Science.gov

Sample records for accurate simulation results

  1. Accurate thermoplasmonic simulation of metallic nanoparticles

    NASA Astrophysics Data System (ADS)

    Yu, Da-Miao; Liu, Yan-Nan; Tian, Fa-Lin; Pan, Xiao-Min; Sheng, Xin-Qing

    2017-01-01

    Thermoplasmonics leads to enhanced heat generation due to the localized surface plasmon resonances. The measurement of heat generation is fundamentally a complicated task, which necessitates the development of theoretical simulation techniques. In this paper, an efficient and accurate numerical scheme is proposed for applications with complex metallic nanostructures. Light absorption and temperature increase are, respectively, obtained by solving the volume integral equation (VIE) and the steady-state heat diffusion equation through the method of moments (MoM). Previously, methods based on surface integral equations (SIEs) were utilized to obtain light absorption. However, computing light absorption from the equivalent current is as expensive as O(NsNv), where Ns and Nv, respectively, denote the number of surface and volumetric unknowns. Our approach reduces the cost to O(Nv) by using VIE. The accuracy, efficiency and capability of the proposed scheme are validated by multiple simulations. The simulations show that our proposed method is more efficient than the approach based on SIEs under comparable accuracy, especially for the case where many incidents are of interest. The simulations also indicate that the temperature profile can be tuned by several factors, such as the geometry configuration of array, beam direction, and light wavelength.

  2. Time-Accurate Numerical Simulations of Synthetic Jet Quiescent Air

    NASA Technical Reports Server (NTRS)

    Rupesh, K-A. B.; Ravi, B. R.; Mittal, R.; Raju, R.; Gallas, Q.; Cattafesta, L.

    2007-01-01

    The unsteady evolution of three-dimensional synthetic jet into quiescent air is studied by time-accurate numerical simulations using a second-order accurate mixed explicit-implicit fractional step scheme on Cartesian grids. Both two-dimensional and three-dimensional calculations of synthetic jet are carried out at a Reynolds number (based on average velocity during the discharge phase of the cycle V(sub j), and jet width d) of 750 and Stokes number of 17.02. The results obtained are assessed against PIV and hotwire measurements provided for the NASA LaRC workshop on CFD validation of synthetic jets.

  3. Time accurate simulations of compressible shear flows

    NASA Technical Reports Server (NTRS)

    Givi, Peyman; Steinberger, Craig J.; Vidoni, Thomas J.; Madnia, Cyrus K.

    1993-01-01

    The objectives of this research are to employ direct numerical simulation (DNS) to study the phenomenon of mixing (or lack thereof) in compressible free shear flows and to suggest new means of enhancing mixing in such flows. The shear flow configurations under investigation are those of parallel mixing layers and planar jets under both non-reacting and reacting nonpremixed conditions. During the three-years of this research program, several important issues regarding mixing and chemical reactions in compressible shear flows were investigated.

  4. Accurate simulation of optical properties in dyes.

    PubMed

    Jacquemin, Denis; Perpète, Eric A; Ciofini, Ilaria; Adamo, Carlo

    2009-02-17

    Since Antiquity, humans have produced and commercialized dyes. To this day, extraction of natural dyes often requires lengthy and costly procedures. In the 19th century, global markets and new industrial products drove a significant effort to synthesize artificial dyes, characterized by low production costs, huge quantities, and new optical properties (colors). Dyes that encompass classes of molecules absorbing in the UV-visible part of the electromagnetic spectrum now have a wider range of applications, including coloring (textiles, food, paintings), energy production (photovoltaic cells, OLEDs), or pharmaceuticals (diagnostics, drugs). Parallel to the growth in dye applications, researchers have increased their efforts to design and synthesize new dyes to customize absorption and emission properties. In particular, dyes containing one or more metallic centers allow for the construction of fairly sophisticated systems capable of selectively reacting to light of a given wavelength and behaving as molecular devices (photochemical molecular devices, PMDs).Theoretical tools able to predict and interpret the excited-state properties of organic and inorganic dyes allow for an efficient screening of photochemical centers. In this Account, we report recent developments defining a quantitative ab initio protocol (based on time-dependent density functional theory) for modeling dye spectral properties. In particular, we discuss the importance of several parameters, such as the methods used for electronic structure calculations, solvent effects, and statistical treatments. In addition, we illustrate the performance of such simulation tools through case studies. We also comment on current weak points of these methods and ways to improve them.

  5. Accurate stress resultants equations for laminated composite deep thick shells

    SciTech Connect

    Qatu, M.S.

    1995-11-01

    This paper derives accurate equations for the normal and shear force as well as bending and twisting moment resultants for laminated composite deep, thick shells. The stress resultant equations for laminated composite thick shells are shown to be different from those of plates. This is due to the fact the stresses over the thickness of the shell have to be integrated on a trapezoidal-like shell element to obtain the stress resultants. Numerical results are obtained and showed that accurate stress resultants are needed for laminated composite deep thick shells, especially if the curvature is not spherical.

  6. Can numerical simulations accurately predict hydrodynamic instabilities in liquid films?

    NASA Astrophysics Data System (ADS)

    Denner, Fabian; Charogiannis, Alexandros; Pradas, Marc; van Wachem, Berend G. M.; Markides, Christos N.; Kalliadasis, Serafim

    2014-11-01

    Understanding the dynamics of hydrodynamic instabilities in liquid film flows is an active field of research in fluid dynamics and non-linear science in general. Numerical simulations offer a powerful tool to study hydrodynamic instabilities in film flows and can provide deep insights into the underlying physical phenomena. However, the direct comparison of numerical results and experimental results is often hampered by several reasons. For instance, in numerical simulations the interface representation is problematic and the governing equations and boundary conditions may be oversimplified, whereas in experiments it is often difficult to extract accurate information on the fluid and its behavior, e.g. determine the fluid properties when the liquid contains particles for PIV measurements. In this contribution we present the latest results of our on-going, extensive study on hydrodynamic instabilities in liquid film flows, which includes direct numerical simulations, low-dimensional modelling as well as experiments. The major focus is on wave regimes, wave height and wave celerity as a function of Reynolds number and forcing frequency of a falling liquid film. Specific attention is paid to the differences in numerical and experimental results and the reasons for these differences. The authors are grateful to the EPSRC for their financial support (Grant EP/K008595/1).

  7. Accurate Langevin approaches to simulate Markovian channel dynamics

    NASA Astrophysics Data System (ADS)

    Huang, Yandong; Rüdiger, Sten; Shuai, Jianwei

    2015-12-01

    The stochasticity of ion-channels dynamic is significant for physiological processes on neuronal cell membranes. Microscopic simulations of the ion-channel gating with Markov chains can be considered to be an accurate standard. However, such Markovian simulations are computationally demanding for membrane areas of physiologically relevant sizes, which makes the noise-approximating or Langevin equation methods advantageous in many cases. In this review, we discuss the Langevin-like approaches, including the channel-based and simplified subunit-based stochastic differential equations proposed by Fox and Lu, and the effective Langevin approaches in which colored noise is added to deterministic differential equations. In the framework of Fox and Lu’s classical models, several variants of numerical algorithms, which have been recently developed to improve accuracy as well as efficiency, are also discussed. Through the comparison of different simulation algorithms of ion-channel noise with the standard Markovian simulation, we aim to reveal the extent to which the existing Langevin-like methods approximate results using Markovian methods. Open questions for future studies are also discussed.

  8. Progress in fast, accurate multi-scale climate simulations

    DOE PAGES

    Collins, W. D.; Johansen, H.; Evans, K. J.; ...

    2015-06-01

    We present a survey of physical and computational techniques that have the potential to contribute to the next generation of high-fidelity, multi-scale climate simulations. Examples of the climate science problems that can be investigated with more depth with these computational improvements include the capture of remote forcings of localized hydrological extreme events, an accurate representation of cloud features over a range of spatial and temporal scales, and parallel, large ensembles of simulations to more effectively explore model sensitivities and uncertainties. Numerical techniques, such as adaptive mesh refinement, implicit time integration, and separate treatment of fast physical time scales are enablingmore » improved accuracy and fidelity in simulation of dynamics and allowing more complete representations of climate features at the global scale. At the same time, partnerships with computer science teams have focused on taking advantage of evolving computer architectures such as many-core processors and GPUs. As a result, approaches which were previously considered prohibitively costly have become both more efficient and scalable. In combination, progress in these three critical areas is poised to transform climate modeling in the coming decades.« less

  9. Progress in fast, accurate multi-scale climate simulations

    SciTech Connect

    Collins, W. D.; Johansen, H.; Evans, K. J.; Woodward, C. S.; Caldwell, P. M.

    2015-06-01

    We present a survey of physical and computational techniques that have the potential to contribute to the next generation of high-fidelity, multi-scale climate simulations. Examples of the climate science problems that can be investigated with more depth with these computational improvements include the capture of remote forcings of localized hydrological extreme events, an accurate representation of cloud features over a range of spatial and temporal scales, and parallel, large ensembles of simulations to more effectively explore model sensitivities and uncertainties. Numerical techniques, such as adaptive mesh refinement, implicit time integration, and separate treatment of fast physical time scales are enabling improved accuracy and fidelity in simulation of dynamics and allowing more complete representations of climate features at the global scale. At the same time, partnerships with computer science teams have focused on taking advantage of evolving computer architectures such as many-core processors and GPUs. As a result, approaches which were previously considered prohibitively costly have become both more efficient and scalable. In combination, progress in these three critical areas is poised to transform climate modeling in the coming decades.

  10. ICAAS piloted simulation results

    NASA Astrophysics Data System (ADS)

    Landy, R. J.; Halski, P. J.; Meyer, R. P.

    1994-05-01

    This paper reports piloted simulation results from the Integrated Control and Avionics for Air Superiority (ICAAS) piloted simulation evaluations. The program was to develop, integrate, and demonstrate critical technologies which will enable United States Air Force tactical fighter 'blue' aircraft to achieve superiority and survive when outnumbered by as much as four to one by enemy aircraft during air combat engagements. Primary emphasis was placed on beyond visual range (BVR) combat with provisions for effective transition to close-in combat. The ICAAS system was developed and tested in two stages. The first stage, called low risk ICAAS, was defined as employing aircraft and avionics technology with an initial operational date no later than 1995. The second stage, called medium risk ICAAS, was defined as employing aircraft and avionics technology with an initial operational date no later than 1998. Descriptions of the low risk and medium risk simulation configurations are given. Normalized (unclassified) results from both the low risk and medium risk ICAAS simulations are discussed. The results show the ICAAS system provided a significant improvement in air combat performance when compared to a current weapon system. Data are presented for both current generation and advanced fighter aircraft. The ICAAS technologies which are ready for flight testing in order to transition to the fighter fleet are described along with technologies needing additional development.

  11. Development of accurate force fields for the simulation of biomineralization.

    PubMed

    Raiteri, Paolo; Demichelis, Raffaella; Gale, Julian D

    2013-01-01

    The existence of an accurate force field (FF) model that reproduces the free-energy landscape is a key prerequisite for the simulation of biomineralization. Here, the stages in the development of such a model are discussed including the quality of the water model, the thermodynamics of polymorphism, and the free energies of solvation for the relevant species. The reliability of FFs can then be benchmarked against quantities such as the free energy of ion pairing in solution, the solubility product, and the structure of the mineral-water interface.

  12. D-BRAIN: Anatomically Accurate Simulated Diffusion MRI Brain Data.

    PubMed

    Perrone, Daniele; Jeurissen, Ben; Aelterman, Jan; Roine, Timo; Sijbers, Jan; Pizurica, Aleksandra; Leemans, Alexander; Philips, Wilfried

    2016-01-01

    Diffusion Weighted (DW) MRI allows for the non-invasive study of water diffusion inside living tissues. As such, it is useful for the investigation of human brain white matter (WM) connectivity in vivo through fiber tractography (FT) algorithms. Many DW-MRI tailored restoration techniques and FT algorithms have been developed. However, it is not clear how accurately these methods reproduce the WM bundle characteristics in real-world conditions, such as in the presence of noise, partial volume effect, and a limited spatial and angular resolution. The difficulty lies in the lack of a realistic brain phantom on the one hand, and a sufficiently accurate way of modeling the acquisition-related degradation on the other. This paper proposes a software phantom that approximates a human brain to a high degree of realism and that can incorporate complex brain-like structural features. We refer to it as a Diffusion BRAIN (D-BRAIN) phantom. Also, we propose an accurate model of a (DW) MRI acquisition protocol to allow for validation of methods in realistic conditions with data imperfections. The phantom model simulates anatomical and diffusion properties for multiple brain tissue components, and can serve as a ground-truth to evaluate FT algorithms, among others. The simulation of the acquisition process allows one to include noise, partial volume effects, and limited spatial and angular resolution in the images. In this way, the effect of image artifacts on, for instance, fiber tractography can be investigated with great detail. The proposed framework enables reliable and quantitative evaluation of DW-MR image processing and FT algorithms at the level of large-scale WM structures. The effect of noise levels and other data characteristics on cortico-cortical connectivity and tractography-based grey matter parcellation can be investigated as well.

  13. On the accurate simulation of tsunami wave propagation

    NASA Astrophysics Data System (ADS)

    Castro, C. E.; Käser, M.; Toro, E. F.

    2009-04-01

    A very important part of any tsunami early warning system is the numerical simulation of the wave propagation in the open sea and close to geometrically complex coastlines respecting bathymetric variations. Here we are interested in improving the numerical tools available to accurately simulate tsunami wave propagation on a Mediterranean basin scale. To this end, we need to accomplish some targets, such as: high-order numerical simulation in space and time, preserve steady state conditions to avoid spurious oscillations and describe complex geometries due to bathymetry and coastlines. We use the Arbitrary accuracy DERivatives Riemann problem method together with Finite Volume method (ADER-FV) over non-structured triangular meshes. The novelty of this method is the improvement of the ADER-FV scheme, introducing the well-balanced property when geometrical sources are considered for unstructured meshes and arbitrary high-order accuracy. In a previous work from Castro and Toro [1], the authors mention that ADER-FV schemes approach asymptotically the well-balanced condition, which was true for the test case mentioned in [1]. However, new evidence[2] shows that for real scale problems as the Mediterranean basin, and considering realistic bathymetry as ETOPO-2[3], this asymptotic behavior is not enough. Under these realistic conditions the standard ADER-FV scheme fails to accurately describe the propagation of gravity waves without being contaminated with spurious oscillations, also known as numerical waves. The main problem here is that at discrete level, i.e. from a numerical point of view, the numerical scheme does not correctly balance the influence of the fluxes and the sources. Numerical schemes that retain this balance are said to satisfy the well-balanced property or the exact C-property. This unbalance reduces, as we refine the spatial discretization or increase the order of the numerical method. However, the computational cost increases considerably this way

  14. Progress in Fast, Accurate Multi-scale Climate Simulations

    SciTech Connect

    Collins, William D; Johansen, Hans; Evans, Katherine J; Woodward, Carol S.; Caldwell, Peter

    2015-01-01

    We present a survey of physical and computational techniques that have the potential to con- tribute to the next generation of high-fidelity, multi-scale climate simulations. Examples of the climate science problems that can be investigated with more depth include the capture of remote forcings of localized hydrological extreme events, an accurate representation of cloud features over a range of spatial and temporal scales, and parallel, large ensembles of simulations to more effectively explore model sensitivities and uncertainties. Numerical techniques, such as adaptive mesh refinement, implicit time integration, and separate treatment of fast physical time scales are enabling improved accuracy and fidelity in simulation of dynamics and allow more complete representations of climate features at the global scale. At the same time, part- nerships with computer science teams have focused on taking advantage of evolving computer architectures, such as many-core processors and GPUs, so that these approaches which were previously considered prohibitively costly have become both more efficient and scalable. In combination, progress in these three critical areas is poised to transform climate modeling in the coming decades.

  15. How Accurate Are Transition States from Simulations of Enzymatic Reactions?

    PubMed Central

    2015-01-01

    The rate expression of traditional transition state theory (TST) assumes no recrossing of the transition state (TS) and thermal quasi-equilibrium between the ground state and the TS. Currently, it is not well understood to what extent these assumptions influence the nature of the activated complex obtained in traditional TST-based simulations of processes in the condensed phase in general and in enzymes in particular. Here we scrutinize these assumptions by characterizing the TSs for hydride transfer catalyzed by the enzyme Escherichia coli dihydrofolate reductase obtained using various simulation approaches. Specifically, we compare the TSs obtained with common TST-based methods and a dynamics-based method. Using a recently developed accurate hybrid quantum mechanics/molecular mechanics potential, we find that the TST-based and dynamics-based methods give considerably different TS ensembles. This discrepancy, which could be due equilibrium solvation effects and the nature of the reaction coordinate employed and its motion, raises major questions about how to interpret the TSs determined by common simulation methods. We conclude that further investigation is needed to characterize the impact of various TST assumptions on the TS phase-space ensemble and on the reaction kinetics. PMID:24860275

  16. Accurate Behavioral Simulator of All-Digital Time-Domain Smart Temperature Sensors by Using SIMULINK.

    PubMed

    Chen, Chun-Chi; Chen, Chao-Lieh; Lin, You-Ting

    2016-08-08

    This study proposes a new behavioral simulator that uses SIMULINK for all-digital CMOS time-domain smart temperature sensors (TDSTSs) for performing rapid and accurate simulations. Inverter-based TDSTSs offer the benefits of low cost and simple structure for temperature-to-digital conversion and have been developed. Typically, electronic design automation tools, such as HSPICE, are used to simulate TDSTSs for performance evaluations. However, such tools require extremely long simulation time and complex procedures to analyze the results and generate figures. In this paper, we organize simple but accurate equations into a temperature-dependent model (TDM) by which the TDSTSs evaluate temperature behavior. Furthermore, temperature-sensing models of a single CMOS NOT gate were devised using HSPICE simulations. Using the TDM and these temperature-sensing models, a novel simulator in SIMULINK environment was developed to substantially accelerate the simulation and simplify the evaluation procedures. Experiments demonstrated that the simulation results of the proposed simulator have favorable agreement with those obtained from HSPICE simulations, showing that the proposed simulator functions successfully. This is the first behavioral simulator addressing the rapid simulation of TDSTSs.

  17. Accurate Behavioral Simulator of All-Digital Time-Domain Smart Temperature Sensors by Using SIMULINK

    PubMed Central

    Chen, Chun-Chi; Chen, Chao-Lieh; Lin, You-Ting

    2016-01-01

    This study proposes a new behavioral simulator that uses SIMULINK for all-digital CMOS time-domain smart temperature sensors (TDSTSs) for performing rapid and accurate simulations. Inverter-based TDSTSs offer the benefits of low cost and simple structure for temperature-to-digital conversion and have been developed. Typically, electronic design automation tools, such as HSPICE, are used to simulate TDSTSs for performance evaluations. However, such tools require extremely long simulation time and complex procedures to analyze the results and generate figures. In this paper, we organize simple but accurate equations into a temperature-dependent model (TDM) by which the TDSTSs evaluate temperature behavior. Furthermore, temperature-sensing models of a single CMOS NOT gate were devised using HSPICE simulations. Using the TDM and these temperature-sensing models, a novel simulator in SIMULINK environment was developed to substantially accelerate the simulation and simplify the evaluation procedures. Experiments demonstrated that the simulation results of the proposed simulator have favorable agreement with those obtained from HSPICE simulations, showing that the proposed simulator functions successfully. This is the first behavioral simulator addressing the rapid simulation of TDSTSs. PMID:27509507

  18. Symphony: a framework for accurate and holistic WSN simulation.

    PubMed

    Riliskis, Laurynas; Osipov, Evgeny

    2015-02-25

    Research on wireless sensor networks has progressed rapidly over the last decade, and these technologies have been widely adopted for both industrial and domestic uses. Several operating systems have been developed, along with a multitude of network protocols for all layers of the communication stack. Industrial Wireless Sensor Network (WSN) systems must satisfy strict criteria and are typically more complex and larger in scale than domestic systems. Together with the non-deterministic behavior of network hardware in real settings, this greatly complicates the debugging and testing of WSN functionality. To facilitate the testing, validation, and debugging of large-scale WSN systems, we have developed a simulation framework that accurately reproduces the processes that occur inside real equipment, including both hardware- and software-induced delays. The core of the framework consists of a virtualized operating system and an emulated hardware platform that is integrated with the general purpose network simulator ns-3. Our framework enables the user to adjust the real code base as would be done in real deployments and also to test the boundary effects of different hardware components on the performance of distributed applications and protocols. Additionally we have developed a clock emulator with several different skew models and a component that handles sensory data feeds. The new framework should substantially shorten WSN application development cycles.

  19. Symphony: A Framework for Accurate and Holistic WSN Simulation

    PubMed Central

    Riliskis, Laurynas; Osipov, Evgeny

    2015-01-01

    Research on wireless sensor networks has progressed rapidly over the last decade, and these technologies have been widely adopted for both industrial and domestic uses. Several operating systems have been developed, along with a multitude of network protocols for all layers of the communication stack. Industrial Wireless Sensor Network (WSN) systems must satisfy strict criteria and are typically more complex and larger in scale than domestic systems. Together with the non-deterministic behavior of network hardware in real settings, this greatly complicates the debugging and testing of WSN functionality. To facilitate the testing, validation, and debugging of large-scale WSN systems, we have developed a simulation framework that accurately reproduces the processes that occur inside real equipment, including both hardware- and software-induced delays. The core of the framework consists of a virtualized operating system and an emulated hardware platform that is integrated with the general purpose network simulator ns-3. Our framework enables the user to adjust the real code base as would be done in real deployments and also to test the boundary effects of different hardware components on the performance of distributed applications and protocols. Additionally we have developed a clock emulator with several different skew models and a component that handles sensory data feeds. The new framework should substantially shorten WSN application development cycles. PMID:25723144

  20. Accurate Simulation of Acoustic Emission Sources in Composite Plates

    NASA Technical Reports Server (NTRS)

    Prosser, W. H.; Gorman, M. R.

    1994-01-01

    Acoustic emission (AE) signals propagate as the extensional and flexural plate modes in thin composite plates and plate-like geometries such as shells, pipes, and tubes. The relative amplitude of the two modes depends on the directionality of the source motion. For source motions with large out-of-plane components such as delaminations or particle impact, the flexural or bending plate mode dominates the AE signal with only a small extensional mode detected. A signal from such a source is well simulated with the standard pencil lead break (Hsu-Neilsen source) on the surface of the plate. For other sources such as matrix cracking or fiber breakage in which the source motion is primarily in-plane, the resulting AE signal has a large extensional mode component with little or no flexural mode observed. Signals from these type sources can also be simulated with pencil lead breaks. However, the lead must be fractured on the edge of the plate to generate an in-plane source motion rather than on the surface of the plate. In many applications such as testing of pressure vessels and piping or aircraft structures, a free edge is either not available or not in a desired location for simulation of in-plane type sources. In this research, a method was developed which allows the simulation of AE signals with a predominant extensional mode component in composite plates requiring access to only the surface of the plate.

  1. Quantum circuit design for accurate simulation of qudit channels

    NASA Astrophysics Data System (ADS)

    Wang, Dong-Sheng; Sanders, Barry C.

    2015-04-01

    We construct a classical algorithm that designs quantum circuits for algorithmic quantum simulation of arbitrary qudit channels on fault-tolerant quantum computers within a pre-specified error tolerance with respect to diamond-norm distance. The classical algorithm is constructed by decomposing a quantum channel into a convex combination of generalized extreme channels by convex optimization of a set of nonlinear coupled algebraïc equations. The resultant circuit is a randomly chosen generalized extreme channel circuit whose run-time is logarithmic with respect to the error tolerance and quadratic with respect to Hilbert space dimension, which requires only a single ancillary qudit plus classical dits.

  2. Accurate numerical simulation of short fiber optical parametric amplifiers.

    PubMed

    Marhic, M E; Rieznik, A A; Kalogerakis, G; Braimiotis, C; Fragnito, H L; Kazovsky, L G

    2008-03-17

    We improve the accuracy of numerical simulations for short fiber optical parametric amplifiers (OPAs). Instead of using the usual coarse-step method, we adopt a model for birefringence and dispersion which uses fine-step variations of the parameters. We also improve the split-step Fourier method by exactly treating the nonlinear ellipse rotation terms. We find that results obtained this way for two-pump OPAs can be significantly different from those obtained by using the usual coarse-step fiber model, and/or neglecting ellipse rotation terms.

  3. Open cherry picker simulation results

    NASA Technical Reports Server (NTRS)

    Nathan, C. A.

    1982-01-01

    The simulation program associated with a key piece of support equipment to be used to service satellites directly from the Shuttle is assessed. The Open Cherry Picker (OCP) is a manned platform mounted at the end of the remote manipulator system (RMS) and is used to enhance extra vehicular activities (EVA). The results of simulations performed on the Grumman Large Amplitude Space Simulator (LASS) and at the JSC Water Immersion Facility are summarized.

  4. Accurate Position Sensing of Defocused Beams Using Simulated Beam Templates

    SciTech Connect

    Awwal, A; Candy, J; Haynam, C; Widmayer, C; Bliss, E; Burkhart, S

    2004-09-29

    In position detection using matched filtering one is faced with the challenge of determining the best position in the presence of distortions such as defocus and diffraction noise. This work evaluates the performance of simulated defocused images as the template against the real defocused beam. It was found that an amplitude modulated phase-only filter is better equipped to deal with real defocused images that suffer from diffraction noise effects resulting in a textured spot intensity pattern. It is shown that the there is a tradeoff of performance dependent upon the type and size of the defocused image. A novel automated system was developed that can automatically select the right template type and size. Results of this automation for real defocused images are presented.

  5. Accurate direct Eulerian simulation of dynamic elastic-plastic flow

    SciTech Connect

    Kamm, James R; Walter, John W

    2009-01-01

    The simulation of dynamic, large strain deformation is an important, difficult, and unsolved computational challenge. Existing Eulerian schemes for dynamic material response are plagued by unresolved issues. We present a new scheme for the first-order system of elasto-plasticity equations in the Eulerian frame. This system has an intrinsic constraint on the inverse deformation gradient. Standard Godunov schemes do not satisfy this constraint. The method of Flux Distributions (FD) was devised to discretely enforce such constraints for numerical schemes with cell-centered variables. We describe a Flux Distribution approach that enforces the inverse deformation gradient constraint. As this approach is new and novel, we do not yet have numerical results to validate our claims. This paper is the first installment of our program to develop this new method.

  6. Improving light propagation Monte Carlo simulations with accurate 3D modeling of skin tissue

    SciTech Connect

    Paquit, Vincent C; Price, Jeffery R; Meriaudeau, Fabrice; Tobin Jr, Kenneth William

    2008-01-01

    In this paper, we present a 3D light propagation model to simulate multispectral reflectance images of large skin surface areas. In particular, we aim to simulate more accurately the effects of various physiological properties of the skin in the case of subcutaneous vein imaging compared to existing models. Our method combines a Monte Carlo light propagation model, a realistic three-dimensional model of the skin using parametric surfaces and a vision system for data acquisition. We describe our model in detail, present results from the Monte Carlo modeling and compare our results with those obtained with a well established Monte Carlo model and with real skin reflectance images.

  7. Accurate Evaluation of the Dispersion Energy in the Simulation of Gas Adsorption into Porous Zeolites.

    PubMed

    Fraccarollo, Alberto; Canti, Lorenzo; Marchese, Leonardo; Cossi, Maurizio

    2017-03-07

    The force fields used to simulate the gas adsorption in porous materials are strongly dominated by the van der Waals (vdW) terms. Here we discuss the delicate problem to estimate these terms accurately, analyzing the effect of different models. To this end, we simulated the physisorption of CH4, CO2, and Ar into various Al-free microporous zeolites (ITQ-29, SSZ-13, and silicalite-1), comparing the theoretical results with accurate experimental isotherms. The vdW terms in the force fields were parametrized against the free gas densities and high-level quantum mechanical (QM) calculations, comparing different methods to evaluate the dispersion energies. In particular, MP2 and DFT with semiempirical corrections, with suitable basis sets, were chosen to approximate the best QM calculations; either Lennard-Jones or Morse expressions were used to include the vdW terms in the force fields. The comparison of the simulated and experimental isotherms revealed that a strong interplay exists between the definition of the dispersion energies and the functional form used in the force field; these results are fairly general and reproducible, at least for the systems considered here. On this basis, the reliability of different models can be discussed, and a recipe can be provided to obtain accurate simulated adsorption isotherms.

  8. Massively Parallel Processing for Fast and Accurate Stamping Simulations

    NASA Astrophysics Data System (ADS)

    Gress, Jeffrey J.; Xu, Siguang; Joshi, Ramesh; Wang, Chuan-tao; Paul, Sabu

    2005-08-01

    The competitive automotive market drives automotive manufacturers to speed up the vehicle development cycles and reduce the lead-time. Fast tooling development is one of the key areas to support fast and short vehicle development programs (VDP). In the past ten years, the stamping simulation has become the most effective validation tool in predicting and resolving all potential formability and quality problems before the dies are physically made. The stamping simulation and formability analysis has become an critical business segment in GM math-based die engineering process. As the simulation becomes as one of the major production tools in engineering factory, the simulation speed and accuracy are the two of the most important measures for stamping simulation technology. The speed and time-in-system of forming analysis becomes an even more critical to support the fast VDP and tooling readiness. Since 1997, General Motors Die Center has been working jointly with our software vendor to develop and implement a parallel version of simulation software for mass production analysis applications. By 2001, this technology was matured in the form of distributed memory processing (DMP) of draw die simulations in a networked distributed memory computing environment. In 2004, this technology was refined to massively parallel processing (MPP) and extended to line die forming analysis (draw, trim, flange, and associated spring-back) running on a dedicated computing environment. The evolution of this technology and the insight gained through the implementation of DM0P/MPP technology as well as performance benchmarks are discussed in this publication.

  9. Toward the Accurate Simulation of Two-Dimensional Electronic Spectra

    NASA Astrophysics Data System (ADS)

    Giussani, Angelo; Nenov, Artur; Segarra-Martí, Javier; Jaiswal, Vishal K.; Rivalta, Ivan; Dumont, Elise; Mukamel, Shaul; Garavelli, Marco

    2015-06-01

    Two-dimensional pump-probe electronic spectroscopy is a powerful technique able to provide both high spectral and temporal resolution, allowing the analysis of ultrafast complex reactions occurring via complementary pathways by the identification of decay-specific fingerprints. [1-2] The understanding of the origin of the experimentally recorded signals in a two-dimensional electronic spectrum requires the characterization of the electronic states involved in the electronic transitions photoinduced by the pump/probe pulses in the experiment. Such a goal constitutes a considerable computational challenge, since up to 100 states need to be described, for which state-of-the-art methods as RASSCF and RASPT2 have to be wisely employed. [3] With the present contribution, the main features and potentialities of two-dimensional electronic spectroscopy are presented, together with the machinery in continuous development in our groups in order to compute two-dimensional electronic spectra. The results obtained using different level of theory and simulations are shown, bringing as examples the computed two-dimensional electronic spectra for some specific cases studied. [2-4] [1] Rivalta I, Nenov A, Cerullo G, Mukamel S, Garavelli M, Int. J. Quantum Chem., 2014, 114, 85 [2] Nenov A, Segarra-Martí J, Giussani A, Conti I, Rivalta I, Dumont E, Jaiswal V K, Altavilla S, Mukamel S, Garavelli M, Faraday Discuss. 2015, DOI: 10.1039/C4FD00175C [3] Nenov A, Giussani A, Segarra-Martí J, Jaiswal V K, Rivalta I, Cerullo G, Mukamel S, Garavelli M, J. Chem. Phys. submitted [4] Nenov A, Giussani A, Fingerhut B P, Rivalta I, Dumont E, Mukamel S, Garavelli M, Phys. Chem. Chem. Phys. Submitted [5] Krebs N, Pugliesi I, Hauer J, Riedle E, New J. Phys., 2013,15, 08501

  10. The FLUKA Code: An Accurate Simulation Tool for Particle Therapy

    PubMed Central

    Battistoni, Giuseppe; Bauer, Julia; Boehlen, Till T.; Cerutti, Francesco; Chin, Mary P. W.; Dos Santos Augusto, Ricardo; Ferrari, Alfredo; Ortega, Pablo G.; Kozłowska, Wioletta; Magro, Giuseppe; Mairani, Andrea; Parodi, Katia; Sala, Paola R.; Schoofs, Philippe; Tessonnier, Thomas; Vlachoudis, Vasilis

    2016-01-01

    Monte Carlo (MC) codes are increasingly spreading in the hadrontherapy community due to their detailed description of radiation transport and interaction with matter. The suitability of a MC code for application to hadrontherapy demands accurate and reliable physical models capable of handling all components of the expected radiation field. This becomes extremely important for correctly performing not only physical but also biologically based dose calculations, especially in cases where ions heavier than protons are involved. In addition, accurate prediction of emerging secondary radiation is of utmost importance in innovative areas of research aiming at in vivo treatment verification. This contribution will address the recent developments of the FLUKA MC code and its practical applications in this field. Refinements of the FLUKA nuclear models in the therapeutic energy interval lead to an improved description of the mixed radiation field as shown in the presented benchmarks against experimental data with both 4He and 12C ion beams. Accurate description of ionization energy losses and of particle scattering and interactions lead to the excellent agreement of calculated depth–dose profiles with those measured at leading European hadron therapy centers, both with proton and ion beams. In order to support the application of FLUKA in hospital-based environments, Flair, the FLUKA graphical interface, has been enhanced with the capability of translating CT DICOM images into voxel-based computational phantoms in a fast and well-structured way. The interface is capable of importing also radiotherapy treatment data described in DICOM RT standard. In addition, the interface is equipped with an intuitive PET scanner geometry generator and automatic recording of coincidence events. Clinically, similar cases will be presented both in terms of absorbed dose and biological dose calculations describing the various available features. PMID:27242956

  11. The FLUKA Code: An Accurate Simulation Tool for Particle Therapy.

    PubMed

    Battistoni, Giuseppe; Bauer, Julia; Boehlen, Till T; Cerutti, Francesco; Chin, Mary P W; Dos Santos Augusto, Ricardo; Ferrari, Alfredo; Ortega, Pablo G; Kozłowska, Wioletta; Magro, Giuseppe; Mairani, Andrea; Parodi, Katia; Sala, Paola R; Schoofs, Philippe; Tessonnier, Thomas; Vlachoudis, Vasilis

    2016-01-01

    Monte Carlo (MC) codes are increasingly spreading in the hadrontherapy community due to their detailed description of radiation transport and interaction with matter. The suitability of a MC code for application to hadrontherapy demands accurate and reliable physical models capable of handling all components of the expected radiation field. This becomes extremely important for correctly performing not only physical but also biologically based dose calculations, especially in cases where ions heavier than protons are involved. In addition, accurate prediction of emerging secondary radiation is of utmost importance in innovative areas of research aiming at in vivo treatment verification. This contribution will address the recent developments of the FLUKA MC code and its practical applications in this field. Refinements of the FLUKA nuclear models in the therapeutic energy interval lead to an improved description of the mixed radiation field as shown in the presented benchmarks against experimental data with both (4)He and (12)C ion beams. Accurate description of ionization energy losses and of particle scattering and interactions lead to the excellent agreement of calculated depth-dose profiles with those measured at leading European hadron therapy centers, both with proton and ion beams. In order to support the application of FLUKA in hospital-based environments, Flair, the FLUKA graphical interface, has been enhanced with the capability of translating CT DICOM images into voxel-based computational phantoms in a fast and well-structured way. The interface is capable of importing also radiotherapy treatment data described in DICOM RT standard. In addition, the interface is equipped with an intuitive PET scanner geometry generator and automatic recording of coincidence events. Clinically, similar cases will be presented both in terms of absorbed dose and biological dose calculations describing the various available features.

  12. A GPU tool for efficient, accurate, and realistic simulation of cone beam CT projections

    PubMed Central

    Jia, Xun; Yan, Hao; Cerviño, Laura; Folkerts, Michael; Jiang, Steve B.

    2012-01-01

    Purpose: Simulation of x-ray projection images plays an important role in cone beam CT (CBCT) related research projects, such as the design of reconstruction algorithms or scanners. A projection image contains primary signal, scatter signal, and noise. It is computationally demanding to perform accurate and realistic computations for all of these components. In this work, the authors develop a package on graphics processing unit (GPU), called gDRR, for the accurate and efficient computations of x-ray projection images in CBCT under clinically realistic conditions. Methods: The primary signal is computed by a trilinear ray-tracing algorithm. A Monte Carlo (MC) simulation is then performed, yielding the primary signal and the scatter signal, both with noise. A denoising process specifically designed for Poisson noise removal is applied to obtain a smooth scatter signal. The noise component is then obtained by combining the difference between the MC primary and the ray-tracing primary signals, and the difference between the MC simulated scatter and the denoised scatter signals. Finally, a calibration step converts the calculated noise signal into a realistic one by scaling its amplitude according to a specified mAs level. The computations of gDRR include a number of realistic features, e.g., a bowtie filter, a polyenergetic spectrum, and detector response. The implementation is fine-tuned for a GPU platform to yield high computational efficiency. Results: For a typical CBCT projection with a polyenergetic spectrum, the calculation time for the primary signal using the ray-tracing algorithms is 1.2–2.3 s, while the MC simulations take 28.1–95.3 s, depending on the voxel size. Computation time for all other steps is negligible. The ray-tracing primary signal matches well with the primary part of the MC simulation result. The MC simulated scatter signal using gDRR is in agreement with EGSnrc results with a relative difference of 3.8%. A noise calibration process is

  13. Accurate and precise determination of critical properties from Gibbs ensemble Monte Carlo simulations

    SciTech Connect

    Dinpajooh, Mohammadhasan; Bai, Peng; Allan, Douglas A.; Siepmann, J. Ilja

    2015-09-21

    Since the seminal paper by Panagiotopoulos [Mol. Phys. 61, 813 (1997)], the Gibbs ensemble Monte Carlo (GEMC) method has been the most popular particle-based simulation approach for the computation of vapor–liquid phase equilibria. However, the validity of GEMC simulations in the near-critical region has been questioned because rigorous finite-size scaling approaches cannot be applied to simulations with fluctuating volume. Valleau [Mol. Simul. 29, 627 (2003)] has argued that GEMC simulations would lead to a spurious overestimation of the critical temperature. More recently, Patel et al. [J. Chem. Phys. 134, 024101 (2011)] opined that the use of analytical tail corrections would be problematic in the near-critical region. To address these issues, we perform extensive GEMC simulations for Lennard-Jones particles in the near-critical region varying the system size, the overall system density, and the cutoff distance. For a system with N = 5500 particles, potential truncation at 8σ and analytical tail corrections, an extrapolation of GEMC simulation data at temperatures in the range from 1.27 to 1.305 yields T{sub c} = 1.3128 ± 0.0016, ρ{sub c} = 0.316 ± 0.004, and p{sub c} = 0.1274 ± 0.0013 in excellent agreement with the thermodynamic limit determined by Potoff and Panagiotopoulos [J. Chem. Phys. 109, 10914 (1998)] using grand canonical Monte Carlo simulations and finite-size scaling. Critical properties estimated using GEMC simulations with different overall system densities (0.296 ≤ ρ{sub t} ≤ 0.336) agree to within the statistical uncertainties. For simulations with tail corrections, data obtained using r{sub cut} = 3.5σ yield T{sub c} and p{sub c} that are higher by 0.2% and 1.4% than simulations with r{sub cut} = 5 and 8σ but still with overlapping 95% confidence intervals. In contrast, GEMC simulations with a truncated and shifted potential show that r{sub cut} = 8σ is insufficient to obtain accurate results. Additional GEMC simulations for hard

  14. Towards accurate quantum simulations of large systems with small computers

    NASA Astrophysics Data System (ADS)

    Yang, Yonggang

    2017-01-01

    Numerical simulations are important for many systems. In particular, various standard computer programs have been developed for solving the quantum Schrödinger equations. However, the accuracy of these calculations is limited by computer capabilities. In this work, an iterative method is introduced to enhance the accuracy of these numerical calculations, which is otherwise prohibitive by conventional methods. The method is easily implementable and general for many systems.

  15. Towards accurate quantum simulations of large systems with small computers.

    PubMed

    Yang, Yonggang

    2017-01-24

    Numerical simulations are important for many systems. In particular, various standard computer programs have been developed for solving the quantum Schrödinger equations. However, the accuracy of these calculations is limited by computer capabilities. In this work, an iterative method is introduced to enhance the accuracy of these numerical calculations, which is otherwise prohibitive by conventional methods. The method is easily implementable and general for many systems.

  16. Accurate, practical simulation of satellite infrared radiometer spectral data

    SciTech Connect

    Sullivan, T.J.

    1982-09-01

    This study's purpose is to determine whether a relatively simple random band model formulation of atmospheric radiation transfer in the infrared region can provide valid simulations of narrow interval satellite-borne infrared sounder system data. Detailed ozonesondes provide the pertinent atmospheric information and sets of calibrated satellite measurements provide the validation. High resolution line-by-line model calculations are included to complete the evaluation.

  17. Towards accurate quantum simulations of large systems with small computers

    PubMed Central

    Yang, Yonggang

    2017-01-01

    Numerical simulations are important for many systems. In particular, various standard computer programs have been developed for solving the quantum Schrödinger equations. However, the accuracy of these calculations is limited by computer capabilities. In this work, an iterative method is introduced to enhance the accuracy of these numerical calculations, which is otherwise prohibitive by conventional methods. The method is easily implementable and general for many systems. PMID:28117366

  18. Time Accurate CFD Simulations of the Orion Launch Abort Vehicle in the Transonic Regime

    NASA Technical Reports Server (NTRS)

    Ruf, Joseph; Rojahn, Josh

    2011-01-01

    Significant asymmetries in the fluid dynamics were calculated for some cases in the CFD simulations of the Orion Launch Abort Vehicle through its abort trajectories. The CFD simulations were performed steady state with symmetric boundary conditions and geometries. The trajectory points at issue were in the transonic regime, at 0 and 5 angles of attack with the Abort Motors with and without the Attitude Control Motors (ACM) firing. In some of the cases the asymmetric fluid dynamics resulted in aerodynamic side forces that were large enough that would overcome the control authority of the ACMs. MSFC s Fluid Dynamics Group supported the investigation into the cause of the flow asymmetries with time accurate CFD simulations, utilizing a hybrid RANS-LES turbulence model. The results show that the flow over the vehicle and the subsequent interaction with the AB and ACM motor plumes were unsteady. The resulting instantaneous aerodynamic forces were oscillatory with fairly large magnitudes. Time averaged aerodynamic forces were essentially symmetric.

  19. Efficient and accurate simulation of dynamic dielectric objects.

    PubMed

    Barros, Kipton; Sinkovits, Daniel; Luijten, Erik

    2014-02-14

    Electrostatic interactions between dielectric objects are complex and of a many-body nature, owing to induced surface bound charge. We present a collection of techniques to simulate dynamical dielectric objects. We calculate the surface bound charge from a matrix equation using the Generalized Minimal Residue method (GMRES). Empirically, we find that GMRES converges very quickly. Indeed, our detailed analysis suggests that the relevant matrix has a very compact spectrum for all non-degenerate dielectric geometries. Each GMRES iteration can be evaluated using a fast Ewald solver with cost that scales linearly or near-linearly in the number of surface charge elements. We analyze several previously proposed methods for calculating the bound charge, and show that our approach compares favorably.

  20. A hierarchical approach to accurate predictions of macroscopic thermodynamic behavior from quantum mechanics and molecular simulations

    NASA Astrophysics Data System (ADS)

    Garrison, Stephen L.

    2005-07-01

    The combination of molecular simulations and potentials obtained from quantum chemistry is shown to be able to provide reasonably accurate thermodynamic property predictions. Gibbs ensemble Monte Carlo simulations are used to understand the effects of small perturbations to various regions of the model Lennard-Jones 12-6 potential. However, when the phase behavior and second virial coefficient are scaled by the critical properties calculated for each potential, the results obey a corresponding states relation suggesting a non-uniqueness problem for interaction potentials fit to experimental phase behavior. Several variations of a procedure collectively referred to as quantum mechanical Hybrid Methods for Interaction Energies (HM-IE) are developed and used to accurately estimate interaction energies from CCSD(T) calculations with a large basis set in a computationally efficient manner for the neon-neon, acetylene-acetylene, and nitrogen-benzene systems. Using these results and methods, an ab initio, pairwise-additive, site-site potential for acetylene is determined and then improved using results from molecular simulations using this initial potential. The initial simulation results also indicate that a limited range of energies important for accurate phase behavior predictions. Second virial coefficients calculated from the improved potential indicate that one set of experimental data in the literature is likely erroneous. This prescription is then applied to methanethiol. Difficulties in modeling the effects of the lone pair electrons suggest that charges on the lone pair sites negatively impact the ability of the intermolecular potential to describe certain orientations, but that the lone pair sites may be necessary to reasonably duplicate the interaction energies for several orientations. Two possible methods for incorporating the effects of three-body interactions into simulations within the pairwise-additivity formulation are also developed. A low density

  1. Accurate and general treatment of electrostatic interaction in Hamiltonian adaptive resolution simulations

    NASA Astrophysics Data System (ADS)

    Heidari, M.; Cortes-Huerto, R.; Donadio, D.; Potestio, R.

    2016-10-01

    In adaptive resolution simulations the same system is concurrently modeled with different resolution in different subdomains of the simulation box, thereby enabling an accurate description in a small but relevant region, while the rest is treated with a computationally parsimonious model. In this framework, electrostatic interaction, whose accurate treatment is a crucial aspect in the realistic modeling of soft matter and biological systems, represents a particularly acute problem due to the intrinsic long-range nature of Coulomb potential. In the present work we propose and validate the usage of a short-range modification of Coulomb potential, the Damped shifted force (DSF) model, in the context of the Hamiltonian adaptive resolution simulation (H-AdResS) scheme. This approach, which is here validated on bulk water, ensures a reliable reproduction of the structural and dynamical properties of the liquid, and enables a seamless embedding in the H-AdResS framework. The resulting dual-resolution setup is implemented in the LAMMPS simulation package, and its customized version employed in the present work is made publicly available.

  2. Numerical simulations of catastrophic disruption: Recent results

    NASA Technical Reports Server (NTRS)

    Benz, W.; Asphaug, E.; Ryan, E. V.

    1994-01-01

    Numerical simulations have been used to study high velocity two-body impacts. In this paper, a two-dimensional Largrangian finite difference hydro-code and a three-dimensional smooth particle hydro-code (SPH) are described and initial results reported. These codes can be, and have been, used to make specific predictions about particular objects in our solar system. But more significantly, they allow us to explore a broad range of collisional events. Certain parameters (size, time) can be studied only over a very restricted range within the laboratory; other parameters (initial spin, low gravity, exotic structure or composition) are difficult to study at all experimentally. The outcomes of numerical simulations lead to a more general and accurate understanding of impacts in their many forms.

  3. Recommendations for Achieving Accurate Numerical Simulation of Tip Clearance Flows in Transonic Compressor Rotors

    NASA Technical Reports Server (NTRS)

    VanZante, Dale E.; Strazisar, Anthony J.; Wood, Jerry R,; Hathaway, Michael D.; Okiishi, Theodore H.

    2000-01-01

    The tip clearance flows of transonic compressor rotors are important because they have a significant impact on rotor and stage performance. While numerical simulations of these flows are quite sophisticated. they are seldom verified through rigorous comparisons of numerical and measured data because these kinds of measurements are rare in the detail necessary to be useful in high-speed machines. In this paper we compare measured tip clearance flow details (e.g. trajectory and radial extent) with corresponding data obtained from a numerical simulation. Recommendations for achieving accurate numerical simulation of tip clearance flows are presented based on this comparison. Laser Doppler Velocimeter (LDV) measurements acquired in a transonic compressor rotor, NASA Rotor 35, are used. The tip clearance flow field of this transonic rotor was simulated using a Navier-Stokes turbomachinery solver that incorporates an advanced k-epsilon turbulence model derived for flows that are not in local equilibrium. Comparison between measured and simulated results indicates that simulation accuracy is primarily dependent upon the ability of the numerical code to resolve important details of a wall-bounded shear layer formed by the relative motion between the over-tip leakage flow and the shroud wall. A simple method is presented for determining the strength of this shear layer.

  4. Body charge modelling for accurate simulation of small-signal behaviour in floating body SOI

    NASA Astrophysics Data System (ADS)

    Benson, James; Redman-White, William; D'Halleweyn, Nele V.; Easson, Craig A.; Uren, Michael J.

    2002-04-01

    We show that careful modelling of body node elements in floating body PD-SOI MOSFET compact models is required in order to obtain accurate small-signal simulation results in the saturation region. The body network modifies the saturation output conductance of the device via the body-source transconductance, resulting in a pole/zero pair being introduced in the conductance-frequency response. We show that neglecting the presence of body charge in the saturation region can often yield inaccurate values for the body capacitances, which in turn can adversely affect the modelling of the output conductance above the pole/zero frequency. We conclude that the underlying cause of this problem is the use of separate models for the intrinsic and extrinsic capacitances. Finally, we present a simple saturation body charge model which can greatly improve small-signal simulation accuracy for floating body devices.

  5. Fast and accurate MAS-DNP simulations of large spin ensembles.

    PubMed

    Mentink-Vigier, Frédéric; Vega, Shimon; De Paëpe, Gaël

    2017-02-01

    A deeper understanding of parameters affecting Magic Angle Spinning Dynamic Nuclear Polarization (MAS-DNP), an emerging nuclear magnetic resonance hyperpolarization method, is crucial for the development of new polarizing agents and the successful implementation of the technique at higher magnetic fields (>10 T). Such progress is currently impeded by computational limitation which prevents the simulation of large spin ensembles (electron as well as nuclear spins) and to accurately describe the interplay between all the multiple key parameters at play. In this work, we present an alternative approach to existing cross-effect and solid-effect MAS-DNP codes that yields fast and accurate simulations. More specifically we describe the model, the associated Liouville-based formalism (Bloch-type derivation and/or Landau-Zener approximations) and the linear time algorithm that allows computing MAS-DNP mechanisms with unprecedented time savings. As a result, one can easily scan through multiple parameters and disentangle their mutual influences. In addition, the simulation code is able to handle multiple electrons and protons, which allows probing the effect of (hyper)polarizing agents concentration, as well as fully revealing the interplay between the polarizing agent structure and the hyperfine couplings, nuclear dipolar couplings, nuclear relaxation times, both in terms of depolarization effect, but also of polarization gain and buildup times.

  6. Fast and accurate simulations of diffusion-weighted MRI signals for the evaluation of acquisition sequences

    NASA Astrophysics Data System (ADS)

    Rensonnet, Gaëtan; Jacobs, Damien; Macq, Benoît.; Taquet, Maxime

    2016-03-01

    Diffusion-weighted magnetic resonance imaging (DW-MRI) is a powerful tool to probe the diffusion of water through tissues. Through the application of magnetic gradients of appropriate direction, intensity and duration constituting the acquisition parameters, information can be retrieved about the underlying microstructural organization of the brain. In this context, an important and open question is to determine an optimal sequence of such acquisition parameters for a specific purpose. The use of simulated DW-MRI data for a given microstructural configuration provides a convenient and efficient way to address this problem. We first present a novel hybrid method for the synthetic simulation of DW-MRI signals that combines analytic expressions in simple geometries such as spheres and cylinders and Monte Carlo (MC) simulations elsewhere. Our hybrid method remains valid for any acquisition parameters and provides identical levels of accuracy with a computational time that is 90% shorter than that required by MC simulations for commonly-encountered microstructural configurations. We apply our novel simulation technique to estimate the radius of axons under various noise levels with different acquisition protocols commonly used in the literature. The results of our comparison suggest that protocols favoring a large number of gradient intensities such as a Cube and Sphere (CUSP) imaging provide more accurate radius estimation than conventional single-shell HARDI acquisitions for an identical acquisition time.

  7. Development of modified cable models to simulate accurate neuronal active behaviors

    PubMed Central

    2014-01-01

    In large network and single three-dimensional (3-D) neuron simulations, high computing speed dictates using reduced cable models to simulate neuronal firing behaviors. However, these models are unwarranted under active conditions and lack accurate representation of dendritic active conductances that greatly shape neuronal firing. Here, realistic 3-D (R3D) models (which contain full anatomical details of dendrites) of spinal motoneurons were systematically compared with their reduced single unbranched cable (SUC, which reduces the dendrites to a single electrically equivalent cable) counterpart under passive and active conditions. The SUC models matched the R3D model's passive properties but failed to match key active properties, especially active behaviors originating from dendrites. For instance, persistent inward currents (PIC) hysteresis, frequency-current (FI) relationship secondary range slope, firing hysteresis, plateau potential partial deactivation, staircase currents, synaptic current transfer ratio, and regional FI relationships were not accurately reproduced by the SUC models. The dendritic morphology oversimplification and lack of dendritic active conductances spatial segregation in the SUC models caused significant underestimation of those behaviors. Next, SUC models were modified by adding key branching features in an attempt to restore their active behaviors. The addition of primary dendritic branching only partially restored some active behaviors, whereas the addition of secondary dendritic branching restored most behaviors. Importantly, the proposed modified models successfully replicated the active properties without sacrificing model simplicity, making them attractive candidates for running R3D single neuron and network simulations with accurate firing behaviors. The present results indicate that using reduced models to examine PIC behaviors in spinal motoneurons is unwarranted. PMID:25277743

  8. A spectral element method with adaptive segmentation for accurately simulating extracellular electrical stimulation of neurons.

    PubMed

    Eiber, Calvin D; Dokos, Socrates; Lovell, Nigel H; Suaning, Gregg J

    2016-08-19

    The capacity to quickly and accurately simulate extracellular stimulation of neurons is essential to the design of next-generation neural prostheses. Existing platforms for simulating neurons are largely based on finite-difference techniques; due to the complex geometries involved, the more powerful spectral or differential quadrature techniques cannot be applied directly. This paper presents a mathematical basis for the application of a spectral element method to the problem of simulating the extracellular stimulation of retinal neurons, which is readily extensible to neural fibers of any kind. The activating function formalism is extended to arbitrary neuron geometries, and a segmentation method to guarantee an appropriate choice of collocation points is presented. Differential quadrature may then be applied to efficiently solve the resulting cable equations. The capacity for this model to simulate action potentials propagating through branching structures and to predict minimum extracellular stimulation thresholds for individual neurons is demonstrated. The presented model is validated against published values for extracellular stimulation threshold and conduction velocity for realistic physiological parameter values. This model suggests that convoluted axon geometries are more readily activated by extracellular stimulation than linear axon geometries, which may have ramifications for the design of neural prostheses.

  9. Time Accurate CFD Simulations of the Orion Launch Abort Vehicle in the Transonic Regime

    NASA Technical Reports Server (NTRS)

    Rojahn, Josh; Ruf, Joe

    2011-01-01

    Significant asymmetries in the fluid dynamics were calculated for some cases in the CFD simulations of the Orion Launch Abort Vehicle through its abort trajectories. The CFD simulations were performed steady state and in three dimensions with symmetric geometries, no freestream sideslip angle, and motors firing. The trajectory points at issue were in the transonic regime, at 0 and +/- 5 angles of attack with the Abort Motors with and without the Attitude Control Motors (ACM) firing. In some of the cases the asymmetric fluid dynamics resulted in aerodynamic side forces that were large enough that would overcome the control authority of the ACMs. MSFC's Fluid Dynamics Group supported the investigation into the cause of the flow asymmetries with time accurate CFD simulations, utilizing a hybrid RANS-LES turbulence model. The results show that the flow over the vehicle and the subsequent interaction with the AB and ACM motor plumes were unsteady. The resulting instantaneous aerodynamic forces were oscillatory with fairly large magnitudes. Time averaged aerodynamic forces were essentially symmetric.

  10. Accurate load prediction by BEM with airfoil data from 3D RANS simulations

    NASA Astrophysics Data System (ADS)

    Schneider, Marc S.; Nitzsche, Jens; Hennings, Holger

    2016-09-01

    In this paper, two methods for the extraction of airfoil coefficients from 3D CFD simulations of a wind turbine rotor are investigated, and these coefficients are used to improve the load prediction of a BEM code. The coefficients are extracted from a number of steady RANS simulations, using either averaging of velocities in annular sections, or an inverse BEM approach for determination of the induction factors in the rotor plane. It is shown that these 3D rotor polars are able to capture the rotational augmentation at the inner part of the blade as well as the load reduction by 3D effects close to the blade tip. They are used as input to a simple BEM code and the results of this BEM with 3D rotor polars are compared to the predictions of BEM with 2D airfoil coefficients plus common empirical corrections for stall delay and tip loss. While BEM with 2D airfoil coefficients produces a very different radial distribution of loads than the RANS simulation, the BEM with 3D rotor polars manages to reproduce the loads from RANS very accurately for a variety of load cases, as long as the blade pitch angle is not too different from the cases from which the polars were extracted.

  11. Hydration free energies of cyanide and hydroxide ions from molecular dynamics simulations with accurate force fields

    USGS Publications Warehouse

    Lee, M.W.; Meuwly, M.

    2013-01-01

    The evaluation of hydration free energies is a sensitive test to assess force fields used in atomistic simulations. We showed recently that the vibrational relaxation times, 1D- and 2D-infrared spectroscopies for CN(-) in water can be quantitatively described from molecular dynamics (MD) simulations with multipolar force fields and slightly enlarged van der Waals radii for the C- and N-atoms. To validate such an approach, the present work investigates the solvation free energy of cyanide in water using MD simulations with accurate multipolar electrostatics. It is found that larger van der Waals radii are indeed necessary to obtain results close to the experimental values when a multipolar force field is used. For CN(-), the van der Waals ranges refined in our previous work yield hydration free energy between -72.0 and -77.2 kcal mol(-1), which is in excellent agreement with the experimental data. In addition to the cyanide ion, we also study the hydroxide ion to show that the method used here is readily applicable to similar systems. Hydration free energies are found to sensitively depend on the intermolecular interactions, while bonded interactions are less important, as expected. We also investigate in the present work the possibility of applying the multipolar force field in scoring trajectories generated using computationally inexpensive methods, which should be useful in broader parametrization studies with reduced computational resources, as scoring is much faster than the generation of the trajectories.

  12. Time-Accurate Simulations and Acoustic Analysis of Slat Free-Shear Layer

    NASA Technical Reports Server (NTRS)

    Khorrami, Mehdi R.; Singer, Bart A.; Berkman, Mert E.

    2001-01-01

    A detailed computational aeroacoustic analysis of a high-lift flow field is performed. Time-accurate Reynolds Averaged Navier-Stokes (RANS) computations simulate the free shear layer that originates from the slat cusp. Both unforced and forced cases are studied. Preliminary results show that the shear layer is a good amplifier of disturbances in the low to mid-frequency range. The Ffowcs-Williams and Hawkings equation is solved to determine the acoustic field using the unsteady flow data from the RANS calculations. The noise radiated from the excited shear layer has a spectral shape qualitatively similar to that obtained from measurements in a corresponding experimental study of the high-lift system.

  13. Object-Oriented NeuroSys: Parallel Programs for Simulating Large Networks of Biologically Accurate Neurons

    SciTech Connect

    Pacheco, P; Miller, P; Kim, J; Leese, T; Zabiyaka, Y

    2003-05-07

    Object-oriented NeuroSys (ooNeuroSys) is a collection of programs for simulating very large networks of biologically accurate neurons on distributed memory parallel computers. It includes two principle programs: ooNeuroSys, a parallel program for solving the large systems of ordinary differential equations arising from the interconnected neurons, and Neurondiz, a parallel program for visualizing the results of ooNeuroSys. Both programs are designed to be run on clusters and use the MPI library to obtain parallelism. ooNeuroSys also includes an easy-to-use Python interface. This interface allows neuroscientists to quickly develop and test complex neuron models. Both ooNeuroSys and Neurondiz have a design that allows for both high performance and relative ease of maintenance.

  14. Importance of accurate spectral simulations for the analysis of terahertz spectra: citric acid anhydrate and monohydrate.

    PubMed

    King, Matthew D; Davis, Eric A; Smith, Tiffany M; Korter, Timothy M

    2011-10-13

    The terahertz (THz) spectra of crystalline solids are typically uniquely sensitive to the molecular packing configurations, allowing for the detection of polymorphs and hydrates by THz spectroscopic techniques. It is possible, however, that coincident absorptions may be observed between related crystal forms, in which case careful assessment of the lattice vibrations of each system must be performed. Presented here is a THz spectroscopic investigation of citric acid in its anhydrous and monohydrate phases. Remarkably similar features were observed in the THz spectra of both systems, requiring the accurate calculation of the low-frequency vibrational modes by solid-state density functional theory to determine the origins of these spectral features. The results of the simulations demonstrate the necessity of reliable and rigorous methods for THz vibrational modes to ensure the proper evaluation of the THz spectra of molecular solids.

  15. Time-Accurate Computational Fluid Dynamics Simulation of a Pair of Moving Solid Rocket Boosters

    NASA Technical Reports Server (NTRS)

    Strutzenberg, Louise L.; Williams, Brandon R.

    2011-01-01

    Since the Columbia accident, the threat to the Shuttle launch vehicle from debris during the liftoff timeframe has been assessed by the Liftoff Debris Team at NASA/MSFC. In addition to engineering methods of analysis, CFD-generated flow fields during the liftoff timeframe have been used in conjunction with 3-DOF debris transport methods to predict the motion of liftoff debris. Early models made use of a quasi-steady flow field approximation with the vehicle positioned at a fixed location relative to the ground; however, a moving overset mesh capability has recently been developed for the Loci/CHEM CFD software which enables higher-fidelity simulation of the Shuttle transient plume startup and liftoff environment. The present work details the simulation of the launch pad and mobile launch platform (MLP) with truncated solid rocket boosters (SRBs) moving in a prescribed liftoff trajectory derived from Shuttle flight measurements. Using Loci/CHEM, time-accurate RANS and hybrid RANS/LES simulations were performed for the timeframe T0+0 to T0+3.5 seconds, which consists of SRB startup to a vehicle altitude of approximately 90 feet above the MLP. Analysis of the transient flowfield focuses on the evolution of the SRB plumes in the MLP plume holes and the flame trench, impingement on the flame deflector, and especially impingment on the MLP deck resulting in upward flow which is a transport mechanism for debris. The results show excellent qualitative agreement with the visual record from past Shuttle flights, and comparisons to pressure measurements in the flame trench and on the MLP provide confidence in these simulation capabilities.

  16. Time Accurate Unsteady Pressure Loads Simulated for the Space Launch System at a Wind Tunnel Condition

    NASA Technical Reports Server (NTRS)

    Alter, Stephen J.; Brauckmann, Gregory J.; Kleb, Bil; Streett, Craig L; Glass, Christopher E.; Schuster, David M.

    2015-01-01

    Using the Fully Unstructured Three-Dimensional (FUN3D) computational fluid dynamics code, an unsteady, time-accurate flow field about a Space Launch System configuration was simulated at a transonic wind tunnel condition (Mach = 0.9). Delayed detached eddy simulation combined with Reynolds Averaged Naiver-Stokes and a Spallart-Almaras turbulence model were employed for the simulation. Second order accurate time evolution scheme was used to simulate the flow field, with a minimum of 0.2 seconds of simulated time to as much as 1.4 seconds. Data was collected at 480 pressure taps at locations, 139 of which matched a 3% wind tunnel model, tested in the Transonic Dynamic Tunnel (TDT) facility at NASA Langley Research Center. Comparisons between computation and experiment showed agreement within 5% in terms of location for peak RMS levels, and 20% for frequency and magnitude of power spectral densities. Grid resolution and time step sensitivity studies were performed to identify methods for improved accuracy comparisons to wind tunnel data. With limited computational resources, accurate trends for reduced vibratory loads on the vehicle were observed. Exploratory methods such as determining minimized computed errors based on CFL number and sub-iterations, as well as evaluating frequency content of the unsteady pressures and evaluation of oscillatory shock structures were used in this study to enhance computational efficiency and solution accuracy. These techniques enabled development of a set of best practices, for the evaluation of future flight vehicle designs in terms of vibratory loads.

  17. Accurate simulation of transient landscape evolution by eliminating numerical diffusion: the TTLEM 1.0 model

    NASA Astrophysics Data System (ADS)

    Campforts, Benjamin; Schwanghart, Wolfgang; Govers, Gerard

    2017-01-01

    Landscape evolution models (LEMs) allow the study of earth surface responses to changing climatic and tectonic forcings. While much effort has been devoted to the development of LEMs that simulate a wide range of processes, the numerical accuracy of these models has received less attention. Most LEMs use first-order accurate numerical methods that suffer from substantial numerical diffusion. Numerical diffusion particularly affects the solution of the advection equation and thus the simulation of retreating landforms such as cliffs and river knickpoints. This has potential consequences for the integrated response of the simulated landscape. Here we test a higher-order flux-limiting finite volume method that is total variation diminishing (TVD-FVM) to solve the partial differential equations of river incision and tectonic displacement. We show that using the TVD-FVM to simulate river incision significantly influences the evolution of simulated landscapes and the spatial and temporal variability of catchment-wide erosion rates. Furthermore, a two-dimensional TVD-FVM accurately simulates the evolution of landscapes affected by lateral tectonic displacement, a process whose simulation was hitherto largely limited to LEMs with flexible spatial discretization. We implement the scheme in TTLEM (TopoToolbox Landscape Evolution Model), a spatially explicit, raster-based LEM for the study of fluvially eroding landscapes in TopoToolbox 2.

  18. ILT based defect simulation of inspection images accurately predicts mask defect printability on wafer

    NASA Astrophysics Data System (ADS)

    Deep, Prakash; Paninjath, Sankaranarayanan; Pereira, Mark; Buck, Peter

    2016-05-01

    printability of defects at wafer level and automates the process of defect dispositioning from images captured using high resolution inspection machine. It first eliminates false defects due to registration, focus errors, image capture errors and random noise caused during inspection. For the remaining real defects, actual mask-like contours are generated using the Calibre® ILT solution [1][2], which is enhanced to predict the actual mask contours from high resolution defect images. It enables accurate prediction of defect contours, which is not possible from images captured using inspection machine because some information is already lost due to optical effects. Calibre's simulation engine is used to generate images at wafer level using scanner optical conditions and mask-like contours as input. The tool then analyses simulated images and predicts defect printability. It automatically calculates maximum CD variation and decides which defects are severe to affect patterns on wafer. In this paper, we assess the printability of defects for the mask of advanced technology nodes. In particular, we will compare the recovered mask contours with contours extracted from SEM image of the mask and compare simulation results with AIMSTM for a variety of defects and patterns. The results of printability assessment and the accuracy of comparison are presented in this paper. We also suggest how this method can be extended to predict printability of defects identified on EUV photomasks.

  19. ACCURATE SIMULATIONS OF BINARY BLACK HOLE MERGERS IN FORCE-FREE ELECTRODYNAMICS

    SciTech Connect

    Alic, Daniela; Moesta, Philipp; Rezzolla, Luciano; Jaramillo, Jose Luis; Zanotti, Olindo

    2012-07-20

    We provide additional information on our recent study of the electromagnetic emission produced during the inspiral and merger of supermassive black holes when these are immersed in a force-free plasma threaded by a uniform magnetic field. As anticipated in a recent letter, our results show that although a dual-jet structure is present, the associated luminosity is {approx}100 times smaller than the total one, which is predominantly quadrupolar. Here we discuss the details of our implementation of the equations in which the force-free condition is not implemented at a discrete level, but rather obtained via a damping scheme which drives the solution to satisfy the correct condition. We show that this is important for a correct and accurate description of the current sheets that can develop in the course of the simulation. We also study in greater detail the three-dimensional charge distribution produced as a consequence of the inspiral and show that during the inspiral it possesses a complex but ordered structure which traces the motion of the two black holes. Finally, we provide quantitative estimates of the scaling of the electromagnetic emission with frequency, with the diffused part having a dependence that is the same as the gravitational-wave one and that scales as L{sup non-coll}{sub EM} Almost-Equal-To {Omega}{sup 10/3-8/3}, while the collimated one scales as L{sup coll}{sub EM} Almost-Equal-To {Omega}{sup 5/3-6/3}, thus with a steeper dependence than previously estimated. We discuss the impact of these results on the potential detectability of dual jets from supermassive black holes and the steps necessary for more accurate estimates.

  20. Can a Global Model Accurately Simulate Land-Atmosphere Interactions under Climate Change Conditions?

    NASA Astrophysics Data System (ADS)

    Zhou, C., VI; Wang, K.

    2015-12-01

    Surface air temperature (Ta) is largely determined by surface net radiation (Rn) and its partitioning into latent (LE) and sensible heat fluxes (H). Existing model evaluations of the absolute values of these fluxes are less helpful because the evaluation results are a blending of inconsistent spatial scales, inaccurate model forcing data and inaccurate parameterizations. This study further evaluates the relationship of LE and H with Rn and environmental parameters, including Ta, relative humidity (RH) and wind speed (WS), using ERA-interim reanalysis data at a grid of 0.125°×0.125° with measurements at AmeriFlux sites from 1998 to 2012. The results demonstrate that ERA-Interim can reproduce the absolute values of environmental parameters, radiation and turbulent fluxes rather accurately. The model performs well in simulating the correlation of LE and H to Rn, except for the notable correlation overestimation of H against Rn over high-density vegetation (e.g., deciduous broadleaf forest (DBF), grassland (GRA) and cropland (CRO)). The sensitivity of LE to Rn in the model is similar to the observations, but that of H to Rn is overestimated by 24.2%. In regions with high-density vegetation, the correlation coefficient between H and Ta is overestimated by more than 0.2, whereas that between H and WS is underestimated by more than 0.43. The sensitivity of H to Ta is overestimated by 0.72 Wm-2 °C-1, whereas that of H to WS in the model is underestimated by 16.15 Wm-2/(ms-1) over all of the sites. Considering both LE and H, the model cannot accurately capture the response of the evaporative fraction (EF=LE/(LE+H)) to Rn and the environmental parameters.

  1. A mechanistic approach for accurate simulation of village scale malaria transmission

    PubMed Central

    Bomblies, Arne; Duchemin, Jean-Bernard; Eltahir, Elfatih AB

    2009-01-01

    Background Malaria transmission models commonly incorporate spatial environmental and climate variability for making regional predictions of disease risk. However, a mismatch of these models' typical spatial resolutions and the characteristic scale of malaria vector population dynamics may confound disease risk predictions in areas of high spatial hydrological variability such as the Sahel region of Africa. Methods Field observations spanning two years from two Niger villages are compared. The two villages are separated by only 30 km but exhibit a ten-fold difference in anopheles mosquito density. These two villages would be covered by a single grid cell in many malaria models, yet their entomological activity differs greatly. Environmental conditions and associated entomological activity are simulated at high spatial- and temporal resolution using a mechanistic approach that couples a distributed hydrology scheme and an entomological model. Model results are compared to regular field observations of Anopheles gambiae sensu lato mosquito populations and local hydrology. The model resolves the formation and persistence of individual pools that facilitate mosquito breeding and predicts spatio-temporal mosquito population variability at high resolution using an agent-based modeling approach. Results Observations of soil moisture, pool size, and pool persistence are reproduced by the model. The resulting breeding of mosquitoes in the simulated pools yields time-integrated seasonal mosquito population dynamics that closely follow observations from captured mosquito abundance. Interannual difference in mosquito abundance is simulated, and the inter-village difference in mosquito population is reproduced for two years of observations. These modeling results emulate the known focal nature of malaria in Niger Sahel villages. Conclusion Hydrological variability must be represented at high spatial and temporal resolution to achieve accurate predictive ability of malaria risk

  2. CgWind: A high-order accurate simulation tool for wind turbines and wind farms

    SciTech Connect

    Chand, K K; Henshaw, W D; Lundquist, K A; Singer, M A

    2010-02-22

    CgWind is a high-fidelity large eddy simulation (LES) tool designed to meet the modeling needs of wind turbine and wind park engineers. This tool combines several advanced computational technologies in order to model accurately the complex and dynamic nature of wind energy applications. The composite grid approach provides high-quality structured grids for the efficient implementation of high-order accurate discretizations of the incompressible Navier-Stokes equations. Composite grids also provide a natural mechanism for modeling bodies in relative motion and complex geometry. Advanced algorithms such as matrix-free multigrid, compact discretizations and approximate factorization will allow CgWind to perform highly resolved calculations efficiently on a wide class of computing resources. Also in development are nonlinear LES subgrid-scale models required to simulate the many interacting scales present in large wind turbine applications. This paper outlines our approach, the current status of CgWind and future development plans.

  3. Computer simulation results of attitude estimation of earth orbiting satellites

    NASA Technical Reports Server (NTRS)

    Kou, S. R.

    1976-01-01

    Computer simulation results of attitude estimation of Earth-orbiting satellites (including Space Telescope) subjected to environmental disturbances and noises are presented. Decomposed linear recursive filter and Kalman filter were used as estimation tools. Six programs were developed for this simulation, and all were written in the basic language and were run on HP 9830A and HP 9866A computers. Simulation results show that a decomposed linear recursive filter is accurate in estimation and fast in response time. Furthermore, for higher order systems, this filter has computational advantages (i.e., less integration errors and roundoff errors) over a Kalman filter.

