated and time-consuming ray-tracing process when optimizing the illumination system parameters. The easy approaches of the proposed optimization method to sample the target illumination areas and to divide the light source radiant intensity distribution make the proposed method can be applied to both direct-lit and non-direct-lit illumination systems. To demonstrate the proposed method, this study designs an illuminator for a tube photo-bioreactor using the proposed one-time ray-tracing method. A comparison shows that in the designing of the photo-bioreactor, tracing all rays one time requires about 13 hours, while optimizing the light source's radiant intensity distribution requires only about twenty minutes. The considerable reduction in the ray-tracing time shows that the proposed method is a fast and effective way to design illumination systems. PMID:24663876

  10. New X-ray microprobe system for trace heavy element analysis using ultraprecise X-ray mirror optics of long working distance

    NASA Astrophysics Data System (ADS)

    Terada, Yasuko; Yumoto, Hirokatsu; Takeuchi, Akihisa; Suzuki, Yoshio; Yamauchi, Kazuto; Uruga, Tomoya

    2010-05-01

    A new X-ray microprobe system for trace heavy element analysis using ultraprecise X-ray mirror optics of 300 mm long working distance has been developed at beamline 37XU of SPring-8. A focusing test has been performed in the X-ray energy range 20-37.7 keV. A focused beam size of 1.3 μm ( V)×1.5 μm ( H) has been achieved at an X-ray energy of 30 keV, and a total photon flux of the focused beam was about 2.7×10 10 photons/s. Micro-X-ray fluorescence (μ-XRF) analysis of eggplant roots has been carried out using the developed microprobe. It is clearly observed in the XRF images that cadmium is highly accumulated in the endodermis, exodermis and epidermis of roots. This study demonstrates the potential of scanning microscopy for heavy elements analysis in the high-energy X-ray region.

  11. Ray Tracing through the Edge Focusing of Rectangular Benders and an Improved Model for the Los Alamos Proton Storage Ring

    SciTech Connect

    Kolski, Jeffrey S.; Barlow, David B.; Macek, Robert J.; McCrady, Rodney C.

    2011-01-01

    Particle ray tracing through simulated 3D magnetic fields was executed to investigate the effective quadrupole strength of the edge focusing of the rectangular bending magnets in the Los Alamos Proton Storage Ring (PSR). The particle rays receive a kick in the edge field of the rectangular dipole. A focal length may be calculated from the particle tracking and related to the fringe field integral (FINT) model parameter. This tech note introduces the baseline lattice model of the PSR and motivates the need for an improvement in the baseline model's vertical tune prediction, which differs from measurement by .05. An improved model of the PSR is created by modifying the fringe field integral parameter to those suggested by the ray tracing investigation. This improved model is then verified against measurement at the nominal PSR operating set point and at set points far away from the nominal operating conditions. Lastly, Linear Optics from Closed Orbits (LOCO) is employed in an orbit response matrix method for model improvement to verify the quadrupole strengths of the improved model.

  12. Semi-analytic ray tracing method for time-efficient computing of transmission behavior of PCB level optical interconnects with varying core cross sections

    NASA Astrophysics Data System (ADS)

    Stübbe, Oliver

    2015-03-01

    Optical interconnects on printed circuit board level are a promising choice to support high bandwidth for short distance interconnects. These interconnects consists of highly multimode step index waveguides with rectangular core cross sections. Therefore ray tracing is an excellent method to determine the optical path parameters, e.g. optical power, ray path lengths and local ray directions. Based on these parameters the step response, the transient transfer function and the coupling behavior can be calculated. Classical ray tracing methods calculates the optical path parameters of each ray by successively computing internal reflections until a termination condition is reached. Therefore the computing time depends on the number of internal reflections. If the optical waveguide consists of cascaded straight and curved segments, e. g. point-to-point interconnects, one can use the analytic ray tracing method to determine the optical path parameters. The whole path parameters of each ray are determined by one analytical computation. The computing time depends on the number of segments. The analytic ray tracing method is unusable to determine ray path parameters of segments with varying core cross sections, e.g. tapers, crossings, splitters and combiners.

  13. Observation of the Z mode with DE 1 and its analysis by three-dimensional ray tracing

    NASA Technical Reports Server (NTRS)

    Hashimoto, Kozo; Calvert, Wynne

    1990-01-01

    Certain Z-mode wave emissions in the earth's magnetosphere have been identified using the wave spectra and polarization measurements of the DE 1 satellite. Although such emissions accompany the aurora, and thus presumably originate from the evening-sector auroral zone, they are found to occur over much wider ranges of latitude and longitude. Since the predicted cyclotron maser emission at the cyclotron frequency could not have produced waves which travel such great distances, as shown by three-dimensional ray tracing, it is proposed instead that these emissions must originate from lower altitudes within the auroral zone and probably from near the plasma frequency inside the auroral plasma cavity.

  14. A 3-dimensional ray-trace model for predicting the performance of flashlamp-pumped laser amplifiers

    SciTech Connect

    Jancaitis, K.S.; Haney, S.W.; Munro, D.H.; Le Touze, G.; Cabourdin, O.

    1997-02-13

    We have developed a fully three-dimensional model for the performance of flashlamp pumped laser amplifiers. The model uses a reverse ray-trace technique to calculate the pumping of the laser glass by the flashlamp radiation. We have discovered several different methods by which we can speed up the calculation of the gain profile in a amplifier. The model predicts the energy-storage performance of the Beamlet amplifiers to better than 5%. This model will be used in the optimization of the National Ignition Facility (NIF) amplifier design.

  15. Full automatic preprocessing of digital map for 2.5D ray tracing propagation model in urban microcellular environment

    NASA Astrophysics Data System (ADS)

    Liu, Zhong-Yu; Guo, Li-Xin; Tao, Wei

    2013-08-01

    Due to the importance of digital map to ray-tracing (RT) algorithm, intelligent preprocessing techniques for the geometric information of buildings are improved, taking into account the characteristic of quasi three-dimensional (2.5D) RT method. By using these techniques, the geometrical factors, which have little or no effect on the prediction results, are neglected from the digital map, and the reduction of the number of blocking test is achieved in the process of executing the RT routine. With the proposed preprocessing of the digital map in urban microcellular environments, the improvement in the computational efficiency is clearly demonstrated without sensibly affecting the accuracy of the propagation prediction.

  16. Optical analysis of a curved-slats fixed-mirror solar concentrator by a forward ray-tracing procedure.

    PubMed

    Pujol Nadal, Ramon; Martínez Moll, Víctor

    2013-10-20

    Fixed-mirror solar concentrators (FMSCs) use a static reflector and a moving receiver. They are easily installable on building roofs. However, for high-concentration factors, several flat mirrors would be needed. If curved mirrors are used instead, high-concentration levels can be achieved, and such a solar concentrator is called a curved-slats fixed-mirror solar concentrator (CSFMSC), on which little information is available. Herein, a methodology is proposed to characterize the CSFMSC using 3D ray-tracing tools. The CSFMSC shows better optical characteristics than the FMSC, as it needs fewer reflector segments for achieving the same concentration and optical efficiency. PMID:24216595

  17. Classification of osteosarcoma T-ray responses using adaptive and rational wavelets for feature extraction

    NASA Astrophysics Data System (ADS)

    Ng, Desmond; Wong, Fu Tian; Withayachumnankul, Withawat; Findlay, David; Ferguson, Bradley; Abbott, Derek

    2007-12-01

    In this work we investigate new feature extraction algorithms on the T-ray response of normal human bone cells and human osteosarcoma cells. One of the most promising feature extraction methods is the Discrete Wavelet Transform (DWT). However, the classification accuracy is dependant on the specific wavelet base chosen. Adaptive wavelets circumvent this problem by gradually adapting to the signal to retain optimum discriminatory information, while removing redundant information. Using adaptive wavelets, classification accuracy, using a quadratic Bayesian classifier, of 96.88% is obtained based on 25 features. In addition, the potential of using rational wavelets rather than the standard dyadic wavelets in classification is explored. The advantage it has over dyadic wavelets is that it allows a better adaptation of the scale factor according to the signal. An accuracy of 91.15% is obtained through rational wavelets with 12 coefficients using a Support Vector Machine (SVM) as the classifier. These results highlight adaptive and rational wavelets as an efficient feature extraction method and the enormous potential of T-rays in cancer detection.

  18. A RAY-TRACING ALGORITHM FOR SPINNING COMPACT OBJECT SPACETIMES WITH ARBITRARY QUADRUPOLE MOMENTS. I. QUASI-KERR BLACK HOLES

    SciTech Connect

    Psaltis, Dimitrios; Johannsen, Tim

    2012-01-20

    We describe a new numerical algorithm for ray tracing in the external spacetimes of spinning compact objects characterized by arbitrary quadrupole moments. Such spacetimes describe non-Kerr vacuum solutions that can be used to test the no-hair theorem in conjunction with observations of accreting black holes. They are also appropriate for neutron stars with spin frequencies in the {approx_equal} 300-600 Hz range, which are typical of the bursting sources in low-mass X-ray binaries. We use our algorithm to show that allowing for the quadrupole moment of the spacetime to take arbitrary values leads to observable effects in the profiles of relativistic broadened fluorescent iron lines from geometrically thin accretion disks.

  19. Intelligent Simultaneous Quantitative Online Analysis of Environmental Trace Heavy Metals with Total-Reflection X-Ray Fluorescence

    PubMed Central

    Ma, Junjie; Wang, Yeyao; Yang, Qi; Liu, Yubing; Shi, Ping

    2015-01-01

    Total-reflection X-ray fluorescence (TXRF) has achieved remarkable success with the advantages of simultaneous multi-element analysis capability, decreased background noise, no matrix effects, wide dynamic range, ease of operation, and potential of trace analysis. Simultaneous quantitative online analysis of trace heavy metals is urgently required by dynamic environmental monitoring and management, and TXRF has potential in this application domain. However, it calls for an online analysis scheme based on TXRF as well as a robust and rapid quantification method, which have not been well explored yet. Besides, spectral overlapping and background effects may lead to loss of accuracy or even faulty results during practical quantitative TXRF analysis. This paper proposes an intelligent, multi-element quantification method according to the established online TXRF analysis platform. In the intelligent quantification method, collected characteristic curves of all existing elements and a pre-estimated background curve in the whole spectrum scope are used to approximate the measured spectrum. A novel hybrid algorithm, PSO-RBFN-SA, is designed to solve the curve-fitting problem, with offline global optimization and fast online computing. Experimental results verify that simultaneous quantification of trace heavy metals, including Cr, Mn, Fe, Co, Ni, Cu and Zn, is realized on the online TXRF analysis platform, and both high measurement precision and computational efficiency are obtained. PMID:25954949

  20. Intelligent simultaneous quantitative online analysis of environmental trace heavy metals with total-reflection X-ray fluorescence.

    PubMed

    Ma, Junjie; Wang, Yeyao; Yang, Qi; Liu, Yubing; Shi, Ping

    2015-01-01

    Total-reflection X-ray fluorescence (TXRF) has achieved remarkable success with the advantages of simultaneous multi-element analysis capability, decreased background noise, no matrix effects, wide dynamic range, ease of operation, and potential of trace analysis. Simultaneous quantitative online analysis of trace heavy metals is urgently required by dynamic environmental monitoring and management, and TXRF has potential in this application domain. However, it calls for an online analysis scheme based on TXRF as well as a robust and rapid quantification method, which have not been well explored yet. Besides, spectral overlapping and background effects may lead to loss of accuracy or even faulty results during practical quantitative TXRF analysis. This paper proposes an intelligent, multi-element quantification method according to the established online TXRF analysis platform. In the intelligent quantification method, collected characteristic curves of all existing elements and a pre-estimated background curve in the whole spectrum scope are used to approximate the measured spectrum. A novel hybrid algorithm, PSO-RBFN-SA, is designed to solve the curve-fitting problem, with offline global optimization and fast online computing. Experimental results verify that simultaneous quantification of trace heavy metals, including Cr, Mn, Fe, Co, Ni, Cu and Zn, is realized on the online TXRF analysis platform, and both high measurement precision and computational efficiency are obtained. PMID:25954949

  1. Ray tracing flux calculation for the small and wide angle x-ray scattering diffraction station at the SESAME synchrotron radiation facility

    SciTech Connect

    Salah, Wa'el; Sanchez del Rio, M.; Hoorani, H.

    2009-09-15

    The calculation for the optics of the synchrotron radiation small and wide angle x-ray scattering beamline, currently under construction at SESAME is described. This beamline is based on a cylindrically bent germanium (111) single crystal with an asymmetric cut of 10.5 deg., followed by a 1.2 m long rhodium coated plane mirror bent into a cylindrical form. The focusing properties of bent asymmetrically cut crystals have not yet been studied in depth. The present paper is devoted to study of a particular application of a bent asymmetrically cut crystal using ray tracing simulations with the SHADOW code. These simulations show that photon fluxes of order of 1.09x10{sup 11} photons/s will be available at the experimental focus at 8.79 keV. The focused beam dimensions will be 2.2 mm horizontal full width at half maximum (FWHM) by 0.12 mm vertical (FWHM).

  2. Comparison of a 3-D GPU-Assisted Maxwell Code and Ray Tracing for Reflectometry on ITER

    NASA Astrophysics Data System (ADS)

    Gady, Sarah; Kubota, Shigeyuki; Johnson, Irena

    2015-11-01

    Electromagnetic wave propagation and scattering in magnetized plasmas are important diagnostics for high temperature plasmas. 1-D and 2-D full-wave codes are standard tools for measurements of the electron density profile and fluctuations; however, ray tracing results have shown that beam propagation in tokamak plasmas is inherently a 3-D problem. The GPU-Assisted Maxwell Code utilizes the FDTD (Finite-Difference Time-Domain) method for solving the Maxwell equations with the cold plasma approximation in a 3-D geometry. Parallel processing with GPGPU (General-Purpose computing on Graphics Processing Units) is used to accelerate the computation. Previously, we reported on initial comparisons of the code results to 1-D numerical and analytical solutions, where the size of the computational grid was limited by the on-board memory of the GPU. In the current study, this limitation is overcome by using domain decomposition and an additional GPU. As a practical application, this code is used to study the current design of the ITER Low Field Side Reflectometer (LSFR) for the Equatorial Port Plug 11 (EPP11). A detailed examination of Gaussian beam propagation in the ITER edge plasma will be presented, as well as comparisons with ray tracing. This work was made possible by funding from the Department of Energy for the Summer Undergraduate Laboratory Internship (SULI) program. This work is supported by the US DOE Contract No.DE-AC02-09CH11466 and DE-FG02-99-ER54527.

  3. Ray-tracing WKB analysis of Whistler waves in non-uniform magnetic fields applied to space thrusters

    NASA Astrophysics Data System (ADS)

    Cardinali, A.; Melazzi, D.; Manente, M.; Pavarin, D.

    2014-02-01

    Radiofrequency magnetized cylindrical plasma sources are proposed for the development of space thrusters, whose thrust efficiency and specific impulse depend on the power coupled into the plasma. At this stage of research, emphasis has been on the absorption of Whistler wave energy by non-uniform plasmas but not much on the role played by the magneto-static confinement field, considered uniform, constant and aligned with the axis of the source. We present RAYWh (RAY-tracing Whistler), a three-dimensional (3D) ray-tracing solver for electromagnetic propagation and power deposition in cylindrical plasma sources for space plasma thrusters, where actual magnetic confinement configurations along with plasma density profiles are included. The propagation and absorption of Whistler waves are investigated by solving the 3D Maxwell-Vlasov model equations by a Wentzel-Kramers-Brillouin (WKB) asymptotic expansion. The reduced set of equations for the wave phase and for the square amplitude of the electric field is solved numerically by means of a modified Runge-Kutta algorithm. Unexpected cut-offs, resonances, radial reflections, mode conversions and power deposition profile of the excited waves are found, when realistic confinement magnetic fields are considered. An analysis of the influence of axial wavenumbers and the axial length of the system on the power deposition is presented.

  4. Hiss induced radiation belt electron loss timescales in the plasmasphere based on ray tracings of wave propagation angle

    NASA Astrophysics Data System (ADS)

    Zhou, C.; Ni, B.; Li, W.; Bortnik, J.; Gu, X.; Zhao, Z.

    2015-12-01

    Plasmaspheric hiss plays an important role in driving resonant scattering losses of radiation belt electrons and thereby largely controls the lifetimes of electrons in the plasmasphere. Besides the spectral information of waves, an accurate investigation of hiss induced radiation belt electron loss timescales requires the details of wave normal angle distribution during propagation along the field line, which however is difficult to obtain directly from in situ measurements but can be reasonably evaluated from ray tracing of hiss propagation on basis of reasonable setups of background field and plasma density. By assuming a nominal and suitable plasmapause location at L = 4.5, we report the ray tracing results of hiss wave propagation angles for various hiss wave frequencies at various L-shells in the plasmasphere. Subsequently, we construct the improved model of hiss wave normal angle distribution with dependence on both wave frequency, magnetic latitude and L-shell, which is used to compute the quasi-linear bounce-averaged rates of electron scattering due to plasmaspheric hiss and perform the pure pitch angle diffusion simulations. Hiss induced radiation belt electron loss timescales are then determined from the simulated temporal evolution of electron fluxes after reaching the equilibrium state, as a function of electron kinetic energy and L-shell, which is of importance for incorporation into future simulations of the radiation belt electron dynamics under various geomagnetic conditions to comprehend the exact contribution of plasmaspheric hiss.

  5. Elimination of 'ghost'-effect-related systematic error in metrology of X-ray optics with a long trace profiler

    SciTech Connect

    Yashchuk, Valeriy V.; Irick, Steve C.; MacDowell, Alastair A.

    2005-04-28

    A data acquisition technique and relevant program for suppression of one of the systematic effects, namely the ''ghost'' effect, of a second generation long trace profiler (LTP) is described. The ''ghost'' effect arises when there is an unavoidable cross-contamination of the LTP sample and reference signals into one another, leading to a systematic perturbation in the recorded interference patterns and, therefore, a systematic variation of the measured slope trace. Perturbations of about 1-2 {micro}rad have been observed with a cylindrically shaped X-ray mirror. Even stronger ''ghost'' effects show up in an LTP measurement with a mirror having a toroidal surface figure. The developed technique employs separate measurement of the ''ghost''-effect-related interference patterns in the sample and the reference arms and then subtraction of the ''ghost'' patterns from the sample and the reference interference patterns. The procedure preserves the advantage of simultaneously measuring the sample and reference signals. The effectiveness of the technique is illustrated with LTP metrology of a variety of X-ray mirrors.

  6. Integrated Ray Tracing simulation of the SCOTS surface measurement test for the GMT Fast Steering Mirror Prototype

    NASA Astrophysics Data System (ADS)

    Choi, Ji Nyeong; Ryu, Dongok; Kim, Sug-Whan; Kim, Dae Wook; Su, Peng; Huang, Run; Kim, Young-Soo; Yang, Ho-Soon

    2015-12-01

    Software Configurable Optical Testing System (SCOTS) is one of relatively new optical testing methods for large optical surfaces and uses the principle of Phase Measuring Deflectometry (PMD). A camera captures images of the target surface illuminated by a light source screen with patterns. Then, the surface slope and height are obtained by camera image analysis. In the meantime, Integrated Ray Tracing (IRT) concept was developed for the simultaneous end-to-end imaging and radiometric performance simulation of space instruments. It incorporates a light source, medium, target and observing instrument into single computation environment for real scale ray tracing. In this study, we combined these two techniques for the development of an optical testing simulation model applicable to testing the secondary mirror (M2) of Giant Magellan Telescope (GMT). Using the IRT SCOTS model, we simulated SCOTS test runs and reconstructed its surface slopes and heights from the simulated image data. The result shows 1.05 nm rms in difference between the input and reconstructed surface heights. It demonstrates the high fidelity of the suggested IRT approach showing nanometer level numerical accuracy and therefore it shows the potential applicability of the IRT simulation technique to SCOTS test method for large precision optical surfaces.

  7. Optimization of sample preparation for grazing emission X-ray fluorescence in micro- and trace analysis applications

    NASA Astrophysics Data System (ADS)

    Claes, Martine; de Bokx, Pieter; Willard, Nico; Veny, Paul; Van Grieken, René

    1997-07-01

    Grazing emission X-ray fluorescence (GEXRF) is a new development in X-ray fluorescence analysis related to total-reflection XRF. An optical flat carrying the sample is irradiated at an angle of approximately 90° with an uncollimated polychromatic X-ray beam. The emitted fluorescent radiation of the sample elements is measured at very small angles using wavelength dispersive detection. For the application of GEXRF in micro- and trace analysis, a sample preparation procedure for analysis of liquid samples has been developed. Polycarbonate was investigated as a possible material for the sample carrier. Homogeneous distribution of the sample on the support was achieved by special pre-treatment of the carrier. This pre-treatment includes siliconizing the polycarbonate disks with Serva silicone solution, after which the siliconized carriers are placed in an oxygen plasma asher. Finally, to obtain a spot of the same size as the X-ray beam (≈30 mm diameter), a thin silicone layer is placed as a ring on the carriers with an ear pick. Electron microprobe analyses were performed to check the distribution of the liquid sample deposit, and GEXRF measurements were used to check the reproducibility of sample preparation.

  8. Investigating the role for adaptation of the microbial community to transform trace organic chemicals during managed aquifer recharge.

    PubMed

    Alidina, Mazahirali; Li, Dong; Drewes, Jörg E

    2014-06-01

    This study was undertaken to investigate whether adaptation by pre-exposure to trace organic chemicals (TOrCs) was necessary for microbial transformation during managed aquifer recharge (MAR). Two pairs of laboratory-scale soil columns, each receiving a different primary substrate, were utilized to simulate the dominant bulk organic carbon present in MAR systems receiving wastewater effluent of varying quality and having undergone different degrees of pre-treatment, as well as organic carbon prevalent at different stages of subsurface travel. Each pair of columns consisted of duplicate set-ups receiving the same feed solution with only one pre-exposed to a suite of eight TOrCs for approximately ten months. Following the pre-exposure period, a spiking experiment was conducted in which the non-exposed columns also received the same suite of TOrCs. TOrC attenuation was quantified for the pre- and non-exposed columns of each pair during the spiking experiment. The microbial community structure and function of these systems were characterized by pyrosequencing of 16S rRNA gene and metagenomics, respectively. Biotransformation rather than sorption was identified as the dominant removal mechanism for almost all the TOrCs (except triclocarban). Similar removal efficiencies were observed between pre-exposed and non-exposed columns for most TOrCs. No obvious differences in microbial community structure were revealed between pre- and non-exposed columns. Using metagenomics, biotransformation capacity potentials of the microbial community present were also similar between pre- and non-exposed columns of each pair. Overall, the pre-exposure of MAR systems to TOrCs at ng/L levels did not affect their attenuation and had no obvious influence on the resulting microbial community structure and function. Thus, other factors such as bioavailability of the primary substrate play a greater role regarding biotransformation of TOrCs. These results indicate that MAR systems adapted to a

  9. Auxiliary probe design adaptable to existing probes for remote detection NMR, MRI, and time-of-flight tracing.

    PubMed

    Han, Songi; Granwehr, Josef; Garcia, Sandra; McDonnell, Erin E; Pines, Alexander

    2006-10-01

    A versatile, detection-only probe design is presented that can be adapted to any existing NMR or MRI probe with the purpose of making the remote detection concept generally applicable. Remote detection suggests freeing the NMR experiment from the confinement of using the same radio frequency (RF) coil and magnetic field for both information encoding and signal detection. Information is stored during the encoding step onto a fluid sensor medium whose magnetization is later measured in a different location. The choice of an RF probe and magnetic field for encoding can be made based solely on the size and characteristics of the sample and the desired information quality without considering detection sensitivity, as this aspect is dealt with by a separate detector. While early experiments required building probes that included two resonant circuits, one for encoding and one for detection, a modular approach with a detection-only probe as presented here can be used along with any existing NMR probe of choice for encoding. The design of two different detection-only probes is presented, one with a saddle coil for milliliter-sized detection volumes, and the other one with a microsolenoid coil for sub-microliter fluid quantities. As example applications, we present time-of-flight (TOF) tracing of hyperpolarized (129)Xe spins in a gas mixture through coiled tubing using the microsolenoid coil detector and TOF flow imaging through a nested glass container where the gas flow changes its direction twice between inlet and outlet using the saddle coil detector. PMID:16875855

  10. An adaptive gating approach for x-ray dose reduction during cardiac interventional procedures

    SciTech Connect

    Abdel-Malek, A.; Yassa, F.; Bloomer, J. )

    1994-03-01

    The increasing number of cardiac interventional procedures has resulted in a tremendous increase in the absorbed x-ray dose by radiologists as well as patients. A new method is presented for x-ray dose reduction which utilizes adaptive tube pulse-rate scheduling in pulsed fluoroscopic systems. In the proposed system, pulse-rate scheduling depends on the heart muscle activity phase determined through continuous guided segmentation of the patient's electrocardiogram (ECG). Displaying images generated at the proposed adaptive nonuniform rate is visually unacceptable; therefore, a frame-filling approach is devised to ensure a 30 frame/sec display rate. The authors adopted two approaches for the frame-filling portion of the system depending on the imaging mode used in the procedure. During cine-mode imaging (high x-ray dose), collected image frame-to-frame pixel motion is estimated using a pel-recursive algorithm followed by motion-based pixel interpolation to estimate the frames necessary to increase the rate to 30 frames/sec. The other frame-filling approach is adopted during fluoro-mode imaging (low x-ray dose), characterized by low signal-to-noise ratio images. This approach consists of simply holding the last collected frame for as many frames as necessary to maintain the real-time display rate.

  11. Time-resolved non-sequential ray-tracing modelling of non-line-of-sight picosecond pulse LIDAR

    NASA Astrophysics Data System (ADS)

    Sroka, Adam; Chan, Susan; Warburton, Ryan; Gariepy, Genevieve; Henderson, Robert; Leach, Jonathan; Faccio, Daniele; Lee, Stephen T.

    2016-05-01

    The ability to detect motion and to track a moving object that is hidden around a corner or behind a wall provides a crucial advantage when physically going around the obstacle is impossible or dangerous. One recently demonstrated approach to achieving this goal makes use of non-line-of-sight picosecond pulse laser ranging. This approach has recently become interesting due to the availability of single-photon avalanche diode (SPAD) receivers with picosecond time resolution. We present a time-resolved non-sequential ray-tracing model and its application to indirect line-of-sight detection of moving targets. The model makes use of the Zemax optical design programme's capabilities in stray light analysis where it traces large numbers of rays through multiple random scattering events in a 3D non-sequential environment. Our model then reconstructs the generated multi-segment ray paths and adds temporal analysis. Validation of this model against experimental results is shown. We then exercise the model to explore the limits placed on system design by available laser sources and detectors. In particular we detail the requirements on the laser's pulse energy, duration and repetition rate, and on the receiver's temporal response and sensitivity. These are discussed in terms of the resulting implications for achievable range, resolution and measurement time while retaining eye-safety with this technique. Finally, the model is used to examine potential extensions to the experimental system that may allow for increased localisation of the position of the detected moving object, such as the inclusion of multiple detectors and/or multiple emitters.

  12. Thermal imaging of laser-tissue interaction using color Schlieren techniques quantified by ray-tracing simulation

    NASA Astrophysics Data System (ADS)

    Verdaasdonck, Rudolf M.; Lodder, Rogier; van Swol, Christiaan F. P.; Grimbergen, Matthijs C. M.

    1999-06-01

    In various studies the use of a color Schlieren technique to visualize the dynamic thermal effects of lasers in an aqueous environment has proven to be very useful. Besides for the research, this setup has also proven to be very successful for education and demonstration purposes. This 'pseudo thermal imaging' technique has also been applied to study the behavior of diathermia devices and ultrasound resectors used in surgery. Since, the images reflect gradients in refractive index induced by thermal gradients, they can not simply be converted and interpreted as thermal images. In order to understand the pathway of light through thermal gradients, a ray-trace program was developed. The program is capable of visualizing the path of light rays through simulated thermal gradients as well as generating an image, which can be compared with the 'real' images from the color Schlieren setup. For calibration, the program was successfully tested on well defined optical configurations such as spherical and index-gradient lenses. Images calculated using data from a temperature profile measured with a small thermocouple appeared to be almost similar to the actual Schlieren image. Matching the calculated and actual image was possible by either assuming a minimal error in the temperature measurements or in the temperature dependence of the refractive index. The ray-trace program has been a helpful tool to quantify the absolute temperatures in color images from simple geometries. Expanding the code might enable the quantification of more complex temperature gradients. Such information is valuable for the clinical application of energy source such as lasers.

  13. Development and application of a ray-tracing code integrating with 3D equilibrium mapping in LHD ECH experiments

    NASA Astrophysics Data System (ADS)

    Tsujimura, T., Ii; Kubo, S.; Takahashi, H.; Makino, R.; Seki, R.; Yoshimura, Y.; Igami, H.; Shimozuma, T.; Ida, K.; Suzuki, C.; Emoto, M.; Yokoyama, M.; Kobayashi, T.; Moon, C.; Nagaoka, K.; Osakabe, M.; Kobayashi, S.; Ito, S.; Mizuno, Y.; Okada, K.; Ejiri, A.; Mutoh, T.

    2015-11-01

    The central electron temperature has successfully reached up to 7.5 keV in large helical device (LHD) plasmas with a central high-ion temperature of 5 keV and a central electron density of 1.3× {{10}19} m-3. This result was obtained by heating with a newly-installed 154 GHz gyrotron and also the optimisation of injection geometry in electron cyclotron heating (ECH). The optimisation was carried out by using the ray-tracing code ‘LHDGauss’, which was upgraded to include the rapid post-processing three-dimensional (3D) equilibrium mapping obtained from experiments. For ray-tracing calculations, LHDGauss can automatically read the relevant data registered in the LHD database after a discharge, such as ECH injection settings (e.g. Gaussian beam parameters, target positions, polarisation and ECH power) and Thomson scattering diagnostic data along with the 3D equilibrium mapping data. The equilibrium map of the electron density and temperature profiles are then extrapolated into the region outside the last closed flux surface. Mode purity, or the ratio between the ordinary mode and the extraordinary mode, is obtained by calculating the 1D full-wave equation along the direction of the rays from the antenna to the absorption target point. Using the virtual magnetic flux surfaces, the effects of the modelled density profiles and the magnetic shear at the peripheral region with a given polarisation are taken into account. Power deposition profiles calculated for each Thomson scattering measurement timing are registered in the LHD database. The adjustment of the injection settings for the desired deposition profile from the feedback provided on a shot-by-shot basis resulted in an effective experimental procedure.

  14. Reconstruction of Chorus Type Whistler Waves Distribution in the Radiation Belts and Inner Magnetosphere Using Ray Tracing

    NASA Astrophysics Data System (ADS)

    Breuillard, H.; Zaliznyak, Y.; Agapitov, O.; Krasnoselskikh, V.; Rolland, G.

    2011-12-01

    The quasi-monochromatic whistler wave packets are supposed to be formed in the vicinity of the magnetic equator and are frequently observed for example by Cluster spacecraft. The objective of our study is a reconstruction of realistic distribution of chorus emissions in radiation belts and in inner magnetosphere. To achieve this aim the data from the electric and magnetic field measurements onboard Cluster satellite are used to determine the major characteristics of the chorus signal around the equator region, namely, its averaged wave vector, wave vector distribution, Poynting flux and polarization. Then the propagation of such a wave packet is modeled using ray tracing technique. We developed the original code which employs K. Rönnmark's WHAMP to obtain hot plasma dispersion function values along the wave packet trajectory. The observed (real) whistler wave distributions at the equator are first fitted to reproduce the observed waveform using Cluster observations (initial conditions) and then these rays are propagated numerically through the inner magnetosphere in the frame of the WKB approximation. The density distribution of the magnetospheric particles is taken from the Gallagher et al. package that is provided by the authors and distributed as free software. Ray tracing allows one to reconstruct the properties of waves such as electric and magnetic fields, and the width of the wavepacket in k-space along the propagation path. The calculations take into account realistic effects of the spreading of the signal due to propagation in the inhomogeneous and anisotropic magnetized plasma, the dependence of signal propagation characteristics upon initial conditions, etc. Our calculations make possible to follow the wave packets and calculate their properties in the desired regions, e.g. the regions where an efficient wave-particle interaction is expected to occur. We present here the comparison between the distributions obtained with the statistical data sets of

  15. Tracing the Reverberation Lag in the Hard State of Black Hole X-Ray Binaries

    NASA Astrophysics Data System (ADS)

    De Marco, B.; Ponti, G.; Muñoz-Darias, T.; Nandra, K.

    2015-11-01

    We report results obtained from a systematic analysis of X-ray lags in a sample of black hole X-ray binaries, with the aim of assessing the presence of reverberation lags and studying their evolution during outburst. We used XMM-Newton and simultaneous Rossi X-ray Timing Explorer (RXTE) observations to obtain broadband energy coverage of both the disk and the hard X-ray Comptonization components. In most cases the detection of reverberation lags is hampered by low levels of variability-power signal-to-noise ratio (typically when the source is in a soft state) and/or short exposure times. The most detailed study was possible for GX 339-4 in the hard state, which allowed us to characterize the evolution of X-ray lags as a function of luminosity in a single source. Over all the sampled frequencies (˜0.05-9 Hz), we observe the hard lags intrinsic to the power-law component, already well known from previous RXTE studies. The XMM-Newton soft X-ray response allows us to detail the disk variability. At low frequencies (long timescales) the disk component always leads the power-law component. On the other hand, a soft reverberation lag (ascribable to thermal reprocessing) is always detected at high frequencies (short timescales). The intrinsic amplitude of the reverberation lag decreases as the source luminosity and the disk fraction increase. This suggests that the distance between the X-ray source and the region of the optically thick disk where reprocessing occurs gradually decreases as GX 339-4 rises in luminosity through the hard state, possibly as a consequence of reduced disk truncation.

  16. 3-D x-ray mirror metrology with a vertical scanning long trace profiler

    SciTech Connect

    Takacs, P.Z.; Li, H.; Li, X.; Grindel, M.W.

