Kolkoori, S R; Rahman, M-U; Chinta, P K; Ktreutzbruck, M; Rethmeier, M; Prager, J
2013-02-01
Ultrasound propagation in inhomogeneous anisotropic materials is difficult to examine because of the directional dependency of elastic properties. Simulation tools play an important role in developing advanced reliable ultrasonic non destructive testing techniques for the inspection of anisotropic materials particularly austenitic cladded materials, austenitic welds and dissimilar welds. In this contribution we present an adapted 2D ray tracing model for evaluating ultrasonic wave fields quantitatively in inhomogeneous anisotropic materials. Inhomogeneity in the anisotropic material is represented by discretizing into several homogeneous layers. According to ray tracing model, ultrasonic ray paths are traced during its energy propagation through various discretized layers of the material and at each interface the problem of reflection and transmission is solved. The presented algorithm evaluates the transducer excited ultrasonic fields accurately by taking into account the directivity of the transducer, divergence of the ray bundle, density of rays and phase relations as well as transmission coefficients. The ray tracing model is able to calculate the ultrasonic wave fields generated by a point source as well as a finite dimension transducer. The ray tracing model results are validated quantitatively with the results obtained from 2D Elastodynamic Finite Integration Technique (EFIT) on several configurations generally occurring in the ultrasonic non destructive testing of anisotropic materials. Finally, the quantitative comparison of ray tracing model results with experiments on 32mm thick austenitic weld material and 62mm thick austenitic cladded material is discussed.
Ray tracing of Electron Bernstein Waves in 2D for C-2 Equilibrium
NASA Astrophysics Data System (ADS)
Trask, E.; Kruszelnicki, J.; Harvey, R. W.; Petrov, Yu.; TAE Team
2013-10-01
Ray propagation in the electron cyclotron range of frequencies (ECRF) has been studied for simulated two dimensional equilibria on the C-2 device. Studies have been performed using the Genray ray tracing code, with modifications to allow ray trajectories on open magnetic flux surfaces. Primary studies are focused on Electron Bernstein Wave (EBW) coupling mechanisms to study the potential for microwave heating of Field Reversed Configurations (FRC).
NASA Technical Reports Server (NTRS)
Poli, P.; Joiner, J.
2003-01-01
Global Positioning System (GPS) Radio Occultations (RO) bending angles and refractivity data characterize mostly the vertical structure of the Earth's atmosphere. We answer the question whether proper simulation of GPS RO data for data assimilation can be obtained with one-dimensional vertical operators, or if accounting also for horizontal atmospheric structures via ray-tracing makes a positive difference when compared with real data. We present a detailed implementation of a geometrical optics multi-plane two-dimensional (2D) ray-tracing as an observation operator to simulate GPS RO bending angles and refractivities within the Finite Volume Data Assimilation System (FVDAS). Comparisons of the outputs of that 2D observation operator with those of simpler ID observation operators are used to generate estimates of errors induced by neglecting tangent point drift (TPD) and horizontal gradients (HG). These error estimates are then confronted with errors estimates derived using 6335 real CHAMP and SAC-C occultations. The agreement for TPD-induced (HG-induced) errors is remarkably positive at altitudes 10-30 km (below 10 km). Comparisons in bending angles O - B STD of the outputs of the multi-plane 2D ray-tracer with those of a vertical Abel transform show reductions of about 8% of the usual O - B bending angle STD due to TPD in the stratosphere (3% due to HG, in the troposphere only). In terms of refractivity, the O - B STD reductions are about 1520% for TPD and 3-5% for HG in the same regions. These reductions are obtained using either 6-hour forecasts or analyses as backgrounds, and using Geometrical Optics (GO) or Canonical Transform (CT) data.
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)
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
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)
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)
NASA Technical Reports Server (NTRS)
Dorband, John E.
1987-01-01
Generating graphics to faithfully represent information can be a computationally intensive task. A way of using the Massively Parallel Processor to generate images by ray tracing is presented. This technique uses sort computation, a method of performing generalized routing interspersed with computation on a single-instruction-multiple-data (SIMD) computer.
Computer program for optical systems ray tracing
NASA Technical Reports Server (NTRS)
Ferguson, T. J.; Konn, H.
1967-01-01
Program traces rays of light through optical systems consisting of up to 65 different optical surfaces and computes the aberrations. For design purposes, paraxial tracings with astigmation and third order tracings are provided.
Ray tracing planetary radio emissions
NASA Technical Reports Server (NTRS)
Green, James L.
1988-01-01
Planetary ray tracing calculations of free escaping electromagnetic waves are presented, with special attention given to calculations of the earth's auroral kilometric and continuum radiations and of the Jovian decametric and kilometric radiation. The technique is used to study the composition and propagation effects causing multiion resonances and shadow zones. Although results obtained for Jovian broadband kilometric radiation have been used to estimate the location of the source region, no unique solutions are obtained.
2-D soft x-ray arrays in the EAST
NASA Astrophysics Data System (ADS)
Chen, Kaiyun; Xu, Liqing; Hu, Liqun; Duan, Yanmin; Li, Xueqin; Yuan, Yi; Mao, Songtao; Sheng, Xiuli; Zhao, Jinlong
2016-06-01
A high spatial and temporal resolution soft x-ray (SXR) imaging diagnostic has been installed in EAST for the study of magnetohydrodynamics activities and core high-Z impurity transport. Up to 122 lines of sight view the poloidal plasma from three directions (two up-down symmetrical horizontal arrays and one vertical array), which renders the diagnostic able to provide detailed tomographic reconstructions under various conditions. Fourier-Bessel method based on flux coordinates was employed for 2-D SXR tomographic reconstruction. Examples of several events measured by SXR diagnostic in EAST are shown, namely the crash patterns of sawtooth, periodical burst of edge localized modes, and the transport of high-Z intrinsic impurities.
Gómez-Correa, J E; Coello, V; Garza-Rivera, A; Puente, N P; Chávez-Cerda, S
2016-03-10
Ray tracing in spherical Luneburg lenses has always been represented in 2D. All propagation planes in a 3D spherical Luneburg lens generate the same ray tracing, due to its radial symmetry. A geometry without radial symmetry generates a different ray tracing. For this reason, a new ray tracing method in 3D through spherical and elliptical Luneburg lenses using 2D methods is proposed. The physics of the propagation is shown here, which allows us to make a ray tracing associated with a vortex beam. A 3D ray tracing in a composite modified Luneburg lens that represents the human eye lens is also presented.
Gómez-Correa, J E; Coello, V; Garza-Rivera, A; Puente, N P; Chávez-Cerda, S
2016-03-10
Ray tracing in spherical Luneburg lenses has always been represented in 2D. All propagation planes in a 3D spherical Luneburg lens generate the same ray tracing, due to its radial symmetry. A geometry without radial symmetry generates a different ray tracing. For this reason, a new ray tracing method in 3D through spherical and elliptical Luneburg lenses using 2D methods is proposed. The physics of the propagation is shown here, which allows us to make a ray tracing associated with a vortex beam. A 3D ray tracing in a composite modified Luneburg lens that represents the human eye lens is also presented. PMID:26974795
Jannaud, L.R.
1994-12-31
In the SMART method, exact traveltimes, used as input of reflection tomography, are computed by tracing rays that are reflected on interpreted migrated events. Since picking migrated events is easier in common offset migrated images than in common shot migrated images, a common offset raytracing has been developed. It is based on a continuation method in the source position-shooting angle domain. It consists in following in this domain iso-offset lines and determining the points of these lines corresponding to the actual sources. It allows the user to compute all the arrivals even for complex media at a low computational cost.
Infrasound ray tracing models for real events
NASA Astrophysics Data System (ADS)
Averbuch, Gil; Applbaum, David; Price, Colin; Ben Horin, Yochai
2015-04-01
Infrasound ray tracing models for real events C. Price1, G. Averbuch1, D. Applbaum1, Y. Ben Horin2 (1) Department of Geosciences, Tel Aviv University, Israel (2) Soreq Nuclear Research Center, Yavne, Israel Ray tracing models for infrasound propagation require two atmospheric parameters: the speed of sound profile and the wind profile. The usage of global atmospheric models for the speed of sound and wind profiles raises a fundamental question: can these models provide accurate results for modeling real events that have been detected by the infrasound arrays? Moreover, can these models provide accurate results for events that occurred during extreme weather conditions? We use 2D and 3D ray tracing models based on a modified Hamiltonian for a moving medium. Radiosonde measurements enable us to update the first 20 km of both speed of sound and wind profiles. The 2009 and 2011 Sayarim calibration experiments in Israel served us as a test for the models. In order to answer the question regarding the accuracy of the model during extreme weather conditions, we simulate infrasound sprite signals that were detected by the infrasound array in Mt. Meron, Israel. The results from modeling the Sayarim experiment provided us sufficient insight to conclude that ray tracing modeling can provide accurate results for real events that occurred during fair weather conditions. We conclude that the time delay in the model of the 2009 experiment is due to lack of accuracy in the wind and speed of sound profiles. Perturbed profiles provide accurate results. Earlier arrivals in 2011 are a result of the assumption that the earth is flat (no topography) and the use of local radiosonde measurements for the entire model. Using local radiosonde measurements only for part of the model and neglecting them on other parts prevents the early arrivals. We were able to determine which sprite is the one that got detected in the infrasound array as well as providing a height range for the sprite
Seismic ray tracing using linear traveltime interpolation
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.
Reverse ray tracing for transformation optics.
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.
Reverse ray tracing for transformation optics.
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
Ray tracing on distributed memory parallel systems
NASA Technical Reports Server (NTRS)
Jensen, David W.; Reed, Daniel A.
1990-01-01
Among the many techniques in computer graphics, ray tracing is prized because it can render realistic images, albeit at great computational expense. In this note, the performance of several approaches to ray tracing on a distributed memory parallel system is evaluated. A set of performance instrumentation tools and their associated visualization software are used to identify the underlying causes of performance differences.
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.
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.
Development of 2-D-MAX-DOAS and retrievals of trace gases and aerosols optical properties
NASA Astrophysics Data System (ADS)
Ortega, Ivan
Air pollution is a major problem worldwide that adversely a_ects human health, impacts ecosystems and climate. In the atmosphere, there are hundreds of important compounds participating in complex atmospheric reactions linked to air quality and climate. Aerosols are relevant because they modify the radiation balance, a_ect clouds, and thus Earth albedo. The amount of aerosol is often characterized by the vertical integral through the entire height of the atmosphere of the logarithm fraction of incident light that is extinguished called Aerosol Optical Depth (AOD). The AOD at 550 nm (AOD550) over land is 0.19 (multi annual global mean), and that over oceans is 0.13. About 43 % of the Earth surface shows AOD550 smaller than 0.1. There is a need for measurement techniques that are optimized to measure aerosol optical properties under low AOD conditions, sample spatial scales that resemble satellite ground-pixels and atmospheric models, and help integrate remote sensing and in-situ observations to obtain optical closure on the effects of aerosols and trace gases in our changing environment. In this work, I present the recent development of the University of Colorado two dimensional (2-D) Multi-AXis Differential Optical Absorption Spectroscopy (2-D-MAX-DOAS) instrument to measure the azimuth and altitude distribution of trace gases and aerosol optical properties simultaneously with a single instrument. The instrument measures solar scattered light from any direction in the sky, including direct sun light in the hyperspectral domain. In Chapter 2, I describe the capabilities of 2-D measurements in the context of retrievals of azimuth distributions of nitrogen dioxide (NO2), formaldehyde (HCHO), and glyoxal (CHOCHO), which are precursors for tropospheric O3 and aerosols. The measurements were carried out during the Multi-Axis DOAS Comparison campaign for Aerosols and Trace gases (MAD-CAT) campaign in Mainz, Germany and show the ability to bridge spatial scales to
Microsecond time-resolved 2D X-ray imaging
NASA Astrophysics Data System (ADS)
Sarvestani, A.; Sauer, N.; Strietzel, C.; Besch, H. J.; Orthen, A.; Pavel, N.; Walenta, A. H.; Menk, R. H.
2001-06-01
A method is presented which allows to take two-dimensional X-ray images of repetitive processes with recording times in the sub-microsecond range. Various measurements have been performed with a recently introduced novel two-dimensional single photon counter which has been slightly modified in order to determine the exact arrival time of each detected photon. For this purpose a special clock signal is synchronized with the process and is digitized contemporaneously with each event. This technique can be applied even with rate limited detectors and low flux sources, since—unlike in conventional methods, where chopped beams or gated read out electronics are used—all photons are used for the image formation. For the measurements, rapidly moving mechanical systems and conventional X-ray sources have been used, reaching time resolutions of some 10 μs. The technique presented here opens a variety of new biological, medical and industrial applications which will be discussed. As a first application example, three dimensional tomographic reconstructions of rapidly rotating objects (4000 turns/min) are presented.
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 ...
Ray tracing of Jovian kilometric radiation
NASA Technical Reports Server (NTRS)
Green, J. L.; Gurnett, D. A.
1980-01-01
Results of computer ray tracing of Jovian kilometric radiation from 56.2 kHz to 1 MHz in a model Jovian magnetosphere with an Io torus are presented. Ray tracing calculations indicate that the Io torus presents a propagation barrier to the radiation and that the Jovian kilometric radiation must be generated in the L-O mode from a source near Jupiter on field lines passing through the Io torus. One effect of the Io torus is to refract the rays away from the magnetic equator forming a shadow zone at radial distances beyond the torus. In general, at radial distances greater than 10 Jovian radii, as the wave frequency increases (greater than 200 kHz) so does the magnetic latitude of the shadow zone. These and other features of the ray tracing calculations are in good qualitative agreement with the observations from the plasma wave receiver and planetary radio astronomy experiment on board both Voyagers 1 and 2.
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).
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.
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.
2D mapping of LA-ICPMS trace element distributions using R
NASA Astrophysics Data System (ADS)
Rittner, Martin; Müller, Wolfgang
2012-05-01
A new add-on package (LAICPMS) for the R language for statistical computing is presented, which greatly facilitates data reduction and visualisation (single tracks and 2D element maps) of laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) data. The package determines many input parameters automatically and is easy to use. We present major and trace element distribution maps of natural calcite samples, processed using LAICPMS. Data processing from raw data to presented graphics takes only a few minutes. The empirical cumulative density function (ECDF) is used for optimised colour coding of the maps rather than linear or logarithmic scale, making a maximum of element-specific detail visible. For preprocessing, several different smoothing algorithms were evaluated and can be chosen by the user; for the presented data, a simple running median/running average was chosen. Typical data analysis is performed via short, easy-to-understand script files, and results can be used for further analyses within R. Owing to other R add-on packages utilised, the results can be output either numerically or as high-quality graphics in a wide range of file formats. Inheriting from its host environment R, the package is open-source software and freely available for all major computer platforms.
Ray tracing study for non-imaging daylight collectors
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)
Zhou, Zhi; Liu, Xiaoxiao; Long, Brian; Peng, Hanchuan
2016-01-01
Efficient and accurate digital reconstruction of neurons from large-scale 3D microscopic images remains a challenge in neuroscience. We propose a new automatic 3D neuron reconstruction algorithm, TReMAP, which utilizes 3D Virtual Finger (a reverse-mapping technique) to detect 3D neuron structures based on tracing results on 2D projection planes. Our fully automatic tracing strategy achieves close performance with the state-of-the-art neuron tracing algorithms, with the crucial advantage of efficient computation (much less memory consumption and parallel computation) for large-scale images.
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.
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.
Mohri, Masakuni; Hashimoto, Naoki; Wada, Hiroshi
2016-03-01
By evolving bilaterally separated shell plates, bivalves acquired a unique body plan in which their soft tissues are completely protected by hard shell plates. In this unique body plan, mobility between the separated shell plates is provided by novel structures such as a ligament and adductor muscles. As a first step towards understanding how the bivalve body plan was established, we investigated the development of the separated shell plates and ligament. Over 100 years ago, it was hypothesized that the development of separated shell plates is tightly linked with the unique cell cleavage (division) pattern of bivalves during development, wherein each bilateral daughter cell of the 2d descendant 2d(1121) develops into one of the bilateral shell fields. In this study, we tested this hypothesis by tracing the cell lineages of the Japanese purple mussel Septifer virgatus. Although the shell fields were found to be exclusively derived from the bilateral descendant cells of 2d: 2d(11211) and 2d(11212), the descendants of these cells were not restricted to shell fields alone, nor were they confined to the left or right side of the shell field based on their lineage. Our study demonstrated that ligament cells are also derived from 2d(11211) and 2d(11212), indicating that the ligament cells emerged as a subpopulation of shell field cells. This also suggests that the establishment of the novel developmental system for the ligament cells was critical for the evolution of the unique body plan of bivalves.
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.
Tracing Rays In A Solar Power System
NASA Technical Reports Server (NTRS)
Jefferies, Kent; Gallo, Chris
1989-01-01
OFFSET is ray-tracing computer code for analysis of optics of solar collector. Code models distributions of solar flux within receiver cavity, produced by reflections from collector. Developed to model mathematically offset solar collector of solar dynamic electric power system being developed for Space Station Freedom. Used to develop revised collector-facet concept of four groups of toroidally contoured facets. Also used to develop methods for tailoring distribution of flux incident on receiver. Written in FORTRAN 77 (100 percent).
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.
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.
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
Tracing the cold regions of a dense core with para-H2D+ against a bright continuum source
NASA Astrophysics Data System (ADS)
Vastel, Charlotte
2015-10-01
Using Herschel/HIFI and IRAM-30m/Pdb observations, we detected a dense and cold core on the line of sight of a distant compact HII region (W51). While the fortuitous coincidence of the dense core along the line of sight with the continuum-bright W51e2 compact HII region has contributed to its non detection in the submillimeter continuum images, this same attribute makes it an appropriate source for absorption studies of star-forming gas. This core has been traced with deuterated species for the first time in absorption in the case of DCO+. We now propose to trace this core with the para-H2D+ ground-state transition, since H2D+ is a reliable tracer of the cold and dense phase of star-forming regions. For example, both species will be used to constrain the H2 fraction in its para form and consequently the age of the core. The source proposed here is unique because of its distance and its chance coincidence to lie against a bright continuum source. A detection is crucial to constrain the nature of the clump, in a chemical point of view, at a galactocentric distance (~ 5 kpc) different than the usual clouds (such as Orion and Taurus) that have been observed so far for detection of tracers of star-formation activity with H2D+.
The Polaris-M ray tracing program
NASA Astrophysics Data System (ADS)
Chipman, Russell A.; Lam, Wai Sze T.
2015-09-01
An optical design program, Polaris-M, developed at the University of Arizona incorporates many advanced polarization analysis features. At the core of the program is a three-dimensional polarization ray tracing structure used to characterize polarization effects occurring at interfaces and upon propagation through isotropic and anisotropic materials. Reflection and refraction at uniaxial, biaxial, and optically active interfaces are handled rigorously, as well as anisotropic grating structures. By analyzing multiple polarized wavefront components individually, one can study the complicated effects of multiple anisotropic optical elements at the image. Wavefronts can be expanded into polarization aberration terms. Polarized diffraction image formation and polarization dependent optical transfer functions are included.
Ray tracing analysis of inclined illumination techniques.
Sinkó, József; Szabó, Gábor; Erdélyi, Miklós
2014-08-11
The reduction of out of focus signal is a general task in fluorescence microscopy and is especially important in the recently developed super-resolution techniques because of the degradation of the final image. Several illumination methods have been developed to provide decreased out of focus signal level relative to the common epifluorescent illumination. In this paper we examine the highly inclined and the total internal reflection illumination techniques using the ray tracing method. Two merit functions were introduced for the quantitative description of the excitation of the selected region. We studied the feasibility of illumination methods, and the required corrections arising from the imperfections of the optical elements.
NASA Astrophysics Data System (ADS)
Clausing, Eric; Vielhauer, Claus
2015-03-01
Locksmith forensics is an important and very challenging part of classic crime scene forensics. In prior work, we propose a partial transfer to the digital domain, to effectively support forensic experts and present approaches for a full process chain consisting of five steps: Trace positioning, 2D/3D acquisition with a confocal 3D laser scanning microscope, detection by segmentation, trace type determination, and determination of the opening method. In particular the step of trace segmentation on high-resolution 3D surfaces thereby turned out to be the part most difficult to implement. The reason for that is the highly structured and complex surfaces to be analyzed. These surfaces are cluttered with a high number of toolmarks, which overlap and distort each other. In Clausing et al., we present an improved approach for a reliable segmentation of relevant trace regions but without the possibility of separating single traces out of segmented trace regions. However, in our past research, especially features based on shape and dimension turned out to be highly relevant for a fully automated analysis and interpretation. In this paper, we consequently propose an approach for this separation. To achieve this goal, we use our segmentation approach and expand it with a combination of the watershed algorithm with a graph-based analysis. Found sub-regions are compared based on their surface character and are connected or divided depending on their similarity. We evaluate our approach with a test set of about 1,300 single traces on the exemplary locking cylinder component 'key pin' and thereby are able of showing the high suitability of our approach.
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.
Ray tracing studies of Jupiter's magnetosphere
NASA Technical Reports Server (NTRS)
Six, N. F.
1982-01-01
Raypaths for decametric wavelength radiation in Jupiter's magnetosphere were calculated. The model-dependent raypaths with the Voyager observations were compared. Characteristics of the source regions and the influence of propagation effects were deduced. A three dimensional ray tracing program was employed to calculate the raypaths. Families of rays were launched at particular angles with respect to the magnetic field lines to generate conical sheets of radiation for various frequencies and various source locations. As the planet's magnetic field rotates, these warped sheets of radiation sweep past the observer, producing signatures in frequency versus time plots. These signatures match some of those found in the Voyager data. The greatest propagation effects occur in and around the source regions in the Io auroral oval.
2D profile of poloidal magnetic field diagnosed by a laser-driven ion-beam trace probe (LITP)
NASA Astrophysics Data System (ADS)
Yang, Xiaoyi; Xiao, Chijie; Chen, Yihang; Xu, Tianchao; Lin, Chen; Wang, Long; Xu, Min; Yu, Yi
2016-11-01
Based on large energy spread of laser-driven ion beam (LIB), a new method, the Laser-driven Ion-beam Trace Probe (LITP), was suggested recently to diagnose the poloidal magnetic field (Bp) and radial electric field (Er) in toroidal devices. Based on another property of LIB, a wide angular distribution, here we suggested that LITP could be extended to get 2D Bp profile or 1D profile of both poloidal and radial magnetic fields at the same time. In this paper, we show the basic principle, some preliminary simulation results, and experimental preparation to test the basic principle of LITP.
2D electron temperature diagnostic using soft x-ray imaging technique
Nishimura, K. Sanpei, A. Tanaka, H.; Ishii, G.; Kodera, R.; Ueba, R.; Himura, H.; Masamune, S.; Ohdachi, S.; Mizuguchi, N.
2014-03-15
We have developed a two-dimensional (2D) electron temperature (T{sub e}) diagnostic system for thermal structure studies in a low-aspect-ratio reversed field pinch (RFP). The system consists of a soft x-ray (SXR) camera with two pin holes for two-kinds of absorber foils, combined with a high-speed camera. Two SXR images with almost the same viewing area are formed through different absorber foils on a single micro-channel plate (MCP). A 2D T{sub e} image can then be obtained by calculating the intensity ratio for each element of the images. We have succeeded in distinguishing T{sub e} image in quasi-single helicity (QSH) from that in multi-helicity (MH) RFP states, where the former is characterized by concentrated magnetic fluctuation spectrum and the latter, by broad spectrum of edge magnetic fluctuations.
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.
2D X-ray scanner and its uses in laboratory reservoir characterization measurements
Maloney, D.; Doggett, K.
1997-08-01
X-ray techniques are used in petroleum laboratories for a variety of reservoir characterization measurements. This paper describes the configuration of a 2D X-ray scanner and many of the ways in which it simplifies and improves accuracy`s of laboratory measurements. Linear X-ray scanners are most often used to provide descriptions of fluid saturations within core plugs during flow tests. We configured our linear scanner for both horizontal and vertical movement. Samples can be scanned horizontally, vertically, or according to horizontal and vertical grids. X-ray measurements are fast, allowing measurements of two- and three-phase fluid saturations during both steady- and unsteady-state flow processes. Rock samples can be scanned while they are subjected to stress, pore pressure, and temperature conditions simulating those of a petroleum reservoir. Many types of measurements are possible by selecting appropriate X-ray power settings, dopes, filters, and collimator configurations. The scanner has been used for a variety of applications besides fluid saturation measurements. It is useful for measuring porosity distributions in rocks, concentrations of X-ray dopes within flow streams during tracer tests, gap widths in fracture flow cells, fluid interface levels in PVT cells and fluid separators, and other features and phenomena.
Ray tracing program with options for diffraction gratings
NASA Technical Reports Server (NTRS)
Howell, B. J.
1971-01-01
Diffraction theory, developed in vectorial form and coded into ray tracing routines, permits tracing rays of any wavelength through surfaces that are plane, spherical, conical, or aspheric polynomial. Ruled diffraction gratings may run in either X-direction or Y-direction, where Z is optical axis.
Using differential ray tracing in stray light analysis
NASA Astrophysics Data System (ADS)
Rock, David F.
2012-10-01
This paper describes differential ray tracing and shows how it can be used to great advantage in stray light analysis. Tracing a differential ray from a source to a target yields a set of derivatives that contain a complete first-order description of a ray bundle surrounding the ray being traced. These derivatives provide the information needed for aiming rays and transforming a sample area on a target surface into a solid angle seen by the source. By using targeted differential rays, we eliminate the need for defining importance curves for generating scattered rays. Convergence is accelerated, and the resulting irradiance distributions end up smoother than what one usually obtains with the traditional Monte Carlo approach. This paper also shows how the derivatives from a single ray can be used to define and propagate Gaussian beams without the need for secondary rays.
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
Quantizing calcification in the lumbar aorta on 2-D lateral x-ray images
NASA Astrophysics Data System (ADS)
Conrad-Hansen, Lars A.; Lauze, Francois; Tanko, Laszlo B.; Nielsen, Mads
2005-04-01
In this paper we seek to improve upon the standard method of assessing the degree of calcification in the lumbar aorta, which is commonly used on lateral 2-D x-rays. The necessity for improvement arises from the fact that the existing method can not measure subtle progressions in the plaque development; neither is it possible to express the density of individual plaques. Both of these qualities would be desireable to assess, since they are the key for making progression studies as well as for testing the effect of drugs in longitudinal studies. Our approach is based on inpainting, a technique used in image restoration as well as postprocessing of film. In this study we discuss the potential implications of total variation inpainting for characterizing aortic calcification.
Characterization of a 2D soft x-ray tomography camera with discrimination in energy bands
Romano, A.; Pacella, D.; Gabellieri, L.; Tilia, B.; Piergotti, V.; Mazon, D.; Malard, P.
2010-10-15
A gas detector with a 2D pixel readout is proposed for a future soft x-ray (SXR) tomography with discrimination in energy bands separately per pixel. The detector has three gas electron multiplier foils for the electron amplification and it offers the advantage, compared with the single stage, to be less sensitive to neutrons and gammas. The energy resolution and the detection efficiency of the detector have been accurately studied in the laboratory with continuous SXR spectra produced by an electronic tube and line emissions produced by fluorescence (K, Fe, and Mo) in the range of 3-17 keV. The front-end electronics, working in photon counting mode with a selectable threshold for pulse discrimination, is optimized for high rates. The distribution of the pulse amplitude has been indirectly derived by means of scans of the threshold. Scans in detector gain have also been performed to assess the capability of selecting different energy ranges.
Geometry-invariant GRIN lens: finite ray tracing.
Bahrami, Mehdi; Goncharov, Alexander V
2014-11-17
The refractive index distribution of the geometry-invariant gradient refractive index lens (GIGL) model is derived as a function of Cartesian coordinates. The adjustable external geometry of the GIGL model aims to mimic the shape of the human and animal crystalline lens. The refractive index distribution is based on an adjustable power-law profile, which provides additional flexibility of the model. An analytical method for layer-by-layer finite ray tracing through the GIGL model is developed and used to calculate aberrations of the GIGL model. The result of the finite ray tracing aberrations of the GIGL model are compared to those obtained with paraxial ray tracing. The derived analytical expression for the refractive index distribution can be employed in the reconstruction processes of the eye using the conventional ray tracing methods. The layer-by-layer finite ray tracing approach would be an asset in ray tracing through a modified GIGL model, where the refractive index distribution cannot be described analytically. Using the layer-by-layer finite ray-tracing method, the potential of the GIGL model in representing continuous as well as shell-like layered structures is illustrated and the results for both cases are presented and analysed.
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.
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.
Fast 2-D soft X-ray imaging device based on micro pattern gas detector
NASA Astrophysics Data System (ADS)
Pacella, D.; Bellazzini, R.; Brez, A.; Pizzicaroli, G.
2003-09-01
An innovative fast system for X-ray imaging has been developed at ENEA Frascati (Italy) to be used as diagnostic of magnetic plasmas for thermonuclear fusion. It is based on a pinhole camera coupled to a Micro Pattern Gas Detector (MPGD) having a Gas Electron Multiplier (GEM) as amplifying stage. This detector (2.5 cm × 2.5 cm active area) is equipped with a 2-D read-out printed circuit board with 144 pixels (12 × 12), with an electronic channel for each pixel (charge conversion, shaping, discrimination and counting). Working in photon counting mode, in proportional regime, it is able to get X-ray images of the plasma in a selectable X-ray energy range, at very high photon fluxes (106 ph s-̊1mm-2 all over the detector) and high framing rate (up to 100 kHz). It has very high dynamic range, high signal to noise ratio (statistical) and large flexibility in the optical configurations (magnification and views on the plasma). The system has been tested successfully on the Frascati Tokamak Upgrade (FTU), having central electron temperature of a few keV and density of 1020 m-3, during the summer 2001, with a one-dimensional perpendicular view of the plasma. In collaboration with ENEA, the Johns Hopkins University (JHU) and Princeton Plasma Physics (PPPL), this system has been set up and calibrated in the X-ray energy range 2-8 keV and it has been installed, with a two-dimensional tangential view, on the spherical tokamak NSTX at Princeton. Time resolved X-ray images of the NSTX plasma core have been obtained. Fast acquisitions, performed up to 50 kHz of framing rate, allow the study of the plasma evolution and its magneto-hydrodynamic instabilities, while with a slower sampling (a few kHz) the curvature of the magnetic surfaces can be measured. All these results reveal the good imaging properties of this device at high time resolution, despite of the low number of pixels, and the effectiveness of the fine controlled energy discrimination.
Fracture network evaluation program (FraNEP): A software for analyzing 2D fracture trace-line maps
NASA Astrophysics Data System (ADS)
Zeeb, Conny; Gomez-Rivas, Enrique; Bons, Paul D.; Virgo, Simon; Blum, Philipp
2013-10-01
Fractures, such as joints, faults and veins, strongly influence the transport of fluids through rocks by either enhancing or inhibiting flow. Techniques used for the automatic detection of lineaments from satellite images and aerial photographs, LIDAR technologies and borehole televiewers significantly enhanced data acquisition. The analysis of such data is often performed manually or with different analysis software. Here we present a novel program for the analysis of 2D fracture networks called FraNEP (Fracture Network Evaluation Program). The program was developed using Visual Basic for Applications in Microsoft Excel™ and combines features from different existing software and characterization techniques. The main novelty of FraNEP is the possibility to analyse trace-line maps of fracture networks applying the (1) scanline sampling, (2) window sampling or (3) circular scanline and window method, without the need of switching programs. Additionally, binning problems are avoided by using cumulative distributions, rather than probability density functions. FraNEP is a time-efficient tool for the characterisation of fracture network parameters, such as density, intensity and mean length. Furthermore, fracture strikes can be visualized using rose diagrams and a fitting routine evaluates the distribution of fracture lengths. As an example of its application, we use FraNEP to analyse a case study of lineament data from a satellite image of the Oman Mountains.
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.
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.
Ray tracing method for doubly curved reflector surfaces
NASA Astrophysics Data System (ADS)
Sletten, C. J.
1981-06-01
A regular grid of discrete points is often used to define shaped reflector surfaces for microwave antennas. In the present paper, a ray tracing procedure useful for computing aperture and power distributions produced by an arbitrarily shaped reflector surface is described. It is found that this formulation provides an accurate ray tracing tool for shaped surfaces approximating conic sections and with d values small enough for templates used for precise construction of these surfaces.
Registration of 2D x-ray images to 3D MRI by generating pseudo-CT data
NASA Astrophysics Data System (ADS)
van der Bom, M. J.; Pluim, J. P. W.; Gounis, M. J.; van de Kraats, E. B.; Sprinkhuizen, S. M.; Timmer, J.; Homan, R.; Bartels, L. W.
2011-02-01
Spatial and soft tissue information provided by magnetic resonance imaging can be very valuable during image-guided procedures, where usually only real-time two-dimensional (2D) x-ray images are available. Registration of 2D x-ray images to three-dimensional (3D) magnetic resonance imaging (MRI) data, acquired prior to the procedure, can provide optimal information to guide the procedure. However, registering x-ray images to MRI data is not a trivial task because of their fundamental difference in tissue contrast. This paper presents a technique that generates pseudo-computed tomography (CT) data from multi-spectral MRI acquisitions which is sufficiently similar to real CT data to enable registration of x-ray to MRI with comparable accuracy as registration of x-ray to CT. The method is based on a k-nearest-neighbors (kNN)-regression strategy which labels voxels of MRI data with CT Hounsfield Units. The regression method uses multi-spectral MRI intensities and intensity gradients as features to discriminate between various tissue types. The efficacy of using pseudo-CT data for registration of x-ray to MRI was tested on ex vivo animal data. 2D-3D registration experiments using CT and pseudo-CT data of multiple subjects were performed with a commonly used 2D-3D registration algorithm. On average, the median target registration error for registration of two x-ray images to MRI data was approximately 1 mm larger than for x-ray to CT registration. The authors have shown that pseudo-CT data generated from multi-spectral MRI facilitate registration of MRI to x-ray images. From the experiments it could be concluded that the accuracy achieved was comparable to that of registering x-ray images to CT data.