  4. Time-Accurate Simulations and Acoustic Analysis of Slat Free-Shear-Layer. Part 2

    NASA Technical Reports Server (NTRS)

    Khorrami, Mehdi R.; Singer, Bart A.; Lockard, David P.

    2002-01-01

    Unsteady computational simulations of a multi-element, high-lift configuration are performed. Emphasis is placed on accurate spatiotemporal resolution of the free shear layer in the slat-cove region. The excessive dissipative effects of the turbulence model, so prevalent in previous simulations, are circumvented by switching off the turbulence-production term in the slat cove region. The justifications and physical arguments for taking such a step are explained in detail. The removal of this excess damping allows the shear layer to amplify large-scale structures, to achieve a proper non-linear saturation state, and to permit vortex merging. The large-scale disturbances are self-excited, and unlike our prior fully turbulent simulations, no external forcing of the shear layer is required. To obtain the farfield acoustics, the Ffowcs Williams and Hawkings equation is evaluated numerically using the simulated time-accurate flow data. The present comparison between the computed and measured farfield acoustic spectra shows much better agreement for the amplitude and frequency content than past calculations. The effect of the angle-of-attack on the slat's flow features radiated acoustic field are also simulated presented.

  5. Can a Rescuer or Simulated Patient Accurately Assess Motion During Cervical Spine Stabilization Practice Sessions?

    PubMed Central

    Shrier, Ian; Boissy, Patrick; Brière, Simon; Mellette, Jay; Fecteau, Luc; Matheson, Gordon O.; Garza, Daniel; Meeuwisse, Willem H.; Segal, Eli; Boulay, John; Steele, Russell J.

    2012-01-01

    Context: Health care providers must be prepared to manage all potential spine injuries as if they are unstable. Therefore, most sport teams devote resources to training for sideline cervical spine (C-spine) emergencies. Objective: To determine (1) how accurately rescuers and simulated patients can assess motion during C-spine stabilization practice and (2) whether providing performance feedback to rescuers influences their choice of stabilization technique. Design: Crossover study. Setting: Training studio. Patients or Other Participants: Athletic trainers, athletic therapists, and physiotherapists experienced at managing suspected C-spine injuries. Intervention(s): Twelve lead rescuers (at the patient's head) performed both the head-squeeze and trap-squeeze C-spine stabilization maneuvers during 4 test scenarios: lift-and-slide and log-roll placement on a spine board and confused patient trying to sit up or rotate the head. Main Outcome Measure(s): Interrater reliability between rescuer and simulated patient quality scores for subjective evaluation of C-spine stabilization during trials (0 = best, 10 = worst), correlation between rescuers' quality scores and objective measures of motion with inertial measurement units, and frequency of change in preference for the head-squeeze versus trap-squeeze maneuver. Results: Although the weighted κ value for interrater reliability was acceptable (0.71–0.74), scores varied by 2 points or more between rescuers and simulated patients for approximately 10% to 15% of trials. Rescuers' scores correlated with objective measures, but variability was large: 38% of trials scored as 0 or 1 by the rescuer involved more than 10° of motion in at least 1 direction. Feedback did not affect the preference for the lift-and-slide placement. For the log-roll placement, 6 of 8 participants who preferred the head squeeze at baseline preferred the trap squeeze after feedback. For the confused patient, 5 of 5 participants initially preferred

  6. A Three Dimensional Parallel Time Accurate Turbopump Simulation Procedure Using Overset Grid Systems

    NASA Technical Reports Server (NTRS)

    Kiris, Cetin; Chan, William; Kwak, Dochan

    2001-01-01

    The objective of the current effort is to provide a computational framework for design and analysis of the entire fuel supply system of a liquid rocket engine, including high-fidelity unsteady turbopump flow analysis. This capability is needed to support the design of pump sub-systems for advanced space transportation vehicles that are likely to involve liquid propulsion systems. To date, computational tools for design/analysis of turbopump flows are based on relatively lower fidelity methods. An unsteady, three-dimensional viscous flow analysis tool involving stationary and rotational components for the entire turbopump assembly has not been available for real-world engineering applications. The present effort provides developers with information such as transient flow phenomena at start up, and non-uniform inflows, and will eventually impact on system vibration and structures. In the proposed paper, the progress toward the capability of complete simulation of the turbo-pump for a liquid rocket engine is reported. The Space Shuttle Main Engine (SSME) turbo-pump is used as a test case for evaluation of the hybrid MPI/Open-MP and MLP versions of the INS3D code. CAD to solution auto-scripting capability is being developed for turbopump applications. The relative motion of the grid systems for the rotor-stator interaction was obtained using overset grid techniques. Unsteady computations for the SSME turbo-pump, which contains 114 zones with 34.5 million grid points, are carried out on Origin 3000 systems at NASA Ames Research Center. Results from these time-accurate simulations with moving boundary capability will be presented along with the performance of parallel versions of the code.

  7. A Three-Dimensional Parallel Time-Accurate Turbopump Simulation Procedure Using Overset Grid System

    NASA Technical Reports Server (NTRS)

    Kiris, Cetin; Chan, William; Kwak, Dochan

    2002-01-01

    The objective of the current effort is to provide a computational framework for design and analysis of the entire fuel supply system of a liquid rocket engine, including high-fidelity unsteady turbopump flow analysis. This capability is needed to support the design of pump sub-systems for advanced space transportation vehicles that are likely to involve liquid propulsion systems. To date, computational tools for design/analysis of turbopump flows are based on relatively lower fidelity methods. An unsteady, three-dimensional viscous flow analysis tool involving stationary and rotational components for the entire turbopump assembly has not been available for real-world engineering applications. The present effort provides developers with information such as transient flow phenomena at start up, and nonuniform inflows, and will eventually impact on system vibration and structures. In the proposed paper, the progress toward the capability of complete simulation of the turbo-pump for a liquid rocket engine is reported. The Space Shuttle Main Engine (SSME) turbo-pump is used as a test case for evaluation of the hybrid MPI/Open-MP and MLP versions of the INS3D code. CAD to solution auto-scripting capability is being developed for turbopump applications. The relative motion of the grid systems for the rotor-stator interaction was obtained using overset grid techniques. Unsteady computations for the SSME turbo-pump, which contains 114 zones with 34.5 million grid points, are carried out on Origin 3000 systems at NASA Ames Research Center. Results from these time-accurate simulations with moving boundary capability are presented along with the performance of parallel versions of the code.

  8. How accurate is the Pearson r-from-Z approximation? A Monte Carlo simulation study.

    PubMed

    Hittner, James B; May, Kim

    2012-01-01

    The Pearson r-from-Z approximation estimates the sample correlation (as an effect size measure) from the ratio of two quantities: the standard normal deviate equivalent (Z-score) corresponding to a one-tailed p-value divided by the square root of the total (pooled) sample size. The formula has utility in meta-analytic work when reports of research contain minimal statistical information. Although simple to implement, the accuracy of the Pearson r-from-Z approximation has not been empirically evaluated. To address this omission, we performed a series of Monte Carlo simulations. Results indicated that in some cases the formula did accurately estimate the sample correlation. However, when sample size was very small (N = 10) and effect sizes were small to small-moderate (ds of 0.1 and 0.3), the Pearson r-from-Z approximation was very inaccurate. Detailed figures that provide guidance as to when the Pearson r-from-Z formula will likely yield valid inferences are presented.

  9. An Accurate Heading Solution using MEMS-based Gyroscope and Magnetometer Integrated System (Preliminary Results)

    NASA Astrophysics Data System (ADS)

    El-Diasty, M.

    2014-11-01

    An accurate heading solution is required for many applications and it can be achieved by high grade (high cost) gyroscopes (gyros) which may not be suitable for such applications. Micro-Electro Mechanical Systems-based (MEMS) is an emerging technology, which has the potential of providing heading solution using a low cost MEMS-based gyro. However, MEMS-gyro-based heading solution drifts significantly over time. The heading solution can also be estimated using MEMS-based magnetometer by measuring the horizontal components of the Earth magnetic field. The MEMS-magnetometer-based heading solution does not drift over time, but are contaminated by high level of noise and may be disturbed by the presence of magnetic field sources such as metal objects. This paper proposed an accurate heading estimation procedure based on the integration of MEMS-based gyro and magnetometer measurements that correct gyro and magnetometer measurements where gyro angular rates of changes are estimated using magnetometer measurements and then integrated with the measured gyro angular rates of changes with a robust filter to estimate the heading. The proposed integration solution is implemented using two data sets; one was conducted in static mode without magnetic disturbances and the second was conducted in kinematic mode with magnetic disturbances. The results showed that the proposed integrated heading solution provides accurate, smoothed and undisturbed solution when compared with magnetometerbased and gyro-based heading solutions.

  10. Accurate and efficient halo-based galaxy clustering modelling with simulations

    NASA Astrophysics Data System (ADS)

    Zheng, Zheng; Guo, Hong

    2016-06-01

    Small- and intermediate-scale galaxy clustering can be used to establish the galaxy-halo connection to study galaxy formation and evolution and to tighten constraints on cosmological parameters. With the increasing precision of galaxy clustering measurements from ongoing and forthcoming large galaxy surveys, accurate models are required to interpret the data and extract relevant information. We introduce a method based on high-resolution N-body simulations to accurately and efficiently model the galaxy two-point correlation functions (2PCFs) in projected and redshift spaces. The basic idea is to tabulate all information of haloes in the simulations necessary for computing the galaxy 2PCFs within the framework of halo occupation distribution or conditional luminosity function. It is equivalent to populating galaxies to dark matter haloes and using the mock 2PCF measurements as the model predictions. Besides the accurate 2PCF calculations, the method is also fast and therefore enables an efficient exploration of the parameter space. As an example of the method, we decompose the redshift-space galaxy 2PCF into different components based on the type of galaxy pairs and show the redshift-space distortion effect in each component. The generalizations and limitations of the method are discussed.

  11. Advanced numerical techniques for accurate unsteady simulations of a wingtip vortex

    NASA Astrophysics Data System (ADS)

    Ahmad, Shakeel

    A numerical technique is developed to simulate the vortices associated with stationary and flapping wings. The Unsteady Reynolds-Averaged Navier-Stokes (URANS) equations are used over an unstructured grid. The present work assesses the locations of the origins of vortex generation, models those locations and develops a systematic mesh refinement strategy to simulate vortices more accurately using the URANS model. The vortex center plays a key role in the analysis of the simulation data. A novel approach to locating a vortex center is also developed referred to as the Max-Max criterion. Experimental validation of the simulated vortex from a stationary NACA0012 wing is achieved. The tangential velocity along the core of the vortex falls within five percent of the experimental data in the case of the stationary NACA0012 simulation. The wing surface pressure coefficient also matches with the experimental data. The refinement techniques are then focused on unsteady simulations of pitching and dual-mode wing flapping. Tip vortex strength, location, and wing surface pressure are analyzed. Links to vortex behavior and wing motion are inferred. Key words: vortex, tangential velocity, Cp, vortical flow, unsteady vortices, URANS, Max-Max, Vortex center

  12. Optimization of sample preparation for accurate results in quantitative NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Yamazaki, Taichi; Nakamura, Satoe; Saito, Takeshi

    2017-04-01

    Quantitative nuclear magnetic resonance (qNMR) spectroscopy has received high marks as an excellent measurement tool that does not require the same reference standard as the analyte. Measurement parameters have been discussed in detail and high-resolution balances have been used for sample preparation. However, the high-resolution balances, such as an ultra-microbalance, are not general-purpose analytical tools and many analysts may find those balances difficult to use, thereby hindering accurate sample preparation for qNMR measurement. In this study, we examined the relationship between the resolution of the balance and the amount of sample weighed during sample preparation. We were able to confirm the accuracy of the assay results for samples weighed on a high-resolution balance, such as the ultra-microbalance. Furthermore, when an appropriate tare and amount of sample was weighed on a given balance, accurate assay results were obtained with another high-resolution balance. Although this is a fundamental result, it offers important evidence that would enhance the versatility of the qNMR method.

  13. Milestone M4900: Simulant Mixing Analytical Results

    SciTech Connect

    Kaplan, D.I.

    2001-07-26

    This report addresses Milestone M4900, ''Simulant Mixing Sample Analysis Results,'' and contains the data generated during the ''Mixing of Process Heels, Process Solutions, and Recycle Streams: Small-Scale Simulant'' task. The Task Technical and Quality Assurance Plan for this task is BNF-003-98-0079A. A report with a narrative description and discussion of the data will be issued separately.

  14. Physical and Numerical Model Studies of Cross-flow Turbines Towards Accurate Parameterization in Array Simulations

    NASA Astrophysics Data System (ADS)

    Wosnik, M.; Bachant, P.

    2014-12-01

    Cross-flow turbines, often referred to as vertical-axis turbines, show potential for success in marine hydrokinetic (MHK) and wind energy applications, ranging from small- to utility-scale installations in tidal/ocean currents and offshore wind. As turbine designs mature, the research focus is shifting from individual devices to the optimization of turbine arrays. It would be expensive and time-consuming to conduct physical model studies of large arrays at large model scales (to achieve sufficiently high Reynolds numbers), and hence numerical techniques are generally better suited to explore the array design parameter space. However, since the computing power available today is not sufficient to conduct simulations of the flow in and around large arrays of turbines with fully resolved turbine geometries (e.g., grid resolution into the viscous sublayer on turbine blades), the turbines' interaction with the energy resource (water current or wind) needs to be parameterized, or modeled. Models used today--a common model is the actuator disk concept--are not able to predict the unique wake structure generated by cross-flow turbines. This wake structure has been shown to create "constructive" interference in some cases, improving turbine performance in array configurations, in contrast with axial-flow, or horizontal axis devices. Towards a more accurate parameterization of cross-flow turbines, an extensive experimental study was carried out using a high-resolution turbine test bed with wake measurement capability in a large cross-section tow tank. The experimental results were then "interpolated" using high-fidelity Navier--Stokes simulations, to gain insight into the turbine's near-wake. The study was designed to achieve sufficiently high Reynolds numbers for the results to be Reynolds number independent with respect to turbine performance and wake statistics, such that they can be reliably extrapolated to full scale and used for model validation. The end product of

  15. Metal cutting simulation of 4340 steel using an accurate mechanical description of meterial strength and fracture

    SciTech Connect

    Maudlin, P.J.; Stout, M.G.

    1996-09-01

    Strength and fracture constitutive relationships containing strain rate dependence and thermal softening are important for accurate simulation of metal cutting. The mechanical behavior of a hardened 4340 steel was characterized using the von Mises yield function, the Mechanical Threshold Stress model and the Johnson- Cook fracture model. This constitutive description was implemented into the explicit Lagrangian FEM continuum-mechanics code EPIC, and orthogonal plane-strain metal cutting calculations were performed. Heat conduction and friction at the toolwork-piece interface were included in the simulations. These transient calculations were advanced in time until steady state machining behavior (force) was realized. Experimental cutting force data (cutting and thrust forces) were measured for a planning operation and compared to the calculations. 13 refs., 6 figs.

  16. Canonical Decomposition of Ictal Scalp EEG and Accurate Source Localisation: Principles and Simulation Study

    PubMed Central

    De Vos, Maarten; De Lathauwer, Lieven; Vanrumste, Bart; Van Huffel, Sabine; Van Paesschen, W.

    2007-01-01

    Long-term electroencephalographic (EEG) recordings are important in the presurgical evaluation of refractory partial epilepsy for the delineation of the ictal onset zones. In this paper, we introduce a new concept for an automatic, fast, and objective localisation of the ictal onset zone in ictal EEG recordings. Canonical decomposition of ictal EEG decomposes the EEG in atoms. One or more atoms are related to the seizure activity. A single dipole was then fitted to model the potential distribution of each epileptic atom. In this study, we performed a simulation study in order to estimate the dipole localisation error. Ictal dipole localisation was very accurate, even at low signal-to-noise ratios, was not affected by seizure activity frequency or frequency changes, and was minimally affected by the waveform and depth of the ictal onset zone location. Ictal dipole localisation error using 21 electrodes was around 10.0 mm and improved more than tenfold in the range of 0.5–1.0 mm using 148 channels. In conclusion, our simulation study of canonical decomposition of ictal scalp EEG allowed a robust and accurate localisation of the ictal onset zone. PMID:18301715

  17. Time-Accurate Unsteady Pressure Loads Simulated for the Space Launch System at Wind Tunnel Conditions

    NASA Technical Reports Server (NTRS)

    Alter, Stephen J.; Brauckmann, Gregory J.; Kleb, William L.; Glass, Christopher E.; Streett, Craig L.; Schuster, David M.

    2015-01-01

    A transonic flow field about a Space Launch System (SLS) configuration was simulated with the Fully Unstructured Three-Dimensional (FUN3D) computational fluid dynamics (CFD) code at wind tunnel conditions. Unsteady, time-accurate computations were performed using second-order Delayed Detached Eddy Simulation (DDES) for up to 1.5 physical seconds. The surface pressure time history was collected at 619 locations, 169 of which matched locations on a 2.5 percent wind tunnel model that was tested in the 11 ft. x 11 ft. test section of the NASA Ames Research Center's Unitary Plan Wind Tunnel. Comparisons between computation and experiment showed that the peak surface pressure RMS level occurs behind the forward attach hardware, and good agreement for frequency and power was obtained in this region. Computational domain, grid resolution, and time step sensitivity studies were performed. These included an investigation of pseudo-time sub-iteration convergence. Using these sensitivity studies and experimental data comparisons, a set of best practices to date have been established for FUN3D simulations for SLS launch vehicle analysis. To the author's knowledge, this is the first time DDES has been used in a systematic approach and establish simulation time needed, to analyze unsteady pressure loads on a space launch vehicle such as the NASA SLS.

  18. Accurate boundary treatments for lattice Boltzmann simulations of electric fields and electro-kinetic applications

    NASA Astrophysics Data System (ADS)

    Oulaid, Othmane; Chen, Qing; Zhang, Junfeng

    2013-11-01

    In this paper a novel boundary method is proposed for lattice Boltzmann simulations of electric potential fields with complex boundary shapes and conditions. A shifted boundary from the physical surface location is employed in simulations to achieve a better finite-difference approximation of the potential gradient at the physical surface. Simulations are presented to demonstrate the accuracy and capability of this method in dealing with complex surface situations. An example simulation of the electrical double layer and electro-osmotic flow around a three-dimensional spherical particle is also presented. These simulated results are compared with analytical predictions and are found to be in excellent agreement. This method could be useful for electro-kinetic and colloidal simulations with complex boundaries, and can also be readily extended to other phenomena and processes, such as heat transfer and convection-diffusion systems.

  19. Fast and Accurate Hybrid Stream PCRTMSOLAR Radiative Transfer Model for Reflected Solar Spectrum Simulation in the Cloudy Atmosphere

    NASA Technical Reports Server (NTRS)

    Yang, Qiguang; Liu, Xu; Wu, Wan; Kizer, Susan; Baize, Rosemary R.

    2016-01-01

    A hybrid stream PCRTM-SOLAR model has been proposed for fast and accurate radiative transfer simulation. It calculates the reflected solar (RS) radiances with a fast coarse way and then, with the help of a pre-saved matrix, transforms the results to obtain the desired high accurate RS spectrum. The methodology has been demonstrated with the hybrid stream discrete ordinate (HSDO) radiative transfer (RT) model. The HSDO method calculates the monochromatic radiances using a 4-stream discrete ordinate method, where only a small number of monochromatic radiances are simulated with both 4-stream and a larger N-stream (N = 16) discrete ordinate RT algorithm. The accuracy of the obtained channel radiance is comparable to the result from N-stream moderate resolution atmospheric transmission version 5 (MODTRAN5). The root-mean-square errors are usually less than 5x10(exp -4) mW/sq cm/sr/cm. The computational speed is three to four-orders of magnitude faster than the medium speed correlated-k option MODTRAN5. This method is very efficient to simulate thousands of RS spectra under multi-layer clouds/aerosols and solar radiation conditions for climate change study and numerical weather prediction applications.

  20. Rapid and Accurate T2 Mapping from Multi Spin Echo Data Using Bloch-Simulation-Based Reconstruction

    PubMed Central

    Ben-Eliezer, Noam; Sodickson, Daniel K; Block, Tobias Kai

    2014-01-01

    Purpose Quantitative T2-relaxation-based contrast has the potential to provide valuable clinical information. Practical T2-mapping, however, is impaired either by prohibitively long acquisition times or by contamination of fast multi-echo protocols by stimulated and indirect echoes. This work presents a novel post-processing approach aiming to overcome the common penalties associated with multi-echo protocols, and enabling rapid and accurate mapping of T2 relaxation values. Methods Bloch simulations are used to estimate the actual echo modulation curve (EMC) in a multi spin-echo experiment. Simulations are repeated for a range of T2 values and transmit field scales, yielding a database of simulated EMCs, which is then used to identify the T2 value whose EMC most closely matches the experimentally measured data at each voxel. Results T2 maps of both phantom and in vivo scans were successfully reconstructed, closely matching maps produced from single spin-echo data. Results were consistent over the physiological range of T2 values and across different experimental settings. Conclusion The proposed technique allows accurate T2 mapping in clinically feasible scan times, free of user- and scanner-dependent variations, while providing a comprehensive framework that can be extended to model other parameters (e.g., T1, B1+, B0, diffusion) and support arbitrary acquisition schemes. PMID:24648387

  1. Thermodynamics of supersaturated steam: Molecular simulation results

    NASA Astrophysics Data System (ADS)

    Moučka, Filip; Nezbeda, Ivo

    2016-12-01

    Supersaturated steam modeled by the Gaussian charge polarizable model [P. Paricaud, M. Předota, and A. A. Chialvo, J. Chem. Phys. 122, 244511 (2005)] and BK3 model [P. Kiss and A. Baranyai, J. Chem. Phys. 138, 204507 (2013)] has been simulated at conditions occurring in steam turbines using the multiple-particle-move Monte Carlo for both the homogeneous phase and also implemented for the Gibbs ensemble Monte Carlo molecular simulation methods. Because of these thermodynamic conditions, a specific simulation algorithm has been developed to bypass common simulation problems resulting from very low densities of steam and cluster formation therein. In addition to pressure-temperature-density and orthobaric data, the distribution of clusters has also been evaluated. The obtained extensive data of high precision should serve as a basis for development of reliable molecular-based equations for properties of metastable steam.

  2. A fast but accurate excitonic simulation of the electronic circular dichroism of nucleic acids: how can it be achieved?

    PubMed

    Loco, Daniele; Jurinovich, Sandro; Di Bari, Lorenzo; Mennucci, Benedetta

    2016-01-14

    We present and discuss a simple and fast computational approach to the calculation of electronic circular dichroism spectra of nucleic acids. It is based on a exciton model in which the couplings are obtained in terms of the full transition-charge distributions, as resulting from TDDFT methods applied on the individual nucleobases. We validated the method on two systems, a DNA G-quadruplex and a RNA β-hairpin whose solution structures have been accurately determined by means of NMR. We have shown that the different characteristics of composition and structure of the two systems can lead to quite important differences in the dependence of the accuracy of the simulation on the excitonic parameters. The accurate reproduction of the CD spectra together with their interpretation in terms of the excitonic composition suggest that this method may lend itself as a general computational tool to both predict the spectra of hypothetic structures and define clear relationships between structural and ECD properties.

  3. Initial conditions for accurate N-body simulations of massive neutrino cosmologies

    NASA Astrophysics Data System (ADS)

    Zennaro, M.; Bel, J.; Villaescusa-Navarro, F.; Carbone, C.; Sefusatti, E.; Guzzo, L.

    2017-04-01

    The set-up of the initial conditions in cosmological N-body simulations is usually implemented by rescaling the desired low-redshift linear power spectrum to the required starting redshift consistently with the Newtonian evolution of the simulation. The implementation of this practical solution requires more care in the context of massive neutrino cosmologies, mainly because of the non-trivial scale-dependence of the linear growth that characterizes these models. In this work, we consider a simple two-fluid, Newtonian approximation for cold dark matter and massive neutrinos perturbations that can reproduce the cold matter linear evolution predicted by Boltzmann codes such as CAMB or CLASS with a 0.1 per cent accuracy or below for all redshift relevant to non-linear structure formation. We use this description, in the first place, to quantify the systematic errors induced by several approximations often assumed in numerical simulations, including the typical set-up of the initial conditions for massive neutrino cosmologies adopted in previous works. We then take advantage of the flexibility of this approach to rescale the late-time linear power spectra to the simulation initial redshift, in order to be as consistent as possible with the dynamics of the N-body code and the approximations it assumes. We implement our method in a public code (REPS rescaled power spectra for initial conditions with massive neutrinos https://github.com/matteozennaro/reps) providing the initial displacements and velocities for cold dark matter and neutrino particles that will allow accurate, i.e. 1 per cent level, numerical simulations for this cosmological scenario.

  4. Unfitted Two-Phase Flow Simulations in Pore-Geometries with Accurate

    NASA Astrophysics Data System (ADS)

    Heimann, Felix; Engwer, Christian; Ippisch, Olaf; Bastian, Peter

    2013-04-01

    The development of better macro scale models for multi-phase flow in porous media is still impeded by the lack of suitable methods for the simulation of such flow regimes on the pore scale. The highly complicated geometry of natural porous media imposes requirements with regard to stability and computational efficiency which current numerical methods fail to meet. Therefore, current simulation environments are still unable to provide a thorough understanding of porous media in multi-phase regimes and still fail to reproduce well known effects like hysteresis or the more peculiar dynamics of the capillary fringe with satisfying accuracy. Although flow simulations in pore geometries were initially the domain of Lattice-Boltzmann and other particle methods, the development of Galerkin methods for such applications is important as they complement the range of feasible flow and parameter regimes. In the recent past, it has been shown that unfitted Galerkin methods can be applied efficiently to topologically demanding geometries. However, in the context of two-phase flows, the interface of the two immiscible fluids effectively separates the domain in two sub-domains. The exact representation of such setups with multiple independent and time depending geometries exceeds the functionality of common unfitted methods. We present a new approach to pore scale simulations with an unfitted discontinuous Galerkin (UDG) method. Utilizing a recursive sub-triangulation algorithm, we extent the UDG method to setups with multiple independent geometries. This approach allows an accurate representation of the moving contact line and the interface conditions, i.e. the pressure jump across the interface. Example simulations in two and three dimensions illustrate and verify the stability and accuracy of this approach.

  5. A hybrid Boundary Element Unstructured Transmission-line (BEUT) method for accurate 2D electromagnetic simulation

    NASA Astrophysics Data System (ADS)

    Simmons, Daniel; Cools, Kristof; Sewell, Phillip

    2016-11-01

    Time domain electromagnetic simulation tools have the ability to model transient, wide-band applications, and non-linear problems. The Boundary Element Method (BEM) and the Transmission Line Modeling (TLM) method are both well established numerical techniques for simulating time-varying electromagnetic fields. The former surface based method can accurately describe outwardly radiating fields from piecewise uniform objects and efficiently deals with large domains filled with homogeneous media. The latter volume based method can describe inhomogeneous and non-linear media and has been proven to be unconditionally stable. Furthermore, the Unstructured TLM (UTLM) enables modelling of geometrically complex objects by using triangular meshes which removes staircasing and unnecessary extensions of the simulation domain. The hybridization of BEM and UTLM which is described in this paper is named the Boundary Element Unstructured Transmission-line (BEUT) method. It incorporates the advantages of both methods. The theory and derivation of the 2D BEUT method is described in this paper, along with any relevant implementation details. The method is corroborated by studying its correctness and efficiency compared to the traditional UTLM method when applied to complex problems such as the transmission through a system of Luneburg lenses and the modelling of antenna radomes for use in wireless communications.

  6. Accurate and fast simulation of channel noise in conductance-based model neurons by diffusion approximation.

    PubMed

    Linaro, Daniele; Storace, Marco; Giugliano, Michele

    2011-03-01

    Stochastic channel gating is the major source of intrinsic neuronal noise whose functional consequences at the microcircuit- and network-levels have been only partly explored. A systematic study of this channel noise in large ensembles of biophysically detailed model neurons calls for the availability of fast numerical methods. In fact, exact techniques employ the microscopic simulation of the random opening and closing of individual ion channels, usually based on Markov models, whose computational loads are prohibitive for next generation massive computer models of the brain. In this work, we operatively define a procedure for translating any Markov model describing voltage- or ligand-gated membrane ion-conductances into an effective stochastic version, whose computer simulation is efficient, without compromising accuracy. Our approximation is based on an improved Langevin-like approach, which employs stochastic differential equations and no Montecarlo methods. As opposed to an earlier proposal recently debated in the literature, our approximation reproduces accurately the statistical properties of the exact microscopic simulations, under a variety of conditions, from spontaneous to evoked response features. In addition, our method is not restricted to the Hodgkin-Huxley sodium and potassium currents and is general for a variety of voltage- and ligand-gated ion currents. As a by-product, the analysis of the properties emerging in exact Markov schemes by standard probability calculus enables us for the first time to analytically identify the sources of inaccuracy of the previous proposal, while providing solid ground for its modification and improvement we present here.

  7. CONDENSED MATTER: STRUCTURE, MECHANICAL AND THERMAL PROPERTIES: An Accurate Image Simulation Method for High-Order Laue Zone Effects

    NASA Astrophysics Data System (ADS)

    Cai, Can-Ying; Zeng, Song-Jun; Liu, Hong-Rong; Yang, Qi-Bin

    2008-05-01

    A completely different formulation for simulation of the high order Laue zone (HOLZ) diffractions is derived. It refers to the new method, i.e. the Taylor series (TS) method. To check the validity and accuracy of the TS method, we take polyvinglidene fluoride (PVDF) crystal as an example to calculate the exit wavefunction by the conventional multi-slice (CMS) method and the TS method. The calculated results show that the TS method is much more accurate than the CMS method and is independent of the slice thicknesses. Moreover, the pure first order Laue zone wavefunction by the TS method can reflect the major potential distribution of the first reciprocal plane.

  8. Numerical Methodology for Coupled Time-Accurate Simulations of Primary and Secondary Flowpaths in Gas Turbines

    NASA Technical Reports Server (NTRS)

    Przekwas, A. J.; Athavale, M. M.; Hendricks, R. C.; Steinetz, B. M.

    2006-01-01

    Detailed information of the flow-fields in the secondary flowpaths and their interaction with the primary flows in gas turbine engines is necessary for successful designs with optimized secondary flow streams. Present work is focused on the development of a simulation methodology for coupled time-accurate solutions of the two flowpaths. The secondary flowstream is treated using SCISEAL, an unstructured adaptive Cartesian grid code developed for secondary flows and seals, while the mainpath flow is solved using TURBO, a density based code with capability of resolving rotor-stator interaction in multi-stage machines. An interface is being tested that links the two codes at the rim seal to allow data exchange between the two codes for parallel, coupled execution. A description of the coupling methodology and the current status of the interface development is presented. Representative steady-state solutions of the secondary flow in the UTRC HP Rig disc cavity are also presented.

  9. Cartesian Off-Body Grid Adaption for Viscous Time- Accurate Flow Simulation

    NASA Technical Reports Server (NTRS)

    Buning, Pieter G.; Pulliam, Thomas H.

    2011-01-01

    An improved solution adaption capability has been implemented in the OVERFLOW overset grid CFD code. Building on the Cartesian off-body approach inherent in OVERFLOW and the original adaptive refinement method developed by Meakin, the new scheme provides for automated creation of multiple levels of finer Cartesian grids. Refinement can be based on the undivided second-difference of the flow solution variables, or on a specific flow quantity such as vorticity. Coupled with load-balancing and an inmemory solution interpolation procedure, the adaption process provides very good performance for time-accurate simulations on parallel compute platforms. A method of using refined, thin body-fitted grids combined with adaption in the off-body grids is presented, which maximizes the part of the domain subject to adaption. Two- and three-dimensional examples are used to illustrate the effectiveness and performance of the adaption scheme.

  10. Ventricular Fibrillation in Mammalian Hearts: Simulation Results

    NASA Astrophysics Data System (ADS)

    Fenton, Flavio H.

    2002-03-01

    The computational approach to understanding the initiation and evolution of cardiac arrhythmias forms a necessary link between experiment and theory. Numerical simulations combine useful mathematical models and complex geometry while offering clean and comprehensive data acquisition, reproducible results that can be compared to experiments, and the flexibility of exploring parameter space systematically. However, because cardiac dynamics occurs on many scales (on the order of 10^9 cells of size 10-100 microns with more than 40 ionic currents and time scales as fast as 0.01ms), roughly 10^17 operations are required to simulate just one second of real time. These intense computational requirements lead to significant implementation challenges even on existing supercomputers. Nevertheless, progress over the last decade in understanding the effects of some spatial scales and spatio-temporal dynamics on cardiac cell and tissue behavior justifies the use of certain simplifications which, along with improved models for cellular dynamics and detailed digital models of cardiac anatomy, are allowing simulation studies of full-size ventricles and atria. We describe this simulation problem from a combined numerical, physical and biological point of view, with an emphasis on the dynamics and stability of scroll waves of electrical activity in mammalian hearts and their relation to tachycardia, fibrillation and sudden death. Detailed simulations of electrical activity in ventricles including complex anatomy, anisotropic fiber structure, and electrophysiological effects of two drugs (DAM and CytoD) are presented and compared with experimental results.

  11. Accurate method for the Brownian dynamics simulation of spherical particles with hard-body interactions

    NASA Astrophysics Data System (ADS)

    Barenbrug, Theo M. A. O. M.; Peters, E. A. J. F. (Frank); Schieber, Jay D.

    2002-11-01

    In Brownian Dynamics simulations, the diffusive motion of the particles is simulated by adding random displacements, proportional to the square root of the chosen time step. When computing average quantities, these Brownian contributions usually average out, and the overall simulation error becomes proportional to the time step. A special situation arises if the particles undergo hard-body interactions that instantaneously change their properties, as in absorption or association processes, chemical reactions, etc. The common "naı̈ve simulation method" accounts for these interactions by checking for hard-body overlaps after every time step. Due to the simplification of the diffusive motion, a substantial part of the actual hard-body interactions is not detected by this method, resulting in an overall simulation error proportional to the square root of the time step. In this paper we take the hard-body interactions during the time step interval into account, using the relative positions of the particles at the beginning and at the end of the time step, as provided by the naı̈ve method, and the analytical solution for the diffusion of a point particle around an absorbing sphere. Öttinger used a similar approach for the one-dimensional case [Stochastic Processes in Polymeric Fluids (Springer, Berlin, 1996), p. 270]. We applied the "corrected simulation method" to the case of a simple, second-order chemical reaction. The results agree with recent theoretical predictions [K. Hyojoon and Joe S. Kook, Phys. Rev. E 61, 3426 (2000)]. The obtained simulation error is proportional to the time step, instead of its square root. The new method needs substantially less simulation time to obtain the same accuracy. Finally, we briefly discuss a straightforward way to extend the method for simulations of systems with additional (deterministic) forces.

  12. Titan's organic chemistry: Results of simulation experiments

    NASA Technical Reports Server (NTRS)

    Sagan, Carl; Thompson, W. Reid; Khare, Bishun N.

    1992-01-01

    Recent low pressure continuous low plasma discharge simulations of the auroral electron driven organic chemistry in Titan's mesosphere are reviewed. These simulations yielded results in good accord with Voyager observations of gas phase organic species. Optical constants of the brownish solid tholins produced in similar experiments are in good accord with Voyager observations of the Titan haze. Titan tholins are rich in prebiotic organic constituents; the Huygens entry probe may shed light on some of the processes that led to the origin of life on Earth.

  13. Voxel-based registration of simulated and real patient CBCT data for accurate dental implant pose estimation

    NASA Astrophysics Data System (ADS)

    Moreira, António H. J.; Queirós, Sandro; Morais, Pedro; Rodrigues, Nuno F.; Correia, André Ricardo; Fernandes, Valter; Pinho, A. C. M.; Fonseca, Jaime C.; Vilaça, João. L.

    2015-03-01

    The success of dental implant-supported prosthesis is directly linked to the accuracy obtained during implant's pose estimation (position and orientation). Although traditional impression techniques and recent digital acquisition methods are acceptably accurate, a simultaneously fast, accurate and operator-independent methodology is still lacking. Hereto, an image-based framework is proposed to estimate the patient-specific implant's pose using cone-beam computed tomography (CBCT) and prior knowledge of implanted model. The pose estimation is accomplished in a threestep approach: (1) a region-of-interest is extracted from the CBCT data using 2 operator-defined points at the implant's main axis; (2) a simulated CBCT volume of the known implanted model is generated through Feldkamp-Davis-Kress reconstruction and coarsely aligned to the defined axis; and (3) a voxel-based rigid registration is performed to optimally align both patient and simulated CBCT data, extracting the implant's pose from the optimal transformation. Three experiments were performed to evaluate the framework: (1) an in silico study using 48 implants distributed through 12 tridimensional synthetic mandibular models; (2) an in vitro study using an artificial mandible with 2 dental implants acquired with an i-CAT system; and (3) two clinical case studies. The results shown positional errors of 67+/-34μm and 108μm, and angular misfits of 0.15+/-0.08° and 1.4°, for experiment 1 and 2, respectively. Moreover, in experiment 3, visual assessment of clinical data results shown a coherent alignment of the reference implant. Overall, a novel image-based framework for implants' pose estimation from CBCT data was proposed, showing accurate results in agreement with dental prosthesis modelling requirements.

  14. Error Estimation And Accurate Mapping Based ALE Formulation For 3D Simulation Of Friction Stir Welding

    NASA Astrophysics Data System (ADS)

    Guerdoux, Simon; Fourment, Lionel

    2007-05-01

    An Arbitrary Lagrangian Eulerian (ALE) formulation is developed to simulate the different stages of the Friction Stir Welding (FSW) process with the FORGE3® F.E. software. A splitting method is utilized: a) the material velocity/pressure and temperature fields are calculated, b) the mesh velocity is derived from the domain boundary evolution and an adaptive refinement criterion provided by error estimation, c) P1 and P0 variables are remapped. Different velocity computation and remap techniques have been investigated, providing significant improvement with respect to more standard approaches. The proposed ALE formulation is applied to FSW simulation. Steady state welding, but also transient phases are simulated, showing good robustness and accuracy of the developed formulation. Friction parameters are identified for an Eulerian steady state simulation by comparison with experimental results. Void formation can be simulated. Simulations of the transient plunge and welding phases help to better understand the deposition process that occurs at the trailing edge of the probe. Flexibility and robustness of the model finally allows investigating the influence of new tooling designs on the deposition process.

  15. Industrial Compositional Streamline Simulation for Efficient and Accurate Prediction of Gas Injection and WAG Processes

    SciTech Connect

    Margot Gerritsen

    2008-10-31

    Gas-injection processes are widely and increasingly used for enhanced oil recovery (EOR). In the United States, for example, EOR production by gas injection accounts for approximately 45% of total EOR production and has tripled since 1986. The understanding of the multiphase, multicomponent flow taking place in any displacement process is essential for successful design of gas-injection projects. Due to complex reservoir geometry, reservoir fluid properties and phase behavior, the design of accurate and efficient numerical simulations for the multiphase, multicomponent flow governing these processes is nontrivial. In this work, we developed, implemented and tested a streamline based solver for gas injection processes that is computationally very attractive: as compared to traditional Eulerian solvers in use by industry it computes solutions with a computational speed orders of magnitude higher and a comparable accuracy provided that cross-flow effects do not dominate. We contributed to the development of compositional streamline solvers in three significant ways: improvement of the overall framework allowing improved streamline coverage and partial streamline tracing, amongst others; parallelization of the streamline code, which significantly improves wall clock time; and development of new compositional solvers that can be implemented along streamlines as well as in existing Eulerian codes used by industry. We designed several novel ideas in the streamline framework. First, we developed an adaptive streamline coverage algorithm. Adding streamlines locally can reduce computational costs by concentrating computational efforts where needed, and reduce mapping errors. Adapting streamline coverage effectively controls mass balance errors that mostly result from the mapping from streamlines to pressure grid. We also introduced the concept of partial streamlines: streamlines that do not necessarily start and/or end at wells. This allows more efficient coverage and avoids

  16. Numerical simulation and analysis of accurate blood oxygenation measurement by using optical resolution photoacoustic microscopy

    NASA Astrophysics Data System (ADS)

    Yu, Tianhao; Li, Qian; Li, Lin; Zhou, Chuanqing

    2016-10-01

    Accuracy of photoacoustic signal is the crux on measurement of oxygen saturation in functional photoacoustic imaging, which is influenced by factors such as defocus of laser beam, curve shape of large vessels and nonlinear saturation effect of optical absorption in biological tissues. We apply Monte Carlo model to simulate energy deposition in tissues and obtain photoacoustic signals reaching a simulated focused surface detector to investigate corresponding influence of these factors. We also apply compensation on photoacoustic imaging of in vivo cat cerebral cortex blood vessels, in which signals from different lateral positions of vessels are corrected based on simulation results. And this process on photoacoustic images can improve the smoothness and accuracy of oxygen saturation results.

  17. Accurate time delay technology in simulated test for high precision laser range finder

    NASA Astrophysics Data System (ADS)

    Chen, Zhibin; Xiao, Wenjian; Wang, Weiming; Xue, Mingxi

    2015-10-01

    With the continuous development of technology, the ranging accuracy of pulsed laser range finder (LRF) is higher and higher, so the maintenance demand of LRF is also rising. According to the dominant ideology of "time analog spatial distance" in simulated test for pulsed range finder, the key of distance simulation precision lies in the adjustable time delay. By analyzing and comparing the advantages and disadvantages of fiber and circuit delay, a method was proposed to improve the accuracy of the circuit delay without increasing the count frequency of the circuit. A high precision controllable delay circuit was designed by combining the internal delay circuit and external delay circuit which could compensate the delay error in real time. And then the circuit delay accuracy could be increased. The accuracy of the novel circuit delay methods proposed in this paper was actually measured by a high sampling rate oscilloscope actual measurement. The measurement result shows that the accuracy of the distance simulated by the circuit delay is increased from +/- 0.75m up to +/- 0.15m. The accuracy of the simulated distance is greatly improved in simulated test for high precision pulsed range finder.

  18. Continuum Level Results from Particle Simulations of Active Suspensions

    NASA Astrophysics Data System (ADS)

    Delmotte, Blaise; Climent, Eric; Plouraboue, Franck; Keaveny, Eric

    2014-11-01

    Accurately simulating active suspensions on the lab scale is a technical challenge. It requires considering large numbers of interacting swimmers with well described hydrodynamics in order to obtain representative and reliable statistics of suspension properties. We have developed a computationally scalable model based on an extension of the Force Coupling Method (FCM) to active particles. This tool can handle the many-body hydrodynamic interactions between O (105) swimmers while also accounting for finite-size effects, steady or time-dependent strokes, or variable swimmer aspect ratio. Results from our simulations of steady-stroke microswimmer suspensions coincide with those given by continuum models, but, in certain cases, we observe collective dynamics that these models do not predict. We provide robust statistics of resulting distributions and accurately characterize the growth rates of these instabilities. In addition, we explore the effect of the time-dependent stroke on the suspension properties, comparing with those from the steady-stroke simulations. Authors acknowledge the ANR project Motimo for funding and the Calmip computing centre for technical support.

  19. Molecular Simulation of Carbon Dioxide Capture by Montmorillonite Using an Accurate and Flexible Force Field

    SciTech Connect

    Romanov, V N; Cygan, R T; Myshakin, E M

    2012-06-21

    Naturally occurring clay minerals provide a distinctive material for carbon capture and carbon dioxide sequestration. Swelling clay minerals, such as the smectite variety, possess an aluminosilicate structure that is controlled by low-charge layers that readily expand to accommodate water molecules and, potentially, CO2. Recent experimental studies have demonstrated the efficacy of intercalating CO2 in the interlayer of layered clays, but little is known about the molecular mechanisms of the process and the extent of carbon capture as a function of clay charge and structure. A series of molecular dynamics simulations and vibrational analyses have been completed to assess the molecular interactions associated with incorporation of CO2 and H2O in the interlayer of montmorillonite clay and to help validate the models with experimental observation. An accurate and fully flexible set of interatomic potentials for CO2 is developed and combined with Clayff potentials to help evaluate the intercalation mechanism and examine the effect of molecular flexibility onthe diffusion rate of CO2 in water.

  20. Photovoltaic-electrolyzer system transient simulation results

    SciTech Connect

    Leigh, R.W.; Metz, P.D.; Michalek, K.

    1986-05-01

    Brookhaven National Laboratory has developed a Hydrogen Technology Evaluation Center to illustrate advanced hydrogen technology. The first phase of this effort investigated the use of solar energy to produce hydrogen from water via photovoltaic-powered electrolysis. A coordinated program of system testing, computer simulation, and economic analysis has been adopted to characterize and optimize the photovoltaic-electrolyzer system. This paper presents the initial transient simulation results. Innovative features of the modeling include the use of real weather data, detailed hourly modeling of thermal characteristics of the PV array and of system control strategies, and examination of systems over a wide range of power and voltage ratings. The transient simulation system TRNSYS was used, incorporating existing, modified or new component subroutines as required. For directly coupled systems, the authors found the PV array voltage which maximizes hydrogen production to be quite near the nominal electrolyzer voltage for a wide range of PV array powers. The array voltage which maximizes excess electricity production is slightly higher. The use of an ideal (100 percent efficient) maximum power tracking system provides only a six percent increase in annual hydrogen production. An examination of the effect of the PV array tilt indicates, as expected, that annual hydrogen production is insensitive to tilt angle within +-20 deg of latitude. Summer production greatly exceeds winter generation. Tilting the array, even to 90 deg, produces no significant increase in winter hydrogen production.

  1. ENTROPY PRODUCTION IN COLLISIONLESS SYSTEMS. III. RESULTS FROM SIMULATIONS

    SciTech Connect

    Barnes, Eric I.; Egerer, Colin P. E-mail: egerer.coli@uwlax.edu

    2015-05-20

    The equilibria formed by the self-gravitating, collisionless collapse of simple initial conditions have been investigated for decades. We present the results of our attempts to describe the equilibria formed in N-body simulations using thermodynamically motivated models. Previous work has suggested that it is possible to define distribution functions for such systems that describe maximum entropy states. These distribution functions are used to create radial density and velocity distributions for comparison to those from simulations. A wide variety of N-body code conditions are used to reduce the chance that results are biased by numerical issues. We find that a subset of initial conditions studied lead to equilibria that can be accurately described by these models, and that direct calculation of the entropy shows maximum values being achieved.

  2. Simulation of diurnal thermal energy storage systems: Preliminary results

    NASA Astrophysics Data System (ADS)

    Katipamula, S.; Somasundaram, S.; Williams, H. R.

    1994-12-01

    This report describes the results of a simulation of thermal energy storage (TES) integrated with a simple-cycle gas turbine cogeneration system. Integrating TES with cogeneration can serve the electrical and thermal loads independently while firing all fuel in the gas turbine. The detailed engineering and economic feasibility of diurnal TES systems integrated with cogeneration systems has been described in two previous PNL reports. The objective of this study was to lay the ground work for optimization of the TES system designs using a simulation tool called TRNSYS (TRaNsient SYstem Simulation). TRNSYS is a transient simulation program with a sequential-modular structure developed at the Solar Energy Laboratory, University of Wisconsin-Madison. The two TES systems selected for the base-case simulations were: (1) a one-tank storage model to represent the oil/rock TES system; and (2) a two-tank storage model to represent the molten nitrate salt TES system. Results of the study clearly indicate that an engineering optimization of the TES system using TRNSYS is possible. The one-tank stratified oil/rock storage model described here is a good starting point for parametric studies of a TES system. Further developments to the TRNSYS library of available models (economizer, evaporator, gas turbine, etc.) are recommended so that the phase-change processes is accurately treated.

  3. Fast Plasma Instrument for MMS: Simulation Results

    NASA Technical Reports Server (NTRS)

    Figueroa-Vinas, Adolfo; Adrian, Mark L.; Lobell, James V.; Simpson, David G.; Barrie, Alex; Winkert, George E.; Yeh, Pen-Shu; Moore, Thomas E.

    2008-01-01

    Magnetospheric Multiscale (MMS) mission will study small-scale reconnection structures and their rapid motions from closely spaced platforms using instruments capable of high angular, energy, and time resolution measurements. The Dual Electron Spectrometer (DES) of the Fast Plasma Instrument (FPI) for MMS meets these demanding requirements by acquiring the electron velocity distribution functions (VDFs) for the full sky with high-resolution angular measurements every 30 ms. This will provide unprecedented access to electron scale dynamics within the reconnection diffusion region. The DES consists of eight half-top-hat energy analyzers. Each analyzer has a 6 deg. x 11.25 deg. Full-sky coverage is achieved by electrostatically stepping the FOV of each of the eight sensors through four discrete deflection look directions. Data compression and burst memory management will provide approximately 30 minutes of high time resolution data during each orbit of the four MMS spacecraft. Each spacecraft will intelligently downlink the data sequences that contain the greatest amount of temporal structure. Here we present the results of a simulation of the DES analyzer measurements, data compression and decompression, as well as ground-based analysis using as a seed re-processed Cluster/PEACE electron measurements. The Cluster/PEACE electron measurements have been reprocessed through virtual DES analyzers with their proper geometrical, energy, and timing scale factors and re-mapped via interpolation to the DES angular and energy phase-space sampling measurements. The results of the simulated DES measurements are analyzed and the full moments of the simulated VDFs are compared with those obtained from the Cluster/PEACE spectrometer using a standard quadrature moment, a newly implemented spectral spherical harmonic method, and a singular value decomposition method. Our preliminary moment calculations show a remarkable agreement within the uncertainties of the measurements, with the

  4. Accurate optical simulation of nano-particle based internal scattering layers for light outcoupling from organic light emitting diodes

    NASA Astrophysics Data System (ADS)

    Egel, Amos; Gomard, Guillaume; Kettlitz, Siegfried W.; Lemmer, Uli

    2017-02-01

    We present a numerical strategy for the accurate simulation of light extraction from organic light emitting diodes (OLEDs) comprising an internal nano-particle based scattering layer. On the one hand, the light emission and propagation through the OLED thin film system (including the scattering layer) is treated by means of rigorous wave optics calculations using the T-matrix formalism. On the other hand, the propagation through the substrate is modeled in a ray optics approach. The results from the wave optics calculations enter in terms of the initial substrate radiation pattern and the bidirectional reflectivity distribution of the OLED stack with scattering layer. In order to correct for the truncation error due to a finite number of particles in the simulations, we extrapolate the results to infinitely extended scattering layers. As an application example, we estimate the optimal particle filling fraction for an internal scattering layer in a realistic OLED geometry. The presented treatment is designed to emerge from electromagnetic theory with as few additional assumptions as possible. It could thus serve as a baseline to validate faster but approximate simulation approaches.

  5. An Accurate Simulation Of Thermoforming And Blow-Molding Processes Using The Space Fiber Rotation (SFR) Concept

    NASA Astrophysics Data System (ADS)

    Ghomari, T.; Ayad, R.; Talbi, N.

    2007-05-01

    This work deals with a non-linear formulation of an axisymmetric hyperelastic solid model for thermoforming and blow-molding processes. It's based on a new kinematic concept labeled SFR (Space Fiber Rotation). The SFR-Axi element model uses a kinematic motion of a space linear fiber in order to obtain more accurate displacement field, without increasing the number of nodes. It improves in a significant way the precision of the linear element Q4 indeed. The corresponding numerical results are comparable and even better, in term of time CPU, with those of the 8-nodes higher order element Q8. A hyperelastic behavior law based on Mooney-Rivlin model has been implemented to allow the model better simulations of forming processes hollow plastic bodies. The numerical results, very promising, are given with considering or not the contact between the polymer.

  6. A time-accurate adaptive grid method and the numerical simulation of a shock-vortex interaction

    NASA Technical Reports Server (NTRS)

    Bockelie, Michael J.; Eiseman, Peter R.

    1990-01-01

    A time accurate, general purpose, adaptive grid method is developed that is suitable for multidimensional steady and unsteady numerical simulations. The grid point movement is performed in a manner that generates smooth grids which resolve the severe solution gradients and the sharp transitions in the solution gradients. The temporal coupling of the adaptive grid and the PDE solver is performed with a grid prediction correction method that is simple to implement and ensures the time accuracy of the grid. Time accurate solutions of the 2-D Euler equations for an unsteady shock vortex interaction demonstrate the ability of the adaptive method to accurately adapt the grid to multiple solution features.

  7. ANOVA parameters influence in LCF experimental data and simulation results

    NASA Astrophysics Data System (ADS)

    Delprete, C.; Sesanaa, R.; Vercelli, A.

    2010-06-01

    The virtual design of components undergoing thermo mechanical fatigue (TMF) and plastic strains is usually run in many phases. The numerical finite element method gives a useful instrument which becomes increasingly effective as the geometrical and numerical modelling gets more accurate. The constitutive model definition plays an important role in the effectiveness of the numerical simulation [1, 2] as, for example, shown in Figure 1. In this picture it is shown how a good cyclic plasticity constitutive model can simulate a cyclic load experiment. The component life estimation is the subsequent phase and it needs complex damage and life estimation models [3-5] which take into account of several parameters and phenomena contributing to damage and life duration. The calibration of these constitutive and damage models requires an accurate testing activity. In the present paper the main topic of the research activity is to investigate whether the parameters, which result to be influent in the experimental activity, influence the numerical simulations, thus defining the effectiveness of the models in taking into account of all the phenomena actually influencing the life of the component. To obtain this aim a procedure to tune the parameters needed to estimate the life of mechanical components undergoing TMF and plastic strains is presented for commercial steel. This procedure aims to be easy and to allow calibrating both material constitutive model (for the numerical structural simulation) and the damage and life model (for life assessment). The procedure has been applied to specimens. The experimental activity has been developed on three sets of tests run at several temperatures: static tests, high cycle fatigue (HCF) tests, low cycle fatigue (LCF) tests. The numerical structural FEM simulations have been run on a commercial non linear solver, ABAQUS®6.8. The simulations replied the experimental tests. The stress, strain, thermal results from the thermo structural FEM

  8. Accurate simulation of the electron cloud in the Fermilab Main Injector with VORPAL

    SciTech Connect

    Lebrun, Paul L.G.; Spentzouris, Panagiotis; Cary, John R.; Stoltz, Peter; Veitzer, Seth A.; /Tech-X, Boulder

    2011-01-01

    We present results from a precision simulation of the electron cloud (EC) in the Fermilab Main Injector using the code VORPAL. This is a fully 3d and self consistent treatment of the EC. Both distributions of electrons in 6D phase-space and E.M. field maps have been generated. This has been done for various configurations of the magnetic fields found around the machine have been studied. Plasma waves associated to the fluctuation density of the cloud have been analyzed. Our results are compared with those obtained with the POSINST code. The response of a Retarding Field Analyzer (RFA) to the EC has been simulated, as well as the more challenging microwave absorption experiment. Definite predictions of their exact response are difficult to obtain,mostly because of the uncertainties in the secondary emission yield and, in the case of the RFA, because of the sensitivity of the electron collection efficiency to unknown stray magnetic fields. Nonetheless, our simulations do provide guidance to the experimental program.

  9. Simulation Results Related to Stochastic Electrodynamics

    NASA Astrophysics Data System (ADS)

    Cole, Daniel C.

    2006-01-01

    Stochastic electrodynamics (SED) is a classical theory of nature advanced significantly in the 1960s by Trevor Marshall and Timothy Boyer. Since then, SED has continued to be investigated by a very small group of physicists. Early investigations seemed promising, as SED was shown to agree with quantum mechanics (QM) and quantum electrodynamics (QED) for a few linear systems. In particular, agreement was found for the simple harmonic electric dipole oscillator, physical systems composed of such oscillators and interacting electromagnetically, and free electromagnetic fields with boundary conditions imposed such as would enter into Casimir-type force calculations. These results were found to hold for both zero-point and non-zero temperature conditions. However, by the late 1970s and then into the early 1980s, researchers found that when investigating nonlinear systems, SED did not appear to provide agreement with the predictions of QM and QED. A proposed reason for this disagreement was advocated by Boyer and Cole that such nonlinear systems are not sufficiently realistic for describing atomic and molecular physical systems, which should be fundamentally based on the Coulombic binding potential. Analytic attempts on these systems have proven to be most difficult. Consequently, in recent years more attention has been placed on numerically simulating the interaction of a classical electron in a Coulombic binding potential, with classical electromagnetic radiation acting on the classical electron. Good agreement was found for this numerical simulation work as compared with predictions from QM. Here this worked is reviewed and possible directions are discussed. Recent simulation work involving subharmonic resonances for the classical hydrogen atom is also discussed; some of the properties of these subharmonic resonances seem quite interesting and unusual.

  10. Accurate simulation of two-dimensional optical microcavities with uniquely solvable boundary integral equations and trigonometric Galerkin discretization.

    PubMed

    Boriskina, Svetlana V; Sewell, Phillip; Benson, Trevor M; Nosich, Alexander I

    2004-03-01

    A fast and accurate method is developed to compute the natural frequencies and scattering characteristics of arbitrary-shape two-dimensional dielectric resonators. The problem is formulated in terms of a uniquely solvable set of second-kind boundary integral equations and discretized by the Galerkin method with angular exponents as global test and trial functions. The log-singular term is extracted from one of the kernels, and closed-form expressions are derived for the main parts of all the integral operators. The resulting discrete scheme has a very high convergence rate. The method is used in the simulation of several optical microcavities for modern dense wavelength-division-multiplexed systems.

  11. Utilizing fast multipole expansions for efficient and accurate quantum-classical molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Schwörer, Magnus; Lorenzen, Konstantin; Mathias, Gerald; Tavan, Paul

    2015-03-01

    Recently, a novel approach to hybrid quantum mechanics/molecular mechanics (QM/MM) molecular dynamics (MD) simulations has been suggested [Schwörer et al., J. Chem. Phys. 138, 244103 (2013)]. Here, the forces acting on the atoms are calculated by grid-based density functional theory (DFT) for a solute molecule and by a polarizable molecular mechanics (PMM) force field for a large solvent environment composed of several 103-105 molecules as negative gradients of a DFT/PMM hybrid Hamiltonian. The electrostatic interactions are efficiently described by a hierarchical fast multipole method (FMM). Adopting recent progress of this FMM technique [Lorenzen et al., J. Chem. Theory Comput. 10, 3244 (2014)], which particularly entails a strictly linear scaling of the computational effort with the system size, and adapting this revised FMM approach to the computation of the interactions between the DFT and PMM fragments of a simulation system, here, we show how one can further enhance the efficiency and accuracy of such DFT/PMM-MD simulations. The resulting gain of total performance, as measured for alanine dipeptide (DFT) embedded in water (PMM) by the product of the gains in efficiency and accuracy, amounts to about one order of magnitude. We also demonstrate that the jointly parallelized implementation of the DFT and PMM-MD parts of the computation enables the efficient use of high-performance computing systems. The associated software is available online.

  12. Utilizing fast multipole expansions for efficient and accurate quantum-classical molecular dynamics simulations

    SciTech Connect

    Schwörer, Magnus; Lorenzen, Konstantin; Mathias, Gerald; Tavan, Paul

    2015-03-14

    Recently, a novel approach to hybrid quantum mechanics/molecular mechanics (QM/MM) molecular dynamics (MD) simulations has been suggested [Schwörer et al., J. Chem. Phys. 138, 244103 (2013)]. Here, the forces acting on the atoms are calculated by grid-based density functional theory (DFT) for a solute molecule and by a polarizable molecular mechanics (PMM) force field for a large solvent environment composed of several 10{sup 3}-10{sup 5} molecules as negative gradients of a DFT/PMM hybrid Hamiltonian. The electrostatic interactions are efficiently described by a hierarchical fast multipole method (FMM). Adopting recent progress of this FMM technique [Lorenzen et al., J. Chem. Theory Comput. 10, 3244 (2014)], which particularly entails a strictly linear scaling of the computational effort with the system size, and adapting this revised FMM approach to the computation of the interactions between the DFT and PMM fragments of a simulation system, here, we show how one can further enhance the efficiency and accuracy of such DFT/PMM-MD simulations. The resulting gain of total performance, as measured for alanine dipeptide (DFT) embedded in water (PMM) by the product of the gains in efficiency and accuracy, amounts to about one order of magnitude. We also demonstrate that the jointly parallelized implementation of the DFT and PMM-MD parts of the computation enables the efficient use of high-performance computing systems. The associated software is available online.

  13. Medical Simulation Practices 2010 Survey Results

    NASA Technical Reports Server (NTRS)

    McCrindle, Jeffrey J.

    2011-01-01

    Medical Simulation Centers are an essential component of our learning infrastructure to prepare doctors and nurses for their careers. Unlike the military and aerospace simulation industry, very little has been published regarding the best practices currently in use within medical simulation centers. This survey attempts to provide insight into the current simulation practices at medical schools, hospitals, university nursing programs and community college nursing programs. Students within the MBA program at Saint Joseph's University conducted a survey of medical simulation practices during the summer 2010 semester. A total of 115 institutions responded to the survey. The survey resus discuss overall effectiveness of current simulation centers as well as the tools and techniques used to conduct the simulation activity

  14. On high-order accurate weighted essentially non-oscillatory and discontinuous Galerkin schemes for compressible turbulence simulations.

    PubMed

    Shu, Chi-Wang

    2013-01-13

    In this article, we give a brief overview on high-order accurate shock capturing schemes with the aim of applications in compressible turbulence simulations. The emphasis is on the basic methodology and recent algorithm developments for two classes of high-order methods: the weighted essentially non-oscillatory and discontinuous Galerkin methods.

  15. TRIM—3D: a three-dimensional model for accurate simulation of shallow water flow

    USGS Publications Warehouse

    Casulli, Vincenzo; Bertolazzi, Enrico; Cheng, Ralph T.

    1993-01-01

    A semi-implicit finite difference formulation for the numerical solution of three-dimensional tidal circulation is discussed. The governing equations are the three-dimensional Reynolds equations in which the pressure is assumed to be hydrostatic. A minimal degree of implicitness has been introduced in the finite difference formula so that the resulting algorithm permits the use of large time steps at a minimal computational cost. This formulation includes the simulation of flooding and drying of tidal flats, and is fully vectorizable for an efficient implementation on modern vector computers. The high computational efficiency of this method has made it possible to provide the fine details of circulation structure in complex regions that previous studies were unable to obtain. For proper interpretation of the model results suitable interactive graphics is also an essential tool.

  16. Consistent Multigroup Theory Enabling Accurate Course-Group Simulation of Gen IV Reactors

    SciTech Connect

    Rahnema, Farzad; Haghighat, Alireza; Ougouag, Abderrafi

    2013-11-29

    The objective of this proposal is the development of a consistent multi-group theory that accurately accounts for the energy-angle coupling associated with collapsed-group cross sections. This will allow for coarse-group transport and diffusion theory calculations that exhibit continuous energy accuracy and implicitly treat cross- section resonances. This is of particular importance when considering the highly heterogeneous and optically thin reactor designs within the Next Generation Nuclear Plant (NGNP) framework. In such reactors, ignoring the influence of anisotropy in the angular flux on the collapsed cross section, especially at the interface between core and reflector near which control rods are located, results in inaccurate estimates of the rod worth, a serious safety concern. The scope of this project will include the development and verification of a new multi-group theory enabling high-fidelity transport and diffusion calculations in coarse groups, as well as a methodology for the implementation of this method in existing codes. This will allow for a higher accuracy solution of reactor problems while using fewer groups and will reduce the computational expense. The proposed research represents a fundamental advancement in the understanding and improvement of multi- group theory for reactor analysis.

  17. Accurate schemes for calculation of thermodynamic properties of liquid mixtures from molecular dynamics simulations.

    PubMed

    Caro, Miguel A; Laurila, Tomi; Lopez-Acevedo, Olga

    2016-12-28

    We explore different schemes for improved accuracy of entropy calculations in aqueous liquid mixtures from molecular dynamics (MD) simulations. We build upon the two-phase thermodynamic (2PT) model of Lin et al. [J. Chem. Phys. 119, 11792 (2003)] and explore new ways to obtain the partition between the gas-like and solid-like parts of the density of states, as well as the effect of the chosen ideal "combinatorial" entropy of mixing, both of which have a large impact on the results. We also propose a first-order correction to the issue of kinetic energy transfer between degrees of freedom (DoF). This problem arises when the effective temperatures of translational, rotational, and vibrational DoF are not equal, either due to poor equilibration or reduced system size/time sampling, which are typical problems for ab initio MD. The new scheme enables improved convergence of the results with respect to configurational sampling, by up to one order of magnitude, for short MD runs. To ensure a meaningful assessment, we perform MD simulations of liquid mixtures of water with several other molecules of varying sizes: methanol, acetonitrile, N, N-dimethylformamide, and n-butanol. Our analysis shows that results in excellent agreement with experiment can be obtained with little computational effort for some systems. However, the ability of the 2PT method to succeed in these calculations is strongly influenced by the choice of force field, the fluidicity (hard-sphere) formalism employed to obtain the solid/gas partition, and the assumed combinatorial entropy of mixing. We tested two popular force fields, GAFF and OPLS with SPC/E water. For the mixtures studied, the GAFF force field seems to perform as a slightly better "all-around" force field when compared to OPLS+SPC/E.

  18. SALTSTONE MATRIX CHARACTERIZATION AND STADIUM SIMULATION RESULTS

    SciTech Connect

    Langton, C.

    2009-07-30

    SIMCO Technologies, Inc. was contracted to evaluate the durability of the saltstone matrix material and to measure saltstone transport properties. This information will be used to: (1) Parameterize the STADIUM{reg_sign} service life code, (2) Predict the leach rate (degradation rate) for the saltstone matrix over 10,000 years using the STADIUM{reg_sign} concrete service life code, and (3) Validate the modeled results by conducting leaching (water immersion) tests. Saltstone durability for this evaluation is limited to changes in the matrix itself and does not include changes in the chemical speciation of the contaminants in the saltstone. This report summarized results obtained to date which include: characterization data for saltstone cured up to 365 days and characterization of saltstone cured for 137 days and immersed in water for 31 days. Chemicals for preparing simulated non-radioactive salt solution were obtained from chemical suppliers. The saltstone slurry was mixed according to directions provided by SRNL. However SIMCO Technologies Inc. personnel made a mistake in the premix proportions. The formulation SIMCO personnel used to prepare saltstone premix was not the reference mix proportions: 45 wt% slag, 45 wt% fly ash, and 10 wt% cement. SIMCO Technologies Inc. personnel used the following proportions: 21 wt% slag, 65 wt% fly ash, and 14 wt% cement. The mistake was acknowledged and new mixes have been prepared and are curing. The results presented in this report are assumed to be conservative since the excessive fly ash was used in the SIMCO saltstone. The SIMCO mixes are low in slag which is very reactive in the caustic salt solution. The impact is that the results presented in this report are expected to be conservative since the samples prepared were deficient in slag and contained excess fly ash. The hydraulic reactivity of slag is about four times that of fly ash so the amount of hydrated binder formed per unit volume in the SIMCO saltstone samples is

  19. Exploring Space Physics Concepts Using Simulation Results

    NASA Astrophysics Data System (ADS)

    Gross, N. A.

    2008-05-01

    The Center for Integrated Space Weather Modeling (CISM), a Science and Technology Center (STC) funded by the National Science Foundation, has the goal of developing a suite of integrated physics based computer models of the space environment that can follow the evolution of a space weather event from the Sun to the Earth. In addition to the research goals, CISM is also committed to training the next generation of space weather professionals who are imbued with a system view of space weather. This view should include an understanding of both helio-spheric and geo-space phenomena. To this end, CISM offers a yearly Space Weather Summer School targeted to first year graduate students, although advanced undergraduates and space weather professionals have also attended. This summer school uses a number of innovative pedagogical techniques including devoting each afternoon to a computer lab exercise that use results from research quality simulations and visualization techniques, along with ground based and satellite data to explore concepts introduced during the morning lectures. These labs are suitable for use in wide variety educational settings from formal classroom instruction to outreach programs. The goal of this poster is to outline the goals and content of the lab materials so that instructors may evaluate their potential use in the classroom or other settings.

  20. Mathematical analysis and algorithms for efficiently and accurately implementing stochastic simulations of short-term synaptic depression and facilitation.

    PubMed

    McDonnell, Mark D; Mohan, Ashutosh; Stricker, Christian

    2013-01-01

    The release of neurotransmitter vesicles after arrival of a pre-synaptic action potential (AP) at cortical synapses is known to be a stochastic process, as is the availability of vesicles for release. These processes are known to also depend on the recent history of AP arrivals, and this can be described in terms of time-varying probabilities of vesicle release. Mathematical models of such synaptic dynamics frequently are based only on the mean number of vesicles released by each pre-synaptic AP, since if it is assumed there are sufficiently many vesicle sites, then variance is small. However, it has been shown recently that variance across sites can be significant for neuron and network dynamics, and this suggests the potential importance of studying short-term plasticity using simulations that do generate trial-to-trial variability. Therefore, in this paper we study several well-known conceptual models for stochastic availability and release. We state explicitly the random variables that these models describe and propose efficient algorithms for accurately implementing stochastic simulations of these random variables in software or hardware. Our results are complemented by mathematical analysis and statement of pseudo-code algorithms.

  1. Numerical parameter constraints for accurate PIC-DSMC simulation of breakdown from arc initiation to stable arcs

    NASA Astrophysics Data System (ADS)

    Moore, Christopher; Hopkins, Matthew; Moore, Stan; Boerner, Jeremiah; Cartwright, Keith

    2015-09-01

    Simulation of breakdown is important for understanding and designing a variety of applications such as mitigating undesirable discharge events. Such simulations need to be accurate through early time arc initiation to late time stable arc behavior. Here we examine constraints on the timestep and mesh size required for arc simulations using the particle-in-cell (PIC) method with direct simulation Monte Carlo (DMSC) collisions. Accurate simulation of electron avalanche across a fixed voltage drop and constant neutral density (reduced field of 1000 Td) was found to require a timestep ~ 1/100 of the mean time between collisions and a mesh size ~ 1/25 the mean free path. These constraints are much smaller than the typical PIC-DSMC requirements for timestep and mesh size. Both constraints are related to the fact that charged particles are accelerated by the external field. Thus gradients in the electron energy distribution function can exist at scales smaller than the mean free path and these must be resolved by the mesh size for accurate collision rates. Additionally, the timestep must be small enough that the particle energy change due to the fields be small in order to capture gradients in the cross sections versus energy. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. DOE's National Nuclear Security Administration under Contract DE-AC04-94AL85000.

  2. An efficient and accurate model of the coax cable feeding structure for FEM simulations

    NASA Technical Reports Server (NTRS)

    Gong, Jian; Volakis, John L.

    1995-01-01

    An efficient and accurate coax cable feed model is proposed for microstrip or cavity-backed patch antennas in the context of a hybrid finite element method (FEM). A TEM mode at the cavity-cable junction is assumed for the FEM truncation and system excitation. Of importance in this implementation is that the cavity unknowns are related to the model fields by enforcing an equipotential condition rather than field continuity. This scheme proved quite accurate and may be applied to other decomposed systems as a connectivity constraint. Comparisons of our predictions with input impedance measurements are presented and demonstrate the substantially improved accuracy of the proposed model.

  3. Accurate simulation of the electron cloud in the Fermilab Main Injector with VORPAL

    SciTech Connect

    Lebrun, Paul L.G.; Spentzouris, Panagiotis; Cary, John R.; Stoltz, Peter; Veitzer, Seth A.; /Tech-X, Boulder

    2010-05-01

    Precision simulations of the electron cloud at the Fermilab Main Injector have been studied using the plasma simulation code VORPAL. Fully 3D and self consistent solutions that includes E.M. field maps generated by the cloud and the proton bunches have been obtained, as well detailed distributions of the electron's 6D phase space. We plan to include such maps in the ongoing simulation of the space charge effects in the Main Injector. Simulations of the response of beam position monitors, retarding field analyzers and microwave transmission experiments are ongoing.

  4. Metrology target design simulations for accurate and robust scatterometry overlay measurements

    NASA Astrophysics Data System (ADS)

    Ben-Dov, Guy; Tarshish-Shapir, Inna; Gready, David; Ghinovker, Mark; Adel, Mike; Herzel, Eitan; Oh, Soonho; Choi, DongSub; Han, Sang Hyun; El Kodadi, Mohamed; Hwang, Chan; Lee, Jeongjin; Lee, Seung Yoon; Lee, Kuntack

    2016-03-01

    Overlay metrology target design is an essential step prior to performing overlay measurements. This step is done through the optimization of target parameters for a given process stack. A simulation tool is therefore used to improve measurement performances. This work shows how our Metrology Target Design (MTD) simulator helps significantly in the target design process. We show the role of film and Optical CD measurements in improving significantly the fidelity of the simulations. We demonstrate that for various target design parameters we are capable of predicting measured performance metrics by simulations and correctly rank various designs performances.

  5. A novel approach for accurate radiative transfer in cosmological hydrodynamic simulations

    NASA Astrophysics Data System (ADS)

    Petkova, Margarita; Springel, Volker

    2011-08-01

    accurately deal with non-equilibrium effects. We discuss several tests of the new method, including shadowing configurations in two and three dimensions, ionized sphere expansion in static and dynamic density fields and the ionization of a cosmological density field. The tests agree favourably with analytical expectations and results based on other numerical radiative transfer approximations.