    1996-09-01

    The long trace profiler (LTP) was originally developed at Brookhaven National Laboratory for the specific purpose of measuring the surface figure of large cylindrical mirrors used at grazing incidence in synchrotron radiation (SR) beamlines. In its original configuration, it could measure only along one line down the center of the cylinder. A single linear profile is often sufficient to gauge the quality of the optical surface on these kinds of mirrors. For some applications it is necessary to measure the topography of the entire surface, not just along one line but over a grid that covers the entire surface area. We have modified a standard LTP to enable measurement of the complete surface of Wolter telescope optics in a vertical configuration. The vertical scanning LTP (VSLTP) is capable of producing a complete 3-D map of the surface topography errors relative to the ideal desired surface on complete segments of paraboloids and hyperboloids. The instrument uses a penta prism assembly to scan the probe beam in the longitudinal direction parallel to the mirror symmetry axis and uses a precision rotary stage to provide scans in the azimuthal direction. A Risley prism pair and a dove prism are used to orient the probe beam in the proper direction for the azimuthal scans. The repeatability of the prototype instrument is better than 20 nm over trace lengths of 35 mm with a slope measurement accuracy of about 1 microradian. {copyright} {ital 1996 American Institute of Physics.}

  17. Atmospheric Delay Reduction using Ray Tracing Technique through Meso-scale Numerical Weather Data for Space Geodesy

    NASA Astrophysics Data System (ADS)

    Ichikawa, Ryuichi; Hobiger, Thomas; Shoji, Yoshinori; Koyama, Yasuhiro; Kondo, Tesuro

    2010-05-01

    We have been developing a state-of-art tool to estimate the atmospheric path delays by ray-tracing through meso-scale analysis (MANAL data) data with 10km grid interval, which is operationally used for numerical weather prediction by Japan Meteorological Agency (JMA). The tools, which we have named 'KAshima RAytracing Tools (KARAT)', are capable of calculating total slant delays and ray-bending angles considering real atmospheric phenomena. The KARAT can estimate atmospheric slant delays by three different calculation schemes. These are (1) a piece-wise linear propagation, (2) an analytical 2-D ray-propagation model by Thayer, and (3) a 3-D Eikonal solver. By computing GPS PPP solutions for 57 GPS sites of the GEONET (GPS Earth Observation Network System) operated by Geographical Survey Institute (GSI) of Japan it could be shown that KARAT performs slightly better than results based on the Global Mapping Function (GMF) and the Vienna Mapping Function 1 (VMF1), whereas for the latter two also linear gradient models had to be applied. The grid interval of the MANAL data was updated from 10km to 5km on April 7, 2009. In addition, on October 27, 2009 the JMA started data assimilation of zenith wet delay obtained by the GEONET for meso-scale numerical weather prediction. We are now evaluating impacts of data scheme improvements and assimilation strategy change on the slant delay reduction. We will include these preliminary results in our presentation.

  18. Direct inversion of surface wave dispersion for three-dimensional shallow crustal structure based on ray tracing: methodology and application

    NASA Astrophysics Data System (ADS)

    Fang, Hongjian; Yao, Huajian; Zhang, Haijiang; Huang, Yu-Chih; van der Hilst, Robert D.

    2015-06-01

    We propose a method to invert surface wave dispersion data directly for 3-D variations of shear wave speed, that is, without the intermediate step of phase or group velocity maps, using frequency-dependent ray tracing and a wavelet-based sparsity-constrained tomographic inversion. A fast marching method is used to compute, at each period, surface wave traveltimes and ray paths between sources and receivers. This avoids the assumption of great-circle propagation that is used in most surface wave tomographic studies, but which is not appropriate in complex media. To simplify the problem we consider quasi-stratified media with smoothly varying seismic properties. We represent the 3-D shear wave speed model by means of 1-D profiles beneath grid points, which are determined from all dispersion data simultaneously using a wavelet-based sparsity-constrained tomographic method. The wavelet coefficients of the wave speed model are estimated with an iteratively reweighted least squares algorithm, and upon iteration the surface wave ray paths and the data sensitivity matrix are updated using the newly obtained wave speed model. To demonstrate its feasibility, we apply the method to determine the 3-D shallow crustal shear wave speed variations in the Taipei basin of Taiwan using short period interstation Rayleigh wave phase velocity dispersion measurements extracted from the ambient noise cross-correlation method. The results are consistent with previous studies and reveal strong shallow crustal heterogeneity that correlates with surface geology.

  19. The ray tracing analytical solution within the RAMOD framework. The case of a Gaia-like observer

    NASA Astrophysics Data System (ADS)

    Crosta, M.; Vecchiato, A.; de Felice, F.; Lattanzi, M. G.

    2015-08-01

    This paper presents the analytical solution of the inverse ray tracing problem for photons emitted by a star and collected by an observer located in the gravitational field of the Solar System. This solution has been conceived to suit the accuracy achievable by the ESA Gaia satellite (launched on 19 December 2013) consistently with the measurement protocol in General Relativity adopted within the RAMOD framework. The aim of this study is to provide a general relativistic tool for the science exploitation of such a revolutionary mission, whose main goal is to trace back star directions from within our local curved space-time, therefore providing a three-dimensional map of our Galaxy. The calculations are performed assuming that the massive bodies of the Solar System move uniformly and have monopole and quadrupole structures. The results are useful for a thorough comparison and cross-checking validation of what already exists in the field of relativistic astrometry. Moreover, the analytical solutions presented here can be extended to model other measurements that require the same order of accuracy as that expected for Gaia.

  20. Ray tracing of whistler-mode chorus elements: implications for generation mechanisms of rising and falling tone emissions

    NASA Astrophysics Data System (ADS)

    Yamaguchi, K.; Matsumuro, T.; Omura, Y.; Nunn, D.

    2013-04-01

    Using a well-established magnetospheric very-low-frequency (VLF) ray tracing method, in this work we trace the propagation of individual rising- and falling-frequency elements of VLF chorus from their generation point in the equatorial region of the magnetosphere through to at least one reflection at the lower-hybrid resonance point. Unlike recent work by Bortnik and co-workers, whose emphasis was on demonstrating that magnetospheric hiss has its origins in chorus, we here track the motion in the equatorial plane of the whole chorus element, paying particular regard to movement across field lines, rotation, and compression or expansion of the wave pulse. With a generation point for rising chorus at the equator, it was found the element wave pulse remained largely field aligned in the generation region. However, for a falling tone generation point at 4000 km upstream from the equator, by the time the pulse crosses the equator the wavefield had substantial obliquity, displacement, and compression, which has substantial implications for the theory of falling chorus generation.

  1. Distance corrections for single- and dual-color lasers by ray tracing. [for earth crustal deformation and strain measurement

    NASA Technical Reports Server (NTRS)

    Berg, E.; Carter, J. A.

    1980-01-01

    The physical arc length difference between the red and blue beam of a dual-color laser generates an error term in determining Delta-n as well as n (the refractive index) and D (the line length). Numerical ray trace examples and theoretical approximations show that the resulting relative error Delta-D/D increases as D-squared. Error reduction by a factor of nearly 10 is possible by using the pressure, temperature, and humidity of both endpoints to calculate n. The present study results from a desire to improve the precision of monitoring the local and regional position of the Lunar Laser Ranging Observatory atop Haleakala, Maui, Hawaii; the monitoring of the earth's crustal deformation and strain is a primary concern of the study.

  2. Use of Rayleigh imaging and ray tracing to correct for beam-steering effects in turbulent flames.

    PubMed

    Kaiser, Sebastian A; Frank, Jonathan H; Long, Marshall B

    2005-11-01

    Laser Rayleigh imaging has been applied in a number of flow and flame studies to measure concentration or temperature distributions. Rayleigh cross sections are dependent on the index of refraction of the scattering medium. The same index of refraction changes that provide contrast in Rayleigh images can also deflect the illuminating laser sheet. By applying a ray-tracing algorithm to the detected image, it is possible to correct for some of these beam-steering effects and thereby improve the accuracy of the measured field. Additionally, the quantification of the degree of beam steering through the flow provides information on the degradation of spatial resolution in the measurement. Application of the technique in a well-studied laboratory flame is presented, along with analysis of the effects of image noise and spatial resolution on the effectiveness of the algorithm. PMID:16270544

  3. Three-dimensional ray tracing through curvilinear interfaces with application to laser Doppler anemometry in a blood analogue fluid.

    PubMed

    Nugent, Allen H; Bertram, Christopher D

    2010-02-01

    Prediction of the effects of refractive index (RI) mismatch on laser Doppler anemometer (LDA) measurements within a curvilinear cavity (an artificial ventricle) was achieved by developing a general technique for modelling the paths of the convergent beams of the LDA system using 3D vector geometry. Validated by ray tracing through CAD drawings, the predicted maximum tolerance in RI between the solid model and the working fluid was +/- 0.0005, equivalent to focusing errors commensurate with the geometric and alignment uncertainties associated with the flow model and the LDA arrangement. This technique supports predictions of the effects of refraction within a complex geometry. Where the RI mismatch is unavoidable but known, it is possible not only to calculate the true position of the measuring volume (using the probe location and model geometry), but also to estimate degradation in signal quality arising from differential displacement and refraction of the laser beams. PMID:19669821

  4. Trace element analyses of spheres from the melt zone of the Greenland ice cap using synchrotron X ray fluorescence

    NASA Technical Reports Server (NTRS)

    Chevallier, P.; Wang, J.; Jehanno, C.; Maurette, M.; Sutton, S. R.

    1986-01-01

    Synchrotron X-ray fluorescence spectra of unpolished iron and chondritic spheres extracted from sediments collected on the melt zone of the Greenland ice cap allow the analysis of Ni, Cu, Zn, Ga, Ge, Pb, and Se with minimum detection limits on the order of several parts per million. All detected elements are depleted relative to chondritic abundance with the exception of Pb, which shows enrichments up to a factor of 500. An apparent anticorrelation between the Ni-content and trace element concentration was observed in both types of spherules. The fractionation patterns of the iron and chondritic spheres are not complementary and consequently the two iron spheres examined in this study are unlikely to result from ejection of globules of Fe/Ni from parent chondritic micrometeoroids.

  5. Retrieving particle size and density from extinction measurement in dusty plasma, Monte Carlo inversion and Ray-tracing comparison

    NASA Astrophysics Data System (ADS)

    Dap, S.; Lacroix, D.; Hugon, R.; Bougdira, J.

    2013-10-01

    In this study, we present a Monte Carlo inversion procedure dedicated to the determination of particle size and density from extinction measurements. In order to check the validity of the method, a ray tracing code able to calculate the exact extinction coefficient for a given particle size distribution was developed. The inversion method was then applied to this numerically obtained results in order to retrieve the initial particle size distribution. We found that the method provides good estimations of the particle sizes and density. Finally, the inversion procedure was applied to experimental data obtained with visible and infra-red spectroscopy. A comparison between the calculated particle sizes and the ones measured from SEM micrography shows good agreements.

  6. Trace element analyses of spheres from the melt zone of the Greenland Ice Cap using synchrotron X ray fluorescence

    NASA Astrophysics Data System (ADS)

    Chevallier, P.; Jehanno, C.; Maurette, M.; Sutton, S. R.; Wang, J.

    Synchrotron X ray fluorescence spectra of unpolished iron and chondritic spheres extracted from sediments collected on the melt zone of the Greenland ice cap allow the analysis of Ni, Cu, Zn, Ga, Ge, Pb, and Se with minimum detection limits on the order of several parts per million. All detected elements are depleted relative to chondritic abundance with the exception of Pb, which shows enrichments up to a factor of 500. An apparent anticorrelation between the Ni-content and trace element concentration was observed in both types of spherules. The fractionation patterns of the iron and chondritic spheres are not complementary and consequently the two iron spheres examined in this study are unlikely to result from the ejection of globules of Fe/Ni from parent chondritic micrometeoroids.

  7. Trace element analyses of spheres from the melt zone of the Greenland ice cap using synchrotron X ray fluorescence

    NASA Astrophysics Data System (ADS)

    Chevallier, P.; Jehanno, C.; Maurette, M.; Sutton, S. R.; Wang, J.

    1987-09-01

    Synchrotron X ray fluorescence spectra of unpolished iron and chondritic spheres extracted from sediments collected on the melt zone of the Greenland ice cap allow the analysis of Ni, Cu, Zn, Ga, Ge, Pb, and Se with minimum detection limits on the order of several parts per million. All detected elements are depleted relative to chondritic abundance with the exception of Pb, which shows enrichments up to a factor of 500. An apparent anticorrelation between the Ni-content and trace element concentration was observed in both types of spherules. The fractionation patterns of the iron and chondrite spheres are not complementary and consequently the two iron spheres examined in this study are unlikely to result from the ejection of globules of Fe/Ni from parent chondritic micrometeroids. © American Geophyscial Union 1987

  8. Ray-tracing study on the post-scanner variable beam expansion optics in a two-photon microscopy system

    NASA Astrophysics Data System (ADS)

    Kim, Do-Hyun; Welle, Cristin; Krauthamer, Victor

    2012-03-01

    Due to the low signal levels typical of two-photon microscopy (TPM) in biological samples, optical design optimization is critical. One of the most important factors is overfilling of the back aperture of the objective lens. A variable beam expander is commonly placed before the scanning mirrors to achieve this goal, however, this may cause degradation of image quality due to increased dispersion. Additionally, scanning mirror size restricts the degree of expansion, which often prevents the overfilling of objective lens back aperture. We investigated the implementation of variable beam expansion optics after the scanning mirrors. Ray-tracing analyses confirmed that the post-scanner beam expansion has two key advantages over the conventional pre-scanner beam expansion approach: decreasing the number of optical elements reduces pulse dispersion and reducing the size of the scanning mirror enables faster scanning. Resolution and aberration of a TPM with post-scanner beam expansion optics were analysed.

  9. Erratum: Studying the precision of ray tracing techniques with Szekeres models [Phys. Rev. D 92, 023532 (2015)

    NASA Astrophysics Data System (ADS)

    Koksbang, S. M.; Hannestad, S.

    2015-09-01

    This erratum serves to give corrections of two errors made in Koksbang and Hannestad [Phys. Rev. D, 92, 023532 (2015)]. One error consists of having used the expression for the Doppler convergence for a flat background to study the convergence on curved backgrounds. The other error which was made, is a typo in the numerical code used to study the convergence in onion models with curved backgrounds. After correcting this typo, the results of Sec. VI A in Koksbang and Hannestad [Phys. Rev. D, 92, 023532 (2015)] were recomputed. Contrary to the original results, the new results show that the ray-tracing scheme studied in Koksbang and Hannestad [Phys. Rev. D, 92, 023532 (2015)] can reproduce the exact results in LTB onion models very well. The corrections and new results are described more elaborately below.

  10. Seasonal variation in trace and minor elements in Brazilian honey by total reflection X-ray fluorescence.

    PubMed

    de Oliveira Resende Ribeiro, Roberta; Mársico, Eliane Teixeira; da Silva Carneiro, Carla; Simoes, Julia Siqueira; da Silva Ferreira, Micheli; de Jesus, Edgar Francisco Oliveira; Almeida, Eduardo; Junior, Carlos Adam Conte

    2015-03-01

    Honey is used as an alternative medicine and is a constituent of a healthy diet worldwide. Its composition is associated with botanical origin and, to some extent, geographical origin because soil and climate characteristics determine the melliferous flora. Also, the elements content in honey samples could give an indication of environmental pollution or geographical origin. The main purpose of this study was to evaluate seasonal patterns of essential elements of Brazilian honey. Honey was collected during spring, summer, autumn, and winter for 2 years to quantify K, Ca, Ti, Cr, Mn, Fe, Ni, Cu, Zn, Se, Br, and Sr using total reflection X-ray fluorescence spectroscopy (TXRF). Our results indicate no seasonal differences in concentration of Cr, Ni, Se, and Ti, although there were significant seasonal patterns in the composition of essential elements in honey, with higher concentrations of minor and trace elements, especially K and Ca of samples collected in spring and summer. PMID:25663399

  11. Role of x-ray-induced transcripts in adaptive responses following x-rays

    SciTech Connect

    Boothman, D.A.

    1992-01-01

    Potentially lethal damage repair (PLDR) and sublethal damage repair, may be the same manifestations of a series of common enzymatic steps. PLDR, has two distinct phases based upon DNA lesion repair and survival recovery studies. The first phase of PLDR occurs very quickly (t{sub {1/2}}:2--20 mins) to increase the survival of X-irradiated cells by mending the vast array of DNA lesions created by ionizing radiation. The second slower phase of PLDR proceeds much later (i.e., >1--2 hrs) following X-irradiation, during which the remaining double-stranded DNA breaks are completely repaired. This second phase of repair closely corresponds to the restructuring of gross chromosomal damage, and can be partially blocked in some human cells by inhibiting protein synthesis. This slower phase of PLDR correlated with a rapid decline in X-ray-induced transformation of normal cells. The fast component of PLDR may be due to constitutively synthesized DNA ligases, topoisomerases, or polymerases, which act immediately to repair damaged, DNA. In contrast, the slow phase of PLDR in human cells may require the induction of specific genes and gene product's involved in the repair of potentially lethal or carcinogenic DNA lesions. Induced gene products (i.e., proteins) specifically synthesized in response to physiological doses of ionizing radiation in radioresistant human melanoma (U1-Mel) cells, and in a variety of other human normal and cancer-prone cells, were identified using two-dimensional gel electrophoresis. We identified and partially characterized ten proteins synthesized by U1-Mel cells. The synthesis of eight of these proteins were specifically induced by ionizing radiation and two proteins were repressed Neither heat shock, UV-irradiation, nor bifunctional alkylating agent treatments resulted in the induction of these proteins. The expression of one protein, XIP269, correlated very well with PLDR capacity.

  12. Incorporation of Trace Elements in Ancient and Modern Human Bone: An X-Ray Absorption Spectroscopy Study

    NASA Astrophysics Data System (ADS)

    Pingitore, N. E.; Cruz-Jimenez, G.; Price, T. D.

    2001-12-01

    X-ray absorption spectroscopy (XAS) affords the opportunity to probe the atomic environment of trace elements in human bone. We are using XAS to investigate the mode(s) of incorporation of Sr, Zn, Pb, and Ba in both modern and ancient (and thus possibly altered) human and animal bone. Because burial and diagenesis may add trace elements to bone, we performed XAS analysis on samples of pristine contemporary and ancient, buried human and animal bone. We assume that deposition of these elements during burial occurs by processes distinct from those in vivo, and this will be reflected in their atomic environments. Archaeologists measure strontium in human and animal bone as a guide to diet. Carnivores show lower Sr/Ca ratios than their herbivore prey due to discrimination against Sr relative to Ca up the food chain. In an initial sample suite no difference was observed between modern and buried bone. Analysis of additional buried samples, using a more sensitive detector, revealed significant differences in the distance to the second and third neighbors of the Sr in some of the buried samples. Distances to the first neighbor, oxygen, were similar in all samples. Zinc is also used in paleo-diet studies. Initial x-ray absorption spectroscopy of a limited suite of bones did not reveal any differences between modern and buried samples. This may reflect the limited number of samples examined or the low levels of Zn in typical aqueous solutions in soils. Signals from barium and lead were too low to record useful XAS spectra. Additional samples will be studied for Zn, Ba, and Pb. We conducted our XAS experiments on beam lines 4-1 and 4-3 at the Stanford Synchrotron Radiation Laboratory. Data were collected in the fluorescence mode, using a Lytle detector and appropriate filter, and a solid state, 13-element Ge-detector.

  13. Integrated ray tracing simulation of annual variation of spectral bio-signatures from cloud free 3D optical Earth model

    NASA Astrophysics Data System (ADS)

    Ryu, Dongok; Kim, Sug-Whan; Kim, Dae Wook; Lee, Jae-Min; Lee, Hanshin; Park, Won Hyun; Seong, Sehyun; Ham, Sun-Jeong

    2010-09-01

    Understanding the Earth spectral bio-signatures provides an important reference datum for accurate de-convolution of collapsed spectral signals from potential earth-like planets of other star systems. This study presents a new ray tracing computation method including an improved 3D optical earth model constructed with the coastal line and vegetation distribution data from the Global Ecological Zone (GEZ) map. Using non-Lambertian bidirectional scattering distribution function (BSDF) models, the input earth surface model is characterized with three different scattering properties and their annual variations depending on monthly changes in vegetation distribution, sea ice coverage and illumination angle. The input atmosphere model consists of one layer with Rayleigh scattering model from the sea level to 100 km in altitude and its radiative transfer characteristics is computed for four seasons using the SMART codes. The ocean scattering model is a combination of sun-glint scattering and Lambertian scattering models. The land surface scattering is defined with the semi empirical parametric kernel method used for MODIS and POLDER missions. These three component models were integrated into the final Earth model that was then incorporated into the in-house built integrated ray tracing (IRT) model capable of computing both spectral imaging and radiative transfer performance of a hypothetical space instrument as it observes the Earth from its designated orbit. The IRT model simulation inputs include variation in earth orientation, illuminated phases, and seasonal sea ice and vegetation distribution. The trial simulation runs result in the annual variations in phase dependent disk averaged spectra (DAS) and its associated bio-signatures such as NDVI. The full computational details are presented together with the resulting annual variation in DAS and its associated bio-signatures.

  14. Laser ray tracing and power deposition on an unstructured three-dimensional grid

    PubMed

    Kaiser

    2000-01-01

    A scheme is presented for laser beam evolution and power deposition on three-dimensional unstructured grids composed of hexahedra, prisms, pyramids, and tetrahedra. The geometrical-optics approximation to the electromagnetic wave equation is used to follow propagation of a collection of discrete rays used to represent the beam(s). Ray trajectory equations are integrated using a method that is second order in time, exact for a constant electron-density gradient, and capable of dealing with density discontinuities that arise in certain hydrodynamics formulations. Power deposition by inverse-bremsstrahlung is modeled with a scheme based on Gaussian quadrature to accommodate a deposition rate whose spatial variation is highly nonuniform. Comparisons with analytic results are given for a density ramp in three dimensions, and a "quadratic-well" density trough in two dimensions. PMID:11046339

  15. Application of the Total Reflection X-ray Fluorescence technique to trace elements determination in tobacco

    NASA Astrophysics Data System (ADS)

    Martinez, T.; Lartigue, J.; Zarazua, G.; Avila-Perez, P.; Navarrete, M.; Tejeda, S.

    2008-12-01

    Many studies have identified an important number of toxic elements along with organic carcinogen molecules and radioactive isotopes in tobacco. In this work we have analyzed by Total Reflection X-Ray Fluorescence 9 brands of cigarettes being manufactured and distributed in the Mexican market. Two National Institute of Standards and Technology standards and a blank were equally treated at the same time. Results show the presence of some toxic elements such as Pb and Ni. These results are compared with available data for some foreign brands, while their implications for health are discussed. It can be confirmed that the Total Reflection X-Ray Fluorescence method provides precise (reproducible) and accuracy (trueness) data for 15 elements concentration in tobacco samples.

  16. Hard X-ray nanofocusing using adaptive focusing optics based on piezoelectric deformable mirrors

    SciTech Connect

    Goto, Takumi; Nakamori, Hiroki; Sano, Yasuhisa; Matsuyama, Satoshi; Kimura, Takashi; Kohmura, Yoshiki; Tamasaku, Kenji; Yabashi, Makina; Ishikawa, Tetsuya

    2015-04-15

    An adaptive Kirkpatrick–Baez mirror focusing optics based on piezoelectric deformable mirrors was constructed at SPring-8 and its focusing performance characteristics were demonstrated. By adjusting the voltages applied to the deformable mirrors, the shape errors (compared to a target elliptical shape) were finely corrected on the basis of the mirror shape determined using the pencil-beam method, which is a type of at-wavelength figure metrology in the X-ray region. The mirror shapes were controlled with a peak-to-valley height accuracy of 2.5 nm. A focused beam with an intensity profile having a full width at half maximum of 110 × 65 nm (V × H) was achieved at an X-ray energy of 10 keV.

  17. Hard X-ray nanofocusing using adaptive focusing optics based on piezoelectric deformable mirrors

    NASA Astrophysics Data System (ADS)

    Goto, Takumi; Nakamori, Hiroki; Kimura, Takashi; Sano, Yasuhisa; Kohmura, Yoshiki; Tamasaku, Kenji; Yabashi, Makina; Ishikawa, Tetsuya; Yamauchi, Kazuto; Matsuyama, Satoshi

    2015-04-01

    An adaptive Kirkpatrick-Baez mirror focusing optics based on piezoelectric deformable mirrors was constructed at SPring-8 and its focusing performance characteristics were demonstrated. By adjusting the voltages applied to the deformable mirrors, the shape errors (compared to a target elliptical shape) were finely corrected on the basis of the mirror shape determined using the pencil-beam method, which is a type of at-wavelength figure metrology in the X-ray region. The mirror shapes were controlled with a peak-to-valley height accuracy of 2.5 nm. A focused beam with an intensity profile having a full width at half maximum of 110 × 65 nm (V × H) was achieved at an X-ray energy of 10 keV.

  18. Vertical scanning long trace profiler: A tool for metrology of X-ray mirrors

    SciTech Connect

    Li, Haizhang; Takacs, P.Z.; Oversluizen, T.

    1997-07-01

    This paper describes the development of a prototype instrument of the Vertical Scanning Long Trace Profiler (VSLTP) under a SBIR Phase II grant from NASA. The instrument is capable of scanning shell mirrors with a diameter as small as 100mm for a travel distance of 700mm in vertical configuration. Main components of the optical system are described. It has a beam separation set, a beam splitting set, a Fourier transform lens system, a penta prism pair, a Risley prism pair and a cylinder lens. The main hardware and software for implementation of the prototype instrument are also presented. They include the major mechanical structure, 9-axis motion control system and the data acquisition and analysis software. The design of the optical and mechanical systems makes the VSLTP very tolerable to the deformation of the slide deformation, laser pattern shift and fluctuation due to temperature change. Results obtained from the Phase I show that VSLTP instrument is capable of a measurement accuracy of 50 nm for the height and 1 microradian for the slope.

  19. Synchrotron radiation X-ray fluorescence analysis of trace elements in Nerium oleander for pollution monitoring

    NASA Astrophysics Data System (ADS)

    de Jesus, E. F. O.; Simabuco, S. M.; dos Anjos, M. J.; Lopes, R. T.

    2000-07-01

    This works describes the use of synchrotron radiation fluorescence analysis as a technique for monitoring trace elements in bio-indicators for environmental pollution control. The analyses were performed on leaves of Nerium oleander collected in streets with different levels of traffic flow in Rio de Janeiro, Brazil, with one sample from a rural zone. The leaves were collected from adult trees in December and April. The measurement was made with a white beam of synchrotron radiation calibrated with thin samples from MicroMatter. The results indicate that some metals such as Ti, V, Fe and Zn have major content in samples that were collected in places with a high traffic flow, even in the leaves that have been washed. The levels of Mn, Co, Cu and Ni did not show significant differences between the samples. The Pb level also did not vary significantly. This was expected because in Brazil gasoline without Pb has been used for many years. The results seem to indicate that the leaves from Nerium oleander absorb metals from the atmosphere and may be used as an environmental indicator.

  20. Electroadsorption-assisted direct determination of trace arsenic without interference using transmission X-ray fluorescence spectroscopy.

    PubMed

    Jiang, Tian-Jia; Guo, Zheng; Liu, Jin-Huai; Huang, Xing-Jiu

    2015-08-18

    An analytical technique based on electroadsorption and transmission X-ray fluorescence (XRF) for the quantitative determination of arsenic in aqueous solution with ppb-level limits of detection (LOD) is proposed. The approach uses electroadsorption to enhance the sensitivity and LOD of the arsenic XRF response. Amine-functionalized carbonaceous microspheres (NH2-CMSs) are found to be the ideal materials for both the quantitative adsorption of arsenic and XRF analysis due to the basic amine sites on the surface and their noninterference in the XRF spectrum. In electroadsorptive X-ray fluorescence (EA-XRF), arsenic is preconcentrated by a conventional three-electrode system with a positive electricity field around the adsorbents. Then, the quantification of arsenic on the adsorbents is achieved using XRF. The electroadsorption preconcentration can realize the fast transfer of arsenic from the solution to the adsorbents and improve the LOD of conventional XRF compared with directly determining arsenic solution by XRF alone. The sensitivity of 0.09 cnt ppb(-1) is obtained without the interferences from coexisted metal ions in the determination of arsenic, and the LOD is found to be 7 ppb, which is lower than the arsenic guideline value of 10 ppb given by the World Health Organization (WHO). These results demonstrated that XRF coupled with electroadsorption was able to determine trace arsenic in real water sample. PMID:26211572

  1. X-ray fluorescence study of the concentration of selected trace and minor elements in human brain tumours

    NASA Astrophysics Data System (ADS)

    Wandzilak, Aleksandra; Czyzycki, Mateusz; Radwanska, Edyta; Adamek, Dariusz; Geraki, Kalotina; Lankosz, Marek

    2015-12-01

    Neoplastic and healthy brain tissues were analysed to discern the changes in the spatial distribution and overall concentration of elements using micro X-ray fluorescence spectroscopy. High-resolution distribution maps of minor and trace elements such as P, S, Cl, K, Ca, Fe, Cu and Zn made it possible to distinguish between homogeneous cancerous tissue and areas where some structures could be identified, such as blood vessels and calcifications. Concentrations of the elements in the selected homogeneous areas of brain tissue were compared between tumours with various malignancy grades and with the controls. The study showed a decrease in the average concentration of Fe, P, S and Ca in tissues with high grades of malignancy as compared to the control group, whereas the concentration of Zn in these tissues was increased. The changes in the concentration were found to be correlated with the tumour malignancy grade. The efficacy of micro X-ray fluorescence spectroscopy to distinguish between various types of cancer based on the concentrations of studied elements was confirmed by multivariate discriminant analysis. Our analysis showed that the most important elements for tissue classification are Cu, K, Fe, Ca, and Zn. This method made it possible to correctly classify histopathological types in 99.93% of the cases used to build the model and in as much as 99.16% of new cases.

  2. Three-dimensional trace element analysis by confocal X-ray microfluorescence imaging.

    PubMed

    Vincze, Laszlo; Vekemans, Bart; Brenker, Frank E; Falkenberg, Gerald; Rickers, Karen; Somogyi, Andrea; Kersten, Michael; Adams, Freddy

    2004-11-15

    A three-dimensional (3D) variant of scanning micro X-ray fluorescence (XRF) is described and evaluated at the ID18F instrument of the European Synchrotron Radiation Facility (ESRF). The method is based on confocal excitation/detection using a polycapillary half-lens in front of the energy-dispersive detector. The experimental arrangement represents a significant generalization of regular two-dimensional (2D) scanning micro-XRF and employs a detector half-lens whose focus coincides with that of the focused incoming beam. The detection volume defined by the intersection of the exciting beam and the energy-dependent acceptance of the polycapillary optics is 100-350 mum(3). Minimum detection limits are sub-ppm, and sensitivities are comparable with regular scanning XRF. Next to the reduction of in-sample single/multiple scattering, the setup provides the possibility of sample depth scans with an energy-dependent resolution of 10-35 mum in the energy range of 3-23 keV and the possibility of performing 3D-XRF analysis by simple XYZ linear scanning. This provides a suitable alternative to X-ray fluorescence tomography. The method is illustrated with results of the analysis of solid inclusions in diamond and fluid inclusions in quartz. PMID:15538804

  3. Trace the polymerization induced by gamma-ray irradiated silica particles

    NASA Astrophysics Data System (ADS)

    Lee, Hoik; Ryu, Jungju; Kim, Myungwoong; Im, Seung Soon; Kim, Ick Soo; Sohn, Daewon

    2016-08-01

    A γ-ray irradiation to inorganic particles is a promising technique for preparation of organic/inorganic composites as it offers a number of advantages such as an additive-free polymerizations conducted under mild conditions, avoiding undesired damage to organic components in the composites. Herein, we demonstrated a step-wise formation mechanism of organic/inorganic nanocomposite hydrogel in detail. The γ-ray irradiation to silica particles dispersed in water generates peroxide groups on their surface, enabling surface-initiated polymerization of acrylic acid from the inorganic material. As a result, poly(acrylic acid) (PAA) covers the silica particles in the form of a core-shell at the initial stage. Then, PAA-coated silica particles associate with each other by combination of radicals at the end of chains on different particles, leading to micro-gel domains. Finally, the micro-gels are further associated with each other to form a 3D network structure. We investigated this mechanism using dynamic light scattering (DLS) and transmission electron microscopy (TEM). Our result strongly suggests that controlling reaction time is critical to achieve specific and desirable organic/inorganic nanocomposite structure among core-shell particles, micro-gels and 3D network bulk hydrogel.

  4. A quasi-optical ray tracing code for EC absorption and current drive

    NASA Astrophysics Data System (ADS)

    Farina, Daniela

    2005-10-01

    A new code GRAY has been developed for the quasi-optical (QO) propagation of a Gaussian beam of EC waves and the relevant absorbed power and driven current in a generic tokamak equilibrium [D. Farina, IFP-CNR Int. Rep. 2005, FP 05/1]. In the framework of the complex eikonal approach [E. Mazzucato, Phys. Fluids, 1, 1855 (1989)], the beam propagation is described by a set of mutually interacting rays. Several theoretical and numerical issues have been addressed and solved, mainly concerning the accurate solution of the complex dispersion relation. A fast numerical algorithm for the solution of the imaginary part of the QO dispersion relation has been implemented. Along each ray, EC wave absorption is computed solving either the weakly or the fully relativistic dispersion relation for EC waves (up to any order in Larmor radius expansion), and EC current drive by means of a neoclassical response function for the current [D. Farina, IFP-CNR Int. Rep. 2003, FP 03/5]. The code has been benchmarked against other existing codes, and used for calculations of EC driven current in ITER plasma.