A generic x-ray tracing toolbox in Geant4
NASA Astrophysics Data System (ADS)
Vacanti, Giuseppe; Buis, Ernst-Jan; Collon, Maximilien; Beijersbergen, Marco; Kelly, Chris
2009-05-01
We have developed a generic X-ray tracing toolbox based on Geant4, a generic simulation toolkit. By leveraging the facilities available on Geant4, we are able to design and analyze complex X-ray optical systems. In this article we describe our toolbox, and describe how it is being applied to support the development of silicon pore optics for IXO.
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.
Interactive isosurface ray tracing of time-varying tetrahedral volumes.
Wald, Ingo; Friedrich, Heiko; Knoll, Aaron; Hansen, Charles D
2007-01-01
We describe a system for interactively rendering isosurfaces of tetrahedral finite-element scalar fields using coherent ray tracing techniques on the CPU. By employing state-of-the art methods in polygonal ray tracing, namely aggressive packet/frustum traversal of a bounding volume hierarchy, we can accomodate large and time-varying unstructured data. In conjunction with this efficiency structure, we introduce a novel technique for intersecting ray packets with tetrahedral primitives. Ray tracing is flexible, allowing for dynamic changes in isovalue and time step, visualization of multiple isosurfaces, shadows, and depth-peeling transparency effects. The resulting system offers the intuitive simplicity of isosurfacing, guaranteed-correct visual results, and ultimately a scalable, dynamic and consistently interactive solution for visualizing unstructured volumes.
Microcellular propagation prediction model based on an improved ray tracing algorithm.
Liu, Z-Y; Guo, L-X; Fan, T-Q
2013-11-01
Two-dimensional (2D)/two-and-one-half-dimensional ray tracing (RT) algorithms for the use of the uniform theory of diffraction and geometrical optics are widely used for channel prediction in urban microcellular environments because of their high efficiency and reliable prediction accuracy. In this study, an improved RT algorithm based on the "orientation face set" concept and on the improved 2D polar sweep algorithm is proposed. The goal is to accelerate point-to-point prediction, thereby making RT prediction attractive and convenient. In addition, the use of threshold control of each ray path and the handling of visible grid points for reflection and diffraction sources are adopted, resulting in an improved efficiency of coverage prediction over large areas. Measured results and computed predictions are also compared for urban scenarios. The results indicate that the proposed prediction model works well and is a useful tool for microcellular communication applications.
Ray tracing of lower hybrid and ion cyclotron waves
NASA Astrophysics Data System (ADS)
Brambilla, Marco
1986-08-01
We review the use of ray tracing codes for the investigation of wave propagation and plasma heating in toroidal axisymmetric geometry, with particular emphasis to the lower hybrid and ion cyclotron frequency ranges. After a summary of the approximations involved, we point out that, at these low frequencies, a full-wave treatment of the launching structure on the one hand, and of singular layers (wave and particle resonances) on the other hand, are an essential part of any ray tracing code. The spectral approach to ray tracing, which makes explicit use of the decomposition of the hf fields in toroidal modes allowed by axisymmetry, is instrumental to cope with electrically short antennas whose radiation pattern is dominated by diffraction, and to allow a plausible evaluation of Landau and cyclotron damping, and of wave behaviour near conversion layers. Numerical methods and structure of ray tracing briefly discussed, and a few examples are presented, obtained with the RAYLH and RAYIC codes developed by the author. The rapidly growing number of applications of ray tracing in the literature is also briefly summarised; it is the best proof that this approximate method, if its possibilities and limits are properly understood, can give precious insight into the physics of hf heating of tokamak plasmas.
Jesus, Danilo A; Iskander, D Robert
2015-12-01
Ray tracing is a powerful technique to understand the light behavior through an intricate optical system such as that of a human eye. The prediction of visual acuity can be achieved through characteristics of an optical system such as the geometrical point spread function. In general, its precision depends on the number of discrete rays and the accurate surface representation of each eye's components. Recently, a method that simplifies calculation of the geometrical point spread function has been proposed for circularly symmetric systems [Appl. Opt.53, 4784 (2014)]. An extension of this method to 2D noncircularly symmetric systems is proposed. In this method, a two-dimensional ray tracing procedure for an arbitrary number of surfaces and arbitrary surface shapes has been developed where surfaces, rays, and refractive indices are all represented in functional forms being approximated by Chebyshev polynomials. The Liou and Brennan anatomically accurate eye model has been adapted and used for evaluating the method. Further, real measurements of the anterior corneal surface of normal, astigmatic, and keratoconic eyes were substituted for the first surface in the model. The results have shown that performing ray tracing, utilizing the two-dimensional Chebyshev function approximation, is possible for noncircularly symmetric models, and that such calculation can be performed with a newly created Chebfun toolbox.
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.
Benthin, Carsten; Wald, Ingo; Woop, Sven; Ernst, Manfred; Mark, William R
2012-09-01
Wide-SIMD hardware is power and area efficient, but it is challenging to efficiently map ray tracing algorithms to such hardware especially when the rays are incoherent. The two most commonly used schemes are either packet tracing, or relying on a separate traversal stack for each SIMD lane. Both work great for coherent rays, but suffer when rays are incoherent: The former experiences a dramatic loss of SIMD utilization once rays diverge; the latter requires a large local storage, and generates multiple incoherent streams of memory accesses that present challenges for the memory system. In this paper, we introduce a single-ray tracing scheme for incoherent rays that uses just one traversal stack on 16-wide SIMD hardware. It uses a bounding-volume hierarchy with a branching factor of four as the acceleration structure, exploits four-wide SIMD in each box and primitive intersection test, and uses 16-wide SIMD by always performing four such node or primitive tests in parallel. We then extend this scheme to a hybrid tracing scheme that automatically adapts to varying ray coherence by starting out with a 16-wide packet scheme and switching to the new single-ray scheme as soon as rays diverge. We show that on the Intel Many Integrated Core architecture this hybrid scheme consistently, and over a wide range of scenes and ray distributions, outperforms both packet and single-ray tracing.
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.
On ray-tracing via caustic geometry
NASA Astrophysics Data System (ADS)
Chillingworth, David R. J.; Danesh-Narouie, G. R.; Westcott, Bryan S.
1990-05-01
It is shown that results from the mathematical theory of singularities of differentiable mappings make it possible to understand the local structure of typical caustics in fields of two and three dimensions, and that this local information can be pieced together to give an effective visualization of the overall ray configuration. For simplicity, the work is done in the context of geometrical optics only, assuming the region of space under consideration to be homogeneous, so that ray paths are straight lines. No account is taken of edge diffraction, although the methods can be extended to incorporate such effects using the geometric theory of diffraction. Quantitative results concerning numbers and configurations of specular points are obtained for source and field points, the positions of which are allowed to vary.
Ray tracing a three dimensional scene using a grid
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.
Fast GPU-based ray tracing in radial GRIN lenses.
Horiuchi, Shuma; Yoshida, Shuhei; Yamamoto, Manabu
2014-07-01
This paper describes that in ray tracing of a radial gradient-index (GRIN) lens, analysis with a graphics processing unit (GPU) can complete faster than analysis with a central processing unit (CPU). The refractive index of the radial GRIN lens varies in the direction perpendicular to the optical axis. We prepare two types of the refractive index distribution for the radial GRIN lens. One type of distribution is represented by the power series expansion equation and the other is an arbitrary distribution type represented by a cubic spline interpolation curve. Although the performance of ray tracing with these distribution representations varies between representations, in both representations, the analysis with a GPU is about 19 times (on average) faster than that with a CPU. The average GPU effective performance is 90% and 40% when the refractive index distribution is given by the power series expansion equation and spline interpolation curve, respectively. These increased performances indicate that ray tracing with these distributions is very effective for the GRIN lens illumination and rendering analyses, which have to trace a significant number of rays.
Tscherning ellipses and ray tracing in aspheric ophthalmic lenses.
Malacara, D; Malacara, Z
1985-07-01
The effect of conicoid asphericity in one of the surfaces of an ophthalmic lens is examined by means of exact ray tracing. Graphical solutions resembling the Tscherning ellipses are obtained for lenses free of oblique astigmatism as well as for lenses free of peripheral power error or curvature of field.
Electromagnetic scattering from an inhomogeneous object by ray tracing
NASA Technical Reports Server (NTRS)
Kim, Hyeongdong; Ling, Hao
1992-01-01
A 'shooting and bouncing ray' (SBR) formulation is presented for treating the electromagnetic scattering from electrically large, inhomogeneous objects. A dense grid of rays representing the incident plane wave is shot toward the inhomogeneous object. At the scatterer boundary, reflected rays and refracted rays are generated due to discontinuity of the medium parameters. The trajectory, amplitude, phase and polarization of the rays inside the inhomogeneous object are traced based on geometrical optics. Whenever the rays cross the scatterer surface, additional reflected/refracted rays are generated and are tracked. This process is repeated until the intensities of the refracted/reflected rays become negligible. The contributions of the exiting rays to the total scattered field are calculated by using the equivalence principle in conjunction with a ray-tube integration scheme. The ray formulation is applied to calculate the backscattering from cylinders and spheres and good agreement with the exact series solutions is observed in the high frequency range. In addition, the backscattering mechanisms in penetrable objects are interpreted in terms of simple ray pictures.
Simplifying numerical ray tracing for characterization of optical systems.
Gagnon, Yakir Luc; Speiser, Daniel I; Johnsen, Sönke
2014-07-20
Ray tracing, a computational method for tracing the trajectories of rays of light through matter, is often used to characterize mechanical or biological visual systems with aberrations that are larger than the effect of diffraction inherent in the system. For example, ray tracing may be used to calculate geometric point spread functions (PSFs), which describe the image of a point source after it passes through an optical system. Calculating a geometric PSF is useful because it gives an estimate of the detail and quality of the image formed by a given optical system. However, when using ray tracing to calculate a PSF, the accuracy of the estimated PSF directly depends on the number of discrete rays used in the calculation; higher accuracies may require more computational power. Furthermore, adding optical components to a modeled system will increase its complexity and require critical modifications so that the model will describe the system correctly, sometimes necessitating a completely new model. Here, we address these challenges by developing a method that represents rays of light as a continuous function that depends on the light's initial direction. By utilizing Chebyshev approximations (via the chebfun toolbox in MATLAB) for the implementation of this method, we greatly simplified the calculations for the location and direction of the rays. This method provides high precision and fast calculation speeds that allow the characterization of any symmetrical optical system (with a centered point source) in an analytical-like manner. Next, we demonstrate our methods by showing how they can easily calculate PSFs for complicated optical systems that contain multiple refractive and/or reflective interfaces.
HART: A Hybrid Architecture for Ray Tracing Animated Scenes.
Nah, Jae-Ho; Kim, Jin-Woo; Park, Junho; Lee, Won-Jong; Park, Jeong-Soo; Jung, Seok-Yoon; Park, Woo-Chan; Manocha, Dinesh; Han, Tack-Don
2015-03-01
We present a hybrid architecture, inspired by asynchronous BVH construction [1], for ray tracing animated scenes. Our hybrid architecture utilizes heterogeneous hardware resources: dedicated ray-tracing hardware for BVH updates and ray traversal and a CPU for BVH reconstruction. We also present a traversal scheme using a primitive's axis-aligned bounding box (PrimAABB). This scheme reduces ray-primitive intersection tests by reusing existing BVH traversal units and the primAABB data for tree updates; it enables the use of shallow trees to reduce tree build times, tree sizes, and bus bandwidth requirements. Furthermore, we present a cache scheme that exploits consecutive memory access by reusing data in an L1 cache block. We perform cycle-accurate simulations to verify our architecture, and the simulation results indicate that the proposed architecture can achieve real-time Whitted ray tracing animated scenes at 1,920 × 1,200 resolution. This result comes from our high-performance hardware architecture and minimized resource requirements for tree updates.
HART: A Hybrid Architecture for Ray Tracing Animated Scenes.
Nah, Jae-Ho; Kim, Jin-Woo; Park, Junho; Lee, Won-Jong; Park, Jeong-Soo; Jung, Seok-Yoon; Park, Woo-Chan; Manocha, Dinesh; Han, Tack-Don
2015-03-01
We present a hybrid architecture, inspired by asynchronous BVH construction [1], for ray tracing animated scenes. Our hybrid architecture utilizes heterogeneous hardware resources: dedicated ray-tracing hardware for BVH updates and ray traversal and a CPU for BVH reconstruction. We also present a traversal scheme using a primitive's axis-aligned bounding box (PrimAABB). This scheme reduces ray-primitive intersection tests by reusing existing BVH traversal units and the primAABB data for tree updates; it enables the use of shallow trees to reduce tree build times, tree sizes, and bus bandwidth requirements. Furthermore, we present a cache scheme that exploits consecutive memory access by reusing data in an L1 cache block. We perform cycle-accurate simulations to verify our architecture, and the simulation results indicate that the proposed architecture can achieve real-time Whitted ray tracing animated scenes at 1,920 × 1,200 resolution. This result comes from our high-performance hardware architecture and minimized resource requirements for tree updates. PMID:26357070
NASA Astrophysics Data System (ADS)
Merkel, Ronny; Gruhn, Stefan; Dittmann, Jana; Vielhauer, Claus; Bräutigam, Anja
2012-03-01
Determining the age of latent fingerprint traces found at crime scenes is an unresolved research issue since decades. Solving this issue could provide criminal investigators with the specific time a fingerprint trace was left on a surface, and therefore would enable them to link potential suspects to the time a crime took place as well as to reconstruct the sequence of events or eliminate irrelevant fingerprints to ensure privacy constraints. Transferring imaging techniques from different application areas, such as 3D image acquisition, surface measurement and chemical analysis to the domain of lifting latent biometric fingerprint traces is an upcoming trend in forensics. Such non-destructive sensor devices might help to solve the challenge of determining the age of a latent fingerprint trace, since it provides the opportunity to create time series and process them using pattern recognition techniques and statistical methods on digitized 2D, 3D and chemical data, rather than classical, contact-based capturing techniques, which alter the fingerprint trace and therefore make continuous scans impossible. In prior work, we have suggested to use a feature called binary pixel, which is a novel approach in the working field of fingerprint age determination. The feature uses a Chromatic White Light (CWL) image sensor to continuously scan a fingerprint trace over time and retrieves a characteristic logarithmic aging tendency for 2D-intensity as well as 3D-topographic images from the sensor. In this paper, we propose to combine such two characteristic aging features with other 2D and 3D features from the domains of surface measurement, microscopy, photography and spectroscopy, to achieve an increase in accuracy and reliability of a potential future age determination scheme. Discussing the feasibility of such variety of sensor devices and possible aging features, we propose a general fusion approach, which might combine promising features to a joint age determination scheme
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.
NASA Astrophysics Data System (ADS)
Zagorchev, Lyubomir; Manzke, Robert; Cury, Ricardo; Reddy, Vivek Y.; Chan, Raymond C.
2007-03-01
Interventional cardiac electrophysiology (EP) procedures are typically performed under X-ray fluoroscopy for visualizing catheters and EP devices relative to other highly-attenuating structures such as the thoracic spine and ribs. These projections do not however contain information about soft-tissue anatomy and there is a recognized need for fusion of conventional fluoroscopy with pre-operatively acquired cardiac multislice computed tomography (MSCT) volumes. Rapid 2D-3D integration in this application would allow for real-time visualization of all catheters present within the thorax in relation to the cardiovascular anatomy visible in MSCT. We present a method for rapid fusion of 2D X-ray fluoroscopy with 3DMSCT that can facilitate EP mapping and interventional procedures by reducing the need for intra-operative contrast injections to visualize heart chambers and specialized systems to track catheters within the cardiovascular anatomy. We use hardware-accelerated ray-casting to compute digitally reconstructed radiographs (DRRs) from the MSCT volume and iteratively optimize the rigid-body pose of the volumetric data to maximize the similarity between the MSCT-derived DRR and the intra-operative X-ray projection data.
New challenges in ray tracing simulations of X-ray optics
NASA Astrophysics Data System (ADS)
Sánchez del Río, M.
2013-03-01
The construction of new synchrotron sources and the refurbishment and upgrade of existing ones has boosted in the last years the interest in X-ray optics simulations for beamline design and optimization. In the last years we conducted a full renewal of the well established SHADOW ray tracing code, ending with a modular version SHADOW3 interfaced to multiple programming languages (C, C++, IDL, Python). Some of the new features of SHADOW3 are presented. From the physics point of view, SHADOW3 has been upgraded for dealing with lens systems. X-ray partial coherence applications demand an extension of traditional ray tracing methods into a hybrid ray-tracing wave-optics approach. The software development is essential for fulfilling the requests of the ESRF Upgrade Programme, and some examples of calculations are also presented.
2D and 3D Refraction Based X-ray Imaging Suitable for Clinical and Pathological Diagnosis
Ando, Masami; Bando, Hiroko; Ueno, Ei
2007-01-19
The first observation of micro papillary (MP) breast cancer by x-ray dark-field imaging (XDFI) and the first observation of the 3D x-ray internal structure of another breast cancer, ductal carcinoma in-situ (DCIS), are reported. The specimen size for the sheet-shaped MP was 26 mm x 22 mm x 2.8 mm, and that for the rod-shaped DCIS was 3.6 mm in diameter and 4.7 mm in height. The experiment was performed at the Photon Factory, KEK: High Energy Accelerator Research Organization. We achieved a high-contrast x-ray image by adopting a thickness-controlled transmission-type angular analyzer that allows only refraction components from the object for 2D imaging. This provides a high-contrast image of cancer-cell nests, cancer cells and stroma. For x-ray 3D imaging, a new algorithm due to the refraction for x-ray CT was created. The angular information was acquired by x-ray optics diffraction-enhanced imaging (DEI). The number of data was 900 for each reconstruction. A reconstructed CT image may include ductus lactiferi, micro calcification and the breast gland. This modality has the possibility to open up a new clinical and pathological diagnosis using x-ray, offering more precise inspection and detection of early signs of breast cancer.
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.
Two-dimensional ray-tracing model for light trapping in microgroove silicon solar cells
NASA Astrophysics Data System (ADS)
Sobhan, M. A.
1992-11-01
A 2-D ray tracing model incorporating light trapping effect to compute the optical generation rate (OGR) for light generated minority carriers in high efficiency micro-groove ((mu) G) silicon solar cells is presented. Based on the principles of geometrical optics, six major types of rays are identified which mainly contribute to light trapping in the (mu) G structure. Assuming .1 and 1.0 reflectances, respectively, on the front and back surfaces, our model computes light generated current density JL to be 53.79 mA/cm2 at AMO for a 100 micrometers thick cell. This value exhibits better agreement with ideal values as compared to those of other 1-D models existing in the literature. On the basis of OGR data from the model, a closed form 2-D OGR formula is developed using fast Fourier transform (FFT) technique. This formula facilitates the apply method of separation of variables to obtain closed form solutions of the 2-D minority carrier transport equations and satisfies the requirements for the boundary conditions therein for device modeling and analysis of (mu) G cells. Performance parameters of (mu) G cells predicted by our computer simulation agree fairly well with recent experimental results.
McXtrace: a modern ray-tracing package for x-ray instrumentation
NASA Astrophysics Data System (ADS)
Knudsen, Erik B.; Prodi, Andrea; Willendrup, Peter; Lefmann, Kim; Baltser, Jana; Gundlach, Carsten; Sanchez del Rio, Manuel; Ferrero, Claudio; Feidenhans'l, Robert
2011-09-01
we present the developments of the McXtrace project, a free, open source software package based on Monte Carlo ray tracing for simulations and optimisation of complete X-ray instruments. The methodology of building a simulation is presented through an example beamline, namely Beamline 811 at MAX-lab, Lund, Sweden - a beamline dedicated to materials science.
An improved MIMO-SAR simulator strategy with ray tracing
NASA Astrophysics Data System (ADS)
Xiang, Xingyu; Mo, Zijian; Wang, Zhonghai; Chen, Genshe; Pham, Khanh; Blasch, Erik
2016-05-01
High resolution and wide-swath imaging can be obtained by Multiple-Input Multiple-Output (MIMO) synthetic aperture radar (SAR) with the state of the art technologies. The time division multiple access (TDMA) MIMO SAR mimics the motion of the antenna of SAR systems by switching the array channels to transmit the radar signals at different time slots. In this paper, we develop a simulation tool with ray tracing techniques to retrieve high resolution and accurate SAR images for development of MIMO SAR imaging methods. Without loss of generality, in the proposed simulator, we apply a TDMA MIMO SAR system with 13 transmitting antennas and 8 receiving antennas, where all transmitting antennas share a single transmitter and the receiving antennas share a single receiver. By comparing with the normal simulation MIMO SAR strategies, the simulation image using ray tracing results validate that the proposed method provides more accurate and higher resolution SAR images.
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.
Twin robotic x-ray system for 2D radiographic and 3D cone-beam CT imaging
NASA Astrophysics Data System (ADS)
Fieselmann, Andreas; Steinbrener, Jan; Jerebko, Anna K.; Voigt, Johannes M.; Scholz, Rosemarie; Ritschl, Ludwig; Mertelmeier, Thomas
2016-03-01
In this work, we provide an initial characterization of a novel twin robotic X-ray system. This system is equipped with two motor-driven telescopic arms carrying X-ray tube and flat-panel detector, respectively. 2D radiographs and fluoroscopic image sequences can be obtained from different viewing angles. Projection data for 3D cone-beam CT reconstruction can be acquired during simultaneous movement of the arms along dedicated scanning trajectories. We provide an initial evaluation of the 3D image quality based on phantom scans and clinical images. Furthermore, initial evaluation of patient dose is conducted. The results show that the system delivers high image quality for a range of medical applications. In particular, high spatial resolution enables adequate visualization of bone structures. This system allows 3D X-ray scanning of patients in standing and weight-bearing position. It could enable new 2D/3D imaging workflows in musculoskeletal imaging and improve diagnosis of musculoskeletal disorders.
Reconstructing lower hybrid fields from ray tracing data
Richardson, A. S.; Bonoli, P.; Wright, J.
2009-11-26
Ray tracing methods are commonly used to estimate the propagation of RF fields in plasmas. By going to higher order in the approximations used to derive the ray equations, it is possible to also reconstruct an approximate field from a family of rays. However, this field reconstruction is often neglected, primarily because of the difficulty of automatically dealing with focusing and reflections (caustics) in computational algorithms. In this work, we have been examining the feasibility of using tools developed for semi-classical quantum approximations to do RF field reconstructions. Specifically, it is possible to obtain a set of ODE's which approximately describe the dynamics of a wave packet centered on a ray. From this information, an approximate field can be reconstructed. We here report preliminary results for the reconstruction of lower hybrid fields using this technique.
Ray tracing of broadband bursty radio emissions from Uranus
NASA Technical Reports Server (NTRS)
Curran, D. B.; Menietti, J. D.; Wong, H. K.
1990-01-01
To determine the source position of the broadband bursty emission, rays of X-mode emissin were traced from source positions along magnetic field lines with footprints that form a large grid centered approximately on the south magnetic pole of Uranus. For large wave normal angles, source regions different from those producing b-smooth emission were found. The emission observed prior to closest approach has a source along field lines that are distinct from those which generate emissions observed after closest approach.
Ray tracing for point distribution in unstructured grid generation
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.
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.
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).
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.
Coronary arteries motion modeling on 2D x-ray images
NASA Astrophysics Data System (ADS)
Gao, Yang; Sundar, Hari
2012-02-01
During interventional procedures, 3D imaging modalities like CT and MRI are not commonly used due to interference with the surgery and radiation exposure concerns. Therefore, real-time information is usually limited and building models of cardiac motion are difficult. In such case, vessel motion modeling based on 2-D angiography images become indispensable. Due to issues with existing vessel segmentation algorithms and the lack of contrast in occluded vessels, manual segmentation of certain branches is usually necessary. In addition, such occluded branches are the most important vessels during coronary interventions and obtaining motion models for these can greatly help in reducing the procedure time and radiation exposure. Segmenting different cardiac phases independently does not guarantee temporal consistency and is not efficient for occluded branches required manual segmentation. In this paper, we propose a coronary motion modeling system which extracts the coronary tree for every cardiac phase, maintaining the segmentation by tracking the coronary tree during the cardiac cycle. It is able to map every frame to the specific cardiac phase, thereby inferring the shape information of the coronary arteries using the model corresponding to its phase. Our experiments show that our motion modeling system can achieve promising results with real-time performance.
NASA Astrophysics Data System (ADS)
Besch, H. J.; Junk, M.; Meißner, W.; Sarvestani, A.; Stiehler, R.; Walenta, A. H.
1997-02-01
The high rates available now at synchrotron beam lines ask for detectors allowing online measurements with good spatial resolution and a precise intensity measurement. For this purpose gaseous detectors operating in the single photon counting mode are well suited. An interpolating 2D pixel readout structure will be presented. It has been tested as backplane of a MSGC or a CAT-detector (recently developed by the group of M. Lemonnier at LURE), and it operates on the principle of resistive charge partition, allowing asynchronous readout. A resolution of 200 μm is reached. Under similar conditions the energy resolution from the signals of the readout structure presented is nearly the same as that of standard readout. In combination with a CAT an energy resolution of 20% is reached. A prototype of 64 channels with a sensitive area of 14 mm × 14 mm was tested at the synchrotron at LURE (Orsay). Diffraction patterns from a collagenase protein crystal were measured and rocking curves were obtained with an angular resolution of 1.5 × 10 -5.
NASA Astrophysics Data System (ADS)
Hatt, Charles R.; Speidel, Michael A.; Raval, Amish N.
2014-03-01
We present a novel 2D/ 3D registration algorithm for fusion between transesophageal echocardiography (TEE) and X-ray fluoroscopy (XRF). The TEE probe is modeled as a subset of 3D gradient and intensity point features, which facilitates efficient 3D-to-2D perspective projection. A novel cost-function, based on a combination of intensity and edge features, evaluates the registration cost value without the need for time-consuming generation of digitally reconstructed radiographs (DRRs). Validation experiments were performed with simulations and phantom data. For simulations, in silica XRF images of a TEE probe were generated in a number of different pose configurations using a previously acquired CT image. Random misregistrations were applied and our method was used to recover the TEE probe pose and compare the result to the ground truth. Phantom experiments were performed by attaching fiducial markers externally to a TEE probe, imaging the probe with an interventional cardiac angiographic x-ray system, and comparing the pose estimated from the external markers to that estimated from the TEE probe using our algorithm. Simulations found a 3D target registration error of 1.08(1.92) mm for biplane (monoplane) geometries, while the phantom experiment found a 2D target registration error of 0.69mm. For phantom experiments, we demonstrated a monoplane tracking frame-rate of 1.38 fps. The proposed feature-based registration method is computationally efficient, resulting in near real-time, accurate image based registration between TEE and XRF.
Time Resolved 2D X-Ray Densitometry of a Ventilated Partial Cavity Closure
NASA Astrophysics Data System (ADS)
Makiharju, Simo; Ceccio, Steven
2011-11-01
A time resolved x-ray densitometry system was developed to measure the spatial distribution of void fraction for nominally two-dimensional flows. The system can image a region of (15 cm)2 at a frame rate of up to 4000 fps. The source was a rotating anode type normally used for cineradiography and angiography. Supplied by a 65 kW high frequency generator with a high speed starter, it could be operated at up to 433 mA at 150 kV. The imager subsystem comprised of a high speed camera coupled with a high resolution image intensifier. The range of measured void fraction can be changed to span a desired range yielding an uncertainty on the order of 1% of the measurement range. The system is used to examine the void fraction field in the closure region of a ventilated partial cavity behind a backward facing step. The cavity has Reynolds number of O(105) based on the cavity length, and a non-dimensional gas flux of Q* = 0.0048. The bubbly flow created in the cavity wake is examined using the x-ray densitometry system, duel fiber optical probes, and high speed cinematography. The local void fraction and bubble size distributions in the cavity wake are determined, and the measurements methods are compared. The research was sponsored by ONR under grant N00014-08-1-0215, program manager Dr. L. Patrick Purtell.
2D-Omnidirectional Hard-X-Ray Scattering Sensitivity in a Single Shot.
Kagias, Matias; Wang, Zhentian; Villanueva-Perez, Pablo; Jefimovs, Konstantins; Stampanoni, Marco
2016-03-01
X-ray scattering imaging can provide complementary information to conventional absorption based radiographic imaging about the unresolved microstructures of a sample. The scattering signal can be accessed with various methods based on coherent illumination, which span from self-imaging to speckle scanning. The directional sensitivity of the existing real space imaging methods is limited to a few directions on the imaging plane and requires scanning of the optical components, or the rotation of either the sample or the imaging setup, in order to cover the full range of possible scattering directions. In this Letter the authors propose a new method that allows the simultaneous acquisition of scattering images in all possible directions in a single shot. This is achieved by a specialized phase grating and a detector with sufficient spatial resolution to record the generated interference fringe. The structural length scale sensitivity of the system can be tuned by varying its geometry for a fixed grating design. Taking into account ongoing developments in the field of compact x-ray sources that allow high brightness and sufficient spatial coherence, the applicability of omnidirectional scattering imaging in industrial and medical settings is boosted significantly. PMID:26991177
Dynamic ray tracing for modeling optical cell manipulation
Sraj, Ihab; Szatmary, Alex C.; Marr, David W. M.; Eggleton, Charles D.
2010-01-01
Current methods for predicting stress distribution on a cell surface due to optical trapping forces are based on a traditional ray optics scheme for fixed geometries. Cells are typically modeled as solid spheres as this facilitates optical force calculation. Under such applied forces however, real and non-rigid cells can deform, so assumptions inherent in traditional ray optics methods begin to break down. In this work, we implement a dynamic ray tracing technique to calculate the stress distribution on a deformable cell induced by optical trapping. Here, cells are modeled as three-dimensional elastic capsules with a discretized surface with associated hydrodynamic forces calculated using the Immersed Boundary Method. We use this approach to simulate the transient deformation of spherical, ellipsoidal and biconcave capsules due to external optical forces induced by a single diode bar optical trap for a range of optical powers. PMID:20721060
Ray tracing and ECRH absorption modeling in the HSX stellarator
NASA Astrophysics Data System (ADS)
Weir, G. M.; Likin, K. M.; Marushchenko, N. B.; Turkin, Y.
2015-09-01
To increase flexibility in ECRH experiments on the helically symmetric experiment (HSX), a second gyrotron and transmission line have been installed. The second antenna includes a steerable mirror for off-axis heating, and the launched power may be modulated for use in heat pulse propagation experiments. The extraordinary wave at the second harmonic of the electron gyrofrequency or the ordinary wave at the fundamental resonance are used for plasma start-up and heating on HSX. The tracing visualized ray tracing code (Marushchenko et al 2007 Plasma Fusion Res. 2 S1129) is used to estimate single-pass absorption and to model multi-pass wave damping in the three-dimensional HSX geometry. The single-pass absorption of the ordinary wave at the fundamental resonance is calculated to be as high as 30%, while measurements of the total absorption indicate that 45% of the launched power is absorbed. A multi-pass ray tracing model correctly predicts the experimental absorption and indicates that the launched power is absorbed within the plasma core (r/a≤slant 0.2 ).
Development of 2D soft X-ray measurement system in the large helical device.
Takemura, Y; Ohdachi, S; Watanabe, K Y; Du, X D
2014-11-01
A fast two-dimensional soft X-ray camera using silicon photo diode array is being developed in order to investigate high frequency MHD instability with high mode number. The advantage of the adopted diode is a large sensor area of 10 mm × 10 mm and small diode capacitance which enable us to measure signals with the short response time. The characteristic of the prototype is summarized as follows: Channel number is 6 × 8 = 48, detection range 1∼10 keV, the spatial resolution 128 mm at the plasma location, and frequency range DC∼100 kHz. Synthetic image of the prototype in the Large Helical Device is estimated by using perturbation model of MHD mode. PMID:25430317
A GPU Simulation Tool for Training and Optimisation in 2D Digital X-Ray Imaging
Gallio, Elena; Rampado, Osvaldo; Gianaria, Elena; Bianchi, Silvio Diego; Ropolo, Roberto
2015-01-01
Conventional radiology is performed by means of digital detectors, with various types of technology and different performance in terms of efficiency and image quality. Following the arrival of a new digital detector in a radiology department, all the staff involved should adapt the procedure parameters to the properties of the detector, in order to achieve an optimal result in terms of correct diagnostic information and minimum radiation risks for the patient. The aim of this study was to develop and validate a software capable of simulating a digital X-ray imaging system, using graphics processing unit computing. All radiological image components were implemented in this application: an X-ray tube with primary beam, a virtual patient, noise, scatter radiation, a grid and a digital detector. Three different digital detectors (two digital radiography and a computed radiography systems) were implemented. In order to validate the software, we carried out a quantitative comparison of geometrical and anthropomorphic phantom simulated images with those acquired. In terms of average pixel values, the maximum differences were below 15%, while the noise values were in agreement with a maximum difference of 20%. The relative trends of contrast to noise ratio versus beam energy and intensity were well simulated. Total calculation times were below 3 seconds for clinical images with pixel size of actual dimensions less than 0.2 mm. The application proved to be efficient and realistic. Short calculation times and the accuracy of the results obtained make this software a useful tool for training operators and dose optimisation studies. PMID:26545097
A GPU Simulation Tool for Training and Optimisation in 2D Digital X-Ray Imaging.
Gallio, Elena; Rampado, Osvaldo; Gianaria, Elena; Bianchi, Silvio Diego; Ropolo, Roberto
2015-01-01
Conventional radiology is performed by means of digital detectors, with various types of technology and different performance in terms of efficiency and image quality. Following the arrival of a new digital detector in a radiology department, all the staff involved should adapt the procedure parameters to the properties of the detector, in order to achieve an optimal result in terms of correct diagnostic information and minimum radiation risks for the patient. The aim of this study was to develop and validate a software capable of simulating a digital X-ray imaging system, using graphics processing unit computing. All radiological image components were implemented in this application: an X-ray tube with primary beam, a virtual patient, noise, scatter radiation, a grid and a digital detector. Three different digital detectors (two digital radiography and a computed radiography systems) were implemented. In order to validate the software, we carried out a quantitative comparison of geometrical and anthropomorphic phantom simulated images with those acquired. In terms of average pixel values, the maximum differences were below 15%, while the noise values were in agreement with a maximum difference of 20%. The relative trends of contrast to noise ratio versus beam energy and intensity were well simulated. Total calculation times were below 3 seconds for clinical images with pixel size of actual dimensions less than 0.2 mm. The application proved to be efficient and realistic. Short calculation times and the accuracy of the results obtained make this software a useful tool for training operators and dose optimisation studies. PMID:26545097
A GPU Simulation Tool for Training and Optimisation in 2D Digital X-Ray Imaging.