  6. Bayesian parameter estimation of a k-ε model for accurate jet-in-crossflow simulations

    SciTech Connect

    Ray, Jaideep; Lefantzi, Sophia; Arunajatesan, Srinivasan; Dechant, Lawrence

    2016-05-31

    Reynolds-averaged Navier–Stokes models are not very accurate for high-Reynolds-number compressible jet-in-crossflow interactions. The inaccuracy arises from the use of inappropriate model parameters and model-form errors in the Reynolds-averaged Navier–Stokes model. In this study, the hypothesis is pursued that Reynolds-averaged Navier–Stokes predictions can be significantly improved by using parameters inferred from experimental measurements of a supersonic jet interacting with a transonic crossflow.

  7. 2-D Simulations for Accurate Extraction of the Specific Contact Resistivity from Contact Resistance Data,

    DTIC Science & Technology

    1985-01-01

    Bridge Kelvin Resistor, the Contact End Resistor, and the Transmission pletely by its sheet resistance . We shall concentrate here on semiconduc- Line...Tap Resistor. For each particular structure, a wniversal set of curves tar to metal contacts. Since the metal sheet resistance is much lower than is...derived that allows accurate determination of V,, given the geometry Of diffusion sheet resistance , metal is considered to be an equipotential the

  8. A Variable Coefficient Method for Accurate Monte Carlo Simulation of Dynamic Asset Price

    NASA Astrophysics Data System (ADS)

    Li, Yiming; Hung, Chih-Young; Yu, Shao-Ming; Chiang, Su-Yun; Chiang, Yi-Hui; Cheng, Hui-Wen

    2007-07-01

    In this work, we propose an adaptive Monte Carlo (MC) simulation technique to compute the sample paths for the dynamical asset price. In contrast to conventional MC simulation with constant drift and volatility (μ,σ), our MC simulation is performed with variable coefficient methods for (μ,σ) in the solution scheme, where the explored dynamic asset pricing model starts from the formulation of geometric Brownian motion. With the method of simultaneously updated (μ,σ), more than 5,000 runs of MC simulation are performed to fulfills basic accuracy of the large-scale computation and suppresses statistical variance. Daily changes of stock market index in Taiwan and Japan are investigated and analyzed.

  9. The Space-Time Conservative Schemes for Large-Scale, Time-Accurate Flow Simulations with Tetrahedral Meshes

    NASA Technical Reports Server (NTRS)

    Venkatachari, Balaji Shankar; Streett, Craig L.; Chang, Chau-Lyan; Friedlander, David J.; Wang, Xiao-Yen; Chang, Sin-Chung

    2016-01-01

    Despite decades of development of unstructured mesh methods, high-fidelity time-accurate simulations are still predominantly carried out on structured, or unstructured hexahedral meshes by using high-order finite-difference, weighted essentially non-oscillatory (WENO), or hybrid schemes formed by their combinations. In this work, the space-time conservation element solution element (CESE) method is used to simulate several flow problems including supersonic jet/shock interaction and its impact on launch vehicle acoustics, and direct numerical simulations of turbulent flows using tetrahedral meshes. This paper provides a status report for the continuing development of the space-time conservation element solution element (CESE) numerical and software framework under the Revolutionary Computational Aerosciences (RCA) project. Solution accuracy and large-scale parallel performance of the numerical framework is assessed with the goal of providing a viable paradigm for future high-fidelity flow physics simulations.

  10. Evaluation of a Second-Order Accurate Navier-Stokes Code for Detached Eddy Simulation Past a Circular Cylinder

    NASA Technical Reports Server (NTRS)

    Vatsa, Veer N.; Singer, Bart A.

    2003-01-01

    We evaluate the applicability of a production computational fluid dynamics code for conducting detached eddy simulation for unsteady flows. A second-order accurate Navier-Stokes code developed at NASA Langley Research Center, known as TLNS3D, is used for these simulations. We focus our attention on high Reynolds number flow (Re = 5 x 10(sup 4) - 1.4 x 10(sup 5)) past a circular cylinder to simulate flows with large-scale separations. We consider two types of flow situations: one in which the flow at the separation point is laminar, and the other in which the flow is already turbulent when it detaches from the surface of the cylinder. Solutions are presented for two- and three-dimensional calculations using both the unsteady Reynolds-averaged Navier-Stokes paradigm and the detached eddy simulation treatment. All calculations use the standard Spalart-Allmaras turbulence model as the base model.

  11. Ultrasonic noninvasive temperature estimation using echoshift gradient maps: simulation results.

    PubMed

    Techavipoo, Udomchai; Chen, Quan; Varghese, Tomy

    2005-07-01

    Percutaneous ultrasound-image-guided radiofrequency (rf) ablation is an effective treatment for patients with hepatic malignancies that are excluded from surgical resection due to other complications. However, ablated regions are not clearly differentiated from normal untreated regions using conventional ultrasound imaging due to similar echogenic tissue properties. In this paper, we investigate the statistics that govern the relationship between temperature elevation and the corresponding temperature map obtained from the gradient of the echoshifts obtained using consecutive ultrasound radiofrequency signals. A relationship derived using experimental data on the sound speed and tissue expansion variations measured on canine liver tissue samples at different elevated temperatures is utilized to generate ultrasound radiofrequency simulated data. The simulated data set is then utilized to statistically estimate the accuracy and precision of the temperature distributions obtained. The results show that temperature increases between 37 and 67 degrees C can be estimated with standard deviations of +/- 3 degrees C. Our results also indicate that the correlation coefficient between consecutive radiofrequency signals should be greater than 0.85 to obtain accurate temperature estimates.

  12. Enabling R&D for accurate simulation of non-ideal explosives.

    SciTech Connect

    Aidun, John Bahram; Thompson, Aidan Patrick; Schmitt, Robert Gerard

    2010-09-01

    We implemented two numerical simulation capabilities essential to reliably predicting the effect of non-ideal explosives (NXs). To begin to be able to treat the multiple, competing, multi-step reaction paths and slower kinetics of NXs, Sandia's CTH shock physics code was extended to include the TIGER thermochemical equilibrium solver as an in-line routine. To facilitate efficient exploration of reaction pathways that need to be identified for the CTH simulations, we implemented in Sandia's LAMMPS molecular dynamics code the MSST method, which is a reactive molecular dynamics technique for simulating steady shock wave response. Our preliminary demonstrations of these two capabilities serve several purposes: (i) they demonstrate proof-of-principle for our approach; (ii) they provide illustration of the applicability of the new functionality; and (iii) they begin to characterize the use of the new functionality and identify where improvements will be needed for the ultimate capability to meet national security needs. Next steps are discussed.

  13. OBSERVING SIMULATED PROTOSTARS WITH OUTFLOWS: HOW ACCURATE ARE PROTOSTELLAR PROPERTIES INFERRED FROM SEDs?

    SciTech Connect

    Offner, Stella S. R.; Robitaille, Thomas P.; Hansen, Charles E.; Klein, Richard I.; McKee, Christopher F.

    2012-07-10

    The properties of unresolved protostars and their local environment are frequently inferred from spectral energy distributions (SEDs) using radiative transfer modeling. In this paper, we use synthetic observations of realistic star formation simulations to evaluate the accuracy of properties inferred from fitting model SEDs to observations. We use ORION, an adaptive mesh refinement (AMR) three-dimensional gravito-radiation-hydrodynamics code, to simulate low-mass star formation in a turbulent molecular cloud including the effects of protostellar outflows. To obtain the dust temperature distribution and SEDs of the forming protostars, we post-process the simulations using HYPERION, a state-of-the-art Monte Carlo radiative transfer code. We find that the ORION and HYPERION dust temperatures typically agree within a factor of two. We compare synthetic SEDs of embedded protostars for a range of evolutionary times, simulation resolutions, aperture sizes, and viewing angles. We demonstrate that complex, asymmetric gas morphology leads to a variety of classifications for individual objects as a function of viewing angle. We derive best-fit source parameters for each SED through comparison with a pre-computed grid of radiative transfer models. While the SED models correctly identify the evolutionary stage of the synthetic sources as embedded protostars, we show that the disk and stellar parameters can be very discrepant from the simulated values, which is expected since the disk and central source are obscured by the protostellar envelope. Parameters such as the stellar accretion rate, stellar mass, and disk mass show better agreement, but can still deviate significantly, and the agreement may in some cases be artificially good due to the limited range of parameters in the set of model SEDs. Lack of correlation between the model and simulation properties in many individual instances cautions against overinterpreting properties inferred from SEDs for unresolved protostellar

  14. A hybrid method for efficient and accurate simulations of diffusion compartment imaging signals

    NASA Astrophysics Data System (ADS)

    Rensonnet, Gaëtan; Jacobs, Damien; Macq, Benoît; Taquet, Maxime

    2015-12-01

    Diffusion-weighted imaging is sensitive to the movement of water molecules through the tissue microstructure and can therefore be used to gain insight into the tissue cellular architecture. While the diffusion signal arising from simple geometrical microstructure is known analytically, it remains unclear what diffusion signal arises from complex microstructural configurations. Such knowledge is important to design optimal acquisition sequences, to understand the limitations of diffusion-weighted imaging and to validate novel models of the brain microstructure. We present a novel framework for the efficient simulation of high-quality DW-MRI signals based on the hybrid combination of exact analytic expressions in simple geometric compartments such as cylinders and spheres and Monte Carlo simulations in more complex geometries. We validate our approach on synthetic arrangements of parallel cylinders representing the geometry of white matter fascicles, by comparing it to complete, all-out Monte Carlo simulations commonly used in the literature. For typical configurations, equal levels of accuracy are obtained with our hybrid method in less than one fifth of the computational time required for Monte Carlo simulations.

  15. Accurate treatments of electrostatics for computer simulations of biological systems: A brief survey of developments and existing problems

    NASA Astrophysics Data System (ADS)

    Yi, Sha-Sha; Pan, Cong; Hu, Zhong-Han

    2015-12-01

    Modern computer simulations of biological systems often involve an explicit treatment of the complex interactions among a large number of molecules. While it is straightforward to compute the short-ranged Van der Waals interaction in classical molecular dynamics simulations, it has been a long-lasting issue to develop accurate methods for the longranged Coulomb interaction. In this short review, we discuss three types of methodologies for the accurate treatment of electrostatics in simulations of explicit molecules: truncation-type methods, Ewald-type methods, and mean-field-type methods. Throughout the discussion, we brief the formulations and developments of these methods, emphasize the intrinsic connections among the three types of methods, and focus on the existing problems which are often associated with the boundary conditions of electrostatics. This brief survey is summarized with a short perspective on future trends along the method developments and applications in the field of biological simulations. Project supported by the National Natural Science Foundation of China (Grant Nos. 91127015 and 21522304) and the Open Project from the State Key Laboratory of Theoretical Physics, and the Innovation Project from the State Key Laboratory of Supramolecular Structure and Materials.

  16. A new class of accurate, mesh-free hydrodynamic simulation methods

    NASA Astrophysics Data System (ADS)

    Hopkins, Philip F.

    2015-06-01

    We present two new Lagrangian methods for hydrodynamics, in a systematic comparison with moving-mesh, smoothed particle hydrodynamics (SPH), and stationary (non-moving) grid methods. The new methods are designed to simultaneously capture advantages of both SPH and grid-based/adaptive mesh refinement (AMR) schemes. They are based on a kernel discretization of the volume coupled to a high-order matrix gradient estimator and a Riemann solver acting over the volume `overlap'. We implement and test a parallel, second-order version of the method with self-gravity and cosmological integration, in the code GIZMO:1 this maintains exact mass, energy and momentum conservation; exhibits superior angular momentum conservation compared to all other methods we study; does not require `artificial diffusion' terms; and allows the fluid elements to move with the flow, so resolution is automatically adaptive. We consider a large suite of test problems, and find that on all problems the new methods appear competitive with moving-mesh schemes, with some advantages (particularly in angular momentum conservation), at the cost of enhanced noise. The new methods have many advantages versus SPH: proper convergence, good capturing of fluid-mixing instabilities, dramatically reduced `particle noise' and numerical viscosity, more accurate sub-sonic flow evolution, and sharp shock-capturing. Advantages versus non-moving meshes include: automatic adaptivity, dramatically reduced advection errors and numerical overmixing, velocity-independent errors, accurate coupling to gravity, good angular momentum conservation and elimination of `grid alignment' effects. We can, for example, follow hundreds of orbits of gaseous discs, while AMR and SPH methods break down in a few orbits. However, fixed meshes minimize `grid noise'. These differences are important for a range of astrophysical problems.

  17. Time-accurate simulations of a shear layer forced at a single frequency

    NASA Technical Reports Server (NTRS)

    Claus, R. W.; Huang, P. G.; Macinnes, J. M.

    1988-01-01

    Calculations are presented for the forced shear layer studied experimentally by Oster and Wygnanski, and Weisbrot. Two different computational approaches are examined: Direct Numerical Simulation (DNS) and Large Eddy Simulation (LES). The DNS approach solves the full three dimensional Navier-Stokes equations for a temporally evolving mixing layer, while the LES approach solves the two dimensional Navier-Stokes equations with a subgrid scale turbulence model. While the comparison between these calculations and experimental data was hampered by a lack of information on the inflow boundary conditions, the calculations are shown to qualitatively agree with several aspects of the experiment. The sensitivity of these calculations to factors such as mesh refinement and Reynolds number is illustrated.

  18. Pre-Stall Behavior of a Transonic Axial Compressor Stage via Time-Accurate Numerical Simulation

    NASA Technical Reports Server (NTRS)

    Chen, Jen-Ping; Hathaway, Michael D.; Herrick, Gregory P.

    2008-01-01

    CFD calculations using high-performance parallel computing were conducted to simulate the pre-stall flow of a transonic compressor stage, NASA compressor Stage 35. The simulations were run with a full-annulus grid that models the 3D, viscous, unsteady blade row interaction without the need for an artificial inlet distortion to induce stall. The simulation demonstrates the development of the rotating stall from the growth of instabilities. Pressure-rise performance and pressure traces are compared with published experimental data before the study of flow evolution prior to the rotating stall. Spatial FFT analysis of the flow indicates a rotating long-length disturbance of one rotor circumference, which is followed by a spike-type breakdown. The analysis also links the long-length wave disturbance with the initiation of the spike inception. The spike instabilities occur when the trajectory of the tip clearance flow becomes perpendicular to the axial direction. When approaching stall, the passage shock changes from a single oblique shock to a dual-shock, which distorts the perpendicular trajectory of the tip clearance vortex but shows no evidence of flow separation that may contribute to stall.

  19. Can virtual simulation of breast tangential portals accurately predict lung and heart volumes?

    PubMed

    Cooke, Stacey; Rattray, Greg

    2003-03-01

    A treatment portal or simulator image has traditionally been used to demonstrate the lung and heart coverage of the breast tangential portal. In many cases, these images were acquired as a planning session on the linear accelerator. The patients were also CT scanned to assess the lung/heart volume and to determine the surgical site depth for the electron-boost energy. A study using 50 consecutive patients was performed comparing the digitally reconstructed radiograph (DRR) from the virtual simulation with treatment portal images. Modification to the patient's arm position is required when performing the planning CT scans due to the aperture size of the CT scanner. Virtual simulation was used to assess the potential variation of lung and heart measurements. The average difference in lung volume between the DRR and portal image was less than 2 mm, with a range of 0-5 mm. Arm position did not have a significant impact on field deviation; however, great care was taken to minimize any changes in arm position. The modification of the arm position for CT scanning did not lead to significant variations between the DRRs and portal images. The Advantage Sim software has proven capable of producing good quality DRR images, providing a realistic representation of the lung and heart volume included in the treatment portal.

  20. Accurate prediction of unsteady and time-averaged pressure loads using a hybrid Reynolds-Averaged/large-eddy simulation technique

    NASA Astrophysics Data System (ADS)

    Bozinoski, Radoslav

    Significant research has been performed over the last several years on understanding the unsteady aerodynamics of various fluid flows. Much of this work has focused on quantifying the unsteady, three-dimensional flow field effects which have proven vital to the accurate prediction of many fluid and aerodynamic problems. Up until recently, engineers have predominantly relied on steady-state simulations to analyze the inherently three-dimensional ow structures that are prevalent in many of today's "real-world" problems. Increases in computational capacity and the development of efficient numerical methods can change this and allow for the solution of the unsteady Reynolds-Averaged Navier-Stokes (RANS) equations for practical three-dimensional aerodynamic applications. An integral part of this capability has been the performance and accuracy of the turbulence models coupled with advanced parallel computing techniques. This report begins with a brief literature survey of the role fully three-dimensional, unsteady, Navier-Stokes solvers have on the current state of numerical analysis. Next, the process of creating a baseline three-dimensional Multi-Block FLOw procedure called MBFLO3 is presented. Solutions for an inviscid circular arc bump, laminar at plate, laminar cylinder, and turbulent at plate are then presented. Results show good agreement with available experimental, numerical, and theoretical data. Scalability data for the parallel version of MBFLO3 is presented and shows efficiencies of 90% and higher for processes of no less than 100,000 computational grid points. Next, the description and implementation techniques used for several turbulence models are presented. Following the successful implementation of the URANS and DES procedures, the validation data for separated, non-reattaching flows over a NACA 0012 airfoil, wall-mounted hump, and a wing-body junction geometry are presented. Results for the NACA 0012 showed significant improvement in flow predictions

  1. Development of accurate waveform models for eccentric compact binaries with numerical relativity simulations

    NASA Astrophysics Data System (ADS)

    Huerta, Eliu; Agarwal, Bhanu; Chua, Alvin; George, Daniel; Haas, Roland; Hinder, Ian; Kumar, Prayush; Moore, Christopher; Pfeiffer, Harald

    2017-01-01

    We recently constructed an inspiral-merger-ringdown (IMR) waveform model to describe the dynamical evolution of compact binaries on eccentric orbits, and used this model to constrain the eccentricity with which the gravitational wave transients currently detected by LIGO could be effectively recovered with banks of quasi-circular templates. We now present the second generation of this model, which is calibrated using a large catalog of eccentric numerical relativity simulations. We discuss the new features of this model, and show that its enhance accuracy makes it a powerful tool to detect eccentric signals with LIGO.

  2. Accurate Simulation of MPPT Methods Performance When Applied to Commercial Photovoltaic Panels

    PubMed Central

    2015-01-01

    A new, simple, and quick-calculation methodology to obtain a solar panel model, based on the manufacturers' datasheet, to perform MPPT simulations, is described. The method takes into account variations on the ambient conditions (sun irradiation and solar cells temperature) and allows fast MPPT methods comparison or their performance prediction when applied to a particular solar panel. The feasibility of the described methodology is checked with four different MPPT methods applied to a commercial solar panel, within a day, and under realistic ambient conditions. PMID:25874262

  3. Accurate simulation of MPPT methods performance when applied to commercial photovoltaic panels.

    PubMed

    Cubas, Javier; Pindado, Santiago; Sanz-Andrés, Ángel

    2015-01-01

    A new, simple, and quick-calculation methodology to obtain a solar panel model, based on the manufacturers' datasheet, to perform MPPT simulations, is described. The method takes into account variations on the ambient conditions (sun irradiation and solar cells temperature) and allows fast MPPT methods comparison or their performance prediction when applied to a particular solar panel. The feasibility of the described methodology is checked with four different MPPT methods applied to a commercial solar panel, within a day, and under realistic ambient conditions.

  4. Accurate and efficient integration for molecular dynamics simulations at constant temperature and pressure.

    PubMed

    Lippert, Ross A; Predescu, Cristian; Ierardi, Douglas J; Mackenzie, Kenneth M; Eastwood, Michael P; Dror, Ron O; Shaw, David E

    2013-10-28

    In molecular dynamics simulations, control over temperature and pressure is typically achieved by augmenting the original system with additional dynamical variables to create a thermostat and a barostat, respectively. These variables generally evolve on timescales much longer than those of particle motion, but typical integrator implementations update the additional variables along with the particle positions and momenta at each time step. We present a framework that replaces the traditional integration procedure with separate barostat, thermostat, and Newtonian particle motion updates, allowing thermostat and barostat updates to be applied infrequently. Such infrequent updates provide a particularly substantial performance advantage for simulations parallelized across many computer processors, because thermostat and barostat updates typically require communication among all processors. Infrequent updates can also improve accuracy by alleviating certain sources of error associated with limited-precision arithmetic. In addition, separating the barostat, thermostat, and particle motion update steps reduces certain truncation errors, bringing the time-average pressure closer to its target value. Finally, this framework, which we have implemented on both general-purpose and special-purpose hardware, reduces software complexity and improves software modularity.

  5. Recent Results on the Accurate Measurements of the Dielectric Constant of Seawater at 1.413GHZ

    NASA Technical Reports Server (NTRS)

    Lang, R.H.; Tarkocin, Y.; Utku, C.; Le Vine, D.M.

    2008-01-01

    Measurements of the complex. dielectric constant of seawater at 30.00 psu, 35.00 psu and 38.27 psu over the temperature range from 5 C to 3 5 at 1.413 GHz are given and compared with the Klein-Swift results. A resonant cavity technique is used. The calibration constant used in the cavity perturbation formulas is determined experimentally using methanol and ethanediol (ethylene glycol) as reference liquids. Analysis of the data shows that the measurements are accurate to better than 1.0% in almost all cases studied.

  6. Simulating Expert Clinical Comprehension: Adapting Latent Semantic Analysis to Accurately Extract Clinical Concepts from Psychiatric Narrative

    PubMed Central

    Cohen, Trevor; Blatter, Brett; Patel, Vimla

    2008-01-01

    Cognitive studies reveal that less-than-expert clinicians are less able to recognize meaningful patterns of data in clinical narratives. Accordingly, psychiatric residents early in training fail to attend to information that is relevant to diagnosis and the assessment of dangerousness. This manuscript presents cognitively motivated methodology for the simulation of expert ability to organize relevant findings supporting intermediate diagnostic hypotheses. Latent Semantic Analysis is used to generate a semantic space from which meaningful associations between psychiatric terms are derived. Diagnostically meaningful clusters are modeled as geometric structures within this space and compared to elements of psychiatric narrative text using semantic distance measures. A learning algorithm is defined that alters components of these geometric structures in response to labeled training data. Extraction and classification of relevant text segments is evaluated against expert annotation, with system-rater agreement approximating rater-rater agreement. A range of biomedical informatics applications for these methods are suggested. PMID:18455483

  7. Recent advances in the practical and accurate calculation of core and valence XPS spectra of polymers: From interpretation to simulation?

    NASA Astrophysics Data System (ADS)

    Bureau, Christophe; Chong, Delano P.; Endo, Kazunaka; Delhalle, Joseph; Lecayon, Gérard; Le Moël, Alain

    1997-08-01

    Core and valence X-ray Photoelectron Spectroscopies (XPS) are routinely used to obtain information on the chemical composition, bonding and homogeneity of polymer surfaces. In spite of their apparent conceptual simplicity, Core and Valence Electron Binding Energies (CEBEs and VEBEs) a few electron-volts (eV) or fractions of an eV apart are difficult to interpret. We present some results obtained with various recent theoretical approaches. An emphasis is made on a procedure based on the Density Functional Theory (DFT) that enables the calculation of CEBEs and VEBEs which are in remarkable agreement with experiment. The method has been tested on numerous small (3-6 atoms) to fairly large (15-25 atoms) molecules, and shows an average absolute deviation with experiment of only 0.20 eV for CEBEs and 0.30 eV for VEBEs, i.e. compatible with the resolution of the best XPS experiments carried out at the moment. Besides the quality of its predictions, the procedure takes advantage of the speed and CPU time scaling of DFT as a function of system size: it is computationally tractable, even for surprisingly large systems such as polymers, and may be an interesting accurate alternative to interpret and simulate XPS-probing on real systems. We illustrate the usefullness and pitfalls of this approach in fundamental as well as applied fields such as in the study of Polyacrylonitrile (PAN), Polytetrafluoroethylene (PTFE), Polyvinyldifluoride (PVdF) and γ-Aminopropyltriethoxysilane (γ-APS, an adhesion promoter).

  8. Adsorption of lactate dehydrogenase enzyme on carbon nanotubes: how to get accurate results for the cytotoxicity of these nanomaterials.

    PubMed

    Forest, Valérie; Figarol, Agathe; Boudard, Delphine; Cottier, Michèle; Grosseau, Philippe; Pourchez, Jérémie

    2015-03-31

    Carbon nanotube (CNT) cytotoxicity is frequently investigated using in vitro classical toxicology assays. However, these cellular tests, usually based on the use of colorimetric or fluorimetric dyes, were designed for chemicals and may not be suitable for nanosized materials. Indeed, because of their unique physicochemical properties CNT can interfere with the assays and bias the results. To get accurate data and draw reliable conclusions, these artifacts should be carefully taken into account. The aim of this study was to evaluate qualitatively and quantitatively the interferences occurring between CNT and the commonly used lactate dehydrogenase (LDH) assay. Experiments under cell-free conditions were performed, and it was clearly demonstrated that artifacts occurred. They were due to the intrinsic absorbance of CNT on one hand and the adsorption of LDH at the CNT surface on the other hand. The adsorption of LDH on CNT was modeled and was found to fit the Langmuir model. The K(ads) and n(eq) constants were defined, allowing the correction of results obtained from cellular experiments to get more accurate data and lead to proper conclusions on the cytotoxicity of CNT.

  9. Simulation of optical diagnostics for crystal growth: models and results

    NASA Astrophysics Data System (ADS)

    Banish, Michele R.; Clark, Rodney L.; Kathman, Alan D.; Lawson, Shelah M.

    1991-12-01

    A computer simulation of a two-color holographic interferometric (TCHI) optical system was performed using a physical (wave) optics model. This model accurately simulates propagation through time-varying, 2-D or 3-D concentration and temperature fields as a wave phenomenon. The model calculates wavefront deformations that can be used to generate fringe patterns. This simulation modeled a proposed TriGlycine sulphate TGS flight experiment by propagating through the simplified onion-like refractive index distribution of the growing crystal and calculating the recorded wavefront deformation. The phase of this wavefront was used to generate sample interferograms that map index of refraction variation. Two such fringe patterns, generated at different wavelengths, were used to extract the original temperature and concentration field characteristics within the growth chamber. This proves feasibility for this TCHI crystal growth diagnostic technique. This simulation provides feedback to the experimental design process.

  10. Accurate laser guide star wavefront sensor simulation for the E-ELT first light adaptive optics module

    NASA Astrophysics Data System (ADS)

    Patti, Mauro; Schreiber, Laura; Arcidiacono, Carmelo; Bregoli, Giovanni; Ciliegi, Paolo; Diolaiti, Emiliano; Esposito, Simone; Feautrier, Philippe; Lombini, Matteo

    2016-07-01

    MAORY will be the multi-conjugate adaptive optics module for the E-ELT first light. The baseline is to operate wavefront sensing using 6 Sodium Laser Guide Stars and 3 Natural Guide Stars to solve intrinsic limitations of artificial beacons and to mitigate the impact of the sodium layer structure and variability. In particular, some critical components of MAORY require to be designed and dimensioned in order to reduce the spurious effects arising from the Sodium Layer density distribution and variation. The MAORY end-to-end simulation code has been designed to accurately model the Laser Guide Star image in the Shack-Hartmann wavefront sensor sub-apertures and to allow sodium profile temporal evolution. The fidelity with which the simulation code translates the sodium profiles in Laser Guide Star images at the wavefront sensor focal plane has been verified using a laboratory Prototype.

  11. Accurate Monte Carlo simulations on FCC and HCP Lennard-Jones solids at very low temperatures and high reduced densities up to 1.30.

    PubMed

    Adidharma, Hertanto; Tan, Sugata P

    2016-07-07

    Canonical Monte Carlo simulations on face-centered cubic (FCC) and hexagonal closed packed (HCP) Lennard-Jones (LJ) solids are conducted at very low temperatures (0.10 ≤ T(∗) ≤ 1.20) and high densities (0.96 ≤ ρ(∗) ≤ 1.30). A simple and robust method is introduced to determine whether or not the cutoff distance used in the simulation is large enough to provide accurate thermodynamic properties, which enables us to distinguish the properties of FCC from that of HCP LJ solids with confidence, despite their close similarities. Free-energy expressions derived from the simulation results are also proposed, not only to describe the properties of those individual structures but also the FCC-liquid, FCC-vapor, and FCC-HCP solid phase equilibria.

  12. Accurate Monte Carlo simulations on FCC and HCP Lennard-Jones solids at very low temperatures and high reduced densities up to 1.30

    NASA Astrophysics Data System (ADS)

    Adidharma, Hertanto; Tan, Sugata P.

    2016-07-01

    Canonical Monte Carlo simulations on face-centered cubic (FCC) and hexagonal closed packed (HCP) Lennard-Jones (LJ) solids are conducted at very low temperatures (0.10 ≤ T∗ ≤ 1.20) and high densities (0.96 ≤ ρ∗ ≤ 1.30). A simple and robust method is introduced to determine whether or not the cutoff distance used in the simulation is large enough to provide accurate thermodynamic properties, which enables us to distinguish the properties of FCC from that of HCP LJ solids with confidence, despite their close similarities. Free-energy expressions derived from the simulation results are also proposed, not only to describe the properties of those individual structures but also the FCC-liquid, FCC-vapor, and FCC-HCP solid phase equilibria.

  13. An accurate elasto-plastic frictional tangential force displacement model for granular-flow simulations: Displacement-driven formulation

    NASA Astrophysics Data System (ADS)

    Zhang, Xiang; Vu-Quoc, Loc

    2007-07-01

    We present in this paper the displacement-driven version of a tangential force-displacement (TFD) model that accounts for both elastic and plastic deformations together with interfacial friction occurring in collisions of spherical particles. This elasto-plastic frictional TFD model, with its force-driven version presented in [L. Vu-Quoc, L. Lesburg, X. Zhang. An accurate tangential force-displacement model for granular-flow simulations: contacting spheres with plastic deformation, force-driven formulation, Journal of Computational Physics 196(1) (2004) 298-326], is consistent with the elasto-plastic frictional normal force-displacement (NFD) model presented in [L. Vu-Quoc, X. Zhang. An elasto-plastic contact force-displacement model in the normal direction: displacement-driven version, Proceedings of the Royal Society of London, Series A 455 (1991) 4013-4044]. Both the NFD model and the present TFD model are based on the concept of additive decomposition of the radius of contact area into an elastic part and a plastic part. The effect of permanent indentation after impact is represented by a correction to the radius of curvature. The effect of material softening due to plastic flow is represented by a correction to the elastic moduli. The proposed TFD model is accurate, and is validated against nonlinear finite element analyses involving plastic flows in both the loading and unloading conditions. The proposed consistent displacement-driven, elasto-plastic NFD and TFD models are designed for implementation in computer codes using the discrete-element method (DEM) for granular-flow simulations. The model is shown to be accurate and is validated against nonlinear elasto-plastic finite-element analysis.

  14. Accurate Simulation of Resonance-Raman Spectra of Flexible Molecules: An Internal Coordinates Approach.

    PubMed

    Baiardi, Alberto; Bloino, Julien; Barone, Vincenzo

    2015-07-14

    The interpretation and analysis of experimental resonance-Raman (RR) spectra can be significantly facilitated by vibronic computations based on reliable quantum-mechanical (QM) methods. With the aim of improving the description of large and flexible molecules, our recent time-dependent formulation to compute vibrationally resolved electronic spectra, based on Cartesian coordinates, has been extended to support internal coordinates. A set of nonredundant delocalized coordinates is automatically generated from the molecular connectivity thanks to a new general and robust procedure. In order to validate our implementation, a series of molecules has been used as test cases. Among them, rigid systems show that normal modes based on Cartesian and delocalized internal coordinates provide equivalent results, but the latter set is much more convenient and reliable for systems characterized by strong geometric deformations associated with the electronic transition. The so-called Z-matrix internal coordinates, which perform well for chain molecules, are also shown to be poorly suited in the presence of cycles or nonstandard structures.

  15. Implementation and evaluation of the Level Set method: Towards efficient and accurate simulation of wet etching for microengineering applications

    NASA Astrophysics Data System (ADS)

    Montoliu, C.; Ferrando, N.; Gosálvez, M. A.; Cerdá, J.; Colom, R. J.

    2013-10-01

    The use of atomistic methods, such as the Continuous Cellular Automaton (CCA), is currently regarded as a computationally efficient and experimentally accurate approach for the simulation of anisotropic etching of various substrates in the manufacture of Micro-electro-mechanical Systems (MEMS). However, when the features of the chemical process are modified, a time-consuming calibration process needs to be used to transform the new macroscopic etch rates into a corresponding set of atomistic rates. Furthermore, changing the substrate requires a labor-intensive effort to reclassify most atomistic neighborhoods. In this context, the Level Set (LS) method provides an alternative approach where the macroscopic forces affecting the front evolution are directly applied at the discrete level, thus avoiding the need for reclassification and/or calibration. Correspondingly, we present a fully-operational Sparse Field Method (SFM) implementation of the LS approach, discussing in detail the algorithm and providing a thorough characterization of the computational cost and simulation accuracy, including a comparison to the performance by the most recent CCA model. We conclude that the SFM implementation achieves similar accuracy as the CCA method with less fluctuations in the etch front and requiring roughly 4 times less memory. Although SFM can be up to 2 times slower than CCA for the simulation of anisotropic etchants, it can also be up to 10 times faster than CCA for isotropic etchants. In addition, we present a parallel, GPU-based implementation (gSFM) and compare it to an optimized, multicore CPU version (cSFM), demonstrating that the SFM algorithm can be successfully parallelized and the simulation times consequently reduced, while keeping the accuracy of the simulations. Although modern multicore CPUs provide an acceptable option, the massively parallel architecture of modern GPUs is more suitable, as reflected by computational times for gSFM up to 7.4 times faster than

  16. Summarizing Simulation Results using Causally-relevant States

    PubMed Central

    Parikh, Nidhi; Marathe, Madhav; Swarup, Samarth

    2016-01-01

    As increasingly large-scale multiagent simulations are being implemented, new methods are becoming necessary to make sense of the results of these simulations. Even concisely summarizing the results of a given simulation run is a challenge. Here we pose this as the problem of simulation summarization: how to extract the causally-relevant descriptions of the trajectories of the agents in the simulation. We present a simple algorithm to compress agent trajectories through state space by identifying the state transitions which are relevant to determining the distribution of outcomes at the end of the simulation. We present a toy-example to illustrate the working of the algorithm, and then apply it to a complex simulation of a major disaster in an urban area. PMID:28042620

  17. Logrithmic current simulator generates electrical currents accurately between 10 to the minus 11 ampere to 10 to the minus 3 ampere

    NASA Technical Reports Server (NTRS)

    Wilson, J.

    1966-01-01

    Current generator accurately simulates electric currents in the range of 10 to the minus 11th power to 0.001 ampere. Compensation networks have been devised to improve the accuracy at the lower current levels.

  18. Visual Mapping of Sedimentary Facies Can Yield Accurate And Geomorphically Meaningful Results at Morphological Unit to River Segment Scales

    NASA Astrophysics Data System (ADS)

    Pasternack, G. B.; Wyrick, J. R.; Jackson, J. R.

    2014-12-01

    Long practiced in fisheries, visual substrate mapping of coarse-bedded rivers is eschewed by geomorphologists for inaccuracy and limited sizing data. Geomorphologists perform time-consuming measurements of surficial grains, with the few locations precluding spatially explicit mapping and analysis of sediment facies. Remote sensing works for bare land, but not vegetated or subaqueous sediments. As visual systems apply the log2 Wentworth scale made for sieving, they suffer from human inability to readily discern those classes. We hypothesized that size classes centered on the PDF of the anticipated sediment size distribution would enable field crews to accurately (i) identify presence/absence of each class in a facies patch and (ii) estimate the relative amount of each class to within 10%. We first tested 6 people using 14 measured samples with different mixtures. Next, we carried out facies mapping for ~ 37 km of the lower Yuba River in California. Finally, we tested the resulting data to see if it produced statistically significant hydraulic-sedimentary-geomorphic results. Presence/absence performance error was 0-4% for four people, 13% for one person, and 33% for one person. The last person was excluded from further effort. For the abundance estimation performance error was 1% for one person, 7-12% for three people, and 33% for one person. This last person was further trained and re-tested. We found that the samples easiest to visually quantify were unimodal and bimodal, while those most difficult had nearly equal amounts of each size. This confirms psychological studies showing that humans have a more difficult time quantifying abundances of subgroups when confronted with well-mixed groups. In the Yuba, mean grain size decreased downstream, as is typical for an alluvial river. When averaged by reach, mean grain size and bed slope were correlated with an r2 of 0.95. At the morphological unit (MU) scale, eight in-channel bed MU types had an r2 of 0.90 between mean

  19. Time Accurate Unsteady Simulation of the Stall Inception Process in the Compression System of a US Army Helicopter Gas Turbine Engine

    DTIC Science & Technology

    2004-06-01

    UNCLASSIFIED Defense Technical Information Center Compilation Part Notice ADP023843 TITLE: Time Accurate Unsteady Simulation of the Stall Inception...report: ADP023820 thru ADP023869 UNCLASSIFIED Time Accurate Unsteady Simulation of the Stall Inception Process in the Compression System of a US Army...surface ships, tanks, manned and Improved understanding of the stall inception process and unmanned fixed-wing and rotary-wing combat aircraft, how stall

  20. The VIIRS Ocean Data Simulator Enhancements and Results

    NASA Technical Reports Server (NTRS)

    Robinson, Wayne D.; Patt, Fredrick S.; Franz, Bryan A.; Turpie, Kevin R.; McClain, Charles R.

    2011-01-01

    The VIIRS Ocean Science Team (VOST) has been developing an Ocean Data Simulator to create realistic VIIRS SDR datasets based on MODIS water-leaving radiances. The simulator is helping to assess instrument performance and scientific processing algorithms. Several changes were made in the last two years to complete the simulator and broaden its usefulness. The simulator is now fully functional and includes all sensor characteristics measured during prelaunch testing, including electronic and optical crosstalk influences, polarization sensitivity, and relative spectral response. Also included is the simulation of cloud and land radiances to make more realistic data sets and to understand their important influence on nearby ocean color data. The atmospheric tables used in the processing, including aerosol and Rayleigh reflectance coefficients, have been modeled using VIIRS relative spectral responses. The capabilities of the simulator were expanded to work in an unaggregated sample mode and to produce scans with additional samples beyond the standard scan. These features improve the capability to realistically add artifacts which act upon individual instrument samples prior to aggregation and which may originate from beyond the actual scan boundaries. The simulator was expanded to simulate all 16 M-bands and the EDR processing was improved to use these bands to make an SST product. The simulator is being used to generate global VIIRS data from and in parallel with the MODIS Aqua data stream. Studies have been conducted using the simulator to investigate the impact of instrument artifacts. This paper discusses the simulator improvements and results from the artifact impact studies.

  1. Can Community Health Workers Report Accurately on Births and Deaths? Results of Field Assessments in Ethiopia, Malawi and Mali

    PubMed Central

    Silva, Romesh; Amouzou, Agbessi; Munos, Melinda; Marsh, Andrew; Hazel, Elizabeth; Victora, Cesar; Black, Robert; Bryce, Jennifer

    2016-01-01

    Introduction Most low-income countries lack complete and accurate vital registration systems. As a result, measures of under-five mortality rates rely mostly on household surveys. In collaboration with partners in Ethiopia, Ghana, Malawi, and Mali, we assessed the completeness and accuracy of reporting of births and deaths by community-based health workers, and the accuracy of annualized under-five mortality rate estimates derived from these data. Here we report on results from Ethiopia, Malawi and Mali. Method In all three countries, community health workers (CHWs) were trained, equipped and supported to report pregnancies, births and deaths within defined geographic areas over a period of at least fifteen months. In-country institutions collected these data every month. At each study site, we administered a full birth history (FBH) or full pregnancy history (FPH), to women of reproductive age via a census of households in Mali and via household surveys in Ethiopia and Malawi. Using these FBHs/FPHs as a validation data source, we assessed the completeness of the counts of births and deaths and the accuracy of under-five, infant, and neonatal mortality rates from the community-based method against the retrospective FBH/FPH for rolling twelve-month periods. For each method we calculated total cost, average annual cost per 1,000 population, and average cost per vital event reported. Results On average, CHWs submitted monthly vital event reports for over 95 percent of catchment areas in Ethiopia and Malawi, and for 100 percent of catchment areas in Mali. The completeness of vital events reporting by CHWs varied: we estimated that 30%-90% of annualized expected births (i.e. the number of births estimated using a FPH) were documented by CHWs and 22%-91% of annualized expected under-five deaths were documented by CHWs. Resulting annualized under-five mortality rates based on the CHW vital events reporting were, on average, under-estimated by 28% in Ethiopia, 32% in

  2. Measurement and Simulation Results of Ti Coated Microwave Absorber

    SciTech Connect

    Sun, Ding; McGinnis, Dave; /Fermilab

    1998-11-01

    When microwave absorbers are put in a waveguide, a layer of resistive coating can change the distribution of the E-M fields and affect the attenuation of the signal within the microwave absorbers. In order to study such effect, microwave absorbers (TT2-111) were coated with titanium thin film. This report is a document on the coating process and measurement results. The measurement results have been used to check the simulation results from commercial software HFSS (High Frequency Structure Simulator.)

  3. Electron-cloud simulation results for the SPS and recent results for the LHC

    SciTech Connect

    Furman, M.A.; Pivi, M.T.F.

    2002-06-19

    We present an update of computer simulation results for some features of the electron cloud at the Large Hadron Collider (LHC) and recent simulation results for the Super Proton Synchrotron (SPS). We focus on the sensitivity of the power deposition on the LHC beam screen to the emitted electron spectrum, which we study by means of a refined secondary electron (SE) emission model recently included in our simulation code.

  4. Electron-cloud simulation results for the PSR and SNS

    SciTech Connect

    Pivi, M.; Furman, M.A.

    2002-07-08

    We present recent simulation results for the main features of the electron cloud in the storage ring of the Spallation Neutron Source (SNS) at Oak Ridge, and updated results for the Proton Storage Ring (PSR) at Los Alamos. In particular, a complete refined model for the secondary emission process including the so called true secondary, rediffused and backscattered electrons has been included in the simulation code.

  5. Accurate path integral molecular dynamics simulation of ab-initio water at near-zero added cost

    NASA Astrophysics Data System (ADS)

    Elton, Daniel; Fritz, Michelle; Soler, José; Fernandez-Serra, Marivi

    It is now established that nuclear quantum motion plays an important role in determining water's structure and dynamics. These effects are important to consider when evaluating DFT functionals and attempting to develop better ones for water. The standard way of treating nuclear quantum effects, path integral molecular dynamics (PIMD), multiplies the number of energy/force calculations by the number of beads, which is typically 32. Here we introduce a method whereby PIMD can be incorporated into a DFT molecular dynamics simulation at virtually zero cost. The method is based on the cluster (many body) expansion of the energy. We first subtract the DFT monomer energies, using a custom DFT-based monomer potential energy surface. The evolution of the PIMD beads is then performed using only the more-accurate Partridge-Schwenke monomer energy surface. The DFT calculations are done using the centroid positions. Various bead thermostats can be employed to speed up the sampling of the quantum ensemble. The method bears some resemblance to multiple timestep algorithms and other schemes used to speed up PIMD with classical force fields. We show that our method correctly captures some of key effects of nuclear quantum motion on both the structure and dynamics of water. We acknowledge support from DOE Award No. DE-FG02-09ER16052 (D.E.) and DOE Early Career Award No. DE-SC0003871 (M.V.F.S.).

  6. MIA computer simulation test results report. [space shuttle avionics

    NASA Technical Reports Server (NTRS)

    Unger, G. E.

    1974-01-01

    Results of the first noise susceptibility computer simulation tests of the complete MIA receiver analytical model are presented. Computer simulation tests were conducted with both Gaussian and pulse noise inputs. The results of the Gaussian noise tests were compared to results predicted previously and were found to be in substantial agreement. The results of the pulse noise tests will be compared to the results of planned analogous tests in the Data Bus Evaluation Laboratory at a later time. The MIA computer model is considered to be fully operational at this time.

  7. Physalis method for heterogeneous mixtures of dielectrics and conductors: Accurately simulating one million particles using a PC

    NASA Astrophysics Data System (ADS)

    Liu, Qianlong

    2011-09-01

    Prosperetti's seminal Physalis method, an Immersed Boundary/spectral method, had been used extensively to investigate fluid flows with suspended solid particles. Its underlying idea of creating a cage and using a spectral general analytical solution around a discontinuity in a surrounding field as a computational mechanism to enable the accommodation of physical and geometric discontinuities is a general concept, and can be applied to other problems of importance to physics, mechanics, and chemistry. In this paper we provide a foundation for the application of this approach to the determination of the distribution of electric charge in heterogeneous mixtures of dielectrics and conductors. The proposed Physalis method is remarkably accurate and efficient. In the method, a spectral analytical solution is used to tackle the discontinuity and thus the discontinuous boundary conditions at the interface of two media are satisfied exactly. Owing to the hybrid finite difference and spectral schemes, the method is spectrally accurate if the modes are not sufficiently resolved, while higher than second-order accurate if the modes are sufficiently resolved, for the solved potential field. Because of the features of the analytical solutions, the derivative quantities of importance, such as electric field, charge distribution, and force, have the same order of accuracy as the solved potential field during postprocessing. This is an important advantage of the Physalis method over other numerical methods involving interpolation, differentiation, and integration during postprocessing, which may significantly degrade the accuracy of the derivative quantities of importance. The analytical solutions enable the user to use relatively few mesh points to accurately represent the regions of discontinuity. In addition, the spectral convergence and a linear relationship between the cost of computer memory/computation and particle numbers results in a very efficient method. In the present

  8. Time-accurate unsteady flow simulations supporting the SRM T+68-second pressure spike anomaly investigation (STS-54B)

    NASA Astrophysics Data System (ADS)

    Dougherty, N. S.; Burnette, D. W.; Holt, J. B.; Matienzo, Jose

    1993-07-01

    Time-accurate unsteady flow simulations are being performed supporting the SRM T+68sec pressure 'spike' anomaly investigation. The anomaly occurred in the RH SRM during the STS-54 flight (STS-54B) but not in the LH SRM (STS-54A) causing a momentary thrust mismatch approaching the allowable limit at that time into the flight. Full-motor internal flow simulations using the USA-2D axisymmetric code are in progress for the nominal propellant burn-back geometry and flow conditions at T+68-sec--Pc = 630 psi, gamma = 1.1381, T(sub c) = 6200 R, perfect gas without aluminum particulate. In a cooperative effort with other investigation team members, CFD-derived pressure loading on the NBR and castable inhibitors was used iteratively to obtain nominal deformed geometry of each inhibitor, and the deformed (bent back) inhibitor geometry was entered into this model. Deformed geometry was computed using structural finite-element models. A solution for the unsteady flow has been obtained for the nominal flow conditions (existing prior to the occurrence of the anomaly) showing sustained standing pressure oscillations at nominally 14.5 Hz in the motor IL acoustic mode that flight and static test data confirm to be normally present at this time. Average mass flow discharged from the nozzle was confirmed to be the nominal expected (9550 lbm/sec). The local inlet boundary condition is being perturbed at the location of the presumed reconstructed anomaly as identified by interior ballistics performance specialist team members. A time variation in local mass flow is used to simulate sudden increase in burning area due to localized propellant grain cracks. The solution will proceed to develop a pressure rise (proportional to total mass flow rate change squared). The volume-filling time constant (equivalent to 0.5 Hz) comes into play in shaping the rise rate of the developing pressure 'spike' as it propagates at the speed of sound in both directions to the motor head end and nozzle. The

  9. Full vectorial simulation for characterizing loss or gain in optical devices with an accurate and automated finite-element program.

    PubMed

    Tzolov, V P; Fontaine, M; Sewell, G; Delâge, A

    1997-01-20

    An efficient, accurate, and automated vectorial finite-element method is described to characterize arbitrarily shaped optical devices having loss or gain properties. The method can be easily implemented inside the pde 2 d software environment, where an interactive session allows the user to specify the problem in a easy-to-use format. For the method to be validated, modal dispersion characteristics of high loss metal-coated optical fibers that have recently been used in applications in scanning near-field optical microscopy are presented and compared with results obtained with two vectorial approaches, i.e., the field expansion and the multiple-multipole methods. These results clearly illustrate the flexibility, accuracy, and ease of implementation of the method.

  10. Experimental and simulational result multipactors in 112 MHz QWR injector

    SciTech Connect

    Xin, T.; Ben-Zvi, I.; Belomestnykh, S.; Brutus, J. C.; Skaritka, J.; Wu, Q.; Xiao, B.

    2015-05-03

    The first RF commissioning of 112 MHz QWR superconducting electron gun was done in late 2014. The coaxial Fundamental Power Coupler (FPC) and Cathode Stalk (stalk) were installed and tested for the first time. During this experiment, we observed several multipacting barriers at different gun voltage levels. The simulation work was done within the same range. The comparison between the experimental observation and the simulation results are presented in this paper. The observations during the test are consisted with the simulation predictions. We were able to overcome most of the multipacting barriers and reach 1.8 MV gun voltage under pulsed mode after several round of conditioning processes.

  11. Aerosol kinetic code "AERFORM": Model, validation and simulation results

    NASA Astrophysics Data System (ADS)

    Gainullin, K. G.; Golubev, A. I.; Petrov, A. M.; Piskunov, V. N.

    2016-06-01

    The aerosol kinetic code "AERFORM" is modified to simulate droplet and ice particle formation in mixed clouds. The splitting method is used to calculate condensation and coagulation simultaneously. The method is calibrated with analytic solutions of kinetic equations. Condensation kinetic model is based on cloud particle growth equation, mass and heat balance equations. The coagulation kinetic model includes Brownian, turbulent and precipitation effects. The real values are used for condensation and coagulation growth of water droplets and ice particles. The model and the simulation results for two full-scale cloud experiments are presented. The simulation model and code may be used autonomously or as an element of another code.

  12. Cardiovascular system and microgravity simulation and inflight results

    NASA Astrophysics Data System (ADS)

    Pottier, J. M.; Patat, F.; Arbeille, P.; Pourcelot, L.; Massabuau, P.; Guell, A.; Gharib, C.

    Main results of cardiovascular investigation, performed with ultrasound methods during the common French/Soviet flight aboard Salyut VII in June 1982, are compared to variations of the same parameters studied during ground-based simulations on the same subject or observed by other investigators during various ground-based experiences. The antiorthostatic bed rest simulation partly reproduces microgravity conditions and seems to be better adaptated to cardiac hemodynamics, despite some differences, and to the cerebral circulation, than to the inferior limb circulation.

  13. Accurate Ab Initio Quantum Mechanics Simulations of Bi2Se3 and Bi2Te3 Topological Insulator Surfaces.

    PubMed

    Crowley, Jason M; Tahir-Kheli, Jamil; Goddard, William A

    2015-10-01

    It has been established experimentally that Bi2Te3 and Bi2Se3 are topological insulators, with zero band gap surface states exhibiting linear dispersion at the Fermi energy. Standard density functional theory (DFT) methods such as PBE lead to large errors in the band gaps for such strongly correlated systems, while more accurate GW methods are too expensive computationally to apply to the thin films studied experimentally. We show here that the hybrid B3PW91 density functional yields GW-quality results for these systems at a computational cost comparable to PBE. The efficiency of our approach stems from the use of Gaussian basis functions instead of plane waves or augmented plane waves. This remarkable success without empirical corrections of any kind opens the door to computational studies of real chemistry involving the topological surface state, and our approach is expected to be applicable to other semiconductors with strong spin-orbit coupling.

  14. Hyper-X Stage Separation: Simulation Development and Results

    NASA Technical Reports Server (NTRS)

    Reubush, David E.; Martin, John G.; Robinson, Jeffrey S.; Bose, David M.; Strovers, Brian K.

    2001-01-01

    This paper provides an overview of stage separation simulation development and results for NASA's Hyper-X program; a focused hypersonic technology effort designed to move hypersonic, airbreathing vehicle technology from the laboratory environment to the flight environment. This paper presents an account of the development of the current 14 degree of freedom stage separation simulation tool (SepSim) and results from use of the tool in a Monte Carlo analysis to evaluate the risk of failure for the separation event. Results from use of the tool show that there is only a very small risk of failure in the separation event.

  15. A streamline splitting pore-network approach for computationally inexpensive and accurate simulation of transport in porous media

    SciTech Connect

    Mehmani, Yashar; Oostrom, Martinus; Balhoff, Matthew

    2014-03-20

    Several approaches have been developed in the literature for solving flow and transport at the pore-scale. Some authors use a direct modeling approach where the fundamental flow and transport equations are solved on the actual pore-space geometry. Such direct modeling, while very accurate, comes at a great computational cost. Network models are computationally more efficient because the pore-space morphology is approximated. Typically, a mixed cell method (MCM) is employed for solving the flow and transport system which assumes pore-level perfect mixing. This assumption is invalid at moderate to high Peclet regimes. In this work, a novel Eulerian perspective on modeling flow and transport at the pore-scale is developed. The new streamline splitting method (SSM) allows for circumventing the pore-level perfect mixing assumption, while maintaining the computational efficiency of pore-network models. SSM was verified with direct simulations and excellent matches were obtained against micromodel experiments across a wide range of pore-structure and fluid-flow parameters. The increase in the computational cost from MCM to SSM is shown to be minimal, while the accuracy of SSM is much higher than that of MCM and comparable to direct modeling approaches. Therefore, SSM can be regarded as an appropriate balance between incorporating detailed physics and controlling computational cost. The truly predictive capability of the model allows for the study of pore-level interactions of fluid flow and transport in different porous materials. In this paper, we apply SSM and MCM to study the effects of pore-level mixing on transverse dispersion in 3D disordered granular media.

  16. Duplicate portion sampling combined with spectrophotometric analysis affords the most accurate results when assessing daily dietary phosphorus intake.

    PubMed

    Navarro-Alarcon, Miguel; Zambrano, Esmeralda; Moreno-Montoro, Miriam; Agil, Ahmad; Olalla, Manuel

    2012-08-01

    The assessment of daily dietary phosphorus (P) intake is a major concern in human nutrition because of its relationship with Ca and Mg metabolism and osteoporosis. Within this context, we hypothesized that several of the methods available for the assessment of daily dietary intake of P are equally accurate and reliable, although few studies have been conducted to confirm this. The aim of this study then was to evaluate daily dietary P intake, which we did by 3 methods: duplicate portion sampling of 108 hospital meals, combined either with spectrophotometric analysis or the use of food composition tables, and 24-hour dietary recall for 3 consecutive days plus the use of food composition tables. The mean P daily dietary intakes found were 1106 ± 221, 1480 ± 221, and 1515 ± 223 mg/d, respectively. Daily dietary intake of P determined by spectrophotometric analysis was significantly lower (P < .001) and closer to dietary reference intakes for adolescents aged from 14 to 18 years (88.5%) and adult subjects (158.1%) compared with the other 2 methods. Duplicate portion sampling with P analysis takes into account the influence of technological and cooking processes on the P content of foods and meals and therefore afforded the most accurate and reliable P daily dietary intakes. The use of referred food composition tables overestimated daily dietary P intake. No adverse effects in relation to P nutrition (deficiencies or toxic effects) were encountered.

  17. Advanced Thermal Simulator Testing: Thermal Analysis and Test Results

    NASA Technical Reports Server (NTRS)

    Bragg-Sitton, Shannon M.; Dickens, Ricky; Dixon, David; Reid, Robert; Adams, Mike; Davis, Joe

    2008-01-01

    Work at the NASA Marshall Space Flight Center seeks to develop high fidelity, electrically heated thermal simulators that represent fuel elements in a nuclear reactor design to support non-nuclear testing applicable to the development of a space nuclear power or propulsion system. Comparison between the fuel pins and thermal simulators is made at the outer fuel clad surface, which corresponds to the outer sheath surface in the thermal simulator. The thermal simulators that are currently being tested correspond to a SNAP derivative reactor design that could be applied for Lunar surface power. These simulators are designed to meet the geometric and power requirements of a proposed surface power reactor design, accommodate testing of various axial power profiles, and incorporate imbedded instrumentation. This paper reports the results of thermal simulator analysis and testing in a bare element configuration, which does not incorporate active heat removal, and testing in a water-cooled calorimeter designed to mimic the heat removal that would be experienced in a reactor core.

  18. Advanced Thermal Simulator Testing: Thermal Analysis and Test Results

    SciTech Connect

    Bragg-Sitton, Shannon M.; Dickens, Ricky; Dixon, David; Reid, Robert; Adams, Mike; Davis, Joe

    2008-01-21

    Work at the NASA Marshall Space Flight Center seeks to develop high fidelity, electrically heated thermal simulators that represent fuel elements in a nuclear reactor design to support non-nuclear testing applicable to the potential development of a space nuclear power or propulsion system. Comparison between the fuel pins and thermal simulators is made at the outer fuel clad surface, which corresponds to the outer sheath surface in the thermal simulator. The thermal simulators that are currently being tested correspond to a liquid metal cooled reactor design that could be applied for Lunar surface power. These simulators are designed to meet the geometric and power requirements of a proposed surface power reactor design, accommodate testing of various axial power profiles, and incorporate imbedded instrumentation. This paper reports the results of thermal simulator analysis and testing in a bare element configuration, which does not incorporate active heat removal, and testing in a water-cooled calorimeter designed to mimic the heat removal that would be experienced in a reactor core.

  19. Relationships between driving simulator performance and driving test results.

    PubMed

    de Winter, J C F; de Groot, S; Mulder, M; Wieringa, P A; Dankelman, J; Mulder, J A

    2009-02-01

    This article is considered relevant because: 1) car driving is an everyday and safety-critical task; 2) simulators are used to an increasing extent for driver training (related topics: training, virtual reality, human-machine interaction); 3) the article addresses relationships between performance in the simulator and driving test results--a relevant topic for those involved in driver training and the virtual reality industries; 4) this article provides new insights about individual differences in young drivers' behaviour. Simulators are being used to an increasing extent for driver training, allowing for the possibility of collecting objective data on driver proficiency under standardised conditions. However, relatively little is known about how learner drivers' simulator measures relate to on-road driving. This study proposes a theoretical framework that quantifies driver proficiency in terms of speed of task execution, violations and errors. This study investigated the relationships between these three measures of learner drivers' (n=804) proficiency during initial simulation-based training and the result of the driving test on the road, occurring an average of 6 months later. A higher chance of passing the driving test the first time was associated with making fewer steering errors on the simulator and could be predicted in regression analysis with a correlation of 0.18. Additionally, in accordance with the theoretical framework, a shorter duration of on-road training corresponded with faster task execution, fewer violations and fewer steering errors (predictive correlation 0.45). It is recommended that researchers conduct more large-scale studies into the reliability and validity of simulator measures and on-road driving tests.

  20. Results from Binary Black Hole Simulations in Astrophysics Applications

    NASA Technical Reports Server (NTRS)

    Baker, John G.

    2007-01-01

    Present and planned gravitational wave observatories are opening a new astronomical window to the sky. A key source of gravitational waves is the merger of two black holes. The Laser Interferometer Space Antenna (LISA), in particular, is expected to observe these events with signal-to-noise ratio's in the thousands. To fully reap the scientific benefits of these observations requires a detailed understanding, based on numerical simulations, of the predictions of General Relativity for the waveform signals. New techniques for simulating binary black hole mergers, introduced two years ago, have led to dramatic advances in applied numerical simulation work. Over the last two years, numerical relativity researchers have made tremendous strides in understanding the late stages of binary black hole mergers. Simulations have been applied to test much of the basic physics of binary black hole interactions, showing robust results for merger waveform predictions, and illuminating such phenomena as spin-precession. Calculations have shown that merging systems can be kicked at up to 2500 km/s by the thrust from asymmetric emission. Recently, long lasting simulations of ten or more orbits allow tests of post-Newtonian (PN) approximation results for radiation from the last orbits of the binary's inspiral. Already, analytic waveform models based PN techniques with incorporated information from numerical simulations may be adequate for observations with current ground based observatories. As new advances in simulations continue to rapidly improve our theoretical understanding of the systems, it seems certain that high-precision predictions will be available in time for LISA and other advanced ground-based instruments. Future gravitational wave observatories are expected to make precision.

  1. Simulation results for the electron-cloud at the PSR

    SciTech Connect

    Furman, M.A.; Pivi, M.

    2001-06-26

    We present a first set of computer simulations for the main features of the electron cloud at the Proton Storage Ring (PSR), particularly its energy spectrum. We compare our results with recent measurements, which have been obtained by means of dedicated probes.

  2. Creation of an idealized nasopharynx geometry for accurate computational fluid dynamics simulations of nasal airflow in patient-specific models lacking the nasopharynx anatomy.

    PubMed

    A T Borojeni, Azadeh; Frank-Ito, Dennis O; Kimbell, Julia S; Rhee, John S; Garcia, Guilherme J M

    2016-08-15

    Virtual surgery planning based on computational fluid dynamics (CFD) simulations has the potential to improve surgical outcomes for nasal airway obstruction patients, but the benefits of virtual surgery planning must outweigh the risks of radiation exposure. Cone beam computed tomography (CT) scans represent an attractive imaging modality for virtual surgery planning due to lower costs and lower radiation exposures compared with conventional CT scans. However, to minimize the radiation exposure, the cone beam CT sinusitis protocol sometimes images only the nasal cavity, excluding the nasopharynx. The goal of this study was to develop an idealized nasopharynx geometry for accurate representation of outlet boundary conditions when the nasopharynx geometry is unavailable. Anatomically accurate models of the nasopharynx created from 30 CT scans were intersected with planes rotated at different angles to obtain an average geometry. Cross sections of the idealized nasopharynx were approximated as ellipses with cross-sectional areas and aspect ratios equal to the average in the actual patient-specific models. CFD simulations were performed to investigate whether nasal airflow patterns were affected when the CT-based nasopharynx was replaced by the idealized nasopharynx in 10 nasal airway obstruction patients. Despite the simple form of the idealized geometry, all biophysical variables (nasal resistance, airflow rate, and heat fluxes) were very similar in the idealized vs patient-specific models. The results confirmed the expectation that the nasopharynx geometry has a minimal effect in the nasal airflow patterns during inspiration. The idealized nasopharynx geometry will be useful in future CFD studies of nasal airflow based on medical images that exclude the nasopharynx.

  3. DSS1/DSS2 astrometry for 1101 First Byurakan Survey blue stellar objects: Accurate positions and other results

    NASA Astrophysics Data System (ADS)

    Mickaelian, A. M.

    2004-10-01

    Accurate measurements of the positions of 1101 First Byurakan Survey (FBS) blue stellar objects (the Second part of the FBS) have been carried out on the DSS1 and DSS2 (red and blue images). To establish the accuracy of the DSS1 and DSS2, measurements have been made for 153 AGN for which absolute VLBI coordinates have been published. The rms errors are: 0.45 arcsec for DSS1, 0.33 arcsec for DSS2 red, and 0.59 arcsec for DSS2 blue in each coordinate, the corresponding total positional errors being 0.64 arcsec, 0.46 arcsec, and 0.83 arcsec, respectively. The highest accuracy (0.42 arcsec) is obtained by weighted averaging of the DSS1 and DSS2 red positions. It is shown that by using all three DSS images accidental errors can be significantly reduced. The comparison of DSS2 and DSS1 images made it possible to reveal positional differences and proper motions for 78 objects (for 62 of these for the first time), including new high-probability candidate white dwarfs, and to find objects showing strong variability, i.e. high-probability candidate cataclysmic variables. Table 1 is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/426/367

  4. Direct Numerical Simulation of Liquid Nozzle Spray with Comparison to Shadowgraphy and X-Ray Computed Tomography Experimental Results

    NASA Astrophysics Data System (ADS)

    van Poppel, Bret; Owkes, Mark; Nelson, Thomas; Lee, Zachary; Sowell, Tyler; Benson, Michael; Vasquez Guzman, Pablo; Fahrig, Rebecca; Eaton, John; Kurman, Matthew; Kweon, Chol-Bum; Bravo, Luis

    2014-11-01

    In this work, we present high-fidelity Computational Fluid Dynamics (CFD) results of liquid fuel injection from a pressure-swirl atomizer and compare the simulations to experimental results obtained using both shadowgraphy and phase-averaged X-ray computed tomography (CT) scans. The CFD and experimental results focus on the dense near-nozzle region to identify the dominant mechanisms of breakup during primary atomization. Simulations are performed using the NGA code of Desjardins et al (JCP 227 (2008)) and employ the volume of fluid (VOF) method proposed by Owkes and Desjardins (JCP 270 (2013)), a second order accurate, un-split, conservative, three-dimensional VOF scheme providing second order density fluxes and capable of robust and accurate high density ratio simulations. Qualitative features and quantitative statistics are assessed and compared for the simulation and experimental results, including the onset of atomization, spray cone angle, and drop size and distribution.

  5. A novel, integrated PET-guided MRS technique resulting in more accurate initial diagnosis of high-grade glioma.

    PubMed

    Kim, Ellen S; Satter, Martin; Reed, Marilyn; Fadell, Ronald; Kardan, Arash

    2016-06-01

    Glioblastoma multiforme (GBM) is the most common and lethal malignant glioma in adults. Currently, the modality of choice for diagnosing brain tumor is high-resolution magnetic resonance imaging (MRI) with contrast, which provides anatomic detail and localization. Studies have demonstrated, however, that MRI may have limited utility in delineating the full tumor extent precisely. Studies suggest that MR spectroscopy (MRS) can also be used to distinguish high-grade from low-grade gliomas. However, due to operator dependent variables and the heterogeneous nature of gliomas, the potential for error in diagnostic accuracy with MRS is a concern. Positron emission tomography (PET) imaging with (11)C-methionine (MET) and (18)F-fluorodeoxyglucose (FDG) has been shown to add additional information with respect to tumor grade, extent, and prognosis based on the premise of biochemical changes preceding anatomic changes. Combined PET/MRS is a technique that integrates information from PET in guiding the location for the most accurate metabolic characterization of a lesion via MRS. We describe a case of glioblastoma multiforme in which MRS was initially non-diagnostic for malignancy, but when MRS was repeated with PET guidance, demonstrated elevated choline/N-acetylaspartate (Cho/NAA) ratio in the right parietal mass consistent with a high-grade malignancy. Stereotactic biopsy, followed by PET image-guided resection, confirmed the diagnosis of grade IV GBM. To our knowledge, this is the first reported case of an integrated PET/MRS technique for the voxel placement of MRS. Our findings suggest that integrated PET/MRS may potentially improve diagnostic accuracy in high-grade gliomas.

  6. Simulating the Cranfield geological carbon sequestration project with high-resolution static models and an accurate equation of state

    SciTech Connect

    Soltanian, Mohamad Reza; Amooie, Mohammad Amin; Cole, David R.; Graham, David E.; Hosseini, Seyyed Abolfazl; Hovorka, Susan; Pfiffner, Susan M.; Phelps, Tommy Joe; Moortgat, Joachim

    2016-10-11

    In this study, a field-scale carbon dioxide (CO2) injection pilot project was conducted as part of the Southeast Regional Sequestration Partnership (SECARB) at Cranfield, Mississippi. We present higher-order finite element simulations of the compositional two-phase CO2-brine flow and transport during the experiment. High- resolution static models of the formation geology in the Detailed Area Study (DAS) located below the oil- water contact (brine saturated) are used to capture the impact of connected flow paths on breakthrough times in two observation wells. Phase behavior is described by the cubic-plus-association (CPA) equation of state, which takes into account the polar nature of water molecules. Parameter studies are performed to investigate the importance of Fickian diffusion, permeability heterogeneity, relative permeabilities, and capillarity. Simulation results for the pressure response in the injection well and the CO2 breakthrough times at the observation wells show good agreement with the field data. For the high injection rates and short duration of the experiment, diffusion is relatively unimportant (high P clet numbers), while relative permeabilities have a profound impact on the pressure response. High-permeability pathways, created by fluvial deposits, strongly affect the CO2 transport and highlight the importance of properly characterizing the formation heterogeneity in future carbon sequestration projects.

  7. Simulating the Cranfield geological carbon sequestration project with high-resolution static models and an accurate equation of state

    DOE PAGES

    Soltanian, Mohamad Reza; Amooie, Mohammad Amin; Cole, David R.; ...

    2016-10-11

    In this study, a field-scale carbon dioxide (CO2) injection pilot project was conducted as part of the Southeast Regional Sequestration Partnership (SECARB) at Cranfield, Mississippi. We present higher-order finite element simulations of the compositional two-phase CO2-brine flow and transport during the experiment. High- resolution static models of the formation geology in the Detailed Area Study (DAS) located below the oil- water contact (brine saturated) are used to capture the impact of connected flow paths on breakthrough times in two observation wells. Phase behavior is described by the cubic-plus-association (CPA) equation of state, which takes into account the polar nature ofmore » water molecules. Parameter studies are performed to investigate the importance of Fickian diffusion, permeability heterogeneity, relative permeabilities, and capillarity. Simulation results for the pressure response in the injection well and the CO2 breakthrough times at the observation wells show good agreement with the field data. For the high injection rates and short duration of the experiment, diffusion is relatively unimportant (high P clet numbers), while relative permeabilities have a profound impact on the pressure response. High-permeability pathways, created by fluvial deposits, strongly affect the CO2 transport and highlight the importance of properly characterizing the formation heterogeneity in future carbon sequestration projects.« less

  8. First results of coupled IPS/NIMROD/GENRAY simulations

    NASA Astrophysics Data System (ADS)

    Jenkins, Thomas; Kruger, S. E.; Held, E. D.; Harvey, R. W.; Elwasif, W. R.; Schnack, D. D.

    2010-11-01

    The Integrated Plasma Simulator (IPS) framework, developed by the SWIM Project Team, facilitates self-consistent simulations of complicated plasma behavior via the coupling of various codes modeling different spatial/temporal scales in the plasma. Here, we apply this capability to investigate the stabilization of tearing modes by ECCD. Under IPS control, the NIMROD code (MHD) evolves fluid equations to model bulk plasma behavior, while the GENRAY code (RF) calculates the self-consistent propagation and deposition of RF power in the resulting plasma profiles. GENRAY data is then used to construct moments of the quasilinear diffusion tensor (induced by the RF) which influence the dynamics of momentum/energy evolution in NIMROD's equations. We present initial results from these coupled simulations and demonstrate that they correctly capture the physics of magnetic island stabilization [Jenkins et al, PoP 17, 012502 (2010)] in the low-beta limit. We also discuss the process of code verification in these simulations, demonstrating good agreement between NIMROD and GENRAY predictions for the flux-surface-averaged, RF-induced currents. An overview of ongoing model development (synthetic diagnostics/plasma control systems; neoclassical effects; etc.) is also presented. Funded by US DoE.

  9. Numerical Simulation of Natural Convection of a Nanofluid in an Inclined Heated Enclosure Using Two-Phase Lattice Boltzmann Method: Accurate Effects of Thermophoresis and Brownian Forces.

    PubMed

    Ahmed, Mahmoud; Eslamian, Morteza

    2015-12-01

    Laminar natural convection in differentially heated (β = 0°, where β is the inclination angle), inclined (β = 30° and 60°), and bottom-heated (β = 90°) square enclosures filled with a nanofluid is investigated, using a two-phase lattice Boltzmann simulation approach. The effects of the inclination angle on Nu number and convection heat transfer coefficient are studied. The effects of thermophoresis and Brownian forces which create a relative drift or slip velocity between the particles and the base fluid are included in the simulation. The effect of thermophoresis is considered using an accurate and quantitative formula proposed by the authors. Some of the existing results on natural convection are erroneous due to using wrong thermophoresis models or simply ignoring the effect. Here we show that thermophoresis has a considerable effect on heat transfer augmentation in laminar natural convection. Our non-homogenous modeling approach shows that heat transfer in nanofluids is a function of the inclination angle and Ra number. It also reveals some details of flow behavior which cannot be captured by single-phase models. The minimum heat transfer rate is associated with β = 90° (bottom-heated) and the maximum heat transfer rate occurs in an inclination angle which varies with the Ra number.

  10. Numerical Simulation of Natural Convection of a Nanofluid in an Inclined Heated Enclosure Using Two-Phase Lattice Boltzmann Method: Accurate Effects of Thermophoresis and Brownian Forces

    NASA Astrophysics Data System (ADS)

    Ahmed, Mahmoud; Eslamian, Morteza

    2015-07-01

    Laminar natural convection in differentially heated ( β = 0°, where β is the inclination angle), inclined ( β = 30° and 60°), and bottom-heated ( β = 90°) square enclosures filled with a nanofluid is investigated, using a two-phase lattice Boltzmann simulation approach. The effects of the inclination angle on Nu number and convection heat transfer coefficient are studied. The effects of thermophoresis and Brownian forces which create a relative drift or slip velocity between the particles and the base fluid are included in the simulation. The effect of thermophoresis is considered using an accurate and quantitative formula proposed by the authors. Some of the existing results on natural convection are erroneous due to using wrong thermophoresis models or simply ignoring the effect. Here we show that thermophoresis has a considerable effect on heat transfer augmentation in laminar natural convection. Our non-homogenous modeling approach shows that heat transfer in nanofluids is a function of the inclination angle and Ra number. It also reveals some details of flow behavior which cannot be captured by single-phase models. The minimum heat transfer rate is associated with β = 90° (bottom-heated) and the maximum heat transfer rate occurs in an inclination angle which varies with the Ra number.