  5. Adaptation.

    PubMed

    Broom, Donald M

    2006-01-01

    The term adaptation is used in biology in three different ways. It may refer to changes which occur at the cell and organ level, or at the individual level, or at the level of gene action and evolutionary processes. Adaptation by cells, especially nerve cells helps in: communication within the body, the distinguishing of stimuli, the avoidance of overload and the conservation of energy. The time course and complexity of these mechanisms varies. Adaptive characters of organisms, including adaptive behaviours, increase fitness so this adaptation is evolutionary. The major part of this paper concerns adaptation by individuals and its relationships to welfare. In complex animals, feed forward control is widely used. Individuals predict problems and adapt by acting before the environmental effect is substantial. Much of adaptation involves brain control and animals have a set of needs, located in the brain and acting largely via motivational mechanisms, to regulate life. Needs may be for resources but are also for actions and stimuli which are part of the mechanism which has evolved to obtain the resources. Hence pigs do not just need food but need to be able to carry out actions like rooting in earth or manipulating materials which are part of foraging behaviour. The welfare of an individual is its state as regards its attempts to cope with its environment. This state includes various adaptive mechanisms including feelings and those which cope with disease. The part of welfare which is concerned with coping with pathology is health. Disease, which implies some significant effect of pathology, always results in poor welfare. Welfare varies over a range from very good, when adaptation is effective and there are feelings of pleasure or contentment, to very poor. A key point concerning the concept of individual adaptation in relation to welfare is that welfare may be good or poor while adaptation is occurring. Some adaptation is very easy and energetically cheap and

  6. DIBENZYLAMMONIUM AND SODIUM DIBENZYLDITHIOCARBAMATES AS PRECIPITANTS FOR PRECONCENTRATION OF TRACE ELEMENTS IN WATER FOR ANALYSIS BY ENERGY DISPERSIVE X-RAY FLUORESCENCE

    EPA Science Inventory

    Precipitation with combined dibenzylammonium dibenzyldithiocarbamate and sodium dibenzyldithiocarbamate at pH 5.0 can be used to separate 22 trace elements from water. Membrane filtration on the precipitate yielded a thin sample, suitable for analysis by energy dispersive X-ray f...

  7. Adaptive Mesh Refinement Cosmological Simulations of Cosmic Rays in Galaxy Clusters

    NASA Astrophysics Data System (ADS)

    Skillman, Samuel William

    2013-12-01

    Galaxy clusters are unique astrophysical laboratories that contain many thermal and non-thermal phenomena. In particular, they are hosts to cosmic shocks, which propagate through the intracluster medium as a by-product of structure formation. It is believed that at these shock fronts, magnetic field inhomogeneities in a compressing flow may lead to the acceleration of cosmic ray electrons and ions. These relativistic particles decay and radiate through a variety of mechanisms, and have observational signatures in radio, hard X-ray, and Gamma-ray wavelengths. We begin this dissertation by developing a method to find shocks in cosmological adaptive mesh refinement simulations of structure formation. After describing the evolution of shock properties through cosmic time, we make estimates for the amount of kinetic energy processed and the total number of cosmic ray protons that could be accelerated at these shocks. We then use this method of shock finding and a model for the acceleration of and radio synchrotron emission from cosmic ray electrons to estimate the radio emission properties in large scale structures. By examining the time-evolution of the radio emission with respect to the X-ray emission during a galaxy cluster merger, we find that the relative timing of the enhancements in each are important consequences of the shock dynamics. By calculating the radio emission expected from a given mass galaxy cluster, we make estimates for future large-area radio surveys. Next, we use a state-of-the-art magnetohydrodynamic simulation to follow the electron acceleration in a massive merging galaxy cluster. We use the magnetic field information to calculate not only the total radio emission, but also create radio polarization maps that are compared to recent observations. We find that we can naturally reproduce Mpc-scale radio emission that resemble many of the known double radio relic systems. Finally, motivated by our previous studies, we develop and introduce a

  8. Aberration analysis of the putative projector for Lorenzo Lotto's Husband and wife: image analysis through computer ray-tracing

    NASA Astrophysics Data System (ADS)

    Robinson, Dirk; Stork, David G.

    2008-02-01

    A recent theory claims that the late-Italian Renaissance painter Lorenzo Lotto secretly built a concave-mirror projector to project an image of a carpet onto his canvas and trace it during the execution of Husband and wife (c. 1543). Key evidence adduced to support this claim includes "perspective anomalies" and changes in "magnification" that the theory's proponents ascribe to Lotto refocusing his projector to overcome its limitations in depth of field. We find, though, that there are important geometrical constraints upon such a putative optical projector not incorporated into the proponents' analyses, and that when properly included, the argument for the use of optics loses its force. We used Zemax optical design software to create a simple model of Lotto's studio and putative projector, and incorporated the optical properties proponents inferred from geometrical properties of the depicted carpet. Our central contribution derives from including the 116-cm-wide canvas screen; we found that this screen forces the incident light to strike the concave mirror at large angles (>= 15°) and that this, in turn, means that the projected image would reveal severe off-axis aberrations, particularly astigmatism. Such aberrations are roughly as severe as the defocus blur claimed to have led Lotto to refocus the projector. In short, we find that the projected images would not have gone in and out of focus in the way claimed by proponents, a result that undercuts their claim that Lotto used a projector for this painting. We speculate on the value of further uses of sophisticated ray-tracing analyses in the study of fine arts.

  9. Cold plasma ashing improves the trace element detection of single Daphnia specimens by total reflection X-ray fluorescence spectrometry

    NASA Astrophysics Data System (ADS)

    Woelfl, Stefan; Mages, Margarete; Encina, Francisco

    2003-12-01

    The recently developed dry method for the element determination of single freshwater microcrustacean specimens ( Daphnia) using total reflection X-ray fluorescence (TXRF) spectrometry showed that inhomogeneities of the biological material on the glass carriers resulted in some cases in high background and hampered the detection of certain trace elements (e.g. Cr, Ni). The aim of this study was to test how inhomogeneities of the biological material can be reduced using cold plasma ashing (CPA) techniques. For that, single specimens of the microcrustacean Daphnia pulex prepared according to the dry method were measured by TXRF before and after CPA. To determine the efficiency of the removal of organic matrix, the background and signal-to-background relationship of 28 samples were analyzed. The results showed (1) a highly significant reduction of the background by CPA fluctuating between 26 and 46% (all elements) and (2) a significant increase of the signal-to-background relationship by the factor 1.5-2.5 (all elements) and a much better detection of Cr, Pb, As and Se. The element concentrations (with exception of Cr, Ni and Pb) after ashing were in the same range or slightly higher than that before ashing. No significant differences between the two treatments were observed for Mn, As, Pb, Se (November), Sr (November), Cr (March) and Pb (March). The element concentration of P, K, Ca, Cu, Zn, Cr (November), Fe and Rb were significantly higher after ashing. In general, they increased by 1.5-13.6% and were highest for Rb (March) and P (November). In contrast, the element concentration of Ni and Cr (only March) decreased significantly after ashing (Ni: 91.6-92.1%, Cr: 91.3%). We recommend the use of CPA for biological material in the microgram-range as a routine method for TXRF analysis, especially when trace elements in minute concentrations are of interest.

  10. Timing in Trace Conditioning of the Nictitating Membrane Response of the Rabbit ("Oryctolagus Cuniculus"): Scalar, Nonscalar, and Adaptive Features

    ERIC Educational Resources Information Center

    Kehoe, E. James; Ludvig, Elliot A.; Sutton, Richard S.

    2010-01-01

    Using interstimulus intervals (ISIs) of 125, 250, and 500 msec in trace conditioning of the rabbit nictitating membrane response, the offset times and durations of conditioned responses (CRs) were collected along with onset and peak latencies. All measures were proportional to the ISI, but only onset and peak latencies conformed to the criterion…

  11. Shape estimation of transparent objects by using inverse polarization ray tracing.

    PubMed

    Miyazaki, Daisuke; Ikeuchi, Katsushi

    2007-11-01

    Few methods have been proposed to measure three-dimensional shapes of transparent objects such as those made of glass and acrylic. In this paper, we propose a novel method for estimating the surface shapes of transparent objects by analyzing the polarization state of the light. Existing methods do not fully consider the reflection, refraction, and transmission of the light occurring inside a transparent object. We employ a polarization raytracing method to compute both the path of the light and its polarization state. Polarization raytracing is a combination of conventional raytracing, which calculates the trajectory of light rays, and Mueller calculus, which calculates the polarization state of the light. First, we set an initial value of the shape of the transparent object. Then, by changing the shape, the method minimizes the difference between the input polarization data and the rendered polarization data calculated by polarization raytracing. Finally, after the iterative computation is converged, the shape of the object is obtained. We also evaluate the method by measuring some real transparent objects. PMID:17848781

  12. An adapted modulation transfer function for x-ray backscatter radiography by selective detection

    NASA Astrophysics Data System (ADS)

    Sabri, Nissia; Dugan, Edward T.; Jacobs, Alan M.; Shedlock, Daniel

    2007-09-01

    The Modulation Transfer Function (MTF) is a quantitative function based on frequency resolution that characterizes imaging system performance. In this study, a new MTF methodology is investigated for application to Radiography by Selective Detection (RSD), an enhanced single-side x-ray Compton backscatter imaging (CBI) technique which detects selected scatter components. The RSD imaging modality is a unique type of real-time radiography that uses a set of fin and sleeve collimators to preferentially select different components of the x-ray backscattered field. Radiography by selective detection has performed successfully in different non-destructive evaluation (NDE) applications. A customized RSD imaging system was built at the University of Florida for inspection of the space shuttle external tank spray-on foam insulation (SOFI). The x-ray backscatter RSD imaging system has been successfully used for crack and corrosion detection in a variety of materials. The conventional transmission x-ray image quality characterization tools do not apply for RSD because of the different physical process involved. Thus, the main objective of this project is to provide an adapted tool for dynamic evaluation of RSD system image quality. For this purpose, an analytical model of the RSD imaging system response is developed and supported. Two approaches are taken for the MTF calculations: one using the Fourier Transform of a line spread function and the other one using a sine function pattern. Calibration and test targets are then designed according to this proposed model. A customized Matlab code using image contrast and digital curve recognition is developed to support the experimental data and provide the Modulation Transfer Functions for RSD.

  13. Development of an Adaptive Optical System for Sub-10-nm Focusing of Synchrotron Radiation Hard X-rays

    SciTech Connect

    Mimura, H.; Kimura, T.; Matsuyama, S.; Yokoyama, H.; Yumoto, H.

    2011-09-09

    In the hard x-ray region, to obtain the theoretical resolution or diffraction-limited focusing size in an imaging optical system, both ultraprecise optics and highly accurate alignment are necessary. An adaptive optical system is used for the compensation of aberrations in various optical systems, such as optical microscopes and space telescopes. In situ wavefront control of hard x-rays is also effective for realizing ideal performance. The aim of this paper is to develop an adaptive optical system for sub-10-nm hard x-ray focusing. The adaptive optical system performs the wavefront measurement using a phase retrieval algorithm and wavefront control using grazing-incidence deformable mirrors. Several results of experiments using the developed system are reported.

  14. Ray-tracing method to analyze and quantify the light enhancement around subsurface defects in transparent materials

    NASA Astrophysics Data System (ADS)

    Wu, Rong; Zhao, Dongfeng; Zhang, Lei; Shao, Ping; Hua, Neng; Lin, Zunqi

    2014-11-01

    Laser-induced damage (LID) to optical glass has become a growing problem in high-power laser systems. It is well known that the main reason of glass being damaged is due to defects and impurities in the material. Damage caused by subsurface defects (SSDs) is especially common in actual system running. Accordingly, in the presence of SSDs, a simple and alternative calculation method is developed to evaluate the enhancement of light field around the incident and exit surface. This ray tracing approach, based on the classical optics theory, is very direct and clear to show the optical phenomena of light intensity enhancement. Some basic SSD shapes have been studied and investigated here, which reveals the importance and boundary condition of controlling the size and density of SSDs in grinding and polishing process. Finally, to achieve optimal breadth depth ratio, the least etching amounts by hydrofluoric (HF) acid is investigated. The theoretical analysis and simulation results provide an appropriate range of removal amounts, which is very important in the HF etching process.

  15. Mapping of endoscopic images to object surfaces via ray-traced texture mapping for image guidance in neurosurgery

    NASA Astrophysics Data System (ADS)

    Dey, Damini; Gobbi, David G.; Surry, Kathleen J. M.; Slomka, Piotr J.; Peters, Terence M.

    2000-04-01

    A major limitation of the use of endoscopes in minimally invasive surgery is the lack of relative context between the endoscope and its surroundings. The purpose of this work is to map endoscopic images to surfaces obtained from 3D preoperative MR or CT data, for assistance in surgical planning and guidance. To test our methods, we acquired pre- operative CT images of a standard brain phantom from which object surfaces were extracted. Endoscopic images were acquired using a neuro-endoscope tracked with an optical tracking system, and the optical properties of the endoscope were characterized using a simple calibration procedure. Registration of the phantom and CT images was accomplished using markers that could be identified both on the physical object and in the pre-operative images. The endoscopic images were rectified for radial lens distortion, and then mapped onto the extracted surfaces via a ray-traced texture- mapping algorithm, which explicitly accounts for surface obliquity. The optical tracker has an accuracy of about 0.3 mm, which allows the endoscope tip to be localized to within mm. The mapping operation allows the endoscopic images to be effectively 'painted' onto the surfaces as they are acquired. Panoramic and stereoscopic visualization and navigation of the painted surfaces may then be reformed from arbitrary orientations, that were not necessarily those from which the original endoscopic views were acquired.

  16. Determination of trace element distribution in cancerous and normal human tissues by total reflection X-ray fluorescence analysis

    NASA Astrophysics Data System (ADS)

    von Czarnowski, D.; Denkhaus, E.; Lemke, K.

    1997-07-01

    The intention of this study was to establish a method for cancer diagnosis. For this purpose, different trace element distributions in carcinomas of the digestive tract and in normal tissues of human stomach, colon and rectum in correlation to the type of cancer were determined by total reflection X-ray fluorescence analysis (TXRF). The tissue samples were frozen and cut by a microtome into 10 μm sections, and a modified sample excision technique was introduced according to the aim of this research. After drying and spiking of the tissue sections, more than 20 elements, especially biologically relevant ones, were determined. The repeatabilities of measurements of element concentrations in malignant and normal tissues were calculated to be 10-30% (RSD) depending on the specific element. The concentration of Ca was found to be virtually constant (0.250±0.025 μg per 0.1 mm 3) in normal tissue and in carcinoma of the digestive organs. A significant diminution of Cr, Fe and Ni in carcinoma of the stomach, of Cr and Co in carcinoma of the colon and a significant accumulation of K in cancerous tissue of the colon and of Fe and K in neoplastic tissue of the rectum were discovered for a very limited population of patients.

  17. Simulating polarized light scattering in terrestrial snow based on bicontinuous random medium and Monte Carlo ray tracing

    NASA Astrophysics Data System (ADS)

    Xiong, Chuan; Shi, Jiancheng

    2014-01-01

    To date, the light scattering models of snow consider very little about the real snow microstructures. The ideal spherical or other single shaped particle assumptions in previous snow light scattering models can cause error in light scattering modeling of snow and further cause errors in remote sensing inversion algorithms. This paper tries to build up a snow polarized reflectance model based on bicontinuous medium, with which the real snow microstructure is considered. The accurate specific surface area of bicontinuous medium can be analytically derived. The polarized Monte Carlo ray tracing technique is applied to the computer generated bicontinuous medium. With proper algorithms, the snow surface albedo, bidirectional reflectance distribution function (BRDF) and polarized BRDF can be simulated. The validation of model predicted spectral albedo and bidirectional reflectance factor (BRF) using experiment data shows good results. The relationship between snow surface albedo and snow specific surface area (SSA) were predicted, and this relationship can be used for future improvement of snow specific surface area (SSA) inversion algorithms. The model predicted polarized reflectance is validated and proved accurate, which can be further applied in polarized remote sensing.

  18. Radiative Transfer Modeling of a Large Pool Fire by Discrete Ordinates, Discrete Transfer, Ray Tracing, Monte Carlo and Moment Methods

    NASA Technical Reports Server (NTRS)

    Jensen, K. A.; Ripoll, J.-F.; Wray, A. A.; Joseph, D.; ElHafi, M.

    2004-01-01

    Five computational methods for solution of the radiative transfer equation in an absorbing-emitting and non-scattering gray medium were compared on a 2 m JP-8 pool fire. The temperature and absorption coefficient fields were taken from a synthetic fire due to the lack of a complete set of experimental data for fires of this size. These quantities were generated by a code that has been shown to agree well with the limited quantity of relevant data in the literature. Reference solutions to the governing equation were determined using the Monte Carlo method and a ray tracing scheme with high angular resolution. Solutions using the discrete transfer method, the discrete ordinate method (DOM) with both S(sub 4) and LC(sub 11) quadratures, and moment model using the M(sub 1) closure were compared to the reference solutions in both isotropic and anisotropic regions of the computational domain. DOM LC(sub 11) is shown to be the more accurate than the commonly used S(sub 4) quadrature technique, especially in anisotropic regions of the fire domain. This represents the first study where the M(sub 1) method was applied to a combustion problem occurring in a complex three-dimensional geometry. The M(sub 1) results agree well with other solution techniques, which is encouraging for future applications to similar problems since it is computationally the least expensive solution technique. Moreover, M(sub 1) results are comparable to DOM S(sub 4).

  19. Correction of ultrasonic array images to improve reflector sizing and location in inhomogeneous materials using a ray-tracing model.

    PubMed

    Connolly, G D; Lowe, M J S; Temple, J A G; Rokhlin, S I

    2010-05-01

    The use of ultrasonic arrays has increased dramatically within recent years due to their ability to perform multiple types of inspection and to produce images of the structure through post-processing of received signals. Phased arrays offer many advantages over conventional transducers in the inspection of materials that are inhomogeneous with spatially varying anisotropic properties. In this paper, the arrays are focused on austenitic steel welds as a representative inhomogeneous material. The method of ray-tracing through a previously developed model of an inhomogeneous weld is shown, with particular emphasis on the difficulties presented by material inhomogeneity. The delay laws for the structure are computed and are used to perform synthetic focusing at the post-processing stage of signal data acquired by the array. It is demonstrated for a simulated austenitic weld that by taking material inhomogeneity and anisotropy into account, superior reflector location (and hence, superior sizing) results when compared to cases where these are ignored. The image is thus said to have been corrected. Typical images are produced from both analytical data in the frequency domain and data from finite element simulations in the time domain in a variety of wave modes, including cases with mode conversion and reflections. PMID:21117730

  20. Reflectance Estimation from Urban Terrestrial Images: Validation of a Symbolic Ray-Tracing Method on Synthetic Data

    NASA Astrophysics Data System (ADS)

    Coubard, F.; Brédif, M.; Paparoditis, N.; Briottet, X.

    2011-04-01

    Terrestrial geolocalized images are nowadays widely used on the Internet, mainly in urban areas, through immersion services such as Google Street View. On the long run, we seek to enhance the visualization of these images; for that purpose, radiometric corrections must be performed to free them from illumination conditions at the time of acquisition. Given the simultaneously acquired 3D geometric model of the scene with LIDAR or vision techniques, we face an inverse problem where the illumination and the geometry of the scene are known and the reflectance of the scene is to be estimated. Our main contribution is the introduction of a symbolic ray-tracing rendering to generate parametric images, for quick evaluation and comparison with the acquired images. The proposed approach is then based on an iterative estimation of the reflectance parameters of the materials, using a single rendering pre-processing. We validate the method on synthetic data with linear BRDF models and discuss the limitations of the proposed approach with more general non-linear BRDF models.

  1. Comparing the clinical outcomes in stereotactic body radiotherapy for lung tumors between Ray-Tracing and Monte-Carlo algorithms

    PubMed Central

    Song, Jin Ho; Kang, Ki Mun; Choi, Hoon-Sik; Jeong, Hojin; Ha, In Bong; Lee, Jong Deog; Kim, Ho Cheol; Jeong, Yi Yeong; Cho, Yu Ji; Lee, Seung Jun; Kim, Sung Hwan; Jang, In-Seok; Jeong, Bae Kwon

    2016-01-01

    Purpose The purpose of this study was to compare the clinical outcomes between the groups using Ray-Tracing (RAT) and Monte-Carlo (MC) calculation algorithms for stereotactic body radiotherapy (SBRT) of lung tumors. Materials and Methods Thirty-five patients received SBRT with CyberKnife for 47 primary or metastatic lung tumors. RAT was used for 22 targets in 12 patients, and MC for 25 targets in 23 patients. Total dose of 48 to 60 Gy was prescribed in 3 to 5 fractions on median 80% isodose line. The response rate, local control rate, and toxicities were compared between RAT and MC groups. Results The response rate was lower in the RAT group (77.3%) compared to the MC group (100%) (p = 0.008). The response rates showed an association with the mean dose to the gross tumor volume, which the doses were re-calculated with MC algorithm in both groups. However, the local control rate and toxicities did not differ between the groups. Conclusions The clinical outcome and toxicity of lung SBRT between the RAT and MC groups were similar except for the response rate when the same apparent doses were prescribed. The lower response rate in the RAT group, however, did not compromise the local control rates. As such, reducing the prescription dose for MC algorithm may be performed but done with caution. PMID:26544622

  2. Effects of Ice-Crystal Structure on Halo Formation: Cirrus Cloud Experimental and Ray-Tracing Modeling Studies

    NASA Technical Reports Server (NTRS)

    Sassen, Kenneth; Knight, Nancy C.; Takano, Yoshihide; Heymsfield, Andrew J.

    1994-01-01

    During the 1986 Project FIRE (First International Satellite Cloud Climatology Project Regional Experiment) field campaign, four 22 deg halo-producing cirrus clouds were studied jointly from a ground-based polarization lidar and an instrumented aircraft. The lidar data show the vertical cloud structure and the relative position of the aircraft, which collected a total of 84 slides by impaction, preserving the ice crystals for later microscopic examination. Although many particles were too fragile to survive impaction intact, a large fraction of the identifiable crystals were columns and radial bullet rosettes, with both displaying internal cavitations and radial plate-column combinations. Particles that were solid or displayed only a slight amount of internal structure were relatively rare, which shows that the usual model postulated by halo theorists, i.e., the randomly oriented, solid hexagonal crystal, is inappropriate for typical cirrus clouds. With the aid of new ray-tracing simulations for hexagonal hollow-ended column and bullet-rosette models, we evaluate the effects of more realistic ice-crystal structures on halo formation and lidar depolarization and consider why the common halo is not more common in cirrus clouds.

  3. Using Monte Carlo ray tracing simulations to model the quantum harmonic oscillator modes observed in uranium nitride

    NASA Astrophysics Data System (ADS)

    Lin, J. Y. Y.; Aczel, A. A.; Abernathy, D. L.; Nagler, S. E.; Buyers, W. J. L.; Granroth, G. E.

    2014-04-01

    Recently an extended series of equally spaced vibrational modes was observed in uranium nitride (UN) by performing neutron spectroscopy measurements using the ARCS and SEQUOIA time-of-flight chopper spectrometers [A. A. Aczel et al., Nat. Commun. 3, 1124 (2012), 10.1038/ncomms2117]. These modes are well described by three-dimensional isotropic quantum harmonic oscillator (QHO) behavior of the nitrogen atoms, but there are additional contributions to the scattering that complicate the measured response. In an effort to better characterize the observed neutron scattering spectrum of UN, we have performed Monte Carlo ray tracing simulations of the ARCS and SEQUOIA experiments with various sample kernels, accounting for nitrogen QHO scattering, contributions that arise from the acoustic portion of the partial phonon density of states, and multiple scattering. These simulations demonstrate that the U and N motions can be treated independently, and show that multiple scattering contributes an approximate Q-independent background to the spectrum at the oscillator mode positions. Temperature-dependent studies of the lowest few oscillator modes have also been made with SEQUOIA, and our simulations indicate that the T dependence of the scattering from these modes is strongly influenced by the uranium lattice.

  4. Using Monte Carlo Ray tracing to Understand the Vibrational Response of UN as Measured by Neutron Spectroscopy

    NASA Astrophysics Data System (ADS)

    Lin, J. Y. Y.; Aczel, A. A.; Abernathy, D. L.; Nagler, S. E.; Buyers, W. J. L.; Granroth, G. E.

    2014-03-01

    Recently neutron spectroscopy measurements, using the ARCS and SEQUOIA time-of-flight chopper spectrometers, observed an extended series of equally spaced modes in UN that are well described by quantum harmonic oscillator behavior of the N atoms. Additional contributions to the scattering are also observed. Monte Carlo ray tracing simulations with various sample kernels have allowed us to distinguish between the response from the N oscillator scattering, contributions that arise from the U partial phonon density of states (PDOS), and all forms of multiple scattering. These simulations confirm that multiple scattering contributes an ~ Q -independent background to the spectrum at the oscillator mode positions. All three of the aforementioned contributions are necessary to accurately model the experimental data. These simulations were also used to compare the T dependence of the oscillator modes in SEQUOIA data to that predicted by the binary solid model. This work was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy.

  5. Using Monte Carlo ray tracing simulations to model the quantum harmonic oscillator modes observed in uranium nitride

    SciTech Connect

    Lin, J. Y. Y.; Aczel, Adam A; Abernathy, Douglas L; Nagler, Stephen E; Buyers, W. J. L.; Granroth, Garrett E

    2014-01-01

    Recently an extended series of equally spaced vibrational modes was observed in uranium nitride (UN) by performing neutron spectroscopy measurements using the ARCS and SEQUOIA time-of- flight chopper spectrometers [A.A. Aczel et al, Nature Communications 3, 1124 (2012)]. These modes are well described by 3D isotropic quantum harmonic oscillator (QHO) behavior of the nitrogen atoms, but there are additional contributions to the scattering that complicate the measured response. In an effort to better characterize the observed neutron scattering spectrum of UN, we have performed Monte Carlo ray tracing simulations of the ARCS and SEQUOIA experiments with various sample kernels, accounting for the nitrogen QHO scattering, contributions that arise from the acoustic portion of the partial phonon density of states (PDOS), and multiple scattering. These simulations demonstrate that the U and N motions can be treated independently, and show that multiple scattering contributes an approximate Q-independent background to the spectrum at the oscillator mode positions. Temperature dependent studies of the lowest few oscillator modes have also been made with SEQUOIA, and our simulations indicate that the T-dependence of the scattering from these modes is strongly influenced by the uranium lattice.

  6. Comparison of VTEC from ground-based space geodetic techniques based on ray-traced mapping factors

    NASA Astrophysics Data System (ADS)

    Heinkelmann, Robert; Alizadeh, M. Mahdi; Schuh, Harald; Deng, Zhiguo; Zus, Florian; Etemadfard, M. Hossein

    2016-07-01

    For the derivation of vertical total electron content (VTEC) from slant total electron content (STEC), usually a standard approach is used based on mapping functions that assume a single-layer model of the ionosphere (e.g. IERS Conventions 2010). In our study we test the standard approach against a recently developed alternative which is based on station specific ray-traced mapping factors. For the evaluation of this new mapping concept, we compute VTEC at selected Very Long Baseline Interferometry (VLBI) stations using the dispersive delays and the corresponding formal errors obtained by observing extra-galactic radio sources at two radio frequencies in S- and X-bands by the permanent geodetic/astrometric program organized by the IVS (International VLBI Service for Geodesy and Astrometry). Additionally, by applying synchronous sampling and a consistent analysis configuration, we determine VTEC at Global Navigation Satellite System (GNSS) antennas using GPS (Global Positioning System) and/or GLONASS (Globalnaja nawigazionnaja sputnikowaja Sistema) observations provided by the IGS (International GNSS Service) that are operated in the vicinity of the VLBI antennas. We compare the VTEC time series obtained by the individual techniques over a period of about twenty years and describe their characteristics qualitatively and statistically. The length of the time series allows us to assess the long-term climatology of ionospheric VTEC during the last twenty years.

  7. Analysis of trace metals in thin silicon nitride films by total-reflection X-ray fluorescence

    NASA Astrophysics Data System (ADS)

    Vereecke, G.; Arnauts, S.; Van Doorne, P.; Kenis, K.; Onsia, B.; Verstraeten, K.; Schaekers, M.; Van Hoeymissen, J. A. B.; Heyns, M. M.

    2001-11-01

    The validity of a matrix withdrawal method for the analysis of trace metals in silicon nitride films on silicon wafers by total-reflection X-ray fluorescence has been evaluated with samples contaminated with diluted standard solutions of eight metals (Ca, V, Cr, Fe, Ni, Cu, Ta, W). The nitride matrix was removed by a decomposition step with HF vapor at ambient conditions followed by the vaporization of the product at a temperature higher than 240°C. The recovery of added metals was determined first directly after vaporization and secondly after preconcentration by the droplet collection (DC) method. The recovery of metals after vaporization at a temperature of 300±50°C was generally close to 100%, except for Cu whose recovery was approximately 40%. The efficiency of the DC step was approximately 50% for most metals but only 10-20% for Cu and Cr. Thus for most metals the total recovery was close to 50%, which is acceptable for analytical purpose. The recovery of Cu and Cr was studied in more detail considering the influence of the thickness of the nitride film, the vaporization temperature, and the composition of the DC solution. The total recovery of Cu increased from approximately 10 to 40% by lowering the temperature of the vaporization step and using a more concentrated DC solution. The recovery of Cr by DC was markedly influenced by the thickness of the nitride film with no great benefit of using a more concentrated DC solution.

  8. Application of vector ray tracing to the computation of Möbius shifts for the primary and secondary rainbows.

    PubMed

    Yu, Haitao; Shen, Jianqi; Tropea, Cameron

    2015-11-01

    The Möbius approximation for the primary rainbow and the Können approximation for the secondary rainbow have been modified to yield consistent predictions of the Möbius shift of the top and bottom rainbows, respectively. The applicability ranges of the Möbius and Können approximations are investigated by comparison to vector ray tracing (VRT) simulations. For the primary rainbow, these results indicate that the Möbius approximation is valid for spheroidal water droplets (m=1.333) in the range of aspect ratios 0.98≤a/c≤1.02. For the secondary rainbow, the Können approximation predicts the Möbius shift well for spheroidal water droplets within the range 0.99≤a/c≤1.01. For a spheroidal droplet with side-on incidence, the difference between the approximations and VRT simulations are discussed. Furthermore, the dependence of Möbius shifts on the relative refractive index of droplet is discussed. PMID:26560560

  9. No evidence for local adaptation in an invasive alien plant: field and greenhouse experiments tracing a colonization sequence

    PubMed Central

    Pahl, Anna T.; Kollmann, Johannes; Mayer, Andreas; Haider, Sylvia

    2013-01-01

    Background and Aims Local adaptation enables plant species to persist under different environmental conditions. Evolutionary change can occur rapidly in invasive annual species and has been shown to lead to local adaptation. However, the patterns and mechanisms of local adaptation in invasive species along colonization sequences are not yet understood. Thus, in this study the alien annual Impatiens glandulifera was used to investigate local adaptation to distinct habitats that have been consecutively invaded in central Europe. Methods A reciprocal transplant experiment was performed using 15 populations from alluvial deciduous forests, fallow meadows and coniferous upland forests, and a greenhouse experiment was performed in which plants from these habitats were grown under treatments reflecting the main habitat differentiators (shade, soil acidity, competition). Key Results Biomass production, specific leaf area, plant height and relative growth rate differed between habitats in the field experiment and between treatments in the greenhouse, but not between seed origins. Overall, there was no indication of local adaptation in either experiment. Conclusions Since I. glandulifera is a successful invader in many habitats without showing local adaptation, it is suggested that the species is coping with environmental variation by means of high phenotypic plasticity. The species seems to follow a ‘jack-and-master’ strategy, i.e. it is able to maintain high fitness under a wide range of environmental conditions, but performs particularly well in favourable habitats. Therefore, the proposed colonization sequence is likely to be based primarily on changes in propagule pressure. It is concluded that invasive alien plants can become dominant in distinct habitats without local adaptation. PMID:24214934

  10. Adapt

    NASA Astrophysics Data System (ADS)

    Bargatze, L. F.

    2015-12-01

    Active Data Archive Product Tracking (ADAPT) is a collection of software routines that permits one to generate XML metadata files to describe and register data products in support of the NASA Heliophysics Virtual Observatory VxO effort. ADAPT is also a philosophy. The ADAPT concept is to use any and all available metadata associated with scientific data to produce XML metadata descriptions in a consistent, uniform, and organized fashion to provide blanket access to the full complement of data stored on a targeted data server. In this poster, we present an application of ADAPT to describe all of the data products that are stored by using the Common Data File (CDF) format served out by the CDAWEB and SPDF data servers hosted at the NASA Goddard Space Flight Center. These data servers are the primary repositories for NASA Heliophysics data. For this purpose, the ADAPT routines have been used to generate data resource descriptions by using an XML schema named Space Physics Archive, Search, and Extract (SPASE). SPASE is the designated standard for documenting Heliophysics data products, as adopted by the Heliophysics Data and Model Consortium. The set of SPASE XML resource descriptions produced by ADAPT includes high-level descriptions of numerical data products, display data products, or catalogs and also includes low-level "Granule" descriptions. A SPASE Granule is effectively a universal access metadata resource; a Granule associates an individual data file (e.g. a CDF file) with a "parent" high-level data resource description, assigns a resource identifier to the file, and lists the corresponding assess URL(s). The CDAWEB and SPDF file systems were queried to provide the input required by the ADAPT software to create an initial set of SPASE metadata resource descriptions. Then, the CDAWEB and SPDF data repositories were queried subsequently on a nightly basis and the CDF file lists were checked for any changes such as the occurrence of new, modified, or deleted

  11. Stent enhancement using a locally adaptive unsharp masking filter in digital x-ray fluoroscopy

    NASA Astrophysics Data System (ADS)

    Jiang, Yuhao; Ekanayake, Eranda

    2014-03-01

    Low exposure X-ray fluoroscopy is used to guide some complicate interventional procedures. Due to the inherent high levels of noise, improving the visibility of some interventional devices such as stent will greatly benefit those interventional procedures. Stent, which is made up of tiny steel wires, is also suffered from contrast dilutions of large flat panel detector pixels. A novel adaptive unsharp masking filter has been developed to improve stent contrast in real-time applications. In unsharp masking processing, the background is estimated and subtracted from the original input image to create a foreground image containing objects of interest. A background estimator is therefore critical in the unsharp masking processing. In this specific study, orientation filter kernels are used as the background estimator. To make the process simple and fast, the kernels average along a line of pixels. A high orientation resolution of 18° is used. A nonlinear operator is then used to combine the information from the images generated from convolving the original background and noise only images with orientation filters. A computerized Monte Carlo simulation followed by ROC study is used to identify the best nonlinear operator. We then apply the unsharp masking filter to the images with stents present. It is shown that the locally adaptive unsharp making filter is an effective filter for improving stent visibility in the interventional fluoroscopy. We also apply a spatio-temporal channelized human observer model to quantitatively optimize and evaluate the filter.