Gallio, Elena; Rampado, Osvaldo; Gianaria, Elena; Bianchi, Silvio Diego; Ropolo, Roberto
2015-01-01
Conventional radiology is performed by means of digital detectors, with various types of technology and different performance in terms of efficiency and image quality. Following the arrival of a new digital detector in a radiology department, all the staff involved should adapt the procedure parameters to the properties of the detector, in order to achieve an optimal result in terms of correct diagnostic information and minimum radiation risks for the patient. The aim of this study was to develop and validate a software capable of simulating a digital X-ray imaging system, using graphics processing unit computing. All radiological image components were implemented in this application: an X-ray tube with primary beam, a virtual patient, noise, scatter radiation, a grid and a digital detector. Three different digital detectors (two digital radiography and a computed radiography systems) were implemented. In order to validate the software, we carried out a quantitative comparison of geometrical and anthropomorphic phantom simulated images with those acquired. In terms of average pixel values, the maximum differences were below 15%, while the noise values were in agreement with a maximum difference of 20%. The relative trends of contrast to noise ratio versus beam energy and intensity were well simulated. Total calculation times were below 3 seconds for clinical images with pixel size of actual dimensions less than 0.2 mm. The application proved to be efficient and realistic. Short calculation times and the accuracy of the results obtained make this software a useful tool for training operators and dose optimisation studies.
The elimination of ray tracing in Monte Carlo shielding programs
Bendall, D.E.
1988-01-01
The MONK6 code has clearly demonstrated the advantages of hole tracking, which was devised by Woodcock et at. for use in criticality codes from earlier work by Von Neumann. Hole tracking eliminates ray tracing by introducing, for all materials present in the problem, a pseudo scattering reaction that forward scatters without energy loss. The cross section for this reaction is chosen so that the total cross sections for all the materials are equal at a given energy. By this means, tracking takes place with a constant total cross section everywhere, so there is now no need to ray trace. The present work extends hole tracking to shielding codes, where it functions in tandem with Russian roulette and splitting. An algorithm has been evolved and its performance is compared with the ray-tracking code McBEND. A disadvantage with hole tracking occurs when there is a wide variation in total cross section for materials present. As the tracking uses the total cross section of the material that has the maximum cross section, there can be a large number of pseudo collisions in the materials with low total cross sections. In extreme cases, the advantages of hole tracking can be lost by the by the extra time taken in servicing these pseudo collisions; however, techniques for eliminating this problem are under consideration.
Dynamic ray tracing and its application in triangulated media
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.
Dynamic ray tracing and its application in triangulated media
NASA Astrophysics Data System (ADS)
Rueger, A.
1993-07-01
Hale and Cohen 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 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. 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.
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.
Trans-Ionospheric High Frequency Signal Ray Tracing
NASA Astrophysics Data System (ADS)
Wright, S.; Gillespie, R. J.
2012-09-01
All electromagnetic radiation undergoes refraction as it propagates through the atmosphere. Tropospheric refraction is largely governed by interaction of the radiation with bounded electrons; ionospheric refraction is primarily governed by free electron interactions. The latter phenomenon is important for propagation and refraction of High Frequency (HF) through Extremely High Frequency (EHF) signals. The degree to which HF to EHF signals are bent is dependent upon the integrated refractive effect of the ionosphere: a result of the signal's angle of incidence with the boundaries between adjacent ionospheric regions, the magnitude of change in electron density between two regions, as well as the frequency of the signal. In the case of HF signals, the ionosphere may bend the signal so much that it is directed back down towards the Earth, making over-the-horizon HF radio communication possible. Ionospheric refraction is a major challenge for space-based geolocation applications, where the ionosphere is typically the biggest contributor to geolocation error. Accurate geolocation requires an algorithm that accurately reflects the physical process of a signal transiting the ionosphere, and an accurate specification of the ionosphere at the time of the signal transit. Currently implemented solutions are limited by both the algorithm chosen to perform the ray trace and by the accuracy of the ionospheric data used in the calculations. This paper describes a technique for adapting a ray tracing algorithm to run on a General-Purpose Graphics Processing Unit (GPGPU or GPU), and using a physics-based model specifying the ionosphere at the time of signal transit. This technique allows simultaneous geolocation of significantly more signals than an equivalently priced Central Processing Unit (CPU) based system. Additionally, because this technique makes use of the most widely accepted numeric algorithm for ionospheric ray tracing and a timely physics-based model of the ionosphere
Ray-tracing optical modeling of negative dysphotopsia
NASA Astrophysics Data System (ADS)
Hong, Xin; Liu, Yueai; Karakelle, Mutlu; Masket, Samuel; Fram, Nicole R.
2011-12-01
Negative dysphotopsia is a relatively common photic phenomenon that may occur after implantation of an intraocular lens. The etiology of negative dysphotopsia is not fully understood. In this investigation, optical modeling was developed using nonsequential-component Zemax ray-tracing technology to simulate photic phenomena experienced by the human eye. The simulation investigated the effects of pupil size, capsulorrhexis size, and bag diffusiveness. Results demonstrated the optical basis of negative dysphotopsia. We found that photic structures were mainly influenced by critical factors such as the capsulorrhexis size and the optical diffusiveness of the capsular bag. The simulations suggested the hypothesis that the anterior capsulorrhexis interacting with intraocular lens could induce negative dysphotopsia.
Photorealistic ray tracing to visualize automobile side mirror reflective scenes.
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.
An iterative ray tracing model for ultrasonic nondestructive testing
NASA Astrophysics Data System (ADS)
Ogilvy, J. A.
A three-dimensional ray tracing model is proposed for predicting ultrasonic energy propagation in anisotropic and inhomogeneous materials. The model is designed as an iterative tool capable of calculating energy paths between specified start and end points. The use of the model for assessing defect location and sizing errors in components containing anisotropic or inhomogeneous materials is demonstrated for an austenitic cladding layer and an austenitic steel V-weld. Although the predicted errors are generally small, they are found to be dependent on the nominal probe angles, except for cracks close to the cladding layer, where significant underestimation of the distance between the top of the defect and the cladding occurs.
NASA Astrophysics Data System (ADS)
Engelbrecht, N. E.; Burger, R. A.
2015-12-01
In this study, a novel ab initio cosmic ray (CR) modulation code that solves a set of stochastic transport equations equivalent to the Parker transport equation, and that uses output from a turbulence transport code as input for the diffusion tensor, is introduced. This code is benchmarked with a previous approach to ab initio modulation. The sensitivity of computed galactic CR proton spectra at Earth to assumptions made as to the low-wavenumber behavior of the two-dimensional (2D) turbulence power spectrum is investigated using perpendicular mean free path expressions derived from two different scattering theories. Constraints on the low-wavenumber behavior of the 2D power spectrum are inferred from the qualitative comparison of computed CR spectra with spacecraft observations at Earth. Another key difference from previous studies is that observed and inferred CR intensity spectra at 73 AU are used as boundary spectra instead of the usual local interstellar spectrum. Furthermore, the results presented here provide a tentative explanation as to the reason behind the unusually high galactic proton intensity spectra observed in 2009 during the recent unusual solar minimum.
Engelbrecht, N. E.; Burger, R. A.
2015-12-01
In this study, a novel ab initio cosmic ray (CR) modulation code that solves a set of stochastic transport equations equivalent to the Parker transport equation, and that uses output from a turbulence transport code as input for the diffusion tensor, is introduced. This code is benchmarked with a previous approach to ab initio modulation. The sensitivity of computed galactic CR proton spectra at Earth to assumptions made as to the low-wavenumber behavior of the two-dimensional (2D) turbulence power spectrum is investigated using perpendicular mean free path expressions derived from two different scattering theories. Constraints on the low-wavenumber behavior of the 2D power spectrum are inferred from the qualitative comparison of computed CR spectra with spacecraft observations at Earth. Another key difference from previous studies is that observed and inferred CR intensity spectra at 73 AU are used as boundary spectra instead of the usual local interstellar spectrum. Furthermore, the results presented here provide a tentative explanation as to the reason behind the unusually high galactic proton intensity spectra observed in 2009 during the recent unusual solar minimum.
Personalized x-ray reconstruction of the proximal femur via a non-rigid 2D-3D registration
NASA Astrophysics Data System (ADS)
Yu, Weimin; Zysset, Philippe; Zheng, Guoyan
2015-03-01
In this paper we present a new approach for a personalized X-ray reconstruction of the proximal femur via a non-rigid registration of a 3D volumetric template to 2D calibrated C-arm images. The 2D-3D registration is done with a hierarchical two-stage strategy: the global scaled rigid registration stage followed by a regularized deformable b-spline registration stage. In both stages, a set of control points with uniform spacing are placed over the domain of the 3D volumetric template and the registrations are driven by computing updated positions of these control points, which then allows to accurately register the 3D volumetric template to the reference space of the C-arm images. Comprehensive experiments on simulated images, on images of cadaveric femurs and on clinical datasets are designed and conducted to evaluate the performance of the proposed approach. Quantitative and qualitative evaluation results are given, which demonstrate the efficacy of the present approach.
Ray tracing method in phase space for two-dimensional optical systems.
Filosa, C; Ten Thije Boonkkamp, J H M; IJzerman, W L
2016-05-01
Ray tracing is a forward method to calculate the photometric variables at the target of a non-imaging optical system. In this paper, a new ray tracing technique is presented to improve the accuracy and to reduce the computational time of the classical ray tracing approach. The method is based on the phase space representation of the source and the target of the optical system, and it is applied to a two-dimensional TIR-collimator. The strength of the method lies in tracing fewer rays through the system. Only rays that lie in the meridional plane are considered. A procedure that disregards rays in smooth regions in phase space, where the luminance is continuous, is implemented and only the rays close to discontinuities are traced. The efficiency of the method is demonstrated by numerical simulations that compare the new method with Monte Carlo ray tracing. The results show that the phase space approach is faster and more accurate than the already existing ray tracing method; moreover the phase space method converges as one over the number of rays traced unlike Monte Carlo ray tracing in which the speed of convergence is proportional to one over the square root of the number of rays.
Ray tracing method in phase space for two-dimensional optical systems.
Filosa, C; Ten Thije Boonkkamp, J H M; IJzerman, W L
2016-05-01
Ray tracing is a forward method to calculate the photometric variables at the target of a non-imaging optical system. In this paper, a new ray tracing technique is presented to improve the accuracy and to reduce the computational time of the classical ray tracing approach. The method is based on the phase space representation of the source and the target of the optical system, and it is applied to a two-dimensional TIR-collimator. The strength of the method lies in tracing fewer rays through the system. Only rays that lie in the meridional plane are considered. A procedure that disregards rays in smooth regions in phase space, where the luminance is continuous, is implemented and only the rays close to discontinuities are traced. The efficiency of the method is demonstrated by numerical simulations that compare the new method with Monte Carlo ray tracing. The results show that the phase space approach is faster and more accurate than the already existing ray tracing method; moreover the phase space method converges as one over the number of rays traced unlike Monte Carlo ray tracing in which the speed of convergence is proportional to one over the square root of the number of rays. PMID:27140377
Wolter X-Ray Microscope Computed Tomography Ray-Trace Model with Preliminary Simulation Results
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
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.
NASA Technical Reports Server (NTRS)
Kastner, S. O.
1979-01-01
The convex curved crystal X-ray spectrograph has recently seen increasing use for the spectral analysis of transient plasmas. The present paper describes the calculation of ray paths through the spectrograph for both localized and extended sources. The method traces a ray from any given source point to its point of diffraction by the curved crystal and then to the imaging circle, where the image point is obtained. Application of the ray tracing method is made to some actual experimental configurations to obtain resolution values and source sizes. Wavelength calibrations are obtainable with the ray tracing method in advance of instrument construction.
Testing the validity of the ray-tracing code GYOTO
NASA Astrophysics Data System (ADS)
Grould, M.; Paumard, T.; Perrin, G.
2016-06-01
Context. In the next few years, the near-infrared interferometer GRAVITY will be able to observe the Galactic center. Astrometric data will be obtained with an anticipated accuracy of 10 μas. To analyze these future data, we have developed a code called GYOTO to compute orbits and ray-trace images. Aims: We want to assess the validity and accuracy of GYOTO in a variety of contexts, in particular for stellar astrometry in the Galactic center. Furthermore, we want to tackle and complete a study made on the astrometric displacements that are due to lensing effects of a star of the central parsec with GYOTO. Methods: We first validate GYOTO in the weak-deflection limit (WDL) by studying primary caustics and primary critical curves obtained for a Kerr black hole. We compare GYOTO results to available analytical approximations and estimate GYOTO errors using an intrinsic estimator. In the strong-deflection limit (SDL), we choose to compare null geodesics computed by GYOTO and the ray-tracing code named Geokerr. Finally, we use GYOTO to estimate the apparent astrometric displacements of a star for different angles from Sagittarius A* (Sgr A*). Results: In the WDL, we find a good coherence between GYOTO results and approximations. The maximal difference is around 10-5μas. Our intrinsic estimator finds a conservative uncertainty estimate also around 10-5μas. In the SDL, both ray-tracing codes find the same photon's coordinates with a maximal difference of about 10-3μas. The shift of a star located behind the plane of sky containing Sgr A* is consistent with the current study. In addition, the effect of lensing on any star in this plane of sky is a radial shift by 5 μas, independent of the distance from Sgr A* up to a very large distance. Conclusions: We have demonstrated that GYOTO is accurate to a very high level, orders of magnitude better than the GRAVITY requirements. GYOTO is also valid in weak- and strong-deflection regimes and for very long integrations. At the
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).
Calibration model of a dual gain flat panel detector for 2D and 3D x-ray imaging
Schmidgunst, C.; Ritter, D.; Lang, E.
2007-09-15
The continuing research and further development in flat panel detector technology have led to its integration into more and more medical x-ray systems for two-dimensional (2D) and three-dimensional (3D) imaging, such as fixed or mobile C arms. Besides the obvious advantages of flat panel detectors, like the slim design and the resulting optimum accessibility to the patient, their success is primarily a product of the image quality that can be achieved. The benefits in the physical and performance-related features as opposed to conventional image intensifier systems (e.g., distortion-free reproduction of imaging information or almost linear signal response over a large dynamic range) can be fully exploited, however, only if the raw detector images are correctly calibrated and postprocessed. Previous procedures for processing raw data contain idealizations that, in the real world, lead to artifacts or losses in image quality. Thus, for example, temperature dependencies or changes in beam geometry, as can occur with mobile C arm systems, have not been taken into account up to this time. Additionally, adverse characteristics such as image lag or aging effects have to be compensated to attain the best possible image quality. In this article a procedure is presented that takes into account the important dependencies of the individual pixel sensitivity of flat panel detectors used in 2D or 3D imaging and simultaneously minimizes the work required for an extensive recalibration. It is suitable for conventional detectors with only one gain mode as well as for the detectors specially developed for 3D imaging with dual gain read-out technology.
A FORMALISM FOR COVARIANT POLARIZED RADIATIVE TRANSPORT BY RAY TRACING
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.
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.
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.
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.
Image transfer through cirrus clouds. I. Ray trace analysis and wave-front reconstruction.
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.
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.
Geometry-invariant gradient refractive index lens: analytical ray tracing
NASA Astrophysics Data System (ADS)
Bahrami, Mehdi; Goncharov, Alexander V.
2012-05-01
A new class of gradient refractive index (GRIN) lens is introduced and analyzed. The interior iso-indicial contours mimic the external shape of the lens, which leads to an invariant geometry of the GRIN structure. The lens model employs a conventional surface representation using a coincoid of revolution with a higher-order aspheric term. This model has a unique feature, namely, it allows analytical paraxial ray tracing. The height and the angle of an arbitrary incident ray can be found inside the lens in a closed-form expression, which is used to calculate the main optical characteristics of the lens, including the optical power and third-order monochromatic aberration coefficients. Moreover, due to strong coupling of the external surface shape to the GRIN structure, the proposed GRIN lens is well suited for studying accommodation mechanism in the eye. To show the power of the model, several examples are given emphasizing the usefulness of the analytical solution. The presented geometry-invariant GRIN lens can be used for modeling and reconstructing the crystalline lens of the human eye and other types of eyes featuring a GRIN lens.
A General Computer Program for Ionospheric Ray-Tracing
NASA Technical Reports Server (NTRS)
Gonzales, Victor H.
1961-01-01
The study of the ionosphere using the Faraday rotation effect has been undertaken recently by means of rocket, satellite, and moon echo experiments. Different approximations have been used by different authors, resulting in methods with different degrees of complexity, and it is possible to say that the more accurate a method is, the more difficult its application becomes. However, the use of modern high-speed digital computers offers the possibility of using more complex methods in the solution of this problem, The program described in this report was written for the ILLIAC, the digital computer of the University of Illinois. Only the general features common to most digital computers will be mentioned. This program was prepared having in mind the analysis of the Faraday rotation effect, as recorded from artificial satellites. It is intended to be as general as possible in the conditions imposed on the assumed propagating medium: specifically there are no restrictions on the models of the electron density distribution and the earth's magnetic fields. long as the ray theory Ls valid. The program will trace separately the ordinary and the extraordinary mode, and it will find the virtual phase path length of a ray of each mode between the transmitter (satellite) and a receiver (station). The difference between respective phase path-lengths is related to the Faraday rotation through a constant which depends on the frequency.
Accurate and fast stray radiation calculation based on improved backward ray tracing.
Yang, Liu; XiaoQiang, An; Qian, Wang
2013-02-01
An improved method of backward ray tracing is proposed according to the theory of geometrical optics and thermal radiation heat transfer. The accuracy is essentially raised comparing to the traditional backward ray tracing because ray orders and weight factors are taken into account and the process is designed as sequential and recurring steps to trace and calculate different order stray lights. Meanwhile, it needs very small computation comparing to forward ray tracing because irrelevant surfaces and rays are excluded from the tracing. The effectiveness was verified in the stray radiation analysis for a cryogenic infrared (IR) imaging system, as the results coincided with the actual stray radiation irradiance distributions in the real images. The computation amount was compared with that of forward ray tracing in the narcissus calculation for another cryogenic IR imaging system, it was found that to produce the same accuracy result, the computation of the improved backward ray tracing is far smaller than that of forward ray tracing by at least 2 orders of magnitude.
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.
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.
Point-to-point ionospheric ray tracing by a direct variational method
NASA Astrophysics Data System (ADS)
Coleman, Christopher J.
2011-10-01
While the Haselgrove ray tracing equations are well suited to situations where the ray launch direction is known, they are less effective for situations where only the end points of the ray are known. In such cases, many rays must be traced from the launch point in order to home in on the landing point. An alternative approach is to directly solve the variational principle from which the Haselgrove equations are derived. Such an approach is well suited to the point-to-point ray tracing, but poses several technical difficulties. In this paper we overcome these difficulties and show that a direct approach can indeed provide an effective means of point-to-point ray tracing.
Analysis of numerically specified multireflector antennas by kinematic and dynamic ray tracing
NASA Astrophysics Data System (ADS)
Kildal, Per-Simon
1990-10-01
A technique for tracing rays and fields with several numerically specified reflectors by using geometrical optics is described. The ray paths are determined by launching individual rays from the feed point and following them by reflection from all the reflector surfaces to the output aperture of the last reflector. This procedure is referred to as kinematic ray tracing. Thereafter, the amplitude, phase and polarization of the E-field is traced along the ray paths to the aperture; this is referred to as dynamic ray tracing. The aperture field is then integrated to find the aperture efficiency, which is factorized into convenient subefficiencies. The technique has been implemented in a computer code that has been used to analyze the proposed new shaped-offset dual-reflector feed for the spherical reflector antenna at the Arecibo Observatory.
NASA Astrophysics Data System (ADS)
Miksat, J.; Müller, T. M.; Wenzel, F.
2008-07-01
Finite difference (FD) simulation of elastic wave propagation is an important tool in geophysical research. As large-scale 3-D simulations are only feasible on supercomputers or clusters, and even then the simulations are limited to long periods compared to the model size, 2-D FD simulations are widespread. Whereas in generally 3-D heterogeneous structures it is not possible to infer the correct amplitude and waveform from 2-D simulations, in 2.5-D heterogeneous structures some inferences are possible. In particular, Vidale & Helmberger developed an approach that simulates 3-D waveforms using 2-D FD experiments only. However, their method requires a special FD source implementation technique that is based on a source definition which is not any longer used in nowadays FD codes. In this paper, we derive a conversion between 2-D and 3-D Green tensors that allows us to simulate 3-D displacement seismograms using 2-D FD simulations and the actual ray path determined in the geometrical optic limit. We give the conversion for a source of a certain seismic moment that is implemented by incrementing the components of the stress tensor. Therefore, we present a hybrid modelling procedure involving 2-D FD and kinematic ray-tracing techniques. The applicability is demonstrated by numerical experiments of elastic wave propagation for models of different complexity.
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)
Computation of rms spot radii by ray tracing. [size determination through telescope
NASA Technical Reports Server (NTRS)
Foreman, J. W., Jr.
1974-01-01
In a ray trace calculation of the rms radius of the spot formed in the image plane of an optical system by a point source object, a decision must be made as to how many rays will be traced to obtain the result. As the number of rays is increased, the rms spot radius is generally found to decrease, apparently approaching a definite lower limit as the number of rays becomes very large. This paper examines the question of how many rays must be traced and what their geometrical distribution within the aperture should be to approach the limiting value of the rms spot radius for an infinite number of rays within an accuracy of approximately 1%.
Harmon, Katherine J; Bennett, Eric E; Gomella, Andrew A; Wen, Han
2014-01-01
The ability to map the phase distribution and lateral coherence of an x-ray wavefront offers the potential for imaging the human body through phase contrast, without the need to deposit significant radiation energy. The classic means to achieve this goal is structured illumination, in which a periodic intensity modulation is introduced into the image, and changes in the phase distribution of the wavefront are detected as distortions of the modulation pattern. Two-dimensional periodic patterns are needed to fully characterize a transverse wavefront. Traditionally, the information in a 2D pattern is retrieved at high resolution by acquiring multiple images while shifting the pattern over a 2D matrix of positions. Here we describe a method to decode 2D periodic patterns with single-axis phase stepping, without either a loss of information or increasing the number of sampling steps. The method is created to reduce the instrumentation complexity of high-resolution 2D wavefront sensing in general. It is demonstrated with motionless electromagnetic phase stepping and a flexible processing algorithm in x-ray dark-field and phase contrast imaging.
Study of improved ray tracing parallel algorithm for CGH of 3D objects on GPU
NASA Astrophysics Data System (ADS)
Cong, Bin; Jiang, Xiaoyu; Yao, Jun; Zhao, Kai
2014-11-01
An improved parallel algorithm for holograms of three-dimensional objects was presented. According to the physical characteristics and mathematical properties of the original ray tracing algorithm for computer generated holograms (CGH), using transform approximation and numerical analysis methods, we extract parts of ray tracing algorithm which satisfy parallelization features and implement them on graphics processing unit (GPU). Meanwhile, through proper design of parallel numerical procedure, we did parallel programming to the two-dimensional slices of three-dimensional object with CUDA. According to the experiments, an effective method of dealing with occlusion problem in ray tracing is proposed, as well as generating the holograms of 3D objects with additive property. Our results indicate that the improved algorithm can effectively shorten the computing time. Due to the different sizes of spatial object points and hologram pixels, the speed has increased 20 to 70 times comparing with original ray tracing algorithm.
Ray tracing method in arbitrarily shaped radial graded-index waveguide.
Tsukada, Kenji; Nihei, Eisuke
2015-10-10
A ray tracing algorithm for an arbitrarily shaped axially symmetric graded index waveguide was proposed. This was achieved by considering the center of the waveguide (optical axis) as a set of discrete points. The refractive index depends on the distance of the ray position from the optical axis. This distance was approximated as the shortest distance between the ray position and a point in the set. Using this algorithm, ray tracing could be performed, regardless of the waveguide configuration. In this study, a precise explanation of the algorithm is given and the errors are evaluated. A technique to reduce computing time is also included.
Fox, Christopher; Romeijn, H. Edwin; Dempsey, James F.
2006-05-15
We present work on combining three algorithms to improve ray-tracing efficiency in radiation therapy dose computation. The three algorithms include: An improved point-in-polygon algorithm, incremental voxel ray tracing algorithm, and stereographic projection of beamlets for voxel truncation. The point-in-polygon and incremental voxel ray-tracing algorithms have been used in computer graphics and nuclear medicine applications while the stereographic projection algorithm was developed by our group. These algorithms demonstrate significant improvements over the current standard algorithms in peer reviewed literature, i.e., the polygon and voxel ray-tracing algorithms of Siddon for voxel classification (point-in-polygon testing) and dose computation, respectively, and radius testing for voxel truncation. The presented polygon ray-tracing technique was tested on 10 intensity modulated radiation therapy (IMRT) treatment planning cases that required the classification of between 0.58 and 2.0 million voxels on a 2.5 mm isotropic dose grid into 1-4 targets and 5-14 structures represented as extruded polygons (a.k.a. Siddon prisms). Incremental voxel ray tracing and voxel truncation employing virtual stereographic projection was tested on the same IMRT treatment planning cases where voxel dose was required for 230-2400 beamlets using a finite-size pencil-beam algorithm. Between a 100 and 360 fold cpu time improvement over Siddon's method was observed for the polygon ray-tracing algorithm to perform classification of voxels for target and structure membership. Between a 2.6 and 3.1 fold reduction in cpu time over current algorithms was found for the implementation of incremental ray tracing. Additionally, voxel truncation via stereographic projection was observed to be 11-25 times faster than the radial-testing beamlet extent approach and was further improved 1.7-2.0 fold through point-classification using the method of translation over the cross product technique.
Pawar, Sunayna S; Koorbanally, Neil A
2014-06-01
A series of novel pyranochromene chalcones and corresponding flavanones were synthesized. This is the first report on the confirmation of the absolute configuration of chromene-based flavanones using X-ray crystallography. These compounds were characterized by 2D NMR spectroscopy, and their assignments are reported herein. The 3D structure of the chalcone 3b and flavanone 4g was determined by X-ray crystallography, and the structure of the flavanone was confirmed to be in the S configuration at C-2.
Validation study of a ray-tracing simulator for focal construct geometry.
Dicken, Anthony; Rogers, Keith; Godber, Simon; Prokopiou, Danae; Shevchuk, Alex; Tranfield, Graham; Evans, Paul
2014-12-01
We present the results of a computer modelling package designed to simulate X-ray diffraction imaging employing focal construct geometry. The paths of coherently diffracted X-rays are modelled by ray-tracing. The results of the study show good agreement between simulated and measured data obtained in the laboratory. The validation of the modelling package permits the rapid optimisation and prototyping of focal construct technology, which has wide applicability in security X-ray imaging.
Labate, L.; Koester, P.; Levato, T.; Gizzi, L. A.
2012-10-15
A novel x-ray diagnostic of laser-fusion plasmas is described, allowing 2D monochromatic images of hot, dense plasmas to be obtained in any x-ray photon energy range, over a large domain, on a single-shot basis. The device (named energy-encoded pinhole camera) is based upon the use of an array of many pinholes coupled to a large area CCD camera operating in the single-photon mode. The available x-ray spectral domain is only limited by the quantum efficiency of scientific-grade x-ray CCD cameras, thus extending from a few keV up to a few tens of keV. Spectral 2D images of the emitting plasma can be obtained at any x-ray photon energy provided that a sufficient number of photons had been collected at the desired energy. Results from recent inertial confinement fusion related experiments will be reported in order to detail the new diagnostic.
Paraxial ray-tracing approach for the simulation of ultrasonic inspection of welds
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.
Exact trace formulas for a class of one-dimensional ray-splitting systems
Dabaghian, Y.; Jensen, R. V.; Blumel, R.
2001-06-01
Using quantum graph theory we establish that the ray-splitting trace formula proposed by Couchman [Phys. Rev. A >46, 6193 (1992)] is exact for a class of one-dimensional ray-splitting systems. Important applications in combinatorics are suggested.
Laser Ray Tracing in a Parallel Arbitrary Lagrangian-Eulerian Adaptive Mesh Refinement Hydrocode
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.
Multiple ray-tracing analysis for EBWH/CD experiments in QUEST
NASA Astrophysics Data System (ADS)
Kalinnikova, E. I.; Idei, H.; Zushi, H.; Hanada, K.; Igami, H.; Kubo, S.; Fukuyama, A.; Nuga, H.
2011-02-01
The power deposition profiles were analyzed with a multiple ray tracing code for the Electron Bernstein Wave Heating and Current Drive (EBWH/CD) experiments in the QUEST. In the EBWH/CD experiments in the QUEST, the O-X-B mode conversion scenario was selected for the plasma current sustainment in the rather low-density case. The algorithm for the wave penetration through evanescent layer beyond a O-mode cutoff position was developed for the multiple-ray analysis. The launching antenna positions were considered to obtain the significant wave absorption in the specific propagating direction using the developed ray-tracing code.
Ray tracing a three-dimensional scene using a hierarchical data structure
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.
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.
An hybrid detector GEM-ASIC for 2-D soft X-ray imaging for laser produced plasma and pulsed sources
NASA Astrophysics Data System (ADS)
Pacella, D.; Claps, G.; De Angelis, R.; Murtas, F.
2016-03-01
The following paper presents a new 2-D detector (`GEMpix') in the soft X-ray range, having a wide dynamic range thanks to its intrisic gain, working in charge integration mode to be used for diagnosing laser produced plasma (LPP) or X-ray pulsed sources. It is a gas detector based on the Gas Electron Multiplier (GEM) technology with a quad-medipix chip as read-out electronics. In our prototype, the substitution of semiconductor material with a gas triple-GEM allows several advantages with respect to the detectors commonly used in LPP, as X-ray CCDs and Micro Channel Plates or Image Plates. In these experiments the configuration Time-over-Threshold (ToT) has been used, to measure the total charge released to the gas and collected by each pixel, integrated over the X-ray burst duration. Intensity response and spatial resolution has been measured first in laboratory for calibration, as function of the voltage applied to the GEMs, in single photon regime with energies between 3.7 and 17 keV. Subsequently it has been tested at the ABC laser facility (ENEA, Frascati). In this case, we measured the X-rays produced when the ABC neodymium laser, with pulse of 50 J and 3 ns time width, hits plane targets of aluminum. 2-D images have been acquired by means of a pinhole configuration with magnification 1.5 and 50 μ m of spatial resolution. The results are encouraging regarding the capability of this imaging detector to work in experiments where soft X-ray emissivity varies over many orders of magnitude.
Lee, Yong Geun; Lee, Jeongjin; Shin, Yeong-Gil; Kang, Ho Chul
2016-01-01
Enhancing 2D angiography while maintaining a low radiation dose has become an important research topic. However, it is difficult to enhance images while preserving vessel-structure details because X-ray noise and contrast blood vessels in 2D angiography have similar intensity distributions, which can lead to ambiguous images of vessel structures. In this paper, we propose a novel and fast vessel-enhancement method for 2D angiography. We apply filtering in the principal component analysis domain for vessel regions and background regions separately, using assumptions based on energy compaction. First, we identify an approximate vessel region using a Hessian-based method. Vessel and non-vessel regions are then represented sparsely by calculating their optimal bases separately. This is achieved by identifying periodic motion in the vessel region caused by the flow of the contrast medium through the blood vessels when viewed on the time axis. Finally, we obtain noise-free images by removing noise in the new coordinate domain for the optimal bases. Our method was validated for an X-ray system, using 10 low-dose sets for training and 20 low-dose sets for testing. The results were compared with those for a high-dose dataset with respect to noise-free images. The average enhancement rate was 93.11±0.71%. The average processing time for enhancing video comprising 50-70 frames was 0.80±0.35s, which is much faster than the previously proposed technique. Our method is applicable to 2D angiography procedures such as catheterization, which requires rapid and natural vessel enhancement. PMID:26483302
Lee, Yong Geun; Lee, Jeongjin; Shin, Yeong-Gil; Kang, Ho Chul
2016-01-01
Enhancing 2D angiography while maintaining a low radiation dose has become an important research topic. However, it is difficult to enhance images while preserving vessel-structure details because X-ray noise and contrast blood vessels in 2D angiography have similar intensity distributions, which can lead to ambiguous images of vessel structures. In this paper, we propose a novel and fast vessel-enhancement method for 2D angiography. We apply filtering in the principal component analysis domain for vessel regions and background regions separately, using assumptions based on energy compaction. First, we identify an approximate vessel region using a Hessian-based method. Vessel and non-vessel regions are then represented sparsely by calculating their optimal bases separately. This is achieved by identifying periodic motion in the vessel region caused by the flow of the contrast medium through the blood vessels when viewed on the time axis. Finally, we obtain noise-free images by removing noise in the new coordinate domain for the optimal bases. Our method was validated for an X-ray system, using 10 low-dose sets for training and 20 low-dose sets for testing. The results were compared with those for a high-dose dataset with respect to noise-free images. The average enhancement rate was 93.11±0.71%. The average processing time for enhancing video comprising 50-70 frames was 0.80±0.35s, which is much faster than the previously proposed technique. Our method is applicable to 2D angiography procedures such as catheterization, which requires rapid and natural vessel enhancement.
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…
A ray tracing model for leaf bidirectional scattering studies
NASA Technical Reports Server (NTRS)
Brakke, T. W.; Smith, J. A.
1987-01-01
A leaf is modeled as a deterministic two-dimensional structure consisting of a network of circular arcs designed to represent the internal morphology of major species. The path of an individual ray through the leaf is computed using geometric optics. At each intersection of the ray with an arc, the specular reflected and transmitted rays are calculated according to the Snell and Fresnel equations. Diffuse scattering is treated according to Lambert's law. Absorption is also permitted but requires a detailed knowledge of the spectral attenuation coefficients. An ensemble of initial rays are chosen for each incident direction with the initial intersection points on the leaf surface selected randomly. The final equilibrium state after all interactions then yields the leaf bidirectional reflectance and transmittance distributions. The model also yields the internal two dimensional light gradient profile of the leaf.