  11. Windblown sand on Venus - Preliminary results of laboratory simulations

    NASA Technical Reports Server (NTRS)

    Greeley, R.; Iversen, J.; Leach, R.; Marshall, J.; Williams, S.; White, B.

    1984-01-01

    Small particles and winds of sufficient strength to move them have been detected from Venera and Pioneer-Venus data and suggest the existence of aeolian processes on Venus. The Venus wind tunnel (VWT) was fabricated in order to investigate the behavior of windblown particles in a simulated Venusian environment. Preliminary results show that sand-size material is readily entrained at the wind speeds detected on Venus and that saltating grains achieve velocities closely matching those of the wind. Measurements of saltation threshold and particle flux for various particle sizes have been compared with theoretical models which were developed by extrapolation of findings from Martian and terrestrial simulations. Results are in general agreement with theory, although certain discrepancies are apparent which may be attributed to experimental and/or theoretical-modeling procedures. Present findings enable a better understanding of Venusian surface processes and suggest that aeolian processes are important in the geological evolution of Venus.

  12. Key results from SB8 simulant flowsheet studies

    SciTech Connect

    Koopman, D. C.

    2013-04-26

    Key technically reviewed results are presented here in support of the Defense Waste Processing Facility (DWPF) acceptance of Sludge Batch 8 (SB8). This report summarizes results from simulant flowsheet studies of the DWPF Chemical Process Cell (CPC). Results include: Hydrogen generation rate for the Sludge Receipt and Adjustment Tank (SRAT) and Slurry Mix Evaporator (SME) cycles of the CPC on a 6,000 gallon basis; Volume percent of nitrous oxide, N2O, produced during the SRAT cycle; Ammonium ion concentrations recovered from the SRAT and SME off-gas; and, Dried weight percent solids (insoluble, soluble, and total) measurements and density.

  13. Comprehensive simulation of the middle atmospheric climate: some recent results

    NASA Astrophysics Data System (ADS)

    Hamilton, Kevin

    1995-05-01

    This study discusses the results of comprehensive time-dependent, three-dimensional numerical modelling of the circulation in the middle atmosphere obtained with the GFDL “SKYHI” troposphere-stratosphere-mesosphere general circulation model (GCM). The climate in a long control simulation with an intermediate resolution version (≈3° in horizontal) is briefly reviewed. While many aspects of the simulation are quite realistic, the focus in this study is on remaining first-order problems with the modelled middle atmospheric general circulation, notably the very cold high latitude temperatures in the Southern Hemisphere (SH) winter/spring, and the virtual absence of a quasi-biennial oscillation (QBO) in the tropical stratosphere. These problems are shared by other extant GCMs. It was noted that the SH cold pole problem is somewhat ameliorated with increasing horizontal resolution in the model. This suggests that improved resolution increases the vertical momentum fluxes from the explicitly resolved gravity waves in the model, a point confirmed by detailed analysis of the spectrum of vertical eddy momentum flux in the winter SH extratropics. This result inspired a series of experiments with the 3° SKYHI model modified by adding a prescribed zonally-symmetric zonal drag on the SH winter westerlies. The form of the imposed momentum source was based on the simple assumption that the mean flow drag produced by unresolved waves has a spatial distribution similar to that of the Eliassen-Palm flux divergence associated with explicitly resolved gravity waves. It was found that an appropriately-chosen drag confined to the top six model levels (above 0.35 mb) can lead to quite realistic simulations of the SH winter flow (including even the stationary wave fields) through August, but that problems still remain in the late-winter/springtime simulation. While the imposed momentum source was largely confined to the extratropics, it produced considerable improvement in the

  14. On the near space population from simulation results

    NASA Astrophysics Data System (ADS)

    Tischenko, V. I.

    A new computer technology module for studying meteoroid complexes is proposed. Space structure is represented by orbital fragments with their visualization from simulated cometary nucleus disintegration. The modelled section in the ecliptic is shown which presents the complex form and its inner structure. This representation can be used for analysing space filling to establish potentially dangerous regions near the complex and the concrete planet's orbits or other object routes. Main results for specific comets are given.

  15. Report: EPA Needs Accurate Data on Results of Pollution Prevention Grants to Maintain Program Integrity and Measure Effectiveness of Grants

    EPA Pesticide Factsheets

    Report #15-P-0276, September 4, 2015. Inaccurate reporting of results misrepresents the impacts of pollution prevention activities provided to the public, and misinforms EPA management on the effectiveness of its investment in the program.

  16. Airflow Hazard Visualization for Helicopter Pilots: Flight Simulation Study Results

    NASA Technical Reports Server (NTRS)

    Aragon, Cecilia R.; Long, Kurtis R.

    2005-01-01

    Airflow hazards such as vortices or low level wind shear have been identified as a primary contributing factor in many helicopter accidents. US Navy ships generate airwakes over their decks, creating potentially hazardous conditions for shipboard rotorcraft launch and recovery. Recent sensor developments may enable the delivery of airwake data to the cockpit, where visualizing the hazard data may improve safety and possibly extend ship/helicopter operational envelopes. A prototype flight-deck airflow hazard visualization system was implemented on a high-fidelity rotorcraft flight dynamics simulator. Experienced helicopter pilots, including pilots from all five branches of the military, participated in a usability study of the system. Data was collected both objectively from the simulator and subjectively from post-test questionnaires. Results of the data analysis are presented, demonstrating a reduction in crash rate and other trends that illustrate the potential of airflow hazard visualization to improve flight safety.

  17. TU-EF-204-01: Accurate Prediction of CT Tube Current Modulation: Estimating Tube Current Modulation Schemes for Voxelized Patient Models Used in Monte Carlo Simulations

    SciTech Connect

    McMillan, K; Bostani, M; McNitt-Gray, M; McCollough, C

    2015-06-15

    Purpose: Most patient models used in Monte Carlo-based estimates of CT dose, including computational phantoms, do not have tube current modulation (TCM) data associated with them. While not a problem for fixed tube current simulations, this is a limitation when modeling the effects of TCM. Therefore, the purpose of this work was to develop and validate methods to estimate TCM schemes for any voxelized patient model. Methods: For 10 patients who received clinically-indicated chest (n=5) and abdomen/pelvis (n=5) scans on a Siemens CT scanner, both CT localizer radiograph (“topogram”) and image data were collected. Methods were devised to estimate the complete x-y-z TCM scheme using patient attenuation data: (a) available in the Siemens CT localizer radiograph/topogram itself (“actual-topo”) and (b) from a simulated topogram (“sim-topo”) derived from a projection of the image data. For comparison, the actual TCM scheme was extracted from the projection data of each patient. For validation, Monte Carlo simulations were performed using each TCM scheme to estimate dose to the lungs (chest scans) and liver (abdomen/pelvis scans). Organ doses from simulations using the actual TCM were compared to those using each of the estimated TCM methods (“actual-topo” and “sim-topo”). Results: For chest scans, the average differences between doses estimated using actual TCM schemes and estimated TCM schemes (“actual-topo” and “sim-topo”) were 3.70% and 4.98%, respectively. For abdomen/pelvis scans, the average differences were 5.55% and 6.97%, respectively. Conclusion: Strong agreement between doses estimated using actual and estimated TCM schemes validates the methods for simulating Siemens topograms and converting attenuation data into TCM schemes. This indicates that the methods developed in this work can be used to accurately estimate TCM schemes for any patient model or computational phantom, whether a CT localizer radiograph is available or not

  18. Analysis of Numerical Simulation Results of LIPS-200 Lifetime Experiments

    NASA Astrophysics Data System (ADS)

    Chen, Juanjuan; Zhang, Tianping; Geng, Hai; Jia, Yanhui; Meng, Wei; Wu, Xianming; Sun, Anbang

    2016-06-01

    Accelerator grid structural and electron backstreaming failures are the most important factors affecting the ion thruster's lifetime. During the thruster's operation, Charge Exchange Xenon (CEX) ions are generated from collisions between plasma and neutral atoms. Those CEX ions grid's barrel and wall frequently, which cause the failures of the grid system. In order to validate whether the 20 cm Lanzhou Ion Propulsion System (LIPS-200) satisfies China's communication satellite platform's application requirement for North-South Station Keeping (NSSK), this study analyzed the measured depth of the pit/groove on the accelerator grid's wall and aperture diameter's variation and estimated the operating lifetime of the ion thruster. Different from the previous method, in this paper, the experimental results after the 5500 h of accumulated operation of the LIPS-200 ion thruster are presented firstly. Then, based on these results, theoretical analysis and numerical calculations were firstly performed to predict the on-orbit lifetime of LIPS-200. The results obtained were more accurate to calculate the reliability and analyze the failure modes of the ion thruster. The results indicated that the predicted lifetime of LIPS-200's was about 13218.1 h which could satisfy the required lifetime requirement of 11000 h very well.

  19. Infectious titres of sheep scrapie and bovine spongiform encephalopathy agents cannot be accurately predicted from quantitative laboratory test results.

    PubMed

    González, Lorenzo; Thorne, Leigh; Jeffrey, Martin; Martin, Stuart; Spiropoulos, John; Beck, Katy E; Lockey, Richard W; Vickery, Christopher M; Holder, Thomas; Terry, Linda

    2012-11-01

    It is widely accepted that abnormal forms of the prion protein (PrP) are the best surrogate marker for the infectious agent of prion diseases and, in practice, the detection of such disease-associated (PrP(d)) and/or protease-resistant (PrP(res)) forms of PrP is the cornerstone of diagnosis and surveillance of the transmissible spongiform encephalopathies (TSEs). Nevertheless, some studies question the consistent association between infectivity and abnormal PrP detection. To address this discrepancy, 11 brain samples of sheep affected with natural scrapie or experimental bovine spongiform encephalopathy were selected on the basis of the magnitude and predominant types of PrP(d) accumulation, as shown by immunohistochemical (IHC) examination; contra-lateral hemi-brain samples were inoculated at three different dilutions into transgenic mice overexpressing ovine PrP and were also subjected to quantitative analysis by three biochemical tests (BCTs). Six samples gave 'low' infectious titres (10⁶·⁵ to 10⁶·⁷ LD₅₀ g⁻¹) and five gave 'high titres' (10⁸·¹ to ≥ 10⁸·⁷ LD₅₀ g⁻¹) and, with the exception of the Western blot analysis, those two groups tended to correspond with samples with lower PrP(d)/PrP(res) results by IHC/BCTs. However, no statistical association could be confirmed due to high individual sample variability. It is concluded that although detection of abnormal forms of PrP by laboratory methods remains useful to confirm TSE infection, infectivity titres cannot be predicted from quantitative test results, at least for the TSE sources and host PRNP genotypes used in this study. Furthermore, the near inverse correlation between infectious titres and Western blot results (high protease pre-treatment) argues for a dissociation between infectivity and PrP(res).

  20. Towards more accurate isoscapes encouraging results from wine, water and marijuana data/model and model/model comparisons.

    NASA Astrophysics Data System (ADS)

    West, J. B.; Ehleringer, J. R.; Cerling, T.

    2006-12-01

    Understanding how the biosphere responds to change it at the heart of biogeochemistry, ecology, and other Earth sciences. The dramatic increase in human population and technological capacity over the past 200 years or so has resulted in numerous, simultaneous changes to biosphere structure and function. This, then, has lead to increased urgency in the scientific community to try to understand how systems have already responded to these changes, and how they might do so in the future. Since all biospheric processes exhibit some patchiness or patterns over space, as well as time, we believe that understanding the dynamic interactions between natural systems and human technological manipulations can be improved if these systems are studied in an explicitly spatial context. We present here results of some of our efforts to model the spatial variation in the stable isotope ratios (δ2H and δ18O) of plants over large spatial extents, and how these spatial model predictions compare to spatially explicit data. Stable isotopes trace and record ecological processes and as such, if modeled correctly over Earth's surface allow us insights into changes in biosphere states and processes across spatial scales. The data-model comparisons show good agreement, in spite of the remaining uncertainties (e.g., plant source water isotopic composition). For example, inter-annual changes in climate are recorded in wine stable isotope ratios. Also, a much simpler model of leaf water enrichment driven with spatially continuous global rasters of precipitation and climate normals largely agrees with complex GCM modeling that includes leaf water δ18O. Our results suggest that modeling plant stable isotope ratios across large spatial extents may be done with reasonable accuracy, including over time. These spatial maps, or isoscapes, can now be utilized to help understand spatially distributed data, as well as to help guide future studies designed to understand ecological change across

  1. Electron-cloud updated simulation results for the PSR, and recent results for the SNS

    SciTech Connect

    Pivi, M.; Furman, M.A.

    2002-05-29

    Recent simulation results for the main features of the electron cloud in the storage ring of the Spallation Neutron Source (SNS) at Oak Ridge, and updated results for the Proton Storage Ring (PSR) at Los Alamos are presented in this paper. A refined model for the secondary emission process including the so called true secondary, rediffused and backscattered electrons has recently been included in the electron-cloud code.

  2. Modeling results for a linear simulator of a divertor

    SciTech Connect

    Hooper, E.B.; Brown, M.D.; Byers, J.A.; Casper, T.A.; Cohen, B.I.; Cohen, R.H.; Jackson, M.C.; Kaiser, T.B.; Molvik, A.W.; Nevins, W.M.; Nilson, D.G.; Pearlstein, L.D.; Rognlien, T.D.

    1993-06-23

    A divertor simulator, IDEAL, has been proposed by S. Cohen to study the difficult power-handling requirements of the tokamak program in general and the ITER program in particular. Projections of the power density in the ITER divertor reach {approximately} 1 Gw/m{sup 2} along the magnetic fieldlines and > 10 MW/m{sup 2} on a surface inclined at a shallow angle to the fieldlines. These power densities are substantially greater than can be handled reliably on the surface, so new techniques are required to reduce the power density to a reasonable level. Although the divertor physics must be demonstrated in tokamaks, a linear device could contribute to the development because of its flexibility, the easy access to the plasma and to tested components, and long pulse operation (essentially cw). However, a decision to build a simulator requires not just the recognition of its programmatic value, but also confidence that it can meet the required parameters at an affordable cost. Accordingly, as reported here, it was decided to examine the physics of the proposed device, including kinetic effects resulting from the intense heating required to reach the plasma parameters, and to conduct an independent cost estimate. The detailed role of the simulator in a divertor program is not explored in this report.

  3. Time-accurate aeroelastic simulations of a wind turbine in yaw and shear using a coupled CFD-CSD method

    NASA Astrophysics Data System (ADS)

    Yu, D. O.; Kwon, O. J.

    2014-06-01

    In the present study, aeroelastic simulations of horizontal-axis wind turbine rotor blades were conducted using a coupled CFD-CSD method. The unsteady blade aerodynamic loads and the dynamic blade response due to yaw misalignment and non-uniform sheared wind were investigated. For this purpose, a CFD code solving the RANS equations on unstructured meshes and a FEM-based CSD beam solver were used. The coupling of the CFD and CSD solvers was made by exchanging the data between the two solvers in a loosely coupled manner. The present coupled CFD-CSD method was applied to the NREL 5MW reference wind turbine rotor, and the results were compared with those of CFD-alone rigid blade calculations. It was found that aeroelastic blade deformation leads to a significant reduction of blade aerodynamic loads, and alters the unsteady load behaviours, mainly due to the torsional deformation. The reduction of blade aerodynamic loads is particularly significant at the advancing rotor blade side for yawed flow conditions, and at the upper half of rotor disk where wind velocity is higher due to wind shear.

  4. The route to MBxNyCz molecular wheels: II. Results using accurate functionals and basis sets

    NASA Astrophysics Data System (ADS)

    Güthler, A.; Mukhopadhyay, S.; Pandey, R.; Boustani, I.

    2014-04-01

    Applying ab initio quantum chemical methods, molecular wheels composed of metal and light atoms were investigated. High quality basis sets 6-31G*, TZPV, and cc-pVTZ as well as exchange and non-local correlation functionals B3LYP, BP86 and B3P86 were used. The ground-state energy and structures of cyclic planar and pyramidal clusters TiBn (for n = 3-10) were computed. In addition, the relative stability and electronic structures of molecular wheels TiBxNyCz (for x, y, z = 0-10) and MBnC10-n (for n = 2 to 5 and M = Sc to Zn) were determined. This paper sustains a follow-up study to the previous one of Boustani and Pandey [Solid State Sci. 14 (2012) 1591], in which the calculations were carried out at the HF-SCF/STO3G/6-31G level of theory to determine the initial stability and properties. The results show that there is a competition between the 2D planar and the 3D pyramidal TiBn clusters (for n = 3-8). Different isomers of TiB10 clusters were also studied and a structural transition of 3D-isomer into 2D-wheel is presented. Substitution boron in TiB10 by carbon or/and nitrogen atoms enhances the stability and leads toward the most stable wheel TiB3C7. Furthermore, the computations show that Sc, Ti and V at the center of the molecular wheels are energetically favored over other transition metal atoms of the first row.

  5. Nucleic Acids Research Group (NRG): The Importance of DNA Extraction in Metagenomics: The Gatekeeper to Accurate Results!

    PubMed Central

    Carmical, R.; Nadella, V.; Herbert, Z.; Beckloff, N.; Chittur, S.; Rosato, C.; Perera, A.; Auer, H.; Robinson, M.; Tighe, S.; Holbrook, Jennifer

    2013-01-01

    It is well recognized that the field of metagenomics is becoming a critical tool for studying previously unobtainable population dynamics at both an identification of species level and a functional or transcriptional level. Because the power to resolve microbial information is so important for identifying the components in an mixed sample, metagenomics can be used to study nearly any possible environment or system including clinical, environmental, and industrial, to name a few. Clinically, it may be used to determine sub-populations colonizing regions of the body or determining a rare infection to assist in treatment strategies. Environmentally it may be used to identify microbial populations within a soil, water or air sample, or within a bioreactor to characterize a population- based functional process. The possibilities are endless. However, the accuracy of a metagenomics dataset relies on three important “gatekeepers” including 1) The ability to effectively extract all DNA or RNA from every cell within a sample, 2) The reliability of the methods used for deep or high-throughput sequencing, and 3) The software used to analyze the data. Since DNA extraction is the first step in the technical process of metagenomics, the Nucleic Acid Research Group (NARG) conducted a study to evaluate extraction methods using a synthetic microbial sample. The synthetic microbial sample was prepared from 10 known bacteria at specific concentrations and ranging in diversity. Samples were extracted in duplicate using various popular kit based methods as well as several homebrew protocols then analyzed by NextGen sequencing on an Illumina HiSeq. Results of the study include determining the percent recovery of those organisms by comparing to the known quantity in the original synthetic mix.

  6. An Electroacoustic Hearing Protector Simulator That Accurately Predicts Pressure Levels in the Ear Based on Standard Performance Metrics

    DTIC Science & Technology

    2013-08-01

    24 Figure 20. ABQ experiment showing five volunteers located 1.0 m from source in upper-left panel wearing...study (Royster et al.,1996) in which users self-fit hearing protectors (ANSI S12.6- 2008 method B: user fit) with no experimenter instruction gives an...values provided by the experimenters and simulator fits for the intact and modified muffs. Figure 22 (upper panel) shows the simulator prediction

  7. Earth resources mission performance studies. Volume 2: Simulation results

    NASA Technical Reports Server (NTRS)

    1974-01-01

    Simulations were made at three month intervals to investigate the EOS mission performance over the four seasons of the year. The basic objectives of the study were: (1) to evaluate the ability of an EOS type system to meet a representative set of specific collection requirements, and (2) to understand the capabilities and limitations of the EOS that influence the system's ability to satisfy certain collection objectives. Although the results were obtained from a consideration of a two sensor EOS system, the analysis can be applied to any remote sensing system having similar optical and operational characteristics. While the category related results are applicable only to the specified requirement configuration, the results relating to general capability and limitations of the sensors can be applied in extrapolating to other U.S. based EOS collection requirements. The TRW general purpose mission simulator and analytic techniques discussed in this report can be applied to a wide range of collection and planning problems of earth orbiting imaging systems.

  8. Planck 2015 results. XII. Full focal plane simulations

    NASA Astrophysics Data System (ADS)

    Planck Collaboration; Ade, P. A. R.; Aghanim, N.; Arnaud, M.; Ashdown, M.; Aumont, J.; Baccigalupi, C.; Banday, A. J.; Barreiro, R. B.; Bartlett, J. G.; Bartolo, N.; Battaner, E.; Benabed, K.; Benoît, A.; Benoit-Lévy, A.; Bernard, J.-P.; Bersanelli, M.; Bielewicz, P.; Bock, J. J.; Bonaldi, A.; Bonavera, L.; Bond, J. R.; Borrill, J.; Bouchet, F. R.; Boulanger, F.; Bucher, M.; Burigana, C.; Butler, R. C.; Calabrese, E.; Cardoso, J.-F.; Castex, G.; Catalano, A.; Challinor, A.; Chamballu, A.; Chiang, H. C.; Christensen, P. R.; Clements, D. L.; Colombi, S.; Colombo, L. P. L.; Combet, C.; Couchot, F.; Coulais, A.; Crill, B. P.; Curto, A.; Cuttaia, F.; Danese, L.; Davies, R. D.; Davis, R. J.; de Bernardis, P.; de Rosa, A.; de Zotti, G.; Delabrouille, J.; Delouis, J.-M.; Désert, F.-X.; Dickinson, C.; Diego, J. M.; Dolag, K.; Dole, H.; Donzelli, S.; Doré, O.; Douspis, M.; Ducout, A.; Dupac, X.; Efstathiou, G.; Elsner, F.; Enßlin, T. A.; Eriksen, H. K.; Fergusson, J.; Finelli, F.; Forni, O.; Frailis, M.; Fraisse, A. A.; Franceschi, E.; Frejsel, A.; Galeotta, S.; Galli, S.; Ganga, K.; Ghosh, T.; Giard, M.; Giraud-Héraud, Y.; Gjerløw, E.; González-Nuevo, J.; Górski, K. M.; Gratton, S.; Gregorio, A.; Gruppuso, A.; Gudmundsson, J. E.; Hansen, F. K.; Hanson, D.; Harrison, D. L.; Henrot-Versillé, S.; Hernández-Monteagudo, C.; Herranz, D.; Hildebrandt, S. R.; Hivon, E.; Hobson, M.; Holmes, W. A.; Hornstrup, A.; Hovest, W.; Huffenberger, K. M.; Hurier, G.; Jaffe, A. H.; Jaffe, T. R.; Jones, W. C.; Juvela, M.; Karakci, A.; Keihänen, E.; Keskitalo, R.; Kiiveri, K.; Kisner, T. S.; Kneissl, R.; Knoche, J.; Kunz, M.; Kurki-Suonio, H.; Lagache, G.; Lamarre, J.-M.; Lasenby, A.; Lattanzi, M.; Lawrence, C. R.; Leonardi, R.; Lesgourgues, J.; Levrier, F.; Liguori, M.; Lilje, P. B.; Linden-Vørnle, M.; Lindholm, V.; López-Caniego, M.; Lubin, P. M.; Macías-Pérez, J. F.; Maggio, G.; Maino, D.; Mandolesi, N.; Mangilli, A.; Maris, M.; Martin, P. G.; Martínez-González, E.; Masi, S.; Matarrese, S.; McGehee, P.; Meinhold, P. R.; Melchiorri, A.; Melin, J.-B.; Mendes, L.; Mennella, A.; Migliaccio, M.; Mitra, S.; Miville-Deschênes, M.-A.; Moneti, A.; Montier, L.; Morgante, G.; Mortlock, D.; Moss, A.; Munshi, D.; Murphy, J. A.; Naselsky, P.; Nati, F.; Natoli, P.; Netterfield, C. B.; Nørgaard-Nielsen, H. U.; Noviello, F.; Novikov, D.; Novikov, I.; Oxborrow, C. A.; Paci, F.; Pagano, L.; Pajot, F.; Paoletti, D.; Pasian, F.; Patanchon, G.; Pearson, T. J.; Perdereau, O.; Perotto, L.; Perrotta, F.; Pettorino, V.; Piacentini, F.; Piat, M.; Pierpaoli, E.; Pietrobon, D.; Plaszczynski, S.; Pointecouteau, E.; Polenta, G.; Pratt, G. W.; Prézeau, G.; Prunet, S.; Puget, J.-L.; Rachen, J. P.; Rebolo, R.; Reinecke, M.; Remazeilles, M.; Renault, C.; Renzi, A.; Ristorcelli, I.; Rocha, G.; Roman, M.; Rosset, C.; Rossetti, M.; Roudier, G.; Rubiño-Martín, J. A.; Rusholme, B.; Sandri, M.; Santos, D.; Savelainen, M.; Scott, D.; Seiffert, M. D.; Shellard, E. P. S.; Spencer, L. D.; Stolyarov, V.; Stompor, R.; Sudiwala, R.; Sutton, D.; Suur-Uski, A.-S.; Sygnet, J.-F.; Tauber, J. A.; Terenzi, L.; Toffolatti, L.; Tomasi, M.; Tristram, M.; Tucci, M.; Tuovinen, J.; Valenziano, L.; Valiviita, J.; Van Tent, B.; Vielva, P.; Villa, F.; Wade, L. A.; Wandelt, B. D.; Wehus, I. K.; Welikala, N.; Yvon, D.; Zacchei, A.; Zonca, A.

    2016-09-01

    We present the 8th full focal plane simulation set (FFP8), deployed in support of the Planck 2015 results. FFP8 consists of 10 fiducial mission realizations reduced to 18 144 maps, together with the most massive suite of Monte Carlo realizations of instrument noise and CMB ever generated, comprising 104 mission realizations reduced to about 106 maps. The resulting maps incorporate the dominant instrumental, scanning, and data analysis effects, and the remaining subdominant effects will be included in future updates. Generated at a cost of some 25 million CPU-hours spread across multiple high-performance-computing (HPC) platforms, FFP8 is used to validate and verify analysis algorithms and their implementations, and to remove biases from and quantify uncertainties in the results of analyses of the real data.

  9. Diamond-NICAM-SPRINTARS: downscaling and simulation results

    NASA Astrophysics Data System (ADS)

    Uchida, J.

    2012-12-01

    As a part of initiative "Research Program on Climate Change Adaptation" (RECCA) which investigates how predicted large-scale climate change may affect a local weather, and further examines possible atmospheric hazards that cities may encounter due to such a climate change, thus to guide policy makers on implementing new environmental measures, a "Development of Seamless Chemical AssimiLation System and its Application for Atmospheric Environmental Materials" (SALSA) project is funded by the Japanese Ministry of Education, Culture, Sports, Science and Technology and is focused on creating a regional (local) scale assimilation system that can accurately recreate and predict a transport of carbon dioxide and other air pollutants. In this study, a regional model of the next generation global cloud-resolving model NICAM (Non-hydrostatic ICosahedral Atmospheric Model) (Tomita and Satoh, 2004) is used and ran together with a transport model SPRINTARS (Spectral Radiation Transport Model for Aerosol Species) (Takemura et al, 2000) and a chemical transport model CHASER (Sudo et al, 2002) to simulate aerosols across urban cities (over a Kanto region including metropolitan Tokyo). The presentation will mainly be on a "Diamond-NICAM" (Figure 1), a regional climate model version of the global climate model NICAM, and its dynamical downscaling methodologies. Originally, a global NICAM can be described as twenty identical equilateral triangular-shaped panels covering the entire globe where grid points are at the corners of those panels, and to increase a resolution (called a "global-level" in NICAM), additional points are added at the middle of existing two adjacent points, so a number of panels increases by fourfold with an increment of one global-level. On the other hand, a Diamond-NICAM only uses two of those initial triangular-shaped panels, thus only covers part of the globe. In addition, NICAM uses an adaptive mesh scheme and its grid size can gradually decrease, as the grid

  10. Electron transport in the solar wind -results from numerical simulations

    NASA Astrophysics Data System (ADS)

    Smith, Håkan; Marsch, Eckart; Helander, Per

    A conventional fluid approach is in general insufficient for a correct description of electron trans-port in weakly collisional plasmas such as the solar wind. The classical Spitzer-Hürm theory is a not valid when the Knudsen number (the mean free path divided by the length scale of tem-perature variation) is greater than ˜ 10-2 . Despite this, the heat transport from Spitzer-Hürm a theory is widely used in situations with relatively long mean free paths. For realistic Knud-sen numbers in the solar wind, the electron distribution function develops suprathermal tails, and the departure from a local Maxwellian can be significant at the energies which contribute the most to the heat flux moment. To accurately model heat transport a kinetic approach is therefore more adequate. Different techniques have been used previously, e.g. particle sim-ulations [Landi, 2003], spectral methods [Pierrard, 2001], the so-called 16 moment method [Lie-Svendsen, 2001], and approximation by kappa functions [Dorelli, 2003]. In the present study we solve the Fokker-Planck equation for electrons in one spatial dimension and two velocity dimensions. The distribution function is expanded in Laguerre polynomials in energy, and a finite difference scheme is used to solve the equation in the spatial dimension and the velocity pitch angle. The ion temperature and density profiles are assumed to be known, but the electric field is calculated self-consistently to guarantee quasi-neutrality. The kinetic equation is of a two-way diffusion type, for which the distribution of particles entering the computational domain in both ends of the spatial dimension must be specified, leaving the outgoing distributions to be calculated. The long mean free path of the suprathermal electrons has the effect that the details of the boundary conditions play an important role in determining the particle and heat fluxes as well as the electric potential drop across the domain. Dorelli, J. C., and J. D. Scudder, J. D

  11. Simulation Results for Airborne Precision Spacing along Continuous Descent Arrivals

    NASA Technical Reports Server (NTRS)

    Barmore, Bryan E.; Abbott, Terence S.; Capron, William R.; Baxley, Brian T.

    2008-01-01

    This paper describes the results of a fast-time simulation experiment and a high-fidelity simulator validation with merging streams of aircraft flying Continuous Descent Arrivals through generic airspace to a runway at Dallas-Ft Worth. Aircraft made small speed adjustments based on an airborne-based spacing algorithm, so as to arrive at the threshold exactly at the assigned time interval behind their Traffic-To-Follow. The 40 aircraft were initialized at different altitudes and speeds on one of four different routes, and then merged at different points and altitudes while flying Continuous Descent Arrivals. This merging and spacing using flight deck equipment and procedures to augment or implement Air Traffic Management directives is called Flight Deck-based Merging and Spacing, an important subset of a larger Airborne Precision Spacing functionality. This research indicates that Flight Deck-based Merging and Spacing initiated while at cruise altitude and well prior to the Terminal Radar Approach Control entry can significantly contribute to the delivery of aircraft at a specified interval to the runway threshold with a high degree of accuracy and at a reduced pilot workload. Furthermore, previously documented work has shown that using a Continuous Descent Arrival instead of a traditional step-down descent can save fuel, reduce noise, and reduce emissions. Research into Flight Deck-based Merging and Spacing is a cooperative effort between government and industry partners.

  12. Some results on ethnic conflicts based on evolutionary game simulation

    NASA Astrophysics Data System (ADS)

    Qin, Jun; Yi, Yunfei; Wu, Hongrun; Liu, Yuhang; Tong, Xiaonian; Zheng, Bojin

    2014-07-01

    The force of the ethnic separatism, essentially originating from the negative effect of ethnic identity, is damaging the stability and harmony of multiethnic countries. In order to eliminate the foundation of the ethnic separatism and set up a harmonious ethnic relationship, some scholars have proposed a viewpoint: ethnic harmony could be promoted by popularizing civic identity. However, this viewpoint is discussed only from a philosophical prospective and still lacks support of scientific evidences. Because ethnic group and ethnic identity are products of evolution and ethnic identity is the parochialism strategy under the perspective of game theory, this paper proposes an evolutionary game simulation model to study the relationship between civic identity and ethnic conflict based on evolutionary game theory. The simulation results indicate that: (1) the ratio of individuals with civic identity has a negative association with the frequency of ethnic conflicts; (2) ethnic conflict will not die out by killing all ethnic members once for all, and it also cannot be reduced by a forcible pressure, i.e., increasing the ratio of individuals with civic identity; (3) the average frequencies of conflicts can stay in a low level by promoting civic identity periodically and persistently.

  13. Dynamic damping control: Implementation issues and simulation results

    SciTech Connect

    Anderson, R.J.

    1989-01-01

    Computed torque algorithms are used to compensate for the changing dynamics of robot manipulators in order to ensure that a constant level of damping is maintained for all configurations. Unfortunately, there are three significant problems with existing computed torque algorithms. First, they are nonpassive and can lead to unstable behavior; second, they make inefficient use of actuator capability; and third, they cannot be used to maintain a constant end-effector stiffness for force control tasks. Recently, we introduced a new control algorithm for robots which, like computed torque, uses a model of the manipulator's dynamics to maintain a constant level of damping in the system, but does so passively. This new class of passive control algorithms has guaranteed stability properties, utilizes actuators more effectively, and can also be used to maintain constant end-effector stiffness. In this paper, this approach is described in detail, implementation issues are discussed, and simulation results are given. 15 refs., 6 figs., 2 tabs.

  14. Aeolian abrasion on Venus: Preliminary results from the Venus simulator

    NASA Technical Reports Server (NTRS)

    Marshall, J. R.; Greeley, Ronald; Tucker, D. W.; Pollack, J. B.

    1987-01-01

    The role of atmospheric pressure on aeolian abrasion was examined in the Venus Simulator with a constant temperature of 737 K. Both the rock target and the impactor were fine-grained basalt. The impactor was a 3 mm diameter angular particle chosen to represent a size of material that is entrainable by the dense Venusian atmosphere and potentially abrasive by virtue of its mass. It was projected at the target 10 to the 5 power times at a velocity of 0.7 m/s. The impactor showed a weight loss of approximately 1.2 x 10 to the -9 power gm per impact with the attrition occurring only at the edges. Results from scanning electron microscope analysis, profilometry, and weight measurement are summarized. It is concluded that particles can incur abrasion at Venusian temperatures even with low impact velocities expected for Venus.

  15. SLAC E144 Plots, Simulation Results, and Data

    DOE Data Explorer

    The 1997 E144 experiments at the Stanford Linear Accelerator Center (SLAC) utilitized extremely high laser intensities and collided huge groups of photons together so violently that positron-electron pairs were briefly created, actual particles of matter and antimatter. Instead of matter exploding into heat and light, light actually become matter. That accomplishment opened a new path into the exploration of the interactions of electrons and photons or quantum electrodynamics (QED). The E144 information at this website includes Feynmann Diagrams, simulation results, and data files. See also aseries of frames showing the E144 laser colliding with a beam electron and producing an electron-positron pair at http://www.slac.stanford.edu/exp/e144/focpic/focpic.html and lists of collaborators' papers, theses, and a page of press articles.

  16. Governance of complex systems: results of a sociological simulation experiment.

    PubMed

    Adelt, Fabian; Weyer, Johannes; Fink, Robin D

    2014-01-01

    Social sciences have discussed the governance of complex systems for a long time. The following paper tackles the issue by means of experimental sociology, in order to investigate the performance of different modes of governance empirically. The simulation framework developed is based on Esser's model of sociological explanation as well as on Kroneberg's model of frame selection. The performance of governance has been measured by means of three macro and two micro indicators. Surprisingly, central control mostly performs better than decentralised coordination. However, results not only depend on the mode of governance, but there is also a relation between performance and the composition of actor populations, which has yet not been investigated sufficiently. Practitioner Summary: Practitioners can gain insights into the functioning of complex systems and learn how to better manage them. Additionally, they are provided with indicators to measure the performance of complex systems.

  17. Accurate and efficient prediction of fine-resolution hydrologic and carbon dynamic simulations from coarse-resolution models

    NASA Astrophysics Data System (ADS)

    Pau, George Shu Heng; Shen, Chaopeng; Riley, William J.; Liu, Yaning

    2016-02-01

    The topography, and the biotic and abiotic parameters are typically upscaled to make watershed-scale hydrologic-biogeochemical models computationally tractable. However, upscaling procedure can produce biases when nonlinear interactions between different processes are not fully captured at coarse resolutions. Here we applied the Proper Orthogonal Decomposition Mapping Method (PODMM) to downscale the field solutions from a coarse (7 km) resolution grid to a fine (220 m) resolution grid. PODMM trains a reduced-order model (ROM) with coarse-resolution and fine-resolution solutions, here obtained using PAWS+CLM, a quasi-3-D watershed processes model that has been validated for many temperate watersheds. Subsequent fine-resolution solutions were approximated based only on coarse-resolution solutions and the ROM. The approximation errors were efficiently quantified using an error estimator. By jointly estimating correlated variables and temporally varying the ROM parameters, we further reduced the approximation errors by up to 20%. We also improved the method's robustness by constructing multiple ROMs using different set of variables, and selecting the best approximation based on the error estimator. The ROMs produced accurate downscaling of soil moisture, latent heat flux, and net primary production with O(1000) reduction in computational cost. The subgrid distributions were also nearly indistinguishable from the ones obtained using the fine-resolution model. Compared to coarse-resolution solutions, biases in upscaled ROM solutions were reduced by up to 80%. This method has the potential to help address the long-standing spatial scaling problem in hydrology and enable long-time integration, parameter estimation, and stochastic uncertainty analysis while accurately representing the heterogeneities.

  18. MULTEM: A new multislice program to perform accurate and fast electron diffraction and imaging simulations using Graphics Processing Units with CUDA.

    PubMed

    Lobato, I; Van Dyck, D

    2015-09-01

    The main features and the GPU implementation of the MULTEM program are presented and described. This new program performs accurate and fast multislice simulations by including higher order expansion of the multislice solution of the high energy Schrödinger equation, the correct subslicing of the three-dimensional potential and top-bottom surfaces. The program implements different kinds of simulation for CTEM, STEM, ED, PED, CBED, ADF-TEM and ABF-HC with proper treatment of the spatial and temporal incoherences. The multislice approach described here treats the specimen as amorphous material which allows a straightforward implementation of the frozen phonon approximation. The generalized transmission function for each slice is calculated when is needed and then discarded. This allows us to perform large simulations that can include millions of atoms and keep the computer memory requirements to a reasonable level.

  19. The Aurora radiation-hydrodynamical simulations of reionization: calibration and first results

    NASA Astrophysics Data System (ADS)

    Pawlik, Andreas H.; Rahmati, Alireza; Schaye, Joop; Jeon, Myoungwon; Dalla Vecchia, Claudio

    2017-04-01

    We introduce a new suite of radiation-hydrodynamical simulations of galaxy formation and reionization called Aurora. The Aurora simulations make use of a spatially adaptive radiative transfer technique that lets us accurately capture the small-scale structure in the gas at the resolution of the hydrodynamics, in cosmological volumes. In addition to ionizing radiation, Aurora includes galactic winds driven by star formation and the enrichment of the universe with metals synthesized in the stars. Our reference simulation uses 2 × 5123 dark matter and gas particles in a box of size 25 h-1 comoving Mpc with a force softening scale of at most 0.28 h-1 kpc. It is accompanied by simulations in larger and smaller boxes and at higher and lower resolution, employing up to 2 × 10243 particles, to investigate numerical convergence. All simulations are calibrated to yield simulated star formation rate functions in close agreement with observational constraints at redshift z = 7 and to achieve reionization at z ≈ 8.3, which is consistent with the observed optical depth to reionization. We focus on the design and calibration of the simulations and present some first results. The median stellar metallicities of low-mass galaxies at z = 6 are consistent with the metallicities of dwarf galaxies in the Local Group, which are believed to have formed most of their stars at high redshifts. After reionization, the mean photoionization rate decreases systematically with increasing resolution. This coincides with a systematic increase in the abundance of neutral hydrogen absorbers in the intergalactic medium.

  20. Can a quantitative simulation of an Otto engine be accurately rendered by a simple Novikov model with heat leak?

    NASA Astrophysics Data System (ADS)

    Fischer, A.; Hoffmann, K.-H.

    2004-03-01

    In this case study a complex Otto engine simulation provides data including, but not limited to, effects from losses due to heat conduction, exhaust losses and frictional losses. This data is used as a benchmark to test whether the Novikov engine with heat leak, a simple endoreversible model, can reproduce the complex engine behavior quantitatively by an appropriate choice of model parameters. The reproduction obtained proves to be of high quality.

  1. How Many Grid Points are Required for Time Accurate Simulations Scheme Selection and Scale-Discriminant Stabilization

    DTIC Science & Technology

    2015-11-24

    Simulations? Scheme Selection and Scale- Discriminant Stabilization 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S...N/A Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std. 239.18 1 Scheme Selection and Scale- Discriminant Stabilization How Many Grid...Statement A: Approved for public release; distribution is unlimited. Damping Characteristics: 
 Growth Factor 10 - need scale- discriminant , tunable

  2. A novel stress-accurate FE technology for highly non-linear analysis with incompressibility constraint. Application to the numerical simulation of the FSW process

    NASA Astrophysics Data System (ADS)

    Chiumenti, M.; Cervera, M.; Agelet de Saracibar, C.; Dialami, N.

    2013-05-01

    In this work a novel finite element technology based on a three-field mixed formulation is presented. The Variational Multi Scale (VMS) method is used to circumvent the LBB stability condition allowing the use of linear piece-wise interpolations for displacement, stress and pressure fields, respectively. The result is an enhanced stress field approximation which enables for stress-accurate results in nonlinear computational mechanics. The use of an independent nodal variable for the pressure field allows for an adhoc treatment of the incompressibility constraint. This is a mandatory requirement due to the isochoric nature of the plastic strain in metal forming processes. The highly non-linear stress field typically encountered in the Friction Stir Welding (FSW) process is used as an example to show the performance of this new FE technology. The numerical simulation of the FSW process is tackled by means of an Arbitrary-Lagrangian-Eulerian (ALE) formulation. The computational domain is split into three different zones: the work.piece (defined by a rigid visco-plastic behaviour in the Eulerian framework), the pin (within the Lagrangian framework) and finally the stirzone (ALE formulation). A fully coupled thermo-mechanical analysis is introduced showing the heat fluxes generated by the plastic dissipation in the stir-zone (Sheppard rigid-viscoplastic constitutive model) as well as the frictional dissipation at the contact interface (Norton frictional contact model). Finally, tracers have been implemented to show the material flow around the pin allowing a better understanding of the welding mechanism. Numerical results are compared with experimental evidence.

  3. Ion velocity distribution functions in argon and helium discharges: detailed comparison of numerical simulation results and experimental data

    NASA Astrophysics Data System (ADS)

    Wang, Huihui; Sukhomlinov, Vladimir S.; Kaganovich, Igor D.; Mustafaev, Alexander S.

    2017-02-01

    Using the Monte Carlo collision method, we have performed simulations of ion velocity distribution functions (IVDF) taking into account both elastic collisions and charge exchange collisions of ions with atoms in uniform electric fields for argon and helium background gases. The simulation results are verified by comparison with the experiment data of the ion mobilities and the ion transverse diffusion coefficients in argon and helium. The recently published experimental data for the first seven coefficients of the Legendre polynomial expansion of the ion energy and angular distribution functions are used to validate simulation results for IVDF. Good agreement between measured and simulated IVDFs shows that the developed simulation model can be used for accurate calculations of IVDFs.

  4. New simulation and measurement results on gateable DEPFET devices

    NASA Astrophysics Data System (ADS)

    Bähr, Alexander; Aschauer, Stefan; Hermenau, Katrin; Herrmann, Sven; Lechner, Peter H.; Lutz, Gerhard; Majewski, Petra; Miessner, Danilo; Porro, Matteo; Richter, Rainer H.; Schaller, Gerhard; Sandow, Christian; Schnecke, Martina; Schopper, Florian; Stefanescu, Alexander; Strüder, Lothar; Treis, Johannes

    2012-07-01

    To improve the signal to noise level, devices for optical and x-ray astronomy use techniques to suppress background events. Well known examples are e.g. shutters or frame-store Charge Coupled Devices (CCDs). Based on the DEpleted P-channel Field Effect Transistor (DEPFET) principle a so-called Gatebale DEPFET detector can be built. Those devices combine the DEPFET principle with a fast built-in electronic shutter usable for optical and x-ray applications. The DEPFET itself is the basic cell of an active pixel sensor build on a fully depleted bulk. It combines internal amplification, readout on demand, analog storage of the signal charge and a low readout noise with full sensitivity over the whole bulk thickness. A Gatebale DEPFET has all these benefits and obviates the need for an external shutter. Two concepts of Gatebale DEPFET layouts providing a built-in shutter will be introduced. Furthermore proof of principle measurements for both concepts are presented. Using recently produced prototypes a shielding of the collection anode up to 1 • 10-4 was achieved. Predicted by simulations, an optimized geometry should result in values of 1 • 10-5 and better. With the switching electronic currently in use a timing evaluation of the shutter opening and closing resulted in rise and fall times of 100ns.

  5. Accurate Three States Model for Amino Acids with Two Chemically Coupled Titrating Sites in Explicit Solvent Atomistic Constant pH Simulations and pKa Calculations.

    PubMed

    Dobrev, Plamen; Donnini, Serena; Groenhof, Gerrit; Grubmüller, Helmut

    2017-01-10

    Correct protonation of titratable groups in biomolecules is crucial for their accurate description by molecular dynamics simulations. In the context of constant pH simulations, an additional protonation degree of freedom is introduced for each titratable site, allowing the protonation state to change dynamically with changing structure or electrostatics. Here, we extend previous approaches for an accurate description of chemically coupled titrating sites. A second reaction coordinate is used to switch between two tautomeric states of an amino acid with chemically coupled titratable sites, such as aspartate (Asp), glutamate (Glu), and histidine (His). To this aim, we test a scheme involving three protonation states. To facilitate charge neutrality as required for periodic boundary conditions and Particle Mesh Ewald (PME) electrostatics, titration of each respective amino acid is coupled to a "water" molecule that is charged in the opposite direction. Additionally, a force field modification for Amber99sb is introduced and tested for the description of carboxyl group protonation. Our three states model is tested by titration simulations of Asp, Glu, and His, yielding a good agreement, reproducing the correct geometry of the groups in their different protonation forms. We further show that the ion concentration change due to the neutralizing "water" molecules does not significantly affect the protonation free energies of the titratable groups, suggesting that the three states model provides a good description of biomolecular dynamics at constant pH.

  6. Stellar hydrodynamical modeling of dwarf galaxies: simulation methodology, tests, and first results

    NASA Astrophysics Data System (ADS)

    Vorobyov, Eduard I.; Recchi, Simone; Hensler, Gerhard

    2015-07-01

    Context. In spite of enormous progress and brilliant achievements in cosmological simulations, they still lack numerical resolution or physical processes to simulate dwarf galaxies in sufficient detail. Accurate numerical simulations of individual dwarf galaxies are thus still in demand. Aims: We aim to improve available numerical techniques to simulate individual dwarf galaxies. In particular, we aim to (i) study in detail the coupling between stars and gas in a galaxy, exploiting the so-called stellar hydrodynamical approach; and (ii) study for the first time the chemodynamical evolution of individual galaxies starting from self-consistently calculated initial gas distributions. Methods: We present a novel chemodynamical code for studying the evolution of individual dwarf galaxies. In this code, the dynamics of gas is computed using the usual hydrodynamics equations, while the dynamics of stars is described by the stellar hydrodynamics approach, which solves for the first three moments of the collisionless Boltzmann equation. The feedback from stellar winds and dying stars is followed in detail. In particular, a novel and detailed approach has been developed to trace the aging of various stellar populations, which facilitates an accurate calculation of the stellar feedback depending on the stellar age. The code has been accurately benchmarked, allowing us to provide a recipe for improving the code performance on the Sedov test problem. Results: We build initial equilibrium models of dwarf galaxies that take gas self-gravity into account and present different levels of rotational support. Models with high rotational support (and hence high degrees of flattening) develop prominent bipolar outflows; a newly-born stellar population in these models is preferentially concentrated to the galactic midplane. Models with little rotational support blow away a large fraction of the gas and the resulting stellar distribution is extended and diffuse. Models that start from non

  7. Determination of bedform resolution necessary to accurately resolve the flow field by comparing numerical simulations with field data

    NASA Astrophysics Data System (ADS)

    Margelowsky, G.; Foster, D.; Traykovski, P.; Felzenberg, J. A.

    2010-12-01

    The dynamics of wave-current and tidal flow bottom boundary layers are evaluated with a quasi-three-dimensional non-hydrostatic phase-resolving wave-current bottom boundary layer model, Dune. In each case, the model is evaluated with field observations of velocity profiles and seabed geometry. For wave-current boundary layers, the observations were obtained over a 26-day period in 13 m of water at the Martha’s Vineyard Coastal Observatory (MVCO, Edgartown, MA) in 2002 - 2003. Bedforms were orbital-scale ripples with wavelengths of 50-125 cm and heights of 5-20 cm with peak root-mean-square orbital velocities and mean flows typically ranging from 50-70 cm/s and 10-20 cm/s, respectively. The observations for tidal flows were obtained over a 3-day period in 13-16 m of water in Portsmouth Harbor (Portsmouth, NH) in 2008. Bedforms were dunes with wavelengths on the order of 1 m and heights on the order of 10 cm with typical peak tidal currents of approximately 1 m/s. The flow field is simulated with a finite volume approach to solve the Reynolds-Averaged Navier-Stokes equations with a k-ω 2nd order turbulence closure scheme. The model simulations are performed for a range of theoretical and observed bedforms to examine the boundary layer sensitivity to the resolution of the bottom roughness. The observed and predicted vertical velocity profiles are evaluated with correlations and Briar’s Skill scores over the range of data sets.

  8. Impact of the accurateness of bidirectional reflectance distribution function data on the intensity and luminance distributions of a light-emitting diode mixing chamber as obtained by simulations

    NASA Astrophysics Data System (ADS)

    Audenaert, Jan; Leloup, Frédéric B.; Van Giel, Bart; Durinck, Guy; Deconinck, Geert; Hanselaer, Peter

    2013-09-01

    The reliability of ray tracing simulations is strongly dependent on the accuracy of the input data such as the bidirectional reflectance distribution function (BRDF). Software developers offer the possibility to implement BRDF data in different ways, ranging from simple predefined functions to detailed tabulated data. The impact of the accuracy of the implemented reflectance model on ray tracing simulations has been investigated. A light-emitting diode device including a frequently employed diffuse reflector [microcellular polyethylene terephthalate (MCPET)] was constructed. The luminous intensity distribution (LID) and luminance distribution from a specific viewpoint were measured with a near-field goniophotometer. Both distributions were also simulated by use of ray tracing software. Three different reflection models of MCPET were introduced, varying in complexity: a diffuse model, a diffuse/specular model, and a model containing tabulated BRDF data. A good agreement between the measured and simulated LID was found irrespective of the applied model. However, the luminance distributions only corresponded when the most accurate BRDF model was applied. This proves that even for diffuse reflective materials, a simple BRDF model may only be employed for simulations of the LID; for evaluation of luminance distributions, more complex models are needed.

  9. Langmuir Wave Decay in Inhomogeneous Solar Wind Plasmas: Simulation Results

    NASA Astrophysics Data System (ADS)

    Krafft, C.; Volokitin, A. S.; Krasnoselskikh, V. V.

    2015-08-01

    Langmuir turbulence excited by electron flows in solar wind plasmas is studied on the basis of numerical simulations. In particular, nonlinear wave decay processes involving ion-sound (IS) waves are considered in order to understand their dependence on external long-wavelength plasma density fluctuations. In the presence of inhomogeneities, it is shown that the decay processes are localized in space and, due to the differences between the group velocities of Langmuir and IS waves, their duration is limited so that a full nonlinear saturation cannot be achieved. The reflection and the scattering of Langmuir wave packets on the ambient and randomly varying density fluctuations lead to crucial effects impacting the development of the IS wave spectrum. Notably, beatings between forward propagating Langmuir waves and reflected ones result in the parametric generation of waves of noticeable amplitudes and in the amplification of IS waves. These processes, repeated at different space locations, form a series of cascades of wave energy transfer, similar to those studied in the frame of weak turbulence theory. The dynamics of such a cascading mechanism and its influence on the acceleration of the most energetic part of the electron beam are studied. Finally, the role of the decay processes in the shaping of the profiles of the Langmuir wave packets is discussed, and the waveforms calculated are compared with those observed recently on board the spacecraft Solar TErrestrial RElations Observatory and WIND.

  10. AGGREGATES: Finding structures in simulation results of solutions.

    PubMed

    Bernardes, Carlos E S

    2017-04-15

    Molecular Dynamic and Monte-Carlo simulations are widely used to investigate the structure and physical properties of solids and liquids at a molecular level. Tools to extract the most relevant information from the obtained results are, however, in considerable demand. One such tool, the program AGGREGATES, is described in this work. Based on distance criteria, the program searches trajectory files for the presence of molecular clusters and computes several statistical and shape properties for these structures. Tools designed to investigate the local organization and the molecular conformations in the clusters are also available. Among these, it is introduced a new approach to perform a First Shell Analysis, by looking for the presence of atomic contacts between molecules. These elements are particularly useful to obtain information on molecular assembly processes (such as the nucleation of crystals or colloidal particles) or to investigate polymorphism in organic compounds. The program features are illustrated here through the investigation of the 4'-hydroxyacetophenone + ethanol system. © 2017 Wiley Periodicals, Inc.

  11. LANGMUIR WAVE DECAY IN INHOMOGENEOUS SOLAR WIND PLASMAS: SIMULATION RESULTS

    SciTech Connect

    Krafft, C.; Volokitin, A. S.; Krasnoselskikh, V. V.

    2015-08-20

    Langmuir turbulence excited by electron flows in solar wind plasmas is studied on the basis of numerical simulations. In particular, nonlinear wave decay processes involving ion-sound (IS) waves are considered in order to understand their dependence on external long-wavelength plasma density fluctuations. In the presence of inhomogeneities, it is shown that the decay processes are localized in space and, due to the differences between the group velocities of Langmuir and IS waves, their duration is limited so that a full nonlinear saturation cannot be achieved. The reflection and the scattering of Langmuir wave packets on the ambient and randomly varying density fluctuations lead to crucial effects impacting the development of the IS wave spectrum. Notably, beatings between forward propagating Langmuir waves and reflected ones result in the parametric generation of waves of noticeable amplitudes and in the amplification of IS waves. These processes, repeated at different space locations, form a series of cascades of wave energy transfer, similar to those studied in the frame of weak turbulence theory. The dynamics of such a cascading mechanism and its influence on the acceleration of the most energetic part of the electron beam are studied. Finally, the role of the decay processes in the shaping of the profiles of the Langmuir wave packets is discussed, and the waveforms calculated are compared with those observed recently on board the spacecraft Solar TErrestrial RElations Observatory and WIND.

  12. Results of a Flight Simulation Software Methods Survey

    NASA Technical Reports Server (NTRS)

    Jackson, E. Bruce

    1995-01-01

    A ten-page questionnaire was mailed to members of the AIAA Flight Simulation Technical Committee in the spring of 1994. The survey inquired about various aspects of developing and maintaining flight simulation software, as well as a few questions dealing with characterization of each facility. As of this report, 19 completed surveys (out of 74 sent out) have been received. This paper summarizes those responses.

  13. Simulation of Accurate Vibrationally Resolved Electronic Spectra: the Integrated Time-Dependent and Time-Independent Framework

    NASA Astrophysics Data System (ADS)

    Baiardi, Alberto; Barone, Vincenzo; Biczysko, Malgorzata; Bloino, Julien

    2014-06-01

    Two parallel theories including Franck-Condon, Herzberg-Teller and Duschinsky (i.e., mode mixing) effects, allowing different approximations for the description of excited state PES have been developed in order to simulate realistic, asymmetric, electronic spectra line-shapes taking into account the vibrational structure: the so-called sum-over-states or time-independent (TI) method and the alternative time-dependent (TD) approach, which exploits the properties of the Fourier transform. The integrated TI-TD procedure included within a general purpose QM code [1,2], allows to compute one photon absorption, fluorescence, phosphorescence, electronic circular dichroism, circularly polarized luminescence and resonance Raman spectra. Combining both approaches, which use a single set of starting data, permits to profit from their respective advantages and minimize their respective limits: the time-dependent route automatically includes all vibrational states and, possibly, temperature effects, while the time-independent route allows to identify and assign single vibronic transitions. Interpretation, analysis and assignment of experimental spectra based on integrated TI-TD vibronic computations will be illustrated for challenging cases of medium-sized open-shell systems in the gas and condensed phases with inclusion of leading anharmonic effects. 1. V. Barone, A. Baiardi, M. Biczysko, J. Bloino, C. Cappelli, F. Lipparini Phys. Chem. Chem. Phys, 14, 12404, (2012) 2. A. Baiardi, V. Barone, J. Bloino J. Chem. Theory Comput., 9, 4097-4115 (2013)

  14. Flow Curve Determination at Large Plastic Strain Levels to Accurately Constitutive Equations of AHSS in Forming Simulation

    NASA Astrophysics Data System (ADS)

    Lemoine, X.; Sriram, S.; Kergen, R.

    2011-05-01

    ArcelorMittal continuously develops new steel grades (AHSS) with high performance for the automotive industry to improve the weight reduction and the passive safety. The wide market introduction of AHSS raises a new challenge for manufacturers in terms of material models in the prediction of forming—especially formability and springback. The relatively low uniform elongation, the high UTS and the low forming limit curve of these AHSS may cause difficulties in forming simulations. One of these difficulties is the consequence of the relatively low uniform elongation on the parameters identification of isotropic hardening model. Different experimental tests allow to reach large plastic strain levels (hydraulic bulge test, stack compression test, shear test…). After a description on how to determine the flow curve in these experimental tests, a comparison of the different flow curves is made for different steel grades. The ArcelorMittal identification protocol for hardening models is only based on stress-strain curves determined in uniaxial tension. Experimental tests where large plastic strain levels are reached are used to validate our identification protocol and to recommend some hardening models. Finally, the influence of isotropic hardening models and yield loci in forming prediction for AHSS steels will be presented.

  15. 3-D Time-Accurate CFD Simulations of a Multi-Megawatt Slender Bladed HAWT under Yawed Inflow Conditions

    NASA Astrophysics Data System (ADS)

    Sayed, M.; Lutz, Th.; Krämer, E.

    2016-09-01

    In the present study numerical investigations of a generic Multi-Megawatt slender bladed Horizontal-Axis Wind Turbine (HAWT) under yawed inflow conditions were conducted. A three-dimensional URANS flow solver based on structured overlapping meshes was used. The simulations were conducted at wind speeds of 7m/sec, 11 m/sec and 15 m/sec for different yaw angles ranging from +60° to -60°. It was concluded that, for below rated wind speeds, under small yaw angles (below ±15°) the magnitudes of the blade forces are slightly increased, while under high yaw angles (above ±15°) there is a significant decrease. Moreover, the load fluctuations, for the different yaw angles, have the same frequency but different amplitude and oscillation shape. It was concluded that at the above rated wind speed of 15 m/sec, the blade aerodynamic loads are significantly affected by the yaw inflow conditions and the magnitude values of the loads are decreased with increasing yaw angle. It can be concluded that the angle of attack and the tower interference are the utmost variables affecting the yawed turbines.

  16. Petascale Kinetic Simulations in Space Sciences: New Simulations and Data Discovery Techniques and Physics Results

    NASA Astrophysics Data System (ADS)

    Karimabadi, Homa

    2012-03-01

    Recent advances in simulation technology and hardware are enabling breakthrough science where many longstanding problems can now be addressed for the first time. In this talk, we focus on kinetic simulations of the Earth's magnetosphere and magnetic reconnection process which is the key mechanism that breaks the protective shield of the Earth's dipole field, allowing the solar wind to enter the Earth's magnetosphere. This leads to the so-called space weather where storms on the Sun can affect space-borne and ground-based technological systems on Earth. The talk will consist of three parts: (a) overview of a new multi-scale simulation technique where each computational grid is updated based on its own unique timestep, (b) Presentation of a new approach to data analysis that we refer to as Physics Mining which entails combining data mining and computer vision algorithms with scientific visualization to extract physics from the resulting massive data sets. (c) Presentation of several recent discoveries in studies of space plasmas including the role of vortex formation and resulting turbulence in magnetized plasmas.

  17. Simulation of human atherosclerotic femoral plaque tissue: the influence of plaque material model on numerical results

    PubMed Central

    2015-01-01

    discrepancies, future studies should seek to employ vessel-appropriate material models to simulate the response of diseased femoral tissue in order to obtain the most accurate numerical results. PMID:25602515

  18. Melt-rock reaction in the asthenospheric mantle: Perspectives from high-order accurate numerical simulations in 2D and 3D

    NASA Astrophysics Data System (ADS)

    Tirupathi, S.; Schiemenz, A. R.; Liang, Y.; Parmentier, E.; Hesthaven, J.

    2013-12-01

    The style and mode of melt migration in the mantle are important to the interpretation of basalts erupted on the surface. Both grain-scale diffuse porous flow and channelized melt migration have been proposed. To better understand the mechanisms and consequences of melt migration in a heterogeneous mantle, we have undertaken a numerical study of reactive dissolution in an upwelling and viscously deformable mantle where solubility of pyroxene increases upwards. Our setup is similar to that described in [1], except we use a larger domain size in 2D and 3D and a new numerical method. To enable efficient simulations in 3D through parallel computing, we developed a high-order accurate numerical method for the magma dynamics problem using discontinuous Galerkin methods and constructed the problem using the numerical library deal.II [2]. Linear stability analyses of the reactive dissolution problem reveal three dynamically distinct regimes [3] and the simulations reported in this study were run in the stable regime and the unstable wave regime where small perturbations in porosity grows periodically. The wave regime is more relevant to melt migration beneath the mid-ocean ridges but computationally more challenging. Extending the 2D simulations in the stable regime in [1] to 3D using various combinations of sustained perturbations in porosity at the base of the upwelling column (which may result from a viened mantle), we show the geometry and distribution of dunite channel and high-porosity melt channels are highly correlated with inflow perturbation through superposition. Strong nonlinear interactions among compaction, dissolution, and upwelling give rise to porosity waves and high-porosity melt channels in the wave regime. These compaction-dissolution waves have well organized but time-dependent structures in the lower part of the simulation domain. High-porosity melt channels nucleate along nodal lines of the porosity waves, growing downwards. The wavelength scales

  19. Results from teleoperated free-flying spacecraft simulations in the Martin Marietta space operations simulator lab

    NASA Technical Reports Server (NTRS)

    Hartley, Craig S.

    1990-01-01

    To augment the capabilities of the Space Transportation System, NASA has funded studies and developed programs aimed at developing reusable, remotely piloted spacecraft and satellite servicing systems capable of delivering, retrieving, and servicing payloads at altitudes and inclinations beyond the reach of the present Shuttle Orbiters. Since the mid 1970's, researchers at the Martin Marietta Astronautics Group Space Operations Simulation (SOS) Laboratory have been engaged in investigations of remotely piloted and supervised autonomous spacecraft operations. These investigations were based on high fidelity, real-time simulations and have covered a wide range of human factors issues related to controllability. Among these are: (1) mission conditions, including thruster plume impingements and signal time delays; (2) vehicle performance variables, including control authority, control harmony, minimum impulse, and cross coupling of accelerations; (3) maneuvering task requirements such as target distance and dynamics; (4) control parameters including various control modes and rate/displacement deadbands; and (5) display parameters involving camera placement and function, visual aids, and presentation of operational feedback from the spacecraft. This presentation includes a brief description of the capabilities of the SOS Lab to simulate real-time free-flyer operations using live video, advanced technology ground and on-orbit workstations, and sophisticated computer models of on-orbit spacecraft behavior. Sample results from human factors studies in the five categories cited above are provided.

  20. SIMULATION OF DNAPL DISTRIBUTION RESULTING FROM MULTIPLE SOURCES

    EPA Science Inventory

    A three-dimensional and three-phase (water, NAPL and gas) numerical simulator, called NAPL, was employed to study the interaction between DNAPL (PCE) plumes in a variably saturated porous media. Several model verification tests have been performed, including a series of 2-D labo...

  1. FINAL SIMULATION RESULTS FOR DEMONSTRATION CASE 1 AND 2

    SciTech Connect

    David Sloan; Woodrow Fiveland

    2003-10-15

    The goal of this DOE Vision-21 project work scope was to develop an integrated suite of software tools that could be used to simulate and visualize advanced plant concepts. Existing process simulation software did not meet the DOE's objective of ''virtual simulation'' which was needed to evaluate complex cycles. The overall intent of the DOE was to improve predictive tools for cycle analysis, and to improve the component models that are used in turn to simulate equipment in the cycle. Advanced component models are available; however, a generic coupling capability that would link the advanced component models to the cycle simulation software remained to be developed. In the current project, the coupling of the cycle analysis and cycle component simulation software was based on an existing suite of programs. The challenge was to develop a general-purpose software and communications link between the cycle analysis software Aspen Plus{reg_sign} (marketed by Aspen Technology, Inc.), and specialized component modeling packages, as exemplified by industrial proprietary codes (utilized by ALSTOM Power Inc.) and the FLUENT{reg_sign} computational fluid dynamics (CFD) code (provided by Fluent Inc). A software interface and controller, based on an open CAPE-OPEN standard, has been developed and extensively tested. Various test runs and demonstration cases have been utilized to confirm the viability and reliability of the software. ALSTOM Power was tasked with the responsibility to select and run two demonstration cases to test the software--(1) a conventional steam cycle (designated as Demonstration Case 1), and (2) a combined cycle test case (designated as Demonstration Case 2). Demonstration Case 1 is a 30 MWe coal-fired power plant for municipal electricity generation, while Demonstration Case 2 is a 270 MWe, natural gas-fired, combined cycle power plant. Sufficient data was available from the operation of both power plants to complete the cycle configurations. Three runs

  2. Fast Plasma Instrument for MMS: Data Compression Simulation Results

    NASA Technical Reports Server (NTRS)

    Barrie, A.; Adrian, Mark L.; Yeh, P.-S.; Winkert, G. E.; Lobell, J. V.; Vinas, A.F.; Simpson, D. J.; Moore, T. E.

    2008-01-01

    Magnetospheric Multiscale (MMS) mission will study small-scale reconnection structures and their rapid motions from closely spaced platforms using instruments capable of high angular, energy, and time resolution measurements. To meet these requirements, the Fast Plasma Instrument (FPI) consists of eight (8) identical half top-hat electron sensors and eights (8) identical ion sensors and an Instrument Data Processing Unit (IDPU). The sensors (electron or ion) are grouped into pairs whose 6 deg x 180 deg fields-of-view (FOV) are set 90 deg apart. Each sensor is equipped with electrostatic aperture steering to allow the sensor to scan a 45 deg x 180 deg fan about its nominal viewing (0 deg deflection) direction. Each pair of sensors, known as the Dual Electron Spectrometer (DES) and the Dual Ion Spectrometer (DIS), occupies a quadrant on the MMS spacecraft and the combination of the eight electron/ion sensors, employing aperture steering, image the full-sky every 30-ms (electrons) and 150-ms (ions), respectively. To probe the results in the DES complement of a given spacecraft generating 6.5-Mbs(exp -1) of electron data while the DIS generates 1.1-Mbs(exp -1) of ion data yielding an FPI total data rate of 6.6-MBs(exp -1). The FPI electron/ion data is collected by the IDPU then transmitted to the Central Data Instrument Processor (CIDP) on the spacecraft for science interest ranking. Only data sequences that contain the greatest amount of temporal/spatial structure will be intelligently down-linked by the spacecraft. Currently, the FPI data rate allocation to the CIDP is 1.5-Mbs(exp -1). Consequently, the FPI-IDPU must employ data/image compression to meet this CIDP telemetry allocation. Here, we present simulations of the CCSDS 122.0-B-1 algorithm-based compression of the FPI-DES electron data. Compression analysis is based upon a seed of re-processed Cluster/PEACE electron measurements. Topics to be discussed include: review of compression algorithm; data quality

  3. Fast Plasma Instrument for MMS: Data Compression Simulation Results

    NASA Astrophysics Data System (ADS)

    Barrie, A.; Adrian, M. L.; Yeh, P.; Winkert, G.; Lobell, J.; Vinas, A. F.; Simpson, D. G.

    2009-12-01

    Magnetospheric Multiscale (MMS) mission will study small-scale reconnection structures and their rapid motions from closely spaced platforms using instruments capable of high angular, energy, and time resolution measurements. To meet these requirements, the Fast Plasma Instrument (FPI) consists of eight (8) identical half top-hat electron sensors and eight (8) identical ion sensors and an Instrument Data Processing Unit (IDPU). The sensors (electron or ion) are grouped into pairs whose 6° x 180° fields-of-view (FOV) are set 90° apart. Each sensor is equipped with electrostatic aperture steering to allow the sensor to scan a 45° x 180° fan about the its nominal viewing (0° deflection) direction. Each pair of sensors, known as the Dual Electron Spectrometer (DES) and the Dual Ion Spectrometer (DIS), occupies a quadrant on the MMS spacecraft and the combination of the eight electron/ion sensors, employing aperture steering, image the full-sky every 30-ms (electrons) and 150-ms (ions), respectively. To probe the diffusion regions of reconnection, the highest temporal/spatial resolution mode of FPI results in the DES complement of a given spacecraft generating 6.5-Mb s-1 of electron data while the DIS generates 1.1-Mb s-1 of ion data yielding an FPI total data rate of 6.6-Mb s-1. The FPI electron/ion data is collected by the IDPU then transmitted to the Central Data Instrument Processor (CIDP) on the spacecraft for science interest ranking. Only data sequences that contain the greatest amount of temporal/spatial structure will be intelligently down-linked by the spacecraft. Currently, the FPI data rate allocation to the CIDP is 1.5-Mb s-1. Consequently, the FPI-IDPU must employ data/image compression to meet this CIDP telemetry allocation. Here, we present updated simulations of the CCSDS 122.0-B-1 algorithm-based compression of the FPI-DES electron data as well as the FPI-DIS ion data. Compression analysis is based upon a seed of re-processed Cluster

  4. Fast Plasma Instrument for MMS: Data Compression Simulation Results

    NASA Astrophysics Data System (ADS)

    Barrie, A. C.; Adrian, M. L.; Yeh, P.; Winkert, G. E.; Lobell, J. V.; Viňas, A. F.; Simpson, D. G.; Moore, T. E.

    2008-12-01

    Magnetospheric Multiscale (MMS) mission will study small-scale reconnection structures and their rapid motions from closely spaced platforms using instruments capable of high angular, energy, and time resolution measurements. To meet these requirements, the Fast Plasma Instrument (FPI) consists of eight (8) identical half top-hat electron sensors and eight (8) identical ion sensors and an Instrument Data Processing Unit (IDPU). The sensors (electron or ion) are grouped into pairs whose 6° × 180° fields-of-view (FOV) are set 90° apart. Each sensor is equipped with electrostatic aperture steering to allow the sensor to scan a 45° × 180° fan about the its nominal viewing (0° deflection) direction. Each pair of sensors, known as the Dual Electron Spectrometer (DES) and the Dual Ion Spectrometer (DIS), occupies a quadrant on the MMS spacecraft and the combination of the eight electron/ion sensors, employing aperture steering, image the full-sky every 30-ms (electrons) and 150-ms (ions), respectively. To probe the diffusion regions of reconnection, the highest temporal/spatial resolution mode of FPI results in the DES complement of a given spacecraft generating 6.5-Mb s-1 of electron data while the DIS generates 1.1-Mb s-1 of ion data yielding an FPI total data rate of 7.6-Mb s-1. The FPI electron/ion data is collected by the IDPU then transmitted to the Central Data Instrument Processor (CIDP) on the spacecraft for science interest ranking. Only data sequences that contain the greatest amount of temporal/spatial structure will be intelligently down-linked by the spacecraft. Currently, the FPI data rate allocation to the CIDP is 1.5-Mb s-1. Consequently, the FPI-IDPU must employ data/image compression to meet this CIDP telemetry allocation. Here, we present simulations of the CCSDS 122.0-B-1 algorithm- based compression of the FPI-DES electron data. Compression analysis is based upon a seed of re- processed Cluster/PEACE electron measurements. Topics to be

  5. A limited assessment of the ASEP human reliability analysis procedure using simulator examination results

    SciTech Connect

    Gore, B.R.; Dukelow, J.S. Jr.; Mitts, T.M.; Nicholson, W.L.

    1995-10-01

    This report presents a limited assessment of the conservatism of the Accident Sequence Evaluation Program (ASEP) human reliability analysis (HRA) procedure described in NUREG/CR-4772. In particular, the, ASEP post-accident, post-diagnosis, nominal HRA procedure is assessed within the context of an individual`s performance of critical tasks on the simulator portion of requalification examinations administered to nuclear power plant operators. An assessment of the degree to which operator perforn:Lance during simulator examinations is an accurate reflection of operator performance during actual accident conditions was outside the scope of work for this project; therefore, no direct inference can be made from this report about such performance. The data for this study are derived from simulator examination reports from the NRC requalification examination cycle. A total of 4071 critical tasks were identified, of which 45 had been failed. The ASEP procedure was used to estimate human error probability (HEP) values for critical tasks, and the HEP results were compared with the failure rates observed in the examinations. The ASEP procedure was applied by PNL operator license examiners who supplemented the limited information in the examination reports with expert judgment based upon their extensive simulator examination experience. ASEP analyses were performed for a sample of 162 critical tasks selected randomly from the 4071, and the results were used to characterize the entire population. ASEP analyses were also performed for all of the 45 failed critical tasks. Two tests were performed to assess the bias of the ASEP HEPs compared with the data from the requalification examinations. The first compared the average of the ASEP HEP values with the fraction of the population actually failed and it found a statistically significant factor of two bias on the average.