  12. Adaptive grid artifact reduction in the frequency domain with spatial properties for x-ray images

    NASA Astrophysics Data System (ADS)

    Kim, Dong Sik; Lee, Sanggyun

    2012-03-01

    By applying band-rejection filters (BRFs) in the frequency domain, we can efficiently reduce the grid artifacts, which are caused by using the antiscatter grid in obtaining x-ray digital images. However, if the frequency component of the grid artifact is relatively close to that of the object, then simply applying a BRF may seriously distort the object and cause the ringing artifacts. Since the ringing artifacts are quite dependent on the shape of the object to be recovered in the spatial domain, the spatial property of the x-ray image should be considered in applying BRFs. In this paper, we propose an adaptive filtering scheme, which can cooperate such different properties in the spatial domain. In the spatial domain, we compare several approaches, such as the mangnitude, edge, and frequency-modulation (FM) model-based algorithms, to detect the ringing artifact or the grid artifact component. In order to perform a robust detection whether the ringing artifact is strong or not, we employ the FM model for the extracted signal, which corresponds to a specific grid artifact. A detection of the position for the ringing artifact is then conducted based on the slope detection algorithm, which is commonly used as an FM discriminator in the communication area. However, the detected position of the ringing artifact is not accurate. Hence, in order to obtain an accurate detection result, we combine the edge-based approach with the FM model approach. Numerical result for real x-ray images shows that applying BRFs in the frequency domain in conjunction with the spatial property of the ringing artifact can successfully remove the grid artifact, distorting the object less.

  13. Combined Application of QEM-SEM and Hard X-ray Microscopy to Determine Mineralogical Associations and Chemcial Speciation of Trace Metals

    SciTech Connect

    M Grafe; M Landers; R Tappero; P Austin; B Gan; A Grabsch; C Klauber

    2011-12-31

    We describe the application of quantitative evaluation of mineralogy by scanning electron microscopy in combination with techniques commonly available at hard X-ray microprobes to define the mineralogical environment of a bauxite residue core segment with the more specific aim of determining the speciation of trace metals (e.g., Ti, V, Cr, and Mn) within the mineral matrix. Successful trace metal speciation in heterogeneous matrices, such as those encountered in soils or mineral residues, relies on a combination of techniques including spectroscopy, microscopy, diffraction, and wet chemical and physical experiments. Of substantial interest is the ability to define the mineralogy of a sample to infer redox behavior, pH buffering, and mineral-water interfaces that are likely to interact with trace metals through adsorption, coprecipitation, dissolution, or electron transfer reactions. Quantitative evaluation of mineralogy by scanning electron microscopy coupled with micro-focused X-ray diffraction, micro-X-ray fluorescence, and micro-X-ray absorption near edge structure (mXANES) spectroscopy provided detailed insights into the composition of mineral assemblages and their effect on trace metal speciation during this investigation. In the sample investigated, titanium occurs as poorly ordered ilmenite, as rutile, and is substituted in iron oxides. Manganese's spatial correlation to Ti is closely linked to ilmenite, where it appears to substitute for Fe and Ti in the ilmenite structure based on its mXANES signature. Vanadium is associated with ilmenite and goethite but always assumes the +4 oxidation state, whereas chromium is predominantly in the +3 oxidation state and solely associated with iron oxides (goethite and hematite) and appears to substitute for Fe in the goethite structure.

  14. Evidence for tropospheric wind shear excitation of high-phase-speed gravity waves reaching the mesosphere using the ray-tracing technique

    NASA Astrophysics Data System (ADS)

    Pramitha, M.; Venkat Ratnam, M.; Taori, A.; Krishna Murthy, B. V.; Pallamraju, D.; Vijaya Bhaskar Rao, S.

    2015-03-01

    Sources and propagation characteristics of high-frequency gravity waves observed in the mesosphere using airglow emissions from Gadanki (13.5° N, 79.2° E) and Hyderabad (17.5° N, 78.5° E) are investigated using reverse ray tracing. Wave amplitudes are also traced back, including both radiative and diffusive damping. The ray tracing is performed using background temperature and wind data obtained from the MSISE-90 and HWM-07 models, respectively. For the Gadanki region, the suitability of these models is tested. Further, a climatological model of the background atmosphere for the Gadanki region has been developed using nearly 30 years of observations available from a variety of ground-based (MST radar, radiosondes, MF radar) and rocket- and satellite-borne measurements. ERA-Interim products are utilized for constructing background parameters corresponding to the meteorological conditions of the observations. With the reverse ray-tracing method, the source locations for nine wave events could be identified to be in the upper troposphere, whereas for five other events the waves terminated in the mesosphere itself. Uncertainty in locating the terminal points of wave events in the horizontal direction is estimated to be within 50-100 km and 150-300 km for Gadanki and Hyderabad wave events, respectively. This uncertainty arises mainly due to non-consideration of the day-to-day variability in the tidal amplitudes. Prevailing conditions at the terminal points for each of the 14 events are provided. As no convection in and around the terminal points is noticed, convection is unlikely to be the source. Interestingly, large (~9 m s-1km-1) vertical shears in the horizontal wind are noticed near the ray terminal points (at 10-12 km altitude) and are thus identified to be the source for generating the observed high-phase-speed, high-frequency gravity waves.

  15. Modeling Coniferous Canopy Structure over Extensive Areas for Ray Tracing Simulations: Scaling from the Leaf to the Stand Level

    NASA Astrophysics Data System (ADS)

    van Aardt, J. A.; van Leeuwen, M.; Kelbe, D.; Kampe, T.; Krause, K.

    2015-12-01

    Remote sensing is widely accepted as a useful technology for characterizing the Earth surface in an objective, reproducible, and economically feasible manner. To date, the calibration and validation of remote sensing data sets and biophysical parameter estimates remain challenging due to the requirements to sample large areas for ground-truth data collection, and restrictions to sample these data within narrow temporal windows centered around flight campaigns or satellite overpasses. The computer graphics community have taken significant steps to ameliorate some of these challenges by providing an ability to generate synthetic images based on geometrically and optically realistic representations of complex targets and imaging instruments. These synthetic data can be used for conceptual and diagnostic tests of instrumentation prior to sensor deployment or to examine linkages between biophysical characteristics of the Earth surface and at-sensor radiance. In the last two decades, the use of image generation techniques for remote sensing of the vegetated environment has evolved from the simulation of simple homogeneous, hypothetical vegetation canopies, to advanced scenes and renderings with a high degree of photo-realism. Reported virtual scenes comprise up to 100M surface facets; however, due to the tighter coupling between hardware and software development, the full potential of image generation techniques for forestry applications yet remains to be fully explored. In this presentation, we examine the potential computer graphics techniques have for the analysis of forest structure-function relationships and demonstrate techniques that provide for the modeling of extremely high-faceted virtual forest canopies, comprising billions of scene elements. We demonstrate the use of ray tracing simulations for the analysis of gap size distributions and characterization of foliage clumping within spatial footprints that allow for a tight matching between characteristics

  16. Surface roughness estimation by inversion of the Hapke photometric model on optical data simulated using a ray tracing code

    NASA Astrophysics Data System (ADS)

    Champion, J.; Ristorcelli, T.; Ferrari, C. C.; Briottet, X.; Jacquemoud, S.

    2013-12-01

    Surface roughness is a key physical parameter that governs various processes (incident radiation distribution, temperature, erosion,...) on Earth and other Solar System objects. Its impact on the scattering function of incident electromagnetic waves is difficult to model. In the 80's, Hapke provided an approximate analytic solution for the bidirectional reflectance distribution function (BRDF) of a particulate medium and, later on, included the effect of surface roughness as a correction factor for the BRDF of a smooth surface. This analytical radiative transfer model is widely used in solar system science whereas its ability to remotely determine surface roughness is still a question at issue. The validation of the Hapke model has been only occasionally undertaken due to the lack of radiometric data associated with field measurement of surface roughness. We propose to validate it on Earth, on several volcanic terrains for which very high resolution digital elevation models are available at small scale. We simulate the BRDF of these DEMs thanks to a ray-tracing code and fit them with the Hapke model to retrieve surface roughness. The mean slope angle of the facets, which quantifies surface roughness, can be fairly well retrieved when most conditions are met, i.e. a random-like surface and little multiple scattering between the facets. A directional sensitivity analysis of the Hapke model confirms that both surface intrinsic optical properties (facet's reflectance or single scattering albedo) and roughness are the most influential variables on ground BRDFs. Their interactions in some directions explain why their separation may be difficult, unless some constraints are introduced in the inversion process. Simulation of soil surface BRDF at different illumination and viewing angles

  17. Determination of a three-dimensional velocity structure for the Southeastern of Mexico, by means of seismic ray tracing.

    NASA Astrophysics Data System (ADS)

    Rodriguez-Perez, Q.; Valdes-Gozalez, C.

    2007-05-01

    The objective of the present study is to obtain a three-dimensional velocity structure for three different tectonic provinces (Oaxaca, Chiapas and north of Guatemala). The Southeastern of Mexico is a seismic active region, in which several geologic structures of great importance are located: the Tehuantepec ridge, the Central-American volcanic arc, the Chiapas batholit, the extension of the Motagua-Polochic fault system, and also the existance of complex tectonostratigrafic terrenes at cortical level. In this area of study, there are a considerable number of tectonic studies and cortical velocity models (1D). For this reason is desired to obtain a three-dimensional realistic velocity model that agrees with the results obtained in previous studies. To make it posible, a preliminary velocity model has been proposed and has been discretized, and is now at the test stage. Also the geometry of the Cocos plate is determined (variation of the subduction angle) and we will try to obtain the interaction between the Motagua-Polochic fault system and the previously described subduction provinces. We will use P and S waves, from local and regional earthquakes from 1994 to 2004 reported by National Seismological Service (SSN) in eight broadband seismic stations in the Southeastern of Mexico (CCIG, CMIG, EVV, HUIG, OXIG, SCX TPX, TUIG). In the study earthquake relocalizations with the DD method will be performed, and a 3-D ray tracing will be used to test the seismic model. The 3-D velocity model will allow us to better understand the wave propagation characteristics, and apply them to the mitigation of the seismic risk in the region. 1. Earth Science Graduate Program. UNAM. 2. Institute of Geophysics. UNAM.

  18. Educational X-Ray Experiments and XRF Measurements with a Portable Setup Adapted for the Characterization of Cultural Heritage Objects

    ERIC Educational Resources Information Center

    Sianoudis, I.; Drakaki, E.; Hein, A.

    2010-01-01

    It is common to modify valuable, sophisticated equipment, originally acquired for other purposes, to adapt it for the needs of educational experiments, with great didactic effectiveness. The present project concerns a setup developed from components of a portable system for energy dispersive x-ray fluorescence spectroscopy (EDXRF). Two educational…

  19. Heel effect adaptive flat field correction of digital x-ray detectors

    SciTech Connect

    Yu, Yongjian; Wang, Jue

    2013-08-15

    Purpose: Anode heel effect renders large-scale background nonuniformities in digital radiographs. Conventional offset/gain calibration is performed at mono source-to-image distance (SID), and disregards the SID-dependent characteristic of heel effect. It results in a residual nonuniform background in the corrected radiographs when the SID settings for calibration and correction differ. In this work, the authors develop a robust and efficient computational method for digital x-ray detector gain correction adapted to SID-variant heel effect, without resorting to physical filters, phantoms, complicated heel effect models, or multiple-SID calibration and interpolation.Methods: The authors present the Duo-SID projection correction method. In our approach, conventional offset/gain calibrations are performed only twice, at the minimum and maximum SIDs of the system in typical clinical use. A fast iterative separation algorithm is devised to extract the detector gain and basis heel patterns from the min/max SID calibrations. The resultant detector gain is independent of SID, while the basis heel patterns are parameterized by the min- and max-SID. The heel pattern at any SID is obtained from the min-SID basis heel pattern via projection imaging principles. The system gain desired at a specific acquisition SID is then constructed using the projected heel pattern and detector gain map.Results: The method was evaluated for flat field and anatomical phantom image corrections. It demonstrated promising improvements over interpolation and conventional gain calibration/correction methods, lowering their correction errors by approximately 70% and 80%, respectively. The separation algorithm was able to extract the detector gain and heel patterns with less than 2% error, and the Duo-SID corrected images showed perceptually appealing uniform background across the detector.Conclusions: The Duo-SID correction method has substantially improved on conventional offset/gain corrections for

  20. Evidence for an adaptive response to radiation damage in plant cells conditioned with X-rays or incorporated tritium.

    PubMed

    Cortés, F; Domínguez, I; Mateos, S; Piñero, J; Mateos, J C

    1990-03-01

    Allium cepa root-tip cells were first exposed to low 'conditioning' doses of ionizing radiation: to X-rays (0.06 or 0.26 Gy) or to incorporated tritium (1.8 x 10(4) or 7.2 x 10(4) Bq/ml; specific activity: 740.0 GBq/mmol) and subsequently given a 'challenge' dose of 1.5 Gy of X-rays. A reduction in X-ray-induced chromosomal damage was brought about by prior exposure to 0.26 Gy of X-rays, while cells receiving the lower conditioning dose (0.06 Gy of X-rays) did not show any significant reduction. In cells grown in the presence of [3H]TdR on the other hand, the adaptive response was evident after both doses given. The results are essentially in agreement with those published by Wolff's group for human lymphocytes in showing that plant cells in vivo can become 'adapted' by exposure to low-level irradiation so that they become more resistant to the clastogenic effects of X-rays delivered subsequently. PMID:1968946

  1. Adaptation of a 2D in-gel kinase assay to trace phosphotransferase activities in the human pathogen Leishmania donovani.

    PubMed

    Schmidt-Arras, Dirk; Leclercq, Olivier; Gherardini, Pier Federico; Helmer-Citterich, Manuela; Faigle, Wolfgang; Loew, Damarys; Späth, Gerald F

    2011-08-24

    The protozoan parasite Leishmania donovani undergoes various developmental transitions during its infectious cycle that are triggered by environmental signals encountered inside insect and vertebrate hosts. Intracellular differentiation of the pathogenic amastigote stage is induced by pH and temperature shifts that affect protein kinase activities and downstream protein phosphorylation. Identification of parasite proteins with phosphotransferase activity during intracellular infection may reveal new targets for pharmacological intervention. Here we describe an improved protocol to trace this activity in L. donovani extracts at high resolution combining in-gel kinase assay and two-dimensional gel electrophoresis. This 2D procedure allowed us to identify proteins that are associated with amastigote ATP-binding, ATPase, and phosphotransferase activities. The 2D in-gel kinase assay, in combination with recombinant phospho-protein substrates previously identified by phospho-proteomics analyses, provides a novel tool to establish specific protein kinase-substrate relationships thus improving our understanding of Leishmania signal transduction with relevance for future drug development. PMID:21443974

  2. A simple way of characterizing x-ray downwards-deflecting mirror-bender assemblies using the long trace profiler

    SciTech Connect

    Assoufid, L.; Her, P.

    1999-11-22

    A simple device composed of a modular double-pentaprism system that enables the long trace profiler (LTP) to measure mirrors in nonconventional ways, i.e., in the vertical-downward and sideways positions, has been devised and implemented in the Advanced Photon Source (APS) long trace profiler (LTP II). The systems is very useful in calibrating mirror-bender assemblies. This paper describes the system and gives results of measurements performed with it on a mirror used at the APS.

  3. Comparative study of trace element contents in human full-term placenta and fetal membranes by total reflection X-ray fluorescence

    NASA Astrophysics Data System (ADS)

    Kubala-Kukuś, A.; Banaś, D.; Braziewicz, J.; Majewska, U.; Pajek, M.

    2003-04-01

    The total reflection X-ray fluorescence (TXRF) method was applied to study the influence of environmental pollution on the contents of trace elements in human full-term placenta and fetal membranes. The samples were collected from the donors living in two regions characterised by different levels of environmental pollution. In this comparative study, based on relatively large (˜100) populations, the concentrations of approximately 20 trace elements (P-Pb) were determined in the samples. In particular, the paper discusses the role of 'truncation' of measured concentration distribution by the detection limit of the TXRF method in context of comparative studies. First, the importance of the developed method of reconstruction of original concentration distribution, to derive the correct concentrations of trace elements, is described and demonstrated and, second, the statistical tests, which can be used to compare the truncated, or reconstructed, concentration distributions are discussed. Finally, the statistically significant differences of trace element concentrations found in both populations are presented and summarised.

  4. Development of an adaptable coherent x-ray diffraction microscope with the emphasis on imaging hydrated specimens

    SciTech Connect

    Nam, Daewoong; Park, Jaehyun; Shimada, Hiroki; Kim, Sangsoo; Kim, Sunam; Kohmura, Yoshiki; Ishikawa, Tetsuya; Song, Changyong; Gallagher-Jones, Marcus

    2013-11-15

    This paper describes the development of a versatile coherent x-ray diffraction microscope capable of imaging biological specimens in solution. The microscope is a flexible platform accommodating various conditions, from low vacuum (10{sup −2} Pa) to helium gas filled ambient pressure. This flexibility greatly expands the application area, from in situ materials science to biology systems in their native state, by significantly relaxing restrictions to the sample environment. The coherent diffraction microscope has been used successfully to image a yeast cell immersed in buffer solution. We believe that the design of this coherent diffraction microscope can be directly adapted to various platforms such as table top soft x-ray laser, synchrotron x-ray sources, and x-ray free electron laser with minor relevant adjustments.

  5. Trace metal ion partitioning at polymer film-metal oxide interfaces: long-period X-ray standing wave study.

    PubMed

    Yoon, Tae Hyun; Trainor, Thomas P; Eng, Peter J; Bargar, John R; Brown, Gordon E

    2005-05-10

    The distributions of Pb(II) and As(V)O4(3-) ions in the interfacial region between thin poly(acrylic acid) (PAA) coatings and aalpha-A12O3(0001), alpha-Al2O3(1-102), and alpha-Fe2O3(0001) single-crystal substrates were studied using long-period X-ray standing wave fluorescent yield (XSW-FY) and X-ray reflectivity techniques. The PAA film serves as a simplified analogue of natural organic matter (NOM) coatings on mineral surfaces. Such coatings are often assumed to play an important role in the partitioning and speciation of trace heavy metals in soils and aquatic systems. On the alpha-Al2O3(1-102) surface, Pb(II) ions were found to preferentially bind to the PAA coating, even at sub-micromolar Pb(II) concentrations, and to partition increasingly onto the metal oxide surface as the Pb(II) concentration was increased ([Pb(II)] = 5 x 10(-8) to 2 x 10(-5) M, pH = 4.5; 0.01 M NaCl background electrolyte). This observation suggests that the binding sites in the PAA coating outcompete those on the alpha-Al2O3(1-102) surface for Pb(II) under these conditions. The As(V)O4(3-) oxoanion partitions preferentially to the L-Al2O3(1-102) surface for the As(V)O4(3-) concentrations examined (1 x 10(-7) to 5 x 10(-7) M, pH = 4.5; 0.01 M NaCl background electrolyte). Partitioning of Pb(II) (at 1 x 10(-7) M and pH 4.5) was also examined at PAA/alpha-Al2O3(0001), and PAA/alpha-Fe2O3(0001) interfaces using XSW-FY measurements. Our results show that the PAA coating was the dominant sink for Pb(II) in all three samples; however, the relative order of reactivity of these metal oxide surfaces with respect to Pb(II) sorption is alpha-Fe2O3(0001) > alpha-Al2O3(1-102) > alpha-Al2O3(0001). This order is consistent with that found in previous studies of the PAA-free surfaces. These XSW results strongly suggest that the characteristics of the organic film (i.e., binding affinity, type, and density of binding sites) as well as metal oxide substrate reactivity are key factors determining the

  6. Arbitrary Lagrangian Eulerian Adaptive Mesh Refinement

    SciTech Connect

    Koniges, A.; Eder, D.; Masters, N.; Fisher, A.; Anderson, R.; Gunney, B.; Wang, P.; Benson, D.; Dixit, P.

    2009-09-29

    This is a simulation code involving an ALE (arbitrary Lagrangian-Eulerian) hydrocode with AMR (adaptive mesh refinement) and pluggable physics packages for material strength, heat conduction, radiation diffusion, and laser ray tracing developed a LLNL, UCSD, and Berkeley Lab. The code is an extension of the open source SAMRAI (Structured Adaptive Mesh Refinement Application Interface) code/library. The code can be used in laser facilities such as the National Ignition Facility. The code is alsi being applied to slurry flow (landslides).

  7. Gamma-Ray Burst Dynamics and Afterglow Radiation from Adaptive Mesh Refinement, Special Relativistic Hydrodynamic Simulations

    NASA Astrophysics Data System (ADS)

    De Colle, Fabio; Granot, Jonathan; López-Cámara, Diego; Ramirez-Ruiz, Enrico

    2012-02-01

    We report on the development of Mezcal-SRHD, a new adaptive mesh refinement, special relativistic hydrodynamics (SRHD) code, developed with the aim of studying the highly relativistic flows in gamma-ray burst sources. The SRHD equations are solved using finite-volume conservative solvers, with second-order interpolation in space and time. The correct implementation of the algorithms is verified by one-dimensional (1D) and multi-dimensional tests. The code is then applied to study the propagation of 1D spherical impulsive blast waves expanding in a stratified medium with ρvpropr -k , bridging between the relativistic and Newtonian phases (which are described by the Blandford-McKee and Sedov-Taylor self-similar solutions, respectively), as well as to a two-dimensional (2D) cylindrically symmetric impulsive jet propagating in a constant density medium. It is shown that the deceleration to nonrelativistic speeds in one dimension occurs on scales significantly larger than the Sedov length. This transition is further delayed with respect to the Sedov length as the degree of stratification of the ambient medium is increased. This result, together with the scaling of position, Lorentz factor, and the shock velocity as a function of time and shock radius, is explained here using a simple analytical model based on energy conservation. The method used for calculating the afterglow radiation by post-processing the results of the simulations is described in detail. The light curves computed using the results of 1D numerical simulations during the relativistic stage correctly reproduce those calculated assuming the self-similar Blandford-McKee solution for the evolution of the flow. The jet dynamics from our 2D simulations and the resulting afterglow light curves, including the jet break, are in good agreement with those presented in previous works. Finally, we show how the details of the dynamics critically depend on properly resolving the structure of the relativistic flow.

  8. Quantification of trace arsenic in soils by field-portable X-ray fluorescence spectrometry: considerations for sample preparation and measurement conditions.

    PubMed

    Parsons, Chris; Margui Grabulosa, Eva; Pili, Eric; Floor, Geerke H; Roman-Ross, Gabriela; Charlet, Laurent

    2013-11-15

    Recent technological improvements have led to the widespread adoption of field portable energy dispersive X-ray fluorescence (FP-XRF) by governmental agencies, environmental consultancies and research institutions. FP-XRF units often include analysis modes specifically designed for the quantification of trace elements in soils. Using these modes, X-ray tube based FP-XRF units can offer almost "point and shoot" ease of use and results comparable to those of laboratory based instruments. Nevertheless, FP-XRF analysis is sensitive to spectral interferences as well as physical and chemical matrix effects which can result in decreased precision and accuracy. In this study, an X-ray tube-based FP-XRF analyser was used to determine trace (low ppm) concentrations of As in a floodplain soil. The effect of different sample preparation and analysis conditions on precision and accuracy were systematically evaluated. We propose strategies to minimise sources of error and maximise data precision and accuracy, achieving in situ limits of detection and precision of 6.8 ppm and 14.4%RSD, respectively for arsenic. We demonstrate that soil moisture, even in relatively dry soils, dramatically affects analytical performance with a signal loss of 37% recorded for arsenic at 20 wt% soil moisture relative to dry soil. We also highlight the importance of the use of certified reference materials and independent measurement methods to ensure accurate correction of field values. PMID:22819961

  9. Locating radiation hazards and sources within contaminated areas by implementing a reverse ray tracing technique in the RadBall™ technology.

    PubMed

    Farfán, Eduardo B; Stanley, Steven; Holmes, Christopher; Lennox, Kathryn; Oldham, Mark; Clift, Corey; Thomas, Andrew; Adamovics, John

    2012-02-01

    RadBall™ is a novel technology that can locate unknown radioactive hazards within contaminated areas, hot cells, and gloveboxes. The device consists of a colander-like outer tungsten collimator that houses a radiation-sensitive polymer semisphere. The collimator has a number of small holes; as a result, specific areas of the polymer are exposed to radiation, becoming increasingly more opaque in proportion to the absorbed dose. The polymer semisphere is imaged in an optical computed tomography scanner that produces a high resolution three-dimensional map of optical attenuation coefficients. A subsequent analysis of the optical attenuation data, using a reverse ray tracing technique, provides information on the spatial distribution of gamma-ray sources in a given area, forming a three-dimensional characterization of the area of interest. The RadBall™ technology and its reverse ray tracing technique were investigated using known radiation sources at the Savannah River Site's Health Physics Instrument Calibration Laboratory and unknown sources at the Savannah River National Laboratory's Shielded Cells facility. PMID:22217592

  10. Rapid screening of heavy metals and trace elements in environmental samples using portable X-ray fluorescence spectrometer, A comparative study

    PubMed Central

    McComb, Jacqueline Q.; Rogers, Christian; Han, Fengxiang X.; Tchounwou, Paul B.

    2014-01-01

    With industrialization, great amounts of trace elements and heavy metals have been excavated and released on the surface of the earth and dissipated into the environments. Rapid screening technology for detecting major and trace elements as well as heavy metals in variety of environmental samples is most desired. The objectives of this study were to determine the detection limits, accuracy, repeatability and efficiency of a X-ray fluorescence spectrometer (Niton XRF analyzer) in comparison with the traditional analytical methods, inductively coupled plasma optical emission spectrometer (ICP-OES) and inductively coupled plasma optical emission spectrometer (ICP-MS) in screening of major and trace elements of environmental samples including estuary soils and sediments, contaminated soils, and biological samples. XRF is a fast and non-destructive method in measuring the total concentration of multi--elements simultaneously. Contrary to ICP-OES and ICP-MS, XRF analyzer is characterized by the limited preparation required for solid samples, non-destructive analysis, increased total speed and high throughout, the decreased production of hazardous waste and the low running costs as well as multi-elemental determination and portability in the fields. The current comparative study demonstrates that XRF is a good rapid non-destructive method for contaminated soils, sediments and biological samples containing higher concentrations of major and trace elements. Unfortunately, XRF does not have sensitive detection limits of most major and trace elements as ICP-OES or ICP-MS but it may serve as a rapid screening tool for locating hot spots of uncontaminated field soils and sediments. PMID:25861136

  11. Synchrotron-based x-ray fluorescence applied to invertebrates to investigate the role of essential trace elements in a biological process

    NASA Astrophysics Data System (ADS)

    Rao, D. V.; Swapna, M.; Cesareo, R.; Brunetti, A.; Akatsuka, T.; Yuasa, T.; Takeda, T.; Gigante, G. E.

    2012-03-01

    The fluorescence spectra have been detected by exciting invertebrate individual structures, such as external shell, embedded soft-tissue and operculum, with 8, 10 and 12 keV synchrotron x-rays, to find out about the accumulation of trace elements and biological processes in a small animal shell. A new hard x-ray micro-spectroscopy beamline facility, X27A, available at National Synchrotron Light Source, Brookhaven National Laboratory, USA, was utilized. It provided the primary beam in a small spot of the order of ~10 μm, for focusing. With this spatial resolution and high flux throughput, the synchrotron-induced x-ray fluorescent intensities were measured using a liquid-nitrogen-cooled 13-element energy-dispersive high-purity germanium detector. The fluorescence spectrum arising from the sample as a whole was assessed. Calcium is predominant in these aquatic organisms and a normal constituent of all living matter. The percentage of calcium is lower in the soft tissue, as distinguished from other samples, and the contributions of Cu and Zn are considerable. The latter possibility is due to some ground-based minerals, which may enter the sample when it traverses the land, and get attached to the soft tissue. This way, the accumulation of biominerals will be enhanced in addition to the originally presented ones. The presence of other bioactive trace elements such as Ti, Cr, Mn, Fe, Ni, Cu, Zn, As, Rb and Sr was observed in low proportions. Some of these trace elements, for example, Mn, Fe, Cu, Rb and Sr, may induce toxic effects and the other potentially toxic elements, Ni and As, induce disorder in the organism if present in higher and lower proportions.

  12. Improved robustness study of a shock ignited target, with DUED code including non-local electron transport and 3D laser ray-tracing

    NASA Astrophysics Data System (ADS)

    Atzeni, Stefano; Marocchino, Alberto; Schiavi, Angelo

    2016-03-01

    Accurate descriptions of laser power coupling to the plasma and electron energy transport are crucial for designing shock-ignition targets and assessing their robustness (in particular with regard to laser and positioning errors). To this purpose, the 2D DUED laser fusion code has been improved with the inclusion of a 3D laser ray-tracing scheme and a model for non-local electron transport. 2D simulations with the upgraded code are presented; the dependence of the fusion yield vs target displacement is studied. Two different irradiation configurations are considered.

  13. Hamiltonian-based ray-tracing method with triangular-mesh representation for a large-scale cloaking device with an arbitrary shape.

    PubMed

    Tanaka, Tatsuo; Matoba, Osamu

    2016-05-01

    Hamiltonian-based ray-tracing technique with mesh representation is presented for designing large-scale cloaking devices with three-dimensional arbitrary shapes, which have inhomogeneity and anisotropy in their electric permittivity and magnetic permeability. In order to deal with arbitrary shapes, the surfaces of the cloaking devices are represented by triangular meshes. Comparison between the result of cloaking simulations with the mesh representation and those with the rigorous function representation is presented. The numerical results showed that fine-mesh resolution is required for accurate evaluation of cloaking performances. PMID:27140356

  14. Direct comparison of full-wave and ray-tracing methods for a simple model of multi-dimensional mode conversion

    NASA Astrophysics Data System (ADS)

    Xiao, Y.; Richardson, A.; Tracy, E.

    2007-11-01

    Mode conversion can occur in a nonuniform plasma when two waves of different character are locally resonant. Jaun et al. have recently developed a numerical ray-tracing algorithm for realistic tokamak models that accounts for the ray splitting that occurs at conversions [1,2]. Here we present a comparison of ray-based and full-wave methods by considering a simple model consisting of a pair of coupled wave equations in two spatial dimensions. The two spatially-dependent wave speeds, c1(x,y) and c2(x,y) are distinct for almost all (x,y), and are equal only along a line where conversion occurs. We launch a WKB-type wave packet in channel 1. There is initially no excitation in channel 2. Absorbing boundary conditions are used to avoid reflections which would complicate the results. From the full-wave output, we compute the initial energy density as a function of position and consider its evolution along a family of rays which undergo conversion. These full-wave results are then compared to the ray-based predictions. [1] A.Jaun, E.Tracy and A.Kaufman, Plasma Phys. Control. Fusion 49, 43-67 (2007). [2] E.Tracy, A.Kaufman and A.Jaun, to appear in Phys. Plasmas.

  15. Development of a Laboratory Micron-Resolution X-ray Microprobe to Map Mineralogy and Trace Elements at PPM Sensitivity for Digital Rock, Magma, and Mining Applications

    NASA Astrophysics Data System (ADS)

    Yun, W.; Lewis, S.; Stripe, B.; Chen, S.; Reynolds, D.; Spink, I.; Lyon, A.

    2015-12-01

    We are developing a patent-pending x-ray microprobe with substantially unprecedented performance attributes: <5 μm spot on the sample (with 1 μm targeted), large working distances of >2 cm, narrow spectral bandwidth, and large x-ray flux. The outstanding performance is enabled by: (1) a revolutionary new type of high flux x-ray source designed to be >10X brighter than the brightest rotating anode x-ray source available; (2) an axially symmetric x-ray mirror lens with large solid angle collection and high focusing efficiency; and (3) a detector configuration that enables the collection of 10X more x-rays than current microXRF designs. The sensitivity will be ppm-scale, far surpassing charged particle analysis (e.g. EPMA and SEM-EDS), and >1000X throughput over the leading micro-XRFs. Despite the introduction of a number of laboratory microXRF systems in the past decade, the state-of-the-art has been limited primarily by low resolution (~30 μm) and low throughput. This is substantially attributable to a combination of low x-ray source brightness and poor performance x-ray optics. Here we present our initial results in removing the x-ray source bottleneck, in which we use a novel x-ray source using Fine Anode Array Source Technology (Sigray FAAST™). When coupled with our proprietary high efficiency x-ray mirror lens, the throughput achieved is comparable to that of many synchrotron microXRF beamlines. Potential applications of the x-ray microprobe include high throughput mapping of mineralogy at high resolution, including trace elements, such as rare earth metals, and deposits (e.g. siderite, clays), with ppm sensitivity, providing information for properties such as permeability and elastic/mechanical properties, and to provide compositional information for Digital Rock. Additional applications include those in which the limited penetration of electrons limits achieving adequate statistics, such as determining the concentration of precious minerals in mine

  16. A real-time regional adaptive exposure method for saving dose-area product in x-ray fluoroscopy

    PubMed Central

    Burion, Steve; Speidel, Michael A.; Funk, Tobias

    2013-01-01

    Purpose: Reduction of radiation dose in x-ray imaging has been recognized as a high priority in the medical community. Here the authors show that a regional adaptive exposure method can reduce dose-area product (DAP) in x-ray fluoroscopy. The authors' method is particularly geared toward providing dose savings for the pediatric population. Methods: The scanning beam digital x-ray system uses a large-area x-ray source with 8000 focal spots in combination with a small photon-counting detector. An imaging frame is obtained by acquiring and reconstructing up to 8000 detector images, each viewing only a small portion of the patient. Regional adaptive exposure was implemented by varying the exposure of the detector images depending on the local opacity of the object. A family of phantoms ranging in size from infant to obese adult was imaged in anteroposterior view with and without adaptive exposure. The DAP delivered to each phantom was measured in each case, and noise performance was compared by generating noise arrays to represent regional noise in the images. These noise arrays were generated by dividing the image into regions of about 6 mm2, calculating the relative noise in each region, and placing the relative noise value of each region in a one-dimensional array (noise array) sorted from highest to lowest. Dose-area product savings were calculated as the difference between the ratio of DAP with adaptive exposure to DAP without adaptive exposure. The authors modified this value by a correction factor that matches the noise arrays where relative noise is the highest to report a final dose-area product savings. Results: The average dose-area product saving across the phantom family was (42 ± 8)% with the highest dose-area product saving in the child-sized phantom (50%) and the lowest in the phantom mimicking an obese adult (23%). Conclusions: Phantom measurements indicate that a regional adaptive exposure method can produce large DAP savings without compromising the

  17. A real-time regional adaptive exposure method for saving dose-area product in x-ray fluoroscopy

    SciTech Connect

    Burion, Steve; Funk, Tobias; Speidel, Michael A.