SolTrace: A Ray-Tracing Code for Complex Solar Optical Systems
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.
Ray-tracing method for creeping waves on arbitrarily shaped nonuniform rational B-splines surfaces.
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.
NASA Astrophysics Data System (ADS)
Pouyet, E.; Cotte, M.; Fayard, B.; Salomé, M.; Meirer, F.; Mehta, A.; Uffelman, E. S.; Hull, A.; Vanmeert, F.; Kieffer, J.; Burghammer, M.; Janssens, K.; Sette, F.; Mass, J.
2015-11-01
The chemical and physical alterations of cadmium yellow (CdS) paints in Henri Matisse's The Joy of Life (1905-1906, The Barnes Foundation) have been recognized since 2006, when a survey by portable X-ray fluorescence identified this pigment in all altered regions of the monumental painting. This alteration is visible as fading, discoloration, chalking, flaking, and spalling of several regions of light to medium yellow paint. Since that time, synchrotron radiation-based techniques including elemental and spectroscopic imaging, as well as X-ray scattering have been employed to locate and identify the alteration products observed in this and related works by Henri Matisse. This information is necessary to formulate one or multiple mechanisms for degradation of Matisse's paints from this period, and thus ensure proper environmental conditions for the storage and the display of his works. This paper focuses on 2D full-field X-ray Near Edge Structure imaging, 2D micro-X-ray Diffraction, X-ray Fluorescence, and Fourier Transform Infra-red imaging of the altered paint layers to address one of the long-standing questions about cadmium yellow alteration—the roles of cadmium carbonates and cadmium sulphates found in the altered paint layers. These compounds have often been assumed to be photo-oxidation products, but could also be residual starting reagents from an indirect wet process synthesis of CdS. The data presented here allow identifying and mapping the location of cadmium carbonates, cadmium chlorides, cadmium oxalates, cadmium sulphates, and cadmium sulphides in thin sections of altered cadmium yellow paints from The Joy of Life and Matisse's Flower Piece (1906, The Barnes Foundation). Distribution of various cadmium compounds confirms that cadmium carbonates and sulphates are photo-degradation products in The Joy of Life, whereas in Flower Piece, cadmium carbonates appear to have been a [(partially) unreacted] starting reagent for the yellow paint, a role
NASA Astrophysics Data System (ADS)
Joglekar, Archis; Thomas, Alec
2013-10-01
Here, we present 2D numerical modeling of near critical density plasma using a fully implicit Vlasov-Fokker-Planck code, IMPACTA, which includes self-consistent magnetic fields as well as anisotropic electron pressure terms in the expansion of the distribution function, as well as an implementation of the Boris CYLRAD algorithm through a ray tracing add-on package. This allows to model inverse brehmsstrahlung heating as a laser travels through a plasma by solving the ray tracing equations. Generated magnetic fields (eg. the Biermann battery effect) as well as field advection through heat fluxes from the laser heating is shown. Additionally, perturbations in the plasma density profile arise as a result of the high pressures and flows in the plasma. These perturbations in the plasma density affect the path of the laser traveling through the plasma and modify the heating profile accordingly. The interplay between these effects is discussed in this study.
Tracing Analytic Ray Curves for Light and Sound Propagation in Non-Linear Media.
Mo, Qi; Yeh, Hengchin; Manocha, Dinesh
2016-11-01
The physical world consists of spatially varying media, such as the atmosphere and the ocean, in which light and sound propagates along non-linear trajectories. This presents a challenge to existing ray-tracing based methods, which are widely adopted to simulate propagation due to their efficiency and flexibility, but assume linear rays. We present a novel algorithm that traces analytic ray curves computed from local media gradients, and utilizes the closed-form solutions of both the intersections of the ray curves with planar surfaces, and the travel distance. By constructing an adaptive unstructured mesh, our algorithm is able to model general media profiles that vary in three dimensions with complex boundaries consisting of terrains and other scene objects such as buildings. Our analytic ray curve tracer with the adaptive mesh improves the efficiency considerably over prior methods. We highlight the algorithm's application on simulation of visual and sound propagation in outdoor scenes.
Closed-form analytical solutions for ray tracing in optically anisotropic inhomogeneous media.
Nishidate, Yohei
2013-07-01
Closed-form analytical solutions are obtained for ray tracing in several types of optically anisotropic inhomogeneous media whose optical properties are characterized by a matrix form of the inhomogeneous dielectric tensor in principal coordinates. The first solution is for anisotropic axial media, the second solution is for meridional rays in epsilon-negative metamaterial, and the third solution is an approximate one for rectangular lenses fabricated by molding procedures. The validation of numerical ray-tracing procedures for optically anisotropic inhomogeneous media was widely ignored since the solution was not available, and thus the present solutions are also useful for the validation. Furthermore, as examples of validation, ray trajectories are calculated by the closed-form solutions, and their results are compared with those obtained by a numerical solution of the geodesic equation which can be interpreted as a generalized ray equation.
NASA Technical Reports Server (NTRS)
Cruty, M. R.; Benton, E. V.; Turnbill, C. E.; Philpott, D. E.
1975-01-01
Five pocket mice (Perognathus longimembris) were flown on Apollo XVII, each with a solid-state (plastic) nuclear track detector implanted beneath its scalp. The subscalp detectors were sensitive to HZE cosmic ray particles with a LET greater than or approximately equal to 0.15 million electron volts per micrometer (MeV/micron). A critical aspect of the dosimetry of the experiment involved tracing individual particle trajectories through each mouse head from particle tracks registered in the individual subscalp detectors, thereby establishing a one-to-one correspondence between a trajectory location in the tissue and the presence or absence of a lesion. The other major aspect was the identification of each registered particle. An average of 16 particles with Z greater than or equal to 6 and 2.2 particles with Z greater than or equal to 20 were found per detector. The track density, 29 tracks/sq cm, when adjusted for detection volume, was in agreement with the photographic emulsion data from an area dosimeter located next to the flight package.
Optimizing detector geometry for trace element mapping by X-ray fluorescence
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.
Optimizing detector geometry for trace element mapping by X-ray fluorescence
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
Optimizing detector geometry for trace element mapping by X-ray fluorescence
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
Ray tracing optical analysis of offset solar collector for Space Station solar dynamic system
NASA Technical Reports Server (NTRS)
Jefferies, Kent S.
1988-01-01
OFFSET, a detailed ray tracing computer code, was developed at NASA Lewis Research Center to model the offset solar collector for the Space Station solar dynamic electric power system. This model traces rays from 50 points on the face of the sun to 10 points on each of the 456 collector facets. The triangular facets are modeled with spherical, parabolic, or toroidal reflective surface contour and surface slope errors. The rays are then traced through the receiver aperture to the walls of the receiver. Images of the collector and of the sun within the receiver produced by this code provide insight into the collector receiver interface. Flux distribution on the receiver walls, plotted by this code, is improved by a combination of changes to aperture location and receiver tilt angle. Power loss by spillage at the receiver aperture is computed and is considerably reduced by using toroidal facets.
Ray tracing optical analysis of offset solar collector for space station solar dynamic system
NASA Technical Reports Server (NTRS)
Jefferies, Kent S.
1988-01-01
OFFSET, a detailed ray tracing computer code, was developed at NASA Lewis Research Center to model the offset solar collector for the Space Station solar dynamic electric power system. This model traces rays from 50 points on the face of the Sun to 10 points on each of the 456 collector facets. The triangular facets are modeled with spherical, parabolic, or toroidal reflective surface contour and surface slope errors. The rays are then traced through the receiver aperture to the walls of the receiver. Images of the collector and of the Sun within the receiver produced by this code provide insight into the collector receiver interface. Flux distribution on the receiver walls, plotted by this code, is improved by a combination of changes to aperture location and receiver tilt angle. Power loss by spillage at the receiver aperture is computed and is considerably reduced by using toroidal facets.
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.
Three-dimensional ray-tracing model for the study of advanced refractive errors in keratoconus.
Schedin, Staffan; Hallberg, Per; Behndig, Anders
2016-01-20
We propose a numerical three-dimensional (3D) ray-tracing model for the analysis of advanced corneal refractive errors. The 3D modeling was based on measured corneal elevation data by means of Scheimpflug photography. A mathematical description of the measured corneal surfaces from a keratoconus (KC) patient was used for the 3D ray tracing, based on Snell's law of refraction. A model of a commercial intraocular lens (IOL) was included in the analysis. By modifying the posterior IOL surface, it was shown that the imaging quality could be significantly improved. The RMS values were reduced by approximately 50% close to the retina, both for on- and off-axis geometries. The 3D ray-tracing model can constitute a basis for simulation of customized IOLs that are able to correct the advanced, irregular refractive errors in KC.
Long gamma-ray bursts trace the star formation history
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.
PixFEL: developing a fine pitch, fast 2D X-ray imager for the next generation X-FELs
NASA Astrophysics Data System (ADS)
Ratti, L.; Comotti, D.; Fabris, L.; Grassi, M.; Lodola, L.; Malcovati, P.; Manghisoni, M.; Re, V.; Traversi, G.; Vacchi, C.; Bettarini, S.; Casarosa, G.; Forti, F.; Morsani, F.; Paladino, A.; Paoloni, E.; Rizzo, G.; Benkechkache, M. A.; Dalla Betta, G.-F.; Mendicino, R.; Pancheri, L.; Verzellesi, G.; Xu, H.
2015-10-01
The PixFEL project is conceived as the first stage of a long term research program aiming at the development of advanced X-ray imaging instrumentation for applications at the free electron laser (FEL) facilities. The project aims at substantially advancing the state-of-the-art in the field of 2D X-ray imaging by exploring cutting-edge solutions for sensor development, for integration processes and for readout channel architectures. The main focus is on the development of the fundamental microelectronic building blocks for detector readout and on the technologies for the assembly of a multilayer module with minimum dead area. This work serves the purpose of introducing the main features of the project, together with the simulation results leading to the first prototyping run.
Plasma wave signatures in the magnetotail reconnection region - MHD simulation and ray tracing
NASA Technical Reports Server (NTRS)
Omura, Yoshiharu; Green, James L.
1993-01-01
An MHD simulation was performed to obtain a self-consistent model of magnetic field and plasma density near the X point reconnection region. The MHD model was used to perform extensive ray tracing calculations in order to clarify the propagation characteristics of the plasma waves near the X point reconnection region. The dynamic wave spectra possibly observed by the Geotail spacecraft during a typical cross-tail trajectory are reconstructed. By comparing the extensive ray tracing calculations with the plasma wave data from Geotail, it is possible to perform a kind of 'remote sensing' to identify the location and structure of potential X point reconnection regions.
Liu, Z-Y; Guo, L-X; Meng, X
2013-08-01
A three-dimensional ray-tracing model for the use of the uniform theory of diffraction and geometrical optics in radio channel characterizations of indoor environments is presented in this paper. Based on the environment information chosen by the proposed modeling approach, the model is effectively applied by utilizing a technique in which multiple reflections, transmissions, and diffractions are considered via the ray-path classification into four different categories. Ray paths belonging to each ray category are determined by using different methods. Our theoretical results are compared with narrowband and wideband measurements. The good agreement with these measurements indicates that our prediction model works well for such indoor communication applications.
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.
A boundary integral formalism for stochastic ray tracing in billiards.
Chappell, David J; Tanner, Gregor
2014-12-01
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.
A boundary integral formalism for stochastic ray tracing in billiards
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.
Ray tracing calculations of the output from germanium slab lasers
Plowes, J. A.; Holden, P. B.; Pert, G. J.; Healy, S. B.; Kingston, A. E.; Roberts, E.
1995-05-01
A 3D Raytracing code is used, as a post processor, to simulate experimental observables, such as divergences, deflected angle, and output intensity, from a 1 1/2 D fluid code. The latter self consistently treats the plasma expansion with the atomic physics of the Ne-like ion. The results presented relate to two separate experiments. First, an experiment carried out at R. A. L. where Ge slab targets, of varying lengths, were irradiated at driving laser intensities in the range 0.8{yields}2.3x10{sup 13} W cm{sup -2}. Results presented here are for the 236 A line and good agreement is found with experiment. Also presented, are simulations which relate to an experiment carried out at Osaka University, where a 4 cm Ge slab target, with a curvature from 0 to 20 mrad, along the lasing axis, was irradiated. General agreement with experiment is obtained. Tightening in the output beam, with increasing curvature, can clearly be seen.
Modeling and Measurement of 3D Deformation of Scoliotic Spine Using 2D X-ray Images
NASA Astrophysics Data System (ADS)
Li, Hao; Leow, Wee Kheng; Huang, Chao-Hui; Howe, Tet Sen
Scoliosis causes deformations such as twisting and lateral bending of the spine. To correct scoliotic deformation, the extents of 3D spinal deformation need to be measured. This paper studies the modeling and measurement of scoliotic spine based on 3D curve model. Through modeling the spine as a 3D Cosserat rod, the 3D structure of a scoliotic spine can be recovered by obtaining the minimum potential energy registration of the rod to the scoliotic spine in the x-ray image. Test results show that it is possible to obtain accurate 3D reconstruction using only the landmarks in a single view, provided that appropriate boundary conditions and elastic properties are included as constraints.
Erturk, Sakine Sebnem; Del Guerra, Alberto
2013-06-01
We have developed a fast, user friendly, ray-tracing program, "CSIM" for low-energy gamma rays (up to ∼200keV) to simulate the performance characteristics of parallelhole collimators. We have used a ray-tracing approach to find the sensitivity and resolution of the parallelhole collimator by including the penetration of photons through the collimator due to the finite attenuation of the collimator material. "CSIM" can calculate the sensitivity of the collimator, the geometric and penetrating photon ratios, and the 1D and 2D point source response functions (PSF) with the statistical uncertainty for different hole shapes (e.g. square, hexagonal, and cylindrical). We have used "CSIM" to simulate the collimator of the YAP-(S)PETII small animal scanner. We present the analysis of the YAP-(S)PETII scanner round-hole parallel collimator designed for nuclear medicine imaging at 140keV. For this aim, different designs have been considered for a variety of source-collimator distances (b=5, 10, 15, 20cm). Resolution and sensitivity characteristics have been plotted as a function of the collimator thickness and the diameter of the hole. For each value of the source-collimator distance, and for each collimator thickness investigated, the trade-off between sensitivity and spatial resolution has been given as a series of characteristic curves. Then, we compare our simulated resolution and sensitivity results to the analytically calculated ones and found that the analytically calculated results for the YAP-(S)PETII scanner collimator are not far away the results predicted by CSIM and also with the experimentally measured resolution values.
NASA Astrophysics Data System (ADS)
Ortega, I.; Coburn, S.; Kassianov, E.; Barnard, J.; Berg, L. K.; Hostetler, C. A.; Hair, J. W.; Ferrare, R. A.; Volkamer, R. M.
2012-12-01
The two Column Aerosol Project (TCAP) investigates uncertainties in the aerosol direct effect in the northern hemisphere mid-latitudes. The DOE Atmospheric Radiation Measurement (ARM) Mobile Facility (AMF) and Mobile Aerosol Observing System (MAOS) provide an opportunity for 1) atmospheric radiation closure studies, and 2) test retrievals of aerosol optical properties in the presence and absence of clouds. This presentation discusses innovative means to access column information about aerosol optical properties in the lower atmosphere from ground based measurements of solar stray light spectra in the hyperspectral domain, i.e., measurements of the Raman Scattering Probability (RSP, the probability that an observed photon has undergone a rotational Raman scattering event), and oxygen dimer slant column densities (O4 SCD) by means of the University of Colorado 2D scanning ground Multi AXis Differential Optical Absorption Spectroscopy (2D-GMAX-DOAS) instrument that was located at the ARM/MAOS site at Cape Cod, MA. We compare retrievals of aerosol optical properties with those retrieved from the MFRSR and the Cimel Sunphotometer, for case studies in the presence/absence of clouds, and assess the need for atmospheric correction of NO2. 2D-GMAX-DOAS also facilitates a link between the ground-based ARM/MAOS dataset and DoE's G1 aircraft, NASA's King Air aircraft, and NASA's OMI satellite (i.e., NO2 vertical column). Early results that explore these linkages are presented for a case study that combines ground based MFRSR, in-situ observations aboard the G1 aircraft, as well as High Spectral Resolution LIDAR aboard the King Air aircraft.
Using Divergent Δ12CH2D2 and Δ13CH3D to Trace the Provenance and Evolution of Methane Gas
NASA Astrophysics Data System (ADS)
Young, E. D.; Freedman, P.; Mills, M.; Rumble, D.
2015-12-01
Measurements of Δ13CH3D (deviations in Δ13CH3D/12CH4 from stochastic; Ono et al. Anal. Chem. v.86, p.6487, 2014) or Δ18 (from (12CH2D2 + 13CH3D)/12CH4; Stolper et al. Science, v.344, p.1500, 2014, ) have been used to infer temperatures of formation of methane gas. However, departures from thermodynamic equilibrium isotopic bond ordering will result from any fractionating process that do not include bond rupture and reformation, including mixing, diffusion, and kinetic processing. This is because the isotopic bond ordering no longer reflects the bulk isotopic composition once fractionation occurs. A direct measure of departures from thermodynamic equilibrium isotopic bond ordering in methane comes from both Δ12CH2D2 and Δ13CH3D in the same gas. Until now, this has not been possible due to instrumental limitations. We have carried out measurements of Δ12CH2D2 and Δ13CH3D in methane gas mixtures using a unique, large-geometry double-focusing isotope ratio mass spectrometer (IRMS), the Panorama, in order to investigate the usefulness of these two mass-18 isotopologues as tracers of mixing of methane sources. This instrument has a dispersion/magnification ratio, the parameter of merit for mass resolving power, of ~ 1400 mm that exceeds that of any other gas-source IRMS by more than 3.5x and is slightly larger than that for large-geometry SIMS instruments. With this geometry we routinely operate with mass resolving power (M/ΔM, 5% and 95%) of 40,000 or greater with useful sensitivity for isotope ratio analysis. For these experiments we mixed two gases with bulk D/H differing by 100 ‰. The results follow theoretical expectations within uncertainties of 0.5 ‰ for Δ12CH2D2 and 0.1 ‰ for Δ13CH3D. Precision is sufficient to detect as little as 10% mixing in this system. This precision would also be capable of detecting subtle departures from equilibrium caused by diffusion and kinetic bond rupture (e.g. CH4 + OH).
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.
Leong, Andrew F. T.; Islam, M. Sirajul; Kitchen, Marcus J.; Fouras, Andreas; Wallace, Megan J.; Hooper, Stuart B.
2013-04-15
Purpose: Described herein is a new technique for measuring regional lung air volumes from two-dimensional propagation-based phase contrast x-ray (PBI) images at very high spatial and temporal resolution. Phase contrast dramatically increases lung visibility and the outlined volumetric reconstruction technique quantifies dynamic changes in respiratory function. These methods can be used for assessing pulmonary disease and injury and for optimizing mechanical ventilation techniques for preterm infants using animal models. Methods: The volumetric reconstruction combines the algorithms of temporal subtraction and single image phase retrieval (SIPR) to isolate the image of the lungs from the thoracic cage in order to measure regional lung air volumes. The SIPR algorithm was used to recover the change in projected thickness of the lungs on a pixel-by-pixel basis (pixel dimensions {approx}16.2 {mu}m). The technique has been validated using numerical simulation and compared results of measuring regional lung air volumes with and without the use of temporal subtraction for removing the thoracic cage. To test this approach, a series of PBI images of newborn rabbit pups mechanically ventilated at different frequencies was employed. Results: Regional lung air volumes measured from PBI images of newborn rabbit pups showed on average an improvement of at least 20% in 16% of pixels within the lungs in comparison to that measured without the use of temporal subtraction. The majority of pixels that showed an improvement was found to be in regions occupied by bone. Applying the volumetric technique to sequences of PBI images of newborn rabbit pups, it is shown that lung aeration at birth can be highly heterogeneous. Conclusions: This paper presents an image segmentation technique based on temporal subtraction that has successfully been used to isolate the lungs from PBI chest images, allowing the change in lung air volume to be measured over regions as small as the pixel size. Using
Feasibility of 3D tracking of surgical tools using 2D single plane x-ray projections
NASA Astrophysics Data System (ADS)
Seslija, Petar; Habets, Damiaan F.; Peters, Terry M.; Holdsworth, David W.
2008-03-01
Fluoroscopy is widely used for intra-procedure image guidance, however its planar images provide limited information about the location of the surgical tools or targets in three-dimensional space. An iterative method based on the projection-Procrustes technique can determine the three-dimensional positions and orientations of known sparse objects from a single, perspective projection. We assess the feasibility of applying this technique to track surgical tools by measuring its accuracy and precision through in vitro experiments. Two phantoms were fabricated to perform this assessment: a grid plate phantom with numerous point-targets at regular distances from each other; and a sparse object used as a surgical tool phantom. Two-dimensional projections of the phantoms were acquired using an image intensifier-based C-arm x-ray unit. The locations of the markers projected onto the images were identified and measured using an automated algorithm. The three-dimensional location of the phantom tool tip was identified from these images using the projection-Procrustes technique. The accuracy and precision of the tip localization were used to assess our technique. The average three-dimensional root-mean-square target registration error of the phantom tool tip was 1.8 mm. The average three-dimensional root-mean-square precision of localizing the tool tip was 0.5 mm.
2D soft x-ray system on DIII-D for imaging the magnetic topology in the pedestal region
Shafer, M.W.; Battaglia, D. J.; Unterberg, Ezekial A; Evans, T. E.; Hillis, Donald Lee; Maingi, R.
2010-01-01
A new tangential two-dimensional soft x-ray imaging system (SXRIS) is being designed to examine the edge island structure in the lower X-point region of DIII-D. Plasma shielding and/or amplification of the calculated vacuum islands may play a role in the suppression of edge-localized modes via resonant magnetic perturbations (RMPs). The SXRIS is intended to improve the understanding of three-dimensional (3D) phenomena associated with RMPs. This system utilizes a tangential view with a pinhole imaging system and spectral filtering with beryllium foils. SXR emission is chosen to avoid line radiation and allows suitable signal at the top of a H-mode pedestal where T(e) similar to 1-2 keV. A synthetic diagnostic calculation based on 3D SXR emissivity estimates is used to help assess signal levels and resolution of the design. A signal-to-noise ratio of 10 at 1 cm resolution is expected for the perturbed signals, which are sufficient to resolve most of the predicted vacuum island sizes.
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.
An Energy Conservative Ray-Tracing Method With a Time Interpolation of the Force Field
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.
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.
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.
Ray tracing in a finite-element domain using nodal basis functions.
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
Ray tracing in a finite-element domain using nodal basis functions.
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.
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
Zheng, Guoyan
2009-01-01
The widely used procedure of evaluation of cup orientation following total hip arthroplasty using single standard anteroposterior (AP) radiograph is known inaccurate, largely due to the wide variability in individual pelvic orientation relative to X-ray plate. 2D/3D rigid image registration methods have been introduced for an accurate determination of the post-operative cup alignment with respect to an anatomical reference extracted from the CT data. Although encouraging results have been reported, their extensive usage in clinical routine is still limited. This may be explained by their requirement of a CAD model of the prosthesis, which is often difficult to be organized from the manufacturer due to the proprietary issue, and by their requirement of a pre-operative CT scan, which is not available for most retrospective studies. To address these issues, we developed and validated a statistically deformable 2D/3D registration approach for accurate determination of post-operative cup orientation. No CAD model and pre-operative CT data is required any more. Quantitative and qualitative results evaluated on cadaveric and clinical datasets are given, which indicate the validity of the approach. PMID:20426064
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.
A ray tracing model of gravity wave propagation and breakdown in the middle atmosphere
NASA Technical Reports Server (NTRS)
Schoeberl, M. R.
1985-01-01
Gravity wave ray tracing and wave packet theory is used to parameterize wave breaking in the mesosphere. Rays are tracked by solving the group velocity equations, and the interaction with the basic state is determined by considering the evolution of the packet wave action density. The ray tracing approach has a number of advantages over the steady state parameterization as the effects of gravity wave focussing and refraction, local dissipation, and wave response to rapid changes in the mean flow are more realistically considered; however, if steady state conditions prevail, the method gives identical results. The ray tracing algorithm is tested using both interactive and noninteractive models of the basic state. In the interactive model, gravity wave interaction with the polar night jet on a beta-plane is considered. The algorithm produces realistic polar night jet closure for weak topographic forcing of gravity waves. Planetary scale waves forced by local transfer of wave action into the basic flow in turn transfer their wave action into the zonal mean flow. Highly refracted rays are also found not to contribute greatly to the climatology of the mesosphere, as their wave action is severely reduced by dissipation during their lateral travel.
Statistical Inverse Ray Tracing for Image-Based 3D Modeling.
Liu, Shubao; Cooper, David B
2014-10-01
This paper proposes a new formulation and solution to image-based 3D modeling (aka "multi-view stereo") based on generative statistical modeling and inference. The proposed new approach, named statistical inverse ray tracing, models and estimates the occlusion relationship accurately through optimizing a physically sound image generation model based on volumetric ray tracing. Together with geometric priors, they are put together into a Bayesian formulation known as Markov random field (MRF) model. This MRF model is different from typical MRFs used in image analysis in the sense that the ray clique, which models the ray-tracing process, consists of thousands of random variables instead of two to dozens. To handle the computational challenges associated with large clique size, an algorithm with linear computational complexity is developed by exploiting, using dynamic programming, the recursive chain structure of the ray clique. We further demonstrate the benefit of exact modeling and accurate estimation of the occlusion relationship by evaluating the proposed algorithm on several challenging data sets.
NASA Astrophysics Data System (ADS)
Parthasarathy, P.; Habisreuther, P.; Zarzalis, N.
2012-10-01
The radiative properties of reticulated porous inert media are computationally identified using the real three-dimensional structural data of porous media. The computational grids data are reconstructed from three-dimensional computer tomography scans and magnetic resonance image scans of different reticulated porous media. A ray tracing algorithm is used to track the rays inside the grid structure. Statistically large numbers of rays are traced for their path length and incident angle, which are used to find the probability based equivalent extinction coefficient and scattering phase function. The equivalent extinction coefficients are found for porous media with different porosities and pore densities. The dependency of specular and diffuse scattering phase functions on the porous structure and surface reflectance are also studied.
Exact ray tracing formulas based on a nontrigonometric alternative to Snell's law.
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
NASA Technical Reports Server (NTRS)
Menietti, J. Douglas; Green, James L.; Six, N. Frank; Gulkis, S.
1987-01-01
The Voyager 1 and 2 Planetary Radio Astronomy observations of Io-dependent decametric (DAM) radiation originating from the Southern Hemisphere of Jupiter were compared with the results of three-dimensional model ray tracing calculations of the DAM radiation. The ray trajectories for sources located at constant sub-Io longitudes of 260 and 300 deg were computed for both the Northern and the Southern Jovian Hemisphere sources. The model results of wave propagation agree with the Voyager observations obtained with Io located at 260 and 300 deg in Jovian system III longitude. The agreement between the Voyager observations and the model ray tracings allows identification of the origin of several of the emission components.
Exact ray tracing formulas based on a nontrigonometric alternative to Snell's law.
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.
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.
NASA Astrophysics Data System (ADS)
Jones, M. W. M.; Elgass, K. D.; Junker, M. D.; de Jonge, M. D.; van Riessen, G. A.
2016-04-01
Recent developments in biological X-ray microscopy have allowed structural information and elemental distribution to be simultaneously obtained by combining X-ray ptychography and X-ray fluorescence microscopy. Experimentally, these methods can be performed simultaneously; however, the optimal conditions for each measurement may not be compatible. Here, we combine two distinct measurements of ultrastructure and elemental distribution, with each measurement performed under optimised conditions. By combining optimised ptychography and fluorescence information we are able to determine molar concentrations from two-dimensional images, allowing an investigation into the interactions between the environment sensing filopodia in fibroblasts and extracellular calcium. Furthermore, the biological ptychography results we present illustrate a point of maturity where the technique can be applied to solve significant problems in structural biology.
Trace metal content in aspirin and women's cosmetics via proton induced x-ray emission (PIXE)
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).
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.
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.
Comparison of spherical wave ray tracing and exact boundary value solutions for spherical radomes
NASA Astrophysics Data System (ADS)
Bloom, D. A.; Overfelt, P. L.; White, D. J.
Much radome analysis is based on plane wave ray tracing techniques which combine conceptual simplicity with reasonable accuracy. As increasing demands on the performance of airborne antennas necessitate more accurate methods of analysis for the enclosing radome, an exact idea of the limits of applicability of the ray-optical approximation becomes more critical. In an effort to contribute to this subject, we have taken a single layer spherical radome excited by a dipole source oriented parallel to the z-axis and computed its transmitted electric and magnetic fields using a spherical wave ray tracing technique and also by solving the electromagnetic boundary value problem exactly. The exact solution is used as a standard against which the ray tracing approximation can be compared. In this paper, we compare the field patterns of the two solutions by varying the dipole offset distance, the observation point position, wall thickness, dielectric constant, wavelength, and curvature. Parameter values and the compared field patterns are examined in terms of the theory, and conclusions are drawn as to which parameters affect agreement most strongly.
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.
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.
Hopp, T; Duric, N; Ruiter, N V
2015-03-01
Ultrasound Computer Tomography (USCT) is a promising breast imaging modality under development. Comparison to a standard method like mammography is essential for further development. Due to significant differences in image dimensionality and compression state of the breast, correlating USCT images and X-ray mammograms is challenging. In this paper we present a 2D/3D registration method to improve the spatial correspondence and allow direct comparison of the images. It is based on biomechanical modeling of the breast and simulation of the mammographic compression. We investigate the effect of including patient-specific material parameters estimated automatically from USCT images. The method was systematically evaluated using numerical phantoms and in-vivo data. The average registration accuracy using the automated registration was 11.9mm. Based on the registered images a method for analysis of the diagnostic value of the USCT images was developed and initially applied to analyze sound speed and attenuation images based on X-ray mammograms as ground truth. Combining sound speed and attenuation allows differentiating lesions from surrounding tissue. Overlaying this information on mammograms, combines quantitative and morphological information for multimodal diagnosis. PMID:25456144
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.
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.
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.
Nonparaxial geometrical Ronchi test for spherical mirrors: an inverse ray-tracing approach.
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.
Numerical ray tracing method for an eccentric radial gradient-index rod lens.
Horiuchi, Shuma; Yoshida, Shuhei; Yamamoto, Manabu
2014-10-01
We propose a ray tracing method for a radial gradient-index (GRIN) rod lens with an eccentric refractive index distribution. Radial GRIN rod lenses are typically treated as being rotationally symmetric around the optical axis. However, there are several eccentricities of the refractive index distribution in the transverse section, and an eccentricity point is the position of the highest refractive index with respect to the rod axis. Some manufacturing techniques can introduce these eccentricities in the refractive index distribution, and the effect of eccentricity on the lens performance cannot be neglected in some cases. Ray tracing in an eccentric refractive index distribution is possible by extending the conventional method. This allows analysis of the imaging performance of a radial GRIN rod lens with an eccentric refractive index distribution. Since the proposed method builds on the conventional formalism for a rotationally symmetric refractive index distribution, it is simple and easy to implement.
Stochastic ray tracing for simulation of high intensity focal ultrasound therapy.
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.
Benchmarking stepwise ray-tracing in rings in presence of radiation damping
Meot, F.
2011-03-28
A number of machine design studies, including 'nanobeams', sub-millimeter 'beta*' optics, SR rings, etc., require high accuracy on beam orbit and beam size, reliable evaluation of machine parameters, dynamic apertures, etc. This can only be achieved using high precision simulation tools. Stepwise ray-tracing methods belong in this category of tools, stochastic synchrotron radiation and its effects on an electron beam in a storage ring are simulated here in that manner. Benchmarking of the method against analytical model expectations, using a Chasman-Green cell, is presented. Ray-tracing reproduces very accurately beam parameters associated with synchrotron radiation damping. That makes the method a relevant tool in design studies regarding nanobeams, resonance factories and other e-p collider projects.
Three-surface model for the ray tracing of an imaging acousto-optic tunable filter.
Zhao, Huijie; Li, Chongchong; Zhang, Ying
2014-11-10
A three-surface model is proposed for the ray tracing of an imaging acousto-optic tunable filter (AOTF) in the optical design of an AOTF imaging system. The first and last surfaces are two refractive planes corresponding to the incident and exit facets of the AOTF, while the property of the second surface is defined particularly to describe the change of the ray trace owing to the interaction of the acoustic and optic waves. One parameter, the acoustic angle, is first corrected using the test tuning relation to compensate for the nonideality of the acoustic wave. The model has been verified with a two-piezotransducer AOTF to show its usefulness. The differences between the measured diffracted angles and the modeling value are below 0.01°. The comparison demonstrates the accuracy and the efficiency of the three-surface model.
Nonparaxial geometrical Ronchi test for spherical mirrors: an inverse ray-tracing approach.
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
Analysis of KVN 21m Radio Antenna Optics using Ray-Tracing Method
NASA Astrophysics Data System (ADS)
Bae, Jae-Han; Byun, Do-Young
2009-06-01
In this work, we calculate drop in antenna gain, aperture phase distribution, and antenna pointing shift of KVN(Korean VLBI Network) 21m shaped Cassegrain antenna due to misalignments of antenna optics using ray-tracing method. The misalignments we considered are axial displacement of feed, axial displacement of sub-reflector, lateral displacement of feed, lateral displacement of sub-reflector, and sub-reflector tilt. Calculations are performed not only when these misalignments exist separately, but also when they exist at the same time. Although ray-tracing method is based on geometric optics which does not consider electromagnetic effects, we expect that this work enables us to align antenna optics which give the maximum gain.
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.
Exact synthesis of offset multi-reflector antennas using dynamic and kinematic ray tracing
NASA Astrophysics Data System (ADS)
Kildal, P.-S.
The equations and stepwise procedure of a new synthesis-by-ray tracing method is presented. The usefulness of the technique is demonstrated by synthesizing an offset dual-reflector antenna with low cross-polarization and an offset Gregorian dual-reflector feed for the spherical reflector antenna of the radio telescope in Arecibo. The synthesis method can be extended to synthesize contoured beams.