  6. Quiet Clean Short-haul Experimental Engine (QCSEE) over-the-wing engine and control simulation results

    NASA Technical Reports Server (NTRS)

    1978-01-01

    A hybrid-computer simulation of the over the wing turbofan engine was constructed to develop the dynamic design of the control. This engine and control system includes a full authority digital electronic control using compressor stator reset to achieve fast thrust response and a modified Kalman filter to correct for sensor failures. Fast thrust response for powered-lift operations and accurate, fast responding, steady state control of the engine is provided. Simulation results for throttle bursts from 62 to 100 percent takeoff thrust predict that the engine will accelerate from 62 to 95 percent takeoff thrust in one second.

  7. The structural properties of a two-Yukawa fluid: Simulation and analytical results.

    PubMed

    Broccio, Matteo; Costa, Dino; Liu, Yun; Chen, Sow-Hsin

    2006-02-28

    Standard Monte Carlo simulations are carried out to assess the accuracy of theoretical predictions for the structural properties of a model fluid interacting through a hard-core two-Yukawa potential composed of a short-range attractive well next to a hard repulsive core, followed by a smooth, long-range repulsive tail. Theoretical calculations are performed in the framework provided by the Ornstein-Zernike equation, solved either analytically with the mean spherical approximation (MSA) or iteratively with the hypernetted-chain (HNC) closure. Our analysis shows that both theories are generally accurate in a thermodynamic region corresponding to a dense vapor phase around the critical point. For a suitable choice of potential parameters, namely, when the attractive well is deep and/or large enough, the static structure factor displays a secondary low-Q peak. In this case HNC predictions closely follow the simulation results, whereas MSA results progressively worsen the more pronounced this low-Q peak is. We discuss the appearance of such a peak, also experimentally observed in colloidal suspensions and protein solutions, in terms of the formation of equilibrium clusters in the homogeneous fluid.

  8. The structural properties of a two-Yukawa fluid: Simulation and analytical results

    NASA Astrophysics Data System (ADS)

    Broccio, Matteo; Costa, Dino; Liu, Yun; Chen, Sow-Hsin

    2006-02-01

    Standard Monte Carlo simulations are carried out to assess the accuracy of theoretical predictions for the structural properties of a model fluid interacting through a hard-core two-Yukawa potential composed of a short-range attractive well next to a hard repulsive core, followed by a smooth, long-range repulsive tail. Theoretical calculations are performed in the framework provided by the Ornstein-Zernike equation, solved either analytically with the mean spherical approximation (MSA) or iteratively with the hypernetted-chain (HNC) closure. Our analysis shows that both theories are generally accurate in a thermodynamic region corresponding to a dense vapor phase around the critical point. For a suitable choice of potential parameters, namely, when the attractive well is deep and/or large enough, the static structure factor displays a secondary low-Q peak. In this case HNC predictions closely follow the simulation results, whereas MSA results progressively worsen the more pronounced this low-Q peak is. We discuss the appearance of such a peak, also experimentally observed in colloidal suspensions and protein solutions, in terms of the formation of equilibrium clusters in the homogeneous fluid.

  9. Simulations Build Efficacy: Empirical Results from a Four-Week Congressional Simulation

    ERIC Educational Resources Information Center

    Mariani, Mack; Glenn, Brian J.

    2014-01-01

    This article describes a four-week congressional committee simulation implemented in upper level courses on Congress and the Legislative process at two liberal arts colleges. We find that the students participating in the simulation possessed high levels of political knowledge and confidence in their political skills prior to the simulation. An…

  10. Direct drive: Simulations and results from the National Ignition Facility

    SciTech Connect

    Radha, P. B.; Hohenberger, M.; Edgell, D. H.; Marozas, J. A.; Marshall, F. J.; Michel, D. T.; Rosenberg, M. J.; Seka, W.; Shvydky, A.; Boehly, T. R.; Collins, T. J. B.; Campbell, E. M.; Craxton, R. S.; Delettrez, J. A.; Dixit, S. N.; Frenje, J. A.; Froula, D. H.; Goncharov, V. N.; Hu, S. X.; Knauer, J. P.; McCrory, R. L.; McKenty, P. W.; Meyerhofer, D. D.; Moody, J.; Myatt, J. F.; Petrasso, R. D.; Regan, S. P.; Sangster, T. C.; Sio, H.; Skupsky, S.; Zylstra, A.

    2016-04-19

    Here, the direct-drive implosion physics is being investigated at the National Ignition Facility. The primary goal of the experiments is twofold: to validate modeling related to implosion velocity and to estimate the magnitude of hot-electron preheat. Implosion experiments indicate that the energetics is well-modeled when cross-beam energy transfer (CBET) is included in the simulation and an overall multiplier to the CBET gain factor is employed; time-resolved scattered light and scattered-light spectra display the correct trends. Trajectories from backlit images are well modeled, although those from measured self-emission images indicate increased shell thickness and reduced shell density relative to simulations. Sensitivity analyses indicate that the most likely cause for the density reduction is nonuniformity growth seeded by laser imprint and not laser-energy coupling. Hot-electron preheat is at tolerable levels in the ongoing experiments, although it is expected to increase after the mitigation of CBET. Future work will include continued model validation, imprint measurements, and mitigation of CBET and hot-electron preheat.

  11. Direct drive: Simulations and results from the National Ignition Facility

    DOE PAGES

    Radha, P. B.; Hohenberger, M.; Edgell, D. H.; ...

    2016-04-19

    Here, the direct-drive implosion physics is being investigated at the National Ignition Facility. The primary goal of the experiments is twofold: to validate modeling related to implosion velocity and to estimate the magnitude of hot-electron preheat. Implosion experiments indicate that the energetics is well-modeled when cross-beam energy transfer (CBET) is included in the simulation and an overall multiplier to the CBET gain factor is employed; time-resolved scattered light and scattered-light spectra display the correct trends. Trajectories from backlit images are well modeled, although those from measured self-emission images indicate increased shell thickness and reduced shell density relative to simulations. Sensitivitymore » analyses indicate that the most likely cause for the density reduction is nonuniformity growth seeded by laser imprint and not laser-energy coupling. Hot-electron preheat is at tolerable levels in the ongoing experiments, although it is expected to increase after the mitigation of CBET. Future work will include continued model validation, imprint measurements, and mitigation of CBET and hot-electron preheat.« less

  12. Implementation and Simulation Results using Autonomous Aerobraking Development Software

    NASA Technical Reports Server (NTRS)

    Maddock, Robert W.; DwyerCianciolo, Alicia M.; Bowes, Angela; Prince, Jill L. H.; Powell, Richard W.

    2011-01-01

    An Autonomous Aerobraking software system is currently under development with support from the NASA Engineering and Safety Center (NESC) that would move typically ground-based operations functions to onboard an aerobraking spacecraft, reducing mission risk and mission cost. The suite of software that will enable autonomous aerobraking is the Autonomous Aerobraking Development Software (AADS) and consists of an ephemeris model, onboard atmosphere estimator, temperature and loads prediction, and a maneuver calculation. The software calculates the maneuver time, magnitude and direction commands to maintain the spacecraft periapsis parameters within design structural load and/or thermal constraints. The AADS is currently tested in simulations at Mars, with plans to also evaluate feasibility and performance at Venus and Titan.

  13. Stellar populations of stellar halos: Results from the Illustris simulation

    NASA Astrophysics Data System (ADS)

    Cook, B. A.; Conroy, C.; Pillepich, A.; Hernquist, L.

    2016-08-01

    The influence of both major and minor mergers is expected to significantly affect gradients of stellar ages and metallicities in the outskirts of galaxies. Measurements of observed gradients are beginning to reach large radii in galaxies, but a theoretical framework for connecting the findings to a picture of galactic build-up is still in its infancy. We analyze stellar populations of a statistically representative sample of quiescent galaxies over a wide mass range from the Illustris simulation. We measure metallicity and age profiles in the stellar halos of quiescent Illustris galaxies ranging in stellar mass from 1010 to 1012 M ⊙, accounting for observational projection and luminosity-weighting effects. We find wide variance in stellar population gradients between galaxies of similar mass, with typical gradients agreeing with observed galaxies. We show that, at fixed mass, the fraction of stars born in-situ within galaxies is correlated with the metallicity gradient in the halo, confirming that stellar halos contain unique information about the build-up and merger histories of galaxies.

  14. Results from modeling and simulation of chemical downstream etch systems

    SciTech Connect

    Meeks, E.; Vosen, S.R.; Shon, J.W.; Larson, R.S.; Fox, C.A.; Buchenauer

    1996-05-01

    This report summarizes modeling work performed at Sandia in support of Chemical Downstream Etch (CDE) benchmark and tool development programs under a Cooperative Research and Development Agreement (CRADA) with SEMATECH. The Chemical Downstream Etch (CDE) Modeling Project supports SEMATECH Joint Development Projects (JDPs) with Matrix Integrated Systems, Applied Materials, and Astex Corporation in the development of new CDE reactors for wafer cleaning and stripping processes. These dry-etch reactors replace wet-etch steps in microelectronics fabrication, enabling compatibility with other process steps and reducing the use of hazardous chemicals. Models were developed at Sandia to simulate the gas flow, chemistry and transport in CDE reactors. These models address the essential components of the CDE system: a microwave source, a transport tube, a showerhead/gas inlet, and a downstream etch chamber. The models have been used in tandem to determine the evolution of reactive species throughout the system, and to make recommendations for process and tool optimization. A significant part of this task has been in the assembly of a reasonable set of chemical rate constants and species data necessary for successful use of the models. Often the kinetic parameters were uncertain or unknown. For this reason, a significant effort was placed on model validation to obtain industry confidence in the model predictions. Data for model validation were obtained from the Sandia Molecular Beam Mass Spectrometry (MBMS) experiments, from the literature, from the CDE Benchmark Project (also part of the Sandia/SEMATECH CRADA), and from the JDP partners. The validated models were used to evaluate process behavior as a function of microwave-source operating parameters, transport-tube geometry, system pressure, and downstream chamber geometry. In addition, quantitative correlations were developed between CDE tool performance and operation set points.

  15. Achieving Actionable Results from Available Inputs: Metamodels Take Building Energy Simulations One Step Further

    SciTech Connect

    Horsey, Henry; Fleming, Katherine; Ball, Brian; Long, Nicholas

    2016-08-26

    Modeling commercial building energy usage can be a difficult and time-consuming task. The increasing prevalence of optimization algorithms provides one path for reducing the time and difficulty. Many use cases remain, however, where information regarding whole-building energy usage is valuable, but the time and expertise required to run and post-process a large number of building energy simulations is intractable. A relatively underutilized option to accurately estimate building energy consumption in real time is to pre-compute large datasets of potential building energy models, and use the set of results to quickly and efficiently provide highly accurate data. This process is called metamodeling. In this paper, two case studies are presented demonstrating the successful applications of metamodeling using the open-source OpenStudio Analysis Framework. The first case study involves the U.S. Department of Energy's Asset Score Tool, specifically the Preview Asset Score Tool, which is designed to give nontechnical users a near-instantaneous estimated range of expected results based on building system-level inputs. The second case study involves estimating the potential demand response capabilities of retail buildings in Colorado. The metamodel developed in this second application not only allows for estimation of a single building's expected performance, but also can be combined with public data to estimate the aggregate DR potential across various geographic (county and state) scales. In both case studies, the unique advantages of pre-computation allow building energy models to take the place of topdown actuarial evaluations. This paper ends by exploring the benefits of using metamodels and then examines the cost-effectiveness of this approach.

  16. Covariate-Based Assignment to Treatment Groups: Some Simulation Results.

    ERIC Educational Resources Information Center

    Jain, Ram B.; Hsu, Tse-Chi

    1980-01-01

    Six estimators of treatment effect when assignment to treatment groups is based on the covariate are compared in terms of empirical standard errors and percent relative bias. Results show that simple analysis of covariance estimator is not always appropriate. (Author/GK)

  17. Preliminary Benchmarking and MCNP Simulation Results for Homeland Security

    SciTech Connect

    Robert Hayes

    2008-03-01

    The purpose of this article is to create Monte Carlo N-Particle (MCNP) input stacks for benchmarked measurements sufficient for future perturbation studies and analysis. The approach was to utilize historical experimental measurements to recreate the empirical spectral results in MCNP, both qualitatively and quantitatively. Results demonstrate that perturbation analysis of benchmarked MCNP spectra can be used to obtain a better understanding of field measurement results which may be of national interest. If one or more spectral radiation measurements are made in the field and deemed of national interest, the potential source distribution, naturally occurring radioactive material shielding, and interstitial materials can only be estimated in many circumstances. The effects from these factors on the resultant spectral radiation measurements can be very confusing. If benchmarks exist which are sufficiently similar to the suspected configuration, these benchmarks can then be compared to the suspect measurements. Having these benchmarks with validated MCNP input stacks can substantially improve the predictive capability of experts supporting these efforts.

  18. Head Kinematics Resulting from Simulated Blast Loading Scenarios

    DTIC Science & Technology

    2012-09-17

    pressure wave and the body which commonly damages air-filled organs such as the lungs , gastrointestinal tract, and ears. Secondary blast injury...subsequent impact with surrounding obstacles or the ground. Quaternary injury is the result of other factors including burns or inhalation of dust and gas... Woods , W., Feldman, S., Cummings, T., et al. (2011). Survival Risk Assessment for Primary Blast Exposures to the Head. Journal of neurotrauma, 2328

  19. Diffusion of emergency warning: Comparing empirical and simulation results

    SciTech Connect

    Rogers, G.O.; Sorensen, J.H.

    1988-10-01

    As officials consider emergency warning systems to alert the public to potential danger in areas surrounding hazardous facilities, the issue of warning system effectiveness is of critical importance. The purpose of this paper is to present the results of an analysis on the timing of warning system information dissemination including the alert of the public and delivery of a warning message. A general model of the diffusion of emergency warning is specified as a logistic function. Alternative warning systems are characterized in terms of the parameters of the model, which generally constrain the diffusion process to account for judged maximum penetration of each system for various locations and likelihood of being in those places by time of day. The results indicate that the combination of either telephone ring-down warning systems or tone-alert radio systems combined with sirens provide the most effective warning system under conditions of either very rapid onset, or close proximity or both. These results indicate that single technology systems provide adequate warning effectiveness when available warning time (to the public after detection and the decision to warn) extends to as much as an hour. Moreover, telephone ring-down systems provide similar coverage at approximately 30 minutes of available public warning time. 36 refs., 5 figs., 3 tabs.

  20. Aeolian Simulations: A Comparison of Numerical and Experimental Results

    NASA Astrophysics Data System (ADS)

    Mathews, O.; Burr, D. M.; Bridges, N. T.; Lyne, J. E.; Marshall, J. R.; Greeley, R.; White, B. R.; Hills, J.; Smith, K.; Prissel, T. C.; Aliaga-Caro, J. F.

    2010-12-01

    Aeolian processes are a major geomorphic agent on solid planetary bodies with atmospheres (Earth, Mars, Venus, and Titan). This paper describes preliminary efforts to model aeolian saltation using computational fluid dynamics (CFD) and to compare the results with those obtained in wind tunnel testing conducted in the Planetary Aeolian Laboratory at NASA Ames Research Center at ambient pressure. The end goal of the project is to develop an experimentally validated CFD approach for modeling aeolian sediment transport on Titan and other planetary bodies. The MARSWIT open-circuit tunnel in this work was specifically designed for atmospheric boundary layer studies. It is a variable-speed, continuous flow tunnel with a test section 1.0 m by 1.2 m in size; the tunnel is able to operate at pressures from 10 millibar to one atmosphere. Flow trips near the tunnel inlet ensure a fully developed, turbulent boundary layer in the test section. Wind speed and axial velocity profiles can be measured with a traversing pitot tube. In this study, sieved walnut shell particles (Greeley et al. 1976) with a density of ~1.1 g/cm3 were used to correlate the low gravity conditions and low sediment density on a body of interest to that of Earth. This sediment was placed in the tunnel, and the freestream airspeed raised to 5.4 m/s. A Phantom v12 camera imaged the resulting particle motion at 1000 frames per second, which was analyzed with ImageJ open-source software (Fig. 1). Airflow in the tunnel was modeled with FLUENT, a commercial CFD program. The turbulent scheme used in FLUENT to obtain closed-form solutions to the Navier-Stokes equations was a 1st Order, k-epsilon model. These methods produced computational velocity profiles that agree with experimental data to within 5-10%. Once modeling of the flow field had been achieved, a Euler-Lagrangian scheme was employed, treating the particles as spheres and tracking each particle at its center. The particles are assumed to interact with

  1. Numerical Simulation of Micronozzles with Comparison to Experimental Results

    NASA Astrophysics Data System (ADS)

    Thornber, B.; Chesta, E.; Gloth, O.; Brandt, R.; Schwane, R.; Perigo, D.; Smith, P.

    2004-10-01

    A numerical analysis of conical micronozzle flows has been conducted using the commercial software package CFD-RC FASTRAN [13]. The numerical results have been validated by comparison with direct thrust and mass flow measurements recently performed in ESTEC Propulsion Laboratory on Polyflex Space Ltd. 10mN Cold-Gas thrusters in the frame of ESA CryoSat mission. The flow is viscous dominated, with a throat Reynolds number of 5000, and the relatively large length of the nozzle causes boundary layer effects larger than usual for nozzles of this size. This paper discusses in detail the flow physics such as boundary layer growth and structure, and the effects of rarefaction. Furthermore a number of different domain sizes and exit boundary conditions are used to determine the optimum combination of computational time and accuracy.

  2. Preliminary Benchmarking Efforts and MCNP Simulation Results for Homeland Security

    SciTech Connect

    Robert Hayes

    2008-04-18

    It is shown in this work that basic measurements made from well defined source detector configurations can be readily converted in to benchmark quality results by which Monte Carlo N-Particle (MCNP) input stacks can be validated. Specifically, a recent measurement made in support of national security at the Nevada Test Site (NTS) is described with sufficient detail to be submitted to the American Nuclear Society’s (ANS) Joint Benchmark Committee (JBC) for consideration as a radiation measurement benchmark. From this very basic measurement, MCNP input stacks are generated and validated both in predicted signal amplitude and spectral shape. Not modeled at this time are those perturbations from the more recent pulse height light (PHL) tally feature, although what spectral deviations are seen can be largely attributed to not including this small correction. The value of this work is as a proof-of-concept demonstration that with well documented historical testing can be converted into formal radiation measurement benchmarks. This effort would support virtual testing of algorithms and new detector configurations.

  3. Stereotactic hypofractionated accurate radiotherapy of the prostate (SHARP), 33.5 Gy in five fractions for localized disease: First clinical trial results

    SciTech Connect

    Madsen, Berit L. . E-mail: ronblm@vmmc.org; Hsi, R. Alex; Pham, Huong T.; Fowler, Jack F.; Esagui, Laura C.; Corman, John

    2007-03-15

    Purpose: To evaluate the feasibility and toxicity of stereotactic hypofractionated accurate radiotherapy (SHARP) for localized prostate cancer. Methods and Materials: A Phase I/II trial of SHARP performed for localized prostate cancer using 33.5 Gy in 5 fractions, calculated to be biologically equivalent to 78 Gy in 2 Gy fractions ({alpha}/{beta} ratio of 1.5 Gy). Noncoplanar conformal fields and daily stereotactic localization of implanted fiducials were used for treatment. Genitourinary (GU) and gastrointestinal (GI) toxicity were evaluated by American Urologic Association (AUA) score and Common Toxicity Criteria (CTC). Prostate-specific antigen (PSA) values and self-reported sexual function were recorded at specified follow-up intervals. Results: The study includes 40 patients. The median follow-up is 41 months (range, 21-60 months). Acute toxicity Grade 1-2 was 48.5% (GU) and 39% (GI); 1 acute Grade 3 GU toxicity. Late Grade 1-2 toxicity was 45% (GU) and 37% (GI). No late Grade 3 or higher toxicity was reported. Twenty-six patients reported potency before therapy; 6 (23%) have developed impotence. Median time to PSA nadir was 18 months with the majority of nadirs less than 1.0 ng/mL. The actuarial 48-month biochemical freedom from relapse is 70% for the American Society for Therapeutic Radiology and Oncology definition and 90% by the alternative nadir + 2 ng/mL failure definition. Conclusions: SHARP for localized prostate cancer is feasible with minimal acute or late toxicity. Dose escalation should be possible.

  4. Test Results from a Direct Drive Gas Reactor Simulator Coupled to a Brayton Power Conversion Unit

    NASA Technical Reports Server (NTRS)

    Hervol, David S.; Briggs, Maxwell H.; Owen, Albert K.; Bragg-Sitton, Shannon M.; Godfroy, Thomas J.

    2010-01-01

    Component level testing of power conversion units proposed for use in fission surface power systems has typically been done using relatively simple electric heaters for thermal input. These heaters do not adequately represent the geometry or response of proposed reactors. As testing of fission surface power systems transitions from the component level to the system level it becomes necessary to more accurately replicate these reactors using reactor simulators. The Direct Drive Gas-Brayton Power Conversion Unit test activity at the NASA Glenn Research Center integrates a reactor simulator with an existing Brayton test rig. The response of the reactor simulator to a change in Brayton shaft speed is shown as well as the response of the Brayton to an insertion of reactivity, corresponding to a drum reconfiguration. The lessons learned from these tests can be used to improve the design of future reactor simulators which can be used in system level fission surface power tests.

  5. The simulation of optical diagnostics for crystal growth - Models and results

    NASA Astrophysics Data System (ADS)

    Banish, M. R.; Clark, R. L.; Kathman, A. D.; Lawson, S. M.

    A computer simulation of a Two Color Holographic Interferometric (TCHI) optical system was performed using a physical (wave) optics model. This model accurately simulates propagation through time-varying, 2-D or 3-D concentration and temperature fields as a wave phenomenon. The model calculates wavefront deformations that can be used to generate fringe patterns. This simulation modeled a proposed TriGlycine sulphate TGS flight experiment by propagating through the simplified onion-like refractive index distribution of the growing crystal and calculating the recorded wavefront deformation. The phase of this wavefront was used to generate sample interferograms that map index of refraction variation. Two such fringe patterns, generated at different wavelengths, were used to extract the original temperature and concentration field characteristics within the growth chamber. This proves feasibility for this TCHI crystal growth diagnostic technique. This simulation provides feedback to the experimental design process.

  6. Dispersion curves from short-time molecular dynamics simulation. 1. Diatomic chain results

    SciTech Connect

    Noid, D.W.; Broocks, B.T.; Gray, S.K.; Marple, S.L.

    1988-06-16

    The multiple signal classification method (MUSIC) for frequency estimation is used to compute the frequency dispersion curves of a diatomic chain from the time-dependent structure factor. In this paper, the authors demonstrate that MUSIC can accurately determine the frequencies from very short time trajectories. MUSIC is also used to show how the frequencies can vary in time, i.e., along a trajectory. The method is ideally suited for analyzing molecular dynamics simulations of large systems.

  7. Fast and accurate methods for the performance testing of highly-efficient c-Si photovoltaic modules using a 10 ms single-pulse solar simulator and customized voltage profiles

    NASA Astrophysics Data System (ADS)

    Virtuani, A.; Rigamonti, G.; Friesen, G.; Chianese, D.; Beljean, P.

    2012-11-01

    Performance testing of highly efficient, highly capacitive c-Si modules with pulsed solar simulators requires particular care. These devices in fact usually require a steady-state solar simulator or pulse durations longer than 100-200 ms in order to avoid measurement artifacts. The aim of this work was to validate an alternative method for the testing of highly capacitive c-Si modules using a 10 ms single pulse solar simulator. Our approach attempts to reconstruct a quasi-steady-state I-V (current-voltage) curve of a highly capacitive device during one single 10 ms flash by applying customized voltage profiles--in place of a conventional V ramp—to the terminals of the device under test. The most promising results were obtained by using V profiles which we name ‘dragon-back’ (DB) profiles. When compared to the reference I-V measurement (obtained by using a multi-flash approach with approximately 20 flashes), the DB V profile method provides excellent results with differences in the estimation of Pmax (as well as of Isc, Voc and FF) below ±0.5%. For the testing of highly capacitive devices the method is accurate, fast (two flashes—possibly one—required), cost-effective and has proven its validity with several technologies making it particularly interesting for in-line testing.

  8. Preliminary results for a two-dimensional simulation of the working process of a Stirling engine

    SciTech Connect

    Makhkamov, K.K.; Ingham, D.B.

    1998-07-01

    Stirling engines have several potential advantages over existing types of engines, in particular they can use renewable energy sources for power production and their performance meets the demands on the environmental security. In order to design Stirling Engines properly, and to put into effect their potential performance, it is important to more accurately mathematically simulate its working process. At present, a series of very important mathematical models are used for describing the working process of Stirling Engines and these are, in general, classified as models of three levels. All the models consider one-dimensional schemes for the engine and assume a uniform fluid velocity, temperature and pressure profiles at each plane of the internal gas circuit of the engine. The use of two-dimensional CFD models can significantly extend the capabilities for the detailed analysis of the complex heat transfer and gas dynamic processes which occur in the internal gas circuit, as well as in the external circuit of the engine. In this paper a two-dimensional simplified frame (no construction walls) calculation scheme for the Stirling Engine has been assumed and the standard {kappa}-{var{underscore}epsilon} turbulence model has been used for the analysis of the engine working process. The results obtained show that the use of two-dimensional CFD models gives the possibility of gaining a much greater insight into the fluid flow and heat transfer processes which occur in Stirling Engines.

  9. Simulated changes in ground-water levels resulting from proposed phosphate mining, west-central Florida; preliminary results

    USGS Publications Warehouse

    Wilson, William Edward

    1977-01-01

    A digital model of two-dimensional ground-water flow was used to simulate projected changes in the Floridan aquifer potentiometric surface in 1985 and 2000, resulting from proposed ground-water developments by the phosphate mining industry in west-central Florida. The .model was calibrated under steady-state conditions to simulate the September 1975 potentiometric surface. Under one development plan, existing phosphate mines in Polk County would continue to withdraw ground water at 1975 rates, until phased out as the ore is depleted; no new mines would be introduced. Preliminary results indicate that under this plan, maximum simulated recovery of the potentiometric surface is 11.9 feet by 1985 and 36.5 feet by 2000. Under an alternative plan, all proposed mines in Polk, Hardee, DeSoto, Hillsborough and Manatee Counties would begin operations: in addition to the continuation and phasing out of existing mines. Preliminary results indicate that the potentiometric surface would generally recover in Polk County and decline elsewhere in the modeled area. Maximum simulated recovery is 4.5 feet by 1985 and 29.6 feet by 2000; maximum simulated drawdown is 15.1 feet by 1985 and feet by 2000. All results are preliminary and subject to revision as the investigation continues.

  10. Accurate measurements of vadose zone fluxes using automated equilibrium tension plate lysimeters: A synopsis of results from the Spydia research facility, New Zealand.

    NASA Astrophysics Data System (ADS)

    Wöhling, Thomas; Barkle, Greg; Stenger, Roland; Moorhead, Brian; Wall, Aaron; Clague, Juliet

    2014-05-01

    Automated equilibrium tension plate lysimeters (AETLs) are arguably the most accurate method to measure unsaturated water and contaminant fluxes below the root zone at the scale of up to 1 m². The AETL technique utilizes a porous sintered stainless-steel plate to provide a comparatively large sampling area with a continuously controlled vacuum that is in "equilibrium" with the surrounding vadose zone matric pressure to ensure measured fluxes represent those under undisturbed conditions. This novel lysimeter technique was used at an intensive research site for investigations of contaminant pathways from the land surface to the groundwater on a sheep and beef farm under pastoral land use in the Tutaeuaua subcatchment, New Zealand. The Spydia research facility was constructed in 2005 and was fully operational between 2006 and 2011. Extending from a central access caisson, 15 separately controlled AETLs with 0.2 m² surface area were installed at five depths between 0.4 m and 5.1 m into the undisturbed volcanic vadose zone materials. The unique setup of the facility ensured minimum interference of the experimental equipment and external factors with the measurements. Over the period of more than five years, a comprehensive data set was collected at each of the 15 AETL locations which comprises of time series of soil water flux, pressure head, volumetric water contents, and soil temperature. The soil water was regularly analysed for EC, pH, dissolved carbon, various nitrogen compounds (including nitrate, ammonia, and organic N), phosphorus, bromide, chloride, sulphate, silica, and a range of other major ions, as well as for various metals. Climate data was measured directly at the site (rainfall) and a climate station at 500m distance. The shallow groundwater was sampled at three different depths directly from the Spydia caisson and at various observation wells surrounding the facility. Two tracer experiments were conducted at the site in 2009 and 2010. In the 2009

  11. Basin scale reactive-transport simulations of CO2 leakage and resulting metal transport in a shallow drinking water aquifer

    NASA Astrophysics Data System (ADS)

    Navarre-Sitchler, A.; Maxwell, R. M.; Hammond, G. E.; Lichtner, P. C.

    2011-12-01

    solubility buffers the lead concentration to low values. Results from these models suggest that using pure end member metal sulfides to simulate metal release in aquifers impacted by a CO2 leak may be problematic. Additional model simulations run on a higher resolution grid where hydraulic conductivity is assigned at each grid cell geostatistically to more accurately simulate metal behavior, will also be presented.

  12. Coupling geostatistics to detailed reservoir description allows better visualization and more accurate characterization/simulation of turbidite reservoirs: Elk Hills oil field, California

    SciTech Connect

    Allan, M.E.; Wilson, M.L.; Wightman, J. )

    1996-01-01

    The Elk Hills giant oilfield, located in the southern San Joaquin Valley of California, has produced 1.1 billion barrels of oil from Miocene and shallow Pliocene reservoirs. 65% of the current 64,000 BOPD production is from the pressure-supported, deeper Miocene turbidite sands. In the turbidite sands of the 31 S structure, large porosity permeability variations in the Main Body B and Western 31 S sands cause problems with the efficiency of the waterflooding. These variations have now been quantified and visualized using geostatistics. The end result is a more detailed reservoir characterization for simulation. Traditional reservoir descriptions based on marker correlations, cross-sections and mapping do not provide enough detail to capture the short-scale stratigraphic heterogeneity needed for adequate reservoir simulation. These deterministic descriptions are inadequate to tie with production data as the thinly bedded sand/shale sequences blur into a falsely homogenous picture. By studying the variability of the geologic petrophysical data vertically within each wellbore and spatially from well to well, a geostatistical reservoir description has been developed. It captures the natural variability of the sands and shales that was lacking from earlier work. These geostatistical studies allow the geologic and petrophysical characteristics to be considered in a probabilistic model. The end-product is a reservoir description that captures the variability of the reservoir sequences and can be used as a more realistic starting point for history matching and reservoir simulation.

  13. Coupling geostatistics to detailed reservoir description allows better visualization and more accurate characterization/simulation of turbidite reservoirs: Elk Hills oil field, California

    SciTech Connect

    Allan, M.E.; Wilson, M.L.; Wightman, J.

    1996-12-31

    The Elk Hills giant oilfield, located in the southern San Joaquin Valley of California, has produced 1.1 billion barrels of oil from Miocene and shallow Pliocene reservoirs. 65% of the current 64,000 BOPD production is from the pressure-supported, deeper Miocene turbidite sands. In the turbidite sands of the 31 S structure, large porosity & permeability variations in the Main Body B and Western 31 S sands cause problems with the efficiency of the waterflooding. These variations have now been quantified and visualized using geostatistics. The end result is a more detailed reservoir characterization for simulation. Traditional reservoir descriptions based on marker correlations, cross-sections and mapping do not provide enough detail to capture the short-scale stratigraphic heterogeneity needed for adequate reservoir simulation. These deterministic descriptions are inadequate to tie with production data as the thinly bedded sand/shale sequences blur into a falsely homogenous picture. By studying the variability of the geologic & petrophysical data vertically within each wellbore and spatially from well to well, a geostatistical reservoir description has been developed. It captures the natural variability of the sands and shales that was lacking from earlier work. These geostatistical studies allow the geologic and petrophysical characteristics to be considered in a probabilistic model. The end-product is a reservoir description that captures the variability of the reservoir sequences and can be used as a more realistic starting point for history matching and reservoir simulation.

  14. Analysis procedures and subjective flight results of a simulator validation and cue fidelity experiment

    NASA Technical Reports Server (NTRS)

    Carr, Peter C.; Mckissick, Burnell T.

    1988-01-01

    A joint experiment to investigate simulator validation and cue fidelity was conducted by the Dryden Flight Research Facility of NASA Ames Research Center (Ames-Dryden) and NASA Langley Research Center. The primary objective was to validate the use of a closed-loop pilot-vehicle mathematical model as an analytical tool for optimizing the tradeoff between simulator fidelity requirements and simulator cost. The validation process includes comparing model predictions with simulation and flight test results to evaluate various hypotheses for differences in motion and visual cues and information transfer. A group of five pilots flew air-to-air tracking maneuvers in the Langley differential maneuvering simulator and visual motion simulator and in an F-14 aircraft at Ames-Dryden. The simulators used motion and visual cueing devices including a g-seat, a helmet loader, wide field-of-view horizon, and a motion base platform.

  15. A simulation study of the flight dynamics of elastic aircraft. Volume 1: Experiment, results and analysis

    NASA Technical Reports Server (NTRS)

    Waszak, Martin R.; Davidson, John B.; Schmidt, David K.

    1987-01-01

    The simulation experiment described addresses the effects of structural flexibility on the dynamic characteristics of a generic family of aircraft. The simulation was performed using the NASA Langley VMS simulation facility. The vehicle models were obtained as part of this research. The simulation results include complete response data and subjective pilot ratings and comments and so allow a variety of analyses. The subjective ratings and analysis of the time histories indicate that increased flexibility can lead to increased tracking errors, degraded handling qualities, and changes in the frequency content of the pilot inputs. These results, furthermore, are significantly affected by the visual cues available to the pilot.

  16. CORRECTING FOR INTERSTELLAR SCATTERING DELAY IN HIGH-PRECISION PULSAR TIMING: SIMULATION RESULTS

    SciTech Connect

    Palliyaguru, Nipuni; McLaughlin, Maura; Stinebring, Daniel; Demorest, Paul; Jones, Glenn E-mail: maura.mclaughlin@mail.wvu.edu E-mail: pdemores@nrao.edu

    2015-12-20

    Light travel time changes due to gravitational waves (GWs) may be detected within the next decade through precision timing of millisecond pulsars. Removal of frequency-dependent interstellar medium (ISM) delays due to dispersion and scattering is a key issue in the detection process. Current timing algorithms routinely correct pulse times of arrival (TOAs) for time-variable delays due to cold plasma dispersion. However, none of the major pulsar timing groups correct for delays due to scattering from multi-path propagation in the ISM. Scattering introduces a frequency-dependent phase change in the signal that results in pulse broadening and arrival time delays. Any method to correct the TOA for interstellar propagation effects must be based on multi-frequency measurements that can effectively separate dispersion and scattering delay terms from frequency-independent perturbations such as those due to a GW. Cyclic spectroscopy, first described in an astronomical context by Demorest (2011), is a potentially powerful tool to assist in this multi-frequency decomposition. As a step toward a more comprehensive ISM propagation delay correction, we demonstrate through a simulation that we can accurately recover impulse response functions (IRFs), such as those that would be introduced by multi-path scattering, with a realistic signal-to-noise ratio (S/N). We demonstrate that timing precision is improved when scatter-corrected TOAs are used, under the assumptions of a high S/N and highly scattered signal. We also show that the effect of pulse-to-pulse “jitter” is not a serious problem for IRF reconstruction, at least for jitter levels comparable to those observed in several bright pulsars.

  17. Molecular dynamics and docking simulations as a proof of high flexibility in E. coli FabH and its relevance for accurate inhibitor modeling

    NASA Astrophysics Data System (ADS)

    Pérez-Castillo, Yunierkis; Froeyen, Matheus; Cabrera-Pérez, Miguel Ángel; Nowé, Ann

    2011-04-01

    Bacterial β-ketoacyl-acyl carrier protein synthase III (FabH) has become an attractive target for the development of new antibacterial agents which can overcome the increased resistance of these pathogens to antibiotics in clinical use. Despite several efforts have been dedicated to find inhibitors for this enzyme, it is not a straightforward task, mainly due its high flexibility which makes difficult the structure-based design of FabH inhibitors. Here, we present for the first time a Molecular Dynamics (MD) study of the E. colil FabH enzyme to explore its conformational space. We compare the flexibility of this enzyme for the unliganded protein and an enzyme-inhibitor complex and find a correspondence between our modeling results and the experimental evidence previously reported for this enzyme. Furthermore, through a 100 ns MD simulation of the unliganded enzyme we extract useful information related to the concerted motions that take place along the principal components of displacement. We also establish a relation between the presence of water molecules in the oxyanion hole with the conformational stability of structural important loops. Representative conformations of the binding pocket along the whole trajectory of the unliganded protein are selected through cluster analysis and we find that they contain a conformational diversity which is not provided by the X-ray structures of ecFabH. As a proof of this last hypothesis, we use a set of 10 FabH inhibitors and show that they cannot be correctly modeled in any available X-ray structure, while by using our set of conformations extracted from the MD simulations, this task can be accomplish. Finally, we show the ability of short MD simulations for the refinement of the docking binding poses and for MM-PBSA calculations to predict stable protein-inhibitor complexes in this enzyme.

  18. Composition, preparation, and gas generation results from simulated wastes of Tank 241-SY-101

    SciTech Connect

    Bryan, S.A.; Pederson, L.R.

    1994-08-01

    This document reviews the preparation and composition of simulants that have been developed to mimic the wastes temporarily stored in Tank 241-SY-101 at Hanford. The kinetics and stoichiometry of gases that are generated using these simulants are also compared, considering the roles of hydroxide, chloride, and transition metal ions; the identities of organic constituents; and the effects of dilution, radiation, and temperature. Work described in this report was conducted for the Flammable Gas Safety Program at Pacific Northwest Laboratory, (a) whose purpose is to develop information that is necessary to mitigate potential safety hazards associated with waste tanks at the Hanford Site. The goal of this research and of related efforts at the Georgia Institute of Technology (GIT), Argonne National Laboratory (ANL), and Westinghouse Hanford Company (WHC) is to determine the thermal and thermal/radiolytic mechanisms by which flammable and other gases are produced in Hanford wastes, emphasizing those stored in Tank 241-SY-101. A variety of Tank 241-SY-101 simulants have been developed to date. The use of simulants in laboratory testing activities provides a number of advantages, including elimination of radiological risks to researchers, lower costs associated with experimentation, and the ability to systematically alter simulant compositions to study the chemical mechanisms of reactions responsible for gas generation. The earliest simulants contained the principal inorganic components of the actual waste and generally a single complexant such as N-(2-hydroxyethyl) ethylenediaminetriacetic acid (HEDTA) or ethylenediaminetriacetic acid (EDTA). Both homogeneous and heterogeneous compositional forms were developed. Aggressive core sampling and analysis activities conducted during Windows C and E provided information that was used to design new simulants that more accurately reflected major and minor inorganic components.

  19. Results of GEANT simulations and comparison with first experiments at DANCE.

    SciTech Connect

    Reifarth, R.; Bredeweg, T. A.; Browne, J. C.; Esch, E. I.; Haight, R. C.; O'Donnell, J. M.; Kronenberg, A.; Rundberg, R. S.; Ullmann, J. L.; Vieira, D. J.; Wilhelmy, J. B.; Wouters, J. M.

    2003-07-29

    This report describes intensive Monte Carlo simulations carried out to be compared with the results of the first run cycle with DANCE (Detector for Advanced Neutron Capture Experiments). The experimental results were gained during the commissioning phase 2002/2003 with only a part of the array. Based on the results of these simulations the most important items to be improved before the next experiments will be addressed.

  20. DoSSiER: Database of scientific simulation and experimental results

    SciTech Connect

    Wenzel, Hans; Yarba, Julia; Genser, Krzystof; Elvira, Daniel; Pokorski, Witold; Carminati, Federico; Konstantinov, Dmitri; Ribon, Alberto; Folger, Gunter; Dotti, Andrea

    2016-08-01

    The Geant4, GeantV and GENIE collaborations regularly perform validation and regression tests for simulation results. DoSSiER (Database of Scientific Simulation and Experimental Results) is being developed as a central repository to store the simulation results as well as the experimental data used for validation. DoSSiER can be easily accessed via a web application. In addition, a web service allows for programmatic access to the repository to extract records in json or xml exchange formats. In this paper, we describe the functionality and the current status of various components of DoSSiER as well as the technology choices we made.

  1. A method for data handling numerical results in parallel OpenFOAM simulations

    SciTech Connect

    Anton, Alin; Muntean, Sebastian

    2015-12-31

    Parallel computational fluid dynamics simulations produce vast amount of numerical result data. This paper introduces a method for reducing the size of the data by replaying the interprocessor traffic. The results are recovered only in certain regions of interest configured by the user. A known test case is used for several mesh partitioning scenarios using the OpenFOAM toolkit{sup ®}[1]. The space savings obtained with classic algorithms remain constant for more than 60 Gb of floating point data. Our method is most efficient on large simulation meshes and is much better suited for compressing large scale simulation results than the regular algorithms.

  2. Accurate Finite Difference Algorithms

    NASA Technical Reports Server (NTRS)

    Goodrich, John W.

    1996-01-01

    Two families of finite difference algorithms for computational aeroacoustics are presented and compared. All of the algorithms are single step explicit methods, they have the same order of accuracy in both space and time, with examples up to eleventh order, and they have multidimensional extensions. One of the algorithm families has spectral like high resolution. Propagation with high order and high resolution algorithms can produce accurate results after O(10(exp 6)) periods of propagation with eight grid points per wavelength.

  3. Evaluating the Effects of Ankle-Foot Orthosis Mechanical Property Assumptions on Gait Simulation Muscle Force Results.

    PubMed

    Hegarty, Amy K; Petrella, Anthony J; Kurz, Max J; Silverman, Anne K

    2017-03-01

    Musculoskeletal modeling and simulation techniques have been used to gain insights into movement disabilities for many populations, such as ambulatory children with cerebral palsy (CP). The individuals who can benefit from these techniques are often limited to those who can walk without assistive devices, due to challenges in accurately modeling these devices. Specifically, many children with CP require the use of ankle-foot orthoses (AFOs) to improve their walking ability, and modeling these devices is important to understand their role in walking mechanics. The purpose of this study was to quantify the effects of AFO mechanical property assumptions, including rotational stiffness, damping, and equilibrium angle of the ankle and subtalar joints, on the estimation of lower-limb muscle forces during stance for children with CP. We analyzed two walking gait cycles for two children with CP while they were wearing their own prescribed AFOs. We generated 1000-trial Monte Carlo simulations for each of the walking gait cycles, resulting in a total of 4000 walking simulations. We found that AFO mechanical property assumptions influenced the force estimates for all the muscles in the model, with the ankle muscles having the largest resulting variability. Muscle forces were most sensitive to assumptions of AFO ankle and subtalar stiffness, which should therefore be measured when possible. Muscle force estimates were less sensitive to estimates of damping and equilibrium angle. When stiffness measurements are not available, limitations on the accuracy of muscle force estimates for all the muscles in the model, especially the ankle muscles, should be acknowledged.

  4. MO-A-BRD-10: A Fast and Accurate GPU-Based Proton Transport Monte Carlo Simulation for Validating Proton Therapy Treatment Plans

    SciTech Connect

    Wan Chan Tseung, H; Ma, J; Beltran, C

    2014-06-15

    Purpose: To build a GPU-based Monte Carlo (MC) simulation of proton transport with detailed modeling of elastic and non-elastic (NE) protonnucleus interactions, for use in a very fast and cost-effective proton therapy treatment plan verification system. Methods: Using the CUDA framework, we implemented kernels for the following tasks: (1) Simulation of beam spots from our possible scanning nozzle configurations, (2) Proton propagation through CT geometry, taking into account nuclear elastic and multiple scattering, as well as energy straggling, (3) Bertini-style modeling of the intranuclear cascade stage of NE interactions, and (4) Simulation of nuclear evaporation. To validate our MC, we performed: (1) Secondary particle yield calculations in NE collisions with therapeutically-relevant nuclei, (2) Pencil-beam dose calculations in homogeneous phantoms, (3) A large number of treatment plan dose recalculations, and compared with Geant4.9.6p2/TOPAS. A workflow was devised for calculating plans from a commercially available treatment planning system, with scripts for reading DICOM files and generating inputs for our MC. Results: Yields, energy and angular distributions of secondaries from NE collisions on various nuclei are in good agreement with the Geant4.9.6p2 Bertini and Binary cascade models. The 3D-gamma pass rate at 2%–2mm for 70–230 MeV pencil-beam dose distributions in water, soft tissue, bone and Ti phantoms is 100%. The pass rate at 2%–2mm for treatment plan calculations is typically above 98%. The net computational time on a NVIDIA GTX680 card, including all CPU-GPU data transfers, is around 20s for 1×10{sup 7} proton histories. Conclusion: Our GPU-based proton transport MC is the first of its kind to include a detailed nuclear model to handle NE interactions on any nucleus. Dosimetric calculations demonstrate very good agreement with Geant4.9.6p2/TOPAS. Our MC is being integrated into a framework to perform fast routine clinical QA of pencil

  5. Simulation loop between cad systems, GEANT-4 and GeoModel: Implementation and results

    NASA Astrophysics Data System (ADS)

    Sharmazanashvili, A.; Tsutskiridze, Niko

    2016-09-01

    Compare analysis of simulation and as-built geometry descriptions of detector is important field of study for data_vs_Monte-Carlo discrepancies. Shapes consistency and detalization is not important while adequateness of volumes and weights of detector components are essential for tracking. There are 2 main reasons of faults of geometry descriptions in simulation: (1) Difference between simulated and as-built geometry descriptions; (2) Internal inaccuracies of geometry transformations added by simulation software infrastructure itself. Georgian Engineering team developed hub on the base of CATIA platform and several tools enabling to read in CATIA different descriptions used by simulation packages, like XML->CATIA; VP1->CATIA; Geo-Model->CATIA; Geant4->CATIA. As a result it becomes possible to compare different descriptions with each other using the full power of CATIA and investigate both classes of reasons of faults of geometry descriptions. Paper represents results of case studies of ATLAS Coils and End-Cap toroid structures.

  6. Comparison between simulations and lab results on the ASSIST test-bench

    NASA Astrophysics Data System (ADS)

    Le Louarn, Miska; Madec, Pierre-Yves; Kolb, Johann; Paufique, Jerome; Oberti, Sylvain; La Penna, Paolo; Arsenault, Robin

    2016-07-01

    We present the latest comparison results between laboratory tests carried out on the ASSIST test bench and Octopus end-to end simulations. We simulated, as closely to the lab conditions as possible, the different AOF modes (Maintenance and commissioning mode (SCAO), GRAAL (GLAO in the near IR), Galacsi Wide Field mode (GLAO in the visible) and Galacsi narrow field mode (LTAO in the visible)). We then compared the simulation results to the ones obtained on the lab bench. Several aspects were investigated, like number of corrected modes, turbulence wind speeds, LGS photon flux etc. The agreement between simulations and lab is remarkably good for all investigated parameters, giving great confidence in both simulation tool and performance of the AO system in the lab.

  7. Lac Repressor Mediated DNA Looping: Monte Carlo Simulation of Constrained DNA Molecules Complemented with Current Experimental Results

    PubMed Central

    Biton, Yoav Y.; Kumar, Sandip; Dunlap, David; Swigon, David

    2014-01-01

    Tethered particle motion (TPM) experiments can be used to detect time-resolved loop formation in a single DNA molecule by measuring changes in the length of a DNA tether. Interpretation of such experiments is greatly aided by computer simulations of DNA looping which allow one to analyze the structure of the looped DNA and estimate DNA-protein binding constants specific for the loop formation process. We here present a new Monte Carlo scheme for accurate simulation of DNA configurations subject to geometric constraints and apply this method to Lac repressor mediated DNA looping, comparing the simulation results with new experimental data obtained by the TPM technique. Our simulations, taking into account the details of attachment of DNA ends and fluctuations of the looped subsegment of the DNA, reveal the origin of the double-peaked distribution of RMS values observed by TPM experiments by showing that the average RMS value for anti-parallel loop types is smaller than that of parallel loop types. The simulations also reveal that the looping probabilities for the anti-parallel loop types are significantly higher than those of the parallel loop types, even for loops of length 600 and 900 base pairs, and that the correct proportion between the heights of the peaks in the distribution can only be attained when loops with flexible Lac repressor conformation are taken into account. Comparison of the in silico and in vitro results yields estimates for the dissociation constants characterizing the binding affinity between O1 and Oid DNA operators and the dimeric arms of the Lac repressor. PMID:24800809

  8. A Novel Simulation Technician Laboratory Design: Results of a Survey-Based Study

    PubMed Central

    Hughes, Patrick G; Friedl, Ed; Ortiz Figueroa, Fabiana; Cepeda Brito, Jose R; Frey, Jennifer; Birmingham, Lauren E; Atkinson, Steven Scott

    2016-01-01

    Objective  The purpose of this study was to elicit feedback from simulation technicians prior to developing the first simulation technician-specific simulation laboratory in Akron, OH. Background Simulation technicians serve a vital role in simulation centers within hospitals/health centers around the world. The first simulation technician degree program in the US has been approved in Akron, OH. To satisfy the requirements of this program and to meet the needs of this special audience of learners, a customized simulation lab is essential.  Method A web-based survey was circulated to simulation technicians prior to completion of the lab for the new program. The survey consisted of questions aimed at identifying structural and functional design elements of a novel simulation center for the training of simulation technicians. Quantitative methods were utilized to analyze data. Results Over 90% of technicians (n=65) think that a lab designed explicitly for the training of technicians is novel and beneficial. Approximately 75% of respondents think that the space provided appropriate audiovisual (AV) infrastructure and space to evaluate the ability of technicians to be independent. The respondents think that the lab needed more storage space, visualization space for a large number of students, and more space in the technical/repair area. Conclusions  A space designed for the training of simulation technicians was considered to be beneficial. This laboratory requires distinct space for technical repair, adequate bench space for the maintenance and repair of simulators, an appropriate AV infrastructure, and space to evaluate the ability of technicians to be independent. PMID:27096134

  9. Results of computer calculations for a simulated distribution of kidney cells

    NASA Technical Reports Server (NTRS)

    Micale, F. J.

    1985-01-01

    The results of computer calculations for a simulated distribution of kidney cells are given. The calculations were made for different values of electroosmotic flow, U sub o, and the ratio of sample diameter to channel diameter, R.

  10. Comparison of experimental results with numerical simulations for pulsed thermographic NDE

    NASA Astrophysics Data System (ADS)

    Sripragash, Letchuman; Sundaresan, Mannur

    2017-02-01

    This paper examines pulse thermographic nondestructive evaluation of flat bottom holes of isotropic materials. Different combinations of defect diameters and depths are considered. Thermographic Signal Reconstruction (TSR) method is used to analyze these results. In addition, a new normalization procedure is used to remove the dependence of thermographic results on the material properties and instrumentation settings during these experiments. Hence the normalized results depend only on the geometry of the specimen and the defects. These thermographic NDE procedures were also simulated using finite element technique for a variety of defect configurations. The data obtained from numerical simulations were also processed using the normalization scheme. Excellent agreement was seen between the results obtained from experiments and numerical simulations. Therefore, the scheme is extended to introduce a correlation technique by which numerical simulations are used to quantify the defect parameters.

  11. Updated electron-cloud simulation results for the Large Hadron Collider (LHC)

    SciTech Connect

    Furman, M. A.; Pivi, M.

    2001-06-26

    This paper presents new simulation results for the power deposition from the electron cloud in the beam screen of the Large Hadron Collider (LHC). We pay particular attention to the sensitivity of the results to certain low-energy parameters of the secondary electron (SE)emission. Most of these parameters, which constitute an input to the simulation program, are extracted from recent measurements at CERN and SLAC.

  12. NPE 2010 results - Independent performance assessment by simulated CTBT violation scenarios

    NASA Astrophysics Data System (ADS)

    Ross, O.; Bönnemann, C.; Ceranna, L.; Gestermann, N.; Hartmann, G.; Plenefisch, T.

    2012-04-01

    earthquakes by seismological analysis. The remaining event at Black Thunder Mine, Wyoming, on 23 Oct at 21:15 UTC showed clear explosion characteristics. It caused also Infrasound detections at one station in Canada. An infrasonic one station localization algorithm led to event localization results comparable in precision to the teleseismic localization. However, the analysis of regional seismological stations gave the most accurate result giving an error ellipse of about 60 square kilometer. Finally a forward ATM simulation was performed with the candidate event as source in order to reproduce the original detection scenario. The ATM results showed a simulated station fingerprint in the IMS very similar to the fictitious detections given in the NPE 2010 scenario which is an additional confirmation that the event was correctly identified. The shown event analysis of the NPE 2010 serves as successful example for Data Fusion between the technology of radionuclide detection supported by ATM and seismological methodology as well as infrasound signal processing.

  13. Computational manufacturing of optical interference coatings: method, simulation results, and comparison with experiment.

    PubMed

    Friedrich, Karen; Wilbrandt, Steffen; Stenzel, Olaf; Kaiser, Norbert; Hoffmann, Karl Heinz

    2010-06-01

    Virtual deposition runs have been performed to estimate the production yield of selected oxide optical interference coatings when plasma ion-assisted deposition with an advanced plasma source is applied. Thereby, deposition of each layer can be terminated either by broadband optical monitoring or quartz crystal monitoring. Numerous deposition runs of single-layer coatings have been performed to investigate the reproducibility of coating properties and to quantify deposition errors for the simulation. Variations of the following parameters are considered in the simulation: refractive index, extinction coefficient, and film thickness. The refractive index and the extinction coefficient are simulated in terms of the oscillator model. The parameters are varied using an apodized normal distribution with known mean value and standard deviation. Simulation of variations in the film thickness is performed specific to the selected monitoring strategy. Several deposition runs of the selected oxide interference coatings have been performed to verify the simulation results by experimental data.

  14. Should we adjust for a confounder if empirical and theoretical criteria yield contradictory results? A simulation study

    PubMed Central

    Lee, Paul H.

    2014-01-01

    Confounders can be identified by one of two main strategies: empirical or theoretical. Although confounder identification strategies that combine empirical and theoretical strategies have been proposed, the need for adjustment remains unclear if the empirical and theoretical criteria yield contradictory results due to random error. We simulated several scenarios to mimic either the presence or the absence of a confounding effect and tested the accuracy of the exposure-outcome association estimates with and without adjustment. Various criteria (significance criterion, Change-in-estimate(CIE) criterion with a 10% cutoff and with a simulated cutoff) were imposed, and a range of sample sizes were trialed. In the presence of a true confounding effect, unbiased estimates were obtained only by using the CIE criterion with a simulated cutoff. In the absence of a confounding effect, all criteria performed well regardless of adjustment. When the confounding factor was affected by both exposure and outcome, all criteria yielded accurate estimates without adjustment, but the adjusted estimates were biased. To conclude, theoretical confounders should be adjusted for regardless of the empirical evidence found. The adjustment for factors that do not have a confounding effect minimally effects. Potential confounders affected by both exposure and outcome should not be adjusted for. PMID:25124526

  15. Application of ARM Cloud Radar Simulator to GCMs: Plan, Issues, and Preliminary Results

    NASA Astrophysics Data System (ADS)

    Zhang, Y.; Xie, S.; Klein, S. A.; Marchand, R.; Lin, W.; Kollias, P.; Clothiaux, E. E.

    2015-12-01

    It has been challenging to directly compare ARM ground-based cloud radar measurements with climate model output because of limitations or features of the observing process. To address this issue, an ongoing effort in ARM is to implement ARM cloud radar simulator, similar to satellite simulators that have been widely used in the global climate modeling community, to convert model data into pseudo-ARM cloud radar observations. The simulator mimics the instrument view of a narrow atmospheric column (as compared to a large GCM grid-cell) thus allowing meaningful comparison between model output and ARM cloud observations. This work is being closely coordinated with the CFMIP (the Cloud-Feedback Model Intercomparison Project) Observation Simulator Package (COSP, www.cfmip.net; Bodas-Salcedo et al. 2011) project. The goal is to incorporate ARM simulators into COSP with the global climate modeling community as the target user. This poster provides details about the implementation plan, discusses potential issues with ground-based simulators for both ARM radars, and presents preliminary results in evaluating the DOE Accelerated Climate Model for Energy (ACME) simulated clouds with ARM radar observations through applying the ARM radar simulator to ACME. Future plans on this project are discussed. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  16. On the role of numerical simulations in studies of reduced gravity-induced physiological effects in humans. Results from NELME.

    NASA Astrophysics Data System (ADS)

    Perez-Poch, Antoni

    Computer simulations are becoming a promising research line of work, as physiological models become more and more sophisticated and reliable. Technological advances in state-of-the-art hardware technology and software allow nowadays for better and more accurate simulations of complex phenomena, such as the response of the human cardiovascular system to long-term exposure to microgravity. Experimental data for long-term missions are difficult to achieve and reproduce, therefore the predictions of computer simulations are of a major importance in this field. Our approach is based on a previous model developed and implemented in our laboratory (NELME: Numercial Evaluation of Long-term Microgravity Effects). The software simulates the behaviour of the cardiovascular system and different human organs, has a modular archi-tecture, and allows to introduce perturbations such as physical exercise or countermeasures. The implementation is based on a complex electrical-like model of this control system, using inexpensive development frameworks, and has been tested and validated with the available experimental data. The objective of this work is to analyse and simulate long-term effects and gender differences when individuals are exposed to long-term microgravity. Risk probability of a health impairement which may put in jeopardy a long-term mission is also evaluated. . Gender differences have been implemented for this specific work, as an adjustment of a number of parameters that are included in the model. Women versus men physiological differences have been therefore taken into account, based upon estimations from the physiology bibliography. A number of simulations have been carried out for long-term exposure to microgravity. Gravity varying continuosly from Earth-based to zero, and time exposure are the two main variables involved in the construction of results, including responses to patterns of physical aerobic ex-ercise and thermal stress simulating an extra

  17. Blood-Borne Markers of Fatigue in Competitive Athletes – Results from Simulated Training Camps

    PubMed Central

    Hecksteden, Anne; Skorski, Sabrina; Schwindling, Sascha; Hammes, Daniel; Pfeiffer, Mark; Kellmann, Michael; Ferrauti, Alexander; Meyer, Tim

    2016-01-01

    Assessing current fatigue of athletes to fine-tune training prescriptions is a critical task in competitive sports. Blood-borne surrogate markers are widely used despite the scarcity of validation trials with representative subjects and interventions. Moreover, differences between training modes and disciplines (e.g. due to differences in eccentric force production or calorie turnover) have rarely been studied within a consistent design. Therefore, we investigated blood-borne fatigue markers during and after discipline-specific simulated training camps. A comprehensive panel of blood-born indicators was measured in 73 competitive athletes (28 cyclists, 22 team sports, 23 strength) at 3 time-points: after a run-in resting phase (d 1), after a 6-day induction of fatigue (d 8) and following a subsequent 2-day recovery period (d 11). Venous blood samples were collected between 8 and 10 a.m. Courses of blood-borne indicators are considered as fatigue dependent if a significant deviation from baseline is present at day 8 (Δfatigue) which significantly regresses towards baseline until day 11 (Δrecovery). With cycling, a fatigue dependent course was observed for creatine kinase (CK; Δfatigue 54±84 U/l; Δrecovery -60±83 U/l), urea (Δfatigue 11±9 mg/dl; Δrecovery -10±10 mg/dl), free testosterone (Δfatigue -1.3±2.1 pg/ml; Δrecovery 0.8±1.5 pg/ml) and insulin linke growth factor 1 (IGF-1; Δfatigue -56±28 ng/ml; Δrecovery 53±29 ng/ml). For urea and IGF-1 95% confidence intervals for days 1 and 11 did not overlap with day 8. With strength and high-intensity interval training, respectively, fatigue-dependent courses and separated 95% confidence intervals were present for CK (strength: Δfatigue 582±649 U/l; Δrecovery -618±419 U/l; HIIT: Δfatigue 863±952 U/l; Δrecovery -741±842 U/l) only. These results indicate that, within a comprehensive panel of blood-borne markers, changes in fatigue are most accurately reflected by urea and IGF-1 for cycling and by CK

  18. Experimental results and simulations from aperture synthesis three-dimensional radiometric imaging

    NASA Astrophysics Data System (ADS)

    Salmon, Neil A.

    2016-10-01

    This paper presents the theory and algorithm of how a three-dimensional (3D) image can be generated using crosscorrelations of radiometric emission from a source measured using antennas in the near field. An example of how the algorithm is used to create 3D images of emission measured from a noise source is presented, indicating the presence of Fresnel noise and aliasing in the experimental data when the source is moved away from the phase centre. Simulations are presented which reproduce the Fresnel noise as generated by a 3x3x3 array of point sources located at the centre of a 2 metre diameter array of antennas representing a security screening portal. Two methods of reducing the Fresnel noise are presented: 1) a software method which makes successive more accurate estimates of the locations and intensities of sources; 2) a hardware method which reduces the coherence length of the radiation by increasing the radiation bandwidth.

  19. Wave spectra of a shoaling wave field: A comparison of experimental and simulated results

    NASA Technical Reports Server (NTRS)

    Morris, W. D.; Grosch, C. E.; Poole, L. R.

    1982-01-01

    Wave profile measurements made from an aircraft crossing the North Carolina continental shelf after passage of Tropical Storm Amy in 1975 are used to compute a series of wave energy spectra for comparison with simulated spectra. Results indicate that the observed wave field experiences refraction and shoaling effects causing statistically significant changes in the spectral density levels. A modeling technique is used to simulate the spectral density levels. Total energy levels of the simulated spectra are within 20 percent of those of the observed wave field. The results represent a successful attempt to theoretically simulate, at oceanic scales, the decay of a wave field which contains significant wave energies from deepwater through shoaling conditions.

  20. Flow and transport in highly heterogeneous formations: 3. Numerical simulations and comparison with theoretical results

    NASA Astrophysics Data System (ADS)

    Janković, I.; Fiori, A.; Dagan, G.

    2003-09-01

    In parts 1 [, 2003] and 2 [, 2003] a multi-indicator model of heterogeneous formations is devised in order to solve flow and transport in highly heterogeneous formations. The isotropic medium is made up from circular (2-D) or spherical (3-D) inclusions of different conductivities K, submerged in a matrix of effective conductivity. This structure is different from the multi-Gaussian one, even for equal log conductivity distribution and integral scale. A snapshot of a two-dimensional plume in a highly heterogeneous medium of lognormal conductivity distribution shows that the model leads to a complex transport picture. The present study was limited, however, to investigating the statistical moments of ergodic plumes. Two approximate semianalytical solutions, based on a self-consistent model (SC) and on a first-order perturbation in the log conductivity variance (FO), are used in parts 1 and 2 in order to compute the statistical moments of flow and transport variables for a lognormal conductivity pdf. In this paper an efficient and accurate numerical procedure, based on the analytic-element method [, 1989], is used in order to validate the approximate results. The solution satisfies exactly the continuity equation and at high-accuracy the continuity of heads at inclusion boundaries. The dimensionless dependent variables depend on two parameters: the volume fraction n of inclusions in the medium and the log conductivity variance σY2. For inclusions of uniform radius, the largest n was 0.9 (2-D) and 0.7 (3-D), whereas the largest σY2 was equal to 10. The SC approximation underestimates the longitudinal Eulerian velocity variance for increasing n and increasing σY2 in 2-D and, to a lesser extent, in 3-D, as compared to numerical results. The FO approximation overestimates these variances, and these effects are larger in the transverse direction. The longitudinal velocity pdf is highly skewed and negative velocities are present at high σY2, especially in 2-D. The main

  1. Results from a limited area mesoscale numerical simulation for 10 April 1979

    NASA Technical Reports Server (NTRS)

    Kalb, M. W.

    1985-01-01

    Results are presented from a nine-hour limited area fine mesh (35-km) mesoscale model simulation initialized with SESAME-AVE I radiosonde data for Apr. 10, 1979 at 2100 GMT. Emphasis is on the diagnosis of mesoscale structure in the mass and precipitation fields. Along the Texas/Oklahoma border, independent of the short wave, convective precipitation formed several hours into the simulation and was organized into a narrow band suggestive of the observed April 10 squall line.

  2. Columbus meteoroid/debris protection study - Experimental simulation techniques and results

    NASA Astrophysics Data System (ADS)

    Schneider, E.; Kitta, K.; Stilp, A.; Lambert, M.; Reimerdes, H. G.

    1992-08-01

    The methods and measurement techniques used in experimental simulations of micrometeoroid and space debris impacts with the ESA's laboratory module Columbus are described. Experiments were carried out at the two-stage light gas gun acceleration facilities of the Ernst-Mach Institute. Results are presented on simulations of normal impacts on bumper systems, oblique impacts on dual bumper systems, impacts into cooled targets, impacts into pressurized targets, and planar impacts of low-density projectiles.

  3. The allele distribution in next-generation sequencing data sets is accurately described as the result of a stochastic branching process.

    PubMed

    Heinrich, Verena; Stange, Jens; Dickhaus, Thorsten; Imkeller, Peter; Krüger, Ulrike; Bauer, Sebastian; Mundlos, Stefan; Robinson, Peter N; Hecht, Jochen; Krawitz, Peter M

    2012-03-01

    With the availability of next-generation sequencing (NGS) technology, it is expected that sequence variants may be called on a genomic scale. Here, we demonstrate that a deeper understanding of the distribution of the variant call frequencies at heterozygous loci in NGS data sets is a prerequisite for sensitive variant detection. We model the crucial steps in an NGS protocol as a stochastic branching process and derive a mathematical framework for the expected distribution of alleles at heterozygous loci before measurement that is sequencing. We confirm our theoretical results by analyzing technical replicates of human exome data and demonstrate that the variance of allele frequencies at heterozygous loci is higher than expected by a simple binomial distribution. Due to this high variance, mutation callers relying on binomial distributed priors are less sensitive for heterozygous variants that deviate strongly from the expected mean frequency. Our results also indicate that error rates can be reduced to a greater degree by technical replicates than by increasing sequencing depth.

  4. ICGA-PSO-ELM approach for accurate multiclass cancer classification resulting in reduced gene sets in which genes encoding secreted proteins are highly represented.

    PubMed

    Saraswathi, Saras; Sundaram, Suresh; Sundararajan, Narasimhan; Zimmermann, Michael; Nilsen-Hamilton, Marit

    2011-01-01

    A combination of Integer-Coded Genetic Algorithm (ICGA) and Particle Swarm Optimization (PSO), coupled with the neural-network-based Extreme Learning Machine (ELM), is used for gene selection and cancer classification. ICGA is used with PSO-ELM to select an optimal set of genes, which is then used to build a classifier to develop an algorithm (ICGA_PSO_ELM) that can handle sparse data and sample imbalance. We evaluate the performance of ICGA-PSO-ELM and compare our results with existing methods in the literature. An investigation into the functions of the selected genes, using a systems biology approach, revealed that many of the identified genes are involved in cell signaling and proliferation. An analysis of these gene sets shows a larger representation of genes that encode secreted proteins than found in randomly selected gene sets. Secreted proteins constitute a major means by which cells interact with their surroundings. Mounting biological evidence has identified the tumor microenvironment as a critical factor that determines tumor survival and growth. Thus, the genes identified by this study that encode secreted proteins might provide important insights to the nature of the critical biological features in the microenvironment of each tumor type that allow these cells to thrive and proliferate.

  5. Handling Qualities Results of an Initial Geared Flap Tilt Wing Piloted Simulation

    NASA Technical Reports Server (NTRS)

    Guerrero, Lourdes M.; Corliss, Lloyd D.

    1991-01-01

    An exploratory simulation study of a novel approach to pitch control for a tilt wing aircraft was conducted in 1990 on the NASA-Ames Vertical Motion Simulator. The purpose of the study was to evaluate and compare the handling qualities of both a conventional and a geared flap tilt wing control configuration. The geared flap is an innovative control concept which has the potential for reducing or eliminating the horizontal pitch control tail rotor or reaction jets required by prior tilt wing designs. The handling qualities results of the geared flap control configuration are presented in this paper and compared to the conventional (programmed flap) tilt wing control configuration. This paper also describes the geared flap concept, the tilt wing aircraft, the simulation model, the simulation facility and experiment setup, and the pilot evaluation tasks and procedures.

  6. Ship's behaviour during hurricane Sandy near the USA coasts. Simulation results

    NASA Astrophysics Data System (ADS)

    Chiotoroiu, B.; Grosan, N.; Soare, L.

    2015-11-01

    The aim of this study is to analyze the impact of the stormy weather during hurricane Sandy on an oil tank using the navigation simulator. Meteorological and waves maps from forecast models are used, together with relevant information from the meteorological warnings. The simulation sessions were performed on the navigation simulator from the Constanta Maritime University and allowed us the selection of specific parameters for the ship and the environment in order to observe the ship's behavior in heavy sea conditions. Simulation results are important due to the unexpected environmental conditions and the ship position: very close to the hurricane centre when the storm began to change its track and to transform into an extra tropical cyclone.

  7. Geant4 simulation of the Elekta XVI kV CBCT unit for accurate description of potential late toxicity effects of image-guided radiotherapy.

    PubMed

    Brochu, F M; Burnet, N G; Jena, R; Plaistow, R; Parker, M A; Thomas, S J

    2014-12-21

    This paper describes the modelisation of the Elekta XVI Cone Beam Computed Tomography (CBCT) machine components with Geant4 and its validation against calibration data taken for two commonly used machine setups. Preliminary dose maps of simulated CBCTs coming from this modelisation work are presented. This study is the first step of a research project, GHOST, aiming to improve the understanding of late toxicity risk in external beam radiotherapy patients by simulating dose depositions integrated from different sources (imaging, treatment beam) over the entire treatment plan. The second cancer risk will then be derived from different models relating irradiation dose and second cancer risk.

  8. Geant4 simulation of the Elekta XVI kV CBCT unit for accurate description of potential late toxicity effects of image-guided radiotherapy

    NASA Astrophysics Data System (ADS)

    Brochu, F. M.; Burnet, N. G.; Jena, R.; Plaistow, R.; Parker, M. A.; Thomas, S. J.

    2014-12-01

    This paper describes the modelisation of the Elekta XVI Cone Beam Computed Tomography (CBCT) machine components with Geant4 and its validation against calibration data taken for two commonly used machine setups. Preliminary dose maps of simulated CBCTs coming from this modelisation work are presented. This study is the first step of a research project, GHOST, aiming to improve the understanding of late toxicity risk in external beam radiotherapy patients by simulating dose depositions integrated from different sources (imaging, treatment beam) over the entire treatment plan. The second cancer risk will then be derived from different models relating irradiation dose and second cancer risk.

  9. Crystal growth of pure substances: Phase-field simulations in comparison with analytical and experimental results

    NASA Astrophysics Data System (ADS)

    Nestler, B.; Danilov, D.; Galenko, P.

    2005-07-01

    A phase-field model for non-isothermal solidification in multicomponent systems [SIAM J. Appl. Math. 64 (3) (2004) 775-799] consistent with the formalism of classic irreversible thermodynamics is used for numerical simulations of crystal growth in a pure material. The relation of this approach to the phase-field model by Bragard et al. [Interface Science 10 (2-3) (2002) 121-136] is discussed. 2D and 3D simulations of dendritic structures are compared with the analytical predictions of the Brener theory [Journal of Crystal Growth 99 (1990) 165-170] and with recent experimental measurements of solidification in pure nickel [Proceedings of the TMS Annual Meeting, March 14-18, 2004, pp. 277-288; European Physical Journal B, submitted for publication]. 3D morphology transitions are obtained for variations in surface energy and kinetic anisotropies at different undercoolings. In computations, we investigate the convergence behaviour of a standard phase-field model and of its thin interface extension at different undercoolings and at different ratios between the diffuse interface thickness and the atomistic capillary length. The influence of the grid anisotropy is accurately analyzed for a finite difference method and for an adaptive finite element method in comparison.