    2013-05-15

    Purpose: Reduction of radiation dose in x-ray imaging has been recognized as a high priority in the medical community. Here the authors show that a regional adaptive exposure method can reduce dose-area product (DAP) in x-ray fluoroscopy. The authors' method is particularly geared toward providing dose savings for the pediatric population. Methods: The scanning beam digital x-ray system uses a large-area x-ray source with 8000 focal spots in combination with a small photon-counting detector. An imaging frame is obtained by acquiring and reconstructing up to 8000 detector images, each viewing only a small portion of the patient. Regional adaptive exposure was implemented by varying the exposure of the detector images depending on the local opacity of the object. A family of phantoms ranging in size from infant to obese adult was imaged in anteroposterior view with and without adaptive exposure. The DAP delivered to each phantom was measured in each case, and noise performance was compared by generating noise arrays to represent regional noise in the images. These noise arrays were generated by dividing the image into regions of about 6 mm{sup 2}, calculating the relative noise in each region, and placing the relative noise value of each region in a one-dimensional array (noise array) sorted from highest to lowest. Dose-area product savings were calculated as the difference between the ratio of DAP with adaptive exposure to DAP without adaptive exposure. The authors modified this value by a correction factor that matches the noise arrays where relative noise is the highest to report a final dose-area product savings. Results: The average dose-area product saving across the phantom family was (42 {+-} 8)% with the highest dose-area product saving in the child-sized phantom (50%) and the lowest in the phantom mimicking an obese adult (23%). Conclusions: Phantom measurements indicate that a regional adaptive exposure method can produce large DAP savings without

  18. Role of trace elements (Zn, Sr, Fe) in bone development: energy dispersive X-ray fluorescence study of rat bone and tooth tissue.

    PubMed

    Maciejewska, Karina; Drzazga, Zofia; Kaszuba, Michał

    2014-01-01

    Osteoporosis is one of the most common debilitating disease around the world and it is more and more established among young people. There are well known recommendations for nutrition of newborns and children concerning adequate calcium and vitamin D intake in order to maintain proper bone density. Nevertheless, important role in structure and function of a healthy bone tissue is played by an integration between all constituents including elements other than Ca, like trace elements, which control vital processes in bone tissue. It is important from scientific point of view as well as prevention of bone diseases, to monitor the mineralization process considering changes of the concentration of minerals during first stage of bone formation. This work presents studies of trace element (zinc, strontium, and iron) concentration in bones and teeth of Wistar rats at the age of 7, 14, and 28 days. Energy dispersive X-ray fluorescence (EDXRF) was used to examine mandibles, skulls, femurs, tibiae, and incisors. The quantitative analysis was performed using fundamental parameters method (FP). Zn and Sr concentrations were highest for the youngest individuals and decreased with age of rats, while Fe content was stable in bone matrix for most studied bones. Our results reveal the necessity of monitoring concentration of not only major, but also minor elements, because the trace elements play special role in the first period of bone development. PMID:24615876

  19. Simple ray-tracing model for a rough surface of an ink layer including internal scattering particles printed on a light guide plate.

    PubMed

    Sekiguchi, Yoshifumi; Kaneko, Hiroki

    2016-02-01

    For simulating light guide lighting systems, we have developed a ray-tracing model for an ink layer extracting light from a light guide. The model consists of the volume and the rough surface scattering calculated on the basis of Mie theory and the facet model, respectively. The model of an ink layer was required to conserve energy for analyzing how much light loss occurs in each component in the lighting system. Though a single-scattering rough surface model with a shadowing/masking function successfully describes the scattering distribution, shadowing light violates the energy conservation law because of a lack of multiple scattering. We developed the rough surface ray-tracing model (RSRT model), which includes the multiple scattering instead of the shadowing/masking effect. We investigated the applicability of the RSRT model for an ink layer by comparing the RSRT model with recent physical and facet models. Finally, we compared the calculated and measured scattering distributions of an ink layer, applied the developed ink layer model to the lighting system, and confirmed the developed model to be valid. PMID:26836100

  20. Modeling the reflectance of the lunar regolith by a new method combining Monte Carlo Ray tracing and Hapke's model with application to Chang'E-1 IIM data.

    PubMed

    Wong, Un-Hong; Wu, Yunzhao; Wong, Hon-Cheng; Liang, Yanyan; Tang, Zesheng

    2014-01-01

    In this paper, we model the reflectance of the lunar regolith by a new method combining Monte Carlo ray tracing and Hapke's model. The existing modeling methods exploit either a radiative transfer model or a geometric optical model. However, the measured data from an Interference Imaging spectrometer (IIM) on an orbiter were affected not only by the composition of minerals but also by the environmental factors. These factors cannot be well addressed by a single model alone. Our method implemented Monte Carlo ray tracing for simulating the large-scale effects such as the reflection of topography of the lunar soil and Hapke's model for calculating the reflection intensity of the internal scattering effects of particles of the lunar soil. Therefore, both the large-scale and microscale effects are considered in our method, providing a more accurate modeling of the reflectance of the lunar regolith. Simulation results using the Lunar Soil Characterization Consortium (LSCC) data and Chang'E-1 elevation map show that our method is effective and useful. We have also applied our method to Chang'E-1 IIM data for removing the influence of lunar topography to the reflectance of the lunar soil and to generate more realistic visualizations of the lunar surface. PMID:24526892

  1. Comparison of wave propagation studies in plasmas using three-dimensional finite-difference time-domain and ray-tracing methods

    SciTech Connect

    Chaudhury, Bhaskar; Chaturvedi, Shashank

    2006-12-15

    Power-flow trajectories of electromagnetic waves through a spatially nonuniform plasma have been computed using direct solutions of Maxwell's equations using the three-dimensional finite-difference time-domain (FDTD) method. This method yields accurate information on refraction as well as absorption effects. The method can be used to compute power-flow trajectories for plasmas with arbitrarily varying density profiles, including effects due to arbitrarily shaped conducting or dielectric surfaces bounding the plasma. Furthermore, since FDTD is computationally expensive, especially for parametric studies, it is desirable to use ray tracing to estimate refraction effects. A quantitative comparison is performed between two different methods of obtaining exact and approximate solutions of Maxwell's equations in order to assess their relative utility in different situations. In the present work, we limit ourselves to a cold, collisional, unmagnetized plasma, where the response to electromagnetic waves is fully specified by a dispersion relation based on magnetoionic theory. It is shown that ray tracing in such plasmas yields accurate results only when two conditions are satisfied. Firstly, the density scale length should be long as compared to the free-space wavelength of the incident wave. Secondly, the conduction current should be small as compared to the displacement current in the medium. The second condition is one which has been identified for the first time.

  2. Modeling the Reflectance of the Lunar Regolith by a New Method Combining Monte Carlo Ray Tracing and Hapke's Model with Application to Chang'E-1 IIM Data

    PubMed Central

    Wu, Yunzhao; Tang, Zesheng

    2014-01-01

    In this paper, we model the reflectance of the lunar regolith by a new method combining Monte Carlo ray tracing and Hapke's model. The existing modeling methods exploit either a radiative transfer model or a geometric optical model. However, the measured data from an Interference Imaging spectrometer (IIM) on an orbiter were affected not only by the composition of minerals but also by the environmental factors. These factors cannot be well addressed by a single model alone. Our method implemented Monte Carlo ray tracing for simulating the large-scale effects such as the reflection of topography of the lunar soil and Hapke's model for calculating the reflection intensity of the internal scattering effects of particles of the lunar soil. Therefore, both the large-scale and microscale effects are considered in our method, providing a more accurate modeling of the reflectance of the lunar regolith. Simulation results using the Lunar Soil Characterization Consortium (LSCC) data and Chang'E-1 elevation map show that our method is effective and useful. We have also applied our method to Chang'E-1 IIM data for removing the influence of lunar topography to the reflectance of the lunar soil and to generate more realistic visualizations of the lunar surface. PMID:24526892

  3. Ray tracing of multiple transmitted/reflected/converted waves in 2-D/3-D layered anisotropic TTI media and application to crosswell traveltime tomography

    NASA Astrophysics Data System (ADS)

    Bai, Chao-Ying; Huang, Guo-Jiao; Li, Xiao-Ling; Zhou, Bing; Greenhalgh, Stewart

    2013-11-01

    To overcome the deficiency of some current grid-/cell-based ray tracing algorithms, which are only able to handle first arrivals or primary reflections (or conversions) in anisotropic media, we have extended the functionality of the multistage irregular shortest-path method to 2-D/3-D tilted transversely isotropic (TTI) media. The new approach is able to track multiple transmitted/reflected/converted arrivals composed of any kind of combinations of transmissions, reflections and mode conversions. The basic principle is that the seven parameters (five elastic parameters plus two polar angles defining the tilt of the symmetry axis) of the TTI media are sampled at primary nodes, and the group velocity values at secondary nodes are obtained by tri-linear interpolation of the primary nodes across each cell, from which the group velocities of the three wave modes (qP, qSV and qSH) are calculated. Finally, we conduct grid-/cell-based wave front expansion to trace multiple transmitted/reflected/converted arrivals from one region to the next. The results of calculations in uniform anisotropic media indicate that the numerical results agree with the analytical solutions except in directions of SV-wave triplications, at which only the lowest velocity value is selected at the singularity points by the multistage irregular shortest-path anisotropic ray tracing method. This verifies the accuracy of the methodology. Several simulation results show that the new method is able to efficiently and accurately approximate situations involving continuous velocity variations and undulating discontinuities, and that it is suitable for any combination of multiple transmitted/reflected/converted arrival tracking in TTI media of arbitrary strength and tilt. Crosshole synthetic traveltime tomographic tests have been performed, which highlight the importance of using such code when the medium is distinctly anisotropic.

  4. A Ray-Tracing Study of the Dependence of Focal Properties on Surface Figure Error for a Kirkpatrick-Baez (K-B) Mirror System

    SciTech Connect

    Xu, S.; Fischetti, R.F.

    2004-05-12

    In the last several years, Kirkpatrick-Baez (K-B) mirror systems have been extensively applied as two-dimensional x-ray focusing elements on x-ray beamlines at low emittance, third generation, synchrotron radiation facilities. The design of the two GM/CA CAT insertion device beamlines at the Advanced Photon Source at Argonne National Laboratory for macromolecular crystallography includes a K-B mirror system situated in each of the experimental stations. Ray-tracing studies have been performed using SHADOW (V2.3.2) to investigate the dependence of the focal distance on the surface figure error obtained from LTP metrology measurements. Additionally, a procedure has been developed to allow one to change the mirror focal positions to provide a beam of given dimensions at a fixed position before or after the focal position. The GM/CA CAT has been established by the National Institutes of Health's (NIH) National Institute of General Medical Sciences (NIGMS), and the National Cancer Institute (NCI) to build and operate a national user facility for crystallographic structure determination of biological macromolecules by X-ray diffraction.

  5. Adaptive nonlocal means-based regularization for statistical image reconstruction of low-dose X-ray CT

    NASA Astrophysics Data System (ADS)

    Zhang, Hao; Ma, Jianhua; Wang, Jing; Liu, Yan; Han, Hao; Li, Lihong; Moore, William; Liang, Zhengrong

    2015-03-01

    To reduce radiation dose in X-ray computed tomography (CT) imaging, one of the common strategies is to lower the milliampere-second (mAs) setting during projection data acquisition. However, this strategy would inevitably increase the projection data noise, and the resulting image by the filtered back-projection (FBP) method may suffer from excessive noise and streak artifacts. The edge-preserving nonlocal means (NLM) filtering can help to reduce the noise-induced artifacts in the FBP reconstructed image, but it sometimes cannot completely eliminate them, especially under very low-dose circumstance when the image is severely degraded. To deal with this situation, we proposed a statistical image reconstruction scheme using a NLM-based regularization, which can suppress the noise and streak artifacts more effectively. However, we noticed that using uniform filtering parameter in the NLM-based regularization was rarely optimal for the entire image. Therefore, in this study, we further developed a novel approach for designing adaptive filtering parameters by considering local characteristics of the image, and the resulting regularization is referred to as adaptive NLM-based regularization. Experimental results with physical phantom and clinical patient data validated the superiority of using the proposed adaptive NLM-regularized statistical image reconstruction method for low-dose X-ray CT, in terms of noise/streak artifacts suppression and edge/detail/contrast/texture preservation.

  6. New Ray Tracing Method to Investigate the Various Effects on Wave Propagation in Medical Scenario: An Application of Wireless Body Area Network

    PubMed Central

    Islam, M. J.; Reza, A. W.; Kausar, A. S. M. Z.; Ramiah, H.

    2014-01-01

    The advent of technology with the increasing use of wireless network has led to the development of Wireless Body Area Network (WBAN) to continuously monitor the change of physiological data in a cost efficient manner. As numerous researches on wave propagation characterization have been done in intrabody communication, this study has given emphasis on the wave propagation characterization between the control units (CUs) and wireless access point (AP) in a hospital scenario. Ray tracing is a tool to predict the rays to characterize the wave propagation. It takes huge simulation time, especially when multiple transmitters are involved to transmit physiological data in a realistic hospital environment. Therefore, this study has developed an accelerated ray tracing method based on the nearest neighbor cell and prior knowledge of intersection techniques. Beside this, Red-Black tree is used to store and provide a faster retrieval mechanism of objects in the hospital environment. To prove the superiority, detailed complexity analysis and calculations of reflection and transmission coefficients are also presented in this paper. The results show that the proposed method is about 1.51, 2.1, and 2.9 times faster than the Object Distribution Technique (ODT), Space Volumetric Partitioning (SVP), and Angular Z-Buffer (AZB) methods, respectively. To show the various effects on received power in 60 GHz frequency, few comparisons are made and it is found that on average −9.44 dBm, −8.23 dBm, and −9.27 dBm received power attenuations should be considered when human, AP, and CU move in a given hospital scenario. PMID:25133220

  7. New ray tracing method to investigate the various effects on wave propagation in medical scenario: an application of wireless body area network.

    PubMed

    Islam, M J; Reza, A W; Kausar, A S M Z; Ramiah, H

    2014-01-01

    The advent of technology with the increasing use of wireless network has led to the development of Wireless Body Area Network (WBAN) to continuously monitor the change of physiological data in a cost efficient manner. As numerous researches on wave propagation characterization have been done in intrabody communication, this study has given emphasis on the wave propagation characterization between the control units (CUs) and wireless access point (AP) in a hospital scenario. Ray tracing is a tool to predict the rays to characterize the wave propagation. It takes huge simulation time, especially when multiple transmitters are involved to transmit physiological data in a realistic hospital environment. Therefore, this study has developed an accelerated ray tracing method based on the nearest neighbor cell and prior knowledge of intersection techniques. Beside this, Red-Black tree is used to store and provide a faster retrieval mechanism of objects in the hospital environment. To prove the superiority, detailed complexity analysis and calculations of reflection and transmission coefficients are also presented in this paper. The results show that the proposed method is about 1.51, 2.1, and 2.9 times faster than the Object Distribution Technique (ODT), Space Volumetric Partitioning (SVP), and Angular Z-Buffer (AZB) methods, respectively. To show the various effects on received power in 60 GHz frequency, few comparisons are made and it is found that on average -9.44 dBm, -8.23 dBm, and -9.27 dBm received power attenuations should be considered when human, AP, and CU move in a given hospital scenario. PMID:25133220

  8. Tracing the Mass-Dependent Star Formation History of Late-Type Galaxies using X-ray Emission: Results from the CHANDRA Deep Fields

    NASA Technical Reports Server (NTRS)

    Lehmer, B.D; Brandt, W.N.; Schneider, D.P.; Steffen, A.T.; Alexander, D.M.; Bell, E.F.; Hornschemeier, A.E.; McIntosh, D.H.; Bauer, F.E.; Gilli, R.; Mainieri, V.; Silverman, J.D.; Tozzi, P.; Wolf, C.

    2008-01-01

    We report on the X-ray evolution over the last approx.9 Gyr of cosmic history (i.e., since z = 1.4) of late-type galaxy populations in the Chandra Deep Field-North and Extended Chandra Deep Field-South (CDF-N and E-CDF-S. respectively; jointly CDFs) survey fields. Our late-type galaxy sample consists of 2568 galaxies. which were identified using rest-frame optical colors and HST morphologies. We utilized X-ray stacking analyses to investigate the X-ray emission from these galaxies, emphasizing the contributions from normal galaxies that are not dominated by active galactic nuclei (AGNs). Over this redshift range, we find significant increases (factors of approx. 5-10) in the X-ray-to-optical mean luminosity ratio (L(sub x)/L(sub B)) and the X-ray-to-stellar-mass mean ratio (L(sub x)/M(sub *)) for galaxy populations selected by L(sub B) and M(sub *), respectively. When analyzing galaxy samples selected via SFR, we find that the mean X-ray-to-SFR ratio (L(sub x)/SFR) is consistent with being constant over the entire redshift range for galaxies with SFR = 1-100 Solar Mass/yr, thus demonstrating that X-ray emission can be used as a robust indicator of star-formation activity out to z approx. 1.4. We find that the star-formation activity (as traced by X-ray luminosity) per unit stellar mass in a given redshift bin increases with decreasing stellar mass over the redshift range z = 0.2-1, which is consistent with previous studies of how star-formation activity depends on stellar mass. Finally, we extend our X-ray analyses to Lyman break galaxies at z approx. 3 and estimate that L(sub x)/L(sub B) at z approx. 3 is similar to its value at z = 1.4.

  9. Role of x-ray-induced transcripts in adaptive responses following x-rays. Progress report, Year 2

    SciTech Connect

    Not Available

    1993-09-01

    I will describe our recent data in which we have extracted and purified a sufficient amount of RNA from primed and unprimed U1-Mel cells to begin the search for new genes which are modulated by priming or high dose irradiation during the establishment and/or challenge of adapted cells, respectively. Gene transcripts which are altered during ASRs now include alterations in xip5 (a gene with homology to human growth hormone), xipl2 (a gene with homology to human angiogenesis factor and a gene which may be involved in apoptosis due to its possible RNase activity), cyclin A (which is altered in primed cells only after a high dose of ionizing radiation), cyclin B (which is also altered in a similar manner as cyclin A), p53 (a tumor suppressor gene involved in cell division control in G{sub 1} following ionizing radiation), and glutathionine S transferase-pi (a gene product which has been demonstrated to be involved in DNA repair and redox cycling). In contrast, the remaining xip CDNA clones [i.e., xip1-4,6-11, which were isolated following high dose ionizing radiation exposure to human U1-Mel cells], Prad-1 (a gene involved in cell cycle controlling events at the G{sub 1} portion of the cell cycle), 36B4 (a gene involved in homeostasis), and cdc2 (a gene involved in the regulation of the S-phase portion of the cell cycle), were not altered following ionizing radiation, either during the establishment or challenge of adapted human cells.

  10. Kinetic Boltzmann approach adapted for modeling highly ionized matter created by x-ray irradiation of a solid

    NASA Astrophysics Data System (ADS)

    Ziaja, Beata; Saxena, Vikrant; Son, Sang-Kil; Medvedev, Nikita; Barbrel, Benjamin; Woloncewicz, Bianca; Stransky, Michal

    2016-05-01

    We report on the kinetic Boltzmann approach adapted for simulations of highly ionized matter created from a solid by its x-ray irradiation. X rays can excite inner-shell electrons, which leads to the creation of deeply lying core holes. Their relaxation, especially in heavier elements, can take complicated paths, leading to a large number of active configurations. Their number can be so large that solving the set of respective evolution equations becomes computationally inefficient and another modeling approach should be used instead. To circumvent this complexity, the commonly used continuum models employ a superconfiguration scheme. Here, we propose an alternative approach which still uses "true" atomic configurations but limits their number by restricting the sample relaxation to the predominant relaxation paths. We test its reliability, performing respective calculations for a bulk material consisting of light atoms and comparing the results with a full calculation including all relaxation paths. Prospective application for heavy elements is discussed.

  11. Kinetic Boltzmann approach adapted for modeling highly ionized matter created by x-ray irradiation of a solid.

    PubMed

    Ziaja, Beata; Saxena, Vikrant; Son, Sang-Kil; Medvedev, Nikita; Barbrel, Benjamin; Woloncewicz, Bianca; Stransky, Michal

    2016-05-01

    We report on the kinetic Boltzmann approach adapted for simulations of highly ionized matter created from a solid by its x-ray irradiation. X rays can excite inner-shell electrons, which leads to the creation of deeply lying core holes. Their relaxation, especially in heavier elements, can take complicated paths, leading to a large number of active configurations. Their number can be so large that solving the set of respective evolution equations becomes computationally inefficient and another modeling approach should be used instead. To circumvent this complexity, the commonly used continuum models employ a superconfiguration scheme. Here, we propose an alternative approach which still uses "true" atomic configurations but limits their number by restricting the sample relaxation to the predominant relaxation paths. We test its reliability, performing respective calculations for a bulk material consisting of light atoms and comparing the results with a full calculation including all relaxation paths. Prospective application for heavy elements is discussed. PMID:27300998

  12. The interaction between gravity waves and solar tides: Results from 4-D ray tracing coupled to a linear tidal model

    NASA Astrophysics Data System (ADS)

    Ribstein, B.; Achatz, U.; Senf, F.

    2015-08-01

    The interaction between solar tides (STs) and gravity waves (GWs) is studied via the coupling of a three-dimensional ray tracer model and a linear tidal model. The ray tracer model describes GW dynamics on a spatially and time-dependent background formed by a monthly mean climatology and STs. It does not suffer from typical simplifications of conventional GW parameterizations where horizontal GW propagation and the effects of horizontal background gradients on GW dynamics are neglected. The ray tracer model uses a variant of Wentzel-Kramers-Brillouin (WKB) theory where a spectral description in position wave number space is helping to avoid numerical instabilities otherwise likely to occur in caustic-like situations. The tidal model has been obtained by linearization of the primitive equations about a monthly mean, allowing for stationary planetary waves. The communication between ray tracer model and tidal model is facilitated using latitude- and altitude-dependent coefficients, named Rayleigh friction and Newtonian relaxation, and obtained from regressing GW momentum and buoyancy fluxes against the STs and their tendencies. These coefficients are calculated by the ray tracer model and then implemented into the tidal model. An iterative procedure updates successively the GW fields and the tidal fields until convergence is reached. Notwithstanding the simplicity of the employed GW source, many aspects of observed tidal dynamics are reproduced. It is shown that the conventional "single-column" approximation leads to significantly overestimated GW fluxes and hence underestimated ST amplitudes, pointing at a sensitive issue of GW parameterizations in general.

  13. Big Bangs in Galaxy Clusters: Using X-ray Temperature Maps to Trace Merger Histories in Clusters with Radio Halos/Relics

    NASA Astrophysics Data System (ADS)

    Burns, Jack O.; Datta, Abhirup; Hallman, Eric J.

    2016-06-01

    Galaxy clusters are assembled through large and small mergers which are the most energetic events ("bangs") since the Big Bang. Cluster mergers "stir" the intracluster medium (ICM) creating shocks and turbulence which are illuminated by ~Mpc-sized radio features called relics and halos. These shocks heat the ICM and are detected in x-rays via thermal emission. Disturbed morphologies in x-ray surface brightness and temperatures are direct evidence for cluster mergers. In the radio, relics (in the outskirts of the clusters) and halos (located near the cluster core) are also clear signposts of recent mergers. Our recent ENZO cosmological simulations suggest that around a merger event, radio emission peaks very sharply (and briefly) while the x-ray emission rises and decays slowly. Hence, a sample of galaxy clusters that shows both luminous x-ray emission and radio relics/halos are good candidates for very recent mergers. We are in the early stages of analyzing a unique sample of 48 galaxy clusters with (i) known radio relics and/or halos and (ii) significant archival x-ray observations (>50 ksec) from Chandra and/or XMM. We have developed a new x-ray data analysis pipeline, implemented on parallel processor supercomputers, to create x-ray surface brightness, high fidelity temperature, and pressure maps of these clusters in order to study merging activity. The temperature maps are made using three different map-making techniques: Weighted Voronoi Tessellation, Adaptive Circular Binning, and Contour Binning. In this talk, we will show preliminary results for several clusters, including Abell 2744 and the Bullet cluster. This work is supported by NASA ADAP grant NNX15AE17G.

  14. Fermi-LAT Observations of High- and Intermediate-velocity Clouds: Tracing Cosmic Rays in the Halo of the Milky Way

    NASA Astrophysics Data System (ADS)

    Tibaldo, L.; Digel, S. W.; Casandjian, J. M.; Franckowiak, A.; Grenier, I. A.; Jóhannesson, G.; Marshall, D. J.; Moskalenko, I. V.; Negro, M.; Orlando, E.; Porter, T. A.; Reimer, O.; Strong, A. W.

    2015-07-01

    It is widely accepted that cosmic rays (CRs) up to at least PeV energies are Galactic in origin. Accelerated particles are injected into the interstellar medium where they propagate to the farthest reaches of the Milky Way, including a surrounding halo. The composition of CRs coming to the solar system can be measured directly and has been used to infer the details of CR propagation that are extrapolated to the whole Galaxy. In contrast, indirect methods, such as observations of γ-ray emission from CR interactions with interstellar gas, have been employed to directly probe the CR densities in distant locations throughout the Galactic plane. In this article we use 73 months of data from the Fermi Large Area Telescope in the energy range between 300 MeV and 10 GeV to search for γ-ray emission produced by CR interactions in several high- and intermediate-velocity clouds (IVCs) located at up to ∼7 kpc above the Galactic plane. We achieve the first detection of IVCs in γ rays and set upper limits on the emission from the remaining targets, thereby tracing the distribution of CR nuclei in the halo for the first time. We find that the γ-ray emissivity per H atom decreases with increasing distance from the plane at 97.5% confidence level. This corroborates the notion that CRs at the relevant energies originate in the Galactic disk. The emissivity of the upper intermediate-velocity Arch hints at a 50% decline of CR densities within 2 kpc from the plane. We compare our results to predictions of CR propagation models.

  15. Using the Long-term Optical/Infrared Color Variability to Trace the Gamma-ray Jet "State"

    NASA Astrophysics Data System (ADS)

    Isler, Jedidah; Urry, C. Megan; Bailyn, Charles D.; Coppi, Paolo S.; Hasan, Imran; MacPherson, Emily; Buxton, Michelle

    2016-04-01

    We have undertaken a 7-year, multiwavelength program to observe a sample of blazars in various Fermi gamma-ray states, using the Small and Medium Aperture Research Telescope System (SMARTS) 1.3m + ANDICAM instrument in Cerro Tololo, Chile. We present near-daily optical and infrared (OIR) color variability diagrams of these sources and compare the OIR flux and color to the Fermi gamma-ray flux on similar cadence. We then analyze the color variability properties on short and long timescales, as compared to the length of an average gamma-ray flare, to better constrain the physical mechanisms responsible for the variability properties that we observe. From this long-term observational data, we develop a schematic representation of the possible color variability behaviors in blazars and how it is related to the thermal disk and non-thermal jet contributions in both Flat Spectrum Radio Quasars and BL Lac objects.

  16. Tracing a Z-track in the M 31 X-ray binary RX J0042.6+4115

    NASA Astrophysics Data System (ADS)

    Barnard, R.; Kolb, U.; Osborne, J. P.

    2003-12-01

    Four XMM-Newton observations of the core of M 31, spaced at 6 month intervals, show that the brightest point X-ray source, RX J0042.6+4115, has a 0.4-10 keV luminosity of ~ 5x 1038 erg s-1, and exhibits significant variability in intensity and X-ray spectrum over a time scale of ~ 100 s including hard flares; such behaviour is only observed in Z-sources and transient black hole binaries in our Galaxy. The lightcurves, X-ray spectra and hardness-intensity data from the four XMM-Newton observations all strongly suggest that it is a Z-source, bringing the total number of known Z-sources to nine.

  17. Mixed-level optical simulations of light-emitting diodes based on a combination of rigorous electromagnetic solvers and Monte Carlo ray-tracing methods

    NASA Astrophysics Data System (ADS)

    Bahl, Mayank; Zhou, Gui-Rong; Heller, Evan; Cassarly, William; Jiang, Mingming; Scarmozzino, Robert; Gregory, G. Groot; Herrmann, Daniel

    2015-04-01

    Over the last two decades, extensive research has been done to improve light-emitting diodes (LEDs) designs. Increasingly complex designs have necessitated the use of computational simulations which have provided numerous insights for improving LED performance. Depending upon the focus of the design and the scale of the problem, simulations are carried out using rigorous electromagnetic (EM) wave optics-based techniques, such as finite-difference time-domain and rigorous coupled wave analysis, or through ray optics-based techniques such as Monte Carlo ray-tracing (RT). The former are typically used for modeling nanostructures on the LED die, and the latter for modeling encapsulating structures, die placement, back-reflection, and phosphor downconversion. This paper presents the use of a mixed-level simulation approach that unifies the use of EM wave-level and ray-level tools. This approach uses rigorous EM wave-based tools to characterize the nanostructured die and generates both a bidirectional scattering distribution function and a far-field angular intensity distribution. These characteristics are then incorporated into the RT simulator to obtain the overall performance. Such a mixed-level approach allows for comprehensive modeling of the optical characteristic of LEDs, including polarization effects, and can potentially lead to a more accurate performance than that from individual modeling tools alone.

  18. Modelling of waves propagation on irregular surfaces using ray tracing and GTD approaches: Application to head waves simulation in TOFD inspections for NDT

    NASA Astrophysics Data System (ADS)

    Ferrand, Adrien; Darmon, Michel; Chatillon, Sylvain; Deschamps, Marc

    2014-04-01

    The Time of Flight Diffraction (TOFD) technique is a classical ultrasonic method used in ultrasonic non-destructive evaluation, which allows a precise positioning and a quantitative size evaluation of cracks in the inspected material. Among the typical phenomena arising in the current TOFD inspection, the so-called "head wave" is the first contribution reaching the receiver. The head wave propagation on a planar interface is well known and identified as a critical refraction taking place on the material surface. On irregular surfaces, it has been shown that the head wave results from the melting of surface and bulk waves mechanisms and that surface irregularities are responsible for numerous diffractions of the incident head wave. To simulate such behaviour, a model has been developed using a ray tracing technique based on time of flight minimization (generalized Fermat's principle). It enables the calculation of the ray path and the corresponding time of flight of all waves propagating in the material, including the head wave. To obtain a complete propagation model for these waves (both trajectory and amplitude), the integration of Geometrical Theory of Diffraction (GTD) models is currently performed by coupling them with the ray-based approach discussed above.

  19. Naked-eye optical flash from gamma-ray burst 080319B: Tracing the decaying neutrons in the outflow

    SciTech Connect

    Fan Yizhong; Zhang Bing; Wei Daming

    2009-01-15

    For an unsteady baryonic gamma-ray burst (GRB) outflow, the fast and slow proton shells collide with each other and produce energetic soft gamma-ray emission. If the outflow has a significant neutron component, the ultrarelativistic neutrons initially expand freely until decaying at a larger radius. The late-time proton shells ejected from the GRB central engine, after powering the regular internal shocks, will sweep these {beta}-decay products and give rise to very bright UV/optical emission. The naked-eye optical flash from GRB 080319B, an energetic explosion in the distant Universe, can be well explained in this way.

  20. Analysis of trace elements during different developmental stages of somatic embryogenesis in Plantago ovata Forssk using energy dispersive X-ray fluorescence.

    PubMed

    Saha, Priyanka; Raychaudhuri, Sarmistha Sen; Sudarshan, Mathummal; Chakraborty, Anindita

    2010-06-01

    Energy dispersive X-ray fluorescence (ED-XRF) technique has been used for the determination of trace element profile during different developmental stages of somatic embryogenic callus of an economically important medicinal plant, Plantago ovata Forssk. Somatic embryogenesis is a plant tissue culture-based technique, which is used for plant regeneration and crop improvement. In the present investigation, elemental content was analysed using ED-XRF technique during different developmental stages and also determine the effect of additives--casein hydrolysate and coconut water on the trace elemental profile of embryogenic callus tissue of P. ovata. Subsequent experiments showed significant alteration in the concentration of K, Ca, Mn, Fe, Zn, Cu, Br, and Sr in both the embryogenic and non-embryogenic callus. Higher K, Ca, Fe, Cu, and Zn accumulation was in embryogenic tissue stage compared to other stages, suggesting these elements are crucial for successful embryogenesis. The results suggest that this information could be useful for formulating a media for in vitro embryo induction of P. ovata. PMID:19696971

  1. Rapid quantitative determination of major and trace elements in silicate rocks and soils employing fused glass discs using wavelength dispersive X-ray fluorescence spectrometry

    NASA Astrophysics Data System (ADS)

    Krishna, A. Keshav; Khanna, Tarun C.; Mohan, K. Rama

    2016-08-01

    This paper introduces a calibration procedure and provides the data achieved for accuracy, precision, reproducibility and the detection limits for major (Si, Al, Fe, Mn, Mg, Ca, Na, K, Ti, P) and trace (Ba, Cr, Cu, Hf, La, Nb, Ni, Pb, Rb, Sr, Ta, Th, U, Y, Zn, Zr) elements in the routine analysis of geological and environmental samples. Forty-two rock and soil reference materials were used to calibrate and evaluate the analytical method using a sequential wavelength dispersive X-ray fluorescence spectrometer. Samples were prepared as fused glass discs and analysis performed with a total measuring time of thirty-one minutes. Another set of twelve independent reference materials were analyzed for the evaluation of accuracy. The detection limits and accuracy obtained for the trace elements (1-2 mg/kg) are adequate both for geochemical exploration and environmental studies. The fitness for purpose of the results was also evaluated by the quality criteria test proposed by the International Global Geochemical Mapping Program (IGCP) from which it can be deduced that the method is adequate considering geochemical mapping application and accuracy obtained is within the expected interval of certified values in most cases.