NASA Technical Reports Server (NTRS)
Menietti, J. D.
1991-01-01
We use an analytical fit to an emission lobe profile together with three-dimensional ray tracing to model the broad-banded smooth Uranian kilometric radiation (UKR). We assume the radiation is gyroemission from sources along magnetic field lines. Using an iterative technique that modifies the lobe function and source region, the results are compared to observations at a frequency of 481 kHz. The best-fit calculations are compared to previously published models and to recent ultraviolet (UV) observations.
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
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.
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.
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
Ray-tracing and physical-optics analysis of the aperture efficiency in a radio telescope.
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.
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.
A data distributed, parallel algorithm for ray-traced volume rendering
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.
Ray-tracing and physical-optics analysis of the aperture efficiency in a radio telescope.
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
Pacella, D.; Pizzicaroli, G.; Romano, A.; Gabellieri, L.; Bellazzini, R.; Brez, A.
2008-03-12
Soft-X ray 2-D imaging on ITER is not considered yet. We propose a new approach, based on a gas detector with a gas electron multiplier (GEM) as amplifying structure and with a two-dimensional readout fully integrated with the front end electronics, through an ASIC developed on purpose. The concept has been already tested by means of a prototype, with 128 pixels, carried out in Frascati in collaboration with INFN-Pisa and tested on FTU in 2001 and NSTX in 2002-2004. Thanks to the photon counting mode, it provides 2-D imaging with high time resolution (sub millisecond), high sensitivity and signal to noise ratio. Its capability of energy discrimination allows the acquisition of pictures in X-ray energy bands or to perform a spectral scan in the full energy interval. We propose the realisation of such kind a detector with a readout microchip (ASIC) equipped with 105600 hexagonal pixels arranged at 70 {mu}m pitch in a 300x352 honeycomb matrix, corresponding to an active area of 2.1x2.1 cm{sup 2}, with a pixel density of 240 pixels/ mm{sup 2}. Each pixel is connected to a charge sensitive amplifier followed by a discriminator of pulse amplitude and counter. The chip integrates more than 16.5 million transistors and it is subdivided in 64 identical clusters, to be read independently each other. An important part of the work will be also the design of the whole detector to fulfil all the constraints and requirements as plasma diagnostic in a tokamak machine. Since the detector has high and controllable intrinsic gain, it works well even at very low photon energy, ranging from 0.2 keV to 10 keV (X-VUV region). This range appears therefore particularly suitable for ITER to monitor the outer part of the plasma. In particular pedestal physics, edge modes, localization and effects of additional heating, boundary plasma control etc. The capability of this proposed detector to work in this energy range is further valuable because solid state detectors are not favorite at low
Hapca, Simona; Baveye, Philippe C.; Wilson, Clare; Lark, Richard Murray; Otten, Wilfred
2015-01-01
There is currently a significant need to improve our understanding of the factors that control a number of critical soil processes by integrating physical, chemical and biological measurements on soils at microscopic scales to help produce 3D maps of the related properties. Because of technological limitations, most chemical and biological measurements can be carried out only on exposed soil surfaces or 2-dimensional cuts through soil samples. Methods need to be developed to produce 3D maps of soil properties based on spatial sequences of 2D maps. In this general context, the objective of the research described here was to develop a method to generate 3D maps of soil chemical properties at the microscale by combining 2D SEM-EDX data with 3D X-ray computed tomography images. A statistical approach using the regression tree method and ordinary kriging applied to the residuals was developed and applied to predict the 3D spatial distribution of carbon, silicon, iron, and oxygen at the microscale. The spatial correlation between the X-ray grayscale intensities and the chemical maps made it possible to use a regression-tree model as an initial step to predict the 3D chemical composition. For chemical elements, e.g., iron, that are sparsely distributed in a soil sample, the regression-tree model provides a good prediction, explaining as much as 90% of the variability in some of the data. However, for chemical elements that are more homogenously distributed, such as carbon, silicon, or oxygen, the additional kriging of the regression tree residuals improved significantly the prediction with an increase in the R2 value from 0.221 to 0.324 for carbon, 0.312 to 0.423 for silicon, and 0.218 to 0.374 for oxygen, respectively. The present research develops for the first time an integrated experimental and theoretical framework, which combines geostatistical methods with imaging techniques to unveil the 3-D chemical structure of soil at very fine scales. The methodology presented
NASA Astrophysics Data System (ADS)
Conrad-Hansen, Lars A.; de Bruijne, Marleen; Lauze, François; Tanko, Laszlo B.; Nielsen, Mads
2006-03-01
In this paper we seek to improve the standard method of assessing the degree of calcification in the lumbar aorta visualized on lateral 2-D X-rays. The semiquantitative method does not take density of calcification within the individual plaques into account and is unable to measure subtle changes in the severity of calcification over time. Both of these parameters would be desirable to assess, since they are the keys to assessing important information on the impact of risk factors and candidate drugs aiming at the prevention of atherosclerosis. As a further step for solving this task, we propose a pixelwise inpainting-based refinement scheme that seeks to optimize the individual plaque shape by maximizing the signal-to-noise ratio. Contrary to previous work the algorithm developped for this study uses a sorted candidate list, which omits possible bias introduced by the choice of starting pixel. The signal-to-noise optimization scheme will be discussed in different settings using TV as well as Harmonic inpainting and comparing these with a simple averaging process.
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.
Improved Mesh Interpolation for Ray Tracing by Wavefront Construction Methods for Anisotropic Media
NASA Astrophysics Data System (ADS)
Gibson, R. L.
2001-12-01
Ray methods are useful for the calculation of Green's tensors for three-dimensional, anisotropic media because they are much faster than more exact algorithms such as finite differences. At the same time, there are significant challenges because of difficulties in implementation, particularly those related to the solution of the two-point problem. Classical shooting methods often either fail to determine a solution and can be very slow. Some approaches, such as eikonal methods, are fast, but they do not compute amplitudes, consider only first arrivals, and cannot be easily applied to anisotropic models. Therefore, they cannot be used to compute Green's tensors. Wavefront construction methods, on the other hand, do evaluate both traveltime and amplitude throughout an earth model (e.g., Lambaré et al., 1996). By tracking propagating wavefronts, the geometry of an entire field of rays can be taken into account, and Green's tensors can be computed for the entire model space. These algorithms begin with a small number of rays traced directly from the source. At regular increments in traveltime, a mesh is constructed from the set of points on all rays at the time of interest. As the wavefront propagates away from the source, new rays are inserted into the mesh based on an interpolation criterion. Previous implementations for isotropic media have typically inserted new rays either when the separation between existing rays exceeds an arbitrary distance or when wavefront curvature exceeds some threshold value. Because most rays are computed for only a portion of the overall time of propagation, the simulation requires less time overall. In our current implementation for anisotropic media, we pose the wavefront construction method as a process of adaptive mesh construction, and we seek to increase the speed of the algorithm in several ways that distinguish it from other approaches. First, rather than applying dynamic ray tracing, we perform only kinematic ray tracing
Computer models in room acoustics: The ray tracing method and the auralization algorithms
NASA Astrophysics Data System (ADS)
Pompei, Anna; Sumbatyan, M. A.; Todorov, N. F.
2009-11-01
Computer algorithms are described for constructing virtual acoustic models of various rooms that should satisfy some specific sound quality criteria. The algorithms are based on the ray tracing method, which, in the general case, allows calculation of the amplitude of an acoustic ray that survived multiple reflections from arbitrary curved surfaces. As a result, calculations of room acoustics are reduced to tracing the trajectories of all the acoustic rays in the course of their propagation with multiple reflections from reflecting surfaces to the point of their complete decay. For this approach to be used, the following physical properties of a room should be known: the geometry of the reflecting surfaces, the absorption and diffusion coefficients on each of these surfaces, and the decay law for rays propagating in air. The proposed models allow for the solution of the important problem of architectural acoustics called the auralization problem, i.e., to predict how any given audio segment will sound in any given hall on the basis of computer simulation alone, without any full-scale testing in specific halls.
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.
A computer program to trace seismic ray distribution in complex two-dimensional geological models
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.
R-LODs: fast LOD-based ray tracing of massive models
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.
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
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.
GRay: A MASSIVELY PARALLEL GPU-BASED CODE FOR RAY TRACING IN RELATIVISTIC SPACETIMES
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.
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
Photorealistic ray tracing of free-space invisibility cloaks made of uniaxial dielectrics.
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
A comprehensive ray tracing study on the impact of solar reflections from glass curtain walls.
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.
Photorealistic ray tracing of free-space invisibility cloaks made of uniaxial dielectrics.
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.
A comprehensive ray tracing study on the impact of solar reflections from glass curtain walls.
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
Spin tracking simulations in AGS based on ray-tracing methods - bare lattice, no snakes -
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
Source location of the Jovian hectometric radiation via ray-tracing technique
NASA Astrophysics Data System (ADS)
Ladreiter, H. P.; Leblanc, Y.
1990-05-01
The source location of the Jovian hectometric radiation (HOM) was investigated by ray tracing using realistic magnetic field and plasma models. The results strongly indicate that the HOM sources lie within the tail-field aurora, whose field lines connect the polar regions to the Jovian magnetic tail, at distances from 2 to 7 Jupiter radii from Jupiter's center. Although the exact source location in magnetic latitude is related to the assumed cone half-angle theta, an HOM source at the tail-field auroral region accounts for a large variety of the phenomena observed so far.
NASA Astrophysics Data System (ADS)
Shi, Guangyuan; Li, Song; Huang, Ke; Li, Zile; Zheng, Guoxing
2016-10-01
We have developed a new numerical ray-tracing approach for LIDAR signal power function computation, in which the light round-trip propagation is analyzed by geometrical optics and a simple experiment is employed to acquire the laser intensity distribution. It is relatively more accurate and flexible than previous methods. We emphatically discuss the relationship between the inclined angle and the dynamic range of detector output signal in biaxial LIDAR system. Results indicate that an appropriate negative angle can compress the signal dynamic range. This technique has been successfully proved by comparison with real measurements.
Ray tracing algorithm for accurate solar irradiance prediction in urban areas.
Vitucci, Enrico M; Falaschi, Federico; Degli-Esposti, Vittorio
2014-08-20
A ray tracing algorithm has been developed to model solar radiation interaction with complex urban environments and, in particular, its effects, including the total irradiance on each surface and overall dissipated power contribution. The proposed model accounts for multiple reflection and diffuse scattering interactions and is based on a rigorous theory, so that the overall power balance is satisfied at the generic surface element. Such approach is validated against measurements in the present work in simple reference scenarios. The results show the importance of multiple-bounce interactions and diffuse scattering to obtain reliable solar irradiance and heat dissipation estimates in urban areas.
CGH calculation with the ray tracing method for the Fourier transform optical system.
Ichikawa, Tsubasa; Yoneyama, Takuo; Sakamoto, Yuji
2013-12-30
Computer-generated holograms (CGHs) are usually displayed on electronic devices. However, the resolution of current output devices is not high enough to display CGHs, so the visual field is very narrow. A method using a Fourier transform optical system has been proposed, to enlarge the size of reconstructed images. This paper describes a method of CGH calculations for the Fourier transform optical system to enlarge the visual field and reconstruct realistic images by using the ray tracing method. This method reconstructs images at arbitrary depths and also eliminates unnecessary light including zero-th order light.
NASA Astrophysics Data System (ADS)
Shi, Guangyuan; Li, Song; Huang, Ke; Li, Zile; Zheng, Guoxing
2016-08-01
We have developed a new numerical ray-tracing approach for LIDAR signal power function computation, in which the light round-trip propagation is analyzed by geometrical optics and a simple experiment is employed to acquire the laser intensity distribution. It is relatively more accurate and flexible than previous methods. We emphatically discuss the relationship between the inclined angle and the dynamic range of detector output signal in biaxial LIDAR system. Results indicate that an appropriate negative angle can compress the signal dynamic range. This technique has been successfully proved by comparison with real measurements.
Infrasonic ray tracing applied to mesoscale atmospheric structures: refraction by hurricanes.
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
Infrasonic ray tracing applied to mesoscale atmospheric structures: refraction by hurricanes.
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.
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.
Practical Considerations in Trace Element Analysis of Bone by Portable X-ray Fluorescence.
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
On multiple scattering in acoustic media: a deterministic Ray Tracing method for random structures.
Brigante, M
2013-03-01
The paper is devoted to computer and experimental simulation of US (ultrasonic) signal propagation in acoustic solids with micro-structure. Any change in the percentage of flaws or pores influences considerably the value of the ultrasonic wave speed. The theoretical analysis is based upon the Ray Tracing algorithm. We calculate numerically the full path of each ray from the transmitter to the receiver, in its multiple reflections between the surfaces of the internal obstacles. The natural experiments are performed in a water basin with some arrays of equal metallic round rods. This simulates the US evaluation of the mechanical properties of concrete. The computer modeling allows us to construct the envelope of the US signal registered at the receiving transducer. Then we simulate the dependence of the wave speed versus porosity. There is a sufficiently good accordance between numerical and experimental results.
NASA Technical Reports Server (NTRS)
Lee, M. K.; Nisbet, J. S.
1975-01-01
Radio wave propagation predictions are described in which modern comprehensive theoretical ionospheric models are coupled with ray-tracing programs. In the computer code described, a network of electron density and collision frequency parameters along a band about the great circle path is calculated by specifying the transmitter and receiver geographic coordinates, time, the day number, and the 2800-MHz solar flux. The ray paths are calculated on specifying the frequency, mode, range of elevation angles, and range of azimuth angles from the great circle direction. The current program uses a combination of the Penn State MKI E and F region models and the Mitra-Rowe D and E region model. Application of the technique to the prediction of satellite to ground propagation and calculation of oblique incidence propagation paths and absorption are described. The implications of the study to the development of the next generation of ionospheric models are discussed.
You, Zhihong; Jiang, Daya; Stamnes, Jakob; Chen, Jianjun; Xiao, Jinghua
2012-12-10
The intensity distribution of light scattered by a capillary tube filled with a liquid is studied using geometrical optics or ray tracing. Several intensity step points are found in the scattering pattern due to contributions from different geometrical rays. The scattering angles of these intensity step points vary with the capillary parameters, i.e., with the inner and outer radii of the capillary wall and the refractive indices of the liquid and the wall material. The relations between the scattering angles of the step points and the capillary parameters are analyzed using the reflection law and Snell's law. A method is developed to determine the capillary parameters from measurements of the scattering angles of the step points. An experiment is designed to provide measured data from which the capillary parameters can be obtained by the proposed method. It is shown that this method provides capillary parameters of high precision.
Tracing X-rays through an L-shaped laterally graded multilayer mirror: a synchrotron application.
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
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.
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.
Accounting for partiality in serial crystallography using ray-tracing principles
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.
[Research on the X-ray fluorescence spectrometry method to determine trace elements in kimberlite].
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.
Trace element profiles in murine Lewis lung carcinoma by radioisotope-induced X-ray fluorescence.
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
[Research on the X-ray fluorescence spectrometry method to determine trace elements in kimberlite].
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
Tsai, Ko-Fan; Chu, Shu-Chun
2016-09-19
The one-time ray-tracing optimization method is a fast way to design LED illumination systems [Opt. Express22, 5357 (2014)10.1364/OE.22.005357]. The method optimizes the performance of LED illumination systems by modifying the LEDs' luminous intensity distribution curve (LIDC) with a freeform lens, instead of modifying the illumination system structure. In finding the LEDs' LIDC for optimizing the illumination system's performance, the LEDs' LIDC found by means of a general gradient descent method can be trapped in a local solution. This study develops a matrix operation method to directly find the global solution of the LEDs' LIDC for the optimization of the illumination system's performance for any initial design of an illumination system structure. As compared with the gradient descent method, using the proposed characteristic matrix operation method to find the best LEDs' LIDC reduces the cost in time by several orders of magnitude. The proposed characteristic matrix operation method ensures that the one-time ray-tracing optimization method is an efficient and reliable method for designing LED illumination systems. PMID:27661876
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.
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.
MCViNE- An object oriented Monte Carlo neutron ray tracing simulation package
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
Fast ray-tracing of human eye optics on Graphics Processing Units.
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.
Tsai, Ko-Fan; Chu, Shu-Chun
2016-09-19
The one-time ray-tracing optimization method is a fast way to design LED illumination systems [Opt. Express22, 5357 (2014)10.1364/OE.22.005357]. The method optimizes the performance of LED illumination systems by modifying the LEDs' luminous intensity distribution curve (LIDC) with a freeform lens, instead of modifying the illumination system structure. In finding the LEDs' LIDC for optimizing the illumination system's performance, the LEDs' LIDC found by means of a general gradient descent method can be trapped in a local solution. This study develops a matrix operation method to directly find the global solution of the LEDs' LIDC for the optimization of the illumination system's performance for any initial design of an illumination system structure. As compared with the gradient descent method, using the proposed characteristic matrix operation method to find the best LEDs' LIDC reduces the cost in time by several orders of magnitude. The proposed characteristic matrix operation method ensures that the one-time ray-tracing optimization method is an efficient and reliable method for designing LED illumination systems.
Ray-tracing technique and imaging properties by a PC slab with neff=-1
NASA Astrophysics Data System (ADS)
Wang, Y.; Chen, Jiabi; Qian, W.
2008-12-01
In recent years, negative refractive media as the representation of new electromagnetic medium has become the front and the very popular researching field, and the production of the flat lens is one of its major applications. In our study, the imaging behaviors by two-dimensional photonic crystal slabs have been investigated systematically. We suggest a ray-tracing technique to discuss the action of photonic crystal slab with negative refraction. The propagation of electromagnetic waves in two-dimensional hexagonal lattice photonic crystal slab is investigated through dispersion characteristics analysis and numerical simulation of field patterns. Imaging and focusing with effective negative refractive index of -1 have been observed in these systems for both polarized waves, that is TE- and TM-polarized point source be considered simultaneously. Based on the exact finite-difference time-domain method to perform numerical simulation and physical analysis, we have demonstrated that the two-dimensional photonic crystal we designed can realize nearly perfect imaging with TM-polarized point source in the near field and far field, and the results are consistent with the ray-tracing technique quite well, while to TE-polarized point source the imaging is not perfect although it have neff=-1 in the same direction.
A versatile ray-tracing code for studying rf wave propagation in toroidal magnetized plasmas
NASA Astrophysics Data System (ADS)
Peysson, Y.; Decker, J.; Morini, L.
2012-04-01
A new ray-tracing code named C3PO has been developed to study the propagation of arbitrary electromagnetic radio-frequency (rf) waves in magnetized toroidal plasmas. Its structure is designed for maximum flexibility regarding the choice of coordinate system and dielectric model. The versatility of this code makes it particularly suitable for integrated modeling systems. Using a coordinate system that reflects the nested structure of magnetic flux surfaces in tokamaks, fast and accurate calculations inside the plasma separatrix can be performed using analytical derivatives of a spline-Fourier interpolation of the axisymmetric toroidal MHD equilibrium. Applications to reverse field pinch magnetic configuration are also included. The effects of 3D perturbations of the axisymmetric toroidal MHD equilibrium, due to the discreteness of the magnetic coil system or plasma fluctuations in an original quasi-optical approach, are also studied. Using a Runge-Kutta-Fehlberg method for solving the set of ordinary differential equations, the ray-tracing code is extensively benchmarked against analytical models and other codes for lower hybrid and electron cyclotron waves.
Immersive Molecular Visualization with Omnidirectional Stereoscopic Ray Tracing and Remote Rendering
Stone, John E.; Sherman, William R.; Schulten, Klaus
2016-01-01
Immersive molecular visualization provides the viewer with intuitive perception of complex structures and spatial relationships that are of critical interest to structural biologists. The recent availability of commodity head mounted displays (HMDs) provides a compelling opportunity for widespread adoption of immersive visualization by molecular scientists, but HMDs pose additional challenges due to the need for low-latency, high-frame-rate rendering. State-of-the-art molecular dynamics simulations produce terabytes of data that can be impractical to transfer from remote supercomputers, necessitating routine use of remote visualization. Hardware-accelerated video encoding has profoundly increased frame rates and image resolution for remote visualization, however round-trip network latencies would cause simulator sickness when using HMDs. We present a novel two-phase rendering approach that overcomes network latencies with the combination of omnidirectional stereoscopic progressive ray tracing and high performance rasterization, and its implementation within VMD, a widely used molecular visualization and analysis tool. The new rendering approach enables immersive molecular visualization with rendering techniques such as shadows, ambient occlusion lighting, depth-of-field, and high quality transparency, that are particularly helpful for the study of large biomolecular complexes. We describe ray tracing algorithms that are used to optimize interactivity and quality, and we report key performance metrics of the system. The new techniques can also benefit many other application domains. PMID:27747138
Fast ray-tracing of human eye optics on Graphics Processing Units.
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
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.
MCViNE- An object oriented Monte Carlo neutron ray tracing simulation package
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.
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.
Exact ray-trace beam for an off-axis paraboloid surface.
Arguijo, Pedro; Scholl, Marija Strojnik
2003-06-01
When an off-axis paraboloidal mirror focuses a parallel beam, the image is formed on one side of the optical axis. For a tilted beam focused by an off-axis paraboloidal mirror, the focus is no longer pointlike (not considering the diffraction effect); rather, it is a distorted spot. This is due to the inherent aberrations of the surface. In addition, there is a change in the focus position. We calculate by exact ray-trace equations the modified wave-front aberration and express it in power series. Our formulation uses the optical path variation along a defined principal ray that we relate to the parameter that describe the surface and the beam angle of incidence. We designate this ray as that reflected by the center of the entrance pupil and field of view. We employ the direction cosines of the principal ray to compute the wave-front aberration function of a beam reflected by an off-axis paraboloid.
NASA Astrophysics Data System (ADS)
Otake, Y.; Schafer, S.; Stayman, J. W.; Zbijewski, W.; Kleinszig, G.; Graumann, R.; Khanna, A. J.; Siewerdsen, J. H.
2012-09-01
Surgical targeting of the incorrect vertebral level (wrong-level surgery) is among the more common wrong-site surgical errors, attributed primarily to the lack of uniquely identifiable radiographic landmarks in the mid-thoracic spine. The conventional localization method involves manual counting of vertebral bodies under fluoroscopy, is prone to human error and carries additional time and dose. We propose an image registration and visualization system (referred to as LevelCheck), for decision support in spine surgery by automatically labeling vertebral levels in fluoroscopy using a GPU-accelerated, intensity-based 3D-2D (namely CT-to-fluoroscopy) registration. A gradient information (GI) similarity metric and a CMA-ES optimizer were chosen due to their robustness and inherent suitability for parallelization. Simulation studies involved ten patient CT datasets from which 50 000 simulated fluoroscopic images were generated from C-arm poses selected to approximate the C-arm operator and positioning variability. Physical experiments used an anthropomorphic chest phantom imaged under real fluoroscopy. The registration accuracy was evaluated as the mean projection distance (mPD) between the estimated and true center of vertebral levels. Trials were defined as successful if the estimated position was within the projection of the vertebral body (namely mPD <5 mm). Simulation studies showed a success rate of 99.998% (1 failure in 50 000 trials) and computation time of 4.7 s on a midrange GPU. Analysis of failure modes identified cases of false local optima in the search space arising from longitudinal periodicity in vertebral structures. Physical experiments demonstrated the robustness of the algorithm against quantum noise and x-ray scatter. The ability to automatically localize target anatomy in fluoroscopy in near-real-time could be valuable in reducing the occurrence of wrong-site surgery while helping to reduce radiation exposure. The method is applicable beyond
Tracing Ambient Air Geochemistry using a Modified X-Ray Fluorescence Filter Method
NASA Astrophysics Data System (ADS)
Steiner, J. C.; Rudolph, E.; Wrice, T.
2002-12-01
Modifications of x-ray fluorescence counting procedures enable tracing of aerosol dispersals related to weather fronts and local weather phenomena. Improved X-ray fluorescence methods for bulk aerosols deposited under positive air pressure conditions onto Millipore filters at 80 liters/hour enable the tracing of geological samples in periods down to one hour. Vacuum-plating aliquots of USGS standards onto 0.2 micron polycarbonate and quartz Millipore filters create standards with a shelf life of several months. The analytical system permits detection of light oxides, such as silica to 10 ppm, and heavy elements, such as iron to 0.5 ppm. These collections allow discriminations to be drawn between dominantly geological, silica-enriched air mass and dominantly iron-enriched air of possible industrial origin. These ambient air collections at 120 feet elevation at City College are used to create possible distinctions in air masses related to points of origin. Splits of aerosol examined by neutron activation and coupled plasma emission spectroscopy agree with x-ray fluorescence methods to within analytical error. Aerosol flux conditions are monitored for speciation using direct examination by scanning electron microscopy with energy dispersive analytical capability plus aerosol physical properties by sun photometry. The latter provides bulk optical transmission at six major wavelengths and estimates for bulk aerosol size properties. Preliminary data show positive photometry links with iron-aerosols with a correlation coefficient with southwesterly wind-driven conditions of seventy percent over a four hour monitoring period. Aerosol flux comparisons with heavy metal populations, Ba, Rb, Zr, La show uniform distributions with iron- and silica-enriched populations indicating a pervasive background condition in the ambient air mass over New York City.
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.
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.
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.
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
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.
An x-ray microprobe beam line for trace element analysis
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.
Modeling of HHFW Heating and Current Drive on NSTX with Ray Tracing and Adjoint Techniques
NASA Astrophysics Data System (ADS)
Mau, T. K.; Ryan, P. M.; Carter, M. D.; Jaeger, E. F.; Swain, D. W.; Phillips, C. K.; Kaye, S.; LeBlanc, B. P.; Rosenberg, A. L.; Wilson, J. R.; Harvey, R. W.; Bonoli, P.
2003-12-01
In recent HHFW current drive experiments on NSTX, relative phase shift of the antenna array was scanned from 30° to 90° to create k∥ spectral peaks between 3 and 8 m-1, for rf power in the 1.1-4.5 MW range. Typical plasma parameters were Ip ˜ 0.5 MA, BT ˜ 0.45 T, and neo ˜ 0.6-3×1019 m-3, and Teo ˜ 0.6-3 keV. In this paper, detailed results from the CURRAY ray tracing code at various time slices of some of the earlier discharges are presented. The complete antenna spectrum is modeled using up to 100 rays with different kφ, and kθ. The rf-driven current is calculated by invoking the adjoint technique that is applicable to toroidal plasmas of all aspect ratios and beta values. In these low β (˜2-3%) discharges, the rf-driven current is peaked on axis and minority ion absorption displays a tendency to increase at lower k∥. Reasonable agreement with inferred results from the voltage measurements has been obtained that points to evidence of current drive, while the calculated power deposition profiles agree very well with the HPRT ray code for these discharges. The use of the adjoint method will become more important in future high β NSTX discharges.
Three-dimensional trace element analysis by confocal X-ray microfluorescence imaging.
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
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.
Simulation of radiation damping in rings, using stepwise ray-tracing methods
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
A ray tracing model of gravity wave propagation and breakdown in the middle atmosphere
NASA Technical Reports Server (NTRS)
Schoeberl, M. R.
1985-01-01
Lindzen (1981, 1984) has considered the effects of monochromatic, steady gravity waves propagating into the upper atmosphere. These waves reach such large amplitudes in the mesosphere that they become convectively unstable. The wave is effectively dissipated by the convection, and the pseudomomentum carried by the wave is transferred to the basic flow. The net effect is to accelerate the background flow to the phase speed of the breaking gravity wave. Schoeberl et al. (1983) have discussed modifications to Lindzen's parameterization. The present paper has the objective to develop a type of parameterization scheme for wave breaking that, in principle, can handle lateral wave propagation. Ray tracing is used to follow the gravity wave packets through varying wind conditions. The theory considered uses both the propagation properties of the wave packet and the concept of the conservation of wave action density to determine the local amplitude and position of the wave packet.
Simulation of radiation damping in rings, using stepwise ray-tracing methods
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.
Introducing GAMER: A fast and accurate method for ray-tracing galaxies using procedural noise
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.
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.
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
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.
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.
Reconstruction of the optical system of the human eye with reverse ray-tracing.
Goncharov, Alexander V; Nowakowski, Maciej; Sheehan, Matthew T; Dainty, Christopher
2008-02-01
We present a practical method for reconstructing the optical system of the human eye from off-axis wavefront measurements. A retinal beacon formed at different locations on the retina allows probing the optical structure of the eye by the outgoing beams that exit the eye through the dilated pupil. A Shack-Hartmann aberrometer measures the amount of wave aberrations in each beam at the exit pupil plane. Wavefront data obtained at different oblique directions is used for tomographic reconstruction by optimizing a generic eye model with reverse ray-tracing. The multi-configuration system is constructed by tracing pre-aberrated beams backwards from each direction through the exit pupil into the optical system of the aberrometer followed by the generic eye model. Matching all wave aberrations measured at each field point is equivalent to minimizing the size of the beacon spots on the retina. The main benefit of having a personalized eye model is the ability to identify the origin of the ocular aberrations and to find the optimal way for their correction.
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.
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.
Parry arc: a polarization lidar, ray-tracing, and aircraft case study.
Sassen, K; Takano, Y
2000-12-20
Using simple ray-tracing simulations, the cause of the rare Parry arc has been linked historically to horizontally oriented columns that display the peculiar ability to fall with a pair of prism faces closely parallel to the ground. Although we understand the aerodynamic forces that orient the long-column axis in the horizontal plane, which gives rise to the relatively common tangent arcs of the 22 degrees halo, the mechanism leading to the Parry crystal orientation has never been resolved adequately. On 16 November 1998, at the University of Utah Facility for Atmospheric Remote Sensing, we studied a cirrus cloud producing a classic upper Parry arc using polarization lidar and an aircraft with a new high-resolution ice crystal imaging probe. Scanning lidar data, which reveal extremely high linear depolarization ratios delta a few degrees off the zenith direction, are simulated with ray-tracing theory to determine the ice crystal properties that reproduce this previously unknown behavior. It is found that a limited range of thick-plate crystal axis (length-to-diameter) ratios from approximately 0.75 to 0.93 generates a maximum delta approximately 2.0-5.0 for vertically polarized 0.532-microm light when the lidar is tilted 1 degrees -2 degrees off the zenith. Halo simulations based on these crystal properties also generate a Parry arc. However, although such particles are abundant in the in situ data in the height interval indicated by the lidar, one still has to invoke an aerodynamic stabilization force to produce properly oriented particles. Although we speculate on a possible mechanism, further research is needed into this new explanation for the Parry arc. PMID:18354687
Tracing the Lowest Propeller Line in Magellanic High-mass X-Ray Binaries
NASA Astrophysics Data System (ADS)
Christodoulou, Dimitris M.; Laycock, Silas G. T.; Yang, Jun; Fingerman, Samuel
2016-09-01
We have combined the published observations of high-mass X-ray binary (HMXB) pulsars in the Magellanic Clouds with a new processing of the complete archival data sets from the XMM-Newton and Chandra observatories in an attempt to trace the lowest propeller line below which accretion to polar caps is inhibited by the centrifugal force and the pulsations from the most weakly magnetized pulsars cease. Previously published data reveal that some of the faster-spinning pulsars with spin periods of P S < 12 s, detected at relatively low X-ray luminosities L X , appear to define such a line in the P S -L X diagram, characterized by a magnetic moment of μ = 3 × 1029 G cm3. This value implies the presence of surface magnetic fields of B ≥ 3 × 1011 G in the compact objects of this class. Only a few quiescent HMXBs are found below the propeller line: LXP4.40 and SXP4.78, for which XMM-Newton and Chandra null detections respectively placed firm upper limits on their X-ray fluxes in deep quiescence; and A0538-66, for which many sub-Eddington detections have never measured any pulsations. On the other hand, the data from the XMM-Newton and Chandra archives show clearly that, during routine observation cycles, several sources have been detected below the propeller line in extremely faint, nonpulsating states that can be understood as the result of weak magnetospheric emission when accretion to the poles is centrifugally stalled or severely diminished. We also pay attention to the anomalous X-ray pulsar CXOU J010043.1-721134 that was reported in HMXB surveys. Its pulsations and locations near and above the propeller line indicate that this pulsar could be accreting from a fossil disk.
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.
Neutrino Pair Annihilation in Collapsars: A Ray-tracing Method in Special Relativity
NASA Astrophysics Data System (ADS)
Harikae, Seiji; Kotake, Kei; Takiwaki, Tomoya
2010-04-01
We develop a numerical scheme and code for estimating the energy and momentum transfer via neutrino pair annihilation (ν + {\\bar{ν}} → e^{-}+ e^{+}), bearing in mind the application to the collapsar models of gamma-ray bursts (GRBs). To calculate the neutrino flux illuminated from the accretion disk, we perform a ray-tracing calculation in the framework of special relativity. The numerical accuracy of the developed code is certified by several tests, in which we show comparisons with the corresponding analytical solutions. Using hydrodynamical data in our collapsar simulation, we estimate the annihilation rates in a post-processing manner. We show that the neutrino energy deposition and momentum transfers are strongest near the inner edge of the accretion disk. The beaming effects of special relativity are found to change the annihilation rates by several factors in the polar funnel region. After the accretion disk settles into a stationary state (typically later than ~9 s from the onset of gravitational collapse), we find that the neutrino-heating timescale in the vicinity of the polar funnel (lsim80 km) can become shorter than the hydrodynamical timescale, indicating that the neutrino-heated outflows can be launched there. We point out that the momentum transfer can play an important role as the energy deposition for the efficient acceleration of neutrino-driven outflows. Our results suggest that the neutrino pair annihilation has a potential importance equal to the conventional magnetohydrodynamic mechanism for igniting the GRB fireballs.
Determining the optical quality of focusing collectors without laser ray tracing
Bendt, P.; Gaul, H.; Rabl, A.