  10. Comparing Simulation Results with Traditional PRA Model on a Boiling Water Reactor Station Blackout Case Study

    SciTech Connect

    Zhegang Ma; Diego Mandelli; Curtis Smith

    2011-07-01

    A previous study used RELAP and RAVEN to conduct a boiling water reactor station black-out (SBO) case study in a simulation based environment to show the capabilities of the risk-informed safety margin characterization methodology. This report compares the RELAP/RAVEN simulation results with traditional PRA model results. The RELAP/RAVEN simulation run results were reviewed for their input parameters and output results. The input parameters for each simulation run include various timing information such as diesel generator or offsite power recovery time, Safety Relief Valve stuck open time, High Pressure Core Injection or Reactor Core Isolation Cooling fail to run time, extended core cooling operation time, depressurization delay time, and firewater injection time. The output results include the maximum fuel clad temperature, the outcome, and the simulation end time. A traditional SBO PRA model in this report contains four event trees that are linked together with the transferring feature in SAPHIRE software. Unlike the usual Level 1 PRA quantification process in which only core damage sequences are quantified, this report quantifies all SBO sequences, whether they are core damage sequences or success (i.e., non core damage) sequences, in order to provide a full comparison with the simulation results. Three different approaches were used to solve event tree top events and quantify the SBO sequences: “W” process flag, default process flag without proper adjustment, and default process flag with adjustment to account for the success branch probabilities. Without post-processing, the first two approaches yield incorrect results with a total conditional probability greater than 1.0. The last approach accounts for the success branch probabilities and provides correct conditional sequence probabilities that are to be used for comparison. To better compare the results from the PRA model and the simulation runs, a simplified SBO event tree was developed with only four

  11. High Fidelity Thermal Simulators for Non-Nuclear Testing: Analysis and Initial Results

    NASA Technical Reports Server (NTRS)

    Bragg-Sitton, Shannon M.; Dickens, Ricky; Dixon, David

    2007-01-01

    Non-nuclear testing can be a valuable tool in the development of a space nuclear power system, providing system characterization data and allowing one to work through various fabrication, assembly and integration issues without the cost and time associated with a full ground nuclear test. In a non-nuclear test bed, electric heaters are used to simulate the heat from nuclear fuel. Testing with non-optimized heater elements allows one to assess thermal, heat transfer, and stress related attributes of a given system, but fails to demonstrate the dynamic response that would be present in an integrated, fueled reactor system. High fidelity thermal simulators that match both the static and the dynamic fuel pin performance that would be observed in an operating, fueled nuclear reactor can vastly increase the value of non-nuclear test results. With optimized simulators, the integration of thermal hydraulic hardware tests with simulated neutronie response provides a bridge between electrically heated testing and fueled nuclear testing, providing a better assessment of system integration issues, characterization of integrated system response times and response characteristics, and assessment of potential design improvements' at a relatively small fiscal investment. Initial conceptual thermal simulator designs are determined by simple one-dimensional analysis at a single axial location and at steady state conditions; feasible concepts are then input into a detailed three-dimensional model for comparison to expected fuel pin performance. Static and dynamic fuel pin performance for a proposed reactor design is determined using SINDA/FLUINT thermal analysis software, and comparison is made between the expected nuclear performance and the performance of conceptual thermal simulator designs. Through a series of iterative analyses, a conceptual high fidelity design can developed. Test results presented in this paper correspond to a "first cut" simulator design for a potential

  12. Obtaining identical results on varying numbers of processors in domain decomposed particle Monte Carlo simulations.

    SciTech Connect

    Brunner, Thomas A.; Kalos, Malvin H.; Gentile, Nicholas A.

    2005-03-01

    Domain decomposed Monte Carlo codes, like other domain-decomposed codes, are difficult to debug. Domain decomposition is prone to error, and interactions between the domain decomposition code and the rest of the algorithm often produces subtle bugs. These bugs are particularly difficult to find in a Monte Carlo algorithm, in which the results have statistical noise. Variations in the results due to statistical noise can mask errors when comparing the results to other simulations or analytic results.

  13. Geometry and Simulation Results for a Gas Turbine Representative of the Energy Efficient Engine (EEE)

    NASA Technical Reports Server (NTRS)

    Claus, Russell W.; Beach, Tim; Turner, Mark; Siddappaji, Kiran; Hendricks, Eric S.

    2015-01-01

    This paper describes the geometry and simulation results of a gas-turbine engine based on the original EEE engine developed in the 1980s. While the EEE engine was never in production, the technology developed during the program underpins many of the current generation of gas turbine engines. This geometry is being explored as a potential multi-stage turbomachinery test case that may be used to develop technology for virtual full-engine simulation. Simulation results were used to test the validity of each component geometry representation. Results are compared to a zero-dimensional engine model developed from experimental data. The geometry is captured in a series of Initial Graphical Exchange Specification (IGES) files and is available on a supplemental DVD to this report.

  14. Results of a 3-D full particle simulation of quasi-perpendicular shock

    NASA Astrophysics Data System (ADS)

    Shinohara, I.; Fujimoto, M.

    2010-12-01

    Recent progress of computational power enables us to perform really macro-scale three-dimensional situations with full particle codes. In this presentation, we will report results of a three-dimensional simulation of a quasi-perpendicular shock. The simulation parameters were selected to simulate a Cluster-II observational result reported by Seki et al. (2009), M_A=7.4 and beta=0.16. The realistic mass ratio mi/me=1840 was taken, and almost one ion inertia length square could be allocated to the plane perpendicular to the upstream flow axis. The result shows that both the self-reformation process and whistler emission are observed. However, the 3-D result is not a simple superposition of 2-D results. The most impressive feature is that quite complicated wave activity is found in the shock foot region. With the help of this wave activity, electron heating observed in the 3-D run is more efficient than those in the 1-D and 2-D runs with the same shock parameters. Moreover, non-thermal electrons are also produced only in the 3D run. In this paper, comparing the 3-D result with previous 1-D and 2-D simulation results, three dimensional nature of the shock transition region of quasi-perpendicular shock is discussed.

  15. Simulation and Analysis of Microwave Transmission through an Electron Cloud, a Comparison of Results

    SciTech Connect

    Sonnad, Kiran; Sonnad, Kiran; Furman, Miguel; Veitzer, Seth; Stoltz, Peter; Cary, John

    2007-03-12

    Simulation studies for transmission of microwaves through electron cloudes show good agreement with analytic results. The elctron cloud produces a shift in phase of the microwave. Experimental observation of this phenomena would lead to a useful diagnostic tool for acessing the local density of electron clouds in an accelerator. These experiments are being carried out at the CERN SPS and the PEP-II LER at SLAC and is proposed to be done at the Fermilab maininjector. In this study, a brief analysis of the phase shift is provided and the results are compared with that obtained from simulations.

  16. SIMULATION AND ANALYSIS OF MICROWAVE TRANSMISSION THROUGH ANELECTRON CLOUD, A COMPARISON OF RESULTS

    SciTech Connect

    Sonnad, Kiran G.; Furman, Miguel; Veitzer, Seth A.; Cary, John

    2006-04-15

    Simulation studies for transmission of microwaves through electron clouds show good agreement with analytic results. The electron cloud produces a shift in phase of the microwave. Experimental observation of this phenomena would lead to a useful diagnostic tool for accessing the local density of electron clouds in an accelerator. These experiments are being carried out at the CERN SPS and the PEP-II LER at SLAC and is proposed to be done at the Fermilab main injector. In this study, a brief analysis of the phase shift is provided and the results are compared with that obtained from simulations.

  17. Battery Performance of ADEOS (Advanced Earth Observing Satellite) and Ground Simulation Test Results

    NASA Technical Reports Server (NTRS)

    Koga, K.; Suzuki, Y.; Kuwajima, S.; Kusawake, H.

    1997-01-01

    The Advanced Earth Observing Satellite (ADEOS) is developed with the aim of establishment of platform technology for future spacecraft and inter-orbit communication technology for the transmission of earth observation data. ADEOS uses 5 batteries, consists of two packs. This paper describes, using graphs and tables, the ground simulation tests and results that are carried to determine the performance of the ADEOS batteries.

  18. Analysis Results for Lunar Soil Simulant Using a Portable X-Ray Fluorescence Analyzer

    NASA Technical Reports Server (NTRS)

    Boothe, R. E.

    2006-01-01

    Lunar soil will potentially be used for oxygen generation, water generation, and as filler for building blocks during habitation missions on the Moon. NASA s in situ fabrication and repair program is evaluating portable technologies that can assess the chemistry of lunar soil and lunar soil simulants. This Technical Memorandum summarizes the results of the JSC 1 lunar soil simulant analysis using the TRACeR III IV handheld x-ray fluorescence analyzer, manufactured by KeyMaster Technologies, Inc. The focus of the evaluation was to determine how well the current instrument configuration would detect and quantify the components of JSC-1.

  19. Reconfigurable computing for Monte Carlo simulations: Results and prospects of the Janus project

    NASA Astrophysics Data System (ADS)

    Baity-Jesi, M.; Baños, R. A.; Cruz, A.; Fernandez, L. A.; Gil-Narvion, J. M.; Gordillo-Guerrero, A.; Guidetti, M.; Iñiguez, D.; Maiorano, A.; Mantovani, F.; Marinari, E.; Martin-Mayor, V.; Monforte-Garcia, J.; Muñoz Sudupe, A.; Navarro, D.; Parisi, G.; Pivanti, M.; Perez-Gaviro, S.; Ricci-Tersenghi, F.; Ruiz-Lorenzo, J. J.; Schifano, S. F.; Seoane, B.; Tarancon, A.; Tellez, P.; Tripiccione, R.; Yllanes, D.

    2012-08-01

    We describe Janus, a massively parallel FPGA-based computer optimized for the simulation of spin glasses, theoretical models for the behavior of glassy materials. FPGAs (as compared to GPUs or many-core processors) provide a complementary approach to massively parallel computing. In particular, our model problem is formulated in terms of binary variables, and floating-point operations can be (almost) completely avoided. The FPGA architecture allows us to run many independent threads with almost no latencies in memory access, thus updating up to 1024 spins per cycle. We describe Janus in detail and we summarize the physics results obtained in four years of operation of this machine; we discuss two types of physics applications: long simulations on very large systems (which try to mimic and provide understanding about the experimental non-equilibrium dynamics), and low-temperature equilibrium simulations using an artificial parallel tempering dynamics. The time scale of our non-equilibrium simulations spans eleven orders of magnitude (from picoseconds to a tenth of a second). On the other hand, our equilibrium simulations are unprecedented both because of the low temperatures reached and for the large systems that we have brought to equilibrium. A finite-time scaling ansatz emerges from the detailed comparison of the two sets of simulations. Janus has made it possible to perform spin-glass simulations that would take several decades on more conventional architectures. The paper ends with an assessment of the potential of possible future versions of the Janus architecture, based on state-of-the-art technology.

  20. Accurate quantum chemical calculations

    NASA Technical Reports Server (NTRS)

    Bauschlicher, Charles W., Jr.; Langhoff, Stephen R.; Taylor, Peter R.

    1989-01-01

    An important goal of quantum chemical calculations is to provide an understanding of chemical bonding and molecular electronic structure. A second goal, the prediction of energy differences to chemical accuracy, has been much harder to attain. First, the computational resources required to achieve such accuracy are very large, and second, it is not straightforward to demonstrate that an apparently accurate result, in terms of agreement with experiment, does not result from a cancellation of errors. Recent advances in electronic structure methodology, coupled with the power of vector supercomputers, have made it possible to solve a number of electronic structure problems exactly using the full configuration interaction (FCI) method within a subspace of the complete Hilbert space. These exact results can be used to benchmark approximate techniques that are applicable to a wider range of chemical and physical problems. The methodology of many-electron quantum chemistry is reviewed. Methods are considered in detail for performing FCI calculations. The application of FCI methods to several three-electron problems in molecular physics are discussed. A number of benchmark applications of FCI wave functions are described. Atomic basis sets and the development of improved methods for handling very large basis sets are discussed: these are then applied to a number of chemical and spectroscopic problems; to transition metals; and to problems involving potential energy surfaces. Although the experiences described give considerable grounds for optimism about the general ability to perform accurate calculations, there are several problems that have proved less tractable, at least with current computer resources, and these and possible solutions are discussed.

  1. Convergence and shear statistics in galaxy clusters as a result of Monte Carlo simulations

    NASA Astrophysics Data System (ADS)

    Poplavsky, Alexander

    2016-03-01

    In this paper the influence of galaxy cluster halo environment on the deflection properties of its galaxies is investigated. For this purpose circular and elliptical projected cluster haloes obeying Einasto density profiles are modelled in the \\varLambdaCDM cosmological model. By Monte-Carlo simulations external shear and convergence are calculated for random positions of a test galaxy within its cluster. Throughout the simulations the total virial mass, profile concentration and slope parameters are varied both for cluster and its galaxies. The cluster is composed of smooth matter distribution (intergalactic gas and dark matter) and randomly placed galaxies. As a result of multiple simulation runs robust statistical estimations of external shear and convergence are derived for variable cluster characteristics and its redshift. In addition, the models for external shear and convergence are applied for the galaxy lens seen through the cluster IRC-0218.

  2. Monte Carlo simulations of microchannel plate detectors I: steady-state voltage bias results

    SciTech Connect

    Ming Wu, Craig Kruschwitz, Dane Morgan, Jiaming Morgan

    2008-07-01

    X-ray detectors based on straight-channel microchannel plates (MCPs) are a powerful diagnostic tool for two-dimensional, time-resolved imaging and timeresolved x-ray spectroscopy in the fields of laser-driven inertial confinement fusion and fast z-pinch experiments. Understanding the behavior of microchannel plates as used in such detectors is critical to understanding the data obtained. The subject of this paper is a Monte Carlo computer code we have developed to simulate the electron cascade in a microchannel plate under a static applied voltage. Also included in the simulation is elastic reflection of low-energy electrons from the channel wall, which is important at lower voltages. When model results were compared to measured microchannel plate sensitivities, good agreement was found. Spatial resolution simulations of MCP-based detectors were also presented and found to agree with experimental measurements.

  3. Monte Carlo simulations of microchannel plate detectors. I. Steady-state voltage bias results

    SciTech Connect

    Wu Ming; Kruschwitz, Craig A.; Morgan, Dane V.; Morgan, Jiaming

    2008-07-15

    X-ray detectors based on straight-channel microchannel plates (MCPs) are a powerful diagnostic tool for two-dimensional, time-resolved imaging and time-resolved x-ray spectroscopy in the fields of laser-driven inertial confinement fusion and fast Z-pinch experiments. Understanding the behavior of microchannel plates as used in such detectors is critical to understanding the data obtained. The subject of this paper is a Monte Carlo computer code we have developed to simulate the electron cascade in a MCP under a static applied voltage. Also included in the simulation is elastic reflection of low-energy electrons from the channel wall, which is important at lower voltages. When model results were compared to measured MCP sensitivities, good agreement was found. Spatial resolution simulations of MCP-based detectors were also presented and found to agree with experimental measurements.

  4. Computer simulation of shelf and stream profile geomorphic evolution resulting from eustasy and uplift

    SciTech Connect

    Johnson, R.M. )

    1993-04-01

    A two-dimensional computer simulation of shelf and stream profile evolution with sea level oscillation has been developed to illustrate the interplay of coastal and fluvial processes on uplifting continental margins. The shelf evolution portion of the simulation is based on the erosional model of Trenhaile (1989). The rate of high tide cliff erosion decreases as abrasion platform gradient decreases the sea cliff height increases. The rate of subtidal erosion decreases as the subtidal sea floor gradient decreases. Values are specified for annual wave energy, energy required to erode a cliff notch 1 meter deep, nominal low tidal erosion rate, and rate of removal of cliff debris. The values were chosen arbitrarily to yield a geomorphic evolution consistent with the present coast of northern California, where flights of uplifted marine terraces are common. The stream profile evolution simulation interfaces in real time with the shelf simulation. The stream profile consists of uniformly spaced cells, each representing the median height of a profile segment. The stream simulation results show that stream response to sea level change on an uplifting coast is dependent on the profile gradient near the stream mouth, relative to the shelf gradient. Small streams with steep gradients aggrade onto the emergent shelf during sea level fall and incise at the mountain front during sea level rise. Large streams with low gradients incise the emergent shelf during sea level fall and aggrade in their valleys during sea level rise.

  5. Ejector nozzle test results at simulated flight conditions for an advanced supersonic transport propulsion system

    NASA Technical Reports Server (NTRS)

    Nelson, D. P.; Bresnahan, D. L.

    1983-01-01

    Results are presented of wind tunnel tests conducted to verify the performance improvements of a refined ejector nozzle design for advanced supersonic transport propulsion systems. The analysis of results obtained at simulated engine operating conditions is emphasized. Tests were conducted with models of approximately 1/10th scale which were configured to simulate nozzle operation at takeoff, subsonic cruise, transonic cruise, and supersonic cruise. Transonic cruise operation was not a consideration during the nozzle design phase, although an evaluation at this condition was later conducted. Test results, characterized by thrust and flow coefficients, are given for a range of nozzle pressure ratios, emphasizing the thrust performance at the engine operating conditions predicted for each flight Mach number. The results indicate that nozzle performance goals were met or closely approximated at takeoff and supersonic cruise, while subsonic cruise performance was within 2.3 percent of the goal with further improvement possible.

  6. Accurate Evaluation of Quantum Integrals

    NASA Technical Reports Server (NTRS)

    Galant, D. C.; Goorvitch, D.; Witteborn, Fred C. (Technical Monitor)

    1995-01-01

    Combining an appropriate finite difference method with Richardson's extrapolation results in a simple, highly accurate numerical method for solving a Schrodinger's equation. Important results are that error estimates are provided, and that one can extrapolate expectation values rather than the wavefunctions to obtain highly accurate expectation values. We discuss the eigenvalues, the error growth in repeated Richardson's extrapolation, and show that the expectation values calculated on a crude mesh can be extrapolated to obtain expectation values of high accuracy.

  7. Approaching system equilibrium with accurate or not accurate feedback information in a two-route system

    NASA Astrophysics Data System (ADS)

    Zhao, Xiao-mei; Xie, Dong-fan; Li, Qi

    2015-02-01

    With the development of intelligent transport system, advanced information feedback strategies have been developed to reduce traffic congestion and enhance the capacity. However, previous strategies provide accurate information to travelers and our simulation results show that accurate information brings negative effects, especially in delay case. Because travelers prefer to the best condition route with accurate information, and delayed information cannot reflect current traffic condition but past. Then travelers make wrong routing decisions, causing the decrease of the capacity and the increase of oscillations and the system deviating from the equilibrium. To avoid the negative effect, bounded rationality is taken into account by introducing a boundedly rational threshold BR. When difference between two routes is less than the BR, routes have equal probability to be chosen. The bounded rationality is helpful to improve the efficiency in terms of capacity, oscillation and the gap deviating from the system equilibrium.

  8. Improving the trust in results of numerical simulations and scientific data analytics

    SciTech Connect

    Cappello, Franck; Constantinescu, Emil; Hovland, Paul; Peterka, Tom; Phillips, Carolyn; Snir, Marc; Wild, Stefan

    2015-04-30

    This white paper investigates several key aspects of the trust that a user can give to the results of numerical simulations and scientific data analytics. In this document, the notion of trust is related to the integrity of numerical simulations and data analytics applications. This white paper complements the DOE ASCR report on Cybersecurity for Scientific Computing Integrity by (1) exploring the sources of trust loss; (2) reviewing the definitions of trust in several areas; (3) providing numerous cases of result alteration, some of them leading to catastrophic failures; (4) examining the current notion of trust in numerical simulation and scientific data analytics; (5) providing a gap analysis; and (6) suggesting two important research directions and their respective research topics. To simplify the presentation without loss of generality, we consider that trust in results can be lost (or the results’ integrity impaired) because of any form of corruption happening during the execution of the numerical simulation or the data analytics application. In general, the sources of such corruption are threefold: errors, bugs, and attacks. Current applications are already using techniques to deal with different types of corruption. However, not all potential corruptions are covered by these techniques. We firmly believe that the current level of trust that a user has in the results is at least partially founded on ignorance of this issue or the hope that no undetected corruptions will occur during the execution. This white paper explores the notion of trust and suggests recommendations for developing a more scientifically grounded notion of trust in numerical simulation and scientific data analytics. We first formulate the problem and show that it goes beyond previous questions regarding the quality of results such as V&V, uncertainly quantification, and data assimilation. We then explore the complexity of this difficult problem, and we sketch complementary general

  9. Results of an A109 simulation validation and handling qualities study

    NASA Technical Reports Server (NTRS)

    Eshow, Michelle M.; Orlandi, Diego; Bonaita, Giovanni; Barbieri, Sergio

    1989-01-01

    The results for the validation of a mathematical model of the Agusta A109 helicopter, and subsequent use of the model as the baseline for a handling qualities study of cockpit centerstick requirements, are described. The technical approach included flight test, non-realtime analysis, and realtime piloted simulation. Results of the validation illustrate a time- and frequency-domain approach to the model and simulator issues. The final A109 model correlates well with the actual aircraft with the Stability Augmentation System (SAS) engaged, but is unacceptable without the SAS because of instability and response coupling at low speeds. Results of the centerstick study support the current U.S. Army handling qualities requirements for centerstick characteristics.

  10. Simulation Results for the New NSTX HHFW Antenna Straps Design by Using Microwave Studio

    SciTech Connect

    Kung, C C; Brunkhorst, C; Greenough, N; Fredd, E; Castano, A; Miller, D; D'Amico, G; Yager, R; Hosea, J; Wilson, J R; Ryan, P

    2009-05-26

    Experimental results have shown that the high harmonic fast wave (HHFW) at 30 MHz can provide substantial plasma heating and current drive for the NSTX spherical tokamak operation. However, the present antenna strap design rarely achieves the design goal of delivering the full transmitter capability of 6 MW to the plasma. In order to deliver more power to the plasma, a new antenna strap design and the associated coaxial line feeds are being constructed. This new antenna strap design features two feedthroughs to replace the old single feed-through design. In the design process, CST Microwave Studio has been used to simulate the entire new antenna strap structure including the enclosure and the Faraday shield. In this paper, the antenna strap model and the simulation results will be discussed in detail. The test results from the new antenna straps with their associated resonant loops will be presented as well.

  11. Results from tight and loose coupled multiphysics in nuclear fuels performance simulations using BISON

    SciTech Connect

    Novascone, S. R.; Spencer, B. W.; Andrs, D.; Williamson, R. L.; Hales, J. D.; Perez, D. M.

    2013-07-01

    The behavior of nuclear fuel in the reactor environment is affected by multiple physics, most notably heat conduction and solid mechanics, which can have a strong influence on each other. To provide credible solutions, a fuel performance simulation code must have the ability to obtain solutions for each of the physics, including coupling between them. Solution strategies for solving systems of coupled equations can be categorized as loosely-coupled, where the individual physics are solved separately, keeping the solutions for the other physics fixed at each iteration, or tightly coupled, where the nonlinear solver simultaneously drives down the residual for each physics, taking into account the coupling between the physics in each nonlinear iteration. In this paper, we compare the performance of loosely and tightly coupled solution algorithms for thermomechanical problems involving coupled thermal and mechanical contact, which is a primary source of interdependence between thermal and mechanical solutions in fuel performance models. The results indicate that loosely-coupled simulations require significantly more nonlinear iterations, and may lead to convergence trouble when the thermal conductivity of the gap is too small. We also apply the tightly coupled solution strategy to a nuclear fuel simulation of an experiment in a test reactor. Studying the results from these simulations indicates that perhaps convergence for either approach may be problem dependent, i.e., there may be problems for which a loose coupled approach converges, where tightly coupled won't converge and vice versa. (authors)

  12. Results of Small-scale Solid Rocket Combustion Simulator testing at Marshall Space Flight Center

    NASA Astrophysics Data System (ADS)

    Goldberg, Benjamin E.; Cook, Jerry

    1993-06-01

    The Small-scale Solid Rocket Combustion Simulator (SSRCS) program was established at the Marshall Space Flight Center (MSFC), and used a government/industry team consisting of Hercules Aerospace Corporation, Aerotherm Corporation, United Technology Chemical Systems Division, Thiokol Corporation and MSFC personnel to study the feasibility of simulating the combustion species, temperatures and flow fields of a conventional solid rocket motor (SRM) with a versatile simulator system. The SSRCS design is based on hybrid rocket motor principles. The simulator uses a solid fuel and a gaseous oxidizer. Verification of the feasibility of a SSRCS system as a test bed was completed using flow field and system analyses, as well as empirical test data. A total of 27 hot firings of a subscale SSRCS motor were conducted at MSFC. Testing of the Small-scale SSRCS program was completed in October 1992. This paper, a compilation of reports from the above team members and additional analysis of the instrumentation results, will discuss the final results of the analyses and test programs.

  13. Results from Tight and Loose Coupled Multiphysics in Nuclear Fuels Performance Simulations using BISON

    SciTech Connect

    S. R. Novascone; B. W. Spencer; D. Andrs; R. L. Williamson; J. D. Hales; D. M. Perez

    2013-05-01

    The behavior of nuclear fuel in the reactor environment is affected by multiple physics, most notably heat conduction and solid mechanics, which can have a strong influence on each other. To provide credible solutions, a fuel performance simulation code must have the ability to obtain solutions for each of the physics, including coupling between them. Solution strategies for solving systems of coupled equations can be categorized as loosely-coupled, where the individual physics are solved separately, keeping the solutions for the other physics fixed at each iteration, or tightly coupled, where the nonlinear solver simultaneously drives down the residual for each physics, taking into account the coupling between the physics in each nonlinear iteration. In this paper, we compare the performance of loosely and tightly coupled solution algorithms for thermomechanical problems involving coupled thermal and mechanical contact, which is a primary source of interdependence between thermal and mechanical solutions in fuel performance models. The results indicate that loosely-coupled simulations require significantly more nonlinear iterations, and may lead to convergence trouble when the thermal conductivity of the gap is too small. We also apply the tightly coupled solution strategy to a nuclear fuel simulation of an experiment in a test reactor. Studying the results from these simulations indicates that perhaps convergence for either approach may be problem dependent, i.e., there may be problems for which a loose coupled approach converges, where tightly coupled won’t converge and vice versa.

  14. High-Alpha Research Vehicle Lateral-Directional Control Law Description, Analyses, and Simulation Results

    NASA Technical Reports Server (NTRS)

    Davidson, John B.; Murphy, Patrick C.; Lallman, Frederick J.; Hoffler, Keith D.; Bacon, Barton J.

    1998-01-01

    This report contains a description of a lateral-directional control law designed for the NASA High-Alpha Research Vehicle (HARV). The HARV is a F/A-18 aircraft modified to include a research flight computer, spin chute, and thrust-vectoring in the pitch and yaw axes. Two separate design tools, CRAFT and Pseudo Controls, were integrated to synthesize the lateral-directional control law. This report contains a description of the lateral-directional control law, analyses, and nonlinear simulation (batch and piloted) results. Linear analysis results include closed-loop eigenvalues, stability margins, robustness to changes in various plant parameters, and servo-elastic frequency responses. Step time responses from nonlinear batch simulation are presented and compared to design guidelines. Piloted simulation task scenarios, task guidelines, and pilot subjective ratings for the various maneuvers are discussed. Linear analysis shows that the control law meets the stability margin guidelines and is robust to stability and control parameter changes. Nonlinear batch simulation analysis shows the control law exhibits good performance and meets most of the design guidelines over the entire range of angle-of-attack. This control law (designated NASA-1A) was flight tested during the Summer of 1994 at NASA Dryden Flight Research Center.

  15. Laboratory simulations of lidar returns from clouds - Experimental and numerical results

    NASA Astrophysics Data System (ADS)

    Zaccanti, Giovanni; Bruscaglioni, Piero; Gurioli, Massimo; Sansoni, Paola

    1993-03-01

    The experimental results of laboratory simulations of lidar returns from clouds are presented. Measurements were carried out on laboratory-scaled cloud models by using a picosecond laser and a streak-camera system. The turbid structures simulating clouds were suspensions of polystyrene spheres in water. The geometrical situation was similar to that of an actual lidar sounding a cloud 1000 m distant and with a thickness of 300 m. Measurements were repeated for different concentrations and different sizes of spheres. The results show how the effect of multiple scattering depends on the scattering coefficient and on the phase function of the diffusers. The depolarization introduced by multiple scattering was also investigated. The results were also compared with numerical results obtained by Monte Carlo simulations. Substantially good agreement between numerical and experimental results was found. The measurements showed the adequacy of modern electro-optical systems to study the features of multiple-scattering effects on lidar echoes from atmosphere or ocean by means of experiments on well-controlled laboratory-scaled models. This adequacy provides the possibility of studying the influence of different effects in the laboratory in well-controlled situations.

  16. Laboratory simulations of lidar returns from clouds: experimental and numerical results.

    PubMed

    Zaccanti, G; Bruscaglioni, P; Gurioli, M; Sansoni, P

    1993-03-20

    The experimental results of laboratory simulations of lidar returns from clouds are presented. Measurements were carried out on laboratory-scaled cloud models by using a picosecond laser and a streak-camera system. The turbid structures simulating clouds were suspensions of polystyrene spheres in water. The geometrical situation was similar to that of an actual lidar sounding a cloud 1000 m distant and with a thickness of 300 m. Measurements were repeated for different concentrations and different sizes of spheres. The results show how the effect of multiple scattering depends on the scattering coefficient and on the phase function of the diffusers. The depolarization introduced by multiple scattering was also investigated. The results were also compared with numerical results obtained by Monte Carlo simulations. Substantially good agreement between numerical and experimental results was found. The measurements showed the adequacy of modern electro-optical systems to study the features of multiple-scattering effects on lidar echoes from atmosphere or ocean by means of experiments on well-controlled laboratory-scaled models. This adequacy provides the possibility of studying the influence of different effects in the laboratory in well-controlled situations.

  17. Stable water isotope simulation by current land-surface schemes:Results of IPILPS phase 1

    SciTech Connect

    Henderson-Sellers, A.; Fischer, M.; Aleinov, I.; McGuffie, K.; Riley, W.J.; Schmidt, G.A.; Sturm, K.; Yoshimura, K.; Irannejad, P.

    2005-10-31

    Phase 1 of isotopes in the Project for Intercomparison of Land-surface Parameterization Schemes (iPILPS) compares the simulation of two stable water isotopologues ({sup 1}H{sub 2} {sup 18}O and {sup 1}H{sup 2}H{sup 16}O) at the land-atmosphere interface. The simulations are off-line, with forcing from an isotopically enabled regional model for three locations selected to offer contrasting climates and ecotypes: an evergreen tropical forest, a sclerophyll eucalypt forest and a mixed deciduous wood. Here we report on the experimental framework, the quality control undertaken on the simulation results and the method of intercomparisons employed. The small number of available isotopically-enabled land-surface schemes (ILSSs) limits the drawing of strong conclusions but, despite this, there is shown to be benefit in undertaking this type of isotopic intercomparison. Although validation of isotopic simulations at the land surface must await more, and much more complete, observational campaigns, we find that the empirically-based Craig-Gordon parameterization (of isotopic fractionation during evaporation) gives adequately realistic isotopic simulations when incorporated in a wide range of land-surface codes. By introducing two new tools for understanding isotopic variability from the land surface, the Isotope Transfer Function and the iPILPS plot, we show that different hydrological parameterizations cause very different isotopic responses. We show that ILSS-simulated isotopic equilibrium is independent of the total water and energy budget (with respect to both equilibration time and state), but interestingly the partitioning of available energy and water is a function of the models' complexity.

  18. Simulated Driving Assessment (SDA) for Teen Drivers: Results from a Validation Study

    PubMed Central

    McDonald, Catherine C.; Kandadai, Venk; Loeb, Helen; Seacrist, Thomas S.; Lee, Yi-Ching; Winston, Zachary; Winston, Flaura K.

    2015-01-01

    Background Driver error and inadequate skill are common critical reasons for novice teen driver crashes, yet few validated, standardized assessments of teen driving skills exist. The purpose of this study was to evaluate the construct and criterion validity of a newly developed Simulated Driving Assessment (SDA) for novice teen drivers. Methods The SDA's 35-minute simulated drive incorporates 22 variations of the most common teen driver crash configurations. Driving performance was compared for 21 inexperienced teens (age 16–17 years, provisional license ≤90 days) and 17 experienced adults (age 25–50 years, license ≥5 years, drove ≥100 miles per week, no collisions or moving violations ≤3 years). SDA driving performance (Error Score) was based on driving safety measures derived from simulator and eye-tracking data. Negative driving outcomes included simulated collisions or run-off-the-road incidents. A professional driving evaluator/instructor reviewed videos of SDA performance (DEI Score). Results The SDA demonstrated construct validity: 1.) Teens had a higher Error Score than adults (30 vs. 13, p=0.02); 2.) For each additional error committed, the relative risk of a participant's propensity for a simulated negative driving outcome increased by 8% (95% CI: 1.05–1.10, p<0.01). The SDA demonstrated criterion validity: Error Score was correlated with DEI Score (r=−0.66, p<0.001). Conclusions This study supports the concept of validated simulated driving tests like the SDA to assess novice driver skill in complex and hazardous driving scenarios. The SDA, as a standard protocol to evaluate teen driver performance, has the potential to facilitate screening and assessment of teen driving readiness and could be used to guide targeted skill training. PMID:25740939

  19. A computerised third molar surgery simulator--results of supervision by different professionals.

    PubMed

    Rosen, A; Eliassi, S; Fors, U; Sallnäs, E-L; Forsslund, J; Sejersen, R; Lund, B

    2014-05-01

    The purpose of the study was to investigate which supervisory approach afforded the most efficient learning method for undergraduate students in oral and maxillofacial surgery (OMS) using a computerised third molar surgery simulator. Fifth year dental students participated voluntarily in a randomised experimental study using the simulator. The amount of time required and the number of trials used by each student were evaluated as a measure of skills development. Students had the opportunity to practise the procedure until no further visible improvements were achieved. The study assessed four different types of supervision to guide the students. The first group was where they were supported by a teacher/specialist in OMS, the second by a teaching assistant, the third group practised without any supervision and the fourth received help from a simulator technician/engineer. A protocol describing assessment criteria was designed for this purpose, and a questionnaire was completed by all participating students after the study. The average number of attempts required to virtually remove a third molar tooth in the simulator was 1.44 times for the group supervised by an OMS teacher; 1.5 times for those supervised by a teaching assistant; 2.8 times for those who had no supervision; and 3.6 times when support was provided only by a simulator technician. The results showed that the most efficient experience of the students was when they were helped by an OMS teacher or a teaching assistant. In a time and cost-effective perspective, supervision by a teaching assistant for a third molar surgery simulator would be the optimal choice.

  20. Analysis of formation pressure test results in the Mount Elbert methane hydrate reservoir through numerical simulation

    USGS Publications Warehouse

    Kurihara, M.; Sato, A.; Funatsu, K.; Ouchi, H.; Masuda, Y.; Narita, H.; Collett, T.S.

    2011-01-01

    Targeting the methane hydrate (MH) bearing units C and D at the Mount Elbert prospect on the Alaska North Slope, four MDT (Modular Dynamic Formation Tester) tests were conducted in February 2007. The C2 MDT test was selected for history matching simulation in the MH Simulator Code Comparison Study. Through history matching simulation, the physical and chemical properties of the unit C were adjusted, which suggested the most likely reservoir properties of this unit. Based on these properties thus tuned, the numerical models replicating "Mount Elbert C2 zone like reservoir" "PBU L-Pad like reservoir" and "PBU L-Pad down dip like reservoir" were constructed. The long term production performances of wells in these reservoirs were then forecasted assuming the MH dissociation and production by the methods of depressurization, combination of depressurization and wellbore heating, and hot water huff and puff. The predicted cumulative gas production ranges from 2.16??106m3/well to 8.22??108m3/well depending mainly on the initial temperature of the reservoir and on the production method.This paper describes the details of modeling and history matching simulation. This paper also presents the results of the examinations on the effects of reservoir properties on MH dissociation and production performances under the application of the depressurization and thermal methods. ?? 2010 Elsevier Ltd.

  1. Simulating Late Ordovician deep ocean O2 with an earth system climate model. Preliminary results.

    NASA Astrophysics Data System (ADS)

    D'Amico, Daniel F.; Montenegro, Alvaro

    2016-04-01

    The geological record provides several lines of evidence that point to the occurrence of widespread and long lasting deep ocean anoxia during the Late Ordovician, between about 460-440 million years ago (ma). While a series of potential causes have been proposed, there is still large uncertainty regarding how the low oxygen levels came about. Here we use the University of Victoria Earth System Climate Model (UVic ESCM) with Late Ordovician paleogeography to verify the impacts of paleogeography, bottom topography, nutrient loading and cycling and atmospheric concentrations of O2 and CO2 on deep ocean oxygen concentration during the period of interest. Preliminary results so far are based on 10 simulations (some still ongoing) covering the following parameter space: CO2 concentrations of 2240 to 3780 ppmv (~8x to 13x pre-industrial), atmospheric O2 ranging from 8% to 12% per volume, oceanic PO4 and NO3 loading from present day to double present day, reductions in wind speed of 50% and 30% (winds are provided as a boundary condition in the UVic ESCM). For most simulations the deep ocean remains well ventilated. While simulations with higher CO2, lower atmospheric O2 and greater nutrient loading generate lower oxygen concentration in the deep ocean, bottom anoxia - here defined as concentrations <10 μmol L-1 - in these cases is restricted to the high-latitue northern hemisphere. Further simulations will address the impact of greater nutrient loads and bottom topography on deep ocean oxygen concentrations.

  2. Recent results from the GISS model of the global atmosphere. [circulation simulation for weather forecasting

    NASA Technical Reports Server (NTRS)

    Somerville, R. C. J.

    1975-01-01

    Large numerical atmospheric circulation models are in increasingly widespread use both for operational weather forecasting and for meteorological research. The results presented here are from a model developed at the Goddard Institute for Space Studies (GISS) and described in detail by Somerville et al. (1974). This model is representative of a class of models, recently surveyed by the Global Atmospheric Research Program (1974), designed to simulate the time-dependent, three-dimensional, large-scale dynamics of the earth's atmosphere.

  3. Trace the Denmark Strait Overflow Water in an Eddy-Resolving Atlantic Simulation: Some Preliminary Results

    DTIC Science & Technology

    2013-05-01

    Trace the Denmark Strait overflow water in an eddy-resolving Atlantic simulation: some preliminary results Xiaobiao Xu ( COAPS /FSU), Alan...Wallcraft (NRL/SSC), Eric Chassignet ( COAPS /FSU) Thanks: Peter Rhines (UW) and William Schmitz May 21-23, Layered ocean modeling workshop, Ann Arbor, MI...Prediction Studies ( COAPS ),2000 Levy Avenue, Building A, Suite 292,Tallahassee,FL,32306-2741 8. PERFORMING ORGANIZATION REPORT NUMBER 9. SPONSORING

  4. Numerical simulations of soft and hard turbulence - Preliminary results for two-dimensional convection

    NASA Technical Reports Server (NTRS)

    Deluca, E. E.; Werne, J.; Rosner, R.; Cattaneo, F.

    1990-01-01

    Results on the transition from soft to hard turbulence in simulations of two-dimensional Boussinesq convection are reported. The computed probability densities for temperature fluctuations are exponential in form in both soft and hard turbulence, unlike what is observed in experiments. In contrast, a change is obtained in the Nusselt number scaling on Rayleigh number in good agreement with the three-dimensional experiments.

  5. PRELIMINARY RESULTS FROM A SIMULATION OF QUENCHED QCD WITH OVERL AP FERMIONS ON A LARGE LATTICE.

    SciTech Connect

    BERRUTO,F.GARRON,N.HOELBLING,D.LELLOUCH,L.REBBI,C.SHORESH,N.

    2003-07-15

    We simulate quenched QCD with the overlap Dirac operator. We work with the Wilson gauge action at {beta} = 6 on an 18{sup 3} x 64 lattice. We calculate quark propagators for a single source point and quark mass ranging from am{sub 4} = 0.03 to 0.75. We present here preliminary results based on the propagators for 60 gauge field configurations.

  6. High order accurate, one-sided finite-difference approximations to concentration gradients at the boundaries, for the simulation of electrochemical reaction-diffusion problems in one-dimensional space geometry.

    PubMed

    Bieniasz, L K

    2003-07-01

    Accurate calculation of concentration gradients at the boundaries is crucial in electrochemical kinetic simulations, owing to the frequent occurrence of gradient-dependent boundary conditions, and the importance of the gradient-dependent electric current. By using the information about higher spatial derivatives of the concentrations, contained in the time-dependent, kinetic reaction-diffusion partial differential equation(s) in one-dimensional space geometry, under appropriate assumptions it is possible to increase the accuracy orders of the conventional, one-sided n-point finite-difference formulae for the concentration gradients at the boundaries, without increasing n. In this way a new class of high order accurate gradient approximations is derived, and tested in simulations of potential-step chronoamperometric and current-step chronopotentiometric transients for the Reinert-Berg system. The new formulae possess advantages over the conventional gradient approximations. For example, they allow one to obtain a third order accuracy by using two space points only, or fourth order accuracy by using three points, and yet they yield smaller errors than the conventional four-point, or five-point formulae, respectively. Needing fewer points, for approximating the gradients with a given accuracy, simplifies also the solution of the linear algebraic equations arising from the application of implicit time integration schemes.

  7. Obtaining Identical Results on Varying Numbers of Processors In Domain Decomposed particle Monte Carlo Simulations

    SciTech Connect

    Gentile, N A; Kalos, M H; Brunner, T A

    2005-03-22

    Domain decomposed Monte Carlo codes, like other domain-decomposed codes, are difficult to debug. Domain decomposition is prone to error, and interactions between the domain decomposition code and the rest of the algorithm often produces subtle bugs. These bugs are particularly difficult to find in a Monte Carlo algorithm, in which the results have statistical noise. Variations in the results due to statistical noise can mask errors when comparing the results to other simulations or analytic results. If a code can get the same result on one domain as on many, debugging the whole code is easier. This reproducibility property is also desirable when comparing results done on different numbers of processors and domains. We describe how reproducibility, to machine precision, is obtained on different numbers of domains in an Implicit Monte Carlo photonics code.

  8. Spatial resolution effect on the simulated results of watershed scale models

    NASA Astrophysics Data System (ADS)

    Epelde, Ane; Antiguedad, Iñaki; Brito, David; Jauch, Eduardo; Neves, Ramiro; Sauvage, Sabine; Sánchez-Pérez, José Miguel

    2016-04-01

    Numerical models are useful tools for water resources planning, development and management. Currently, their use is being spread and more complex modeling systems are being employed for these purposes. The adding of complexity allows the simulation of water quality related processes. Nevertheless, this implies a considerable increase on the computational requirements, which usually is compensated on the models by a decrease on their spatial resolution. The spatial resolution of the models is known to affect the simulation of hydrological processes and therefore, also the nutrient exportation and cycling processes. However, the implication of the spatial resolution on the simulated results is rarely assessed. In this study, we examine the effect of the change in the grid size on the integrated and distributed results of the Alegria River watershed model (Basque Country, Northern Spain). Variables such as discharge, water table level, relative water content of soils, nitrogen exportation and denitrification are analyzed in order to quantify the uncertainty involved in the spatial discretization of the watershed scale models. This is an aspect that needs to be carefully considered when numerical models are employed in watershed management studies or quality programs.

  9. Comparisons of Observations with Results from 3D Simulations and Implications for Predictions of Ozone Recovery

    NASA Technical Reports Server (NTRS)

    Douglass, Anne R.; Stolarski, Richard S.; Strahan, Susan E.; Steenrod, Stephen D.; Polarsky, Brian C.

    2004-01-01

    Although chemistry and transport models (CTMs) include the same basic elements (photo- chemical mechanism and solver, photolysis scheme, meteorological fields, numerical transport scheme), they produce different results for the future recovery of stratospheric ozone as chlorofluorcarbons decrease. Three simulations will be contrasted: the Global Modeling Initiative (GMI) CTM driven by a single year\\'s winds from a general circulation model; the GMI CTM driven by a single year\\'s winds from a data assimilation system; the NASA GSFC CTM driven by a winds from a multi-year GCM simulation. CTM results for ozone and other constituents will be compared with each other and with observations from ground-based and satellite platforms to address the following: Does the simulated ozone tendency and its latitude, altitude and seasonal dependence match that derived from observations? Does the balance from analysis of observations? Does the balance among photochemical processes match that expected from observations? Can the differences in prediction for ozone recovery be anticipated from these comparisons?

  10. Molecular simulation of aqueous electrolytes: water chemical potential results and Gibbs-Duhem equation consistency tests.

    PubMed

    Moučka, Filip; Nezbeda, Ivo; Smith, William R

    2013-09-28

    This paper deals with molecular simulation of the chemical potentials in aqueous electrolyte solutions for the water solvent and its relationship to chemical potential simulation results for the electrolyte solute. We use the Gibbs-Duhem equation linking the concentration dependence of these quantities to test the thermodynamic consistency of separate calculations of each quantity. We consider aqueous NaCl solutions at ambient conditions, using the standard SPC/E force field for water and the Joung-Cheatham force field for the electrolyte. We calculate the water chemical potential using the osmotic ensemble Monte Carlo algorithm by varying the number of water molecules at a constant amount of solute. We demonstrate numerical consistency of these results in terms of the Gibbs-Duhem equation in conjunction with our previous calculations of the electrolyte chemical potential. We present the chemical potential vs molality curves for both solvent and solute in the form of appropriately chosen analytical equations fitted to the simulation data. As a byproduct, in the context of the force fields considered, we also obtain values for the Henry convention standard molar chemical potential for aqueous NaCl using molality as the concentration variable and for the chemical potential of pure SPC/E water. These values are in reasonable agreement with the experimental values.

  11. Result-driven exploration of simulation parameter spaces for visual effects design.

    PubMed

    Bruckner, Stefan; Möller, Torsten

    2010-01-01

    Graphics artists commonly employ physically-based simulation for the generation of effects such as smoke, explosions, and similar phenomena. The task of finding the correct parameters for a desired result, however, is difficult and time-consuming as current tools provide little to no guidance. In this paper, we present a new approach for the visual exploration of such parameter spaces. Given a three-dimensional scene description, we utilize sampling and spatio-temporal clustering techniques to generate a concise overview of the achievable variations and their temporal evolution. Our visualization system then allows the user to explore the simulation space in a goal-oriented manner. Animation sequences with a set of desired characteristics can be composed using a novel search-by-example approach and interactive direct volume rendering is employed to provide instant visual feedback. A user study was performed to evaluate the applicability of our system in production use.

  12. Preliminary Analysis and Simulation Results of Microwave Transmission Through an Electron Cloud

    SciTech Connect

    Sonnad, Kiran; Sonnad, Kiran; Furman, Miguel; Veitzer, Seth; Stoltz, Peter; Cary, John

    2007-01-12

    The electromagnetic particle-in-cell (PIC) code VORPAL is being used to simulate the interaction of microwave radiation through an electron cloud. The results so far showgood agreement with theory for simple cases. The study has been motivated by previous experimental work on this problem at the CERN SPS [1], experiments at the PEP-II Low Energy Ring (LER) at SLAC [4], and proposed experiments at the Fermilab Main Injector (MI). With experimental observation of quantities such as amplitude, phase and spectrum of the output microwave radiation and with support from simulations for different cloud densities and applied magnetic fields, this technique can prove to be a useful probe for assessing the presence as well as the densityof electron clouds.

  13. Simulation and experimental results of optical and thermal modeling of gold nanoshells.

    PubMed

    Ghazanfari, Lida; Khosroshahi, Mohammad E

    2014-09-01

    This paper proposes a generalized method for optical and thermal modeling of synthesized magneto-optical nanoshells (MNSs) for biomedical applications. Superparamagnetic magnetite nanoparticles with diameter of 9.5 ± 1.4 nm are fabricated using co-precipitation method and subsequently covered by a thin layer of gold to obtain 15.8 ± 3.5 nm MNSs. In this paper, simulations and detailed analysis are carried out for different nanoshell geometry to achieve a maximum heat power. Structural, magnetic and optical properties of MNSs are assessed using vibrating sample magnetometer (VSM), X-ray diffraction (XRD), UV-VIS spectrophotometer, dynamic light scattering (DLS), and transmission electron microscope (TEM). Magnetic saturation of synthesized magnetite nanoparticles are reduced from 46.94 to 11.98 emu/g after coating with gold. The performance of the proposed optical-thermal modeling technique is verified by simulation and experimental results.

  14. RESULTS OF CESIUM MASS TRANSFER TESTING FOR NEXT GENERATION SOLVENT WITH HANFORD WASTE SIMULANT AP-101

    SciTech Connect

    Peters, T.; Washington, A.; Fink, S.

    2011-09-27

    SRNL has performed an Extraction, Scrub, Strip (ESS) test using the next generation solvent and AP-101 Hanford Waste simulant. The results indicate that the next generation solvent (MG solvent) has adequate extraction behavior even in the face of a massive excess of potassium. The stripping results indicate poorer behavior, but this may be due to inadequate method detection limits. SRNL recommends further testing using hot tank waste or spiked simulant to provide for better detection limits. Furthermore, strong consideration should be given to performing an actual waste, or spiked waste demonstration using the 2cm contactor bank. The Savannah River Site currently utilizes a solvent extraction technology to selectively remove cesium from tank waste at the Multi-Component Solvent Extraction unit (MCU). This solvent consists of four components: the extractant - BoBCalixC6, a modifier - Cs-7B, a suppressor - trioctylamine, and a diluent, Isopar L{trademark}. This solvent has been used to successfully decontaminate over 2 million gallons of tank waste. However, recent work at Oak Ridge National Laboratory (ORNL), Argonne National Laboratory (ANL), and Savannah River National Laboratory (SRNL) has provided a basis to implement an improved solvent blend. This new solvent blend - referred to as Next Generation Solvent (NGS) - is similar to the current solvent, and also contains four components: the extractant - MAXCalix, a modifier - Cs-7B, a suppressor - LIX-79{trademark} guanidine, and a diluent, Isopar L{trademark}. Testing to date has shown that this 'Next Generation' solvent promises to provide far superior cesium removal efficiencies, and furthermore, is theorized to perform adequately even in waste with high potassium concentrations such that it could be used for processing Hanford wastes. SRNL has performed a cesium mass transfer test in to confirm this behavior, using a simulant designed to simulate Hanford AP-101 waste.

  15. Computer simulation applied to jewellery casting: challenges, results and future possibilities

    NASA Astrophysics Data System (ADS)

    Tiberto, Dario; Klotz, Ulrich E.

    2012-07-01

    Computer simulation has been successfully applied in the past to several industrial processes (such as lost foam and die casting) by larger foundries and direct automotive suppliers, while for the jewelry sector it is a procedure which is not widespread, and which has been tested mainly in the context of research projects. On the basis of a recently concluded EU project, the authors here present the simulation of investment casting, using two different softwares: one for the filling step (Flow-3D®), the other one for the solidification (PoligonSoft®). A work on material characterization was conducted to obtain the necessary physical parameters for the investment (used for the mold) and for the gold alloys (through thermal analysis). A series of 18k and 14k gold alloys were cast in standard set-ups to have a series of benchmark trials with embedded thermocouples for temperature measurement, in order to compare and validate the software output in terms of the cooling curves for definite test parts. Results obtained with the simulation included the reduction of micro-porosity through an optimization of the feeding channels for a controlled solidification of the metal: examples of the predicted porosity in the cast parts (with metallographic comparison) will be shown. Considerations on the feasibility of applying the casting simulation in the jewelry sector will be reached, underlining the importance of the software parametrization necessary to obtain reliable results, and the discrepancies found with the experimental comparison. In addition an overview on further possibilities of application for the CFD in jewellery casting, such as the modeling of the centrifugal and tilting processes, will be presented.

  16. A new model to simulate the Martian mesoscale and microscale atmospheric circulation: Validation and first results

    NASA Astrophysics Data System (ADS)

    Spiga, Aymeric; Forget, François

    2009-02-01

    associated dynamics: convective motions, overlying gravity waves, and dust devil-like vortices. Modeled temperature profiles are in satisfactory agreement with the Miniature Thermal Emission Spectrometer (Mini-TES) measurements. The ability of the model to transport tracers at regional scales is exemplified by the model's prediction for the altitude of the Tharsis topographical water ice clouds in the afternoon. Finally, a nighttime ``warm ring'' at the base of Olympus Mons is identified in the simulations, resulting from adiabatic warming by the intense downslope winds along the flanks of the volcano. The surface temperature enhancement reaches +20 K throughout the night. Such a phenomenon may have adversely affected the thermal inertia derivations in the region.

  17. SRG110 Stirling Generator Dynamic Simulator Vibration Test Results and Analysis Correlation

    NASA Technical Reports Server (NTRS)

    Suarez, Vicente J.; Lewandowski, Edward J.; Callahan, John

    2006-01-01

    The U.S. Department of Energy (DOE), Lockheed Martin (LM), and NASA Glenn Research Center (GRC) have been developing the Stirling Radioisotope Generator (SRG110) for use as a power system for space science missions. The launch environment enveloping potential missions results in a random input spectrum that is significantly higher than historical RPS launch levels and is a challenge for designers. Analysis presented in prior work predicted that tailoring the compliance at the generator-spacecraft interface reduced the dynamic response of the system thereby allowing higher launch load input levels and expanding the range of potential generator missions. To confirm analytical predictions, a dynamic simulator representing the generator structure, Stirling convertors and heat sources was designed and built for testing with and without a compliant interface. Finite element analysis was performed to guide the generator simulator and compliant interface design so that test modes and frequencies were representative of the SRG110 generator. This paper presents the dynamic simulator design, the test setup and methodology, test article modes and frequencies and dynamic responses, and post-test analysis results. With the compliant interface, component responses to an input environment exceeding the SRG110 qualification level spectrum were all within design allowables. Post-test analysis included finite element model tuning to match test frequencies and random response analysis using the test input spectrum. Analytical results were in good overall agreement with the test results and confirmed previous predictions that the SRG110 power system may be considered for a broad range of potential missions, including those with demanding launch environments.

  18. SRG110 Stirling Generator Dynamic Simulator Vibration Test Results and Analysis Correlation

    NASA Technical Reports Server (NTRS)

    Lewandowski, Edward J.; Suarez, Vicente J.; Goodnight, Thomas W.; Callahan, John

    2007-01-01

    The U.S. Department of Energy (DOE), Lockheed Martin (LM), and NASA Glenn Research Center (GRC) have been developing the Stirling Radioisotope Generator (SRG110) for use as a power system for space science missions. The launch environment enveloping potential missions results in a random input spectrum that is significantly higher than historical radioisotope power system (RPS) launch levels and is a challenge for designers. Analysis presented in prior work predicted that tailoring the compliance at the generator-spacecraft interface reduced the dynamic response of the system thereby allowing higher launch load input levels and expanding the range of potential generator missions. To confirm analytical predictions, a dynamic simulator representing the generator structure, Stirling convertors and heat sources were designed and built for testing with and without a compliant interface. Finite element analysis was performed to guide the generator simulator and compliant interface design so that test modes and frequencies were representative of the SRG110 generator. This paper presents the dynamic simulator design, the test setup and methodology, test article modes and frequencies and dynamic responses, and post-test analysis results. With the compliant interface, component responses to an input environment exceeding the SRG110 qualification level spectrum were all within design allowables. Post-test analysis included finite element model tuning to match test frequencies and random response analysis using the test input spectrum. Analytical results were in good overall agreement with the test results and confirmed previous predictions that the SRG110 power system may be considered for a broad range of potential missions, including those with demanding launch environments.

  19. Flow-driven cloud formation and fragmentation: results from Eulerian and Lagrangian simulations

    NASA Astrophysics Data System (ADS)

    Heitsch, Fabian; Naab, Thorsten; Walch, Stefanie

    2011-07-01

    The fragmentation of shocked flows in a thermally bistable medium provides a natural mechanism to form turbulent cold clouds as precursors to molecular clouds. Yet because of the large density and temperature differences and the range of dynamical scales involved, following this process with numerical simulations is challenging. We compare two-dimensional simulations of flow-driven cloud formation without self-gravity, using the Lagrangian smoothed particle hydrodynamics (SPH) code VINE and the Eulerian grid code PROTEUS. Results are qualitatively similar for both methods, yet the variable spatial resolution of the SPH method leads to smaller fragments and thinner filaments, rendering the overall morphologies different. Thermal and hydrodynamical instabilities lead to rapid cooling and fragmentation into cold clumps with temperatures below 300 K. For clumps more massive than 1 M⊙ pc-1, the clump mass function has an average slope of -0.8. The internal velocity dispersion of the clumps is nearly an order of magnitude smaller than their relative motion, rendering it subsonic with respect to the internal sound speed of the clumps but supersonic as seen by an external observer. For the SPH simulations most of the cold gas resides at temperatures below 100 K, while the grid-based models show an additional, substantial component between 100 and 300 K. Independent of the numerical method, our models confirm that converging flows of warm neutral gas fragment rapidly and form high-density, low-temperature clumps as possible seeds for star formation.

  20. Mechanisms of Core-Collapse Supernovae & Simulation Results from the CHIMERA Code

    NASA Astrophysics Data System (ADS)

    Bruenn, S. W.; Mezzacappa, A.; Hix, W. R.; Blondin, J. M.; Marronetti, P.; Messer, O. E. B.; Dirk, C. J.; Yoshida, S.

    2009-05-01

    Unraveling the mechanism for core-collapse supernova explosions is an outstanding computational challenge and the problem remains essentially unsolved despite more than four decades of effort. However, much progress in realistic modeling has occurred recently through the availability of multi-teraflop machines and the increasing sophistication of supernova codes. These improvements have led to some key insights which may clarify the picture in the not too distant future. Here we briefly review the current status of the three explosion mechanisms (acoustic, MHD, and neutrino heating) that are currently under active investigation, concentrating on the neutrino heating mechanism as the one most likely responsible for producing explosions from progenitors in the mass range ~10 to ~25Msolar. We then briefly describe the CHIMERA code, a supernova code we have developed to simulate core-collapse supernovae in 1, 2, and 3 spatial dimensions. We finally describe the results of an ongoing suite of 2D simulations initiated from a 12, 15, 20, and 25Msolar progenitor. These have all exhibited explosions and are currently in the expanding phase with the shock at between 5,000 and 10,000 km. We finally very briefly describe an ongoing simulation in 3 spatial dimensions initiated from the 15Msolar progenitor.

  1. Development of ADOCS controllers and control laws. Volume 3: Simulation results and recommendations

    NASA Technical Reports Server (NTRS)

    Landis, Kenneth H.; Glusman, Steven I.

    1985-01-01

    The Advanced Cockpit Controls/Advanced Flight Control System (ACC/AFCS) study was conducted by the Boeing Vertol Company as part of the Army's Advanced Digital/Optical Control System (ADOCS) program. Specifically, the ACC/AFCS investigation was aimed at developing the flight control laws for the ADOCS demonstator aircraft which will provide satisfactory handling qualities for an attack helicopter mission. The three major elements of design considered are as follows: Pilot's integrated Side-Stick Controller (SSC) -- Number of axes controlled; force/displacement characteristics; ergonomic design. Stability and Control Augmentation System (SCAS)--Digital flight control laws for the various mission phases; SCAS mode switching logic. Pilot's Displays--For night/adverse weather conditions, the dynamics of the superimposed symbology presented to the pilot in a format similar to the Advanced Attack Helicopter (AAH) Pilot Night Vision System (PNVS) for each mission phase is a function of SCAS characteristics; display mode switching logic. Results of the five piloted simulations conducted at the Boeing Vertol and NASA-Ames simulation facilities are presented in Volume 3. Conclusions drawn from analysis of pilot rating data and commentary were used to formulate recommendations for the ADOCS demonstrator flight control system design. The ACC/AFCS simulation data also provide an extensive data base to aid the development of advanced flight control system design for future V/STOL aircraft.

  2. Effects of heterogeneity in aquifer permeability and biomass on biodegradation rate calculations - Results from numerical simulations

    USGS Publications Warehouse

    Scholl, M.A.

    2000-01-01

    Numerical simulations were used to examine the effects of heterogeneity in hydraulic conductivity (K) and intrinsic biodegradation rate on the accuracy of contaminant plume-scale biodegradation rates obtained from field data. The simulations were based on a steady-state BTEX contaminant plume-scale biodegradation under sulfate-reducing conditions, with the electron acceptor in excess. Biomass was either uniform or correlated with K to model spatially variable intrinsic biodegradation rates. A hydraulic conductivity data set from an alluvial aquifer was used to generate three sets of 10 realizations with different degrees of heterogeneity, and contaminant transport with biodegradation was simulated with BIOMOC. Biodegradation rates were calculated from the steady-state contaminant plumes using decreases in concentration with distance downgradient and a single flow velocity estimate, as is commonly done in site characterization to support the interpretation of natural attenuation. The observed rates were found to underestimate the actual rate specified in the heterogeneous model in all cases. The discrepancy between the observed rate and the 'true' rate depended on the ground water flow velocity estimate, and increased with increasing heterogeneity in the aquifer. For a lognormal K distribution with variance of 0.46, the estimate was no more than a factor of 1.4 slower than the true rate. For aquifer with 20% silt/clay lenses, the rate estimate was as much as nine times slower than the true rate. Homogeneous-permeability, uniform-degradation rate simulations were used to generate predictions of remediation time with the rates estimated from heterogeneous models. The homogeneous models were generally overestimated the extent of remediation or underestimated remediation time, due to delayed degradation of contaminants in the low-K areas. Results suggest that aquifer characterization for natural attenuation at contaminated sites should include assessment of the presence

  3. Modelling Study at Kutlular Copper FIELD with Spat This Study, Evaluation Steps of Copper Mine Field SP Data Are Shown How to Reach More Accurate Results for SP Inversion Method.

    NASA Astrophysics Data System (ADS)

    Sahin, O. K.; Asci, M.

    2014-12-01

    At this study, determination of theoretical parameters for inversion process of Trabzon-Sürmene-Kutlular ore bed anomalies was examined. Making a decision of which model equation can be used for inversion is the most important step for the beginning. It is thought that will give a chance to get more accurate results. So, sections were evaluated with sphere-cylinder nomogram. After that, same sections were analyzed with cylinder-dike nomogram to determine the theoretical parameters for inversion process for every single model equations. After comparison of results, we saw that only one of them was more close to parameters of nomogram evaluations. But, other inversion result parameters were different from their nomogram parameters.

  4. Galaxy Properties and UV Escape Fractions during the Epoch of Reionization: Results from the Renaissance Simulations

    NASA Astrophysics Data System (ADS)

    Xu, Hao; Wise, John H.; Norman, Michael L.; Ahn, Kyungjin; O'Shea, Brian W.

    2016-12-01

    Cosmic reionization is thought to be primarily fueled by the first generations of galaxies. We examine their stellar and gaseous properties, focusing on the star formation rates and the escape of ionizing photons, as a function of halo mass, redshift, and environment using the full suite of the Renaissance Simulations with an eye to provide better inputs to global reionization simulations. This suite probes overdense, average, and underdense regions of the universe of several hundred comoving Mpc3, each yielding a sample of over 3000 halos in the mass range of 107-109.5 {M}⊙ at their final redshifts of 15, 12.5, and 8, respectively. In the process, we simulate the effects of radiative and supernova feedback from 5000 to 10,000 Population III stars in each simulation. We find that halos as small as 107 {M}⊙ are able to host bursty star formation due to metal-line cooling from earlier enrichment by massive Population III stars. Using our large sample, we find that the galaxy-halo occupation fraction drops from unity at virial masses above 108.5 {M}⊙ to ˜50% at 108 {M}⊙ and ˜10% at 107 {M}⊙ , quite independent of redshift and region. Their average ionizing escape fraction is ˜5% in the mass range of 108-109 {M}⊙ and increases with decreasing halo mass below this range, reaching 40%-60% at 107 {M}⊙ . Interestingly, we find that the escape fraction varies between 10%-20% in halos with virial masses of ˜3 × 109 {M}⊙ . Taken together, our results confirm the importance of the smallest galaxies as sources of ionizing radiation contributing to the reionization of the universe.

  5. Accurate spectral color measurements

    NASA Astrophysics Data System (ADS)

    Hiltunen, Jouni; Jaeaeskelaeinen, Timo; Parkkinen, Jussi P. S.

    1999-08-01

    Surface color measurement is of importance in a very wide range of industrial applications including paint, paper, printing, photography, textiles, plastics and so on. For a demanding color measurements spectral approach is often needed. One can measure a color spectrum with a spectrophotometer using calibrated standard samples as a reference. Because it is impossible to define absolute color values of a sample, we always work with approximations. The human eye can perceive color difference as small as 0.5 CIELAB units and thus distinguish millions of colors. This 0.5 unit difference should be a goal for the precise color measurements. This limit is not a problem if we only want to measure the color difference of two samples, but if we want to know in a same time exact color coordinate values accuracy problems arise. The values of two instruments can be astonishingly different. The accuracy of the instrument used in color measurement may depend on various errors such as photometric non-linearity, wavelength error, integrating sphere dark level error, integrating sphere error in both specular included and specular excluded modes. Thus the correction formulas should be used to get more accurate results. Another question is how many channels i.e. wavelengths we are using to measure a spectrum. It is obvious that the sampling interval should be short to get more precise results. Furthermore, the result we get is always compromise of measuring time, conditions and cost. Sometimes we have to use portable syste or the shape and the size of samples makes it impossible to use sensitive equipment. In this study a small set of calibrated color tiles measured with the Perkin Elmer Lamda 18 and the Minolta CM-2002 spectrophotometers are compared. In the paper we explain the typical error sources of spectral color measurements, and show which are the accuracy demands a good colorimeter should have.

  6. Conversion of NIMROD simulation results for graphical analysis using VisIt

    SciTech Connect

    Romero-Talamas, C A

    2006-05-03

    Software routines developed to prepare NIMROD [C. R. Sovinec et al., J. Comp. Phys. 195, 355 (2004)] results for three-dimensional visualization from simulations of the Sustained Spheromak Physics Experiment (SSPX ) [E. B. Hooper et al., Nucl. Fusion 39, 863 (1999)] are presented here. The visualization is done by first converting the NIMROD output to a format known as legacy VTK and then loading it to VisIt, a graphical analysis tool that includes three-dimensional rendering and various mathematical operations for large data sets. Sample images obtained from the processing of NIMROD data with VisIt are included.

  7. Results and simulation of the prototype detection unit of KM3NeT-ARCA

    NASA Astrophysics Data System (ADS)

    Hugon, C. M. F.

    2017-03-01

    KM3NeT-ARCA is a deep sea high energy neutrino detector. A detection unit prototype was deployed in the future KM3NeT-ARCA deep-sea site, off of the Sicilian coast. This detection unit is composed of a line of 3 digital optical modules with 31 photomultiplier tubes on each one. The prototype detection unit was operated since its deployment in May 2014 until its decommissioning in July 2015. The results of the calibration of this detection unit and its simulation are presented and discussed.

  8. The Mayfield method of estimating nesting success: A model, estimators and simulation results

    USGS Publications Warehouse

    Hensler, G.L.; Nichols, J.D.

    1981-01-01

    Using a nesting model proposed by Mayfield we show that the estimator he proposes is a maximum likelihood estimator (m.l.e.). M.l.e. theory allows us to calculate the asymptotic distribution of this estimator, and we propose an estimator of the asymptotic variance. Using these estimators we give approximate confidence intervals and tests of significance for daily survival. Monte Carlo simulation results show the performance of our estimators and tests under many sets of conditions. A traditional estimator of nesting success is shown to be quite inferior to the Mayfield estimator. We give sample sizes required for a given accuracy under several sets of conditions.

  9. Entry, Descent and Landing Systems Analysis: Exploration Class Simulation Overview and Results

    NASA Technical Reports Server (NTRS)

    DwyerCianciolo, Alicia M.; Davis, Jody L.; Shidner, Jeremy D.; Powell, Richard W.

    2010-01-01

    NASA senior management commissioned the Entry, Descent and Landing Systems Analysis (EDL-SA) Study in 2008 to identify and roadmap the Entry, Descent and Landing (EDL) technology investments that the agency needed to make in order to successfully land large payloads at Mars for both robotic and exploration or human-scale missions. The year one exploration class mission activity considered technologies capable of delivering a 40-mt payload. This paper provides an overview of the exploration class mission study, including technologies considered, models developed and initial simulation results from the EDL-SA year one effort.

  10. JT9D performance deterioration results from a simulated aerodynamic load test

    NASA Technical Reports Server (NTRS)

    Stakolich, E. G.; Stromberg, W. J.

    1981-01-01

    The results of testing to identify the effects of simulated aerodynamic flight loads on JT9D engine performance are presented. The test results were also used to refine previous analytical studies on the impact of aerodynamic flight loads on performance losses. To accomplish these objectives, a JT9D-7AH engine was assembled with average production clearances and new seals as well as extensive instrumentation to monitor engine performance, case temperatures, and blade tip clearance changes. A special loading device was designed and constructed to permit application of known moments and shear forces to the engine by the use of cables placed around the flight inlet. The test was conducted in the Pratt & Whitney Aircraft X-Ray Test Facility to permit the use of X-ray techniques in conjunction with laser blade tip proximity probes to monitor important engine clearance changes. Upon completion of the test program, the test engine was disassembled, and the condition of gas path parts and final clearances were documented. The test results indicate that the engine lost 1.1 percent in thrust specific fuel consumption (TSFC), as measured under sea level static conditions, due to increased operating clearances caused by simulated flight loads. This compares with 0.9 percent predicted by the analytical model and previous study efforts.

  11. Results from the simulations of geopotential coefficient estimation from gravity gradients

    NASA Astrophysics Data System (ADS)

    Bettadpur, S.; Schutz, B. E.; Lundberg, J. B.

    New information of the short and medium wavelength components of the geopotential is expected from the measurements of gravity gradients made by the future ESA Aristoteles and the NASA Superconducting Gravity Gradiometer missions. In this paper, results are presented from preliminary simulations concerning the estimation of the spherical harmonic coefficients of the geopotential expansion from gravity gradients data. Numerical issues in the brute-force inversion (BFI) of the gravity gradients data are examined, and numerical algorithms are developed that substantially speed up the computation of the potential, acceleration, and gradients, as well as the mapping from the gravity gradients to the geopotential coefficients. The solution of a large least squares problem is also examined, and computational requirements are determined for the implementation of a large scale inversion. A comparative analysis of the results from the BFI and a symmetry method is reported for the test simulations of the estimation of a degree and order 50 gravity field. The results from the two, in the presence of white noise, are seen to compare well. The latter method is implemented on a special, axially symmetric surface that fits the orbit within 380 meters.

  12. Influence of land use on rainfall simulation results in the Souss basin, Morocco

    NASA Astrophysics Data System (ADS)

    Peter, Klaus Daniel; Ries, Johannes B.; Hssaine, Ali Ait

    2013-04-01

    Situated between the High and Anti-Atlas, the Souss basin is characterized by a dynamic land use change. It is one of the fastest growing agricultural regions of Morocco. Traditional mixed agriculture is replaced by extensive plantations of citrus fruits, bananas and vegetables in monocropping, mainly for the European market. For the implementation of the land use change and further expansion of the plantations into marginal land which was former unsuitable for agriculture, land levelling by heavy machinery is used to plane the fields and close the widespread gullies. These gully systems are cutting deep between the plantations and other arable land. Their development started already over 400 years ago with the introduction of sugar production. Heavy rainfall events lead to further strong soil and gully erosion in this with 200 mm mean annual precipitation normally arid region. Gullies are cutting into the arable land or are re-excavating their old stream courses. On the test sites around the city of Taroudant, a total of 122 rainfall simulations were conducted to analyze the susceptibility of soils to surface runoff and soil erosion under different land use. A small portable nozzle rainfall simulator is used for the rainfall simulation experiments, quantifying runoff and erosion rates on micro-plots with a size of 0.28 m2. A motor pump boosts the water regulated by a flow metre into the commercial full cone nozzle at a height of 2 m. The rainfall intensity is maintained at about 40 mm h-1 for each of the 30 min lasting experiments. Ten categories of land use are classified for different stages of levelling, fallow land, cultivation and rangeland. Results show that mean runoff coefficients and mean sediment loads are significantly higher (1.4 and 3.5 times respectively) on levelled study sites compared to undisturbed sites. However, the runoff coefficients of all land use types are relatively equal and reach high median coefficients from 39 to 56 %. Only the

  13. SZ effects in the Magneticum Pathfinder simulation: comparison with the Planck, SPT, and ACT results

    NASA Astrophysics Data System (ADS)

    Dolag, K.; Komatsu, E.; Sunyaev, R.

    2016-12-01

    We calculate the one-point probability density distribution functions (PDF) and the power spectra of the thermal and kinetic Sunyaev-Zeldovich (tSZ and kSZ) effects and the mean Compton Y parameter using the Magneticum Pathfinder simulations, state-of-the-art cosmological hydrodynamical simulations of a large cosmological volume of (896 Mpc h-1)3. These simulations follow in detail the thermal and chemical evolution of the intracluster medium as well as the evolution of supermassive black holes and their associated feedback processes. We construct full-sky maps of tSZ and kSZ from the light-cones out to z = 0.17, and one realization of 8.8° × 8.8° deep light-cone out to z = 5.2. The local universe at z < 0.027 is simulated by a constrained realization. The tail of the one-point PDF of tSZ from the deep light-cone follows a power-law shape with an index of -3.2. Once convolved with the effective beam of Planck, it agrees with the PDF measured by Planck. The predicted tSZ power spectrum agrees with that of the Planck data at all multipoles up to l ≈ 1000, once the calculations are scaled to the Planck 2015 cosmological parameters with Ωm = 0.308 and σ8 = 0.8149. Consistent with the results in the literature, however, we continue to find the tSZ power spectrum at l = 3000 that is significantly larger than that estimated from the high-resolution ground-based data. The simulation predicts the mean fluctuating Compton Y value of bar{Y}=1.18× 10^{-6} for Ωm = 0.272 and σ8 = 0.809. Nearly half (≈5 × 10-7) of the signal comes from haloes below a virial mass of 1013 M⊙ h-1. Scaling this to the Planck 2015 parameters, we find bar{Y}=1.57× {}10^{-6}.