  2. Correction of the spectral calibration of the Joint European Torus core light detecting and ranging Thomson scattering diagnostic using ray tracing.

    PubMed

    Hawke, J; Scannell, R; Maslov, M; Migozzi, J B

    2013-10-01

    This work isolated the cause of the observed discrepancy between the electron temperature (T(e)) measurements before and after the JET Core LIDAR Thomson Scattering (TS) diagnostic was upgraded. In the upgrade process, stray light filters positioned just before the detectors were removed from the system. Modelling showed that the shift imposed on the stray light filters transmission functions due to the variations in the incidence angles of the collected photons impacted plasma measurements. To correct for this identified source of error, correction factors were developed using ray tracing models for the calibration and operational states of the diagnostic. The application of these correction factors resulted in an increase in the observed T(e), resulting in the partial if not complete removal of the observed discrepancy in the measured T(e) between the JET core LIDAR TS diagnostic, High Resolution Thomson Scattering, and the Electron Cyclotron Emission diagnostics. PMID:24188274

  3. Correction of the spectral calibration of the Joint European Torus core light detecting and ranging Thomson scattering diagnostic using ray tracing

    SciTech Connect

    Hawke, J.; Scannell, R.; Maslov, M.; Migozzi, J. B.; Collaboration: JET-EFDA Contributors

    2013-10-15

    This work isolated the cause of the observed discrepancy between the electron temperature (T{sub e}) measurements before and after the JET Core LIDAR Thomson Scattering (TS) diagnostic was upgraded. In the upgrade process, stray light filters positioned just before the detectors were removed from the system. Modelling showed that the shift imposed on the stray light filters transmission functions due to the variations in the incidence angles of the collected photons impacted plasma measurements. To correct for this identified source of error, correction factors were developed using ray tracing models for the calibration and operational states of the diagnostic. The application of these correction factors resulted in an increase in the observed T{sub e}, resulting in the partial if not complete removal of the observed discrepancy in the measured T{sub e} between the JET core LIDAR TS diagnostic, High Resolution Thomson Scattering, and the Electron Cyclotron Emission diagnostics.

  4. Evaluation of light extraction efficiency for the light-emitting diodes based on the transfer matrix formalism and ray-tracing method

    NASA Astrophysics Data System (ADS)

    Pingbo, An; Li, Wang; Hongxi, Lu; Zhiguo, Yu; Lei, Liu; Xin, Xi; Lixia, Zhao; Junxi, Wang; Jinmin, Li

    2016-06-01

    The internal quantum efficiency (IQE) of the light-emitting diodes can be calculated by the ratio of the external quantum efficiency (EQE) and the light extraction efficiency (LEE). The EQE can be measured experimentally, but the LEE is difficult to calculate due to the complicated LED structures. In this work, a model was established to calculate the LEE by combining the transfer matrix formalism and an in-plane ray tracing method. With the calculated LEE, the IQE was determined and made a good agreement with that obtained by the ABC model and temperature-dependent photoluminescence method. The proposed method makes the determination of the IQE more practical and conventional. Project supported by the National Natural Science Foundation of China (Nos.11574306, 61334009), the China International Science and Technology Cooperation Program (No. 2014DFG62280), and the National High Technology Program of China (No. 2015AA03A101).

  5. Portable x-ray fluorescence for assessing trace elements in rice and rice products: Comparison with inductively coupled plasma-mass spectrometry.

    PubMed

    Fleming, David E B; Foran, Kelly A; Kim, Jong Sung; Guernsey, Judy R

    2015-10-01

    Portable x-ray fluorescence (XRF) was investigated as a means of assessing trace elements in rice and rice products. Using five measurement trials of 180 s real time, portable XRF was first used to detect arsenic (As), manganese (Mn), iron (Fe), nickel (Ni), copper (Cu), and zinc (Zn) in a variety of rice samples. The same samples were then microwave-digested and used to determine elemental concentrations using inductively coupled plasma-mass spectrometry (ICP-MS). The concentrations of As, Mn, Fe, Cu, and Zn determined by ICP-MS were found to be consistent with other recent studies involving various types of rice and rice products. When assessing for As, Mn, Fe, Cu, and Zn, comparison of results between XRF amplitude and ICP-MS concentration (wet weight) demonstrated a linear relationship with a significant correlation. A significant correlation between XRF amplitude and ICP-MS concentration was not found when assessing for Ni. PMID:26203871

  6. The extended Beer-Lambert theory for ray tracing modeling of LED chip-scaled packaging application with multiple luminescence materials

    NASA Astrophysics Data System (ADS)

    Yuan, Cadmus C. A.

    2015-12-01

    Optical ray tracing modeling applied Beer-Lambert method in the single luminescence material system to model the white light pattern from blue LED light source. This paper extends such algorithm to a mixed multiple luminescence material system by introducing the equivalent excitation and emission spectrum of individual luminescence materials. The quantum efficiency numbers of individual material and self-absorption of the multiple luminescence material system are considered as well. By this combination, researchers are able to model the luminescence characteristics of LED chip-scaled packaging (CSP), which provides simple process steps and the freedom of the luminescence material geometrical dimension. The method will be first validated by the experimental results. Afterward, a further parametric investigation has been then conducted.

  7. X-ray absorption fine structure combined with fluorescence spectrometry for monitoring trace amounts of lead adsorption in the environmental conditions.

    PubMed

    Izumi, Yasuo; Kiyotaki, Fumitaka; Minato, Taketoshi; Seida, Yoshimi

    2002-08-01

    The local structure of trace amounts of lead in an adsorbent matrix that contains a high concentration of iron and magnesium (Mg6Fe2(OH)16(CO3) x 3H2O) was successfully monitored by means of X-ray absorption fine structure spectroscopy combined with fluorescence spectrometry. A eutectic mixture of PbCO3 and Pb(OH)2 coagulated when Pb2+ was adsorbed from a 1.0 ppm aqueous solution, and in contrast, the major species was ion-exchanged Pb2+ in the case of adsorption from a 100 ppb aqueous solution. The difference was ascribed to the balance between the precipitation equilibrium for coagulation and the rate of the ion exchange reaction with surface hydroxyl groups. PMID:12175171

  8. Ray Tracing Technique for Modeling of Power Deposition into Electron Cyclotron Resonance Discharge of a Simple Mirror Trap with Longitudinal Launch of Microwave Radiation

    SciTech Connect

    Gospodchikov, E.D.; Smolyakova, O.B.; Suvorov, E.V.

    2005-01-15

    The ray-tracing procedure for modeling the power deposition into electron cyclotron resonance (ECR) discharge in an axisymmetric mirror trap with longitudinal launch of microwave power is presented. To deal with cyclotron absorption for normal waves of magnetized plasma propagating nearly along the magnetic field in the vicinity of electron cyclotron frequency approximate dispersion relation has been derived using Stix components for microwave electric field. Calculations have been performed for parameters corresponding to ECR multicharge ion (MCI) source (IAP RAS) as example. It is shown that the efficient power deposition into ECR discharge within single pass of radiation through the plasma column may be provided under conditions that parasitic cyclotron resonance (before the plug) is outside the plasma volume and the electron density in the vicinity of the main resonance is undercritical. This is in a qualitative agreement with experimental results.

  9. [Determination of major, minor and trace elements in soils by polarized energy X-ray fluorescence spectrometry and the application to vertical distribution characteristics of soil organic carbon].

    PubMed

    Shen, Ya-Ting

    2012-11-01

    It is difficult to get accurate, precise and reliable analytical data when using X-ray fluorescence spectrometry (XRF) to determinate sulfur in geological sample. The possible ways to improve sulfur determination accuracy are discussed. Sulfur, and the major, minor and trace elements in soils were determined by polarization energy dispersion XRF (EDXRF) spectrometry and the element profiles and vertical distribution were obtained. Based on this, replacement of two short-term vegetation soil profiles was studied. Significant correlations among the vertical distribution of soil organic carbon content (TOC), organic carbon stable carbon isotopes (delta13C) and several elements were found. The study showed that the EDXRF method can be well applied to element soil geochemical cycle and carbon cycle researches. PMID:23387191

  10. Wavelength-dispersive total-reflection X-ray fluorescence with an efficient Johansson spectrometer and an undulator X-ray source: detection of 10-16 g-level trace metals.

    PubMed

    Sakurai, Kenji; Eba, Hiromi; Inoue, Katsuaki; Yagi, Naoto

    2002-09-01

    The present paper reports significant enhancement of the detection power for total-reflection X-ray fluorescence (TXRF). The employment of an efficient wavelength-dispersive spectrometer rather than a conventional Si(Li) detector, as well as the use of a quasi-monochromatic undulator X-ray source, completely changed the quality of X-ray florescence spectra. The energy resolution is 20 times better, which effectively contributes to reducing the low-energy tail of the scattering background and to separating neighboring X-ray florescence peaks. Another advantage is its capability with respect to high-counting-rate measurements, which ensure the detection of weak signals from trace materials. The absolute and relative detection limit for nickel are 3.1 x 10(-16) g and 3.1 ppt (pg/g) for a 0.1-microL droplet of pure water, respectively, which is nearly 50 times better than the current best data achieved by conventional energy-dispersive TXRF using a Si(Li) detector system. PMID:12236366

  11. Role of x-ray-induced transcripts in adaptive responses following x-rays. Progress report, year 1

    SciTech Connect

    Boothman, D.A.

    1992-09-01

    Potentially lethal damage repair (PLDR) and sublethal damage repair, may be the same manifestations of a series of common enzymatic steps. PLDR, has two distinct phases based upon DNA lesion repair and survival recovery studies. The first phase of PLDR occurs very quickly (t{sub {1/2}}:2--20 mins) to increase the survival of X-irradiated cells by mending the vast array of DNA lesions created by ionizing radiation. The second slower phase of PLDR proceeds much later (i.e., >1--2 hrs) following X-irradiation, during which the remaining double-stranded DNA breaks are completely repaired. This second phase of repair closely corresponds to the restructuring of gross chromosomal damage, and can be partially blocked in some human cells by inhibiting protein synthesis. This slower phase of PLDR correlated with a rapid decline in X-ray-induced transformation of normal cells. The fast component of PLDR may be due to constitutively synthesized DNA ligases, topoisomerases, or polymerases, which act immediately to repair damaged, DNA. In contrast, the slow phase of PLDR in human cells may require the induction of specific genes and gene product`s involved in the repair of potentially lethal or carcinogenic DNA lesions. Induced gene products (i.e., proteins) specifically synthesized in response to physiological doses of ionizing radiation in radioresistant human melanoma (U1-Mel) cells, and in a variety of other human normal and cancer-prone cells, were identified using two-dimensional gel electrophoresis. We identified and partially characterized ten proteins synthesized by U1-Mel cells. The synthesis of eight of these proteins were specifically induced by ionizing radiation and two proteins were repressed Neither heat shock, UV-irradiation, nor bifunctional alkylating agent treatments resulted in the induction of these proteins. The expression of one protein, XIP269, correlated very well with PLDR capacity.

  12. Measurement of trace elements in KH/sub 2/PO/sub 4/ crystals by x-ray fluorescence spectrometry

    SciTech Connect

    Ryon, R.W.; Duewer, T.I.

    1981-02-01

    A non-destructive method is described for the quantitative measurement of impurities in KDP (KH/sub 2/PO/sub 4/) crystals. Part per million concentrations of impurities can be determined with good accuracy in about one hour of instrument time. An energy dispersive x-ray spectrometer is used. Both the crystals and the solutions from which they are grown may be analyzed.

  13. Diffuse cosmic gamma rays at 1-20 MeV: a trace of the dark matter?

    SciTech Connect

    Lawson, Kyle; Zhitnitsky, Ariel R E-mail: arz@phas.ubc.ca

    2008-01-15

    Several independent observations of the galactic core suggest hitherto unexplained sources of energy. The most well known case is the 511 keV line which has proven very difficult to explain with conventional astrophysical positron sources. A similar, but less well known mystery is the excess of gamma ray photons detected by COMPTEL across a broad energy range {approx}1-20 MeV. Such photons are found to be very difficult to produce via known astrophysical sources. We show in this work that dark matter in the form of dense antimatter droplets provides a natural explanation for the observed flux of gamma rays in the {approx}1-20 MeV range. We argue that such photons must always accompany the 511 keV line as they are produced by the same mechanism within our framework. We calculate the spectrum and intensity of the {approx}1-20 MeV gamma rays, and find it to be consistent with the COMPTEL data.

  14. Determination of trace elements in Syrian medicinal plants and their infusions by energy dispersive X-ray fluorescence and total reflection X-ray fluorescence spectrometry

    NASA Astrophysics Data System (ADS)

    Khuder, A.; Sawan, M. Kh.; Karjou, J.; Razouk, A. K.

    2009-07-01

    X-ray fluorescence (XRF) and total-reflection X-ray fluorescence (TXRF) techniques suited well for a multi-element determination of K, Ca, Mn, Fe, Cu, Zn, Rb, and Sr in some Syrian medicinal plant species. The accuracy and the precision of both techniques were verified by analyzing the Standard Reference Materials (SRM) peach-1547 and apple leaves-1515. A good agreement between the measured concentrations of the previously mentioned elements and the certified values were obtained with errors less than 10.7% for TXRF and 15.8% for XRF. The determination of Br was acceptable only by XRF with an error less than 24%. Furthermore, the XRF method showed a very good applicability for the determination of K, Ca, Mn, Fe, Cu, Zn, Rb, Sr, and Br in infusions of different Syrian medicinal plant species, namely anise ( Anisum vulgare), licorice root ( Glycyrrhiza glabra), and white wormwood ( Artemisia herba-alba).

  15. Radiation heat transfer model using Monte Carlo ray tracing method on hierarchical ortho-Cartesian meshes and non-uniform rational basis spline surfaces for description of boundaries

    NASA Astrophysics Data System (ADS)

    Kuczyński, Paweł; Białecki, Ryszard

    2014-06-01

    The paper deals with a solution of radiation heat transfer problems in enclosures filled with nonparticipating medium using ray tracing on hierarchical ortho-Cartesian meshes. The idea behind the approach is that radiative heat transfer problems can be solved on much coarser grids than their counterparts from computational fluid dynamics (CFD). The resulting code is designed as an add-on to OpenFOAM, an open-source CFD program. Ortho-Cartesian mesh involving boundary elements is created based upon CFD mesh. Parametric non-uniform rational basis spline (NURBS) surfaces are used to define boundaries of the enclosure, allowing for dealing with domains of complex shapes. Algorithm for determining random, uniformly distributed locations of rays leaving NURBS surfaces is described. The paper presents results of test cases assuming gray diffusive walls. In the current version of the model the radiation is not absorbed within gases. However, the ultimate aim of the work is to upgrade the functionality of the model, to problems in absorbing, emitting and scattering medium projecting iteratively the results of radiative analysis on CFD mesh and CFD solution on radiative mesh.

  16. Calculation of the radiation forces on a microsphere in the evanescent field of an optical nanofiber by ray tracing.

    PubMed

    Zhang, B; Luo, J X; Liu, Z L; Wu, F P

    2016-02-20

    We use ray optics to calculate the radiation forces on a dielectric microsphere in the evanescent field of an optical nanofiber. We theoretically demonstrate that the gradient force may attract the microsphere onto the fiber surface. The scattering force may transport the microsphere along the fiber and in the light propagating direction. The impact of the sphere-fiber distance, sphere radius, and fiber radius on the scattering and gradient forces are investigated. The radius of nanofiber can be optimized for particle transportation. PMID:26906604

  17. Determination of selenium at trace levels in geologic materials by energy-dispersive X-ray fluorescence spectrometry

    USGS Publications Warehouse

    Wahlberg, J.S.

    1981-01-01

    Low levels of selenium (0.1-500 ppm) in both organic and inorganic geologic materials can be semiquantitatively measured by isolating Se as a thin film for presentation to an energy-dispersive X-ray fluorescence spectrometer. Suitably pulverized samples are first digested by fusing with a mixture of Na2CO3 and Na2O2. The fusion cake is dissolved in distilled water, buffered with NH4Cl, and filtered to remove Si and the R2O3 group. A carrier solution of Na2TeO4, plus solid KI, hydrazine sulfate and Na2SO3, is added to the filtrate. The solution is then vacuum-filtered through a 0.45-??m pore-size filter disc. The filter, with the thin film of precipitate, is supported between two sheets of Mylar?? film for analysis. Good agreement is shown between data reported in this study and literature values reported by epithermal neutron-activation analysis and spectrofluorimetry. The method can be made quantitative by utilizing a secondary precipitation to assure complete recovery of the Se. The X-ray method offers fast turn-around time and a reasonably high production rate. ?? 1981.

  18. Analysis of platinum and trace metals in treated glioma rat cells by X-ray fluorescence emission.

    PubMed

    Gil, Silvia; Carmona, Asunción; Martínez-Criado, Gema; León, Alberto; Prezado, Yolanda; Sabés, Manel

    2015-02-01

    So far, reports in the literature indicate a superior effectiveness of anticancer treatments using drug liposome-encapsulated. In this work, the influence of cisplatin associated with lipid vesicles (liposomes) is studied. Possible induced changes in the elemental composition, distribution, and concentration inside F98 glioma cells are investigated by synchrotron X-ray fluorescence (SXRF) and particle-induced X-ray emission (PIXE), combined with backscattering spectrometry (BS). SXRF at nanometer spatial resolution provides information on the two-dimension variation of elements inside the cells, while PIXE and BS allow the determination of the elemental concentration at μg g(-1) level. In comparison with dead cells, the elemental analysis shows that both platinum and zinc contents decrease in surviving samples. Moreover, higher levels of calcium and lower levels of potassium are revealed in dead cells, especially in those treated with liposomal cisplatin. These findings would mean that liposome-treated cells died mainly by apoptosis. Although further analyses are still necessary, the results presented in this work suggest that the lipid vesicles could provide, thus, a methodology for an effective platinum administration. PMID:25216793

  19. Solar radiation reflectors adapted to track the incident rays of the sun

    SciTech Connect

    Sintes, J.F.

    1981-06-23

    A tracking solar radiation structure is described which includes a main support column and a plurality of secondary structures mounted on the main column with a series of reflecting surfaces on the secondary structures. The bearing column extends in an inclined plane and is rotatable about its axis. The secondary reflector structures are articulatedly connected to the bearing column and adapted to swing with respect to the bearing column around the axis of articulation. The bearing column is supported at its lower end on an appropriate base and at a section above its midpoint by a substantially flat structure perpendicular to the axis of rotation of the bearing column.

  20. Using portable X-ray fluorescence spectrometry and GIS to assess environmental risk and identify sources of trace metals in soils of peri-urban areas in the Yangtze Delta region, China.

    PubMed

    Ran, Jing; Wang, Dejian; Wang, Can; Zhang, Gang; Yao, Lipeng

    2014-08-01

    Portable X-ray fluorescence (PXRF) spectrometry may be very suitable for a fast and effective environmental assessment and source identification of trace metals in soils. In this study, topsoils (0-10 cm) at 139 sites were in situ scanned for total trace metals (Cr, Cu, Ni, Pb and Zn) and arsenic concentrations by PXRF in a typical town in Yangtze Delta region of Jiangsu province, China. To validate the utility of PXRF, 53 samples were collected from the scanning sites for the determination of selected trace metals using conventional methods. Based on trace metal concentrations detected by in situ PXRF, the contamination extent and sources of trace metals were studied via geo-accumulation index, multivariate analysis and geostatistics. The trace metal concentrations determined by PXRF were similar to those obtained via conventional chemical analysis. The median concentration of As, Cr, Cu, Ni, Pb and Zn in soils were 10.8, 56.4, 41.5, 43.5, 33.5, and 77.7 mg kg(-1), respectively. The distribution patterns of Cr, Cu, Ni, Pb, and Zn were mostly affected by anthropogenic sources, while As was mainly derived from lithogenic sources. Overall, PXRF has been successfully applied to contamination assessment and source identification of trace metals in soils. PMID:24875935

  1. Trace element analyses of spheres from the melt zone of the Greenland ice CAP using synchrotron X ray fluorescence

    NASA Astrophysics Data System (ADS)

    Chevallier, P.; Wang, J.; Jehanno, C.; Maurette, M.; Sutton, S. R.

    1987-03-01

    Synchrotron X ray fluorescence spectra of unpolished iron and chondritic spheres extracted from sediments collected on the melt zone of the Greenland ice cap allow the analysis of Ni, Cu, Zn, Ga, Ge, Pb, and Se with minimum detection limits on the order of several parts per million. All detected elements are depleted relative to chondritic abundance with the exception of Pb, which shows enrichments up to a factor of 500. An apparent anticorrelation between the Ni-content and the element concentration was observed in both types of spherules. The fractionation patterns of the iron and chondritic spheres are not complementary and consequently the two iron spheres examined in this study are unlikely to result from the ejection of globules of Fe/Ni from parent chondritic micrometeoroids.

  2. Trace elemental analysis of school chalk using energy dispersive X-ray florescence spectroscopy (ED-XRF)

    SciTech Connect

    Maruthi, Y. A.; Das, N. Lakshmana; Ramprasad, S.; Ram, S. S.; Sudarshan, M.

    2015-08-28

    The present studies focus the quantitative analysis of elements in school chalk to ensure the safety of its use. The elements like Calcium (Ca), Aluminum (Al), Iron (Fe), Silicon (Si) and Chromium (Cr) were analyzed from settled chalk dust samples collected from five classrooms (CD-1) and also from another set of unused chalk samples collected from local market (CD-2) using Energy Dispersive X-Ray florescence(ED-XRF) spectroscopy. Presence of these elements in significant concentrations in school chalk confirmed that, it is an irritant and occupational hazard. It is suggested to use protective equipments like filtered mask for mouth, nose and chalk holders. This study also suggested using the advanced mode of techniques like Digital boards, marker boards and power point presentations to mitigate the occupational hazard for classroom chalk.

  3. Trace elemental analysis of school chalk using energy dispersive X-ray florescence spectroscopy (ED-XRF)

    NASA Astrophysics Data System (ADS)

    Maruthi, Y. A.; Das, N. Lakshmana; Ramprasad, S.; Ram, S. S.; Sudarshan, M.

    2015-08-01

    The present studies focus the quantitative analysis of elements in school chalk to ensure the safety of its use. The elements like Calcium (Ca), Aluminum (Al), Iron (Fe), Silicon (Si) and Chromium (Cr) were analyzed from settled chalk dust samples collected from five classrooms (CD-1) and also from another set of unused chalk samples collected from local market (CD-2) using Energy Dispersive X-Ray florescence(ED-XRF) spectroscopy. Presence of these elements in significant concentrations in school chalk confirmed that, it is an irritant and occupational hazard. It is suggested to use protective equipments like filtered mask for mouth, nose and chalk holders. This study also suggested using the advanced mode of techniques like Digital boards, marker boards and power point presentations to mitigate the occupational hazard for classroom chalk

  4. Quantitative analysis of trace palladium contamination in solution using electrochemical X-ray fluorescence (EC-XRF).

    PubMed

    Ayres, Zoë J; Newton, Mark E; Macpherson, Julie V

    2016-06-01

    The application of electrochemical X-ray fluorescence (EC-XRF), for the detection of palladium (Pd) contamination in a range of solutions containing electrochemically active compounds, present in excess and relevant to the pharmaceutical and food industries, is reported. In EC-XRF, EC is used to electrochemically pre-concentrate metal on an electrode under forced convection conditions, whilst XRF is employed to spectroscopically quantify the amount of metal deposited, which quantitatively correlates with the original metal concentration in solution. Boron doped diamond is used as the electrode due to its very wide cathodic window and the fact that B and C are non-interfering elements for XRF analysis. The effect of several parameters on the Pd XRF signal intensity are explored including: deposition potential (Edep), deposition time (tdep) and Pd(2+) concentration, [Pd(2+)]. Under high deposition potentials (Edep = -1.5 V), the Pd XRF peak intensity varies linearly with both tdep and [Pd(2+)]. Quantification of [Pd(2+)] is demonstrated in the presence of excess acetaminophen (ACM), l-ascorbic acid, caffeine and riboflavin. We show the same Pd XRF signal intensity (for [Pd(2+)] = 1.1 μM and tdep = 325 s) is observed, i.e. same amount of Pd is deposited on the electrode surface, irrespective of whether these redox active molecules are present or absent. For tdep = 900 s we report a limit of detection for [Pd(2+)] of 3.6 ppb (34 nM). Even lower LODs are possible by increasing tdep or by optimising the X-ray source specifically for Pd. The work presented for Pd detection in the presence of ACM, achieves the required detection sensitivity stipulated by international pharmacopeia guidelines. PMID:27118639

  5. THREE-DIMENSIONAL ADAPTIVE MESH REFINEMENT SIMULATIONS OF LONG-DURATION GAMMA-RAY BURST JETS INSIDE MASSIVE PROGENITOR STARS

    SciTech Connect

    Lopez-Camara, D.; Lazzati, Davide; Morsony, Brian J.; Begelman, Mitchell C.

    2013-04-10

    We present the results of special relativistic, adaptive mesh refinement, 3D simulations of gamma-ray burst jets expanding inside a realistic stellar progenitor. Our simulations confirm that relativistic jets can propagate and break out of the progenitor star while remaining relativistic. This result is independent of the resolution, even though the amount of turbulence and variability observed in the simulations is greater at higher resolutions. We find that the propagation of the jet head inside the progenitor star is slightly faster in 3D simulations compared to 2D ones at the same resolution. This behavior seems to be due to the fact that the jet head in 3D simulations can wobble around the jet axis, finding the spot of least resistance to proceed. Most of the average jet properties, such as density, pressure, and Lorentz factor, are only marginally affected by the dimensionality of the simulations and therefore results from 2D simulations can be considered reliable.

  6. Crystallization and preliminary X-ray diffraction analysis of a cold-adapted catalase from Vibrio salmonicida

    SciTech Connect

    Riise, Ellen Kristin; Lorentzen, Marit Sjo; Helland, Ronny; Willassen, Nils Peder

    2006-01-01

    Monoclinic (P2{sub 1}) crystals of a His-tagged form of V. salmonicida catalase without cofactor diffract X-rays to 1.96 Å. Catalase (EC 1.11.1.6) catalyses the breakdown of hydrogen peroxide to water and molecular oxygen. Recombinant Vibrio salmonicida catalase (VSC) possesses typical cold-adapted features, with higher catalytic efficiency, lower thermal stability and a lower temperature optimum than its mesophilic counterpart from Proteus mirabilis. Crystals of VSC were produced by the hanging-drop vapour-diffusion method using ammonium sulfate as precipitant. The crystals belong to the monoclinic space group P2{sub 1}, with unit-cell parameters a = 98.15, b = 217.76, c = 99.28 Å, β = 110.48°. Data were collected to 1.96 Å and a molecular-replacement solution was found with eight molecules in the asymmetric unit.

  7. Performances of a bent-crystal spectrometer adapted to resonant x-ray emission measurements on gas-phase samples

    SciTech Connect

    Journel, Loiec; El Khoury, Lara; Marin, Thierry; Guillemin, Renaud; Carniato, Stephane; Avila, Antoine; Delaunay, Renaud; Hague, Coryn F.; Simon, Marc

    2009-09-15

    We describe a bent-crystal spectrometer adapted to measure x-ray emission resulting from core-level excitation of gas-phase molecules in the 0.8-8 keV energy range. The spectrometer is based on the Johann principle, and uses a microfocused photon beam to provide high-resolution (resolving power of {approx}7500). A gas cell was designed to hold a high-pressure (300 mbar) sample of gas while maintaining a high vacuum (10{sup -9} mbar) in the chamber. The cell was designed to optimize the counting rate (2000 cts/s at the maximum of the Cl K{alpha} emission line), while minimizing self-absorption. Example of the K{alpha} emission lines of CH{sub 3}Cl molecules is presented to illustrate the capabilities of this new instrument.

  8. Adaptive-weighted total variation minimization for sparse data toward low-dose x-ray computed tomography image reconstruction

    NASA Astrophysics Data System (ADS)

    Liu, Yan; Ma, Jianhua; Fan, Yi; Liang, Zhengrong

    2012-12-01

    Previous studies have shown that by minimizing the total variation (TV) of the to-be-estimated image with some data and other constraints, piecewise-smooth x-ray computed tomography (CT) can be reconstructed from sparse-view projection data without introducing notable artifacts. However, due to the piecewise constant assumption for the image, a conventional TV minimization algorithm often suffers from over-smoothness on the edges of the resulting image. To mitigate this drawback, we present an adaptive-weighted TV (AwTV) minimization algorithm in this paper. The presented AwTV model is derived by considering the anisotropic edge property among neighboring image voxels, where the associated weights are expressed as an exponential function and can be adaptively adjusted by the local image-intensity gradient for the purpose of preserving the edge details. Inspired by the previously reported TV-POCS (projection onto convex sets) implementation, a similar AwTV-POCS implementation was developed to minimize the AwTV subject to data and other constraints for the purpose of sparse-view low-dose CT image reconstruction. To evaluate the presented AwTV-POCS algorithm, both qualitative and quantitative studies were performed by computer simulations and phantom experiments. The results show that the presented AwTV-POCS algorithm can yield images with several notable gains, in terms of noise-resolution tradeoff plots and full-width at half-maximum values, as compared to the corresponding conventional TV-POCS algorithm.

  9. Educational x-ray experiments and XRF measurements with a portable setup adapted for the characterization of cultural heritage objects

    NASA Astrophysics Data System (ADS)

    Sianoudis, I.; Drakaki, E.; Hein, A.

    2010-05-01

    It is common to modify valuable, sophisticated equipment, originally acquired for other purposes, to adapt it for the needs of educational experiments, with great didactic effectiveness. The present project concerns a setup developed from components of a portable system for energy dispersive x-ray fluorescence spectroscopy (EDXRF). Two educational modules have been developed on the basis of this setup. Module 1 comprises a series of x-ray laboratory exercises investigating basic principles, such as the verification of Moseley's law, Compton's law and the Lambert-Beer law. Module 2 concerns the calibration of the XRF with reference materials, aiming to get quantitative measurements of the elemental composition of objects of cultural interest. The application of the calibrated experimental setup is demonstrated with indicative measurements of metal objects and pigments of wall paintings, in order to discuss their spectra, and their qualitative and quantitative analyses. The setup and the applied experiments are designed as an educational package of laboratory exercises on the one hand for students in natural sciences, and on the other for the education of students who will work in the field of cultural heritage, such as conservation science or archaeological science.

  10. Determination of trace elements in freshwater rotifers and ciliates by total reflection X-ray fluorescence spectrometry

    NASA Astrophysics Data System (ADS)

    Woelfl, S.; Óvári, M.; Nimptsch, J.; Neu, T. R.; Mages, M.

    2016-02-01

    Element determination in plankton is important for the assessment of metal contamination of aquatic environments. Until recently, it has been difficult to determine elemental content in rotifers or ciliates derived from natural plankton samples because of the difficulty in handling and separation of these fragile organisms. The aim of this study was to evaluate methods for separation of rotifers and large ciliates from natural plankton samples (μg range dry weight) and subsequent analysis of their elemental content using total-reflection X-ray fluorescence spectrometry (TXRF). Plankton samples were collected from different aquatic environments (three lakes, one river) in Chile, Argentina and Hungary. From one to eighty specimens of five rotifer species (Brachionus calyciflorus, Brachionus falcatus, Asplanchna sieboldii, Asplanchna sp., Philodina sp.) and four to twelve specimens of one large ciliate (Stentor amethystinus) were prepared according to the dry method originally developed for microcrustaceans, and analysed by TRXF following in situ microdigestion. Our results demonstrated that it possible to process these small and fragile organisms (individual dry mass: 0.17-9.39 μg ind- 1) via careful washing and preparation procedures. We found species-dependent differences of the element mass fractions for some of the elements studied (Cr, Mn, Fe, Ni, Cu, Zn, As, Pb), especially for Cu, Fe and Mn. One large rotifer species (A. sieboldii) also showed a negative correlation between individual dry weight and the element content for Pb, Ni and Cr. We conclude that our application of the in situ microdigestion-TRXF method is suitable even for rotifers and ciliates, greatly expanding the possibilities for use of plankton in biomonitoring of metal contamination in aquatic environments.

  11. Application of gamma ray spectrometric measurements and VLF-EM data for tracing vein type uranium mineralization

    NASA Astrophysics Data System (ADS)

    Gaafar, Ibrahim

    2015-12-01

    This study is an attempt to use the gamma ray spectrometric measurements and VLF-EM data to identify the subsurface structure and map uranium mineralization along El Sela shear zone, South Eastern Desert of Egypt. Many injections more or less mineralized with uranium and associated with alteration processes were recorded in El Sela shear zone. As results from previous works, the emplacement of these injections is structurally controlled and well defined by large shear zones striking in an ENE-WSW direction and crosscut by NW-SE to NNW-SSE fault sets. VLF method has been applied to map the structure and the presence of radioactive minerals that have been delineated by the detection of high uranium mineralization. The electromagnetic survey was carried out to detect the presence of shallow and deep conductive zones that cross the granites along ENE-WSW fracturing directions and to map its spatial distribution. The survey comprised seventy N-S spectrometry and VLF-EM profiles with 20 m separation. The resulted data were displayed as composite maps for K, eU and eTh as well as VLF-Fraser map. Twelve profiles with 100 m separation were selected for detailed description. The VLF-EM data were interpreted qualitatively as well as quantitatively using the Fraser and the Karous-Hjelt filters. Fraser filtered data and relative current density pseudo-sections indicate the presence of shallow and deep conductive zones that cross the granites along ENE-WSW shearing directions. High uranium concentrations found just above the higher apparent current-density zones that coincide with El-Sela shear zone indicate a positive relation between conductivity and uranium minerals occurrence. This enables to infer that the anomalies detected by VLF-EM data are due to the highly conductive shear zone enriched with uranium mineralization extending for more than 80 m.