1980-02-01
This paper describes a novel alternative to the laser ray trace technique for evaluating the optical quality of focusing solar collectors. The new method does not require any equipment beyond what is used for measuring collector efficiency; it could therefore become part of routine collector testing. The total optical errors resulting from imperfect specularity and from inaccuracies in reflector position or slope are characterized by an angular standard deviation sigma/sub optical/, the rms deviation of the reflected rays from the design direction. The method is based on the fact that the off-axis performance of a concentrator depends on sigma/sub optical/. An angular scan is performed, i.e., the collector output is measured as a function of misalignment angle over the entire range of angles for which there is measurable output (typically a few degrees). This test should be carried out on a very clear day, with receiver close to ambient temperature (if the latter conditions cannot be satisfied, appropriate corrections are necessary). The parameter sigma/sub optical/ is then determined by a least-squares fit between the measured and the calculated angular scan. We tested the method on a parabolic trough collector manufactured by Hexcel, but it is suitable for parabolic dishes as well. The method appears to be accurate enough to determine sigma/sub optical/ within about 10%.
In situ ray tracing and computational steering for interactive blood flow simulation
NASA Astrophysics Data System (ADS)
Mazzeo, Marco D.; Manos, Steven; Coveney, Peter V.
2010-02-01
Recent algorithm and hardware developments have significantly improved our capability to interactively visualise time-varying flow fields. However, when visualising very large dynamically varying datasets interactively there are still limitations in the scalability and efficiency of these methods. Here we present a rendering pipeline which employs an efficient in situ ray tracing technique to visualise flow fields as they are simulated. The ray casting approach is particularly well suited for the visualisation of large and sparse time-varying datasets, where it is capable of rendering fluid flow fields at high image resolutions and at interactive frame rates on a single multi-core processor using OpenMP. The parallel implementation of our in situ visualisation method relies on MPI, requires no specialised hardware support, and employs the same underlying spatial decomposition as the fluid simulator. The visualisation pipeline allows the user to operate on a commodity computer and explore the simulation output interactively. Our simulation environment incorporates numerous features that can be utilised in a wide variety of research contexts.
Simplifications in gravity wave parameterizations assessed by global ray-tracing modeling
NASA Astrophysics Data System (ADS)
Preusse, P.; Eckermann, S. D.; Ern, M.
2009-04-01
All conventional gravity wave (GW) drag parameterizations, such as the Lindzen, Hines, Warner and McIntyre, and Medvedev and Klaassen schemes, have some fundamental assumptions in common. They generally assume GWs propagate upwards instantaneously and purely vertically in a limited number of horizontal directions and exchange momentum with the background winds by wave breaking only. We here use a global ray tracing experiment to test the validity of these assumptions. The spectral shape of a homogeneous and isotropic launch distribution is tuned so that the model best matches observational data in nothern hemisphere summer. For the tuning zonal means of GW squared temperature amplitudes from SABER and of GW momentum flux estimates from CRISTA were used. The chosen launch distribution is confirmed by comparing global maps and seasonal cycles of simulated GW squared amplitudes with SABER observations. We then calculate GW quantities not measured from space, such as zonal and meridional GW-induced mean-flow accelerations. We quantify the effects on the global acceleration distributions by GW lateral refraction (remote recoil effect), oblique/vertical wave propagation and the number of horizontal directions into which rays are launched at the source. We find meridional accelerations are almost completely suppressed by assuming purely vertical propagation. Launching GWs only into the four canonical directions causes large deviations. For the zonal accelerations changes of the global distributions due to the various simplifications are smaller but still significant.
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.
Twining, B. S.; Baines, S. B.; Fisher, N. S.; Jacobsen, C.; Maser, J.; State Univ. of New York at Stony Brook
2003-03-01
The accumulation of trace metals by planktonic protists influences the growth of primary producers, metal biogeochemical cycling, and metal bioaccumulation in aquatic food chains. Despite their importance, unequivocal measurements of trace element concentrations in individual plankton cells have not been possible to date. We have used the 2-ID-E side-branch hard x-ray microprobe at the Advanced Photon Source to measure trace elements in individual marine plankton cells. This microprobe employs zoneplate optics to produce the sub-micron spatial resolution and low background fluorescence required to produce trace element maps of planktonic protist cells ranging in size from 3 to >50 {micro}m. We have developed preservation, rinsing, and mounting protocols that remove most of the salt from our marine samples, thus simplifying the identification of unknown cells and reducing high Cl-related background fluorescence. We have also developed spectral modeling techniques that account for the frequent overlap of adjacent fluorescence peaks and non-uniform detector response. Finally, we have used parallel soft x-ray transmission and epifluorescence microscopy images to estimate C normalized trace element concentrations, identify functional cell types (e.g., photosynthetic vs. non-photosynthetic), and correlate cell structures with spatial patterns in trace element fluorescence.
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
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.
Mukherjee, Smita; Fauré, Marie-Claude; Goldmann, Michel
2015-01-01
Summary In order to form a nanostructured metallic layer below a Langmuir monolayer, radiolysis synthesis was carried out in an adapted geometry that we call surface X-ray radiolysis. In this procedure, an X-ray beam produced by a synchrotron beamline intercepts the surface of an aqueous metal-ion solution covered by a Langmuir monolayer at an angle of incidence below the critical angle for total internal reflection. Underneath the organic layer, the X-ray beam induces the radiolytic synthesis of a nanostructured metal–organic layer whose ultrathin thickness is defined by the vertical X-ray penetration depth. We have shown that increasing the X-ray flux on the surface, which considerably enhances the kinetics of the silver layer formation, results in a second growth regime of silver nanocrystals. Here the formation of the oriented thin layer is followed by the appearance of a 3D powder of silver clusters. PMID:26734531
Accounting for partiality in serial crystallography using ray-tracing principles
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
Accounting for partiality in serial crystallography using ray-tracing principles.
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.
Asselineau, Charles-Alexis; Zapata, Jose; Pye, John
2015-06-01
A stochastic optimisation method adapted to illumination and radiative heat transfer problems involving Monte-Carlo ray-tracing is presented. A solar receiver shape optimisation case study illustrates the advantages of the method and its potential: efficient receivers are identified using a moderate computational cost.
The forms of trace metals in an Illinois basin coal by x-ray absorption fine structure spectroscopy
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.
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
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.
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.
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
Masui, Hisashi; Nakamura, Shuji; DenBaars, Steven P
2008-01-01
Light extraction from two-dimensional objects is discussed. Analytical calculations in terms of three different parameters have been applied to equiangular polygons to trace light rays during multiple reflections in a polygon. Based on the result that there are a finite number of incident angles in a polygon for a light ray, it was found that the triangle has the least chance to trap light rays among the polygons. The discussion has been extended to parallelograms, which have an advantage in light extraction to rectangles. Placement of a possible light source in polygons is discussed.
NASA Astrophysics Data System (ADS)
Fuschini, Franco; Vitucci, Enrico M.; Barbiroli, Marina; Falciasecca, Gabriele; Degli-Esposti, Vittorio
2015-06-01
Applied for the first time to mobile radio propagation modeling at the beginning of the nineties, ray tracing is now living a second youth. It is probably the best model to assist in the design and planning of future short-range, millimeter-wave wireless systems, where the more limited propagation environment with respect to UHF frequencies allows to overcome traditional high-CPU time limitations while the higher operating frequency makes ray-optics approximations less drastic and allows to achieve an unprecedented level of accuracy. An overview of ray tracing propagation modeling is given in this paper, with a special attention to future prospects and applications. In particular, frontiers of ray-based propagation modeling such as extension to diffuse scattering, multidimensional channel characterization, multiple-input multiple-output (MIMO) capacity assessments, and future applications such as real-time ray tracing are addressed in the paper with reference to the work recently carried out at the University of Bologna.
Solar proton exposure of an ICRU sphere within a complex structure part II: Ray-trace geometry.
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
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.
NASA Astrophysics Data System (ADS)
Apriono, Catur; Rahardjo, Eko Tjipto; Hiromoto, Norihisa
2015-03-01
We study a method for simulating a power-flow density distribution of terahertz-wave focused by a hemispherical Silicon lens antenna. A regular ray-tracing method is not enough to evaluate a correct radiation power-flow because it does not take into account transmittances dependent on angles of incidence at different positions on the spherical boundary of the Si-lens. In this study, we propose a ray-tracing method including Fresnel's transmission coefficients on the surface of a Si-lens for incoming polarized rays. The power-flow-density distribution calculated by the proposed method has a good agreement except for interference and diffraction with the result obtained by an electromagnetic wave simulator. Our method is so simple and reliable that it is useful for designing and evaluating THz optical systems using dielectric lens antennas.
Novel ray tracing method for stray light suppression from ocean remote sensing measurements.
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.
Novel ray tracing method for stray light suppression from ocean remote sensing measurements.
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
Pourghassem, Hossein
2012-01-01
Material detection is a vital need in dual energy X-ray luggage inspection systems at security of airport and strategic places. In this paper, a novel material detection algorithm based on statistical trainable models using 2-Dimensional power density function (PDF) of three material categories in dual energy X-ray images is proposed. In this algorithm, the PDF of each material category as a statistical model is estimated from transmission measurement values of low and high energy X-ray images by Gaussian Mixture Models (GMM). Material label of each pixel of object is determined based on dependency probability of its transmission measurement values in the low and high energy to PDF of three material categories (metallic, organic and mixed materials). The performance of material detection algorithm is improved by a maximum voting scheme in a neighborhood of image as a post-processing stage. Using two background removing and denoising stages, high and low energy X-ray images are enhanced as a pre-processing procedure. For improving the discrimination capability of the proposed material detection algorithm, the details of the low and high energy X-ray images are added to constructed color image which includes three colors (orange, blue and green) for representing the organic, metallic and mixed materials. The proposed algorithm is evaluated on real images that had been captured from a commercial dual energy X-ray luggage inspection system. The obtained results show that the proposed algorithm is effective and operative in detection of the metallic, organic and mixed materials with acceptable accuracy.
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.
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.
Ray tracing of gravity waves as a possible warning system for tornadic storms and hurricanes
NASA Technical Reports Server (NTRS)
Hung, R. J.; Smith, R. E.
1978-01-01
Gravity waves with wave periods of 13 to 15 min and horizontal phase velocities of 90 to 220 m/sec were present in ground-based observations of the upper atmosphere during time periods when tornadoes were occurring and gravity waves with wave periods of 20 to 25 min and horizontal phase velocities of 100 to 200 m/sec were detected when a hurricane was present. Combinations of available neutral atmosphere data and model parameter values were used with a group ray tracing technique in an attempt to locate the sources of these waves. Computed sources of the waves with periods of 13 to 15 min were located within 50 km of the locations where tornadoes touched down from 2 to 4 h later. In the case of the waves with periods of 20 to 25 min it was found that the computed location of the source was roughly where the hurricane would be located 3 h after the waves were excited. The applicability of the present study to a tornado and hurricane warning system is noted.
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.
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
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
Effects of urban microcellular environments on ray-tracing-based coverage predictions.
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.
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.
Sensitivity of power and RMS delay spread predictions of a 3D indoor ray tracing model.
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.
Effects of urban microcellular environments on ray-tracing-based coverage predictions.
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
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.
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.
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.
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.
Comparison of laser ray-tracing and skiascopic ocular wavefront-sensing devices
Bartsch, D-UG; Bessho, K; Gomez, L; Freeman, WR
2009-01-01
Purpose To compare two wavefront-sensing devices based on different principles. Methods Thirty-eight healthy eyes of 19 patients were measured five times in the reproducibility study. Twenty eyes of 10 patients were measured in the comparison study. The Tracey Visual Function Analyzer (VFA), based on the ray-tracing principle and the Nidek optical pathway difference (OPD)-Scan, based on the dynamic skiascopy principle were compared. Standard deviation (SD) of root mean square (RMS) errors was compared to verify the reproducibility. We evaluated RMS errors, Zernike terms and conventional refractive indexes (Sph, Cyl, Ax, and spherical equivalent). Results In RMS errors reading, both devices showed similar ratios of SD to the mean measurement value (VFA: 57.5±11.7%, OPD-Scan: 53.9±10.9%). Comparison on the same eye showed that almost all terms were significantly greater using the VFA than using the OPD-Scan. However, certain high spatial frequency aberrations (tetrafoil, pentafoil, and hexafoil) were consistently measured near zero with the OPD-Scan. Conclusion Both devices showed similar level of reproducibility; however, there was considerable difference in the wavefront reading between machines when measuring the same eye. Differences in the number of sample points, centration, and measurement algorithms between the two instruments may explain our results. PMID:17571088
Stevens, John Colby
2012-12-01
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 SrTiO_{3} 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_{3} 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.
Optimizing Antenna Layout for ITER Low Field Side Reflectometer using 3D Ray Tracing Code
NASA Astrophysics Data System (ADS)
Newbury, Sarah; Zolfaghari, Ali
2014-10-01
The ITER Low Field Side Reflectometer (LFSR) is being designed to provide electron density profile measurements for both the core and edge plasma through the launching of millimeter waves into the plasma and the detection of the signal of the reflected wave by a receive antenna. Because the detection of the received signal is integral to the determination of the density profile, an important goal in designing the LFSR is to optimize the coupling between launch and receive antennas. This project investigates this subject by using Genray, a 3D ray tracing code, to simulate the propagation of millimeter waves launched into and reflected by the plasma for a typical ITER case. Based upon the results of the code, beam footprints will be estimated for different cases in which both the height and toroidal angle of the launch antenna are varied. The footprints will be compared, allowing conclusions to be drawn about the optimal antenna layout for the LFSR. This method will be carried out for various frequencies of both O-mode and X-mode waves, and the effect of the scrape-off layer of the plasma will also be considered.
Ding, Xinrui; Li, Jiasheng; Chen, Qiu; Tang, Yong; Li, Zongtao; Yu, Binhai
2015-02-01
Although the light-emitting diode (LED) has revolutionized lighting, the non-uniformity of its correlated color temperature (CCT) still remains a major concern. In this context, to improve the light distribution performance of remote phosphor LED lamps, we employ a micropatterned array (MPA) optical film fabricated using a low-cost molding process. The parameters of the MPA, including different installation configurations, positioning, and diameters, are optimized by combining the finite-difference time-domain and ray-tracing methods. Results show that the sample with the upward-facing convex-cone MPA film that has a diameter of half of that of the remote phosphor glass, and is tightly affixed to the inward surface of the remote phosphor glass renders a superior light distribution performance. When compared with the case in which no MPA film is used, the deviation of the CCT distribution decreases from 1033 K to 223 K, and the corresponding output power of the sample is an acceptable level of 85.6%. We perform experiments to verify our simulation results, and the two sets of results exhibit a close agreement. We believe that our approach can be used to optimize MPA films for various lighting applications.
Sensitivity of power and RMS delay spread predictions of a 3D indoor ray tracing model.
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
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.
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
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.
Zheng, Guoyan; Zhang, Xuan; Steppacher, Simon D; Murphy, Stephen B; Siebenrock, Klaus A; Tannast, Moritz
2009-09-01
The widely used procedure of evaluation of cup orientation following total hip arthroplasty using single standard anteroposterior (AP) radiograph is known inaccurate, largely due to the wide variability in individual pelvic orientation relative to X-ray plate. 2D-3D image registration methods have been introduced for an accurate determination of the post-operative cup alignment with respect to an anatomical reference extracted from the CT data. Although encouraging results have been reported, their extensive usage in clinical routine is still limited. This may be explained by their requirement of a CAD model of the prosthesis, which is often difficult to be organized from the manufacturer due to the proprietary issue, and by their requirement of either multiple radiographs or a radiograph-specific calibration, both of which are not available for most retrospective studies. To address these issues, we developed and validated an object-oriented cross-platform program called "HipMatch" where a hybrid 2D-3D registration scheme combining an iterative landmark-to-ray registration with a 2D-3D intensity-based registration was implemented to estimate a rigid transformation between a pre-operative CT volume and the post-operative X-ray radiograph for a precise estimation of cup alignment. No CAD model of the prosthesis is required. Quantitative and qualitative results evaluated on cadaveric and clinical datasets are given, which indicate the robustness and the accuracy of the program. HipMatch is written in object-oriented programming language C++ using cross-platform software Qt (TrollTech, Oslo, Norway), VTK, and Coin3D and is transportable to any platform. PMID:19328585
NASA Astrophysics Data System (ADS)
Hopp, Torsten; Duric, Neb; Ruiter, Nicole V.
2012-03-01
Breast cancer is the most common cancer among women. The established screening method to detect breast cancer in an early state is X-ray mammography. However, X-ray frequently provides limited contrast of tumors located within glandular tissue. A new imaging approach is Ultrasound Computer Tomography generating threedimensional volumes of the breast. Three different images are available: reflectivity, attenuation and speed of sound. The correlation of USCT volumes with X-ray mammograms is of interest for evaluation of the new imaging modality as well as for a multimodal diagnosis. Yet, both modalities differ in image dimensionality, patient positioning and deformation state of the breast. In earlier work we proposed a methodology based on Finite Element Method to register speed of sound images with the according mammogram. In this work, we enhanced the methodology to register all three image types provided by USCT. Furthermore, the methodology is now completely automated using image similarity measures to estimate rotations in datasets. A fusion methodology is proposed which combines the information of the three USCT image types with the X-ray mammogram via semitransparent overlay images. The evaluation was done using 13 datasets from a clinical study. The registration accuracy was measured by the displacement of the center of a lesion marked in both modalities. Using the automated rotation estimation, a mean displacement of 10.4 mm was achieved. Due to the clinically relevant registration accuracy, the methodology provides a basis for evaluation of the new imaging device USCT as well as for multimodal diagnosis.
Usage of CO2 microbubbles as flow-tracing contrast media in X-ray dynamic imaging of blood flows.
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.
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.
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.
2005-07-01
Aniso2d is a two-dimensional seismic forward modeling code. The earth is parameterized by an X-Z plane in which the seismic properties Can have monoclinic with x-z plane symmetry. The program uses a user define time-domain wavelet to produce synthetic seismograms anrwhere within the two-dimensional media.
NASA Astrophysics Data System (ADS)
Jang, Hyun-Sook; Yu, Changqian; Hayes, Robert; Granick, Steve
2015-03-01
Polymer vesicles (``polymersomes'') are an intriguing class of soft materials, commonly used to encapsulate small molecules or particles. Here we reveal they can also effectively incorporate nanoparticles inside their polymer membrane, leading to novel ``2D nanocomposites.'' The embedded nanoparticles alter the capacity of the polymersomes to bend and to stretch upon external stimuli.
Kotake, Kei; Yamada, Shoichi
2009-10-20
We propose a ray-tracing method to estimate gravitational waves (GWs) generated by anisotropic neutrino emission in supernova cores. To calculate the gravitational waveforms, we derive analytic formulae in a useful form, which are applicable also for three-dimensional computations. Pushed by evidence of slow rotation prior to core-collapse, we focus on asphericities in neutrino emission and matter motions outside the protoneutron star. Based on the two-dimensional models, which mimic standing accretion shock instability (SASI)-aided neutrino heating explosions, we compute the neutrino anisotropies via the ray-tracing method in a post-processing manner and calculate the resulting waveforms. For simplicity, neutrino absorption and emission by free nucleons, dominant processes outside the protoneutron stars, are only taken into account, while the neutrino scattering and the velocity-dependent terms in the transport equations are neglected. With these computations, it is found that the waveforms exhibit more variety in contrast to the ones previously estimated by the ray-by-ray analysis. In addition to a positively growing feature, which was predicted to determine the total wave amplitudes predominantly, the waveforms are shown to exhibit large negative growth for some epochs during the growth of SASI. These features are found to stem from the excess of neutrino emission in lateral directions, which can be precisely captured by the ray-tracing calculation. Reflecting the nature of SASI which grows chaotically with time, there is little systematic dependence of the input neutrino luminosities on the maximum wave amplitudes. Due to the negative contributions and the neutrino absorptions appropriately taken into account by the ray-tracing method, the wave amplitudes become more than one order of magnitude smaller than the previous estimation, thus making their detections very hard for a Galactic source. On the other hand, it is pointed out that the GW spectrum from matter
NASA Astrophysics Data System (ADS)
Kumar, Dhiraj; Rocadenbosch, Francesc
2013-01-01
The problem of overlap factor (OVF) computation and its near-range sensitivity for medium-size aperture (f/10, f/11) bi-axial tropospheric lidar systems using ray-tracing simulation software is presented. The method revisits both detector and fiber optics coupling alternatives at the telescope focal-plane along with the insertion of a field lens. A sensitivity analysis is carried out as a function of laser divergence, field lens, and detector/fiber positions, detector size, and the fiber's core diameter and numerical aperture. The ray-tracing approach presented here is straightforward and a comparatively much simpler solution than analytical-based methods. Parametric simulations are carried out to show that both approaches are coincident. Insertion of a field lens proves to be an elegant and low sensitivity solution for OVF enhancement, particularly, in the near-range of the lidar.
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.
Kajita, Shin; Nishijima, Daisuke; Hollmann, Eric M.; Ohno, Noriyasu
2009-06-15
A ray tracing code combined with a He I collisional-radiative (CR) model has been developed to investigate effects of radiation trapping on the population distribution of He atoms in a weakly ionized plasma. The code accurately reproduces experimentally observed vertical profiles of emission intensities in a linear plasma device. On the other hand, the CR code and that modified with the optical escape factor method to include the radiation trapping effects show that vertical profiles significantly deviate from measured ones at the periphery of the plasma column. This work therefore demonstrates that accurate matching of line intensity profiles over the entire plasma column requires a ray tracing code, not just an optical escape factor approximation.
He, Wenjun; Fu, Yuegang; Zheng, Yang; Zhang, Lei; Wang, Jiake; Liu, Zhiying; Zheng, Jianping
2013-07-01
The output polarization states of corner cubes (for both uncoated and metal-coated surfaces) with an input beam of arbitrary polarization state and of arbitrary tilt angle to the cube have been analyzed by using the three-dimensional polarization ray-tracing matrix method. The diattenuation and retardance of the corner-cube retroreflector (CCR) for all six different ray paths are calculated, and the relationships to the tilt angle and the tilt orientation angle are shown. When the tilt angle is large, hollow metal-coated CCR is more appropriate than solid metal-coated CCR for the case that the polarization states of output beam should be controlled.
Fokker-Planck/Ray Tracing for Electron Bernstein and Fast Wave Modeling in Support of NSTX
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
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
Roh, Hyun Cheol; Chuck, Roy S; Lee, Jimmy K; Park, Choul Yong
2015-04-01
The aim of this study was to compare the effect of corneal irregularity on astigmatism assessment using automated keratometry (AK) (IOLMaster) versus ray tracing keratometry (Pentacam). This is an observational case series approved by the institutional review board of Dongguk University Hospital, Goyang, South Korea. A total of 207 eyes of 207 cataract patients were included. Preoperative corneal astigmatism was measured by both IOLMaster and Pentacam. Corneal irregularity index (IR) was calculated in Fourier analysis map of Pentacam. AK by IOLMaster and total corneal refractive power (TCRP, 3 mm and 4 mm zone analysis with pupil centered) by Pentacam were selected and the difference between the 2 measurements (delta Δ) was calculated using vector analysis. Ocular residual astigmatism (ORA) after cataract surgery was calculated by subtracting 6-month postoperative refractive astigmatism (RA) measurements from corresponding preoperative values (AK, TCRP3, and TCRP4). The mean irregularity index measured was 0.042 ± 0.019 mm (mean ± standard deviation) and was positively correlated with age and magnitude of corneal astigmatism (P < 0.001 and P < 0.05). The difference (Δ) between TCRPs and AK (ΔTCRPs-AK) was 0.43 ± 0.37 (TCRP3) and 0.39 ± 0.35 (TCRP4) diopters. Linear regression analysis revealed that age (P < 0.001), IR (P < 0.001), and AK (P < 0.001) were positively correlated with ΔTCRPs-AK. In highly irregular corneas (IR over 0.77 diopters: mean + 2 standard deviation), postoperative ORAs calculated using TCRPs were significantly lower than ORAs calculated using AK. Corneal irregularities significantly impact astigmatism assessment by IOLMaster (AK) and Pentacam (TCRPs). Compared with AK, TCRPs were more accurate in predicting postoperative residual astigmatism in highly irregular corneas.
Becker, Kathrin; Stauber, Martin; Schwarz, Frank; Beißbarth, Tim
2015-09-01
We propose a novel 3D-2D registration approach for micro-computed tomography (μCT) and histology (HI), constructed for dental implant biopsies, that finds the position and normal vector of the oblique slice from μCT that corresponds to HI. During image pre-processing, the implants and the bone tissue are segmented using a combination of thresholding, morphological filters and component labeling. After this, chamfer matching is employed to register the implant edges and fine registration of the bone tissues is achieved using simulated annealing. The method was tested on n=10 biopsies, obtained at 20 weeks after non-submerged healing in the canine mandible. The specimens were scanned with μCT 100 and processed for hard tissue sectioning. After registration, we assessed the agreement of bone to implant contact (BIC) using automated and manual measurements. Statistical analysis was conducted to test the agreement of the BIC measurements in the registered samples. Registration was successful for all specimens and agreement of the respective binary images was high (median: 0.90, 1.-3. Qu.: 0.89-0.91). Direct comparison of BIC yielded that automated (median 0.82, 1.-3. Qu.: 0.75-0.85) and manual (median 0.61, 1.-3. Qu.: 0.52-0.67) measures from μCT were significant positively correlated with HI (median 0.65, 1.-3. Qu.: 0.59-0.72) between μCT and HI groups (manual: R(2)=0.87, automated: R(2)=0.75, p<0.001). The results show that this method yields promising results and that μCT may become a valid alternative to assess osseointegration in three dimensions.
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
NASA Astrophysics Data System (ADS)
Kurobori, T.; Miyamoto, Y.; Maruyama, Y.; Yamamoto, T.; Sasaki, T.
2014-05-01
We report novel disk-type X-ray two-dimensional (2-D) imaging detectors utilising Ag-doped phosphate glass and lithium fluoride (LiF) thin films based on the radiophotoluminescence (RPL) and photoluminescence (PL) phenomena, respectively. The accumulated X-ray doses written in the form of atomic-scale Ag-related luminescent centres in Ag-doped glass and F-aggregated centres in LiF thin films were rapidly reconstructed as a dose distribution using a homemade readout system. The 2-D images reconstructed from the RPL and PL detectors are compared with that from the optically stimulated luminescence (OSL) detector. In addition, the optical and dosimetric characteristics of LiF thin films are investigated and evaluated. The possibilities of dose distributions with a high spatial resolution on the order of microns over large areas, a wide dynamic range covering 11 orders of magnitude and a non-destructive readout are successfully demonstrated by combining the Ag-doped glass with LiF thin films.
Lundvall, F; Wragg, D S; Dietzel, P D C; Fjellvåg, H
2016-08-01
Two new coordination polymers were synthesized solvothermally using 4,4'-dimethoxy-3,3'-biphenyldicarboxylic acid (H2dmbpdc), and di- and trivalent metal salts (Cu(NO3)2·2.5H2O and La(NO3)3·6H2O). Their structures were determined by single-crystal X-ray diffraction analysis, and their thermal stability was evaluated by thermogravimetric analysis. The copper compound Cu(dmbpdc)(DMF; N,N-dimethylformamide), CPO-71-Cu, is based on the well known copper acetate paddlewheel secondary building unit. The asymmetric unit comprises one copper cation with one DMF molecule and one linker molecule coordinated. The lanthanum compound La2(dmbpdc)3(DMF)(H2O)3, CPO-72-La, is formed from a dimer of nine-coordinate, edge sharing lanthanum cations. To this dimer, three water molecules and one DMF molecule are coordinated in an ordered fashion. In addition, the asymmetric unit contains three crystallographically unique linker molecules. Both CPO-71-Cu and CPO-72-La form two-dimensional layered structures, and topological analyses reveal sql topologies with point symbol 4(4)·6(2) and vertex symbol 4·4·4·4·6(2)·6(2). The thermal behavior of CPO-71-Cu was investigated in an in situ structural analysis by variable temperature powder- and single-crystal X-ray diffraction. PMID:27469613
2011-12-31
Mesh2d is a Fortran90 program designed to generate two-dimensional structured grids of the form [x(i),y(i,j)] where [x,y] are grid coordinates identified by indices (i,j). The x(i) coordinates alone can be used to specify a one-dimensional grid. Because the x-coordinates vary only with the i index, a two-dimensional grid is composed in part of straight vertical lines. However, the nominally horizontal y(i,j0) coordinates along index i are permitted to undulate or otherwise vary. Mesh2d also assignsmore » an integer material type to each grid cell, mtyp(i,j), in a user-specified manner. The complete grid is specified through three separate input files defining the x(i), y(i,j), and mtyp(i,j) variations.« less
NASA Astrophysics Data System (ADS)
Otake, Y.; Murphy, R. J.; Kutzer, M. D.; Taylor, R. H.; Armand, M.
2014-03-01
Background: Snake-like dexterous manipulators may offer significant advantages in minimally-invasive surgery in areas not reachable with conventional tools. Precise control of a wire-driven manipulator is challenging due to factors such as cable deformation, unknown internal (cable friction) and external forces, thus requiring correcting the calibration intraoperatively by determining the actual pose of the manipulator. Method: A method for simultaneously estimating pose and kinematic configuration of a piecewise-rigid object such as a snake-like manipulator from a single x-ray projection is presented. The method parameterizes kinematics using a small number of variables (e.g., 5), and optimizes them simultaneously with the 6 degree-of-freedom pose parameter of the base link using an image similarity between digitally reconstructed radiographs (DRRs) of the manipulator's attenuation model and the real x-ray projection. Result: Simulation studies assumed various geometric magnifications (1.2-2.6) and out-of-plane angulations (0°-90°) in a scenario of hip osteolysis treatment, which demonstrated the median joint angle error was 0.04° (for 2.0 magnification, +/-10° out-of-plane rotation). Average computation time was 57.6 sec with 82,953 function evaluations on a mid-range GPU. The joint angle error remained lower than 0.07° while out-of-plane rotation was 0°-60°. An experiment using video images of a real manipulator demonstrated a similar trend as the simulation study except for slightly larger error around the tip attributed to accumulation of errors induced by deformation around each joint not modeled with a simple pin joint. Conclusions: The proposed approach enables high precision tracking of a piecewise-rigid object (i.e., a series of connected rigid structures) using a single projection image by incorporating prior knowledge about the shape and kinematic behavior of the object (e.g., each rigid structure connected by a pin joint parameterized by a
Synchrotron X-ray 2D and 3D Elemental Imaging of CdSe/ZnS Quantum dot Nanoparticles in Daphnia Magna
Jackson, B.; Pace, H; Lanzirotti, A; Smith, R; Ranville, J
2009-01-01
The potential toxicity of nanoparticles to aquatic organisms is of interest given that increased commercialization will inevitably lead to some instances of inadvertent environmental exposures. Cadmium selenide quantum dots (QDs) capped with zinc sulfide are used in the semiconductor industry and in cellular imaging. Their small size (<10 nm) suggests that they may be readily assimilated by exposed organisms. We exposed Daphnia magna to both red and green QDs and used synchrotron X-ray fluorescence to study the distribution of Zn and Se in the organism over a time period of 36 h. The QDs appeared to be confined to the gut, and there was no evidence of further assimilation into the organism. Zinc and Se fluorescence signals were highly correlated, suggesting that the QDs had not dissolved to any extent. There was no apparent difference between red or green QDs, i.e., there was no effect of QD size. 3D tomography confirmed that the QDs were exclusively in the gut area of the organism. It is possible that the QDs aggregated and were therefore too large to cross the gut wall.
NASA Technical Reports Server (NTRS)
Huang, C. Y.; Goertz, C. K.
1983-01-01
Gyroresonance and Landau resonance interactions between unducted low-frequency whistler waves and trapped electrons in the earth's plasmasphere have been studied. Ray paths for waves launched near the plasmapause have been traced. In agreement with recent findings by Thorne et al. (1979), waves have been found which return through the equatorial zone with field-aligned wave normal angles. However, when the growth along the ray path is calculated for such waves, assuming an electron distribution function of the form E exp -n sin exp m alpha, it is found that for all the waves considered, the local growth rate becomes negative before plasmapause reflection, limiting the total gain to small values. Most waves reach zero gain before reflection. This is the result of Landau damping at oblique propagation angles, which necessarily occurs before reflection can take place. It is concluded that the concept of cyclic ray paths does not provide an explanation for the generation of unguided plasmaspheric hiss.
NASA Astrophysics Data System (ADS)
Kalisch, Silvio; Trinh, Thai; Ern, Manfred; Preusse, Peter; Chun, Hye-Yeong; Kim, Young-Ha; Eckermann, Steven D.; Riese, Martin
2014-05-01
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. The 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 for 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. Only by including convective GW sources
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.
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
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.
Qin, Yuan; Michalowski, Andreas; Weber, Rudolf; Yang, Sen; Graf, Thomas; Ni, Xiaowu
2012-11-19
Ray-tracing is the commonly used technique to calculate the absorption of light in laser deep-penetration welding or drilling. Since new lasers with high brilliance enable small capillaries with high aspect ratios, diffraction might become important. To examine the applicability of the ray-tracing method, we studied the total absorptance and the absorbed intensity of polarized beams in several capillary geometries. The ray-tracing results are compared with more sophisticated simulations based on physical optics. The comparison shows that the simple ray-tracing is applicable to calculate the total absorptance in triangular grooves and in conical capillaries but not in rectangular grooves. To calculate the distribution of the absorbed intensity ray-tracing fails due to the neglected interference, diffraction, and the effects of beam propagation in the capillaries with sub-wavelength diameter. If diffraction is avoided e.g. with beams smaller than the entrance pupil of the capillary or with very shallow capillaries, the distribution of the absorbed intensity calculated by ray-tracing corresponds to the local average of the interference pattern found by physical optics.
NASA Astrophysics Data System (ADS)
Rabahi, Amal; Hamdi, Safouane M.; Rachedi, Yahia; Hamdi, Maamar; Talhi, Oualid; Almeida Paz, Filipe A.; Silva, Artur S. M.; Fadila, Balegroune; Malika, Hamadène; Kamel, Taïbi
2014-03-01
The synthesis of 1,5-benzodiazepines by the reaction of o-phenylenediamines (o-PDAs) with dehydroacetic acid DHAA [3-acetyl-4-hydroxy-6-methyl-2H-pyran-2-one] or conjugate analogues is largely reported in the literature, but still with uncontrolled stereochemistry. In this work, a comprehensive mechanistic study on the formation of some synthesized 1,5-benzodiazepine models following different organic routes is established based on liquid-state 2D NMR, single-crystal X-ray diffraction and theoretical calculations allowing the classification of two prototropic forms A (enaminopyran-2,4-dione) and B (imino-4-hydroxypyran-2-one). Evidences are presented to show that most of the reported 1,5-benzodiazepine structures arising from DHAA and derivatives preferentially adopt the (E)-enaminopyran-2,4-diones A.