  14. RESULTS OF COPPER CATALYZED PEROXIDE OXIDATION (CCPO) OF TANK 48H SIMULANTS

    SciTech Connect

    Peters, T.; Pareizs, J.; Newell, J.; Fondeur, F.; Nash, C.; White, T.; Fink, S.

    2012-08-14

    Savannah River National Laboratory (SRNL) performed a series of laboratory-scale experiments that examined copper-catalyzed hydrogen peroxide (H{sub 2}O{sub 2}) aided destruction of organic components, most notably tetraphenylborate (TPB), in Tank 48H simulant slurries. The experiments were designed with an expectation of conducting the process within existing vessels of Building 241-96H with minimal modifications to the existing equipment. Results of the experiments indicate that TPB destruction levels exceeding 99.9% are achievable, dependent on the reaction conditions. The following observations were made with respect to the major processing variables investigated. A lower reaction pH provides faster reaction rates (pH 7 > pH 9 > pH 11); however, pH 9 reactions provide the least quantity of organic residual compounds within the limits of species analyzed. Higher temperatures lead to faster reaction rates and smaller quantities of organic residual compounds. Higher concentrations of the copper catalyst provide faster reaction rates, but the highest copper concentration (500 mg/L) also resulted in the second highest quantity of organic residual compounds. Faster rates of H{sub 2}O{sub 2} addition lead to faster reaction rates and lower quantities of organic residual compounds. Testing with simulated slurries continues. Current testing is examining lower copper concentrations, refined peroxide addition rates, and alternate acidification methods. A revision of this report will provide updated findings with emphasis on defining recommended conditions for similar tests with actual waste samples.

  15. Natural frequencies of two bubbles in a compliant tube: Analytical, simulation, and experimental results

    PubMed Central

    Jang, Neo W.; Zakrzewski, Aaron; Rossi, Christina; Dalecki, Diane; Gracewski, Sheryl

    2011-01-01

    Motivated by various clinical applications of ultrasound contrast agents within blood vessels, the natural frequencies of two bubbles in a compliant tube are studied analytically, numerically, and experimentally. A lumped parameter model for a five degree of freedom system was developed, accounting for the compliance of the tube and coupled response of the two bubbles. The results were compared to those produced by two different simulation methods: (1) an axisymmetric coupled boundary element and finite element code previously used to investigate the response of a single bubble in a compliant tube and (2) finite element models developed in comsol Multiphysics. For the simplified case of two bubbles in a rigid tube, the lumped parameter model predicts two frequencies for in- and out-of-phase oscillations, in good agreement with both numerical simulation and experimental results. For two bubbles in a compliant tube, the lumped parameter model predicts four nonzero frequencies, each asymptotically converging to expected values in the rigid and compliant limits of the tube material. PMID:22088008

  16. Evolution of star cluster systems in isolated galaxies: first results from direct N-body simulations

    NASA Astrophysics Data System (ADS)

    Rossi, L. J.; Bekki, K.; Hurley, J. R.

    2016-11-01

    The evolution of star clusters is largely affected by the tidal field generated by the host galaxy. It is thus in principle expected that under the assumption of a `universal' initial cluster mass function the properties of the evolved present-day mass function of star cluster systems should show a dependence on the properties of the galactic environment in which they evolve. To explore this expectation, a sophisticated model of the tidal field is required in order to study the evolution of star cluster systems in realistic galaxies. Along these lines, in this work we first describe a method developed for coupling N-body simulations of galaxies and star clusters. We then generate a data base of galaxy models along the Hubble sequence and calibrate evolutionary equations to the results of direct N-body simulations of star clusters in order to predict the clusters' mass evolution as function of the galactic environment. We finally apply our methods to explore the properties of evolved `universal' initial cluster mass functions and any dependence on the host galaxy morphology and mass distribution. The preliminary results show that an initial power-law distribution of the masses `universally' evolves into a lognormal distribution, with the properties correlated with the stellar mass and stellar mass density of the host galaxy.

  17. Modelled air pollution levels versus EC air quality legislation - results from high resolution simulation.

    PubMed

    Chervenkov, Hristo

    2013-12-01

    An appropriate method for evaluating the air quality of a certain area is to contrast the actual air pollution levels to the critical ones, prescribed in the legislative standards. The application of numerical simulation models for assessing the real air quality status is allowed by the legislation of the European Community (EC). This approach is preferable, especially when the area of interest is relatively big and/or the network of measurement stations is sparse, and the available observational data are scarce, respectively. Such method is very efficient for similar assessment studies due to continuous spatio-temporal coverage of the obtained results. In the study the values of the concentration of the harmful substances sulphur dioxide, (SO2), nitrogen dioxide (NO2), particulate matter - coarse (PM10) and fine (PM2.5) fraction, ozone (O3), carbon monoxide (CO) and ammonia (NH3) in the surface layer obtained from modelling simulations with resolution 10 km on hourly bases are taken to calculate the necessary statistical quantities which are used for comparison with the corresponding critical levels, prescribed in the EC directives. For part of them (PM2.5, CO and NH3) this is done for first time with such resolution. The computational grid covers Bulgaria entirely and some surrounding territories and the calculations are made for every year in the period 1991-2000. The averaged over the whole time slice results can be treated as representative for the air quality situation of the last decade of the former century.

  18. Newest Results from the Investigation of Polymer-Induced Drag Reduction through Direct Numerical Simulation

    NASA Astrophysics Data System (ADS)

    Dimitropoulos, Costas D.; Beris, Antony N.; Sureshkumar, R.; Handler, Robert A.

    1998-11-01

    This work continues our attempts to elucidate theoretically the mechanism of polymer-induced drag reduction through direct numerical simulations of turbulent channel flow, using an independently evaluated rheological model for the polymer stress. Using appropriate scaling to accommodate effects due to viscoelasticity reveals that there exists a great consistency in the results for different combinations of the polymer concentration and chain extension. This helps demonstrate that our obervations are applicable to very dilute systems, currently not possible to simulate. It also reinforces the hypothesis that one of the prerequisites for the phenomenon of drag reduction is sufficiently enhanced extensional viscosity, corresponding to the level of intensity and duration of extensional rates typically encountered during the turbulent flow. Moreover, these results motivate a study of the turbulence structure at larger Reynolds numbers and for different periodic computational cell sizes. In addition, the Reynolds stress budgets demonstrate that flow elasticity adversely affects the activities represented by the pressure-strain correlations, leading to a redistribution of turbulent kinetic energy amongst all directions. Finally, we discuss the influence of viscoelasticity in reducing the production of streamwise vorticity.

  19. Natural frequencies of two bubbles in a compliant tube: analytical, simulation, and experimental results.

    PubMed

    Jang, Neo W; Zakrzewski, Aaron; Rossi, Christina; Dalecki, Diane; Gracewski, Sheryl

    2011-11-01

    Motivated by various clinical applications of ultrasound contrast agents within blood vessels, the natural frequencies of two bubbles in a compliant tube are studied analytically, numerically, and experimentally. A lumped parameter model for a five degree of freedom system was developed, accounting for the compliance of the tube and coupled response of the two bubbles. The results were compared to those produced by two different simulation methods: (1) an axisymmetric coupled boundary element and finite element code previously used to investigate the response of a single bubble in a compliant tube and (2) finite element models developed in comsol Multiphysics. For the simplified case of two bubbles in a rigid tube, the lumped parameter model predicts two frequencies for in- and out-of-phase oscillations, in good agreement with both numerical simulation and experimental results. For two bubbles in a compliant tube, the lumped parameter model predicts four nonzero frequencies, each asymptotically converging to expected values in the rigid and compliant limits of the tube material.

  20. Ion equation of state in quasi-parallel shocks - A simulation result

    NASA Technical Reports Server (NTRS)

    Mandt, M. E.; Kan, J. R.

    1988-01-01

    Ion equation of state in the quasi-parallel collisionless shock is deduced from simulation results. The simulations were performed for theta(bn) = 10 deg, beta = 0.5 and M sub A in the range from 1.2 to 8, where M sub A is the Alfven Mach number, beta is the upstream ratio of plasma pressure to magnetic pressure, and theta(bn) is the angle between the shock normal and the upstream magnetic field. The equation of state can be approximated by a power law with different exponents in the upstream and downstream sides of the shock transition region. The exponent in the upstream side of the transition region is much greater than the adiabatic value of 5/3 and increases with M sub A. The exponent in the downstream side of the transition region is slightly less than 5/3. The results show that ion heating in the quasi-parallel shock is highly nonadiabatic with a large increase in entropy and in temperature ratio in the upstream side of the transition region, while the heating is highly isentropic with a large increase in temperature difference across the principal density jump in the downstream side of the transition region.

  1. Ion cyclotron instability at Io: Hybrid simulation results compared to in situ observations

    NASA Astrophysics Data System (ADS)

    Šebek, Ondřej; Trávníček, Pavel M.; Walker, Raymond J.; Hellinger, Petr

    2016-08-01

    We present analysis of global three-dimensional hybrid simulations of Io's interaction with Jovian magnetospheric plasma. We apply a single-species model with simplified neutral-plasma chemistry and downscale Io in order to resolve the ion kinetic scales. We consider charge exchange, electron impact ionization, and photoionization by using variable rates of these processes to investigate their impact. Our results are in a good qualitative agreement with the in situ magnetic field measurements for five Galileo flybys around Io. The hybrid model describes ion kinetics self-consistently. This allows us to assess the distribution of temperature anisotropies around Io and thereby determine the possible triggering mechanism for waves observed near Io. We compare simulated dynamic spectra of magnetic fluctuations with in situ observations made by Galileo. Our results are consistent with both the spatial distribution and local amplitude of magnetic fluctuations found in the observations. Cyclotron waves, triggered probably by the growth of ion cyclotron instability, are observed mainly downstream of Io and on the flanks in regions farther from Io where the ion pickup rate is relatively low. Growth of the ion cyclotron instability is governed mainly by the charge exchange rate.

  2. Mercury's plasma belt: hybrid simulations results compared to in-situ measurements

    NASA Astrophysics Data System (ADS)

    Hercik, D.; Travnicek, P. M.; Schriver, D.; Hellinger, P.

    2012-12-01

    The presence of plasma belt and trapped particles region in the Mercury's inner magnetosphere has been questionable due to small dimensions of the magnetosphere of Mercury compared to Earth, where these regions are formed. Numerical simulations of the solar wind interaction with Mercury's magnetic field suggested that such a structure could be found also in the vicinity of Mercury. These results has been recently confirmed also by MESSENGER observations. Here we present more detailed analysis of the plasma belt structure and quasi-trapped particle population characteristics and behaviour under different orientations of the interplanetary magnetic field.The plasma belt region is constantly supplied with solar wind protons via magnetospheric flanks and tail current sheet region. Protons inside the plasma belt region are quasi-trapped in the magnetic field of Mercury and perform westward drift along the planet. This region is well separated by a magnetic shell and has higher average temperatures and lower bulk proton current densities than surrounding area. On the day side the population exhibits loss cone distribution function matching the theoretical loss cone angle. Simulations results are also compared to in-situ measurements acquired by MESSENGER MAG and FIPS instruments.

  3. Quantifying chain reptation in entangled polymer melts: topological and dynamical mapping of atomistic simulation results onto the tube model.

    PubMed

    Stephanou, Pavlos S; Baig, Chunggi; Tsolou, Georgia; Mavrantzas, Vlasis G; Kröger, Martin

    2010-03-28

    The topological state of entangled polymers has been analyzed recently in terms of primitive paths which allowed obtaining reliable predictions of the static (statistical) properties of the underlying entanglement network for a number of polymer melts. Through a systematic methodology that first maps atomistic molecular dynamics (MD) trajectories onto time trajectories of primitive chains and then documents primitive chain motion in terms of a curvilinear diffusion in a tubelike region around the coarse-grained chain contour, we are extending these static approaches here even further by computing the most fundamental function of the reptation theory, namely, the probability psi(s,t) that a segment s of the primitive chain remains inside the initial tube after time t, accounting directly for contour length fluctuations and constraint release. The effective diameter of the tube is independently evaluated by observing tube constraints either on atomistic displacements or on the displacement of primitive chain segments orthogonal to the initial primitive path. Having computed the tube diameter, the tube itself around each primitive path is constructed by visiting each entanglement strand along the primitive path one after the other and approximating it by the space of a small cylinder having the same axis as the entanglement strand itself and a diameter equal to the estimated effective tube diameter. Reptation of the primitive chain longitudinally inside the effective constraining tube as well as local transverse fluctuations of the chain driven mainly from constraint release and regeneration mechanisms are evident in the simulation results; the latter causes parts of the chains to venture outside their average tube surface for certain periods of time. The computed psi(s,t) curves account directly for both of these phenomena, as well as for contour length fluctuations, since all of them are automatically captured in the atomistic simulations. Linear viscoelastic

  4. Can Wing Tip Vortices Be Accurately Simulated?

    DTIC Science & Technology

    2011-07-01

    additional tail buffeting.2 In commercial applications, winglets have been installed on passenger aircraft to minimize vortex formation and reduce lift...air. In military applications, wing tip In commercial applications, winglets have been installed on passenger aircraft to minimize increases with downstream distances.

  5. Can Wing Tip Vortices Be Accurately Simulated?

    DTIC Science & Technology

    2011-07-01

    additional tail buffeting.2 In commercial applications, winglets have been installed on passenger aircraft to minimize vortex formation and reduce lift...towed vehicles and cause additional tail buffeting (Ref 2). In commercial applications, winglets have been installed on passenger aircraft to

  6. Statistically accurate simulations for atmospheric flows

    NASA Astrophysics Data System (ADS)

    Dubinkina, S.

    2009-04-01

    A Hamiltonian particle-mesh method for quasi-geostrophic potential vorticity flow is proposed. The microscopic vorticity field at any time is an area- and energy-conserving rearrangement of the initial field. We construct a statistical mechanics theory to explain the long-time behavior of the numerical solution. The statistical theory correctly predicts the spatial distribution of particles as a function of their point vorticity. A nonlinear relation between the coarse grained mean stream function and mean vorticity fields is predicted, consistent with the preservation of higher moments of potential vorticity reported in [R. V. Abramov, A. J. Majda 2003, PNAS 100 3841--3846].

  7. Optimal design of clinical trials with computer simulation based on results of earlier trials, illustrated with a lipodystrophy trial in HIV patients.

    PubMed

    Abbas, Ismail; Rovira, Joan; Casanovas, Josep; Greenfield, Tony

    2008-12-01

    The designer of a clinical trial needs to make many assumptions about real-life practice based on prior knowledge. Simulation allows us to learn from experience by using the information obtained from a trial to improve the original estimators of population parameters. We propose using data from a previous trial to formulate assumptions that can be used to simulate trials and thus improve the design of new trials. To demonstrate our method, we used data from a real clinical trial which had been designed to evaluate cholesterol level changes as a surrogate marker for lipodystrophy in HIV patients. We were able to identify the optimal design that would have minimised the cost of a trial subject to a statistical power constraint which could then be used to design a new trial. In particular, we focused on three factors: the distribution of cholesterol levels in HIV patients, trial recruitment rates and trial dropout rates. We were able to verify our hypothesis that the total cost resulting from carrying out a clinical trial can be minimised by applying simulation models as an alternative to conventional approaches. In our findings the simulation model proved to be very intuitive and a useful method for testing the performance of investigators' assumptions and generating an optimal clinical trial design before being put into practice in the real world. In addition, we concluded that simulation models provide a more accurate determination of power than conventional approaches, thus minimising the total cost of clinical trials.

  8. Beam hardening artifacts in micro-computed tomography scanning can be reduced by X-ray beam filtration and the resulting images can be used to accurately measure BMD.

    PubMed

    Meganck, Jeffrey A; Kozloff, Kenneth M; Thornton, Michael M; Broski, Stephen M; Goldstein, Steven A

    2009-12-01

    Bone mineral density (BMD) measurements are critical in many research studies investigating skeletal integrity. For pre-clinical research, micro-computed tomography (microCT) has become an essential tool in these studies. However, the ability to measure the BMD directly from microCT images can be biased by artifacts, such as beam hardening, in the image. This three-part study was designed to understand how the image acquisition process can affect the resulting BMD measurements and to verify that the BMD measurements are accurate. In the first part of this study, the effect of beam hardening-induced cupping artifacts on BMD measurements was examined. In the second part of this study, the number of bones in the X-ray path and the sampling process during scanning was examined. In the third part of this study, microCT-based BMD measurements were compared with ash weights to verify the accuracy of the measurements. The results indicate that beam hardening artifacts of up to 32.6% can occur in sample sizes of interest in studies investigating mineralized tissue and affect mineral density measurements. Beam filtration can be used to minimize these artifacts. The results also indicate that, for murine femora, the scan setup can impact densitometry measurements for both cortical and trabecular bone and morphologic measurements of trabecular bone. Last, when a scan setup that minimized all of these artifacts was used, the microCT-based measurements correlated well with ash weight measurements (R(2)=0.983 when air was excluded), indicating that microCT can be an accurate tool for murine bone densitometry.

  9. Accurate numerical simulation of the far-field tsunami caused by the 2011 Tohoku earthquake, including the effects of Boussinesq dispersion, seawater density stratification, elastic loading, and gravitational potential change

    NASA Astrophysics Data System (ADS)

    Baba, Toshitaka; Allgeyer, Sebastien; Hossen, Jakir; Cummins, Phil R.; Tsushima, Hiroaki; Imai, Kentaro; Yamashita, Kei; Kato, Toshihiro

    2017-03-01

    In this study, we considered the accurate calculation of far-field tsunami waveforms by using the shallow water equations and accounting for the effects of Boussinesq dispersion, seawater density stratification, elastic loading, and gravitational potential change in a finite difference scheme. By comparing numerical simulations that included and excluded each of these effects with the observed waveforms of the 2011 Tohoku tsunami, we found that all of these effects are significant and resolvable in the far field by the current generation of deep ocean-bottom pressure gauges. Our calculations using previously published, high-resolution models of the 2011 Tohoku tsunami source exhibited excellent agreement with the observed waveforms to a degree that has previously been possible only with near-field or regional observations. We suggest that the ability to model far-field tsunamis with high accuracy has important implications for tsunami source and hazard studies.

  10. Carbon fiber composites inspection and defect characterization using active infrared thermography: numerical simulations and experimental results.

    PubMed

    Fernandes, Henrique; Zhang, Hai; Figueiredo, Alisson; Ibarra-Castanedo, Clemente; Guimarares, Gilmar; Maldague, Xavier

    2016-12-01

    Composite materials are widely used in the aeronautic industry. One of the reasons is because they have strength and stiffness comparable to metals, with the added advantage of significant weight reduction. Infrared thermography (IT) is a safe nondestructive testing technique that has a fast inspection rate. In active IT, an external heat source is used to stimulate the material being inspected in order to generate a thermal contrast between the feature of interest and the background. In this paper, carbon-fiber-reinforced polymers are inspected using IT. More specifically, carbon/PEEK (polyether ether ketone) laminates with square Kapton inserts of different sizes and at different depths are tested with three different IT techniques: pulsed thermography, vibrothermography, and line scan thermography. The finite element method is used to simulate the pulsed thermography experiment. Numerical results displayed a very good agreement with experimental results.

  11. Multipacting simulation and test results of BNL 704 MHz SRF gun

    SciTech Connect

    Xu W.; Belomestnykh, S.; Ben-Zvi, I.; Cullen, C. et al

    2012-05-20

    The BNL 704MHz SRF gun has a grooved choke joint to support the photo-cathode. Due to the distortion of grooves at the choke joint during the BCP for the choke joint, several multipacting barriers showed up when it was tested with Nb cathode stalk at JLab. We built a setup to use the spare large grain SRF cavity to test and condition the multipacting at BNL with various power sources up to 50kW. The test is carried out in three stages: testing the cavity performance without cathode, testing the cavity with the Nb cathode stalk that was used at Jlab, and testing the cavity with a copper cathode stalk that is based on the design for the SRF gun. This paper summarizes the results of multipacting simulation, and presents the large grain cavity test setup and the test results.

  12. Results of Simulated Galactic Cosmic Radiation (GCR) and Solar Particle Events (SPE) on Spectra Restraint Fabric

    NASA Technical Reports Server (NTRS)

    Peters, Benjamin; Hussain, Sarosh; Waller, Jess

    2017-01-01

    Spectra or similar Ultra-high-molecular-weight polyethylene (UHMWPE) fabric is the likely choice for future structural space suit restraint materials due to its high strength-to-weight ratio, abrasion resistance, and dimensional stability. During long duration space missions, space suits will be subjected to significant amounts of high-energy radiation from several different sources. To insure that pressure garment designs properly account for effects of radiation, it is important to characterize the mechanical changes to structural materials after they have been irradiated. White Sands Test Facility (WSFTF) collaborated with the Crew and Thermal Systems Division at the Johnson Space Center (JSC) to irradiate and test various space suit materials by examining their tensile properties through blunt probe puncture testing and single fiber tensile testing after the materials had been dosed at various levels of simulated GCR and SPE Iron and Proton beams at Brookhaven National Laboratories. The dosages were chosen based on a simulation developed by the Structural Engineering Division at JSC for the expected radiation dosages seen by space suit softgoods seen on a Mars reference mission. Spectra fabric tested in the effort saw equivalent dosages at 2x, 10x, and 20x the predicted dose as well as a simulated 50 year exposure to examine the range of effects on the material and examine whether any degradation due to GCR would be present if the suit softgoods were stored in deep space for a long period of time. This paper presents the results of this work and outlines the impact on space suit pressure garment design for long duration deep space missions.

  13. Free space optical communication flight mission: simulations and experimental results on ground level demonstrator

    NASA Astrophysics Data System (ADS)

    Mata Calvo, Ramon; Ferrero, Valter; Camatel, Stefano; Catalano, Valeria; Bonino, Luciana; Toselli, Italo

    2009-05-01

    In the context of the increasing demand in high-speed data link for scientific, planetary exploration and earth observation missions, the Italian Space Agency (ASI), involving Thales Alenia Space as prime, the Polytechnic of Turin and other Italian partners, is developing a program for feasibility demonstration of optical communication system with the goal of a prototype flight mission in the next future. We have designed and analyzed a ground level bidirectional Free Space Optical Communication (FSOC) Breadboard at 2.5Gbit/s working at 1550nm as an emulator of slant path link. The breadboard is full-working and we tested it back-toback, at 500m and 2.3km during one month. The distances were chosen in order to get an equivalent slant path cumulative turbulence in a ground level link. The measurements campaign was done during the day and the night time and under several weather conditions, from sunny, rainy or windy. So we could work under very different turbulence conditions from weak to strong turbulence. We measured the scintillation both, on-axis and off-axis by introducing known misalignments at the terminals, transmission losses at both path lengths and BER at both receivers. We present simulations results considering slant and ground level links, where we took into account the atmospheric effects; scintillation, beam spread, beam wander and fade probability, and comparing them with the ground level experimental results, we find a good agreement between them. Finally we discuss the results obtained in the experimentation and in the flight mission simulations in order to apply our experimental results in the next project phases.

  14. Use of WRF result as meteorological input to DNDC model for greenhouse gas flux simulation

    NASA Astrophysics Data System (ADS)

    Grosz, B.; Horváth, L.; Gyöngyösi, A. Z.; Weidinger, T.; Pintér, K.; Nagy, Z.; André, K.

    2015-12-01

    Continuous evolution of biogeochemical models developed in the past decades makes possible the more and more accurate estimation of trace and greenhouse gas fluxes of soils. Due to the detailed meteorological, soil, biological and chemical processes the modeled fluxes are getting closer and closer to the real values. For appropriate evaluation models need large amount of input data. In this paper we have investigated how to build an easily accessible meteorological input data source for biogeochemical models, as it is one of the most important input data sets that is either missing or difficult to get from meteorological networks. The DNDC ecological model was used for testing the WRF numerical weather prediction system as a potential data source. The reference dataset was built by numerical interpolation based on measured data. The average differences between the modeled output data using WRF and observed meteorological data in 2009 and 2010 are less than 3.98 ± 1.6; 8.68 ± 6.72 and 6.5 ± 2.17 per cent for CO2, N2O and CH4, respectively, for the test years. Generalization of the results for other regions is restricted, however this work encourages others to examine the applicability of WRF data instead of observed climate parameters.

  15. Role of dayside transients in a substorm process: Results from the global kinetic simulation Vlasiator

    NASA Astrophysics Data System (ADS)

    Palmroth, M.; Hoilijoki, S.; Pfau-Kempf, Y.; Hietala, H.; Nishimura, Y.; Angelopoulos, V.; Pulkkinen, T. I.; Ganse, U.; Hannuksela, O.; von Alfthan, S.; Battarbee, M. C.; Vainio, R. O.

    2015-12-01

    We investigate the dayside-nightside coupling of the magnetospheric dynamics in a global kinetic simulation displaying the entire magnetosphere. We use the newly developed Vlasiator (http://vlasiator.fmi.fi), which is the world's first global hybrid-Vlasov simulation modelling the ions as distribution functions, while electrons are treated as a charge-neutralising fluid. Here, we run Vlasiator in the 5-dimensional (5D) setup, where the ordinary space is presented in the 2D noon-midnight meridional plane, embedding in each grid cell the 3D velocity space. This approach combines the improved physical solution with fine resolution, allowing to investigate kinetic processes as a consequence of the global magnetospheric evolution. The simulation is during steady southward interplanetary magnetic field. We observe dayside reconnection and the resulting 2D representations of flux transfer events (FTE). FTE's move tailwards and distort the magnetopause, while the largest of them even modify the plasma sheet location. In the nightside, the plasma sheet shows bead-like density enhancements moving slowly earthward. The tailward side of the dipolar field stretches. Strong reconnection initiates first in the near-Earth region, forming a tailward-moving magnetic island that cannibalises other islands forming further down the tail, increasing the island's volume and complexity. After this, several reconnection lines are formed again in the near-Earth region, resulting in several magnetic islands. At first, none of the earthward moving islands reach the closed field region because just tailward of the dipolar region exists a relatively stable X-line, which is strong enough to push most of the magnetic islands tailward. However, finally one of the tailward X-lines is strong enough to overcome the X-line nearest to Earth, forming a strong surge into the dipolar field region as there is nothing anymore to hold back the propagation of the structure. We investigate this substorm

  16. Late Pop III Star Formation During the Epoch of Reionization: Results from the Renaissance Simulations

    NASA Astrophysics Data System (ADS)

    Xu, Hao; Norman, Michael L.; O'Shea, Brian W.; Wise, John H.

    2016-06-01

    We present results on the formation of Population III (Pop III) stars at redshift 7.6 from the Renaissance Simulations, a suite of extremely high-resolution and physics-rich radiation transport hydrodynamics cosmological adaptive-mesh refinement simulations of high-redshift galaxy formation performed on the Blue Waters supercomputer. In a survey volume of about 220 comoving Mpc3, we found 14 Pop III galaxies with recent star formation. The surprisingly late formation of Pop III stars is possible due to two factors: (i) the metal enrichment process is local and slow, leaving plenty of pristine gas to exist in the vast volume; and (ii) strong Lyman-Werner radiation from vigorous metal-enriched star formation in early galaxies suppresses Pop III formation in (“not so”) small primordial halos with mass less than ˜3 × 107 M ⊙. We quantify the properties of these Pop III galaxies and their Pop III star formation environments. We look for analogs to the recently discovered luminous Ly α emitter CR7, which has been interpreted as a Pop III star cluster within or near a metal-enriched star-forming galaxy. We find and discuss a system similar to this in some respects, however, the Pop III star cluster is far less massive and luminous than CR7 is inferred to be.

  17. The Geoengineering Model Intercomparison Project Phase 6 (GeoMIP6): simulation design and preliminary results

    NASA Astrophysics Data System (ADS)

    Kravitz, B.; Robock, A.; Tilmes, S.; Boucher, O.; English, J. M.; Irvine, P. J.; Jones, A.; Lawrence, M. G.; MacCracken, M.; Muri, H.; Moore, J. C.; Niemeier, U.; Phipps, S. J.; Sillmann, J.; Storelvmo, T.; Wang, H.; Watanabe, S.

    2015-06-01

    We present a suite of new climate model experiment designs for the Geoengineering Model Intercomparison Project (GeoMIP). This set of experiments, named GeoMIP6 (to be consistent with the Coupled Model Intercomparison Project Phase 6), builds on the previous GeoMIP simulations, and has been expanded to address several further important topics, including key uncertainties in extreme events, the use of geoengineering as part of a portfolio of responses to climate change, and the relatively new idea of cirrus cloud thinning to allow more longwave radiation to escape to space. We discuss experiment designs, as well as the rationale for those designs, showing preliminary results from individual models when available. We also introduce a new feature, called the GeoMIP Testbed, which provides a platform for simulations that will be performed with a few models and subsequently assessed to determine whether the proposed experiment designs will be adopted as core (Tier 1) GeoMIP experiments. This is meant to encourage various stakeholders to propose new targeted experiments that address their key open science questions, with the goal of making GeoMIP more relevant to a broader set of communities.

  18. The Geoengineering Model Intercomparison Project Phase 6 (GeoMIP6): simulation design and preliminary results

    NASA Astrophysics Data System (ADS)

    Kravitz, B.; Robock, A.; Tilmes, S.; Boucher, O.; English, J. M.; Irvine, P. J.; Jones, A.; Lawrence, M. G.; MacCracken, M.; Muri, H.; Moore, J. C.; Niemeier, U.; Phipps, S. J.; Sillmann, J.; Storelvmo, T.; Wang, H.; Watanabe, S.

    2015-10-01

    We present a suite of new climate model experiment designs for the Geoengineering Model Intercomparison Project (GeoMIP). This set of experiments, named GeoMIP6 (to be consistent with the Coupled Model Intercomparison Project Phase 6), builds on the previous GeoMIP project simulations, and has been expanded to address several further important topics, including key uncertainties in extreme events, the use of geoengineering as part of a portfolio of responses to climate change, and the relatively new idea of cirrus cloud thinning to allow more longwave radiation to escape to space. We discuss experiment designs, as well as the rationale for those designs, showing preliminary results from individual models when available. We also introduce a new feature, called the GeoMIP Testbed, which provides a platform for simulations that will be performed with a few models and subsequently assessed to determine whether the proposed experiment designs will be adopted as core (Tier 1) GeoMIP experiments. This is meant to encourage various stakeholders to propose new targeted experiments that address their key open science questions, with the goal of making GeoMIP more relevant to a broader set of communities.

  19. Control of Warm Compression Stations Using Model Predictive Control: Simulation and Experimental Results

    NASA Astrophysics Data System (ADS)

    Bonne, F.; Alamir, M.; Bonnay, P.

    2017-02-01

    This paper deals with multivariable constrained model predictive control for Warm Compression Stations (WCS). WCSs are subject to numerous constraints (limits on pressures, actuators) that need to be satisfied using appropriate algorithms. The strategy is to replace all the PID loops controlling the WCS with an optimally designed model-based multivariable loop. This new strategy leads to high stability and fast disturbance rejection such as those induced by a turbine or a compressor stop, a key-aspect in the case of large scale cryogenic refrigeration. The proposed control scheme can be used to achieve precise control of pressures in normal operation or to avoid reaching stopping criteria (such as excessive pressures) under high disturbances (such as a pulsed heat load expected to take place in future fusion reactors, expected in the cryogenic cooling systems of the International Thermonuclear Experimental Reactor ITER or the Japan Torus-60 Super Advanced fusion experiment JT-60SA). The paper details the simulator used to validate this new control scheme and the associated simulation results on the SBTs WCS. This work is partially supported through the French National Research Agency (ANR), task agreement ANR-13-SEED-0005.

  20. Simulated flight through JAWS wind shear - In-depth analysis results. [Joint Airport Weather Studies

    NASA Technical Reports Server (NTRS)

    Frost, W.; Chang, H.-P.; Elmore, K. L.; Mccarthy, J.

    1984-01-01

    The Joint Airport Weather Studies (JAWS) field experiment was carried out in 1982 near Denver. An analysis is presented of aircraft performance in the three-dimensional wind fields. The fourth dimension, time, is not considered. The analysis seeks to prepare computer models of microburst wind shear from the JAWS data sets for input to flight simulators and for research and development of aircraft control systems and operational procedures. A description is given of the data set and the method of interpolating velocities and velocity gradients for input to the six-degrees-of-freedom equations governing the motion of the aircraft. The results of the aircraft performance analysis are then presented, and the interpretation classifies the regions of shear as severe, moderate, or weak. Paths through the severe microburst of August 5, 1982, are then recommended for training and operational applications. Selected subregions of the flow field defined in terms of planar sections through the wind field are presented for application to simulators with limited computer storage capacity, that is, for computers incapable of storing the entire array of variables needed if the complete wind field is programmed.

  1. The Formation of Asteroid Satellites in Catastrophic Impacts: Results from Numerical Simulations

    NASA Technical Reports Server (NTRS)

    Durda, D. D.; Bottke, W. F., Jr.; Enke, B. L.; Asphaug, E.; Richardson, D. C.; Leinhardt, Z. M.

    2003-01-01

    We have performed new simulations of the formation of asteroid satellites by collisions, using a combination of hydrodynamical and gravitational dynamical codes. This initial work shows that both small satellites and ejected, co-orbiting pairs are produced most favorably by moderate-energy collisions at more direct, rather than oblique, impact angles. Simulations so far seem to be able to produce systems qualitatively similar to known binaries. Asteroid satellites provide vital clues that can help us understand the physics of hypervelocity impacts, the dominant geologic process affecting large main belt asteroids. Moreover, models of satellite formation may provide constraints on the internal structures of asteroids beyond those possible from observations of satellite orbital properties alone. It is probable that most observed main-belt asteroid satellites are by-products of cratering and/or catastrophic disruption events. Several possible formation mechanisms related to collisions have been identified: (i) mutual capture following catastrophic disruption, (ii) rotational fission due to glancing impact and spin-up, and (iii) re-accretion in orbit of ejecta from large, non-catastrophic impacts. Here we present results from a systematic investigation directed toward mapping out the parameter space of the first and third of these three collisional mechanisms.

  2. The Geoengineering Model Intercomparison Project Phase 6 (GeoMIP6): Simulation design and preliminary results

    DOE PAGES

    Kravitz, Benjamin S.; Robock, Alan; Tilmes, S.; ...

    2015-10-27

    We present a suite of new climate model experiment designs for the Geoengineering Model Intercomparison Project (GeoMIP). This set of experiments, named GeoMIP6 (to be consistent with the Coupled Model Intercomparison Project Phase 6), builds on the previous GeoMIP project simulations, and has been expanded to address several further important topics, including key uncertainties in extreme events, the use of geoengineering as part of a portfolio of responses to climate change, and the relatively new idea of cirrus cloud thinning to allow more long wave radiation to escape to space. We discuss experiment designs, as well as the rationale formore » those designs, showing preliminary results from individual models when available. We also introduce a new feature, called the GeoMIP Testbed, which provides a platform for simulations that will be performed with a few models and subsequently assessed to determine whether the proposed experiment designs will be adopted as core (Tier 1) GeoMIP experiments. In conclusion, this is meant to encourage various stakeholders to propose new targeted experiments that address their key open science questions, with the goal of making GeoMIP more relevant to a broader set of communities.« less

  3. The Geoengineering Model Intercomparison Project Phase 6 (GeoMIP6): Simulation design and preliminary results

    SciTech Connect

    Kravitz, Benjamin S.; Robock, Alan; Tilmes, S.; Boucher, Olivier; English, J. M.; Irvine, Peter J.; Jones, Andrew; Lawrence, M. G.; MacCracken, Michael C.; Muri, Helene O.; Moore, John C.; Niemeier, Ulrike; Phipps, Steven J.; Sillmann, Jana; Storelvmo, Trude; Wang, Hailong; Watanabe, Shingo

    2015-10-27

    We present a suite of new climate model experiment designs for the Geoengineering Model Intercomparison Project (GeoMIP). This set of experiments, named GeoMIP6 (to be consistent with the Coupled Model Intercomparison Project Phase 6), builds on the previous GeoMIP project simulations, and has been expanded to address several further important topics, including key uncertainties in extreme events, the use of geoengineering as part of a portfolio of responses to climate change, and the relatively new idea of cirrus cloud thinning to allow more long wave radiation to escape to space. We discuss experiment designs, as well as the rationale for those designs, showing preliminary results from individual models when available. We also introduce a new feature, called the GeoMIP Testbed, which provides a platform for simulations that will be performed with a few models and subsequently assessed to determine whether the proposed experiment designs will be adopted as core (Tier 1) GeoMIP experiments. In conclusion, this is meant to encourage various stakeholders to propose new targeted experiments that address their key open science questions, with the goal of making GeoMIP more relevant to a broader set of communities.

  4. Simulation of compact circumstellar shells around Type Ia supernovae and the resulting high-velocity features

    NASA Astrophysics Data System (ADS)

    Mulligan, Brian W.; Wheeler, J. Craig

    2017-01-01

    For Type Ia supernovae that are observed prior to B-band maximum (approximately 18-20 days after the explosion) Ca absorption features are observed at velocities of order 10,000 km/s faster than the typical photospheric features. These high velocity features weaken in the first couple of weeks, disappearing entirely by a week after B-band maximum. The source of this high velocity material is uncertain: it may be the result of interaction between the supernova and circumstellar material or may be the result of plumes or bullets of material ejected during the course of the explosion. We simulate interaction between a supernova and several compact circumstellar shells, located within 0.03 solar radii of the progenitor white dwarf and having masses of 0.02 solar masses or less. We use FLASH to perform hydrodynamic simulations of the system to determine the structure of the ejecta and shell components after the interaction, then use these results to generate synthetic spectra with 1 day cadence for the first 25 days after the explosion. We compare the evolution of the velocity and pseudo-equivalent width of the Ca near-infrared triplet features in the synthetic spectra to observed values, demonstrating that these models are consistent with observations. Additionally, we fit the observed spectra of SN 2011fe (Parrent 2012, Pereira 2013) prior to B-band maximum using these models and synthetic spectra and provide an estimate for Ca abundance within the circumstellar material with implications for the mechanism by which the white dwarf explodes.

  5. Biofilm formation and control in a simulated spacecraft water system - Two-year results

    NASA Technical Reports Server (NTRS)

    Schultz, John R.; Taylor, Robert D.; Flanagan, David T.; Carr, Sandra E.; Bruce, Rebekah J.; Svoboda, Judy V.; Huls, M. H.; Sauer, Richard L.; Pierson, Duane L.

    1991-01-01

    The ability of iodine to maintain microbial water quality in a simulated spacecraft water system is being studied. An iodine level of about 2.0 mg/L is maintained by passing ultrapure influent water through an iodinated ion exchange resin. Six liters are withdrawn daily and the chemical and microbial quality of the water is monitored regularly. Stainless steel coupons used to monitor biofilm formation are being analyzed by culture methods, epifluorescence microscopy, and scanning electron microscopy. Results from the first two years of operation show a single episode of high bacterial colony counts in the iodinated system. This growth was apparently controlled by replacing the iodinated ion exchange resin. Scanning electron microscopy indicates that the iodine has limited but not completely eliminated the formation of biofilm during the first two years of operation. Significant microbial contamination has been present continuously in a parallel noniodinated system since the third week of operation.

  6. Multiple Frequency Contrast Source Inversion Method for Vertical Electromagnetic Profiling: 2D Simulation Results and Analyses

    NASA Astrophysics Data System (ADS)

    Li, Jinghe; Song, Linping; Liu, Qing Huo

    2016-02-01

    A simultaneous multiple frequency contrast source inversion (CSI) method is applied to reconstructing hydrocarbon reservoir targets in a complex multilayered medium in two dimensions. It simulates the effects of a salt dome sedimentary formation in the context of reservoir monitoring. In this method, the stabilized biconjugate-gradient fast Fourier transform (BCGS-FFT) algorithm is applied as a fast solver for the 2D volume integral equation for the forward computation. The inversion technique with CSI combines the efficient FFT algorithm to speed up the matrix-vector multiplication and the stable convergence of the simultaneous multiple frequency CSI in the iteration process. As a result, this method is capable of making quantitative conductivity image reconstruction effectively for large-scale electromagnetic oil exploration problems, including the vertical electromagnetic profiling (VEP) survey investigated here. A number of numerical examples have been demonstrated to validate the effectiveness and capacity of the simultaneous multiple frequency CSI method for a limited array view in VEP.

  7. AeroMACS C-Band Interference Modeling and Simulation Results

    NASA Technical Reports Server (NTRS)

    Wilson, Jeffrey

    2010-01-01

    A new C-band (5091-5150 MHz) airport communications system designated as Aeronautical Mobile Airport Communications System (AeroMACS) is being planned under the Federal Aviation Administration s NextGen program. It is necessary to establish practical limits on AeroMACS transmission power from airports so that the threshold of interference into the Mobile Satellite Service (Globalstar) feeder uplinks is not exceeded. To help provide guidelines for these limits, interference models have been created with the commercial software Visualyse Professional. In this presentation, simulation results were shown for the aggregate interference power at low earth orbit from AeroMACS transmitters at each of up to 757 airports in the United States, Canada, Mexico, and the surrounding area. Both omni-directional and sectoral antenna configurations were modeled. Effects of antenna height, beamwidth, and tilt were presented.

  8. Statistics of interacting networks with extreme preferred degrees: Simulation results and theoretical approaches

    NASA Astrophysics Data System (ADS)

    Liu, Wenjia; Schmittmann, Beate; Zia, R. K. P.

    2012-02-01

    Network studies have played a central role for understanding many systems in nature - e.g., physical, biological, and social. So far, much of the focus has been the statistics of networks in isolation. Yet, many networks in the world are coupled to each other. Recently, we considered this issue, in the context of two interacting social networks. In particular, We studied networks with two different preferred degrees, modeling, say, introverts vs. extroverts, with a variety of ``rules for engagement.'' As a first step towards an analytically accessible theory, we restrict our attention to an ``extreme scenario'': The introverts prefer zero contacts while the extroverts like to befriend everyone in the society. In this ``maximally frustrated'' system, the degree distributions, as well as the statistics of cross-links (between the two groups), can depend sensitively on how a node (individual) creates/breaks its connections. The simulation results can be reasonably well understood in terms of an approximate theory.

  9. Using Classification and Regression Trees (CART) and random forests to analyze attrition: Results from two simulations.

    PubMed

    Hayes, Timothy; Usami, Satoshi; Jacobucci, Ross; McArdle, John J

    2015-12-01

    In this article, we describe a recent development in the analysis of attrition: using classification and regression trees (CART) and random forest methods to generate inverse sampling weights. These flexible machine learning techniques have the potential to capture complex nonlinear, interactive selection models, yet to our knowledge, their performance in the missing data analysis context has never been evaluated. To assess the potential benefits of these methods, we compare their performance with commonly employed multiple imputation and complete case techniques in 2 simulations. These initial results suggest that weights computed from pruned CART analyses performed well in terms of both bias and efficiency when compared with other methods. We discuss the implications of these findings for applied researchers.

  10. Test Results From a Direct Drive Gas Reactor Simulator Coupled to a Brayton Power Conversion Unit

    NASA Technical Reports Server (NTRS)

    Hervol, David S.; Briggs, Maxwell H.; Owen, Albert K.; Bragg-Sitton, Shannon M.

    2009-01-01

    The Brayton Power Conversion Unit (BPCU) located at NASA Glenn Research Center (GRC) in Cleveland, OH is a closed cycle system incorporating a turboaltemator, recuperator, and gas cooler connected by gas ducts to an external gas heater. For this series of tests, the BPCU was modified by replacing the gas heater with the Direct Drive Gas heater or DOG. The DOG uses electric resistance heaters to simulate a fast spectrum nuclear reactor similar to those proposed for space power applications. The combined system thermal transient behavior was the focus of these tests. The BPCU was operated at various steady state points. At each point it was subjected to transient changes involving shaft rotational speed or DOG electrical input. This paper outlines the changes made to the test unit and describes the testing that took place along with the test results.

  11. Barred Galaxy Photometry: Comparing results from the Cananea sample with N-body simulations

    NASA Astrophysics Data System (ADS)

    Athanassoula, E.; Gadotti, D. A.; Carrasco, L.; Bosma, A.; de Souza, R. E.; Recillas, E.

    2009-11-01

    We compare the results of the photometrical analysis of barred galaxies with those of a similar analysis from N-body simulations. The photometry is for a sample of nine barred galaxies observed in the J and K[s] bands with the CANICA near infrared (NIR) camera at the 2.1 m telescope of the Observatorio Astrofísico Guillermo Haro (OAGH) in Cananea, Sonora, Mexico. The comparison includes radial ellipticity profiles and surface brightness (density for the N-body galaxies) profiles along the bar major and minor axes. We find very good agreement, arguing that the exchange of angular momentum within the galaxy plays a determinant role in the evolution of barred galaxies.

  12. Experimental and simulation study results for video landmark acquisition and tracking technology

    NASA Technical Reports Server (NTRS)

    Schappell, R. T.; Tietz, J. C.; Thomas, H. M.; Lowrie, J. W.

    1979-01-01

    A synopsis of related Earth observation technology is provided and includes surface-feature tracking, generic feature classification and landmark identification, and navigation by multicolor correlation. With the advent of the Space Shuttle era, the NASA role takes on new significance in that one can now conceive of dedicated Earth resources missions. Space Shuttle also provides a unique test bed for evaluating advanced sensor technology like that described in this report. As a result of this type of rationale, the FILE OSTA-1 Shuttle experiment, which grew out of the Video Landmark Acquisition and Tracking (VILAT) activity, was developed and is described in this report along with the relevant tradeoffs. In addition, a synopsis of FILE computer simulation activity is included. This synopsis relates to future required capabilities such as landmark registration, reacquisition, and tracking.

  13. Results of field trials using the NPL simulated reactor neutron field facility.

    PubMed

    Taylor, G C; Thomas, D J; Bennett, A

    2007-01-01

    The NPL simulated reactor neutron field facility provides neutron spectra similar to those found in the environs of UK gas-cooled reactors. Neutrons are generated by irradiating a thick lithium-alloy target with monoenergetic protons between 2.5 and 3.5 MeV (depending on the desired spectrum), and then moderated by a 40-cm diameter sphere of heavy water. This represents an extremely soft workplace field, with a mean neutron energy of 25 keV and, more significantly, a mean fluence to ambient dose equivalent conversion coefficient of the order of 20 pSv cm(2), approximately 20 times lower than those of the ISO standard calibration sources (252)Cf and (241)Am-Be. Results of field trials are presented, including readings from neutron spectrometers, personal dosimeters (active and passive) and neutron area survey meters, and issues with beam monitoring are discussed.

  14. Results of Aging Tests of Vendor-Produced Blended Feed Simulant

    SciTech Connect

    Russell, Renee L.; Buchmiller, William C.; Cantrell, Kirk J.; Peterson, Reid A.; Rinehart, Donald E.

    2009-04-21

    The Hanford Tank Waste Treatment and Immobilization Plant (WTP) is procuring through Pacific Northwest National Laboratory (PNNL) a minimum of five 3,500 gallon batches of waste simulant for Phase 1 testing in the Pretreatment Engineering Platform (PEP). To make sure that the quality of the simulant is acceptable, the production method was scaled up starting from laboratory-prepared simulant through 15-gallon vendor prepared simulant and 250-gallon vendor prepared simulant before embarking on the production of the 3500-gallon simulant batch by the vendor. The 3500-gallon PEP simulant batches were packaged in 250-gallon high molecular weight polyethylene totes at NOAH Technologies. The simulant was stored in an environmentally controlled environment at NOAH Technologies within their warehouse before blending or shipping. For the 15-gallon, 250-gallon, and 3500-gallon batch 0, the simulant was shipped in ambient temperature trucks with shipment requiring nominally 3 days. The 3500-gallon batch 1 traveled in a 70-75°F temperature controlled truck. Typically the simulant was uploaded in a PEP receiving tank within 24-hours of receipt. The first uploading required longer with it stored outside. Physical and chemical characterization of the 250-gallon batch was necessary to determine the effect of aging on the simulant in transit from the vendor and in storage before its use in the PEP. Therefore, aging tests were conducted on the 250-gallon batch of the vendor-produced PEP blended feed simulant to identify and determine any changes to the physical characteristics of the simulant when in storage. The supernate was also chemically characterized. Four aging scenarios for the vendor-produced blended simulant were studied: 1) stored outside in a 250-gallon tote, 2) stored inside in a gallon plastic bottle, 3) stored inside in a well mixed 5-L tank, and 4) subject to extended temperature cycling under summer temperature conditions in a gallon plastic bottle. The following

  15. First results from ARTEMIS lunar wake crossing: observations and hybrid simulation

    NASA Astrophysics Data System (ADS)

    Plaschke, F.; Wiehle, S.; Angelopoulos, V.; Auster, H.; Georgescu, E.; Glassmeier, K.; Motschmann, U. M.; Sibeck, D. G.

    2010-12-01

    The Moon does not have an intrinsic magnetic field and its conductivity is not sufficient to facilitate the development of an induced magnetosphere. The interaction of the Moon with the unperturbed solar wind (SW) is, hence, dominated by the absorption of SW particles on its surface and the consequent generation of a lunar wake on the night side. The SW magnetic field is basically convected through the Moon; the pressure imbalance in lunar wake, however, accounts for a slight increase in magnetic pressure in the lunar wake center. The wake is slowly filled up with SW particles due to their thermal motion, which generates a magnetohydrodynamic (MHD) rarefaction wave propagating away from the wake in the SW frame of reference. Over the last 3 years the Time History of Events and Macroscale Interactions During Substorms (THEMIS) mission provided excellent data helping the scientific community in drawing a detailed picture of the physical processes associated with the development of substorms in the terrestrial magnetotail. Two of the five THEMIS spacecraft are currently being sent into stationary orbits around the Moon in a follow-up mission called Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon's Interaction with the Sun (ARTEMIS). The ARTEMIS P1 spacecraft (formerly THEMIS-B) has recently passed through the lunar wake in a flyby maneuver on February 13, 2010. We show first results of two hybrid code simulations with static and, for the first time, dynamically changing SW input. Adapted SW monitor data of the NASA OMNI database is used as input for the simulations. During the wake crossing the spin stabilized spacecraft P1 was in lunar shadow and, hence, its spin period cannot be determined from sun sensor data. Therefore, an eclipse-spin model is applied to bridge the gap of missing spin period data in order to recover vector measurements. A comparison of the simulation results with correctly despun magnetic field and particle measurements of

  16. Simulated microgravity inhibits the proliferation of K562 erythroleukemia cells but does not result in apoptosis

    NASA Astrophysics Data System (ADS)

    Yi, Zong-Chun; Xia, Bing; Xue, Ming; Zhang, Guang-Yao; Wang, Hong; Zhou, Hui-Min; Sun, Yan; Zhuang, Feng-Yuan

    2009-07-01

    Astronauts and experimental animals in space develop the anemia of space flight, but the underlying mechanisms are still unclear. In this study, the impact of simulated microgravity on proliferation, cell death, cell cycle progress and cytoskeleton of erythroid progenitor-like K562 leukemia cells was observed. K562 cells were cultured in NASA Rotary Cell Culture System (RCCS) that was used to simulate microgravity (at 15 rpm). After culture for 24 h, 48 h, 72 h, and 96 h, the cell densities cultured in RCCS were only 55.5%, 54.3%, 67.2% and 66.4% of the flask-cultured control cells, respectively. The percentages of trypan blue-stained dead cells and the percentages of apoptotic cells demonstrated no difference between RCCS-cultured cells and flask-cultured cells at every time points (from 12 h to 96 h). Compared with flask-cultured cells, RCCS culture induced an accumulation of cell number at S phase concomitant with a decrease at G0/G1 and G2/M phases at 12 h. But 12 h later (from 24 h to 60 h), the distribution of cell cycle phases in RCCS-cultured cells became no difference compared to flask-cultured cells. Consistent with the changes of cell cycle distribution, the levels of intercellular cyclins in RCCS-cultured cells changed at 12 h, including a decrease in cyclin A, and the increasing in cyclin B, D1 and E, and then (from 24 h to 36 h) began to restore to control levels. After RCCS culture for 12-36 h, the microfilaments showed uneven and clustered distribution, and the microtubules were highly disorganized. These results indicated that RCCS-simulated microgravity could induce a transient inhibition of proliferation, but not result in apoptosis, which could involve in the development of space flight anemia. K562 cells could be a useful model to research the effects of microgravity on differentiation and proliferation of hematopoietic cells.

  17. Recent Simulation Results on Ring Current Dynamics Using the Comprehensive Ring Current Model

    NASA Technical Reports Server (NTRS)

    Zheng, Yihua; Zaharia, Sorin G.; Lui, Anthony T. Y.; Fok, Mei-Ching

    2010-01-01

    Plasma sheet conditions and electromagnetic field configurations are both crucial in determining ring current evolution and connection to the ionosphere. In this presentation, we investigate how different conditions of plasma sheet distribution affect ring current properties. Results include comparative studies in 1) varying the radial distance of the plasma sheet boundary; 2) varying local time distribution of the source population; 3) varying the source spectra. Our results show that a source located farther away leads to a stronger ring current than a source that is closer to the Earth. Local time distribution of the source plays an important role in determining both the radial and azimuthal (local time) location of the ring current peak pressure. We found that post-midnight source locations generally lead to a stronger ring current. This finding is in agreement with Lavraud et al.. However, our results do not exhibit any simple dependence of the local time distribution of the peak ring current (within the lower energy range) on the local time distribution of the source, as suggested by Lavraud et al. [2008]. In addition, we will show how different specifications of the magnetic field in the simulation domain affect ring current dynamics in reference to the 20 November 2007 storm, which include initial results on coupling the CRCM with a three-dimensional (3-D) plasma force balance code to achieve self-consistency in the magnetic field.

  18. Research on an expert system for database operation of simulation-emulation math models. Volume 1, Phase 1: Results

    NASA Technical Reports Server (NTRS)

    Kawamura, K.; Beale, G. O.; Schaffer, J. D.; Hsieh, B. J.; Padalkar, S.; Rodriguez-Moscoso, J. J.

    1985-01-01

    The results of the first phase of Research on an Expert System for Database Operation of Simulation/Emulation Math Models, is described. Techniques from artificial intelligence (AI) were to bear on task domains of interest to NASA Marshall Space Flight Center. One such domain is simulation of spacecraft attitude control systems. Two related software systems were developed to and delivered to NASA. One was a generic simulation model for spacecraft attitude control, written in FORTRAN. The second was an expert system which understands the usage of a class of spacecraft attitude control simulation software and can assist the user in running the software. This NASA Expert Simulation System (NESS), written in LISP, contains general knowledge about digital simulation, specific knowledge about the simulation software, and self knowledge.

  19. Results.

    ERIC Educational Resources Information Center

    Zemsky, Robert; Shaman, Susan; Shapiro, Daniel B.

    2001-01-01

    Describes the Collegiate Results Instrument (CRI), which measures a range of collegiate outcomes for alumni 6 years after graduation. The CRI was designed to target alumni from institutions across market segments and assess their values, abilities, work skills, occupations, and pursuit of lifelong learning. (EV)

  20. Application of high resolution land use and land cover data for atmospheric modeling in the Houston-Galveston metropolitan area, Part I: Meteorological simulation results

    NASA Astrophysics Data System (ADS)

    Cheng, Fang-Yi; Byun, Daewon W.

    To predict atmospheric conditions in an urban environment, the land surface processes must be accurately described through the use of detailed land use (LU) and land cover (LC) data. Use of the U.S. Geological Survey (USGS) 25-category data, currently in the Fifth-generation Mesoscale Model (MM5), with the Noah land surface model (LSM) and MRF (medium-range forecast) planetary boundary layer (PBL) schemes resulted in the over-prediction of daytime temperatures in the Houston downtown area due to the inaccurate representation as a completely impervious surface. This bias could be corrected with the addition of canopy water in the urban areas from the evapotranspiration effects of urban vegetation. A more fundamental approach would be to utilize an LULC dataset that represents land surface features accurately. The Texas Forest Service (TFS) LULC dataset established with the LANDSAT satellite imagery correctly represents the Houston-Galveston-Brazoria (HGB) area as mixtures of urban, residential, grass, and forest LULC types. This paper describes how the Noah LSM and PBL schemes in the MM5 were modified to accommodate the TFS-LULC data. Comparisons with various meteorological measurements show that the MM5 simulation made with the high resolution LULC data improves the boundary layer mixing conditions and local wind patterns in the Houston Ship Channel, which is a critically important anthropogenic emission area affecting the HGB air pollution problems. In particular, when the synoptic flows are weak, the improved LULC data simulates the asymmetrically elongated Houston heat island convergence zone influencing the location of the afternoon Gulf of Mexico sea-breeze front and the Galveston Bay breeze flows. This paper is part I of a two-part study and focuses on the meteorological simulation. In part II, effects of using the different meteorological inputs on air quality simulations are discussed.

  1. Accurate monotone cubic interpolation

    NASA Technical Reports Server (NTRS)

    Huynh, Hung T.

    1991-01-01

    Monotone piecewise cubic interpolants are simple and effective. They are generally third-order accurate, except near strict local extrema where accuracy degenerates to second-order due to the monotonicity constraint. Algorithms for piecewise cubic interpolants, which preserve monotonicity as well as uniform third and fourth-order accuracy are presented. The gain of accuracy is obtained by relaxing the monotonicity constraint in a geometric framework in which the median function plays a crucial role.

  2. Elastodynamic analysis of a gear pump. Part II: Meshing phenomena and simulation results

    NASA Astrophysics Data System (ADS)

    Mucchi, E.; Dalpiaz, G.; Rivola, A.

    2010-10-01

    A non-linear lumped kineto-elastodynamic model for the prediction of the dynamic behaviour of external gear pumps is presented. It takes into account the most important phenomena involved in the operation of this kind of machines. Two main sources of noise and vibration can be considered: pressure and gear meshing. Fluid pressure distribution on gears, which is time-varying, is computed and included as a resultant external force and torque acting on the gears. Parametric excitations due to time-varying meshing stiffness, the tooth profile errors (obtained by a metrological analysis), the backlash effects between meshing teeth, the lubricant squeeze and the possibility of tooth contact on both lines of action were also included. Finally, the torsional stiffness and damping of the driving shaft and the non-linear behaviour of the hydrodynamic journal bearings were also taken into account. Model validation was carried out on the basis of experimental data concerning case accelerations and force reactions. The model can be used in order to analyse the pump dynamic behaviour and to identify the effects of modifications in design and operation parameters, in terms of vibration and dynamic forces. Part I is devoted to the calculation of the gear eccentricity in the steady-state condition as result of the balancing between mean pressure loads, mean meshing force and bearing reactions, while in Part II the meshing phenomena are fully explained and the main simulation results are presented.

  3. Free-Flight Test Results of Scale Models Simulating Viking Parachute/Lander Staging

    NASA Technical Reports Server (NTRS)

    Polutchko, Robert J.

    1973-01-01

    This report presents the results of Viking Aerothermodynamics Test D4-34.0. Motion picture coverage of a number of Scale model drop tests provides the data from which time-position characteristics as well as canopy shape and model system attitudes are measured. These data are processed to obtain the instantaneous drag during staging of a model simulating the Viking decelerator system during parachute staging at Mars. Through scaling laws derived prior to test (Appendix A and B) these results are used to predict such performance of the Viking decelerator parachute during staging at Mars. The tests were performed at the NASA/Kennedy Space Center (KSC) Vertical Assembly Building (VAB). Model assemblies were dropped 300 feet to a platform in High Bay No. 3. The data consist of an edited master film (negative) which is on permanent file in the NASA/LRC Library. Principal results of this investigation indicate that for Viking parachute staging at Mars: 1. Parachute staging separation distance is always positive and continuously increasing generally along the descent path. 2. At staging, the parachute drag coefficient is at least 55% of its prestage equilibrium value. One quarter minute later, it has recovered to its pre-stage value.

  4. Gas cooling in semi-analytic models and smoothed particle hydrodynamics simulations: are results consistent?

    NASA Astrophysics Data System (ADS)

    Saro, A.; De Lucia, G.; Borgani, S.; Dolag, K.

    2010-08-01

    We present a detailed comparison between the galaxy populations within a massive cluster, as predicted by hydrodynamical smoothed particle hydrodynamics (SPH) simulations and by a semi-analytic model (SAM) of galaxy formation. Both models include gas cooling and a simple prescription of star formation, which consists in transforming instantaneously any cold gas available into stars, while neglecting any source of energy feedback. This simplified comparison is thus not meant to be compared with observational data, but is aimed at understanding the level of agreement, at the stripped-down level considered, between two techniques that are widely used to model galaxy formation in a cosmological framework and which present complementary advantages and disadvantages. We find that, in general, galaxy populations from SAMs and SPH have similar statistical properties, in agreement with previous studies. However, when comparing galaxies on an object-by-object basis, we find a number of interesting differences: (i) the star formation histories of the brightest cluster galaxies (BCGs) from SAM and SPH models differ significantly, with the SPH BCG exhibiting a lower level of star formation activity at low redshift, and a more intense and shorter initial burst of star formation with respect to its SAM counterpart; (ii) while all stars associated with the BCG were formed in its progenitors in the SAM used here, this holds true only for half of the final BCG stellar mass in the SPH simulation, the remaining half being contributed by tidal stripping of stars from the diffuse stellar component associated with galaxies accreted on the cluster halo; (iii) SPH satellites can lose up to 90 per cent of their stellar mass at the time of accretion, due to tidal stripping, a process not included in the SAM used in this paper; (iv) in the SPH simulation, significant cooling occurs on the most massive satellite galaxies and this lasts for up to 1 Gyr after accretion. This physical process is

  5. Near-Infrared Spectroscopic Measurements of Calf Muscle during Walking at Simulated Reduced Gravity - Preliminary Results

    NASA Technical Reports Server (NTRS)

    Ellerby, Gwenn E. C.; Lee, Stuart M. C.; Stroud, Leah; Norcross, Jason; Gernhardt, Michael; Soller, Babs R.

    2008-01-01

    Consideration for lunar and planetary exploration space suit design can be enhanced by investigating the physiologic responses of individual muscles during locomotion in reduced gravity. Near-infrared spectroscopy (NIRS) provides a non-invasive method to study the physiology of individual muscles in ambulatory subjects during reduced gravity simulations. PURPOSE: To investigate calf muscle oxygen saturation (SmO2) and pH during reduced gravity walking at varying treadmill inclines and added mass conditions using NIRS. METHODS: Four male subjects aged 42.3 +/- 1.7 years (mean +/- SE) and weighing 77.9 +/- 2.4 kg walked at a moderate speed (3.2 +/- 0.2 km/h) on a treadmill at inclines of 0, 10, 20, and 30%. Unsuited subjects were attached to a partial gravity simulator which unloaded the subject to simulate body weight plus the additional weight of a space suit (121 kg) in lunar gravity (0.17G). Masses of 0, 11, 23, and 34 kg were added to the subject and then unloaded to maintain constant weight. Spectra were collected from the lateral gastrocnemius (LG), and SmO2 and pH were calculated using previously published methods (Yang et al. 2007 Optics Express ; Soller et al. 2008 J Appl Physiol). The effects of incline and added mass on SmO2 and pH were analyzed through repeated measures ANOVA. RESULTS: SmO2 and pH were both unchanged by added mass (p>0.05), so data from trials at the same incline were averaged. LG SmO2 decreased significantly with increasing incline (p=0.003) from 61.1 +/- 2.0% at 0% incline to 48.7 +/- 2.6% at 30% incline, while pH was unchanged by incline (p=0.12). CONCLUSION: Increasing the incline (and thus work performed) during walking causes the LG to extract more oxygen from the blood supply, presumably to support the increased metabolic cost of uphill walking. The lack of an effect of incline on pH may indicate that, while the intensity of exercise has increased, the LG has not reached a level of work above the anaerobic threshold. In these

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

    SciTech Connect

    Jackson, J A

    2006-02-27

    code, (5) description of the modeling code, (6) the results of a number of preliminary imaging simulations, and (7) recommendations for future Wolter designs and for further modeling studies.

  7. A rainfall simulation experiment on soil and water conservation measures - Undesirable results

    NASA Astrophysics Data System (ADS)

    Hösl, R.; Strauss, P.

    2012-04-01

    Sediment and nutrient inputs from agriculturally used land into surface waters are one of the main problems concerning surface water quality. On-site soil and water conservation measures are getting more and more popular throughout the last decades and a lot of research has been done within this issue. Numerous studies can be found about rainfall simulation experiments with different conservation measures tested like no till, mulching employing different types of soil cover, as well as sub soiling practices. Many studies document a more or less great success in preventing soil erosion and enhancing water quality by implementing no till and mulching techniques on farmland but few studies also indicate higher erosion rates with implementation of conservation tillage practices (Strauss et al., 2003). In May 2011 we conducted a field rainfall simulation experiment in Upper Austria to test 5 different maize cultivation techniques: no till with rough seedbed, no till with fine seedbed, mulching with disc harrow and rotary harrow, mulching with rotary harrow and conventional tillage using plough and rotary harrow. Rough seedbed refers to the seedbed preparation at planting of the cover crops. On every plot except on the conventionally managed one cover crops (a mix of Trifolium alexandrinum, Phacelia, Raphanus sativus and Herpestes) were sown in August 2010. All plots were rained three times with deionised water (<50 μS.cm-1) for one hour with 50mm.h-1 rainfall intensity. Surface runoff and soil erosion were measured. Additionally, soil cover by mulch was measured as well as soil texture, bulk density, penetration resistance, surface roughness and soil water content before and after the simulation. The simulation experiments took place about 2 weeks after seeding of maize in spring 2011. The most effective cultivation techniques for soil prevention expectedly proved to be the no till variants, mean erosion rate was about 0.1 kg.h-1, mean surface runoff was 29 l.h-1

  8. Democratic population decisions result in robust policy-gradient learning: a parametric study with GPU simulations.

    PubMed

    Richmond, Paul; Buesing, Lars; Giugliano, Michele; Vasilaki, Eleni

    2011-05-04

    High performance computing on the Graphics Processing Unit (GPU) is an emerging field driven by the promise of high computational power at a low cost. However, GPU programming is a non-trivial task and moreover architectural limitations raise the question of whether investing effort in this direction may be worthwhile. In this work, we use GPU programming to simulate a two-layer network of Integrate-and-Fire neurons with varying degrees of recurrent connectivity and investigate its ability to learn a simplified navigation task using a policy-gradient learning rule stemming from Reinforcement Learning. The purpose of this paper is twofold. First, we want to support the use of GPUs in the field of Computational Neuroscience. Second, using GPU computing power, we investigate the conditions under which the said architecture and learning rule demonstrate best performance. Our work indicates that networks featuring strong Mexican-Hat-shaped recurrent connections in the top layer, where decision making is governed by the formation of a stable activity bump in the neural population (a "non-democratic" mechanism), achieve mediocre learning results at best. In absence of recurrent connections, where all neurons "vote" independently ("democratic") for a decision via population vector readout, the task is generally learned better and more robustly. Our study would have been extremely difficult on a desktop computer without the use of GPU programming. We present the routines developed for this purpose and show that a speed improvement of 5x up to 42x is provided versus optimised Python code. The higher speed is achieved when we exploit the parallelism of the GPU in the search of learning parameters. This suggests that efficient GPU programming can significantly reduce the time needed for simulating networks of spiking neurons, particularly when multiple parameter configurations are investigated.

  9. Prediction Markets and Beliefs about Climate: Results from Agent-Based Simulations

    NASA Astrophysics Data System (ADS)

    Gilligan, J. M.; John, N. J.; van der Linden, M.

    2015-12-01

    Climate scientists have long been frustrated by persistent doubts a large portion of the public expresses toward the scientific consensus about anthropogenic global warming. The political and ideological polarization of this doubt led Vandenbergh, Raimi, and Gilligan [1] to propose that prediction markets for climate change might influence the opinions of those who mistrust the scientific community but do trust the power of markets.We have developed an agent-based simulation of a climate prediction market in which traders buy and sell future contracts that will pay off at some future year with a value that depends on the global average temperature at that time. The traders form a heterogeneous population with different ideological positions, different beliefs about anthropogenic global warming, and different degrees of risk aversion. We also vary characteristics of the market, including the topology of social networks among the traders, the number of traders, and the completeness of the market. Traders adjust their beliefs about climate according to the gains and losses they and other traders in their social network experience. This model predicts that if global temperature is predominantly driven by greenhouse gas concentrations, prediction markets will cause traders' beliefs to converge toward correctly accepting anthropogenic warming as real. This convergence is largely independent of the structure of the market and the characteristics of the population of traders. However, it may take considerable time for beliefs to converge. Conversely, if temperature does not depend on greenhouse gases, the model predicts that traders' beliefs will not converge. We will discuss the policy-relevance of these results and more generally, the use of agent-based market simulations for policy analysis regarding climate change, seasonal agricultural weather forecasts, and other applications.[1] MP Vandenbergh, KT Raimi, & JM Gilligan. UCLA Law Rev. 61, 1962 (2014).

  10. Initial quality performance results using a phantom to simulate chest computed radiography.

    PubMed

    Muhogora, Wilbroad; Padovani, Renato; Msaki, Peter

    2011-01-01

    The aim of this study was to develop a homemade phantom for quantitative quality control in chest computed radiography (CR). The phantom was constructed from copper, aluminium, and polymenthylmethacrylate (PMMA) plates as well as Styrofoam materials. Depending on combinations, the literature suggests that these materials can simulate the attenuation and scattering characteristics of lung, heart, and mediastinum. The lung, heart, and mediastinum regions were simulated by 10 mm x 10 mm x 0.5 mm, 10 mm x 10 mm x 0.5 mm and 10 mm x 10 mm x 1 mm copper plates, respectively. A test object of 100 mm x 100 mm and 0.2 mm thick copper was positioned to each region for CNR measurements. The phantom was exposed to x-rays generated by different tube potentials that covered settings in clinical use: 110-120 kVp (HVL=4.26-4.66 mm Al) at a source image distance (SID) of 180 cm. An approach similar to the recommended method in digital mammography was applied to determine the CNR values of phantom images produced by a Kodak CR 850A system with post-processing turned off. Subjective contrast-detail studies were also carried out by using images of Leeds TOR CDR test object acquired under similar exposure conditions as during CNR measurements. For clinical kVp conditions relevant to chest radiography, the CNR was highest over 90-100 kVp range. The CNR data correlated with the results of contrast detail observations. The values of clinical tube potentials at which CNR is the highest are regarded to be optimal kVp settings. The simplicity in phantom construction can offer easy implementation of related quality control program.

  11. Equations of State for Mixtures: Results from DFT Simulations of Xenon/Ethane Mixtures Compared to High Accuracy Validation Experiments on Z

    NASA Astrophysics Data System (ADS)

    Magyar, Rudolph

    2013-06-01

    We report a computational and validation study of equation of state (EOS) properties of liquid / dense plasma mixtures of xenon and ethane to explore and to illustrate the physics of the molecular scale mixing of light elements with heavy elements. Accurate EOS models are crucial to achieve high-fidelity hydrodynamics simulations of many high-energy-density phenomena such as inertial confinement fusion and strong shock waves. While the EOS is often tabulated for separate species, the equation of state for arbitrary mixtures is generally not available, requiring properties of the mixture to be approximated by combining physical properties of the pure systems. The main goal of this study is to access how accurate this approximation is under shock conditions. Density functional theory molecular dynamics (DFT-MD) at elevated-temperature and pressure is used to assess the thermodynamics of the xenon-ethane mixture. The simulations are unbiased as to elemental species and therefore provide comparable accuracy when describing total energies, pressures, and other physical properties of mixtures as they do for pure systems. In addition, we have performed shock compression experiments using the Sandia Z-accelerator on pure xenon, ethane, and various mixture ratios thereof. The Hugoniot results are compared to the DFT-MD results and the predictions of different rules for combing EOS tables. The DFT-based simulation results compare well with the experimental points, and it is found that a mixing rule based on pressure equilibration performs reliably well for the mixtures considered. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  12. Multiple Hypothesis Tracking (MHT) for Space Surveillance: Results and Simulation Studies

    NASA Astrophysics Data System (ADS)

    Singh, N.; Poore, A.; Sheaff, C.; Aristoff, J.; Jah, M.

    2013-09-01

    tracking performance compared to existing methods at a lower computational cost, especially for closely-spaced objects, in realistic multi-sensor multi-object tracking scenarios over multiple regimes of space. Specifically, we demonstrate that the prototype MHT system can accurately and efficiently process tens of thousands of UCTs and angles-only UCOs emanating from thousands of objects in LEO, GEO, MEO and HELO, many of which are closely-spaced, in real-time on a single laptop computer, thereby making it well-suited for large-scale breakup and tracking scenarios. This is possible in part because complexity reduction techniques are used to control the runtime of MHT without sacrificing accuracy. We assess the performance of MHT in relation to other tracking methods in multi-target, multi-sensor scenarios ranging from easy to difficult (i.e., widely-spaced objects to closely-spaced objects), using realistic physics and probabilities of detection less than one. In LEO, it is shown that the MHT system is able to address the challenges of processing breakups by analyzing multiple frames of data simultaneously in order to improve association decisions, reduce cross-tagging, and reduce unassociated UCTs. As a result, the multi-frame MHT system can establish orbits up to ten times faster than single-frame methods. Finally, it is shown that in GEO, MEO and HELO, the MHT system is able to address the challenges of processing angles-only optical observations by providing a unified multi-frame framework.