  12. Stent enhancement in digital x-ray fluoroscopy using an adaptive feature enhancement filter

    NASA Astrophysics Data System (ADS)

    Jiang, Yuhao; Zachary, Josey

    2016-03-01

    Fluoroscopic images belong to the classes of low contrast and high noise. Simply lowering radiation dose will render the images unreadable. Feature enhancement filters can reduce patient dose by acquiring images at low dose settings and then digitally restoring them to the original quality. In this study, a stent contrast enhancement filter is developed to selectively improve the contrast of stent contour without dramatically boosting the image noise including quantum noise and clinical background noise. Gabor directional filter banks are implemented to detect the edges and orientations of the stent. A high orientation resolution of 9° is used. To optimize the use of the information obtained from Gabor filters, a computerized Monte Carlo simulation followed by ROC study is used to find the best nonlinear operator. The next stage of filtering process is to extract symmetrical parts in the stent. The global and local symmetry measures are used. The information gathered from previous two filter stages are used to generate a stent contour map. The contour map is then scaled and added back to the original image to get a contrast enhanced stent image. We also apply a spatio-temporal channelized Hotelling observer model and other numerical measures to characterize the response of the filters and contour map to optimize the selections of parameters for image quality. The results are compared to those filtered by an adaptive unsharp masking filter previously developed. It is shown that stent enhancement filter can effectively improve the stent detection and differentiation in the interventional fluoroscopy.

  13. Analysis of nutrition-relevant trace elements in human blood and serum by means of total reflection X-ray fluorescence (TXRF) spectroscopy

    NASA Astrophysics Data System (ADS)

    Stosnach, Hagen; Mages, Margarete

    2009-04-01

    In clinical service laboratories, one of the most common analytical tasks with regard to inorganic traces is the determination of the nutrition-relevant elements Fe, Cu, Zn, and Se. Because of the high numbers of samples and the commercial character of these analyses, a time-consuming sample preparation must be avoided. In this presentation, the results of total reflection X-ray fluorescence measurements with a low-power system and different sample preparation procedures are compared with those derived from analysis with common methods like Atomic Absorption Spectroscopy (AAS) and Inductively Coupled Plasma Mass Spectroscopy (ICP-MS). The results of these investigations indicate that the optimal total reflection X-ray fluorescence analysis of the nutrition-relevant elements Fe, Cu, Zn, and Se can be performed by preparing whole blood and serum samples after dilution with ultrapure water and transferring 10 μl of internally standardized sample to an unsiliconized quartz glass sample carrier with subsequent drying in a laboratory oven. Suitable measurement time was found to be 600 s. The enhanced sample preparation by means of microwave or open digestion, in parts combined with cold plasma ashing, led to an improvement of detection limits by a factor of 2 for serum samples while for whole blood samples an improvement was only observed for samples prepared by means of microwave digestion. As the matrix elements P, S, Cl, and for whole blood Fe have a major influence on the detection limits, most probably a further enhancement of analytical quality requires the removal of the organic matrix. However, for the routine analysis of the nutrition-relevant elements, the dilution preparation was found to be sufficient.

  14. Combining ray-tracing and FDTD to enable the simulation of complex optical devices in an iterative simulation process with reduced simulation effort

    NASA Astrophysics Data System (ADS)

    Leiner, Claude; Nemitz, Wolfgang; Schweitzer, Susanne; Wenzl, Franz P.; Peharz, Gerhard; Sommer, Christian

    2015-09-01

    The development of photonic multi-scale devices with tailor-made optical properties requires the control and the manipulation of light propagation within structures of different length scales, ranging from sub-wavelength to macroscopic dimensions. Unfortunately, applications of common optical simulation methods are usually restricted to particular size regimes. For this reason, a complete optical simulation of multi-scale devices can only be conducted by combining different simulation methods. In our previous work we already introduced an interface method that uses the Poynting vector to bridge between classical Ray-Tracing and the Finite-Difference-Time-Domain method to enable the simulation of suchlike devices. In this contribution we present and discuss a method to reduce the simulation effort and time consumption of this interface simulation process. This approach is based on an FDTD simulation concept for creating the matrices containing probability density distributions that are needed for the FDTD-RT interface simulations by using broadband frequency sources. With this new FDTD simulation concept, the number of simulations needed to create these matrices can be significantly decreased.

  15. Accounting for coherent effects in the ray-tracing of light-emitting diodes with interface gratings via mixed-level simulation

    NASA Astrophysics Data System (ADS)

    Bahl, Mayank; Heller, Evan; Cassarly, William; Scarmozzino, Robert

    2016-01-01

    Ray-tracing (RT) has long been the workhorse technique for analyzing light-emitting diode (LED) dies and packages and has led to significant improvements in extraction efficiency and beam shaping. However, to achieve further enhancements, nano-/microscale features such as patterned substrates and surface textures have been explored. The coherent effects arising from these near/subwavelength features are difficult to include in the RT of the packaged device. We show that under certain conditions these effects can have a significant impact on LED performance, especially if back-reflectors are present. Furthermore, we demonstrate that coherence must be accounted for even in structures that would otherwise be considered as having relatively large feature sizes, such as gratings with periods many times the wavelength. We present comparisons between the optical responses of prototypical periodically patterned substrates modeled with RT alone and with a mixed-level approach that combines RT and rigorous electromagnetic simulation, such as rigorous coupled wave analysis and finite-difference time-domain. Several examples with varying lateral periods are computed with both methods. It is shown that these results may differ, and that these differences can be significant if back reflection is present. We conclude that a mixed-level approach is an efficient and accurate method to model light extraction in modern LEDs.

  16. General relativistic ray-tracing algorithm for the determination of the electron-positron energy deposition rate from neutrino pair annihilation around rotating neutron and quark stars

    NASA Astrophysics Data System (ADS)

    Kovács, Z.; Harko, T.

    2011-11-01

    We present a full general relativistic numerical code for estimating the energy-momentum deposition rate (EMDR) from neutrino pair annihilation (?). The source of the neutrinos is assumed to be a neutrino-cooled accretion disc around neutron and quark stars. We calculate the neutrino trajectories by using a ray-tracing algorithm with the general relativistic Hamilton's equations for neutrinos and derive the spatial distribution of the EMDR due to the annihilations of neutrinos and antineutrinos around rotating neutron and quark stars. We obtain the EMDR for several classes of rotating neutron stars, described by different equations of state of the neutron matter, and for quark stars, described by the Massachusetts Institute of Technology (MIT) bag model equation of state and in the colour-flavour-locked (CFL) phase. The distribution of the total annihilation rate of the neutrino-antineutrino pairs around rotating neutron and quark stars is studied for isothermal discs and accretion discs in thermodynamical equilibrium. We demonstrate both the differences in the equations of state for neutron and quark matter and rotation with the general relativistic effects significantly modify the EMDR of the electrons and positrons generated by the neutrino-antineutrino pair annihilation around compact stellar objects, as measured at infinity.

  17. Tracing coffee tabletop traces.

    PubMed

    Leiterer, Jork; Emmerling, Franziska; Panne, Ulrich; Christen, Wolfgang; Rademann, Klaus

    2008-08-01

    Crystallization processes under different conditions are of fundamental interest in chemistry, pharmacy, and medicine. Therefore, we have studied the formation of micro- and nanosized crystals using water-caffeine (1,3,7-trimethyl-1 H-purine-2,6(3 H,7 H)-dione) solutions under ambient conditions as a relevant model system. When droplets of an aqueous caffeine solution evaporate and eventually dry on surfaces (glass, polystyrene, and polyester), stable "coffee tabletop" rings with a perimeter of typically 3 mm are formed after 20 to 50 min. Using a micro focus X-ray beam available at the BESSY muSpot-beamline, the fine structure of different caffeine needles can be distinguished. Unexpectedly, both crystal modifications (alpha- and beta-caffeine) are present, but locally separated in these rings. Furthermore, AFM studies reveal the presence of even smaller particles on a nanometer length scale. To eliminate influences of surface irregularities from the crystallization process, acoustic levitation of liquid samples was employed. Such levitated droplets are trapped in a stable position and only surrounded by air. The solvent in an ultrasonically levitated drop evaporates completely, and the resulting crystallization of caffeine was followed in situ by synchrotron X-ray diffraction. In this case, the diffraction pattern is in accordance with pure alpha-caffeine and does not indicate the formation of the room temperature polymorph beta-caffeine. Hence, our investigations open new vistas that may lead to a controlled formation of cocrystals and novel polymorphs of micro- and nanocrystalline materials, which are of relevance for fundamental studies as well as for pharmaceutical and medical applications. PMID:18582001

  18. Adaptive-weighted total variation minimization for sparse data toward low-dose x-ray computed tomography image reconstruction.

    PubMed

    Liu, Yan; Ma, Jianhua; Fan, Yi; Liang, Zhengrong

    2012-12-01

    Previous studies have shown that by minimizing the total variation (TV) of the to-be-estimated image with some data and other constraints, piecewise-smooth x-ray computed tomography (CT) can be reconstructed from sparse-view projection data without introducing notable artifacts. However, due to the piecewise constant assumption for the image, a conventional TV minimization algorithm often suffers from over-smoothness on the edges of the resulting image. To mitigate this drawback, we present an adaptive-weighted TV (AwTV) minimization algorithm in this paper. The presented AwTV model is derived by considering the anisotropic edge property among neighboring image voxels, where the associated weights are expressed as an exponential function and can be adaptively adjusted by the local image-intensity gradient for the purpose of preserving the edge details. Inspired by the previously reported TV-POCS (projection onto convex sets) implementation, a similar AwTV-POCS implementation was developed to minimize the AwTV subject to data and other constraints for the purpose of sparse-view low-dose CT image reconstruction. To evaluate the presented AwTV-POCS algorithm, both qualitative and quantitative studies were performed by computer simulations and phantom experiments. The results show that the presented AwTV-POCS algorithm can yield images with several notable gains, in terms of noise-resolution tradeoff plots and full-width at half-maximum values, as compared to the corresponding conventional TV-POCS algorithm. PMID:23154621

  19. Arbitrary Lagrangian Eulerian Adaptive Mesh Refinement

    2009-09-29

    This is a simulation code involving an ALE (arbitrary Lagrangian-Eulerian) hydrocode with AMR (adaptive mesh refinement) and pluggable physics packages for material strength, heat conduction, radiation diffusion, and laser ray tracing developed a LLNL, UCSD, and Berkeley Lab. The code is an extension of the open source SAMRAI (Structured Adaptive Mesh Refinement Application Interface) code/library. The code can be used in laser facilities such as the National Ignition Facility. The code is alsi being appliedmore » to slurry flow (landslides).« less

  20. Relationship of college student characteristics and inquiry-based geometrical optics instruction to knowledge of image formation with light-ray tracing

    NASA Astrophysics Data System (ADS)

    Isik, Hakan

    This study is premised on the fact that student conceptions of optics appear to be unrelated to student characteristics of gender, age, years since high school graduation, or previous academic experiences. This study investigated the relationships between student characteristics and student performance on image formation test items and the changes in student conceptions of optics after an introductory inquiry-based physics course. Data was collected from 39 college students who were involved in an inquiry-based physics course teaching topics of geometrical optics. Student data concerning characteristics and previous experiences with optics and mathematics were collected. Assessment of student understanding of optics knowledge for pinholes, plane mirrors, refraction, and convex lenses was collected with, the Test of Image Formation with Light-Ray Tracing instrument. Total scale and subscale scores representing the optics instrument content were derived from student pretest and posttest responses. The types of knowledge, needed to answer each optics item correctly, were categorized as situational, conceptual, procedural, and strategic knowledge. These types of knowledge were associated with student correct and incorrect responses to each item to explain the existences and changes in student scientific and naive conceptions. Correlation and stepwise multiple regression analyses were conducted to identify the student characteristics and academic experiences that significantly predicted scores on the subscales of the test. The results showed that student experience with calculus was a significant predictor of student performance on the total scale as well as on the refraction subscale of the Test of Image Formation with Light-Ray Tracing. A combination of student age and previous academic experience with precalculus was a significant predictor of student performance on the pretest pinhole subscale. Student characteristic of years since high school graduation

  1. Trace element distribution in annual stalagmite laminae mapped by micrometer-resolution X-ray fluorescence: Implications for incorporation of environmentally significant species

    NASA Astrophysics Data System (ADS)

    Borsato, Andrea; Frisia, Silvia; Fairchild, Ian J.; Somogyi, Andrea; Susini, Jean

    2007-03-01

    Stalagmite ER78, from Grotta di Ernesto cave in NE Italy displays clear annual lamination consistent with its shallow depth below a forest ecosystem subject to autumnal peaking of water infiltration. Synchrotron radiation scanning micro-X-ray fluorescence analyses of heavy elements at European Synchrotron Radiation Facility beamline ID22, and light elements at ID21, with 1-3 μm resolution has been combined with data from ion microprobe analyses to reveal chemical variability across the visible layers of these annual laminae. A series of elements display a symmetrical peak, centered around the thin, dark layer at the top of each lamina. The peak concentration is ordered Y > Zn, Cu and Pb > P and Br. This hierarchy is thought to reflect the selectivity of transport of these elements, possibly by organic colloids flushed from the soil zone during autumn infiltration. Ion microprobe analysis indicates Na and F also increase, as does H, the latter reflecting increased microporosity. Sr displays a trough around the dark and thin autumn layer implying that its incorporation may be limited by competition with other elements. Mg and S show a different pattern of annual variation and Fe displays none. The trace metals, Br and Y display peak abundance in the early 20th century, which appears to reflect a period of tree-felling rather than a climatic anomaly. The results demonstrate the power of the high spatial resolution and low detection limits of the synchrotron technique, and its ability to produce quantitative maps that allow distinction of layered structure from that of isolated particles, or irregular inhomogeneities.

  2. SU-E-T-85: Comparison of Treatment Plans Calculated Using Ray Tracing and Monte Carlo Algorithms for Lung Cancer Patients Having Undergone Radiotherapy with Cyberknife

    SciTech Connect

    Pennington, A; Selvaraj, R; Kirkpatrick, S; Oliveira, S; Leventouri, T

    2014-06-01

    Purpose: The latest publications indicate that the Ray Tracing algorithm significantly overestimates the dose delivered as compared to the Monte Carlo (MC) algorithm. The purpose of this study is to quantify this overestimation and to identify significant correlations between the RT and MC calculated dose distributions. Methods: Preliminary results are based on 50 preexisting RT algorithm dose optimization and calculation treatment plans prepared on the Multiplan treatment planning system (Accuray Inc., Sunnyvale, CA). The analysis will be expanded to include 100 plans. These plans are recalculated using the MC algorithm, with high resolution and 1% uncertainty. The geometry and number of beams for a given plan, as well as the number of monitor units, is constant for the calculations for both algorithms and normalized differences are compared. Results: MC calculated doses were significantly smaller than RT doses. The D95 of the PTV was 27% lower for the MC calculation. The GTV and PTV mean coverage were 13 and 39% less for MC calculation. The first parameter of conformality, as defined as the ratio of the Prescription Isodose Volume to the PTV Volume was on average 1.18 for RT and 0.62 for MC. Maximum doses delivered to OARs was reduced in the MC plans. The doses for 1000 and 1500 cc of total lung minus PTV, respectively were reduced by 39% and 53% for the MC plans. The correlation of the ratio of air in PTV to the PTV with the difference in PTV coverage had a coefficient of −0.54. Conclusion: The preliminary results confirm that the RT algorithm significantly overestimates the dosages delivered confirming previous analyses. Finally, subdividing the data into different size regimes increased the correlation for the smaller size PTVs indicating the MC algorithm improvement verses the RT algorithm is dependent upon the size of the PTV.

  3. Comparison of slope and height profiles for flat synchrotron x-ray mirrors measured with a long trace profiler and a Fizeau interferometer.

    SciTech Connect

    Qian, J.; Assoufid, L.; Macrander, A.; X-Ray Science Division

    2007-01-01

    Long trace profilers (LTPS) have been used at many synchrotron radiation laboratories worldwide for over a decade to measure surface slope profiles of long grazing incidence x-ray mirrors. Phase measuring interferometers (PMIs) of the Fizeau type, on the other hand, are being used by most mirror manufacturers to accomplish the same task. However, large mirrors whose dimensions exceed the aperture of the Fizeau interferometer require measurements to be carried out at grazing incidence, and aspheric optics require the use of a null lens. While an LTP provides a direct measurement of ID slope profiles, PMIs measure area height profiles from which the slope can be obtained by a differentiation algorithm. Measurements of the two types of instruments have been found by us to be in good agreement, but to our knowledge there is no published work directly comparing the two instruments. This paper documents that comparison. We measured two different nominally flat mirrors with both the LTP in operation at the Advanced Photon Source (a type-II LTP) and a Fizeau-type PMI interferometer (Wyko model 6000). One mirror was 500 mm long and made of Zerodur, and the other mirror was 350 mm long and made of silicon. Slope error results with these instruments agree within nearly 100% (3.11 {+-} 0.15 {micro}rad for the LTP, and 3.11 {+-} 0.02 {micro}rad for the Fizeau PMI interferometer) for the medium quality Zerodur mirror with 3 {micro}rad rms nominal slope error. A significant difference was observed with the much higher quality silicon mirror. For the Si mirror, slope error data is 0.39 {+-} 0.08 {micro}rad from LTP measurements but it is 0.35 {+-} 0.01 {micro}rad from PMI interferometer measurements. The standard deviations show that the Fizeau PMI interferometer has much better measurement repeatability.

  4. Assessment of the Accuracy of the Conventional Ray-Tracing Technique: Implications in Remote Sensing and Radiative Transfer Involving Ice Clouds.

    NASA Technical Reports Server (NTRS)

    Bi, Lei; Yang, Ping; Liu, Chao; Yi, Bingqi; Baum, Bryan A.; Van Diedenhoven, Bastiaan; Iwabuchi, Hironobu

    2014-01-01

    A fundamental problem in remote sensing and radiative transfer simulations involving ice clouds is the ability to compute accurate optical properties for individual ice particles. While relatively simple and intuitively appealing, the conventional geometric-optics method (CGOM) is used frequently for the solution of light scattering by ice crystals. Due to the approximations in the ray-tracing technique, the CGOM accuracy is not well quantified. The result is that the uncertainties are introduced that can impact many applications. Improvements in the Invariant Imbedding T-matrix method (II-TM) and the Improved Geometric-Optics Method (IGOM) provide a mechanism to assess the aforementioned uncertainties. The results computed by the II-TMþIGOM are considered as a benchmark because the IITM solves Maxwell's equations from first principles and is applicable to particle size parameters ranging into the domain at which the IGOM has reasonable accuracy. To assess the uncertainties with the CGOM in remote sensing and radiative transfer simulations, two independent optical property datasets of hexagonal columns are developed for sensitivity studies by using the CGOM and the II-TMþIGOM, respectively. Ice cloud bulk optical properties obtained from the two datasets are compared and subsequently applied to retrieve the optical thickness and effective diameter from Moderate Resolution Imaging Spectroradiometer (MODIS) measurements. Additionally, the bulk optical properties are tested in broadband radiative transfer (RT) simulations using the general circulation model (GCM) version of the Rapid Radiative Transfer Model (RRTMG) that is adopted in the National Center for Atmospheric Research (NCAR) Community Atmosphere Model (CAM, version 5.1). For MODIS retrievals, the mean bias of uncertainties of applying the CGOM in shortwave bands (0.86 and 2.13 micrometers) can be up to 5% in the optical thickness and as high as 20% in the effective diameter, depending on cloud optical

  5. SU-E-T-587: Monte Carlo Versus Ray-Tracing for Treatment Planning Involving CNS Tumors On the MultiPlan System for CyberKnife Radiosurgery

    SciTech Connect

    Forbang, R Teboh

    2014-06-01

    Purpose: MultiPlan, the treatment planning system for the CyberKnife Robotic Radiosurgery system offers two approaches to dose computation, namely Ray-Tracing (RT), the default technique and Monte Carlo (MC), an option. RT is deterministic, however it accounts for primary heterogeneity only. MC on the other hand has an uncertainty associated with the calculation results. The advantage is that in addition, it accounts for heterogeneity effects on the scattered dose. Not all sites will benefit from MC. The goal of this work was to focus on central nervous system (CNS) tumors and compare dosimetrically, treatment plans computed with RT versus MC. Methods: Treatment plans were computed using both RT and MC for sites covering (a) the brain (b) C-spine (c) upper T-spine (d) lower T-spine (e) L-spine and (f) sacrum. RT was first used to compute clinically valid treatment plans. Then the same treatment parameters, monitor units, beam weights, etc., were used in the MC algorithm to compute the dose distribution. The plans were then compared for tumor coverage to illustrate the difference if any. All MC calculations were performed at a 1% uncertainty. Results: Using the RT technique, the tumor coverage for the brain, C-spine (C3–C7), upper T-spine (T4–T6), lower T-spine (T10), Lspine (L2) and sacrum were 96.8%, 93.1%, 97.2%, 87.3%, 91.1%, and 95.3%. The corresponding tumor coverage based on the MC approach was 98.2%, 95.3%, 87.55%, 88.2%, 92.5%, and 95.3%. It should be noted that the acceptable planning target coverage for our clinical practice is >95%. The coverage can be compromised for spine tumors to spare normal tissues such as the spinal cord. Conclusion: For treatment planning involving the CNS, RT and MC appear to be similar for most sites but for the T-spine area where most of the beams traverse lung tissue. In this case, MC is highly recommended.

  6. Assessment of the accuracy of the conventional ray-tracing technique: Implications in remote sensing and radiative transfer involving ice clouds

    NASA Astrophysics Data System (ADS)

    Bi, Lei; Yang, Ping; Liu, Chao; Yi, Bingqi; Baum, Bryan A.; van Diedenhoven, Bastiaan; Iwabuchi, Hironobu

    2014-10-01

    A fundamental problem in remote sensing and radiative transfer simulations involving ice clouds is the ability to compute accurate optical properties for individual ice particles. While relatively simple and intuitively appealing, the conventional geometric-optics method (CGOM) is used frequently for the solution of light scattering by ice crystals. Due to the approximations in the ray-tracing technique, the CGOM accuracy is not well quantified. The result is that the uncertainties are introduced that can impact many applications. Improvements in the Invariant Imbedding T-matrix method (II-TM) and the Improved Geometric-Optics Method (IGOM) provide a mechanism to assess the aforementioned uncertainties. The results computed by the II-TM+IGOM are considered as a benchmark because the II-TM solves Maxwells equations from first principles and is applicable to particle size parameters ranging into the domain at which the IGOM has reasonable accuracy. To assess the uncertainties with the CGOM in remote sensing and radiative transfer simulations, two independent optical property datasets of hexagonal columns are developed for sensitivity studies by using the CGOM and the II-TM+IGOM, respectively. Ice cloud bulk optical properties obtained from the two datasets are compared and subsequently applied to retrieve the optical thickness and effective diameter from Moderate Resolution Imaging Spectroradiometer (MODIS) measurements. Additionally, the bulk optical properties are tested in broadband radiative transfer (RT) simulations using the general circulation model (GCM) version of the Rapid Radiative Transfer Model (RRTMG) that is adopted in the National Center for Atmospheric Research (NCAR) Community Atmosphere Model (CAM, version 5.1). For MODIS retrievals, the mean bias of uncertainties of applying the CGOM in shortwave bands (0.86 and 2.13 μm) can be up to 5% in the optical thickness and as high as 20% in the effective diameter, depending on cloud optical thickness and

  7. Adaptive thresholding with inverted triangular area for real-time detection of the heart rate from photoplethysmogram traces on a smartphone.

    PubMed

    Jiang, Wen Jun; Wittek, Peter; Zhao, Li; Gao, Shi Chao

    2014-01-01

    Photoplethysmogram (PPG) signals acquired by smartphone cameras are weaker than those acquired by dedicated pulse oximeters. Furthermore, the signals have lower sampling rates, have notches in the waveform and are more severely affected by baseline drift, leading to specific morphological characteristics. This paper introduces a new feature, the inverted triangular area, to address these specific characteristics. The new feature enables real-time adaptive waveform detection using an algorithm of linear time complexity. It can also recognize notches in the waveform and it is inherently robust to baseline drift. An implementation of the algorithm on Android is available for free download. We collected data from 24 volunteers and compared our algorithm in peak detection with two competing algorithms designed for PPG signals, Incremental-Merge Segmentation (IMS) and Adaptive Thresholding (ADT). A sensitivity of 98.0% and a positive predictive value of 98.8% were obtained, which were 7.7% higher than the IMS algorithm in sensitivity, and 8.3% higher than the ADT algorithm in positive predictive value. The experimental results confirmed the applicability of the proposed method. PMID:25570674

  8. Cytogenetic adaptive response with multiple small X-ray doses in mouse germ cells and its biological influence on the offspring of adapted males.

    PubMed

    Cai, L; Wang, P; Piao, X G

    1994-06-01

    Cytogenetic adaptive response of mouse germ cells was studied by exposing male mice to a sequence of 4 conditioning doses of 0.05 Gy each (D1) administered at 10-day intervals and subsequently to a single challenging dose of 1.5 Gy (D2). In concurrent experiments, male mice after treatment with D1 doses alone were mated to unirradiated females and the F1 males were given the D2 dose. Chromosomal aberrations in both spermatocytes and bone-marrow cells and UV-induced UDS in splenocytes of these mice were studied. Adapted mice (i.e., D1 + D2 exposures) responded with a significantly lower frequency of chromosomal aberrations than the non-adapted (D2 exposure only) controls. The relative reduction in frequencies was, however, similar to that observed in earlier work with a single conditioning dose of 0.05 Gy. The frequencies of chromosomal aberrations in spermatocytes and bone-marrow cells as well as the levels of UV-induced UDS in splenocytes of the F1 males in the group D1 to fathers + D2 to F1 males were the same as those in F1 males which received only the D2 exposure. PMID:7515464

  9. Determination of major elements by wavelength-dispersive X-ray fluorescence spectrometry and trace elements by inductively coupled plasma mass spectrometry in igneous rocks from the same fused sample (110 mg)

    NASA Astrophysics Data System (ADS)

    Amosova, Alena A.; Panteeva, Svetlana V.; Chubarov, Victor M.; Finkelshtein, Alexandr L.

    2016-08-01

    The fusion technique is proposed for simultaneous determination of 35 elements from the same sample. Only 110 mg of rock sample was used to obtain fused glasses for quantitative determination of 10 major elements by wavelength dispersive X-ray fluorescence analysis, 16 rare earth elements and some other trace elements by inductively coupled plasma mass spectrometry analysis. Fusion was performed with 1.1 g of lithium metaborate and LiBr solution as the releasing agent in platinum crucible in electric furnace at 1100 °C. The certified reference materials of ultramafic, mafic, intermediate and felsic igneous rocks have been applied to obtain the calibration curves for rock-forming oxides (Na2O, MgO, Al2O3, SiO2, P2O5, K2O, CaO, TiO2, MnO, Fe2O3) and some trace elements (Ba, Sr, Zr) determination by X-ray fluorescence analysis. The repeatability does not exceed the allowable standard deviation for a wide range of concentrations. In the most cases the relative standard deviation was less than 5%. Obtained glasses were utilized for the further determination of rare earth (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) and some other (Ba, Sr, Zr, Rb, Cs, Y, Nb, Hf, Ta, Th and U) trace elements by inductively coupled plasma mass spectrometry analysis with the same certified reference materials employed. The results could mostly be accepted as satisfactory. The proposed procedure essentially reduces the expenses in comparison with separate sample preparation for inductively coupled plasma mass spectrometry and X-ray fluorescence analysis.

  10. Hexacyanoferrate-adapted biofilm enables the development of a microbial fuel cell biosensor to detect trace levels of assimilable organic carbon (AOC) in oxygenated seawater.

    PubMed

    Cheng, Liang; Quek, Soon Bee; Cord-Ruwisch, Ralf

    2014-12-01

    A marine microbial fuel cell (MFC) type biosensor was developed for the detection of assimilable organic carbon (AOC) in ocean water for the purpose of online water quality monitoring for seawater desalination plants prone to biofouling of reverse osmosis (RO) membranes. The anodophilic biofilm that developed on the graphite tissue anode could detect acetate as the model AOC to concentrations as low as 5 µM (120 µg/L of AOC), which is sufficiently sensitive as an online biofouling risk sensor. Although the sensor was operated at a higher (+200 ± 10 mV) than the usual (-300 mV) anodic potential, the presence of oxygen completely suppressed the electrical signal. In order to overcome this outcompeting effect of oxygen over the anode as electron acceptor by the bacteria, hexacyanoferrate (HCF(III)) was found to enable the development of an adapted biofilm that transferred electrons to HCF(III) rather than oxygen. As the resultant of the reduced HCF(II) could readily transfer electrons to the anode while being re-oxidised to HCF(III), the marine MFC biosensor developed could be demonstrated to work in the presence of oxygen unlike traditional MFC. The possibility of operating the marine MFC in batch or continuous (in-line) mode has been explored by using coulombic or potentiometric interpretation of the signal. PMID:24942462

  11. Trace Element Mapping of a Biological Specimen by a Full-Field X-ray Fluorescence Imaging Microscope with a Wolter Mirror

    SciTech Connect

    Hoshino, Masato; Yamada, Norimitsu; Ishino, Toyoaki; Namiki, Takashi; Watanabe, Norio; Aoki, Sadao

    2007-01-19

    A full-field X-ray fluorescence imaging microscope with a Wolter mirror was applied to the element mapping of alfalfa seeds. The X-ray fluorescence microscope was built at the Photon Factory BL3C2 (KEK). X-ray fluorescence images of several growing stages of the alfalfa seeds were obtained. X-ray fluorescence energy spectra were measured with either a solid state detector or a CCD photon counting method. The element distributions of iron and zinc which were included in the seeds were obtained using a photon counting method.

  12. Tracing the History of the Energy Sector Related Applications Using Specially Adapted NASA Long-Term Climate Data Sets and Measures of Their Socio-Economic Value

    NASA Astrophysics Data System (ADS)

    Stackhouse, P. W.; Hoell, J. M.; Chandler, W.; Westberg, D. J.; Zhang, T.

    2012-12-01

    In the mid-1990's the National Renewable Energy Laboratory approached NASA Langley Research Center to gain information about the solar resource in Africa as estimated via early satellite based methods. From this began an effort that eventually involved collaboration with DOE NREL, Natural Resources Canada RETScreen International, and numerous other partners in industry and universities to make progressively improved data products available for the renewable energy and other energy related applications. In 2002, NASA Applied Science projects were initiated providing a more focused effort to accomplish the goal of empowering energy related decision support tools using NASA meteorological and climate related data sets. At this time, NASA Langley Research Center reorganized a project aimed to make long-term solar energy and meteorological data sets available to Energy sector related industries, including sustainable buildings and agroclimatology. This task involved the design and adaption of NASA derived data sets that these industries use, key partnerships, a commitment to validation, a commitment to expansion of parameters and data products over time, and a web based interface that allows energy industry specialists to obtained the needed data parameters in easy to use formats. This presentation shows the history of the NASA Langley Research Center effort to provide data sets for energy sector applications. This includes the development and usage of the Surface meteorology and Solar Energy (SSE, http://eosweb.larc.nasa.gov/sse/) web interface that has been improved under the Prediction of Worldwide renewable Energy Resource Project (POWER, http://power.larc.nasa.gov). Through the years the data sets provided now span more than 30 years and since 2009 include global parameters released within about 4-6 days of real time. The history of usage of this web site is discussed in terms of key partnerships and new data releases. We will present ways of categorizing the

  13. Separation and enrichment of palladium and gold in biological and environmental samples, adapted to the determination by total reflection X-ray fluorescence.

    PubMed

    Messerschmidt, J; von Bohlen, A; Alt, F; Klockenkämper, R

    2000-03-01

    The reductive co-precipitation of trace and ultra-trace elements together with mercury followed by complete evaporation of the mercury makes it possible to determine palladium and gold by total reflection X-ray fluorescence. Both elements can be detected without interferences at optimal sensitivity in the pg range. Thus, detection limits of, e.g., 2.5 ng L-1 for palladium and 2.0 ng L-1 for gold, in urine, were obtained. The precision was determined to 0.04 at a palladium concentration of about 200 ng L-1 urine and to 0.19 at a gold concentration of only 18 ng L-1. The recovery for a urine sample spiked with known amounts of palladium and gold amounted to > 95%. Results of the combined procedure are given for the determination of palladium and gold in the urine of non-exposed and occupationally exposed persons and in some other environmentally relevant samples. PMID:10829339

  14. Comparison of Planned Dose Distributions Calculated by Monte Carlo and Ray-Trace Algorithms for the Treatment of Lung Tumors With CyberKnife: A Preliminary Study in 33 Patients

    SciTech Connect

    Wilcox, Ellen E.; Daskalov, George M.; Lincoln, Holly; Shumway, Richard C.; Kaplan, Bruce M.; Colasanto, Joseph M.

    2010-05-01

    Purpose: To compare dose distributions calculated using the Monte Carlo algorithm (MC) and Ray-Trace algorithm (effective path length method, EPL) for CyberKnife treatments of lung tumors. Materials and Methods: An acceptable treatment plan is created using Multiplan 2.1 and MC dose calculation. Dose is prescribed to the isodose line encompassing 95% of the planning target volume (PTV) and this is the plan clinically delivered. For comparison, the Ray-Trace algorithm with heterogeneity correction (EPL) is used to recalculate the dose distribution for this plan using the same beams, beam directions, and monitor units (MUs). Results: The maximum doses calculated by the EPL to target PTV are uniformly larger than the MC plans by up to a factor of 1.63. Up to a factor of four larger maximum dose differences are observed for the critical structures in the chest. More beams traversing larger distances through low density lung are associated with larger differences, consistent with the fact that the EPL overestimates doses in low-density structures and this effect is more pronounced as collimator size decreases. Conclusions: We establish that changing the treatment plan calculation algorithm from EPL to MC can produce large differences in target and critical organs' dose coverage. The observed discrepancies are larger for plans using smaller collimator sizes and have strong dependency on the anatomical relationship of target-critical structures.