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.
NASA Astrophysics Data System (ADS)
Ohta, Kenji; Nishimura, Yasuhiro; Kitagawa, Tomomi; Hayakawa, Masashi
1997-04-01
The propagation mechanism of very low latitude (geomagnetic latitudes of less than 10-15°) whistlers is poorly understood. There is a controversy on their propagation; some workers using the observational facts have suggested field-aligned propagation, but some theoretical (ray tracing) works have all indicated nonducted propagation. This paper reexamines the propagation characteristics of nonducted propagation, but we use three-dimensional ray tracing (different from previous works) for realistic ionosphere/magnetosphere models (the electron density profile with latitudinal and longitudinal gradients and the International Geomagnetic Reference Field (IGRF) magnetic field model instead of the conventional dipole model). By assuming small possible tilts (in the latitudinal and longitudinal direction) of the initial wave normal angle in the input southern hemisphere, we have found that it is possible for us to detect simultaneously, at a very low latitude position in the northern ionosphere, one-hop whistler rays started from slightly spaced locations in the south with different initial wave normal angles and that some of them can penetrate through the ionosphere, but some others cannot. On the basis of systematic analysis of important parameters, we come to the general conclusion that it is possible for us to find a closely spaced set of paths to reproduce the one-hop and three-hop whistlers in the north and to have the dispersion ratio of 1:3. The echo train whistlers, as were often observed by Hayakawa et al. [1990], are realized also by this nonducted propagation without any serious requirements.
NASA Astrophysics Data System (ADS)
Wobrauschek, Peter; Streli, Christina
1997-01-01
Total reflection x-ray fluorescence analysis (TXRF) is an accepted powerful analytical tool for trace element determination in various kinds of samples. In typical applications like environmental, medical and technical sample analysis as well as for quality control during production processes, ultralow concentrations at the pg/g level, or femtogram masses, have to be determined. The combination of synchrotron radiation (SR) and multilayer monochromators together with TXRF is perfectly suited to meet the requirements. Best results can be expected from SR-TXRF though cost and accessability to SR sources limit the application. In some cases the additional inherent advantage of XRF as a nondestructive method is important. Another approach to reach such low detection limits is to increase the photon flux on the sample by means of high power x-ray tubes and multilayer focusing x-ray optics. With standard laboratory equipment the choice of appropriate anode materials for efficient excitation of specific elements and an optimal design of the energy dispersive spectrometer can also increase sensitivity. Various experimental setups used for EDXRF of the elements from B to U by K-shell excitation will be presented and discussed. The results from ultralow trace element analysis of surface impurities on Si wafers demonstrate the excellent potential of this method. With SR-TXRF the detection limits for medium Z elements can be below 20 femtogram.
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.
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.
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).
Liu, Xin
2014-01-01
This study describes a deterministic method for simulating the first-order scattering in a medical computed tomography scanner. The method was developed based on a physics model of x-ray photon interactions with matter and a ray tracing technique. The results from simulated scattering were compared to the ones from an actual scattering measurement. Two phantoms with homogeneous and heterogeneous material distributions were used in the scattering simulation and measurement. It was found that the simulated scatter profile was in agreement with the measurement result, with an average difference of 25% or less. Finally, tomographic images with artifacts caused by scatter were corrected based on the simulated scatter profiles. The image quality improved significantly.
Ray tracing survey of Z mode emissions from source regions in the high-altitude auroral zone
NASA Technical Reports Server (NTRS)
Menietti, J. D.; Lin, C. S.
1986-01-01
The ray tracing computer program described by Menietti and Lin (1985) was used to investigate the propagation of Z mode emissions from sources in the auroral zone. The calculation results indicate that the propagation is primarily perpendicular to the magnetic field line (horizontal propagation) for almost all sources considered, except when the wave source is assumed to be unrestricted by the cyclotron maser mechanism. While the propagation is initially downward, refraction rapidly increases the wave normal angle, and only propagation at near-constant altitude occurs. The frequency bandwidth estimated from the ray paths was found to be less than that observed by the DE 1 satellite. Large horizontal magnetic field gradients associated with field-aligned currents produce downward propagation but are still not sufficient to produce the observed bandwidths. The results suggest that wave growth may be due to mechanisms in addition to cyclotron maser resonance.
Ray tracing of Z-mode emissions from source regions in the high-altitude auroral zone
NASA Technical Reports Server (NTRS)
Menietti, J. D.; Lin, C. S.
1985-01-01
Two-dimensional ray tracing of Z-mode radiation from sources in the auroral zone has been performed. The Z-mode waves are assumed to be excited by the cyclotron maser mechanism at frequencies near the electron gyrofrequency and at wave normal angles near 90 deg. The emission is found to propagate primarily perpendicular to the magnetic field line (horizontal propagation) for all sources considered, and thus not to substantially lower altitudes. The frequency bandwidth estimated from the ray paths is much less than that observed by DE-1. It is suggested that the wave source needs to be in the region of field-aligned current in order for the cyclotron maser mechanism to explain the broad frequency bandwidth of Z-mode emissions.
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.
NASA Astrophysics Data System (ADS)
Kalisch, S.; Trinh, T.; Chun, H.; Ern, M.; Preusse, P.; Kim, Y.; Eckermann, S. D.; Riese, M.
2013-12-01
Gravity waves (GW) are responsible for driving large scale circulations like Brewer-Dobson circulation, contribute to the wave driving of the QBO in the tropics, and are also known as a coupling mechanism between tropospheric sources and the upper stratosphere to mesosphere region. Convection is a dominant source for tropical GWs, but also one of the most difficult and dynamic GW sources to understand. Therefore, we present the results of GW ray-tracing calculations from tropospheric (convective) sources up to the mesosphere. We used the Gravity wave Regional Or Global RAy-Tracer (GROGRAT) to perform the GW trajectory calculations and the convective GW source scheme from Yonsei University (South Korea) to quantify the excitation by convection. Heating rates, cloud data, and atmospheric background data were provided by the MERRA dataset for the calculation of convective forcing by deep convection and for the atmospheric background of the ray-tracing calculations afterwards. In order to validate our findings we compare our simulation results with satellite measurements of temperature amplitudes and momentum flux from the SABER instrument over a 10 years period. Simulation and measurements are in good agreement for the tropics throughout the whole simulated period and show similar seasonal behavior. Additionally, the observational filter of the instrument was taken into account and its influences are discussed. The modulation of GW momentum flux by the background winds and in particular the influence of the QBO is investigated. GW drag at various altitudes is calculated and compared to the drag required for the forcing of the QBO. Further, we show the results of a non-orographic background parameterization used as start conditions for the ray-tracer to emphasize the improvements of our coupled convective GW source model over non-orographic GW parameterizations.
Ma, Junjie; Wang, Yeyao; Yang, Qi; Liu, Yubing; Shi, Ping
2015-05-06
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.
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
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
NASA Technical Reports Server (NTRS)
Menietti, J. D.; Green, J. L.; Gulkis, S.; Six, N. F.
1984-01-01
Three-dimensional ray tracing is applied to an analysis of variable radio wave normal angle effects on the associated decametric (DAM) arc structures in the Jovian magnetosphere. The analysis is bed on 1-40 MHz radio signature recorded during Voyage 1 and 2 passages. The frequencies considered are above the R-X cut-off, and several ratios of the emission frequency/source frequency. The ray tracing code is based on a cold plasma formula and integration of the Hasselgrove (1955) equations. It is assumed that the emission is in the R-X mode, the source lies at the foot of an Io flux tube, and the emission cone is hollow. Attention is focused on data for two intense, vertex-late, high curvature DAM arc. A possible source for the arcs is found to be doppler-shifted gyroemission from a beam of electrons with an energy of 10 keV. A value of 1.1 is set as the limit of the doppler shift of the DAM emissions.
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.
A hybrid tool for spectral ray tracing simulations of luminescent cascade systems.
Leyre, Sven; Ryckaert, Jana; Acuña, Paula; Audenaert, Jan; Meuret, Youri; Durinck, Guy; Hofkens, Johan; Deconinck, Geert; Hanselaer, Peter
2014-10-01
To perform adequate simulations of luminescent cascade systems, a hybrid method combining a commercial ray tracer and a programming tool is presented. True Monte Carlo algorithms for luminescent materials, treating each ray individually, are adapted to allow wavelength conversion of ray sets. Two solutions for the wavelength conversion of ray sets are discussed: a random approach, where absorption events are randomly selected to create emission events, and a combined approach, where information from multiple absorption events is combined to create emission events. Both methods are applied to simulate the performance of a virtual remote phosphor light-emitting diode module. When using the combined approach, the required computation time to achieve sufficient accuracy is a factor 2 lower, compared to the time required when applying the random approach.
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.
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
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.
Sarmah, Nabin; Richards, Bryce S; Mallick, Tapas K
2011-07-01
We present a detailed design concept and optical performance evaluation of stationary dielectric asymmetric compound parabolic concentrators (DiACPCs) using ray-tracing methods. Three DiACPC designs, DiACPC-55, DiACPC-66, and DiACPC-77, of acceptance half-angles (0° and 55°), (0° and 66°), and (0° and 77°), respectively, are designed in order to optimize the concentrator for building façade photovoltaic applications in northern latitudes (>55 °N). The dielectric concentrator profiles have been realized via truncation of the complete compound parabolic concentrator profiles to achieve a geometric concentration ratio of 2.82. Ray-tracing simulation results show that all rays entering the designed concentrators within the acceptance half-angle range can be collected without escaping from the parabolic sides and aperture. The maximum optical efficiency of the designed concentrators is found to be 83%, which tends to decrease with the increase in incidence angle. The intensity is found to be distributed at the receiver (solar cell) area in an inhomogeneous pattern for a wide range of incident angles of direct solar irradiance with high-intensity peaks at certain points of the receiver. However, peaks become more intense for the irradiation incident close to the extreme acceptance angles, shifting the peaks to the edge of the receiver. Energy flux distribution at the receiver for diffuse radiation is found to be homogeneous within ±12% with an average intensity of 520 W/m².
TRACING THE REVERBERATION LAG IN THE HARD STATE OF BLACK HOLE X-RAY BINARIES
De Marco, B.; Ponti, G.; Nandra, K.; Muñoz-Darias, T.
2015-11-20
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.
NASA Astrophysics Data System (ADS)
Custo, Graciela; Litter, Marta I.; Rodríguez, Diana; Vázquez, Cristina
2006-11-01
It is well known that Hg species cause high noxious effects on the health of living organisms even at very low levels (5 μg/L). Quantification of this element is an analytical challenge due to the peculiar physicochemical properties of all Hg species. The regulation of the maximal allowable Hg concentration led to search for sensitive methods for its determination. Total reflection X-ray fluorescence is a proved instrumental analytical tool for the determination of trace elements. In this work, the use of total reflection X-ray fluorescence for Hg quantification is investigated. However, experimental determination by total reflection X-ray fluorescence requires depositing a small volume of sample on the reflector and evaporation of the solvent until dryness to form a thin film. Because of volatilization of several Hg forms, a procedure to capture these volatile species in liquid samples by using complexing agents is proposed. Acetate, oxalic acid, ethylenediaminetetracetic acid and ammonium pyrrolidine-dithiocarbamate were assayed for trapping the analytes into the solution during the preparation of the sample and onto the reflector during total reflection X-ray fluorescence measurements. The proposed method was applied to evaluate Hg concentration during TiO 2-heterogeneous photocatalysis, one of the most known advanced oxidation technologies. Advanced oxidation technologies are processes for the treatment of effluents in waters and air that involve the generation of very active oxidative and reductive species. In heterogeneous photocatalysis, Hg is transformed to several species under ultraviolet illumination in the presence of titanium dioxide. Total reflection X-ray fluorescence was demonstrated to be applicable in following the extent of the heterogeneous photocatalysis reaction by determining non-transformed Hg in the remaining solution.
NASA Astrophysics Data System (ADS)
Seong, Sehyun; Kim, Sug-Whan; Kim, Sangmin; Ryu, Dongok; Kang, Ho Gyun
2014-10-01
We present the apparent optical performance variation of an infrared sensor caused by laminar flow field surrounding a highly supersonic projectile with cone shape head. An optical ray tracing model was constructed and numerical simulations of the aero-optical effects were performed by computational fluid dynamics (CFD) analysis and isodensity surface based ray tracing computation. To maximize modeling and computation efficiency, the number of sampling isodensity layers was reduced to less than 5 for improved discretization of the inhomogeneous gradient index (GRIN) media. Using this method, the simulation results show that the BSE is smaller than about 2.8 arcsec when the projectile flies at 25, 35, 50 km in altitude, Mach 4, 6 in speed, and 0°, 10° in angle of attack. The technical details and implications of the optical ray tracing model are presented together with the simulation results.
Meirer, F.; Streli, C.; Wobrauschek, P.; Zoeger, N.; Pepponi, G.
2009-04-01
In the presented study the grazing exit x-ray fluorescence was tested for its applicability to x-ray absorption near edge structure analysis of arsenic in droplet samples. The experimental results have been compared to the findings of former analyses of the same samples using a grazing incidence (GI) setup to compare the performance of both geometries. Furthermore, the investigations were accomplished to gain a better understanding of the so called self-absorption effect, which was observed and investigated in previous studies using a GI geometry. It was suggested that a normal incidence-grazing-exit geometry would not suffer from self-absorption effects in x-ray absorption fine structure (XAFS) analysis due to the minimized path length of the incident beam through the sample. The results proved this assumption and in turn confirmed the occurrence of the self-absorption effect for GI geometry. Due to its lower sensitivity it is difficult to apply the GE geometry to XAFS analysis of trace amounts (few nanograms) of samples but the technique is well suited for the analysis of small amounts of concentrated samples.
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.
NASA Astrophysics Data System (ADS)
Kump, P.; Nečemer, M.; Šnajder, J.
1996-04-01
Multielemental determinations in samples of various types of bee honey, pollen and bee tissue have been carried out using total reflection X-ray fluorescence spectrometry (TXRF) and radioisotope excited X-ray fluorescence spectrometry (XRF). The objective was to establish whether the elemental content of bee honey, in particular, correlates with any useful information about the environment, variety of honey, etc. An attempt has also been made to determine the X-ray techniques' ability to compete with atomic absorption spectrometry (AAS) and inductively coupled plasma-atomic emission spectrometry (ICP-AES), with regard to elemental sensitivity, accuracy, sample preparation procedures, and in particular, economic performance, which is very important in selecting an appropriate technique for the analysis of large numbers of samples. The results confirm the advantages of the TXRF method for trace element analysis, but only when utilising monochromatic excitation and selecting a proper sample preparation procedure. The radioisotope XRF technique, which does not require any sample preparation, is still very competitive in analysis of elements with concentrations above a few ten ppm. Preliminary results also confirm some correlations between the elemental content of honey and the status of the environment, and encourage further work in this direction
Graphical aids for the users of GEMACS (GAUGE): Ray tracing enhancements
NASA Astrophysics Data System (ADS)
Evans, Jeffrey A.; Coffey, Edgar L.
1994-09-01
This report contains update pages for RADC-TR-88-316, same title. The capability to plot rays from source points to observation points via multiple scattering centers has been added to the original suite of operations available in the original GAUGE package. This is useful for antenna design and system integration studies.
NASA Astrophysics Data System (ADS)
Wang, Jin; Ma, Jianyong; Zhou, Changhe
2014-11-01
A 3×3 high divergent 2D-grating with period of 3.842μm at wavelength of 850nm under normal incidence is designed and fabricated in this paper. This high divergent 2D-grating is designed by the vector theory. The Rigorous Coupled Wave Analysis (RCWA) in association with the simulated annealing (SA) is adopted to calculate and optimize this 2D-grating.The properties of this grating are also investigated by the RCWA. The diffraction angles are more than 10 degrees in the whole wavelength band, which are bigger than the traditional 2D-grating. In addition, the small period of grating increases the difficulties of fabrication. So we fabricate the 2D-gratings by direct laser writing (DLW) instead of traditional manufacturing method. Then the method of ICP etching is used to obtain the high divergent 2D-grating.
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.
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.
NASA Astrophysics Data System (ADS)
Mohammad-Pour, Hooman; Kanapathipillai, Sangarapillai; Manns, Fabrice; Ho, Arthur
2015-03-01
A key step in the design of an accommodating gel to replace the natural contents of the presbyopic human crystalline lens is to find the equivalent homogeneous mechanical and material properties of the gel that yield comparable optical response as the lens with gradient properties. This process is compounded by the interplay between the mechanical and optical gradient. In order to find uniform properties of the lens both gradients need to be considered. In this paper, numerical ray-tracing and finite element method (FEM) are implemented to investigate the effects of varying the uniform elasticity and refractive index on the accommodative amplitude. Our results show that the accommodative amplitude be expressed as a function of gel refractive index and Young's modulus of elasticity. In other words infinite sets of elasticity and refractive index exist that yield a certain amount of accommodation.
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.
A model of the AGS based on stepwise ray-tracing through the measured field maps of the main magnets
Dutheil Y.; Meot, F.; Tsoupas, N.
2012-05-20
Two-dimensional mid-plane magnetic field maps of two of the main AGS magnets were produced, from Hall probe measurements, for a series of different current settings. The analysis of these data yielded the excitation functions [1] and the harmonic coefficients [2] of the main magnets which have been used so far in all the models of the AGS. The constant increase of the computation power makes it possible today to directly use a stepwise raytracing through these measured field maps with a reasonable computation time. We describe in detail how these field maps have allowed the generation of models of the 6 different types of AGS main magnets, and how they are being handled with the Zgoubi ray-tracing code [3]. We give and discuss a number of results obtained regarding both beam and spin dynamics in the AGS, and we provide comparisons with other numerical and analytical modelling methods.
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.
Use of Rayleigh imaging and ray tracing to correct for beam-steering effects in turbulent flames.
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
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
NASA Astrophysics Data System (ADS)
Wang, G.; Doyle, E. J.; Peebles, W. A.
2016-11-01
A monostatic antenna array arrangement has been designed for the microwave front-end of the ITER low-field-side reflectometer (LFSR) system. This paper presents details of the antenna coupling coefficient analyses performed using GENRAY, a 3-D ray tracing code, to evaluate the plasma height accommodation capability of such an antenna array design. Utilizing modeled data for the plasma equilibrium and profiles for the ITER baseline and half-field scenarios, a design study was performed for measurement locations varying from the plasma edge to inside the top of the pedestal. A front-end antenna configuration is recommended for the ITER LFSR system based on the results of this coupling analysis.
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.
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.
NASA Astrophysics Data System (ADS)
Dyl, Kathryn A.; Cleverley, James S.; Bland, Phil A.; Ryan, Chris G.; Fisher, Louise A.; Hough, Robert M.
2014-06-01
We present the application of a new synchrotron-based technique for rapid mapping of trace element distributions across large areas of the CV3 meteorites Allende and Vigarano. This technique utilizes the Australian Synchrotron X-ray Fluorescence Microscopy (XFM) beam line with its custom designed and built X-ray detector array called Maia. XFM with Maia allows data to be collected using a 2 μm spot size at very low dwell times (∼0.1-0.5 ms), resulting in maps of entire thin sections in ∼5 h. Maia is an energy dispersive detector system with a large collection solid-angle, which allows full spectral acquisition and high sensitivity. Hence, there is no need to constrain the elements of interest a priori. We collected whole section maps (∼2 cm × 1 cm) from 3 thick sections of Allende and a single map (2 cm × 1.5 cm) from a thick section of Vigarano. Our experimental conditions provide data for elements with 20 ⩽ Z ⩽ 40 (K-shell, Ca through Zr) and the L-emissions of Os, Ir, Pt, Au, and Pb. We illustrate the unique capabilities of this technique by presenting observations across myriad length scales, from the centimeter-scale down to the detection of sub-micrometer particles within these objects. Our initial results show the potential of this technique to help decipher spatial and textural variations in trace element chemistry between CAIs, chondrules, matrix, and other chondritic components. We also illustrate how these datasets can be applied to understanding both nebular and parent-body processes within meteorites.
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.
Spatially Resolved Synthetic Spectra from 2D Simulations of Stainless Steel Wire Array Implosions
Clark, R. W.; Giuliani, J. L.; Thornhill, J. W.; Chong, Y. K.; Dasgupta, A.; Davis, J.
2009-01-21
A 2D radiation MHD model has been developed to investigate stainless steel wire array implosion experiments on the Z and refurbished Z machines. This model incorporates within the Mach2 MHD code a self-consistent calculation of the non-LTE kinetics and ray trace based radiation transport. Such a method is necessary in order to account for opacity effects in conjunction with ionization kinetics of K-shell emitting plasmas. Here the model is used to investigate multi-dimensional effects of stainless steel wire implosions. In particular, we are developing techniques to produce non-LTE, axially and/or radially resolved synthetic spectra based upon snapshots of our 2D simulations. Comparisons between experimental spectra and these synthetic spectra will allow us to better determine the state of the experimental pinches.
Ray tracing and absorption of electron cyclotron waves in the L-2 stellarator
Goldfinger, R.C. ); Likin, K.M. . Inst. Obshchey Fiziki); Ochirov, B.D. . Inst. Avtomatiki i Ehlektrometrii)
1991-01-01
The absorption of electron cyclotron waves in L-2 stellarator plasmas has been investigated by adapting the RAYS geometrical optics code developed at Oak Ridge National Laboratory to the parameters of L-2. Two heating schemes were considered: Low-field launching of the ordinary wave at the fundamental resonance and low-field launching of the extraordinary wave at the second harmonic. Significant power absorption (up to 100%) of the extraordinary mode at the second harmonic resonance was obtained. A multipass absorption model was used to estimate the contribution to plasma heating of the power that remains after the first pass which is subsequently reflected from the vessel walls. Finally, results obtained with the RAYS code and with a code developed at the Institute of Automation and Electrometry were compared and found to be in good agreement. 6 refs., 4 figs.
Laser ray tracing and power deposition on an unstructured three-dimensional grid
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
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.
Ray tracing to study of waxes around the cloud point by optical absorption tomography
NASA Astrophysics Data System (ADS)
Moreno-Alvarez, L.; Meneses-Fabian, C.; Herrera, J. N.; Rodríguez-Zurita, G.
2011-10-01
In optical tomography of parallel projections, the light rays that cross the slice of the object are experimentally approached to suffer minimal refraction, i.e. take refractional limits. Generally, a media is used for immersion whose refractive index rate tied the environment to study, but the geometry of the containment vessels also affects refraction and may be the case that the approach is not subject performed. In this work we make a numerical study of the refraction of a ray of light that enters a typical experimental system for studying the thermodynamic behaviour of a paraffinic wax around their cloud point. Since it has special properties in the heat capacity and refractive index near the phase transition, these results will be used to characterize the transition and is intended to give tomographic information to the study of thermal properties obtained using the T-History calorimetric technique. In this study, we simulate the behaviour of the refraction of parallel rays crossing the T-History test system to find the optimal values of the dimensions of the containment vessels and the index of refraction of the medium for immersion, considering that the optical properties of the sample under study vary with temperature. Thus, we obtain the optimum conditions of minimum refraction technique for which reconstruction of a tomographic slice parallel projection can be applied. The distribution of the linear attenuation coefficient on the slice of the object, typically, is obtained by applying the filtered backprojection algorithm to the set of projections (sinogram) obtained experimentally, which constitutes a way to detect mobile interfacial boundaries in real time. The projections are sequentially measuring the intensity of the wave emerging from the slice of the object at different angles.
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.
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.
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.
NASA Astrophysics Data System (ADS)
Xie, Q.; Peng, L.; Cai, F.; Li, Ai G.; Yang, K.
2013-07-01
We have assessed the relative content and distribution of Iron and Zinc elements using microbeam synchrotron radiation X-ray fluorescence technique. One such technique is X-ray fluorescence (XRF), which has been used previously to map trace elements distribution in Physical samples. In this article a compromise is suggested in issue Pterygium samples. In this study, a prospective randomized clinical trial was conducted. Serial frozen sections of pterygium tissues and conjunctival tissues of 40 μm thickness were collected from 8 patients £¨10 eyes£©undergoing pterygium excision combine with limbal stem cell transplantation. A synchrotron-based XRF microprobe was used to map the distribution of Fe and Zn in whole frozen pterygium sections. The frozen sections were tested by synchrotron radiation X-ray fluorescence technique. These experiments were performed at BL15U in Shanghai, China. Then, the results have palyed that Iron and Zinc were present in both pterygium tissues and normal conjunctiva tissues (relevance ratio 100%). The contents of Iron and Zinc in normal conjunctiva tissues were significantly lower than in pterygium tissues (P < 0.05). The microelements were mostly clusteredin the pterygium tissues, while sparsely distributed in the normal conjunctiva tissue. Finally, we found that XRF imaging will be useful for mapping elemental distribution in Pterygium tissues. 40 μm frozen section on 6 μm mylar film is good for the test on BL15U. The contents of Iron and Zinc in pterygium tissue were significantly higher than in the control tissues. The results seem to be valuable in that Iron and Zinc may play a role in the development process of Pterygium.
Baiz, Carlos R.; Schach, Denise; Tokmakoff, Andrei
2014-01-01
We describe a microscope for measuring two-dimensional infrared (2D IR) spectra of heterogeneous samples with μm-scale spatial resolution, sub-picosecond time resolution, and the molecular structure information of 2D IR, enabling the measurement of vibrational dynamics through correlations in frequency, time, and space. The setup is based on a fully collinear “one beam” geometry in which all pulses propagate along the same optics. Polarization, chopping, and phase cycling are used to isolate the 2D IR signals of interest. In addition, we demonstrate the use of vibrational lifetime as a contrast agent for imaging microscopic variations in molecular environments. PMID:25089490
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.
Shape estimation of transparent objects by using inverse polarization ray tracing.
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
2004-08-01
AnisWave2D is a 2D finite-difference code for a simulating seismic wave propagation in fully anisotropic materials. The code is implemented to run in parallel over multiple processors and is fully portable. A mesh refinement algorithm has been utilized to allow the grid-spacing to be tailored to the velocity model, avoiding the over-sampling of high-velocity materials that usually occurs in fixed-grid schemes.
Wang, Xiao-Huan; Meng, Qing-Fen; Dong, Ya-Ping; Chen, Mei-Da; Li, Wu
2010-03-01
A rapid multi-element analysis method for clay mineral samples was described. This method utilized a polarized wave-length dispersive X-ray fluorescence spectrometer--Axios PW4400, which had a maximum tube power of 4 000 watts. The method was developed for the determination of As, Mn, Co, Cu, Cr, Dy, Ga, Mo, P, Pb, Rb, S, Sr, Ni, ,Cs, Ta, Th, Ti, U, V, Y, Zn, Zr, MgO, K2O, Na2O, CaO, Fe2O3, Al2O3, SiO2 and so on. Thirty elements in clay mineral species were measured by X-ray fluorescence spectrometry with pressed powder pellets. Spectral interferences, in particular the indirect interferences of each element, were studied. A method to distinguish the interference between each other periodic elements in element periodic table was put forward. The measuring conditions and existence were mainly investigated, and the selected background position as well as corrected spectral overlap for the trace elements were also discussed. It was found that the indirect spectral overlap line was the same important as direct spectral overlap line. Due to inducing the effect of indirect spectral overlap, some elements jlike Bi, Sn, W which do not need analysis were also added to the elements channel. The relative standard deviation (RSD) was in the range of 0.01% to 5.45% except three elements Mo, Cs and Ta. The detection limits, precisions and accuracies for most elements using this method can meet the requirements of sample analysis in clay mineral species.
NASA Astrophysics Data System (ADS)
Aird, James; Coil, Alison; Georgakakis, Antonis; Nandra, Kirpal
2016-08-01
X-ray selection provides a powerful method of identifying AGN across a variety of host galaxies and with a wide range of accretion rates. However, careful consideration of the underlying selection biases are vital to reveal the true underlying distribution of accretion rates and determine how the incidence of AGN is related to the properties of the galaxies that host them. I will present new measurements of the distribution of specific accretion rates (scaled relative to the total host galaxy mass, roughly tracing the Eddington ratio) within both star-forming and quiescent galaxy populations. We combine near-infrared selected samples of galaxies from the CANDELS/3D-HST and UltraVISTA surveys with deep Chandra X-ray data and use an advanced Bayesian technique to constrain the underlying distribution of specific accretion rates as a function of stellar mass and redshift. Our results reveal a broad distribution of accretion rates (reflecting long-term variability in the level of AGN fuelling) in both galaxy types. The probability of a star-forming galaxy hosting an AGN (above a fixed specific accretion rate) has a strong stellar mass dependence - revealing an intrinsically higher incidence of AGN in massive star-forming galaxies - and undergoes a stellar-mass-dependent evolution with redshift. The probability of a quiescent galaxy hosting an AGN is generally lower but does not depend on stellar mass and evolves differently with redshift. These results provide vital insights into the relationship between the growth of black hole and the physical properties of their host galaxies.
Saghatforoush, Lotfali Bakhtiari, Akbar; Gheleji, Hojjat
2015-01-15
The synthesis of two dimensional (2D) coordination polymer [Pb{sub 2}(µ-I){sub 2}(µ-dpp-N,N,N,N)(µ-dpp-N,N)I{sub 2}]{sub n} (dpp=2,3-bis(2-pyridyl)pyrazine) is reported. As determined by X-ray diffraction of a twinned crystal, the dpp ligand simultaneously adopts a bis–bidentate and bis–monodentate coordination mode in the crystal structure of compound. The electronic band structure along with density of states (DOS) calculated by the DFT method indicates that the compound is an indirect band gap semiconductor. According to the DFT calculations, the observed emission of the compound at 600 nm in solid phase could be attributed to arise from an excited LLCT state (dpp-π{sup ⁎} [C-2p and N-2p states, CBs] to I-6p state [VBs]). The linear optical properties of the compound are also calculated by DFT method. The structure of the compound in solution phase is discussed based on the measured {sup 1}H NMR and fluorescence spectra in DMSO. TGA studies indicate that the compound is thermally stable up to 210 °C. - Graphical abstract: The synthesis, crystal structure and emission spectra of [Pb{sub 2}(µ-I){sub 2}(µ-dpp-N,N,N,N)(µ-dpp-N,N)I{sub 2}]{sub n} is presented. The electronic band structure and linear optical properties of the compound are calculated by the DFT method. - Highlights: • Two dimensional [Pb{sub 2}(µ-I){sub 2}(µ-dpp-N,N,N,N)(µ-dpp-N,N)I{sub 2}]{sub n} has been prepared. • The structure of the compound is determined by XRD of a twinned crystal. • DFT calculations indicate that the compound is an indirect band gap semiconductor. • As shown by DFT calculations, the emission band of the compound is LLCT. • Solution phase structure of compound is explored by {sup 1}H NMR and emission spectra.
Rethfeldt, Ch.; Fuchs, H.; Gardey, K.-U.
2006-03-15
For the case of eye tumor therapy with protons, improvements are introduced compared to the standard dose calculation which implies straight-line optics and the constant-density assumption for the eye and its surrounding. The progress consists of (i) taking account of the lateral scattering of the protons in tissue by folding the entrance fluence distribution with the pencil beam distribution widening with growing depth in the tissue, (ii) rescaling the spread-out Bragg peak dose distribution in water with the radiological path length calculated voxel by voxel on ray traces through a realistic density matrix for the treatment geometry, yielding a trajectory dependence of the geometrical range. Distributions calculated for some specific situations are compared to measurements and/or standard calculations, and differences to the latter are discussed with respect to the requirements of therapy planning. The most pronounced changes appear for wedges placed in front of the eye, causing additional widening of the lateral falloff. The more accurate prediction of the dose dependence at the field borders is of interest with respect to side effects in the risk organs of the eye.
Sassen, K; Knight, N C; Takano, Y; Heymsfield, A J
1994-07-20
During the 1986 Project FIRE (First International Satellite Cloud Climatology Project Regional Experiment) field campaign, four 22° halo-producing cirrus clouds were studied jointly from a groundbased 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.
Cruty, M R; Benton, E V; Turnbill, C E; Philpott, D E
1975-04-01
Five pocket mice (Perognathus longimembris) were flown on Apollo XVII, each with a solid-state (plastic) nuclear track detector implanted beneath its scalp. The subscalp detectors were sensitive to HZE cosmic ray particles with a LET larger than or equal to 0.15 million electron volts per micrometer (MeV/mjm). A critical aspect of the dosimetry of the experiment involved tracing individual particle trajectories through each mouse head from particle tracks registered in the individual subscalp detectors, thereby establishing a one-to-one correspondence between a trajectory location in the tissue and the presence or absence of a lesion. The other major aspect was the identification of each registered particle. An average of 16 particles with Z larger than or equal to 6 and 2.2 particles with Z larger than or equal to 20 were found per detector. The track density, 29 tracks/cm2, when adjusted for detection volume, was in agreement with the photographic emulsion data from an area dosimeter located next to the flight package.
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.
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.
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).
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.
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.
Bauboeck, Michi; Psaltis, Dimitrios; Oezel, Feryal; Johannsen, Tim E-mail: dpsaltis@email.arizona.edu E-mail: timj@email.arizona.edu
2012-07-10
A moderately spinning neutron star acquires an oblate shape and a spacetime with a significant quadrupole moment. These two properties affect its apparent surface area for an observer at infinity, as well as the light curve arising from a hot spot on its surface. In this paper, we develop a ray-tracing algorithm to calculate the apparent surface areas of moderately spinning neutron stars making use of the Hartle-Thorne metric. This analytic metric allows us to calculate various observables of the neutron star in a way that depends only on its macroscopic properties and not on the details of its equation of state. We use this algorithm to calculate the changes in the apparent surface area, which could play a role in measurements of neutron-star radii and, therefore, in constraining their equation of state. We show that whether a spinning neutron star appears larger or smaller than its non-rotating counterpart depends primarily on its equatorial radius. For neutron stars with radii {approx}10 km, the corrections to the Schwarzschild spacetime cause the apparent surface area to increase with spin frequency. In contrast, for neutron stars with radii {approx}15 km, the oblateness of the star dominates the spacetime corrections and causes the apparent surface area to decrease with increasing spin frequency. In all cases, the change in the apparent geometric surface area for the range of observed spin frequencies is {approx}<5% and hence only a small source of error in the measurement of neutron-star radii.