  13. Accurate torque-speed performance prediction for brushless dc motors

    NASA Astrophysics Data System (ADS)

    Gipper, Patrick D.

    Desirable characteristics of the brushless dc motor (BLDCM) have resulted in their application for electrohydrostatic (EH) and electromechanical (EM) actuation systems. But to effectively apply the BLDCM requires accurate prediction of performance. The minimum necessary performance characteristics are motor torque versus speed, peak and average supply current and efficiency. BLDCM nonlinear simulation software specifically adapted for torque-speed prediction is presented. The capability of the software to quickly and accurately predict performance has been verified on fractional to integral HP motor sizes, and is presented. Additionally, the capability of torque-speed prediction with commutation angle advance is demonstrated.

  14. Test Results of Level A Suits to Challenge by Chemical and Biological Warfare Agents and Simulants: Summary Report

    DTIC Science & Technology

    1998-06-01

    Agent Permeation of GB and HD Through 25-Mil Chemical Protective Glove 30 3.3 System Test (Aerosol Simulant) 3.3.1 System Test (Aerosol Simulant... Chemical Protective Glove GB Permeation 176 Appendix Q: Commander Brigade F91 Table Q - 3: Commander Brigade F91: System Test (Vapor Simulant) Results No...capability to protect in a chemical agent or biological agent environment. Each

  15. Petroleum Systems of South Kara Basin: 3D stratigraphic simulation and basin modeling results

    NASA Astrophysics Data System (ADS)

    Malysheva, S.; Vasilyev, V.; Verzhbitsky, V.; Ananyev, V.; Murzin, R.; Komissarov, D.; Kosenkova, N.; Roslov, Yu.

    2012-04-01

    Petroleum systems of South Kara Basin are still poorly studied and hydrocarbon resource estimates vary depending on geological models and understanding of the basin evolution. The main purpose of the regional studies of South Kara Basin was to produce a consistent model, which would be able to explain the existence of the fields discovered in the area as well as to determine the most favorable hydrocarbon accumulation zones in the study area for further exploration. In the study 3D stratigraphic simulation and basin modeling of South Kara Basin was carried out. The stratigraphic simulation results, along with geological, geophysical and geochemical data for the inland areas of Yamal and Gydan peninsulas and South Kara islands enabled to predict the lithological composition and distribution of source rocks, reservoirs and seals in the Kara Sea offshore area. Based on the basin modeling results hydrocarbon accumulations may occur in the reservoir facies of the wide stratigraphic range from Jurrasic to Cretaceous. The main source for the hydrocarbons, accumulated in the South Kara Basin Neocomian and Cenomanian reservoirs are the J3-K1 (the northward extension of Bazhenov Formation and its analogs of West Siberia), as well as J1 and probably J2 shales with predominantly marine type of kerogen (type II). Thermal and burial history restorations show that Lower Cretaceous (Aptian-Albian) sediments enriched with terrigenous organic matter (kerogen of type III) and containing coaly layers could not produce the hydrocarbon volumes to fill the giant Rusanovskoye and Leningradskoye gas-condensate fields as the K1 source rocks are not mature enough. The modeling results, in particular, suggest that the geologic conditions in the South Kara Basin are favorable for further discoveries of giant fields. Although gas accumulations are predominating in the basin, oil-and-gascondensate fields (not a pure oil fields though) with sufficient part of liquid hydrocarbons might be present

  16. Factors influencing the probability of an incident at a junction: results from an interactive driving simulator.

    PubMed

    Alexander, Jennifer; Barham, Philip; Black, Ian

    2002-11-01

    Using data generated from a fixed-base interactive driving simulator, which was used to evaluate a driver decision aid, a model is built to predict the probability of an incident (i.e. an accident or a 'near miss') occurring as a result of a right-turn across left-hand traffic at an unsignalised junction. This can be considered to be the product of two separate probabilities, the first being the probability that the gap between a pair of vehicles in the traffic stream is accepted, and the second the probability that the time needed to cross the on-coming stream of traffic causes the time-to-collision with the nearest vehicle in this traffic stream to be less than a second. The model is developed from the results of experimental trials involving a sample of drivers, the majority of whom were aged 60 years or older, in order to demonstrate the effect of various parameters on these probabilities. The parameters considered include the size of the gap between successive vehicles, vehicle characteristics such as size, colour and velocity, driver characteristics such as age and sex, and both daytime and night-time conditions.

  17. Results from simulated remote-handled transuranic waste experiments at the Waste Isolation Pilot Plant (WIPP)

    SciTech Connect

    Molecke, M A

    1992-01-01

    Multi-year, simulated remote-handled transuranic waste (RH TRU, nonradioactive) experiments are being conducted underground in the Waste Isolation Pilot-Plant (WIPP) facility. These experiments involve the near-reference (thermal and geometrical) testing of eight full size RH TRU test containers emplaced into horizontal, unlined rock salt boreholes. Half of the test emplacements are partially filled with bentonite/silica-sand backfill material. All test containers were electrically heated at about 115 W/each for three years, then raised to about 300 W/each for the remaining time. Each test borehole was instrumented with a selection of remote-reading thermocouples, pressure gages, borehole vertical-closure gages, and vertical and horizontal borehole-diameter closure gages. Each test emplacements was also periodically opened for visual inspections of brine intrusions and any interactions with waste package materials, materials sampling, manual closure measurements, and observations of borehole changes. Effects of heat on borehole closure rates and near-field materials (metals, backfill, rock salt, and intruding brine) interactions were closely monitored as a function of time. This paper summarizes results for the first five years of in situ test operation with supporting instrumentation and laboratory data and interpretations. Some details of RH TRU waste package materials, designs, and assorted underground test observations are also discussed. Based on the results, the tested RH TRU waste packages, materials, and emplacement geometry in unlined salt boreholes appear to be quite adequate for initial WIPP repository-phase operations.

  18. Correlations between visual test results and flying performance on the advanced simulator for pilot training (ASPT).

    PubMed

    Kruk, R; Regan, D; Beverley, K I; Longridge, T

    1981-08-01

    Looking for visual differences in pilots to account for differences in flying performance, we tested five groups of subjects: Air Force primary student jet pilots, graduating (T38 aircraft) students, Air Force pilot instructors, and two control groups made up of experienced nonpilot aircrew and nonflying civilians. This interim report compares 13 different visual test results with low-visibility landing performance on the Air Force Human Resources Laboratory ASPT simulator. Performance was assessed by the number of crashes and by the distance of the aircraft from the runway threshold at the time of the first visual flight correction. Our main finding was that, for student pilots, landing performance correlated with tracking performance for a target that changed size (as if moving in depth) and also with tracking performance for a target that moved sideways. On the other hand, landing performance correlated comparatively weakly with psychophysical thresholds for motion and contrast. For student pilots, several of the visual tests gave results that correlated with flying grades in T37 and T38 jet aircraft. Tracking tests clearly distinguished between the nonflying group and all the flying groups. On the other hand, visual threshold tests did not distinguish between nonflying and flying groups except for grating contrast, which distinguished between the nonflying group and the pilot instructors. The sideways-motion tracking task was sensitive enough to distinguish between the various flying groups.

  19. Simulation Results of the Huygens Probe Entry and Descent Trajectory Reconstruction Algorithm

    NASA Technical Reports Server (NTRS)

    Kazeminejad, B.; Atkinson, D. H.; Perez-Ayucar, M.

    2005-01-01

    Cassini/Huygens is a joint NASA/ESA mission to explore the Saturnian system. The ESA Huygens probe is scheduled to be released from the Cassini spacecraft on December 25, 2004, enter the atmosphere of Titan in January, 2005, and descend to Titan s surface using a sequence of different parachutes. To correctly interpret and correlate results from the probe science experiments and to provide a reference set of data for "ground-truthing" Orbiter remote sensing measurements, it is essential that the probe entry and descent trajectory reconstruction be performed as early as possible in the postflight data analysis phase. The Huygens Descent Trajectory Working Group (DTWG), a subgroup of the Huygens Science Working Team (HSWT), is responsible for developing a methodology and performing the entry and descent trajectory reconstruction. This paper provides an outline of the trajectory reconstruction methodology, preliminary probe trajectory retrieval test results using a simulated synthetic Huygens dataset developed by the Huygens Project Scientist Team at ESA/ESTEC, and a discussion of strategies for recovery from possible instrument failure.

  20. Results and Lessons Learned from Performance Testing of Humans in Spacesuits in Simulated Reduced Gravity

    NASA Technical Reports Server (NTRS)

    Chappell, Steven P.; Norcross, Jason R.; Gernhardt, Michael L.

    2009-01-01

    NASA's Constellation Program has plans to return to the Moon within the next 10 years. Although reaching the Moon during the Apollo Program was a remarkable human engineering achievement, fewer than 20 extravehicular activities (EVAs) were performed. Current projections indicate that the next lunar exploration program will require thousands of EVAs, which will require spacesuits that are better optimized for human performance. Limited mobility and dexterity, and the position of the center of gravity (CG) are a few of many features of the Apollo suit that required significant crew compensation to accomplish the objectives. Development of a new EVA suit system will ideally result in performance close to or better than that in shirtsleeves at 1 G, i.e., in "a suit that is a pleasure to work in, one that you would want to go out and explore in on your day off." Unlike the Shuttle program, in which only a fraction of the crew perform EVA, the Constellation program will require that all crewmembers be able to perform EVA. As a result, suits must be built to accommodate and optimize performance for a larger range of crew anthropometry, strength, and endurance. To address these concerns, NASA has begun a series of tests to better understand the factors affecting human performance and how to utilize various lunar gravity simulation environments available for testing.

  1. Simulation results of Pulse Shape Discrimination (PSD) for background reduction in INTEGRAL Spectrometer (SPI) germanium detectors

    NASA Technical Reports Server (NTRS)

    Slassi-Sennou, S. A.; Boggs, S. E.; Feffer, P. T.; Lin, R. P.

    1997-01-01

    Pulse Shape Discrimination (PSD) for background reduction will be used in the INTErnational Gamma Ray Astrophysics Laboratory (INTEGRAL) imaging spectrometer (SPI) to improve the sensitivity from 200 keV to 2 MeV. The observation of significant astrophysical gamma ray lines in this energy range is expected, where the dominant component of the background is the beta(sup -) decay in the Ge detectors due to the activation of Ge nuclei by cosmic rays. The sensitivity of the SPI will be improved by rejecting beta(sup -) decay events while retaining photon events. The PSD technique will distinguish between single and multiple site events. Simulation results of PSD for INTEGRAL-type Ge detectors using a numerical model for pulse shape generation are presented. The model was shown to agree with the experimental results for a narrow inner bore closed end cylindrical detector. Using PSD, a sensitivity improvement factor of the order of 2.4 at 0.8 MeV is expected.

  2. Benefits and costs of methadone treatment: results from a lifetime simulation model.

    PubMed

    Zarkin, Gary A; Dunlap, Laura J; Hicks, Katherine A; Mamo, Daniel

    2005-11-01

    Several studies have examined the benefits and costs of drug treatment; however, they have typically focused on the benefits and costs of a single treatment episode. Although beneficial for certain analyses, the results are limited because they implicitly treat drug abuse as an acute problem that can be treated in one episode. We developed a Monte Carlo simulation model that incorporates the chronic nature of drug abuse. Our model represents the progression of individuals from the general population aged 18-60 with respect to their heroin use, treatment for heroin use, criminal behavior, employment, and health care use. We also present three model scenarios representing an increase in the probability of going to treatment, an increase in the treatment length of stay, and a scenario in which drug treatment is not available to evaluate how changes in treatment parameters affect model results. We find that the benefit-cost ratio of treatment from our lifetime model (37.72) exceeds the benefit-cost ratio from a static model (4.86). The model provides a rich characterization of the dynamics of heroin use and captures the notion of heroin use as a chronic recurring condition. Similar models can be developed for other chronic diseases, such as diabetes, mental illness, or cardiovascular disease.

  3. LSP Simulation and Analytical Results on Electromagnetic Wave Scattering on Coherent Density Structures

    NASA Astrophysics Data System (ADS)

    Sotnikov, V.; Kim, T.; Lundberg, J.; Paraschiv, I.; Mehlhorn, T.

    2014-09-01

    The presence of plasma turbulence can strongly influence propagation properties of electromagnetic signals used for surveillance and communication. In particular, we are interested in the generation of low frequency plasma density irregularities in the form of coherent vortex structures. Interchange or flute type density irregularities in magnetized plasma are associated with Rayleigh-Taylor type instability. These types of density irregularities play important role in refraction and scattering of high frequency electromagnetic signals propagating in the earth ionosphere, in high energy density physics (HEDP) and in many other applications. We will discuss scattering of high frequency electromagnetic waves on low frequency density irregularities due to the presence of vortex density structures associated with interchange instability. We will also present PIC simulation results on EM scattering on vortex type density structures using the LSP code and compare them with analytical results. Acknowledgement: This work was supported by the Air Force Research laboratory, the Air Force Office of Scientific Research, the Naval Research Laboratory and NNSA/DOE grant no. DE-FC52-06NA27616 at the University of Nevada at Reno.

  4. A mathematical model and simulation results of plasma enhanced chemical vapor deposition of silicon nitride films

    NASA Astrophysics Data System (ADS)

    Konakov, S. A.; Krzhizhanovskaya, V. V.

    2015-01-01

    We developed a mathematical model of Plasma Enhanced Chemical Vapor Deposition (PECVD) of silicon nitride thin films from SiH4-NH3-N2-Ar mixture, an important application in modern materials science. Our multiphysics model describes gas dynamics, chemical physics, plasma physics and electrodynamics. The PECVD technology is inherently multiscale, from macroscale processes in the chemical reactor to atomic-scale surface chemistry. Our macroscale model is based on Navier-Stokes equations for a transient laminar flow of a compressible chemically reacting gas mixture, together with the mass transfer and energy balance equations, Poisson equation for electric potential, electrons and ions balance equations. The chemical kinetics model includes 24 species and 58 reactions: 37 in the gas phase and 21 on the surface. A deposition model consists of three stages: adsorption to the surface, diffusion along the surface and embedding of products into the substrate. A new model has been validated on experimental results obtained with the "Plasmalab System 100" reactor. We present the mathematical model and simulation results investigating the influence of flow rate and source gas proportion on silicon nitride film growth rate and chemical composition.

  5. [Implementation results of emission standards of air pollutants for thermal power plants: a numerical simulation].

    PubMed

    Wang, Zhan-Shan; Pan, Li-Bo

    2014-03-01

    The emission inventory of air pollutants from the thermal power plants in the year of 2010 was set up. Based on the inventory, the air quality of the prediction scenarios by implementation of both 2003-version emission standard and the new emission standard were simulated using Models-3/CMAQ. The concentrations of NO2, SO2, and PM2.5, and the deposition of nitrogen and sulfur in the year of 2015 and 2020 were predicted to investigate the regional air quality improvement by the new emission standard. The results showed that the new emission standard could effectively improve the air quality in China. Compared with the implementation results of the 2003-version emission standard, by 2015 and 2020, the area with NO2 concentration higher than the emission standard would be reduced by 53.9% and 55.2%, the area with SO2 concentration higher than the emission standard would be reduced by 40.0%, the area with nitrogen deposition higher than 1.0 t x km(-2) would be reduced by 75.4% and 77.9%, and the area with sulfur deposition higher than 1.6 t x km(-2) would be reduced by 37.1% and 34.3%, respectively.

  6. Intracranial hemorrhage alters scalp potential distribution in bioimpedance cerebral monitoring: Preliminary results from FEM simulation on a realistic head model and human subjects

    PubMed Central

    Atefi, Seyed Reza; Seoane, Fernando; Kamalian, Shervin; Rosenthal, Eric S.; Lev, Michael H.; Bonmassar, Giorgio

    2016-01-01

    Purpose: Current diagnostic neuroimaging for detection of intracranial hemorrhage (ICH) is limited to fixed scanners requiring patient transport and extensive infrastructure support. ICH diagnosis would therefore benefit from a portable diagnostic technology, such as electrical bioimpedance (EBI). Through simulations and patient observation, the authors assessed the influence of unilateral ICH hematomas on quasisymmetric scalp potential distributions in order to establish the feasibility of EBI technology as a potential tool for early diagnosis. Methods: Finite element method (FEM) simulations and experimental left–right hemispheric scalp potential differences of healthy and damaged brains were compared with respect to the asymmetry caused by ICH lesions on quasisymmetric scalp potential distributions. In numerical simulations, this asymmetry was measured at 25 kHz and visualized on the scalp as the normalized potential difference between the healthy and ICH damaged models. Proof-of-concept simulations were extended in a pilot study of experimental scalp potential measurements recorded between 0 and 50 kHz with the authors’ custom-made bioimpedance spectrometer. Mean left–right scalp potential differences recorded from the frontal, central, and parietal brain regions of ten healthy control and six patients suffering from acute/subacute ICH were compared. The observed differences were measured at the 5% level of significance using the two-sample Welch t-test. Results: The 3D-anatomically accurate FEM simulations showed that the normalized scalp potential difference between the damaged and healthy brain models is zero everywhere on the head surface, except in the vicinity of the lesion, where it can vary up to 5%. The authors’ preliminary experimental results also confirmed that the left–right scalp potential difference in patients with ICH (e.g., 64 mV) is significantly larger than in healthy subjects (e.g., 20.8 mV; P < 0.05). Conclusions: Realistic

  7. CSSC Fish Barrier Simulated Rescuer Touch Point Results, Operating Guidance, and Recommendations for Rescuer Safety

    DTIC Science & Technology

    2011-09-01

    Public September 2011 x This page intentionally left blank. CSSC Fish Barrier Simulated Rescuer Touch...electrode on the wet end (hook end) to simulate the PIW, and lashed it to the life ring to provide flotation during towing. The dry end was wrapped in foil

  8. Concepts and Results of New Method for Accurate Ground and In-Flight Calibration of the Particle Spectrometers of the Fast Plasma Investigation on NASA's Magnetospheric MultiScale Mission

    NASA Astrophysics Data System (ADS)

    Gliese, U.; Gershman, D. J.; Dorelli, J.; Avanov, L. A.; Barrie, A. C.; Clark, G. B.; Kujawski, J. T.; Mariano, A. J.; Coffey, V. N.; Tucker, C. J.; Chornay, D. J.; Cao, N. T.; Zeuch, M. A.; Dickson, C.; Smith, D. L.; Salo, C.; MacDonald, E.; Kreisler, S.; Jacques, A. D.; Giles, B. L.; Pollock, C. J.

    2015-12-01

    The Fast Plasma Investigation (FPI) on NASA's Magnetospheric MultiScale (MMS) mission employs 16 Dual Electron Spectrometers and 16 Dual Ion Spectrometers with 4 of each type on each of 4 spacecraft to enable fast (30 ms for electrons; 150 ms for ions) and spatially differentiated measurements of the full 3D particle velocity distributions. This approach presents a new and challenging aspect to the calibration and operation of these instruments on ground and in flight. The response uniformity, the reliability of their calibration and the approach to handling any temporal evolution of these calibrated characteristics all assume enhanced importance in this application, where we attempt to understand the meaning of particle distributions within the ion and electron diffusion regions of magnetically reconnecting plasmas. We have developed a detailed model of the spectrometer detection system, its behavior and its signal, crosstalk and noise sources. Based on this, we have devised a new calibration method that enables accurate and repeatable measurement of micro-channel plate (MCP) gain, signal loss due to variation in MCP gain and crosstalk effects in one single measurement. The foundational concepts of this new calibration method, named threshold scan, are presented. It is shown how this method has been successfully applied both on ground and in-flight to achieve highly accurate and precise calibration of all 64 spectrometers. Calibration parameters that will evolve in flight are determined daily providing a robust characterization of sensor suite performance, as a basis for both in-situ hardware adjustment and data processing to scientific units, throughout mission lifetime. This is shown to be very desirable as the instruments will produce higher quality raw science data that will require smaller post-acquisition data-corrections using results from in-flight derived pitch angle distribution measurements and ground calibration measurements. The practical application

  9. Simulation Framework for Rapid Entry, Descent, and Landing (EDL) Analysis, Phase 2 Results

    NASA Technical Reports Server (NTRS)

    Murri, Daniel G.

    2011-01-01

    The NASA Engineering and Safety Center (NESC) was requested to establish the Simulation Framework for Rapid Entry, Descent, and Landing (EDL) Analysis assessment, which involved development of an enhanced simulation architecture using the Program to Optimize Simulated Trajectories II simulation tool. The assessment was requested to enhance the capability of the Agency to provide rapid evaluation of EDL characteristics in systems analysis studies, preliminary design, mission development and execution, and time-critical assessments. Many of the new simulation framework capabilities were developed to support the Agency EDL-Systems Analysis (SA) team that is conducting studies of the technologies and architectures that are required to enable human and higher mass robotic missions to Mars. The findings, observations, and recommendations from the NESC are provided in this report.

  10. Feature Extraction from Simulations and Experiments: Preliminary Results Using a Fluid Mix Problem

    SciTech Connect

    Kamath, C; Nguyen, T

    2005-01-04

    Code validation, or comparing the output of computer simulations to experiments, is necessary to determine which simulation is a better approximation to an experiment. It can also be used to determine how the input parameters in a simulation can be modified to yield output that is closer to the experiment. In this report, we discuss our experiences in the use of image processing techniques for extracting features from 2-D simulations and experiments. These features can be used in comparing the output of simulations to experiments, or to other simulations. We first describe the problem domain and the data. We next explain the need for cleaning or denoising the experimental data and discuss the performance of different techniques. Finally, we discuss the features of interest and describe how they can be extracted from the data. The focus in this report is on extracting features from experimental and simulation data for the purpose of code validation; the actual interpretation of these features and their use in code validation is left to the domain experts.

  11. Chemical compatibility screening results of plastic packaging to mixed waste simulants

    SciTech Connect

    Nigrey, P.J.; Dickens, T.G.

    1995-12-01

    We have developed a chemical compatibility program for evaluating transportation packaging components for transporting mixed waste forms. We have performed the first phase of this experimental program to determine the effects of simulant mixed wastes on packaging materials. This effort involved the screening of 10 plastic materials in four liquid mixed waste simulants. The testing protocol involved exposing the respective materials to {approximately}3 kGy of gamma radiation followed by 14 day exposures to the waste simulants of 60 C. The seal materials or rubbers were tested using VTR (vapor transport rate) measurements while the liner materials were tested using specific gravity as a metric. For these tests, a screening criteria of {approximately}1 g/m{sup 2}/hr for VTR and a specific gravity change of 10% was used. It was concluded that while all seal materials passed exposure to the aqueous simulant mixed waste, EPDM and SBR had the lowest VTRs. In the chlorinated hydrocarbon simulant mixed waste, only VITON passed the screening tests. In both the simulant scintillation fluid mixed waste and the ketone mixture simulant mixed waste, none of the seal materials met the screening criteria. It is anticipated that those materials with the lowest VTRs will be evaluated in the comprehensive phase of the program. For specific gravity testing of liner materials the data showed that while all materials with the exception of polypropylene passed the screening criteria, Kel-F, HDPE, and XLPE were found to offer the greatest resistance to the combination of radiation and chemicals.

  12. Chemical and Mechanical Alteration of Fractures: Micro-Scale Simulations and Comparison to Experimental Results

    NASA Astrophysics Data System (ADS)

    Ameli, P.; Detwiler, R. L.; Elkhoury, J. E.; Morris, J. P.

    2012-12-01

    surfaces to shift away from the equilibrium location. We apply a relative rotation of the fracture surfaces to preserve force equilibrium during each iteration. The results of the model are compared with flow-through experiments conducted on fractured limestone cores and on analogue rough-surfaced KDP-glass fractures. The fracture apertures are mapped before, during (for some) and after the experiments. These detailed aperture measurements are used as input to our new coupled model. The experiments cover a wide range of transport and reaction conditions; some exhibit permeability increase due to channel formation and others exhibit fracture closure due to deformation of contacting asperities. Simulation results predict these general trends as well as the small-scale details in regions of contacting asperities.n example of an aperture field under chemical and mechanical alterations. The color scale is in microns.

  13. Personal values and crew compatibility: Results from a 105 days simulated space mission

    NASA Astrophysics Data System (ADS)

    Sandal, Gro M.; Bye, Hege H.; van de Vijver, Fons J. R.

    2011-08-01

    On a mission to Mars the crew will experience high autonomy and inter-dependence. "Groupthink", known as a tendency to strive for consensus at the cost of considering alternative courses of action, represents a potential safety hazard. This paper addresses two aspects of "groupthink": the extent to which confined crewmembers perceive increasing convergence in personal values, and whether they attribute less tension to individual differences over time. It further examines the impact of personal values for interpersonal compatibility. These questions were investigated in a 105-day confinement study in which a multinational crew ( N=6) simulated a Mars mission. The Portrait of Crew Values Questionnaire was administered regularly to assess personal values, perceived value homogeneity, and tension attributed to value disparities. Interviews were conducted before and after the confinement. Multiple regression analysis revealed no significant changes in value homogeneity over time; rather the opposite tendency was indicated. More tension was attributed to differences in hedonism, benevolence and tradition in the last 35 days when the crew was allowed greater autonomy. Three subgroups, distinct in terms of personal values, were identified. No evidence for "groupthink" was found. The results suggest that personal values should be considered in composition of crews for long duration missions.

  14. Optimal piezoelectric beam shape for single and broadband vibration energy harvesting: Modeling, simulation and experimental results

    NASA Astrophysics Data System (ADS)

    Muthalif, Asan G. A.; Nordin, N. H. Diyana

    2015-03-01

    Harvesting energy from the surroundings has become a new trend in saving our environment. Among the established ones are solar panels, wind turbines and hydroelectric generators which have successfully grown in meeting the world's energy demand. However, for low powered electronic devices; especially when being placed in a remote area, micro scale energy harvesting is preferable. One of the popular methods is via vibration energy scavenging which converts mechanical energy (from vibration) to electrical energy by the effect of coupling between mechanical variables and electric or magnetic fields. As the voltage generated greatly depends on the geometry and size of the piezoelectric material, there is a need to define an optimum shape and configuration of the piezoelectric energy scavenger. In this research, mathematical derivations for unimorph piezoelectric energy harvester are presented. Simulation is done using MATLAB and COMSOL Multiphysics software to study the effect of varying the length and shape of the beam to the generated voltage. Experimental results comparing triangular and rectangular shaped piezoelectric beam are also presented.

  15. Wide Bandpass and Narrow Bandstop Microstrip Filters based on Hilbert fractal geometry: design and simulation results.

    PubMed

    Mezaal, Yaqeen S; Eyyuboglu, Halil T; Ali, Jawad K

    2014-01-01

    This paper presents new Wide Bandpass Filter (WBPF) and Narrow Bandstop Filter (NBSF) incorporating two microstrip resonators, each resonator is based on 2nd iteration of Hilbert fractal geometry. The type of filter as pass or reject band has been adjusted by coupling gap parameter (d) between Hilbert resonators using a substrate with a dielectric constant of 10.8 and a thickness of 1.27 mm. Numerical simulation results as well as a parametric study of d parameter on filter type and frequency responses are presented and studied. WBPF has designed at resonant frequencies of 2 and 2.2 GHz with a bandwidth of 0.52 GHz, -28 dB return loss and -0.125 dB insertion loss while NBSF has designed for electrical specifications of 2.37 GHz center frequency, 20 MHz rejection bandwidth, -0.1873 dB return loss and 13.746 dB insertion loss. The proposed technique offers a new alternative to construct low-cost high-performance filter devices, suitable for a wide range of wireless communication systems.

  16. The relativity experiment of MORE: Global full-cycle simulation and results

    NASA Astrophysics Data System (ADS)

    Schettino, Giulia

    2015-07-01

    BepiColombo is a joint ESA/JAXA mission to Mercury with challenging objectives regarding geophysics, geodesy and fundamental physics. In particular, the Mercury Orbiter Radio science Experiment (MORE) intends, as one of its goals, to perform a test of General Relativity. This can be done by measuring and constraining the parametrized post-Newtonian (PPN) parameters to an accuracy significantly better than current one. In this work we perform a global numerical full-cycle simulation of the BepiColombo Radio Science Experiments (RSE) in a realistic scenario, focussing on the relativity experiment, solving simultaneously for all the parameters of interest for RSE in a global least squares fit within a constrained multiarc strategy. The results on the achievable accuracy for each PPN parameter will be presented and discussed, confirming the significant improvement to the actual knowledge of gravitation theory expected for the MORE relativity experiment. In particular, we will show that, including realistic systematic effects in the range observables, an accuracy of the order of 10-6 can still be achieved in the Eddington parameter β and in the parameter α1, which accounts for preferred frame effects, while the only poorly determined parameter turns out to be ζ, which describes the temporal variations of the gravitational constant and the Sun mass.

  17. Do tanning salons adhere to new legal regulations? Results of a simulated client trial in Germany.

    PubMed

    Möllers, Tobias; Pischke, Claudia R; Zeeb, Hajo

    2016-03-01

    In August 2009 and January 2012, two regulations were passed in Germany to limit UV exposure in the general population. These regulations state that no minors are allowed to use tanning devices. Personnel of tanning salons is mandated to offer counseling regarding individual skin type, to create a dosage plan with the customer and to provide a list describing harmful effects of UV radiation. Furthermore, a poster of warning criteria has to be visible and readable at all times inside the tanning salon. It is unclear whether these regulations are followed by employees of tanning salons in Germany, and we are not aware of any studies examining the implementation of the regulations at individual salons. We performed a simulated client study visiting 20 tanning salons in the city-state of Bremen in the year 2014, using a short checklist of criteria derived from the legal requirements, to evaluate whether legal requirements were followed or not. We found that only 20 % of the tanning salons communicated adverse health effects of UV radiation in visible posters and other materials and that only 60 % of the salons offered the required determination of the skin type to customers. In addition, only 60 % of the salons offered to complete the required dosage plan with their customers. To conclude, our results suggest that the new regulations are insufficiently implemented in Bremen. Additional control mechanisms appear necessary to ensure that consumers are protected from possible carcinogenic effects of excessive UV radiation.

  18. The Plasma Wake Downstream of Lunar Topographic Obstacles: Preliminary Results from 2D Particle Simulations

    NASA Technical Reports Server (NTRS)

    Zimmerman, Michael I.; Farrell, W. M.; Snubbs, T. J.; Halekas, J. S.

    2011-01-01

    Anticipating the plasma and electrical environments in permanently shadowed regions (PSRs) of the moon is critical in understanding local processes of space weathering, surface charging, surface chemistry, volatile production and trapping, exo-ion sputtering, and charged dust transport. In the present study, we have employed the open-source XOOPIC code [I] to investigate the effects of solar wind conditions and plasma-surface interactions on the electrical environment in PSRs through fully two-dimensional pattic1e-in-cell simulations. By direct analogy with current understanding of the global lunar wake (e.g., references) deep, near-terminator, shadowed craters are expected to produce plasma "mini-wakes" just leeward of the crater wall. The present results (e.g., Figure I) are in agreement with previous claims that hot electrons rush into the crater void ahead of the heavier ions, fanning a negative cloud of charge. Charge separation along the initial plasma-vacuum interface gives rise to an ambipolar electric field that subsequently accelerates ions into the void. However, the situation is complicated by the presence of the dynamic lunar surface, which develops an electric potential in response to local plasma currents (e.g., Figure Ia). In some regimes, wake structure is clearly affected by the presence of the charged crater floor as it seeks to achieve current balance (i.e. zero net current to the surface).

  19. Wide Bandpass and Narrow Bandstop Microstrip Filters Based on Hilbert Fractal Geometry: Design and Simulation Results

    PubMed Central

    Mezaal, Yaqeen S.; Eyyuboglu, Halil T.; Ali, Jawad K.

    2014-01-01

    This paper presents new Wide Bandpass Filter (WBPF) and Narrow Bandstop Filter (NBSF) incorporating two microstrip resonators, each resonator is based on 2nd iteration of Hilbert fractal geometry. The type of filter as pass or reject band has been adjusted by coupling gap parameter (d) between Hilbert resonators using a substrate with a dielectric constant of 10.8 and a thickness of 1.27 mm. Numerical simulation results as well as a parametric study of d parameter on filter type and frequency responses are presented and studied. WBPF has designed at resonant frequencies of 2 and 2.2 GHz with a bandwidth of 0.52 GHz, −28 dB return loss and −0.125 dB insertion loss while NBSF has designed for electrical specifications of 2.37 GHz center frequency, 20 MHz rejection bandwidth, −0.1873 dB return loss and 13.746 dB insertion loss. The proposed technique offers a new alternative to construct low-cost high-performance filter devices, suitable for a wide range of wireless communication systems. PMID:25536436

  20. Biofilm formation and control in a simulated spacecraft water system - Three year results

    NASA Technical Reports Server (NTRS)

    Schultz, John R.; Flanagan, David T.; Bruce, Rebekah J.; Mudgett, Paul D.; Carr, Sandra E.; Rutz, Jeffrey A.; Huls, M. H.; Sauer, Richard L.; Pierson, Duane L.

    1992-01-01

    Two simulated spacecraft water systems are being used to evaluate the effectiveness of iodine for controlling microbial contamination within such systems. An iodine concentration of about 2.0 mg/L is maintained in one system by passing ultrapure water through an iodinated ion exchange resin. Stainless steel coupons with electropolished and mechanically-polished sides are being used to monitor biofilm formation. Results after three years of operation show a single episode of significant bacterial growth in the iodinated system when the iodine level dropped to 1.9 mg/L. This growth was apparently controlled by replacing the iodinated ion exchange resin, thereby increasing the iodine level. The second batch of resin has remained effective in controlling microbial growth down to an iodine level of 1.0 mg/L. SEM indicates that the iodine has impeded but may have not completely eliminated the formation of biofilm. Metals analyses reveal some corrosion in the iodinated system after 3 years of continuous exposure. Significant microbial contamination has been present continuously in a parallel noniodinated system since the third week of operation.

  1. Simulation of natural corrosion by vapor hydration test: seven-year results

    SciTech Connect

    Luo, J.S.; Ebert, W.L.; Mazer, J.J.; Bates, J.K.

    1996-12-31

    We have investigated the alteration behavior of synthetic basalt and SRL 165 borosilicate waste glasses that had been reacted in water vapor at 70 {degrees}C for time periods up to seven years. The nature and extent of corrosion of glasses have been determined by characterizing the reacted glass surface with optical microscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive x-ray spectroscopy (EDS). Alteration in 70 {degrees}C laboratory tests was compared to that which occurs at 150-200 {degrees}C and also with Hawaiian basaltic glasses of 480 to 750 year old subaerially altered in nature. Synthetic basalt and waste glasses, both containing about 50 percent wt SiO{sub 2} were found to react with water vapor to form an amorphous hydrated gel that contained small amounts of clay, nearly identical to palagonite layers formed on naturally altered basaltic glass. This result implies that the corrosion reaction in nature can be simulated with a vapor hydration test. These tests also provide a means for measuring the corrosion kinetics, which are difficult to determine by studying natural samples because alteration layers have often spelled off the samples and we have only limited knowledge of the conditions under which alteration occurred.

  2. The Planetary Accretion Shock. I. Framework for Radiation-hydrodynamical Simulations and First Results

    NASA Astrophysics Data System (ADS)

    Marleau, Gabriel-Dominique; Klahr, Hubert; Kuiper, Rolf; Mordasini, Christoph

    2017-02-01

    The key aspect determining the postformation luminosity of gas giants has long been considered to be the energetics of the accretion shock at the surface of the planet. We use one-dimensional radiation-hydrodynamical simulations to study the radiative loss efficiency and to obtain postshock temperatures and pressures and thus entropies. The efficiency is defined as the fraction of the total incoming energy flux that escapes the system (roughly the Hill sphere), taking into account the energy recycling that occurs ahead of the shock in a radiative precursor. We focus in this paper on a constant equation of state (EOS) to isolate the shock physics but use constant and tabulated opacities. While robust quantitative results will have to await a self-consistent treatment including hydrogen dissociation and ionization, the results presented here show the correct qualitative behavior and can be understood from semianalytical calculations. The shock is found to be isothermal and supercritical for a range of conditions relevant to the core accretion formation scenario (CA), with Mach numbers { M }≳ 3. Across the shock, the entropy decreases significantly by a few times {k}{{B}}/{{baryon}}. While nearly 100% of the incoming kinetic energy is converted to radiation locally, the efficiencies are found to be as low as roughly 40%, implying that a significant fraction of the total accretion energy is brought into the planet. However, for realistic parameter combinations in the CA scenario, we find that a nonzero fraction of the luminosity always escapes the Hill sphere. This luminosity could explain, at least in part, recent observations in the young LkCa 15 and HD 100546 systems.

  3. Soil nitrogen balance under wastewater management: Field measurements and simulation results

    USGS Publications Warehouse

    Sophocleous, M.; Townsend, M.A.; Vocasek, F.; Ma, L.; KC, A.

    2009-01-01

    The use of treated wastewater for irrigation of crops could result in high nitrate-nitrogen (NO3-N) concentrations in the vadose zone and ground water. The goal of this 2-yr field-monitoring study in the deep silty clay loam soils south of Dodge City, Kansas, was to assess how and under what circumstances N from the secondary-treated, wastewater-irrigated corn reached the deep (20-45 m) water table of the underlying High Plains aquifer and what could be done to minimize this problem. We collected 15.2-m-deep soil cores for characterization of physical and chemical properties; installed neutron probe access tubes to measure soil-water content and suction lysimeters to sample soil water periodically; sampled monitoring, irrigation, and domestic wells in the area; and obtained climatic, crop, irrigation, and N application rate records for two wastewater-irrigated study sites. These data and additional information were used to run the Root Zone Water Quality Model to identify key parameters and processes that influence N losses in the study area. We demonstrated that NO3-N transport processes result in significant accumulations of N in the vadose zone and that NO3-N in the underlying ground water is increasing with time. Root Zone Water Quality Model simulations for two wastewater-irrigated study sites indicated that reducing levels of corn N fertilization by more than half to 170 kg ha-1 substantially increases N-use efficiency and achieves near-maximum crop yield. Combining such measures with a crop rotation that includes alfalfa should further reduce the accumulation and downward movement of NO3-N in the soil profile. Copyright ?? 2009 by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America. All rights reserved.

  4. Velocity structure of a bottom simulating reflector offshore Peru: Results from full waveform inversion

    USGS Publications Warehouse

    Pecher, I.A.; Minshull, T.A.; Singh, S.C.; Von Huene, R.

    1996-01-01

    Much of our knowledge of the worldwide distribution of submarine gas hydrates comes from seismic observations of Bottom Simulating Reflectors (BSRs). Full waveform inversion has proven to be a reliable technique for studying the fine structure of BSRs using the compressional wave velocity. We applied a non-linear full waveform inversion technique to a BSR at a location offshore Peru. We first determined the large-scale features of seismic velocity variations using a statistical inversion technique to maximise coherent energy along travel-time curves. These velocities were used for a starting velocity model for the full waveform inversion, which yielded a detailed velocity/depth model in the vicinity of the BSR. We found that the data are best fit by a model in which the BSR consists of a thin, low-velocity layer. The compressional wave velocity drops from 2.15 km/s down to an average of 1.70 km/s in an 18m thick interval, with a minimum velocity of 1.62 km/s in a 6 m interval. The resulting compressional wave velocity was used to estimate gas content in the sediments. Our results suggest that the low velocity layer is a 6-18 m thick zone containing a few percent of free gas in the pore space. The presence of the BSR coincides with a region of vertical uplift. Therefore, we suggest that gas at this BSR is formed by a dissociation of hydrates at the base of the hydrate stability zone due to uplift and subsequently a decrease in pressure.

  5. ATMOSPHERIC MERCURY SIMULATION USING THE CMAQ MODEL: FORMULATION DESCRIPTION AND ANALYSIS OF WET DEPOSITION RESULTS

    EPA Science Inventory

    The Community Multiscale Air Quality (CMAQ) modeling system has recently been adapted to simulate the emission, transport, transformation and deposition of atmospheric mercury in three distinct forms; elemental mercury gas, reactive gaseous mercury, and particulate mercury. Emis...

  6. Hamiltonian and potentials in derivative pricing models: exact results and lattice simulations

    NASA Astrophysics Data System (ADS)

    Baaquie, Belal E.; Corianò, Claudio; Srikant, Marakani

    2004-03-01

    The pricing of options, warrants and other derivative securities is one of the great success of financial economics. These financial products can be modeled and simulated using quantum mechanical instruments based on a Hamiltonian formulation. We show here some applications of these methods for various potentials, which we have simulated via lattice Langevin and Monte Carlo algorithms, to the pricing of options. We focus on barrier or path dependent options, showing in some detail the computational strategies involved.

  7. Transient analysis of distribution class Adaptive Var Compensators: Simulation and field test results

    SciTech Connect

    Kagalwala, R.A.; Venkata, S.S.; El-Sharkawi, M.A.; Butler, N.G.; Van Leuven, A.; Rodriguez, A.P.; Kerszenbaum, I.; Smith, D.

    1995-04-01

    Simulation studies are performed to analyze the transient behavior of the Adaptive Var Compensator (AVC), a power electronic device installed at the distribution level, during its design, installation and field testing stages. The simulation model includes detailed models for power apparatus, power semiconductor devices and low signal level electronics. Hence, by using this model, a wide range of simulation studies which contribute towards the development of the AVC and its effectiveness in the field can all be performed on the same platform. A new power electronics simulator called SABER has proven to be very effective for this study because of its model-independent structure and extensive library that covers various disciplines of engineering. The simulation studies are aimed at gaining a better understanding of the interaction between the AVC and the distribution system. They cover a range of phenomena such as switching transients due to mechanical capacitor bank closing, fast transients due to reverse recovery of the power diodes of the AVC, power system harmonics and voltage flicker problem. This paper also briefly describes the criteria for selection of the simulation tool and the models developed.

  8. Particle-In-Cell (PIC) code simulation results and comparison with theory scaling laws for photoelectron-generated radiation

    SciTech Connect

    Dipp, T.M. |

    1993-12-01

    The generation of radiation via photoelectrons induced off of a conducting surface was explored using Particle-In-Cell (PIC) code computer simulations. Using the MAGIC PIC code, the simulations were performed in one dimension to handle the diverse scale lengths of the particles and fields in the problem. The simulations involved monoenergetic, nonrelativistic photoelectrons emitted normal to the illuminated conducting surface. A sinusoidal, 100% modulated, 6.3263 ns pulse train, as well as unmodulated emission, were used to explore the behavior of the particles, fields, and generated radiation. A special postprocessor was written to convert the PIC code simulated electron sheath into far-field radiation parameters by means of rigorous retarded time calculations. The results of the small-spot PIC simulations were used to generate various graphs showing resonance and nonresonance radiation quantities such as radiated lobe patterns, frequency, and power. A database of PIC simulation results was created and, using a nonlinear curve-fitting program, compared with theoretical scaling laws. Overall, the small-spot behavior predicted by the theoretical scaling laws was generally observed in the PIC simulation data, providing confidence in both the theoretical scaling laws and the PIC simulations.

  9. High-resolution Monte Carlo simulation of flow and conservative transport in heterogeneous porous media 2. Transport results

    USGS Publications Warehouse

    Naff, R.L.; Haley, D.F.; Sudicky, E.A.

    1998-01-01

    In this, the second of two papers concerned with the use of numerical simulation to examine flow and transport parameters in heterogeneous porous media via Monte Carlo methods, results from the transport aspect of these simulations are reported on. Transport simulations contained herein assume a finite pulse input of conservative tracer, and the numerical technique endeavors to realistically simulate tracer spreading as the cloud moves through a heterogeneous medium. Medium heterogeneity is limited to the hydraulic conductivity field, and generation of this field assumes that the hydraulic- conductivity process is second-order stationary. Methods of estimating cloud moments, and the interpretation of these moments, are discussed. Techniques for estimation of large-time macrodispersivities from cloud second-moment data, and for the approximation of the standard errors associated with these macrodispersivities, are also presented. These moment and macrodispersivity estimation techniques were applied to tracer clouds resulting from transport scenarios generated by specific Monte Carlo simulations. Where feasible, moments and macrodispersivities resulting from the Monte Carlo simulations are compared with first- and second-order perturbation analyses. Some limited results concerning the possible ergodic nature of these simulations, and the presence of non- Gaussian behavior of the mean cloud, are reported on as well.

  10. Results Of Copper Catalyzed Peroxide Oxidation (CCPO) Of Tank 48H Simulants

    SciTech Connect

    Peters, T. B.; Pareizs, J. M.; Newell, J. D.; Fondeur, F. F.; Nash, C. A.; White, T. L.; Fink, S. D.

    2012-12-13

    Savannah River National Laboratory (SRNL) performed a series of laboratory-scale experiments that examined copper-catalyzed hydrogen peroxide (H{sub 2}O{sub 2}) aided destruction of organic components, most notably tetraphenylborate (TPB), in Tank 48H simulant slurries. The experiments were designed with an expectation of conducting the process within existing vessels of Building 241-96H with minimal modifications to the existing equipment. Results of the experiments indicate that TPB destruction levels exceeding 99.9% are achievable, dependent on the reaction conditions. A lower reaction pH provides faster reaction rates (pH 7 > pH 9 > pH 11); however, pH 9 reactions provide the least quantity of organic residual compounds within the limits of species analyzed. Higher temperatures lead to faster reaction rates and smaller quantities of organic residual compounds. A processing temperature of 50°C as part of an overall set of conditions appears to provide a viable TPB destruction time on the order of 4 days. Higher concentrations of the copper catalyst provide faster reaction rates, but the highest copper concentration (500 mg/L) also resulted in the second highest quantity of organic residual compounds. The data in this report suggests 100-250 mg/L as a minimum. Faster rates of H{sub 2}O{sub 2} addition lead to faster reaction rates and lower quantities of organic residual compounds. An addition rate of 0.4 mL/hour, scaled to the full vessel, is suggested for the process. SRNL recommends that for pH adjustment, an acid addition rate 42 mL/hour, scaled to the full vessel, is used. This is the same addition rate used in the testing. Even though the TPB and phenylborates can be destroyed in a relative short time period, the residual organics will take longer to degrade to <10 mg/L. Low level leaching on titanium occurred, however, the typical concentrations of released titanium are very low (~40 mg/L or less). A small amount of leaching under these conditions is not

  11. MULTI - TRACER CONTROL ROOM AIR INLEAKAGE PROTOCOL AND SIMULATED PRIMARY AND EXTENDED MULTI - ZONE RESULTS.

    SciTech Connect

    DIETZ,R.N.

    2002-01-01

    The perfluorocarbon tracer (PFT) technology can be applied simultaneously to the wide range in zonal flowrates (from tens of cfms in some Control Rooms to almost 1,000,000 cfm in Turbine Buildings), to achieve the necessary uniform tagging for subsequent determination of the desired air inleakage and outleakage from all zones surrounding a plant's Control Room (CR). New types of PFT sources (Mega sources) were devised and tested to handle the unusually large flowrates in a number of HVAC zones in power stations. A review of the plans of a particular nuclear power plant and subsequent simulations of the tagging and sampling results confirm that the technology can provide the necessary concentration measurement data to allow the important ventilation pathways involving the Control Room and its air flow communications with all adjacent zones to be quantitatively determined with minimal uncertainty. Depending on need, a simple single or 3-zone scheme (involving the Control Room alone or along with the Aux. Bldg. and Turbine Bldg.) or a more complex test involving up to 7 zones simultaneously can be accommodated with the current revisions to the technology; to test all the possible flow pathways, several different combinations of up to 7 zones would need to be run. The potential exists that for an appropriate investment, in about 2 years, it would be possible to completely evaluate an entire power plant in a single extended multizone test with up to 12 to 13 separate HVAC zones. With multiple samplers in the Control Room near each of the contiguous zones, not only will the prevalent inleakage or outleakage zones be documented, but the particular location of the pathway's room of ingress can be identified. The suggested protocol is to perform a 3-zone test involving the Control Room, Aux. Bldg., and Turbine Bldg. to (1) verify CR total inleakage and (2) proportion that inleakage to distinguish that from the other 2 major buildings and any remaining untagged locations

  12. Planck 2013 results. X. HFI energetic particle effects: characterization, removal, and simulation

    NASA Astrophysics Data System (ADS)

    Planck Collaboration; Ade, P. A. R.; Aghanim, N.; Armitage-Caplan, C.; Arnaud, M.; Ashdown, M.; Atrio-Barandela, F.; Aumont, J.; Baccigalupi, C.; Banday, A. J.; Barreiro, R. B.; Battaner, E.; Benabed, K.; Benoît, A.; Benoit-Lévy, A.; Bernard, J.-P.; Bersanelli, M.; Bielewicz, P.; Bobin, J.; Bock, J. J.; Bond, J. R.; Borrill, J.; Bouchet, F. R.; Bridges, M.; Bucher, M.; Burigana, C.; Cardoso, J.-F.; Catalano, A.; Challinor, A.; Chamballu, A.; Chiang, H. C.; Chiang, L.-Y.; Christensen, P. R.; Church, S.; Clements, D. L.; Colombi, S.; Colombo, L. P. L.; Couchot, F.; Coulais, A.; Crill, B. P.; Curto, A.; Cuttaia, F.; Danese, L.; Davies, R. D.; de Bernardis, P.; de Rosa, A.; de Zotti, G.; Delabrouille, J.; Delouis, J.-M.; Désert, F.-X.; Diego, J. M.; Dole, H.; Donzelli, S.; Doré, O.; Douspis, M.; Dupac, X.; Efstathiou, G.; Enßlin, T. A.; Eriksen, H. K.; Finelli, F.; Forni, O.; Frailis, M.; Franceschi, E.; Galeotta, S.; Ganga, K.; Giard, M.; Girard, D.; Giraud-Héraud, Y.; González-Nuevo, J.; Górski, K. M.; Gratton, S.; Gregorio, A.; Gruppuso, A.; Hansen, F. K.; Hanson, D.; Harrison, D.; Henrot-Versillé, S.; Hernández-Monteagudo, C.; Herranz, D.; Hildebrandt, S. R.; Hivon, E.; Hobson, M.; Holmes, W. A.; Hornstrup, A.; Hovest, W.; Huffenberger, K. M.; Jaffe, A. H.; Jaffe, T. R.; Jones, W. C.; Juvela, M.; Keihänen, E.; Keskitalo, R.; Kisner, T. S.; Kneissl, R.; Knoche, J.; Knox, L.; Kunz, M.; Kurki-Suonio, H.; Lagache, G.; Lamarre, J.-M.; Lasenby, A.; Laureijs, R. J.; Lawrence, C. R.; Leonardi, R.; Leroy, C.; Lesgourgues, J.; Liguori, M.; Lilje, P. B.; Linden-Vørnle, M.; López-Caniego, M.; Lubin, P. M.; Macías-Pérez, J. F.; Mandolesi, N.; Maris, M.; Marshall, D. J.; Martin, P. G.; Martínez-González, E.; Masi, S.; Massardi, M.; Matarrese, S.; Matthai, F.; Mazzotta, P.; McGehee, P.; Melchiorri, A.; Mendes, L.; Mennella, A.; Migliaccio, M.; Miniussi, A.; Mitra, S.; Miville-Deschênes, M.-A.; Moneti, A.; Montier, L.; Morgante, G.; Mortlock, D.; Mottet, S.; Munshi, D.; Murphy, J. A.; Naselsky, P.; Nati, F.; Natoli, P.; Netterfield, C. B.; Nørgaard-Nielsen, H. U.; Noviello, F.; Novikov, D.; Novikov, I.; Osborne, S.; Oxborrow, C. A.; Paci, F.; Pagano, L.; Pajot, F.; Paoletti, D.; Pasian, F.; Patanchon, G.; Perdereau, O.; Perotto, L.; Perrotta, F.; Piacentini, F.; Piat, M.; Pierpaoli, E.; Pietrobon, D.; Plaszczynski, S.; Pointecouteau, E.; Polenta, G.; Ponthieu, N.; Popa, L.; Poutanen, T.; Pratt, G. W.; Prézeau, G.; Prunet, S.; Puget, J.-L.; Rachen, J. P.; Racine, B.; Reinecke, M.; Remazeilles, M.; Renault, C.; Ricciardi, S.; Riller, T.; Ristorcelli, I.; Rocha, G.; Rosset, C.; Roudier, G.; Rusholme, B.; Sanselme, L.; Santos, D.; Sauvé, A.; Savini, G.; Scott, D.; Shellard, E. P. S.; Spencer, L. D.; Starck, J.-L.; Stolyarov, V.; Stompor, R.; Sudiwala, R.; Sureau, F.; Sutton, D.; Suur-Uski, A.-S.; Sygnet, J.-F.; Tauber, J. A.; Tavagnacco, D.; Terenzi, L.; Toffolatti, L.; Tomasi, M.; Tristram, M.; Tucci, M.; Umana, G.; Valenziano, L.; Valiviita, J.; Van Tent, B.; Vielva, P.; Villa, F.; Vittorio, N.; Wade, L. A.; Wandelt, B. D.; Yvon, D.; Zacchei, A.; Zonca, A.

    2014-11-01

    We describe the detection, interpretation, and removal of the signal resulting from interactions of high energy particles with the Planck High Frequency Instrument (HFI). There are two types of interactions: heating of the 0.1 K bolometer plate; and glitches in each detector time stream. The transientresponses to detector glitch shapes are not simple single-pole exponential decays and fall into three families. The glitch shape for each family has been characterized empirically in flight data and these shapes have been used to remove glitches from the detector time streams. The spectrum of the count rate per unit energy is computed for each family and a correspondence is made to the location on the detector of the particle hit. Most of the detected glitches are from Galactic protons incident on the die frame supporting the micro-machined bolometric detectors. In the Planck orbit at L2, the particle flux is around 5 cm-2 s-1 and is dominated by protons incident on the spacecraft with energy >39 MeV, at a rate of typically one event per second per detector. Different categories of glitches have different signatures in the time stream. Two of the glitch types have a low amplitude component that decays over nearly 1 s. This component produces excess noise if not properly removed from the time-ordered data. We have used a glitch detection and subtraction method based on the joint fit of population templates. The application of this novel glitch subtraction method removes excess noise from the time streams. Using realistic simulations, we find that this method does not introduce signal bias into the Planck data.

  13. Results from simulated contact-handled transuranic waste experiments at the Waste Isolation Pilot Plant

    SciTech Connect

    Molecke, M.A.; Sorensen, N.R.; Krumhansl, J.L.

    1993-12-31

    We conducted in situ experiments with nonradioactive, contact-handled transuranic (CH TRU) waste drums at the Waste Isolation Pilot Plant (WIPP) facility for about four years. We performed these tests in two rooms in rock salt, at WIPP, with drums surrounded by crushed salt or 70 wt % salt/30 wt % bentonite clay backfills, or partially submerged in a NaCl brine pool. Air and brine temperatures were maintained at {approximately}40C. These full-scale (210-L drum) experiments provided in situ data on: backfill material moisture-sorption and physical properties in the presence of brine; waste container corrosion adequacy; and, migration of chemical tracers (nonradioactive actinide and fission product simulants) in the near-field vicinity, all as a function of time. Individual drums, backfill, and brine samples were removed periodically for laboratory evaluations. Waste container testing in the presence of brine and brine-moistened backfill materials served as a severe overtest of long-term conditions that could be anticipated in an actual salt waste repository. We also obtained relevant operational-test emplacement and retrieval experience. All test results are intended to support both the acceptance of actual TRU wastes at the WIPP and performance assessment data needs. We provide an overview and technical data summary focusing on the WIPP CH TRU envirorunental overtests involving 174 waste drums in the presence of backfill materials and the brine pool, with posttest laboratory materials analyses of backfill sorbed-moisture content, CH TRU drum corrosion, tracer migration, and associated test observations.

  14. Design, Results, Evolution and Status of the ATLAS Simulation at Point1 Project

    NASA Astrophysics Data System (ADS)

    Ballestrero, S.; Batraneanu, S. M.; Brasolin, F.; Contescu, C.; Fazio, D.; Di Girolamo, A.; Lee, C. J.; Pozo Astigarraga, M. E.; Scannicchio, D. A.; Sedov, A.; Twomey, M. S.; Wang, F.; Zaytsev, A.

    2015-12-01

    During the LHC Long Shutdown 1 (LSI) period, that started in 2013, the Simulation at Point1 (Sim@P1) project takes advantage, in an opportunistic way, of the TDAQ (Trigger and Data Acquisition) HLT (High-Level Trigger) farm of the ATLAS experiment. This farm provides more than 1300 compute nodes, which are particularly suited for running event generation and Monte Carlo production jobs that are mostly CPU and not I/O bound. It is capable of running up to 2700 Virtual Machines (VMs) each with 8 CPU cores, for a total of up to 22000 parallel jobs. This contribution gives a review of the design, the results, and the evolution of the Sim@P1 project, operating a large scale OpenStack based virtualized platform deployed on top of the ATLAS TDAQ HLT farm computing resources. During LS1, Sim@P1 was one of the most productive ATLAS sites: it delivered more than 33 million CPU-hours and it generated more than 1.1 billion Monte Carlo events. The design aspects are presented: the virtualization platform exploited by Sim@P1 avoids interferences with TDAQ operations and it guarantees the security and the usability of the ATLAS private network. The cloud mechanism allows the separation of the needed support on both infrastructural (hardware, virtualization layer) and logical (Grid site support) levels. This paper focuses on the operational aspects of such a large system during the upcoming LHC Run 2 period: simple, reliable, and efficient tools are needed to quickly switch from Sim@P1 to TDAQ mode and back, to exploit the resources when they are not used for the data acquisition, even for short periods. The evolution of the central OpenStack infrastructure is described, as it was upgraded from Folsom to the Icehouse release, including the scalability issues addressed.

  15. Development and simulation results of a sparsification and readout circuit for wide pixel matrices

    NASA Astrophysics Data System (ADS)

    Gabrielli, A.; Giorgi, F.; Morsani, F.; Villa, M.

    2011-06-01

    In future collider experiments, the increasing luminosity and centre of mass energy are rising challenging problems in the design of new inner tracking systems. In this context we develop high-efficiency readout architectures for large binary pixel matrices that are meant to cope with the high-stressing conditions foreseen in the innermost layers of a tracker [The SuperB Conceptual Design Report, INFN/AE-07/02, SLAC-R-856, LAL 07-15, Available online at: http://www.pi.infn.it/SuperB]. We model and design digital readout circuits to be integrated on VLSI ASICs. These architectures can be realized with different technology processes and sensors: they can be implemented on the same silicon sensor substrate of a CMOS MAPS devices (Monolithic Active Pixel Sensor), on the CMOS tier of a hybrid pixel sensor or in a 3D chip where the digital layer is stacked on the sensor and the analog layers [V. Re et al., Nuc. Instr. and Meth. in Phys. Res. A, doi:10.1016/j.nima.2010.05.039]. In the presented work, we consider a data-push architecture designed for a sensor matrix of an area of about 1.3 cm 2 with a pitch of 50 microns. The readout circuit tries to take great advantage of the high density of in-pixel digital logic allowed by vertical integration. We aim at sustaining a rate density of 100 Mtrack ṡ s -1 ṡ cm -2 with a temporal resolution below 1 μs. We show how this architecture can cope with these stressing conditions presenting the results of Monte Carlo simulations.

  16. Recovery of yttrium from cathode ray tubes and lamps’ fluorescent powders: experimental results and economic simulation

    SciTech Connect

    Innocenzi, V. De Michelis, I.; Ferella, F.; Vegliò, F.

    2013-11-15

    Highlights: • Fluorescent powder of lamps. • Fluorescent powder of cathode ray rubes. • Recovery of yttrium from fluorescent powders. • Economic simulation for the processes to recover yttrium from WEEE. - Abstract: In this paper, yttrium recovery from fluorescent powder of lamps and cathode ray tubes (CRTs) is described. The process for treating these materials includes the following: (a) acid leaching, (b) purification of the leach liquors using sodium hydroxide and sodium sulfide, (c) precipitation of yttrium using oxalic acid, and (d) calcinations of oxalates for production of yttrium oxides. Experimental results have shown that process conditions necessary to purify the solutions and recover yttrium strongly depend on composition of the leach liquor, in other words, whether the powder comes from treatment of CRTs or lamp. In the optimal experimental conditions, the recoveries of yttrium oxide are about 95%, 55%, and 65% for CRT, lamps, and CRT/lamp mixture (called MIX) powders, respectively. The lower yields obtained during treatments of MIX and lamp powders are probably due to the co-precipitation of yttrium together with other metals contained in the lamps powder only. Yttrium loss can be reduced to minimum changing the experimental conditions with respect to the case of the CRT process. In any case, the purity of final products from CRT, lamps, and MIX is greater than 95%. Moreover, the possibility to treat simultaneously both CRT and lamp powders is very important and interesting from an industrial point of view since it could be possible to run a single plant treating fluorescent powder coming from two different electronic wastes.

  17. Testing and Results of Human Metabolic Simulation Utilizing Ultrasonic Nebulizer Technology for Water Vapor Generation

    NASA Technical Reports Server (NTRS)

    Stubbe, Matthew; Curley, Su

    2010-01-01

    Life support technology must be evaluated thoroughly before ever being implemented into a functioning design. A major concern during that evaluation is safety. The ability to mimic human metabolic loads allows test engineers to evaluate the effectiveness of new technologies without risking injury to any actual humans. The main function of most life support technologies is the removal of carbon dioxide (CO2) and water (H2O) vapor. As such any good human metabolic simulator (HMS) will mimic the human body s ability to produce these items. Introducing CO2 into a test chamber is a very straightforward process with few unknowns so the focus of this particular new HMS design was on the much more complicated process of introducing known quantities of H2O vapor on command. Past iterations of the HMS have utilized steam which is very hard to keep in vapor phase while transporting and injecting into a test chamber. Also steam adds large quantities of heat to any test chamber, well beyond what an actual human does. For the new HMS an alternative approach to water vapor generation was designed utilizing ultrasonic nebulizers as a method for creating water vapor. Ultrasonic technology allows water to be vibrated into extremely tiny pieces (2-5 microns) and evaporate without requiring additional heating. Doing this process inside the test chamber itself allows H2O vapor generation without the unwanted heat and the challenging process of transporting water vapor. This paper presents the design details as well as results of all initial and final acceptance system testing. Testing of the system was performed at a range of known human metabolic rates in both sea-level and reduced pressure environments. This multitude of test points fully defines the systems capabilities as they relate to actual environmental systems testing.

  18. Result of Monte-Carlo simulation of electron-photon cascades in lead and layers of lead-scintillator

    NASA Technical Reports Server (NTRS)

    Wasilewski, A.; Krys, E.

    1985-01-01

    Results of Monte-Carlo simulation of electromagnetic cascade development in lead and lead-scintillator sandwiches are analyzed. It is demonstrated that the structure function for core approximation is not applicable in the case in which the primary energy is higher than 100 GeV. The simulation data has shown that introducing an inhomogeneous chamber structure results in subsequent reduction of secondary particles.

  19. Large-scale Validation of AMIP II Land-surface Simulations: Preliminary Results for Ten Models

    SciTech Connect

    Phillips, T J; Henderson-Sellers, A; Irannejad, P; McGuffie, K; Zhang, H

    2005-12-01

    This report summarizes initial findings of a large-scale validation of the land-surface simulations of ten atmospheric general circulation models that are entries in phase II of the Atmospheric Model Intercomparison Project (AMIP II). This validation is conducted by AMIP Diagnostic Subproject 12 on Land-surface Processes and Parameterizations, which is focusing on putative relationships between the continental climate simulations and the associated models' land-surface schemes. The selected models typify the diversity of representations of land-surface climate that are currently implemented by the global modeling community. The current dearth of global-scale terrestrial observations makes exacting validation of AMIP II continental simulations impractical. Thus, selected land-surface processes of the models are compared with several alternative validation data sets, which include merged in-situ/satellite products, climate reanalyses, and off-line simulations of land-surface schemes that are driven by observed forcings. The aggregated spatio-temporal differences between each simulated process and a chosen reference data set then are quantified by means of root-mean-square error statistics; the differences among alternative validation data sets are similarly quantified as an estimate of the current observational uncertainty in the selected land-surface process. Examples of these metrics are displayed for land-surface air temperature, precipitation, and the latent and sensible heat fluxes. It is found that the simulations of surface air temperature, when aggregated over all land and seasons, agree most closely with the chosen reference data, while the simulations of precipitation agree least. In the latter case, there also is considerable inter-model scatter in the error statistics, with the reanalyses estimates of precipitation resembling the AMIP II simulations more than to the chosen reference data. In aggregate, the simulations of land-surface latent and sensible

  20. Application of high resolution land use and land cover data for atmospheric modeling in the Houston-Galveston Metropolitan area: Part II. Air quality simulation results

    NASA Astrophysics Data System (ADS)

    Cheng, Fang-Yi; Kim, Soontae; Byun, Daewon W.

    In the companion paper, we showed that MM5 simulation using a satellite-derived high resolution Texas Forest Service (TFS) land use and land cover (LULC) data set (M2), compared to the MM5 results with the default USGS-LULC (M1), improved representation of the complicated features of the atmospheric planetary boundary layer (PBL) in the Houston ship channel (HSC) area, where large industrial emission sources are concentrated. In the present paper, the study is extended to investigate these effects on air quality simulations. Two emission inputs, namely E1 and E2, are prepared with the M1 and M2 meteorology data, respectively, to reflect the differences in the point source plume rise estimates while keeping the biogenic and mobile emissions the same. Air quality simulations were performed with CMAQ using the M1E1 and M2E2 inputs. The simulation results demonstrate the importance of utilizing high resolution LULC data. In the default LULC data, the HSC area was classified as grass land cover, and MM5 predicted confined mixing, resulting in over-prediction of ozone (O 3) precursors, such as NO x (NO plus NO 2), and highly reactive volatile organic compounds (HRVOC) species, including ethylene and propylene, over the HSC area. In the TFS data, the area was classified as the impervious "urban" land use and MM5 predicted enhanced mixing of the precursor species, leading to better agreements with measurements. The high resolution LULC also resolves the location of water body near the HSC more accurately, predicting shallower PBL heights than the default LULC during daytime. With favorable wind conditions, the O 3 precursors were transported from the HSC emission source towards the area, trapping the pollutants in a confined shallow mixing layer that occasionally led to a rapid photochemical production of O 3. The above comparison includes the changes in both meteorological and plume-rise emissions inputs. We performed two additional CMAQ simulations using the same

  1. Simulation test results for lift/cruise fan research and technology aircraft

    NASA Technical Reports Server (NTRS)

    Bland, M. P.; Konsewicz, R. K.

    1976-01-01

    A flight simulation program was conducted on the flight simulator for advanced aircraft (FSAA). The flight simulation was a part of a contracted effort to provide a lift/cruise fan V/STOL aircraft mathematical model for flight simulation. The simulated aircraft is a configuration of the Lift/Cruise Fan V/STOL research technology aircraft (RTA). The aircraft was powered by three gas generators driving three fans. One lift fan was installed in the nose of the aircraft, and two lift/cruise fans at the wing root. The thrust of these fans was modulated to provide pitch and roll control, and vectored to provide yaw, side force control, and longitudinal translation. Two versions of the RTA were defined. One was powered by the GE J97/LF460 propulsion system which was gas-coupled for power transfer between fans for control. The other version was powered by DDA XT701 gas generators driving 62 inch variable pitch fans. The flight control system in both versions of the RTA was the same.

  2. Three-dimensional MHD simulation of the Caltech plasma jet experiment: first results

    SciTech Connect

    Zhai, Xiang; Bellan, Paul M.; Li, Hui; Li, Shengtai E-mail: pbellan@caltech.edu E-mail: sli@lanl.gov

    2014-08-10

    Magnetic fields are believed to play an essential role in astrophysical jets with observations suggesting the presence of helical magnetic fields. Here, we present three-dimensional (3D) ideal MHD simulations of the Caltech plasma jet experiment using a magnetic tower scenario as the baseline model. Magnetic fields consist of an initially localized dipole-like poloidal component and a toroidal component that is continuously being injected into the domain. This flux injection mimics the poloidal currents driven by the anode-cathode voltage drop in the experiment. The injected toroidal field stretches the poloidal fields to large distances, while forming a collimated jet along with several other key features. Detailed comparisons between 3D MHD simulations and experimental measurements provide a comprehensive description of the interplay among magnetic force, pressure, and flow effects. In particular, we delineate both the jet structure and the transition process that converts the injected magnetic energy to other forms. With suitably chosen parameters that are derived from experiments, the jet in the simulation agrees quantitatively with the experimental jet in terms of magnetic/kinetic/inertial energy, total poloidal current, voltage, jet radius, and jet propagation velocity. Specifically, the jet velocity in the simulation is proportional to the poloidal current divided by the square root of the jet density, in agreement with both the experiment and analytical theory. This work provides a new and quantitative method for relating experiments, numerical simulations, and astrophysical observation, and demonstrates the possibility of using terrestrial laboratory experiments to study astrophysical jets.

  3. End-to-end simulation of high-contrast imaging systems: methods and results for the PICTURE mission family

    NASA Astrophysics Data System (ADS)

    Douglas, Ewan S.; Hewasawam, Kuravi; Mendillo, Christopher B.; Cahoy, Kerri L.; Cook, Timothy A.; Finn, Susanna C.; Howe, Glenn A.; Kuchner, Marc J.; Lewis, Nikole K.; Marinan, Anne D.; Mawet, Dimitri; Chakrabarti, Supriya

    2015-09-01

    We describe a set of numerical approaches to modeling the performance of space flight high-contrast imaging payloads. Mission design for high-contrast imaging requires numerical wavefront error propagation to ensure accurate component specifications. For constructed instruments, wavelength and angle-dependent throughput and contrast models allow detailed simulations of science observations, allowing mission planners to select the most productive science targets. The PICTURE family of missions seek to quantify the optical brightness of scattered light from extrasolar debris disks via several high-contrast imaging techniques: sounding rocket (the Planet Imaging Concept Testbed Using a Rocket Experiment) and balloon flights of a visible nulling coronagraph, as well as a balloon flight of a vector vortex coronagraph (the Planetary Imaging Concept Testbed Using a Recoverable Experiment - Coronagraph, PICTURE-C). The rocket mission employs an on-axis 0.5m Gregorian telescope, while the balloon flights will share an unobstructed off-axis 0.6m Gregorian. This work details the flexible approach to polychromatic, end-to-end physical optics simulations used for both the balloon vector vortex coronagraph and rocket visible nulling coronagraph missions. We show the preliminary PICTURE-C telescope and vector vortex coronagraph design will achieve 10-8 contrast without post-processing as limited by realistic optics, but not considering polarization or low-order errors. Simulated science observations of the predicted warm ring around Epsilon Eridani illustrate the performance of both missions.

  4. Some Results of Weak Anticipative Concept Applied in Simulation Based Decision Support in Enterprise

    NASA Astrophysics Data System (ADS)

    Kljajić, Miroljub; Kofjač, Davorin; Kljajić Borštnar, Mirjana; Škraba, Andrej

    2010-11-01

    The simulation models are used as for decision support and learning in enterprises and in schools. Tree cases of successful applications demonstrate usefulness of weak anticipative information. Job shop scheduling production with makespan criterion presents a real case customized flexible furniture production optimization. The genetic algorithm for job shop scheduling optimization is presented. Simulation based inventory control for products with stochastic lead time and demand describes inventory optimization for products with stochastic lead time and demand. Dynamic programming and fuzzy control algorithms reduce the total cost without producing stock-outs in most cases. Values of decision making information based on simulation were discussed too. All two cases will be discussed from optimization, modeling and learning point of view.

  5. Comparison of preliminary results from Airborne Aster Simulator (AAS) with TIMS data

    NASA Technical Reports Server (NTRS)

    Kannari, Yoshiaki; Mills, Franklin; Watanabe, Hiroshi; Ezaka, Teruya; Narita, Tatsuhiko; Chang, Sheng-Huei

    1992-01-01

    The Japanese Advanced Spaceborne Thermal Emission and Reflection radiometer (ASTER), being developed for a NASA EOS-A satellite, will have 3 VNIR, 6 SWIR, and 5 TIR (8-12 micron) bands. An Airborne ASTER Simulator (AAS) was developed for Japan Resources Observation System Organization (JAROS) by the Geophysical Environmental Research Group (GER) Corp. to research surface temperature and emission features in the MWIR/TIR, to simulate ASTER's TIR bands, and to study further possibility of MWIR/TIR bands. ASTER Simulator has 1 VNIR, 3 MWIR (3-5 microns), and 20 (currently 24) TIR bands. Data was collected over 3 sites - Cuprite, Nevada; Long Valley/Mono Lake, California; and Death Valley, California - with simultaneous ground truth measurements. Preliminary data collected by AAS for Cuprite, Nevada is presented and AAS data is compared with Thermal Infrared Multispectral Scanner (TIMS) data.

  6. Preliminary results of column experiments simulating nutrients transport in artificial recharge by treated wastewater

    NASA Astrophysics Data System (ADS)

    Leal, María; Meffe, Raffaella; Lillo, Javier

    2013-04-01

    the field site. Wastewater synthesized in the laboratory simulates the secondary effluent used for recharge activities in the Experimental Plant of Carrión