  15. Broad-band monitoring tracing the evolution of the jet and disc in the black hole candidate X-ray binary MAXI J1659-152

    NASA Astrophysics Data System (ADS)

    van der Horst, A. J.; Curran, P. A.; Miller-Jones, J. C. A.; Linford, J. D.; Gorosabel, J.; Russell, D. M.; de Ugarte Postigo, A.; Lundgren, A. A.; Taylor, G. B.; Maitra, D.; Guziy, S.; Belloni, T. M.; Kouveliotou, C.; Jonker, P. G.; Kamble, A.; Paragi, Z.; Homan, J.; Kuulkers, E.; Granot, J.; Altamirano, D.; Buxton, M. M.; Castro-Tirado, A.; Fender, R. P.; Garrett, M. A.; Gehrels, N.; Hartmann, D. H.; Kennea, J. A.; Krimm, H. A.; Mangano, V.; Ramirez-Ruiz, E.; Romano, P.; Wijers, R. A. M. J.; Wijnands, R.; Yang, Y. J.

    2013-12-01

    MAXI J1659-152 was discovered on 2010 September 25 as a new X-ray transient, initially identified as a gamma-ray burst, but was later shown to be a new X-ray binary with a black hole as the most likely compact object. Dips in the X-ray light curves have revealed that MAXI J1659-152 is the shortest period black hole candidate identified to date. Here we present the results of a large observing campaign at radio, submillimetre, near-infrared (nIR), optical and ultraviolet (UV) wavelengths. We have combined this very rich data set with the available X-ray observations to compile a broad-band picture of the evolution of this outburst. We have performed broad-band spectral modelling, demonstrating the presence of a spectral break at radio frequencies and a relationship between the radio spectrum and X-ray states. Also, we have determined physical parameters of the accretion disc and put them into context with respect to the other parameters of the binary system. Finally, we have investigated the radio-X-ray and nIR/optical/UV-X-ray correlations up to ˜3 yr after the outburst onset to examine the link between the jet and the accretion disc, and found that there is no significant jet contribution to the nIR emission when the source is in the soft or intermediate X-ray spectral state, consistent with our detection of the jet break at radio frequencies during these states.

  16. Development of a digital panoramic X-ray imaging system of adaptive image layers for dental applications

    NASA Astrophysics Data System (ADS)

    Choi, S. I.; Park, Y. O.; Cho, H. S.; Oh, J. E.; Cho, H. M.; Hong, D. K.; Lee, M. S.; Yang, Y. J.; Je, U. K.; Kim, D. S.; Lee, H. K.

    2011-10-01

    As a continuation of our digital radiographic sensor R&D, we have developed a prototyped digital panoramic X-ray imaging system for dental applications. The imaging system consists of a slit-collimated X-ray generator with a 0.4 mm focal spot size and a 3.5 mm Al filtration, a linear-array typed CMOS imager with a 48×48 μm 2 pixel size and a 128 (in the scan direction)×3072 (in the vertical direction) pixel format, a series of microstep motors for the precise motion control of the imaging system, and the designed sequences for the motion control and pixel readout required to make a specific plane of interest (POI) to be focused. With the several test phantoms we designed, we obtained useful digital panoramic X-ray images by moving the X-ray generator and the CMOS imager along a continuously sliding rotational center. In this study, we demonstrated that the prototype system can be applicable to any shaped POI or multi-POIs simultaneously to be focused, provided that adequate sequences for motion control and pixel readout are designed. We expect that the imaging system will be useful for our ongoing applications of dental panoramic radiography and nondestructive testing.

  17. Analytical possibilities of different X-ray fluorescence systems for determination of trace elements in aqueous samples pre-concentrated with carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Marguí, E.; Zawisza, B.; Skorek, R.; Theato, T.; Queralt, I.; Hidalgo, M.; Sitko, R.

    2013-10-01

    This study was aimed to achieve improved instrumental sensitivity and detection limits for multielement determination of V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Se, Pb and Cd in liquid samples by using different X-ray fluorescence (XRF) configurations (a benchtop energy-dispersive X-ray fluorescence spectrometer, a benchtop polarised energy-dispersive X-ray fluorescence spectrometer and a wavelength-dispersive X-ray fluorescence spectrometer). The preconcentration of metals from liquid solutions consisted on a solid-phase extraction using carbon nanotubes (CNTs) as solid sorbents. After the extraction step, the aqueous sample was filtered and CNTs with the absorbed elements were collected onto a filter paper which was directly analyzed by XRF. The calculated detection limits in all cases were in the low ng mL- 1 range. Nevertheless, results obtained indicate the benefits, in terms of sensitivity, of using polarized X-ray sources using different secondary targets in comparison to conventional XRF systems, above all if Cd determination is required. The developed methodologies, using the aforementioned equipments, have been applied for multielement determination in water samples from an industrial area of Poland.

  18. Integration of airborne LiDAR data and voxel-based ray tracing to determine high-resolution solar radiation dynamics at the forest floor: implications for improving stand-scale distributed snowmelt models

    NASA Astrophysics Data System (ADS)

    Musselman, K. N.; Molotch, N. P.; Margulis, S. A.

    2012-12-01

    Forest architecture dictates sub-canopy solar irradiance and the resulting patterns can vary seasonally and over short spatial distances. These radiation dynamics are thought to have significant implications on snowmelt processes, regional hydrology, and remote sensing signatures. The variability calls into question many assumptions inherent in traditional canopy models (e.g. Beer's Law) when applied at high resolution (i.e. 1 m). We present a method of estimating solar canopy transmissivity using airborne LiDAR data. The canopy structure is represented in 3-D voxel space (i.e. a cubic discretization of a 3-D domain analogous to a pixel representation of a 2-D space). The solar direct beam canopy transmissivity (DBT) is estimated with a ray-tracing algorithm and the diffuse component is estimated from LiDAR-derived effective LAI. Results from one year at five-minute temporal and 1 m spatial resolutions are presented from Sequoia National Park. Compared to estimates from 28 hemispherical photos, the ray-tracing model estimated daily mean DBT with a 10% average error, while the errors from a Beer's-type DBT estimate exceeded 20%. Compared to the ray-tracing estimates, the Beer's-type transmissivity method was unable to resolve complex spatial patterns resulting from canopy gaps, individual tree canopies and boles, and steep variable terrain. The snowmelt model SNOWPACK was applied at locations of ultrasonic snow depth sensors. Two scenarios were tested; 1) a nominal case where canopy model parameters were obtained from hemispherical photographs, and 2) an explicit scenario where the model was modified to accept LiDAR-derived time-variant DBT. The bulk canopy treatment was generally unable to simulate the sub-canopy snowmelt dynamics observed at the depth sensor locations. The explicit treatment reduced error in the snow disappearance date by one week and both positive and negative melt-season SWE biases were reduced. The results highlight the utility of LiDAR canopy

  19. Determination of trace amounts of hexavalent chromium in drinking waters by dispersive microsolid-phase extraction using modified multiwalled carbon nanotubes combined with total reflection X-ray fluorescence spectrometry

    NASA Astrophysics Data System (ADS)

    Bahadir, Z.; Bulut, V. N.; Hidalgo, M.; Soylak, M.; Marguí, E.

    2015-05-01

    A methodology based on the combination of dispersive microsolid-phase extraction (DMSPE) with total reflection X-ray fluorescence (TXRF) spectrometry is proposed for the determination of hexavalent chromium in drinking waters. Multiwalled carbon nanotubes (MWCNTs) modified with the anionic exchanger tricaprylmethylammonium chloride (Aliquat 336) were used as solid sorbents. After the sorption process of Cr(VI) on the modified MWCNTs, the aqueous sample was separated by centrifugation and the loaded MWCNTs were suspended using a small volume of an internal standard solution and analyzed directly by a benchtop TXRF spectrometer, without any elution step. Parameters affecting the extraction process (pH and volume of the aqueous sample, amount of MWCNTs, extraction time) and TXRF analysis (volume of internal standard, volume of deposited suspension on the reflector, drying mode, and instrumental parameters) have been carefully evaluated to test the real capability of the developed methodology for the determination of Cr(VI) at trace levels. Using the best analytical conditions, it was found that the minimum Cr(VI) content that can be detected in an aqueous solution was 3 μg L- 1. This value is almost 20 times lower than the maximum hexavalent chromium content permissible in drinking waters, according to the World Health Organization (WHO). Recoveries for spiked tap and mineral water samples were, in most cases, in the range of 101-108% which demonstrates the suitability of the TXRF methodology for monitoring Cr(VI) at trace levels in drinking water samples.

  20. Ray tracing through the liquid crystal point diffraction interferometer. 1998 summer research program for high school juniors at the University of Rochester`s Laboratory for Laser Energetics: Student research reports

    SciTech Connect

    Turner, A.

    1999-03-01

    The Omega laser is a system with many different parts that may cause imperfections. There are a multitude of lenses and mirrors, for example, that may not be polished correctly and can cause the laser wave front to have aberrations. The Liquid Crystal Point Diffraction Interferometer (L.C.P.D.I.) is a device whose main purpose is to read the wave front of the laser and measure any aberrations that may be on it. The way the L.C.P.D.I. reads the laser wave front and measures these aberrations is very complicated and has yet to be perfected. A ray-tracing model of the L.C.P.D.I. has been built, which calculates and models the ray trajectories, the optical paths of the rays, the O.P.D. between the object and reference beams, the absorption of the rays in the liquid crystal, and the intensities of each beam. It can predict an actual experiment by manipulating the different parameters of the program. It will be useful in optimization and further development of the L.C.P.D.I. Evidently, it is necessary to develop a liquid crystal solution with an O.D. greater than 0.3, and possibly as high as 2.0. This new solution would be able to reduce the intensity of the object beam sufficiently to make it comparable with the reference beam intensity. If this were achieved, the contrast, or visibility of the fringes would be better, and the interferogram could be used to diagnose the aberrations in the laser beam front. Then the cause of the aberrations could be fixed. This would result in a near-perfect laser front. If this were achieved, then it is possible that laser fusion could be made more efficient and possibly used as an energy source.

  1. Trace Elements in Ovaries: Measurement and Physiology.

    PubMed

    Ceko, Melanie J; O'Leary, Sean; Harris, Hugh H; Hummitzsch, Katja; Rodgers, Raymond J

    2016-04-01

    Traditionally, research in the field of trace element biology and human and animal health has largely depended on epidemiological methods to demonstrate involvement in biological processes. These studies were typically followed by trace element supplementation trials or attempts at identification of the biochemical pathways involved. With the discovery of biological molecules that contain the trace elements, such as matrix metalloproteinases containing zinc (Zn), cytochrome P450 enzymes containing iron (Fe), and selenoproteins containing selenium (Se), much of the current research focuses on these molecules, and, hence, only indirectly on trace elements themselves. This review focuses largely on two synchrotron-based x-ray techniques: X-ray absorption spectroscopy and x-ray fluorescence imaging that can be used to identify the in situ speciation and distribution of trace elements in tissues, using our recent studies of bovine ovaries, where the distribution of Fe, Se, Zn, and bromine were determined. It also discusses the value of other techniques, such as inductively coupled plasma mass spectrometry, used to garner information about the concentrations and elemental state of the trace elements. These applications to measure trace elemental distributions in bovine ovaries at high resolutions provide new insights into possible roles for trace elements in the ovary. PMID:26864198

  2. Monitoring of the environmental pollution by trace element analysis in tree-rings using synchrotron radiation total reflection X-ray fluorescence

    NASA Astrophysics Data System (ADS)

    de Vives, Ana Elisa Sirito; Moreira, Silvana; Brienza, Sandra Maria Boscolo; Medeiros, Jean Gabriel Silva; Filho, Mário Tomazello; Zucchi, Orghêda Luíza Araújo Domingues; Filho, Virgílio Franco do Nascimento

    2006-11-01

    This paper aims to study the environmental pollution in the tree development, in order to evaluate its use as bioindicator in urban and country sides. The sample collection was carried out in Piracicaba city, São Paulo State, which presents high level of environmental contamination in water, soil and air, due to industrial activities, vehicles combustion, sugar-cane leaves burning in the harvesting, etc. The species Caesalpinia peltophoroides ("Sibipiruna") was selected because it is widely used in urban forestation. Synchrotron Radiation Total Reflection X-ray Fluorescence technique (SR-TXRF) was employed to identify and quantify the elements and metals of nutritional and toxicological importance in the wood samples. The analysis was performed in the Brazilian Synchrotron Light Source Laboratory, using a white beam for excitation and a Si(Li) detector for X-ray detection. In several samples, P, K, Ca, Ti, Fe, Sr, Ba and Pb were quantified. The K/Ca, K/P and Pb/Ca ratios were found to decrease towards the bark.

  3. Determination of trace rare earth elements by X-ray fluorescence spectrometry after preconcentration on a new chelating resin loaded with thorin.

    PubMed

    De Vito, I E; Masi, A N; Olsina, R A

    1999-07-12

    A very stable chelating resin was prepared by adsorption of (o-[3,6-disulfo-2-hidroxy-1-naphthylazo]-benzenearsonic acid) (thorin) on a macroporous resin Amberlite XAD-7. The optimal conditions for preparing it were obtained through the study of the adsorption properties of the resin and the thermodynamic quantities of the adsorption processes. Likewise, the behavior of the loaded resin with the rare earth elements (REE) were studied (pH of retention, sorption kinetics, etc). The conditions to prepare a thin film with this system were also evaluated. The loaded resin was successfully used for the separation and preconcentration of Sm(III), Eu(III) and Gd(III) prior to their determination by X-ray fluorescence (XRF) spectrometry. The preconcentration factor obtained was 500 and the concentrations at low detection limit were 13.8, 17 and 15.7 microg l(-1) for Sm, Eu and Gd, respectively. PMID:18967670

  4. Distribution of trace elements in the mammalian retina and cornea by use of particle-induced X-ray emission (PIXE): localisation of zinc does not correlate with that of metallothioneins.

    PubMed

    Ugarte, Marta; Grime, Geoffrey W; Osborne, Neville N

    2014-02-01

    Proton-induced X-ray emission (PIXE) in combination with 3D depth profiling with Rutherford backscattering spectrometry (RBS) was used to establish the distribution and concentration of trace elements within individual corneal and retinal areas in frozen sections from adult male Wistar rats (n = 6). The distribution of endogenous trace elements in the cornea and retina is non-homogenous. The most abundant metal in the cornea is calcium followed by zinc. Iron and copper are present in small amounts localised particularly to the epithelium. Iron is also identified in keratocytes. Relatively high levels of calcium occur in the corneal epithelial cell bodies. Zinc has a wide intense distribution across the corneal epithelium (with greater levels in the basal part) and posterior stroma. In the retina, zinc is the most common metal followed by iron and copper. Relatively high levels of zinc exist in the retinal pigment epithelium (RPE), photoreceptor inner segments (RIS) and inner nuclear layer (INL). Chelatable zinc was localised with fluorescent TSQ in the RPE, RIS and plexiform layers. It is interesting to note that the highest levels of total zinc and the greatest intensity of chelatable zinc staining do not coincide. In the RPE and corneal epithelium, zinc co-localised with the zinc-containing metallothioneins (MT). However, there was a clear mismatch between the localisation of the most intense levels of zinc in the neuroretina (i.e. INL) and corneal posterior stroma with that reported for MT. For example, the presence of zinc is not particularly associated with the retinal ganglion cells, retinal area that contains MTs in significant amounts. While high amounts of zinc are present in the INL and corneal posterior stroma, which are largely devoid of MTs. This probably represents pools of static, catalytic and structural zinc associated with substances other than the MTs. PMID:24226809

  5. Using dual-energy x-ray imaging to enhance automated lung tumor tracking during real-time adaptive radiotherapy

    SciTech Connect

    Menten, Martin J. Fast, Martin F.; Nill, Simeon; Oelfke, Uwe

    2015-12-15

    Purpose: Real-time, markerless localization of lung tumors with kV imaging is often inhibited by ribs obscuring the tumor and poor soft-tissue contrast. This study investigates the use of dual-energy imaging, which can generate radiographs with reduced bone visibility, to enhance automated lung tumor tracking for real-time adaptive radiotherapy. Methods: kV images of an anthropomorphic breathing chest phantom were experimentally acquired and radiographs of actual lung cancer patients were Monte-Carlo-simulated at three imaging settings: low-energy (70 kVp, 1.5 mAs), high-energy (140 kVp, 2.5 mAs, 1 mm additional tin filtration), and clinical (120 kVp, 0.25 mAs). Regular dual-energy images were calculated by weighted logarithmic subtraction of high- and low-energy images and filter-free dual-energy images were generated from clinical and low-energy radiographs. The weighting factor to calculate the dual-energy images was determined by means of a novel objective score. The usefulness of dual-energy imaging for real-time tracking with an automated template matching algorithm was investigated. Results: Regular dual-energy imaging was able to increase tracking accuracy in left–right images of the anthropomorphic phantom as well as in 7 out of 24 investigated patient cases. Tracking accuracy remained comparable in three cases and decreased in five cases. Filter-free dual-energy imaging was only able to increase accuracy in 2 out of 24 cases. In four cases no change in accuracy was observed and tracking accuracy worsened in nine cases. In 9 out of 24 cases, it was not possible to define a tracking template due to poor soft-tissue contrast regardless of input images. The mean localization errors using clinical, regular dual-energy, and filter-free dual-energy radiographs were 3.85, 3.32, and 5.24 mm, respectively. Tracking success was dependent on tumor position, tumor size, imaging beam angle, and patient size. Conclusions: This study has highlighted the influence of

  6. Epidemic contact tracing via communication traces.

    PubMed

    Farrahi, Katayoun; Emonet, Rémi; Cebrian, Manuel

    2014-01-01

    Traditional contact tracing relies on knowledge of the interpersonal network of physical interactions, where contagious outbreaks propagate. However, due to privacy constraints and noisy data assimilation, this network is generally difficult to reconstruct accurately. Communication traces obtained by mobile phones are known to be good proxies for the physical interaction network, and they may provide a valuable tool for contact tracing. Motivated by this assumption, we propose a model for contact tracing, where an infection is spreading in the physical interpersonal network, which can never be fully recovered; and contact tracing is occurring in a communication network which acts as a proxy for the first. We apply this dual model to a dataset covering 72 students over a 9 month period, for which both the physical interactions as well as the mobile communication traces are known. Our results suggest that a wide range of contact tracing strategies may significantly reduce the final size of the epidemic, by mainly affecting its peak of incidence. However, we find that for low overlap between the face-to-face and communication interaction network, contact tracing is only efficient at the beginning of the outbreak, due to rapidly increasing costs as the epidemic evolves. Overall, contact tracing via mobile phone communication traces may be a viable option to arrest contagious outbreaks. PMID:24787614

  7. Parametric Trace Slicing

    NASA Technical Reports Server (NTRS)

    Rosu, Grigore (Inventor); Chen, Feng (Inventor); Chen, Guo-fang; Wu, Yamei; Meredith, Patrick O. (Inventor)

    2014-01-01

    A program trace is obtained and events of the program trace are traversed. For each event identified in traversing the program trace, a trace slice of which the identified event is a part is identified based on the parameter instance of the identified event. For each trace slice of which the identified event is a part, the identified event is added to an end of a record of the trace slice. These parametric trace slices can be used in a variety of different manners, such as for monitoring, mining, and predicting.

  8. Comparison of organ dose and dose equivalent using ray tracing of male and female Voxel phantoms to space flight phantom torso data

    NASA Astrophysics Data System (ADS)

    Kim, Myung-Hee; Qualls, Garry; Slaba, Tony; Cucinotta, Francis A.

    Phantom torso experiments have been flown on the space shuttle and International Space Station (ISS) providing validation data for radiation transport models of organ dose and dose equivalents. We describe results for space radiation organ doses using a new human geometry model based on detailed Voxel phantoms models denoted for males and females as MAX (Male Adult voXel) and Fax (Female Adult voXel), respectively. These models represent the human body with much higher fidelity than the CAMERA model currently used at NASA. The MAX and FAX models were implemented for the evaluation of directional body shielding mass for over 1500 target points of major organs. Radiation exposure to solar particle events (SPE), trapped protons, and galactic cosmic rays (GCR) were assessed at each specific site in the human body by coupling space radiation transport models with the detailed body shielding mass of MAX/FAX phantom. The development of multiple-point body-shielding distributions at each organ site made it possible to estimate the mean and variance of space dose equivalents at the specific organ. For the estimate of doses to the blood forming organs (BFOs), active marrow distributions in adult were accounted at bone marrow sites over the human body. We compared the current model results to space shuttle and ISS phantom torso experiments and to calculations using the CAMERA model.

  9. Comparison of Organ Dose and Dose Equivalent Using Ray Tracing of Male and Female Voxel Phantoms to Space Flight Phantom Torso Data

    NASA Technical Reports Server (NTRS)

    Kim, Myung-Hee Y.; Qualls, Garry D.; Cucinotta, Francis A.

    2008-01-01

    Phantom torso experiments have been flown on the space shuttle and International Space Station (ISS) providing validation data for radiation transport models of organ dose and dose equivalents. We describe results for space radiation organ doses using a new human geometry model based on detailed Voxel phantoms models denoted for males and females as MAX (Male Adult voXel) and Fax (Female Adult voXel), respectively. These models represent the human body with much higher fidelity than the CAMERA model currently used at NASA. The MAX and FAX models were implemented for the evaluation of directional body shielding mass for over 1500 target points of major organs. Radiation exposure to solar particle events (SPE), trapped protons, and galactic cosmic rays (GCR) were assessed at each specific site in the human body by coupling space radiation transport models with the detailed body shielding mass of MAX/FAX phantom. The development of multiple-point body-shielding distributions at each organ site made it possible to estimate the mean and variance of space dose equivalents at the specific organ. For the estimate of doses to the blood forming organs (BFOs), active marrow distributions in adult were accounted at bone marrow sites over the human body. We compared the current model results to space shuttle and ISS phantom torso experiments and to calculations using the CAMERA model.

  10. Trace Chemistry

    NASA Technical Reports Server (NTRS)

    Radhakrishnan, Krishnan; Whitefield, Philip

    1999-01-01

    The goals of the trace chemistry group were to identify the processes relevant to aerosol and aerosol precursor formation occurring within aircraft gas turbine engines; that is, within the combustor, turbine, and nozzle. The topics of discussion focused on whether the chemistry of aerosol formation is homogeneous or heterogeneous; what species are important for aerosol and aerosol precursor formation; what modeling/theoretical activities to pursue; what experiments to carry out that both support modeling activities and elucidate fundamental processes; and the role of particulates in aerosol and aerosol precursor formation. The consensus of the group was that attention should be focused on SO2, SO3, and aerosols. Of immediate concern is the measurement of the concentration of the species SO3, SO2, H2SO4 OH, HO2, H2O2, O, NO, NO2, HONO, HNO3, CO, and CO2 and particulates in various engines, both those currently in use and those in development. The recommendation was that concentration measurements should be made at both the combustor exit and the engine exit. At each location the above species were classified into one of four categories of decreasing importance, Priority I through IV, as follows: Combustor exit: Priority I species - SO3:SO2 ratio, SO3, SO2, and particulates; Priority II species: OH and O; Priority III species - NO and NO2; and Priority IV species - CO and CO2. For the Engine exit: Priority I species - SO3:SO2 ratio, SO3, SO2,H2SO4, and particulates; Priority II species: OH,HO2, H2O2, and O; Priority III species - NO, NO2, HONO, and HNO3; and Priority IV species - CO and CO2. Table I summarizes the anticipated concentration range of each of these species. For particulate matter, the quantities of interest are the number density, size distribution, and composition. In order to provide data for validating multidimensional reacting flow models, it would be desirable to make 2-D, time-resolved measurements of the concentrations of the above species and

  11. Low-mAs X-ray CT image reconstruction by adaptive-weighted TV-constrained penalized re-weighted least-squares

    PubMed Central

    Liu, Yan; Ma, Jianhua; Zhang, Hao; Wang, Jing; Liang, Zhengrong

    2014-01-01

    Background The negative effects of X-ray exposure, such as inducing genetic and cancerous diseases, has arisen more attentions. Objective This paper aims to investigate a penalized re-weighted least-square (PRWLS) strategy for low-mAs X-ray computed tomography image reconstruction by incorporating an adaptive weighted total variation (AwTV) penalty term and a noise variance model of projection data. Methods An AwTV penalty is introduced in the objective function by considering both piecewise constant property and local nearby intensity similarity of the desired image. Furthermore, the weight of data fidelity term in the objective function is determined by our recent study on modeling variance estimation of projection data in the presence of electronic background noise. Results The presented AwTV-PRWLS algorithm can achieve the highest full-width-at-half-maximum (FWHM) measurement, for data conditions of (1) full-view 10mA acquisition and (2) sparse-view 80mA acquisition. In comparison between the AwTV/TV-PRWLS strategies and the previous reported AwTV/TV-projection onto convex sets (AwTV/TV-POCS) approaches, the former can gain in terms of FWHM for data condition (1), but cannot gain for the data condition (2). Conclusions In the case of full-view 10mA projection data, the presented AwTV-PRWLS shows potential improvement. However, in the case of sparse-view 80mA projection data, the AwTV/TV-POCS shows advantage over the PRWLS strategies. PMID:25080113

  12. X-ray fluorescence analysis of long-term changes in the levels and distributions of trace elements in the rat brain following mechanical injury

    PubMed Central

    Sarapata, A.; Janeczko, K.; Stegowski, Z.; Appel, K.; Setkowicz, Z.

    2010-01-01

    This paper describes the results of the application of X-ray fluorescence microscopy to the qualitative, topographic and quantitative elemental analysis of nervous tissue from rats with neocortical brain injury. The tissue samples were analyzed with a 15 μm beam defined by the size of the polycapillary focus. Raster scanning of the samples generated 2D cartographies, revealing the distributions of elements such as P, S, Cl, K, Ca, Fe, Cu, and Zn. Special emphasis was placed on the analysis of the areas neighboring the lesion site and the hippocampal formation tissue. The results obtained for rats with mechanical brain injuries were compared with those recorded for controls and animals with pilocarpine-induced seizures. There were no significant differences in the elemental compositions of gray and white matter between injured and uninjured brain hemispheres. A higher level of Ca was observed in the gray matter of both of the hemispheres in brains with neocortical injuries. A similar relation was noticed for Fe in the white matter. A comparative study of hippocampal formation tissue showed a statistically significant decrease in the mass per unit area of P in the dentate gyrus (DG) and the hilus (H) of DG for animals with brain lesions in comparison with the control group. Analogous relations were found for Cu in the DG and Zn in sector 3 of Ammon’s horn (CA3) and the DG. It is important to note that identical changes in the same areas were observed for animals with pilocarpine-induced seizures in our previous study. PMID:21049302

  13. The impact of data assimilation of ground-based GPS precipitable water vapor to numerical weather prediction model on estimation of ray-traced atmospheric slant delays

    NASA Astrophysics Data System (ADS)

    Ichikawa, R.; Hobiger, T.; Shoji, Y.; Miyauchi, Y.

    2012-12-01

    The ''KAshima RAytracing Tools (KARAT)'' is capable of calculating total slant delays and ray-bending angles considering real atmospheric phenomena. One advantage of KARAT is that the reduction of atmospheric path delay will become more accurate each time the numerical weather model is improved. On October 27, 2009 the JMA started data assimilation of zenith wet delays obtained by the GPS Earth Observation Network System (GEONET) operated by Geospatial Information Authority of Japan (GSI) for meso-scale NWP model. The improved NWP model data assimilating the GPS PWV data has the potential to correct the atmospheric path delay more precisely. Meteorological Research Institute (MRI) of Japan has evaluated the impact of ground-based GPS precipitable water vapor (GPS PWV) derived from the GEONET on meso-scale NWP model under the localized heavy rainfall event in Tokyo, Japan on 5 August 2008. A terrific thunderstorm occurred across the Kanto area of Japan, and it caused flooding in downtown Tokyo. During the event, the rainfall intensity increased to over 100 mm per hour within thirty minutes. We have assessed the impacts of GPS PWV assimilation into the NWP model on the KARAT correction by comparisons of the precise point positioning (PPP) solutions. In the nationwide scale of Japan, the short time repeatability of the PPP results for both horizontal and height positions applying KARAT correction through the MRI NWP model with GPS PWV assimilation are about several percent better than that through the conventional MRI NPW model w/o GPS PWV assimilation. In addition we are now investigating the impact of GPS PWV data assimilation in more detail. We will present the updated results of the comparison study.

  14. High-energy polarized-beam energy-dispersive X-ray fluorescence analysis combined with activated thin layers for cadmium determination at trace levels in complex environmental liquid samples.

    PubMed

    Marguí, Eva; Fontàs, Clàudia; Van Meel, Katleen; Van Grieken, René; Queralt, Ignasi; Hidalgo, Manuela

    2008-04-01

    In this paper, we describe a new method for trace level Cd determination in complex environmental liquid samples. Thin layers activated with the extractant Aliquat 336 were prepared either by direct impregnation of commercial polymeric supports or by physical inclusion in a cellulose triacetate matrix, and both were effectively used to collect Cd present at low concentration in different aqueous matrixes. Quantitation of Cd contained in the thin layers was performed by high-energy polarized-beam energy-dispersive X-ray fluorescence. The effects of various experimental parameters such as layer composition, equilibration time, and instrumental conditions have been investigated. The analysis of different impregnated layers contacted with solutions ranging from 5 to 8000 microg L-1 Cd showed a linear response between the Cd concentration in the aqueous solutions and the metal present in the thin layer, with a detection limit of 0.7 microg L-1. The accuracy of the proposed method was confirmed by analyzing spiked seawater samples and a synthetic water sample containing, besides Cd, high amounts of other metal pollutants such as Ni, Cu, and Pb. The attained results were comparable to those obtained by anodic stripping voltammetry or inductively coupled plasma spectrometry. PMID:18327919

  15. In situ trace element microanalysis

    NASA Technical Reports Server (NTRS)

    Burnett, D. S.; Woolum, D. S.

    1983-01-01

    The use of particle-track-radiography and X-ray- fluorescence techniques in the in situ measurement of trace (less than 1000 ppm) elements in single mineral phases of polished sections is surveyed, and examples of their application to ordinary, carbonaceous and enstatite chondrites are provided. Radiographic methods surveyed include fission-track radiography (for U, Th, and Pu-244), alpha radiography using nuclear reactions (for Li and B), alpha autoradiography (for Bi and Pb), and beta autoradiography (for several elements in synthetic or biological samples). Two X-ray-fluorescence methods are compared: (1) photon-induced X-ray emission (PIXE), and (2) the potential use of synchrotron radiation. The latter is shown to allow much greater sensitivity than current PIXE technology and a much broader range of elements than particle-track radiography: the ppm analysis of 10-micron grains for all elements heavier than Na. These advantages are seen as balancing the high cost of accelerator use.

  16. Crystallization and X-ray Crystallographic Analysis of the Adhesive SpaC Pilin Subunit in the SpaCBA Pilus of Gut-adapted Lactobacillus rhamnosus GG.

    PubMed

    Kant, Abhiruchi; von Ossowski, Ingemar; Palva, Airi; Krishnan, Vengadesan

    2016-01-01

    Gram-positive Lactobacillus rhamnosus GG, a gut-adapted commensalic (and probiotic) strain, is known to express sortase-assembled pili on its cell surface. These SpaCBA-called pili consist of three different types of building blocks; the SpaA backbone-pilin subunit and the SpaB and SpaC ancillary pilins. SpaC is a relatively large (~90kDa) multi-domain fimbrial adhesin, and while it is located primarily at the SpaCBA pilus tip, occasionally, it can also be detected throughout the length of pilus backbone. Functionally, SpaC mainly accounts for SpaCBA pilus-mediated interactions with intestinal mucus, collagen, and human gut epithelial cells. Moreover, SpaC adhesiveness is also perceived to have a causal relationship with SpaCBA pilus-induced host-cell immune responses. In order to improve the mechanistic understanding of SpaC and its adhesive properties by structural investigation, we purified and successfully crystallized a recombinant construct of the near full-length SpaC protein (residues 36-856) in the presence of magnesium ions. X-ray diffraction data were collected to 2.6 Å resolution. The SpaC crystal belongs to the space group P21212 with unit cell parameters a = 116.5, b = 128.3, c = 136.5 Å and contains two molecules in the asymmetric unit. Presence of conserved metal ion-dependent adhesion site containing von Willebrand factor type A domain suggests its likely role in the function of SpaC. PMID:26732247

  17. Ray tracing of Jovian low frequency radiation

    NASA Technical Reports Server (NTRS)

    Six, N. Frank

    1987-01-01

    The radio emission from Jupiter in the decametric range (2 to 40 MHz) has been studied for three decades. It is known that this emission is correlated with particular longitude regions on the planet and with the position of the satellite Io. The Planetary Radio Astronomy experiment on the Voyager 1 and 2 spacecraft observed this emission, obtaining valuable new information. The objectives of this study are as follows: (1) calculate raypaths for decametric wavelength radiation in Jupiter's magnetosphere; (2) compare the model-dependent raypaths with the Voyager observations; and (3) deduce characteristics of the source regions and the influence of propagation effects.

  18. An Interactive Instruction Session in Ray Tracing

    ERIC Educational Resources Information Center

    Finn, Edward J.

    1973-01-01

    Describes three interactive programs in the general physics area which are prepared on time-shared facilities to assist a student to self-test himself for an understanding of light reflection problems. Examples of computer printout are given. (CC)

  19. Long Trace Profiler survey results

    SciTech Connect

    Irick, Steve.

    1999-07-01

    Today the Long Trace Profiler (LTP) is widely accepted as a viable way to measure X-ray mirrors, and at some institutions is the only instrument available for measuring long, high-curvature aspheres. Although some questions of absolute accuracy over the entire LTP measurement range remain unanswered, a comparison of LTPs can still be made to assess measurement variation. Recently a round robin survey of some LTPs within the United States has been made using a single set of mirrors. These mirrors were used to characterize the performance of an LTP over its advertised range of operation. The results of this survey are presented here.

  20. Biological trace element measurements using synchrotron radiation

    SciTech Connect

    Giauque, R.D.; Jaklevic, J.M.; Thompson, A.C.

    1985-07-01

    The feasibility of performing x-ray fluorescence trace element determinations at concentrations substantially below the ppM level for biological materials is demonstrated. Conditions for achieving optimum sensitivity were ascertained. Results achieved for five standard reference materials were, in most cases, in excellent agreement with listed values. Minimum detectable limits of 20 ppM were measured for most elements.