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.
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.
A ray-tracing model to account for off-great circle HF propagation over northerly paths
NASA Astrophysics Data System (ADS)
Zaalov, N. Y.; Warrington, E. M.; Stocker, A. J.
2005-08-01
Off-great circle HF propagation effects are a common feature of the northerly ionosphere (i.e., the subauroral trough region, the auroral zone, and the polar cap). In addition to their importance in radiolocation applications where deviations from the great circle path may result in significant triangulation errors, they are also important in two other respects: (1) In systems employing directional antennas pointed along the great circle path, the signal quality may be degraded at times when propagation is via off-great circle propagation modes; and (2) the off-great circle propagation mechanisms may result in propagation at times when the signal frequency exceeds the maximum usable frequency along the great circle path. A ray-tracing model covering the northerly ionosphere is described in this paper. The results obtained using the model are very reminiscent of the directional characteristics observed in various experimental measurement programs, and consequently, it is believed that the model may be employed to enable the nature of off-great circle propagation effects to be estimated for paths which were not subject to experimental investigation. Although it is not possible to predict individual off-great circle propagation events, it is possible to predict the periods during which large deviations are likely to occur and their magnitudes and directions.
Leiner, Claude; Nemitz, Wolfgang; Schweitzer, Susanne; Wenzl, Franz P; Hartmann, Paul; Hohenester, Ulrich; Sommer, Christian
2014-06-30
In this study the applicability of an interface procedure for combined ray-tracing and finite difference time domain (FDTD) simulations of optical systems which contain two diffractive gratings is discussed. The simulation of suchlike systems requires multiple FDTD↔RT steps. In order to minimize the error due to the loss of the phase information in an FDTD→RT step, we derive an equation for a maximal coherence correlation function (MCCF) which describes the maximum degree of impact of phase effects between these two different diffraction gratings and which depends on: the spatial distance between the gratings, the degree of spatial coherence of the light source and the diffraction angle of the first grating for the wavelength of light used. This MCCF builds an envelope of the oscillations caused by the distance dependent coupling effects between the two diffractive optical elements. Furthermore, by comparing the far field projections of pure FDTD simulations with the results of an RT→FDTD→RT→FDTD→RT interface procedure simulation we show that this function strongly correlates with the error caused by the interface procedure.
Hou, Xiandeng; Peters, Heather L; Yang, Zheng; Wagner, Karl A; Batchelor, James D; Daniel, Meredith M; Jones, Bradley T
2003-03-01
A convenient method is described for monitoring Cd, Ni, Cu, and Pb at trace levels in drinking water samples. These metals are preconcentrated on a chelating solid-phase extraction disk and then determined by X-ray fluorescence spectrometry. The method tolerates a wide pH range (pH 6-14) and a large amount of alkaline and alkaline earth elements. The preconcentration factor is well over 1600, assuming a 1 L water sample volume. The limits of detection for Cd, Ni, Cu, and Pb are 3.8, 0.6, 0.4, and 0.3 ng/mL, respectively. These are well below the federal maximum contaminant level values, which are 5, 100, 1300, and 15 ng/mL, respectively. The proposed method has many advantages including ease of operation, multielement capability, nondestructiveness, high sensitivity, and relative cost efficiency. The solid-phase extraction step can be conducted in the field and then the disks can be mailed to a laboratory for the analysis, eliminating the cost of transporting large volumes of water samples. Furthermore, the color of the used extraction disk provides an initial estimate of the degree of contamination for some transition metals (for example, Ni and Cu). Thus, the overall cost for analysis of metals in drinking water can be minimized by implementing the method, and small water supply companies with limited budgets will be better able to comply with the Safe Drinking Water Act. PMID:14658627
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.
Pelzers, R S; Yu, Q L; Mangkuto, R A
2014-10-01
This article aims to understand the radiation behavior within a photo-reactor, following the ISO 22197-1:2007 standard. The RADIANCE lighting simulation tool, based on the backward ray-tracing modeling method, is employed for a numerical computation of the radiation field. The reflection of the glass cover in the photo-reactor and the test sample influence the amount of irradiance received by the test-sample surface in the photo-reactor setup. The reflection of a white sample limits the irradiance reduction by the glass cover to 1.4 %, but darker samples can lead to an overestimation up to 9.8 % when used in the same setup. This overestimation could introduce considerable error into the interpretation of experiments. Furthermore, this method demonstrates that the kinetics for indoor photocatalytic pollutant degradation can be refined through radiation modeling of the reactor setup. In addition, RADIANCE may aid in future modeling of the more complex indoor environment where radiation affects significantly photocatalytic activity.
NASA Astrophysics Data System (ADS)
Abraham, J. A.; Grenón, M. S.; Sánchez, H. J.; Valentinuzzi, M. C.; Perez, C. A.
2007-07-01
Hard dental tissues like dentine and cementum with calcified deposits (dental calculi) were studied in several human dental pieces of adult individuals from the same geographic region. A couple of cross cuts were performed at dental root level resulting in a planar slice with calculus and dental tissue exposed for analysis. The elemental content along a linear path crossing the dentine-cementum-tartar interfaces and also all over a surface was measured by X-ray fluorescence microanalysis using synchrotron radiation (μSRXRF). The concentration of elemental traces like K, V, Cu, Zn, As, Br and Sr showed different features on the analyzed regions. The possible connections with the dynamic of mineralization and biological implications are discussed. The concentrations of major elements Ca and P were also determined and the measured Ca/P molar ratio was used to estimate the average composition of calcium phosphate phases in the measured points. A deeper knowledge of the variations of the elemental compositions and the changes of the different phases will help to a better understanding of the scarcely known mechanism of calculus growing.
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
NASA Astrophysics Data System (ADS)
Baba, Y.; Shimoyama, I.; Hirao, N.
2016-10-01
In order to determine the chemical states of radioactive cesium (137Cs or 134Cs) sorbed in clay minerals, chemical states of cesium as well as the other alkali metals (sodium and rubidium) sorbed in micaceous oxides have been investigated by X-ray photoelectron spectroscopy (XPS). Since the number of atoms in radioactive cesium is extremely small, we specially focused on chemical states of trace-level alkali metals. For this purpose, we have measured XPS under X-ray total reflection (TR) condition. For cesium, it was shown that ultra-trace amount of cesium down to about 100 pg cm-2 can be detected by TR-XPS. This amount corresponds to about 200 Bq of 137Cs (t1/2 = 30.2 y). It was demonstrated that ultra-trace amount of cesium corresponding to radioactive cesium level can be measured by TR-XPS. As to the chemical states, it was found that core-level binding energy in TR-XPS for trace-level cesium shifted to lower-energy side compared with that for thicker layer. A reverse tendency is observed in sodium. Based on charge transfer within a simple point-charge model, it is concluded that chemical bond between alkali metal and micaceous oxide for ultra-thin layer is more polarized that for thick layer.
DYNA2D96. Explicit 2-D Hydrodynamic FEM Program
Whirley, R.G.
1992-04-01
DYNA2D is a vectorized, explicit, two-dimensional, axisymmetric and plane strain finite element program for analyzing the large deformation dynamic and hydrodynamic response of inelastic solids. DYNA2D contains 13 material models and 9 equations of state (EOS) to cover a wide range of material behavior. The material models implemented in all machine versions are: elastic, orthotropic elastic, kinematic/isotropic elastic plasticity, thermoelastoplastic, soil and crushable foam, linear viscoelastic, rubber, high explosive burn, isotropic elastic-plastic, temperature-dependent elastic-plastic. The isotropic and temperature-dependent elastic-plastic models determine only the deviatoric stresses. Pressure is determined by one of 9 equations of state including linear polynomial, JWL high explosive, Sack Tuesday high explosive, Gruneisen, ratio of polynomials, linear polynomial with energy deposition, ignition and growth of reaction in HE, tabulated compaction, and tabulated.
Hutton, Laura A; O'Neil, Glen D; Read, Tania L; Ayres, Zoë J; Newton, Mark E; Macpherson, Julie V
2014-05-01
The development of a novel analytical technique, electrochemical X-ray fluorescence (EC-XRF), is described and applied to the quantitative detection of heavy metals in solution, achieving sub-ppb limits of detection (LOD). In EC-XRF, electrochemical preconcentration of a species of interest onto the target electrode is achieved here by cathodic electrodeposition. Unambiguous elemental identification and quantification of metal concentration is then made using XRF. This simple electrochemical preconcentration step improves the LOD of energy dispersive XRF by over 4 orders of magnitude (for similar sample preparation time scales). Large area free-standing boron doped diamond grown using microwave plasma chemical vapor deposition techniques is found to be ideal as the electrode material for both electrodeposition and XRF due to its wide solvent window, transparency to the XRF beam, and ability to be produced in mechanically robust freestanding thin film form. During electrodeposition it is possible to vary both the deposition potential (Edep) and deposition time (tdep). For the metals Cu(2+) and Pb(2+) the highest detection sensitivities were found for Edep = -1.75 V and tdep (=) 4000 s with LODs of 0.05 and 0.04 ppb achieved, respectively. In mixed Cu(2+)/Pb(2+) solutions, EC-XRF shows that Cu(2+) deposition is unimpeded by Pb(2+), across a broad concentration range, but this is only true for Pb(2+) when both metals are present at low concentrations (10 nM), boding well for trace level measurements. In a dual mixed metal solution, EC-XRF can also be employed to either selectively deposit the metal which has the most positive formal reduction potential, E(0), or exhaustively deplete it from solution, enabling uninhibited detection of the metal with the more negative E(0).
Causin, Valerio; Marega, Carla; Carresi, Pietro; Schiavone, Sergio; Marigo, Antonio
2007-05-01
Thirty-three shopping bags, commonly encountered in the packaging of drug doses, were characterized by wide angle X-ray diffraction (WAXD). Using this single technique, without sample preparation, nearly all the considered samples could be differentiated, achieving a discriminating power of 0.992. The rather large degree of variability existing in grocery bags, even though they are mass produced, was shown, confirming that these items can be useful in tracing the source of illicit drug doses.
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.
NASA Astrophysics Data System (ADS)
Flandes, Alberto; Spilker, Linda; Déau, Estelle
2016-10-01
Saturn's rings are a complex collection of icy particles with diameters from 1 m to few meters. Their natural window of study is the infrared because its temperatures are between 40K and 120K. The main driver of the temperature of these rings is the direct solar radiation as well as the solar radiation reflected off Saturn's atmosphere. The second most important energy source is the infrared radiation coming from Saturn itself. The study of the variations of temperatures of the rings, or, in general, their thermal behavior, may provide important information on their composition, their structure and their dynamics. Models that consider these and other energy sources are able to explain, to a first approximation, the observed temperature variations of the rings. The challenge for these models is to accurately describe the variation of illumination on the rings, i. e., how the illuminated and non-illuminated regions of the ring particles change at the different observation geometries. This shadowing mainly depends on the optical depth, as well as the general structure of the rings.In this work, We show a semi-analytical model that considers the main energy sources of the rings and their average properties (e.g., optical depth, particle size range and vertical distribution). In order to deal with the shadowing at specific geometries, the model uses the ray-tracing technique. The goal is to describe the ring temperatures observed by the Composite Infrared Spectrometer, CIRS, onboard the Cassini spacecraft, which is in orbit around Saturn since 2004. So far, the model is able to reproduce some of the general features of specific regions of the A, B and C rings.
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
Kim, Jee Hoon; Lee, Joon Woo; Ahn, Tae In; Shin, Jong Hwa; Park, Kyung Sub; Son, Jung Eek
2016-01-01
Canopy photosynthesis has typically been estimated using mathematical models that have the following assumptions: the light interception inside the canopy exponentially declines with the canopy depth, and the photosynthetic capacity is affected by light interception as a result of acclimation. However, in actual situations, light interception in the canopy is quite heterogenous depending on environmental factors such as the location, microclimate, leaf area index, and canopy architecture. It is important to apply these factors in an analysis. The objective of the current study is to estimate the canopy photosynthesis of paprika (Capsicum annuum L.) with an analysis of by simulating the intercepted irradiation of the canopy using a 3D ray-tracing and photosynthetic capacity in each layer. By inputting the structural data of an actual plant, the 3D architecture of paprika was reconstructed using graphic software (Houdini FX, FX, Canada). The light curves and A/C i curve of each layer were measured to parameterize the Farquhar, von Caemmerer, and Berry (FvCB) model. The difference in photosynthetic capacity within the canopy was observed. With the intercepted irradiation data and photosynthetic parameters of each layer, the values of an entire plant's photosynthesis rate were estimated by integrating the calculated photosynthesis rate at each layer. The estimated photosynthesis rate of an entire plant showed good agreement with the measured plant using a closed chamber for validation. From the results, this method was considered as a reliable tool to predict canopy photosynthesis using light interception, and can be extended to analyze the canopy photosynthesis in actual greenhouse conditions. PMID:27667994
Kim, Jee Hoon; Lee, Joon Woo; Ahn, Tae In; Shin, Jong Hwa; Park, Kyung Sub; Son, Jung Eek
2016-01-01
Canopy photosynthesis has typically been estimated using mathematical models that have the following assumptions: the light interception inside the canopy exponentially declines with the canopy depth, and the photosynthetic capacity is affected by light interception as a result of acclimation. However, in actual situations, light interception in the canopy is quite heterogenous depending on environmental factors such as the location, microclimate, leaf area index, and canopy architecture. It is important to apply these factors in an analysis. The objective of the current study is to estimate the canopy photosynthesis of paprika (Capsicum annuum L.) with an analysis of by simulating the intercepted irradiation of the canopy using a 3D ray-tracing and photosynthetic capacity in each layer. By inputting the structural data of an actual plant, the 3D architecture of paprika was reconstructed using graphic software (Houdini FX, FX, Canada). The light curves and A/C i curve of each layer were measured to parameterize the Farquhar, von Caemmerer, and Berry (FvCB) model. The difference in photosynthetic capacity within the canopy was observed. With the intercepted irradiation data and photosynthetic parameters of each layer, the values of an entire plant's photosynthesis rate were estimated by integrating the calculated photosynthesis rate at each layer. The estimated photosynthesis rate of an entire plant showed good agreement with the measured plant using a closed chamber for validation. From the results, this method was considered as a reliable tool to predict canopy photosynthesis using light interception, and can be extended to analyze the canopy photosynthesis in actual greenhouse conditions.
NASA Astrophysics Data System (ADS)
Marcos, Susana; Diaz-Santana, Luis; Llorente, Lourdes; Dainty, Chris
2002-06-01
Ocular aberrations were measured in 71 eyes by using two reflectometric aberrometers, employing laser ray tracing (LRT) (60 eyes) and a Shack-Hartmann wave-front sensor (S-H) (11 eyes). In both techniques a point source is imaged on the retina (through different pupil positions in the LRT or a single position in the S-H). The aberrations are estimated by measuring the deviations of the retinal spot from the reference as the pupil is sampled (in LRT) or the deviations of a wave front as it emerges from the eye by means of a lenslet array (in the S-H). In this paper we studied the effect of different polarization configurations in the aberration measurements, including linearly polarized light and circularly polarized light in the illuminating channel and sampling light in the crossed or parallel orientations. In addition, completely depolarized light in the imaging channel was obtained from retinal lipofuscin autofluorescence. The intensity distribution of the retinal spots as a function of entry (for LRT) or exit pupil (for S-H) depends on the polarization configuration. These intensity patterns show bright corners and a dark area at the pupil center for crossed polarization, an approximately Gaussian distribution for parallel polarization and a homogeneous distribution for the autofluorescence case. However, the measured aberrations are independent of the polarization states. These results indicate that the differences in retardation across the pupil imposed by corneal birefringence do not produce significant phase delays compared with those produced by aberrations, at least within the accuracy of these techniques. In addition, differences in the recorded aerial images due to changes in polarization do not affect the aberration measurements in these reflectometric aberrometers.
Kim, Jee Hoon; Lee, Joon Woo; Ahn, Tae In; Shin, Jong Hwa; Park, Kyung Sub; Son, Jung Eek
2016-01-01
Canopy photosynthesis has typically been estimated using mathematical models that have the following assumptions: the light interception inside the canopy exponentially declines with the canopy depth, and the photosynthetic capacity is affected by light interception as a result of acclimation. However, in actual situations, light interception in the canopy is quite heterogenous depending on environmental factors such as the location, microclimate, leaf area index, and canopy architecture. It is important to apply these factors in an analysis. The objective of the current study is to estimate the canopy photosynthesis of paprika (Capsicum annuum L.) with an analysis of by simulating the intercepted irradiation of the canopy using a 3D ray-tracing and photosynthetic capacity in each layer. By inputting the structural data of an actual plant, the 3D architecture of paprika was reconstructed using graphic software (Houdini FX, FX, Canada). The light curves and A/Ci curve of each layer were measured to parameterize the Farquhar, von Caemmerer, and Berry (FvCB) model. The difference in photosynthetic capacity within the canopy was observed. With the intercepted irradiation data and photosynthetic parameters of each layer, the values of an entire plant's photosynthesis rate were estimated by integrating the calculated photosynthesis rate at each layer. The estimated photosynthesis rate of an entire plant showed good agreement with the measured plant using a closed chamber for validation. From the results, this method was considered as a reliable tool to predict canopy photosynthesis using light interception, and can be extended to analyze the canopy photosynthesis in actual greenhouse conditions. PMID:27667994
Kim, Jee Hoon; Lee, Joon Woo; Ahn, Tae In; Shin, Jong Hwa; Park, Kyung Sub; Son, Jung Eek
2016-01-01
Canopy photosynthesis has typically been estimated using mathematical models that have the following assumptions: the light interception inside the canopy exponentially declines with the canopy depth, and the photosynthetic capacity is affected by light interception as a result of acclimation. However, in actual situations, light interception in the canopy is quite heterogenous depending on environmental factors such as the location, microclimate, leaf area index, and canopy architecture. It is important to apply these factors in an analysis. The objective of the current study is to estimate the canopy photosynthesis of paprika (Capsicum annuum L.) with an analysis of by simulating the intercepted irradiation of the canopy using a 3D ray-tracing and photosynthetic capacity in each layer. By inputting the structural data of an actual plant, the 3D architecture of paprika was reconstructed using graphic software (Houdini FX, FX, Canada). The light curves and A/Ci curve of each layer were measured to parameterize the Farquhar, von Caemmerer, and Berry (FvCB) model. The difference in photosynthetic capacity within the canopy was observed. With the intercepted irradiation data and photosynthetic parameters of each layer, the values of an entire plant's photosynthesis rate were estimated by integrating the calculated photosynthesis rate at each layer. The estimated photosynthesis rate of an entire plant showed good agreement with the measured plant using a closed chamber for validation. From the results, this method was considered as a reliable tool to predict canopy photosynthesis using light interception, and can be extended to analyze the canopy photosynthesis in actual greenhouse conditions.
Optical design of wavelength selective CPVT system with 3D/2D hybrid concentration
NASA Astrophysics Data System (ADS)
Ahmad, N.; Ijiro, T.; Yamada, N.; Kawaguchi, T.; Maemura, T.; Ohashi, H.
2012-10-01
Optical design of a concentrating photovoltaic/thermal (CPVT) system is carried out. Using wavelength-selective optics, the system demonstrates 3-D concentration onto a solar cell and 2-D concentration onto a thermal receiver. Characteristics of the two types of concentrator systems are examined with ray-tracing analysis. The first system is a glazed mirror-based concentrator system mounted on a 2-axis pedestal tracker. The size of the secondary optical element is minimized to decrease the cost of the system, and it has a wavelength-selective function for performing 3-D concentration onto a solar cell and 2-D concentration onto a thermal receiver. The second system is a non-glazed beamdown concentrator system containing parabolic mirrors in the lower part. The beam-down selective mirror performs 3-D concentration onto a solar cell placed above the beam-down selective mirror, and 2-D concentration down to a thermal receiver placed at the bottom level. The system is mounted on a two-axis carousel tracker. A parametric study is performed for those systems with different geometrical 2-D/3-D concentration ratios. Wavelength-selective optics such as hot/cold mirrors and spectrum-splitting technologies are taken into account in the analysis. Results show reduced heat load on the solar cell and increased total system efficiency compared to a non-selective CPV system. Requirements for the wavelength-selective properties are elucidated. It is also shown that the hybrid concept with 2-D concentration onto a thermal receiver and 3-D concentration onto a solar cell has an advantageous geometry because of the high total system efficiency and compatibility with the piping arrangement of the thermal receiver.
2001-01-31
This software reduces the data from two-dimensional kSA MOS program, k-Space Associates, Ann Arbor, MI. Initial MOS data is recorded without headers in 38 columns, with one row of data per acquisition per lase beam tracked. The final MOSS 2d data file is reduced, graphed, and saved in a tab-delimited column format with headers that can be plotted in any graphing software.
An application of Ray + Born inversion on real data
Forgues, E.; Beukelaar, P. de; Coppens, F.; Richard, V.; Lambare, G.
1994-12-31
The authors present a linearized 2D acoustic and elastic multiparameter inversion of real marine seismic reflection data from the Gulf of Mexico. They solve the forward problem by a combination of Ray Theory and Born approximation. It fully takes advantage of efficiency of ray tracing in terms of computing, cost and physical comprehension. Lateral variations of background velocities can be introduced in the 2D ray tracing algorithm and a 2.5D approximation is done in order to take into account 3D propagation. The multiparameter inversion method is based on minimization of a weighted cost function. This weighted cost function is estimated from parameters associated with Ray and Paraxial Ray Theory and is introduced in order to diagonalize approximately the Hessian. This form of the Hessian allows the study of spatial resolution and conditioning of inversion.
Kolkoori, Sanjeevareddy; Hoehne, Christian; Prager, Jens; Rethmeier, Michael; Kreutzbruck, Marc
2014-02-01
Quantitative evaluation of ultrasonic C-scan images in homogeneous and layered anisotropic austenitic materials is of general importance for understanding the influence of anisotropy on wave fields during ultrasonic non-destructive testing and evaluation of these materials. In this contribution, a three dimensional ray tracing method is presented for evaluating ultrasonic C-scan images quantitatively in general homogeneous and layered anisotropic austenitic materials. The directivity of the ultrasonic ray source in general homogeneous columnar grained anisotropic austenitic steel material (including layback orientation) is obtained in three dimensions based on Lamb's reciprocity theorem. As a prerequisite for ray tracing model, the problem of ultrasonic ray energy reflection and transmission coefficients at an interface between (a) isotropic base material and anisotropic austenitic weld material (including layback orientation), (b) two adjacent anisotropic weld metals and (c) anisotropic weld metal and isotropic base material is solved in three dimensions. The influence of columnar grain orientation and layback orientation on ultrasonic C-scan image is quantitatively analyzed in the context of ultrasonic testing of homogeneous and layered austenitic steel materials. The presented quantitative results provide valuable information during ultrasonic characterization of homogeneous and layered anisotropic austenitic steel materials.
NASA Astrophysics Data System (ADS)
Amberger, Martin A.; Höltig, Michael; Broekaert, José A. C.
2010-02-01
The use of slurry sampling total reflection X-ray fluorescence spectrometry (SlS-TXRF) for the direct determination of Ca, Cr, Cu, Fe, Mn and Ti in four boron nitride powders has been described. Measurements of the zeta potential showed that slurries with good stabilities can be obtained by the addition of polyethylenimine (PEI) at a concentration of 0.1 wt.% and by adjusting the pH at 4. For the optimization of the concentration of boron nitride in the slurries the net line intensities and the signal to background ratios were determined for the trace elements Ca and Ti as well as for the internal standard element Ga in the case of concentrations of boron nitride ranging from 1 to 30 mg mL -1. As a compromise with respect to high net line intensities and high signal to background ratios, concentrations of 5 mg mL -1 of boron nitride were found suitable and were used for all further measurements. The limits of detection of SlS-TXRF for the boron nitride powders were found to range from 0.062 to 1.6 μg g - 1 for Cu and Ca, respectively. Herewith, they are higher than those obtained in solid sampling and slurry sampling graphite furnace atomic absorption spectrometry (SoS-GFAAS, SlS-GFAAS) as well as those of solid sampling electrothermal evaporation inductively coupled plasma optical emission spectrometry (SoS-ETV-ICP-OES). For Ca and Fe as well as for Cu and Fe, however, they were found to be lower than for GFAAS and for ICP-OES subsequent to wet chemical digestion, respectively. The universal applicability of SlS-TXRF to the analysis of samples with a wide variety of matrices could be demonstrated by the analysis of certified reference materials such as SiC, Al 2O 3, powdered bovine liver and borate ore with a single calibration. The correlation coefficients of the plots for the values found for Ca, Fe and Ti by SlS-TXRF in the boron nitride powders as well as in the before mentioned samples versus the reference values for the respective samples over a
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
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.
Simultaneous elastic parameter inversion in 2-D/3-D TTI medium combined later arrival times
NASA Astrophysics Data System (ADS)
Bai, Chao-ying; Wang, Tao; Yang, Shang-bei; Li, Xing-wang; Huang, Guo-jiao
2016-04-01
Traditional traveltime inversion for anisotropic medium is, in general, based on a "weak" assumption in the anisotropic property, which simplifies both the forward part (ray tracing is performed once only) and the inversion part (a linear inversion solver is possible). But for some real applications, a general (both "weak" and "strong") anisotropic medium should be considered. In such cases, one has to develop a ray tracing algorithm to handle with the general (including "strong") anisotropic medium and also to design a non-linear inversion solver for later tomography. Meanwhile, it is constructive to investigate how much the tomographic resolution can be improved by introducing the later arrivals. For this motivation, we incorporated our newly developed ray tracing algorithm (multistage irregular shortest-path method) for general anisotropic media with a non-linear inversion solver (a damped minimum norm, constrained least squares problem with a conjugate gradient approach) to formulate a non-linear inversion solver for anisotropic medium. This anisotropic traveltime inversion procedure is able to combine the later (reflected) arrival times. Both 2-D/3-D synthetic inversion experiments and comparison tests show that (1) the proposed anisotropic traveltime inversion scheme is able to recover the high contrast anomalies and (2) it is possible to improve the tomographic resolution by introducing the later (reflected) arrivals, but not as expected in the isotropic medium, because the different velocity (qP, qSV and qSH) sensitivities (or derivatives) respective to the different elastic parameters are not the same but are also dependent on the inclination angle.
2D full wave modeling for a synthetic Doppler backscattering diagnostic
Hillesheim, J. C.; Schmitz, L.; Kubota, S.; Rhodes, T. L.; Carter, T. A.; Holland, C.
2012-10-15
Doppler backscattering (DBS) is a plasma diagnostic used in tokamaks and other magnetic confinement devices to measure the fluctuation level of intermediate wavenumber (k{sub {theta}}{rho}{sub s}{approx} 1) density fluctuations and the lab frame propagation velocity of turbulence. Here, a synthetic DBS diagnostic is described, which has been used for comparisons between measurements in the DIII-D tokamak and predictions from nonlinear gyrokinetic simulations. To estimate the wavenumber range to which a Gaussian beam would be sensitive, a ray tracing code and a 2D finite difference, time domain full wave code are used. Experimental density profiles and magnetic geometry are used along with the experimental antenna and beam characteristics. An example of the effect of the synthetic diagnostic on the output of a nonlinear gyrokinetic simulation is presented.
2D full wave modeling for a synthetic Doppler backscattering diagnostica)
NASA Astrophysics Data System (ADS)
Hillesheim, J. C.; Holland, C.; Schmitz, L.; Kubota, S.; Rhodes, T. L.; Carter, T. A.
2012-10-01
Doppler backscattering (DBS) is a plasma diagnostic used in tokamaks and other magnetic confinement devices to measure the fluctuation level of intermediate wavenumber (kθρs ˜ 1) density fluctuations and the lab frame propagation velocity of turbulence. Here, a synthetic DBS diagnostic is described, which has been used for comparisons between measurements in the DIII-D tokamak and predictions from nonlinear gyrokinetic simulations. To estimate the wavenumber range to which a Gaussian beam would be sensitive, a ray tracing code and a 2D finite difference, time domain full wave code are used. Experimental density profiles and magnetic geometry are used along with the experimental antenna and beam characteristics. An example of the effect of the synthetic diagnostic on the output of a nonlinear gyrokinetic simulation is presented.
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.
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.
NASA Astrophysics Data System (ADS)
Wee, Tae-Kwon; Kuo, Ying-Hwa; Lee, Dong-Kyou
2010-12-01
A two-dimensional curved ray tracer (CRT) is developed to study the propagation path of radio signals across a heterogeneous planetary atmosphere. The method, designed to achieve improvements in both computational efficiency and accuracy over conventional straight-line methods, takes rays' first-order bending into account to better describe curved raypaths in the stratified atmosphere. CRT is then used to simulate the phase path from GPS radio occultation (RO). The merit of the ray tracing approach in GPS RO is explicit consideration of horizontal variation in the atmosphere, which may lead to a sizable error but is disregarded in traditional retrieval schemes. In addition, direct modeling of the phase path takes advantage of simple error characteristics in the measurement. With provision of ionospheric and neutral atmospheric refractive indices, in this effort, rays are traced along the full range of GPS-low Earth orbiting (LEO) radio links just as the measurements are made in real life. Here, ray shooting is employed to realize the observed radio links with controlled accuracy. CRT largely reproduces the very measured characteristics of GPS signals. When compared, the measured and simulated phases show remarkable agreement. The cross validation between CRT and GPS RO has confirmed not only the strength of CRT but also the high accuracy of GPS RO measurements. The primary motivation for this study is enabling effective quality control for GPS RO data, overcoming a complicated error structure in the high-level data. CRT has also shown a great deal of potential for improved utilization of GPS RO data for geophysical research.
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
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.
Georgi, Howard; Kats, Yevgeny
2008-09-26
We discuss what can be learned about unparticle physics by studying simple quantum field theories in one space and one time dimension. We argue that the exactly soluble 2D theory of a massless fermion coupled to a massive vector boson, the Sommerfield model, is an interesting analog of a Banks-Zaks model, approaching a free theory at high energies and a scale-invariant theory with nontrivial anomalous dimensions at low energies. We construct a toy standard model coupling to the fermions in the Sommerfield model and study how the transition from unparticle behavior at low energies to free particle behavior at high energies manifests itself in interactions with the toy standard model particles.
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.
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
NASA Astrophysics Data System (ADS)
Vilmer, N. R.; Dauphin, C.; Krucker, S.
2004-05-01
During their transit on the solar disk AR 0488 and AR0486 produced 12 X-class flares. Two of these flares (28 October 2003 and 3 November 2003) were observed at both X-ray/gamma-ray wavelengths by the RHESSI experiment and by the Nancay Radioheliograph. We shall present here results for the 3 November 2003 event which was observed and imaged up to several 100 keV by RHESSI and which produced at radio wavelengths a type II burst with an unusually high starting frequency and a long duration continuum extending from the low corona to the interplanetary medium. The combined analysis of RHESSI sources at energies above a few hundred keV and of metric/decimetric sources observed by the NRH shows a spatial extension of both X-ray and radio sources traced by energetic electrons between the impulsive part of the event and the late energetic X-ray phase associated with the radio continuum. This spatial extension will be discussed in the context of the shock-associated type II burst and of the CME onset. Analysis of radio and X-ray spectra will be tentatively done to investigate the nature of the radio continuum.
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.
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
NASA Astrophysics Data System (ADS)
Wyrowski, F.; Kuhn, M.
2011-03-01
Field tracing is the generalization of ray tracing and enables electromagnetic system modeling. Harmonic fields are traced through the optical system instead of ray bundles. This allows the smooth combination of different modeling techniques in different subdomains of the system, e.g. to use the rigorous spectrum-of-plane-wave operator for homogeneous media, geometrical optics to trace through a lens and finite element methods to include the effect of some scatterer. All modeling techniques have to be formulated for vectorial harmonic fields. The paper introduces the basic concepts of field tracing and derives the corresponding operator equations. Propagation in homogeneous media is of special concern in field tracing to interconnect the modeling in different subdomains of the system. A new concept for a smart propagation algorithm is presented. Because of the success of geometrical optics in ray tracing, it is reasonable to consider its application in field tracing. In this paper we discuss generalizations of geometrical optics that have been enforced by field tracing. Although the basic field tracing equations are formulated for vectorial harmonic fields, general fields can be treated by suitable decompositions into sets of harmonic modes.
CVMAC 2D Program: A method of converting 3D to 2D
Lown, J.
1990-06-20
This paper presents the user with a method of converting a three- dimensional wire frame model into a technical illustration, detail, or assembly drawing. By using the 2D Program, entities can be mapped from three-dimensional model space into two-dimensional model space, as if they are being traced. Selected entities to be mapped can include circles, arcs, lines, and points. This program prompts the user to digitize the view to be mapped, specify the layers in which the new two-dimensional entities will reside, and select the entities, either by digitizing or windowing. The new two-dimensional entities are displayed in a small view which the program creates in the lower left corner of the drawing. 9 figs.
Niemann, A.; von Bohlen, A.; Klockenkaemper, R.K.; Keck, E. )
1990-08-16
An in-vitro tissue culture system with folded periostea of 17-day-old fetal chick calvaria was combined with analytical methods to achieve quantification of biomineralization. A scanning electron microscope with an energy-dispersive X-ray detector was applied to show the distribution of calcium, phosphorus and trace elements. Calcium and phosphorus were concentrated in the zone of the mineralized matrix. Strontium was distributed similar to calcium. Zinc was distributed equally in the soft tissue and the mineralized matrix. Total-reflection X-ray fluorescence was used for quantification. Thyroxine in high concentration reduces the calcium content of the samples. One week after incubation magnesium chloride (1.8 mM) or zinc chloride (.1 mM) were found to reduce the calcium content by 38% or 82%, respectively.