Results from Numerical General Relativity
NASA Technical Reports Server (NTRS)
Baker, John G.
2011-01-01
For several years numerical simulations have been revealing the details of general relativity's predictions for the dynamical interactions of merging black holes. I will review what has been learned of the rich phenomenology of these mergers and the resulting gravitational wave signatures. These wave forms provide a potentially observable record of the powerful astronomical events, a central target of gravitational wave astronomy. Asymmetric radiation can produce a thrust on the system which may accelerate the single black hole resulting from the merger to high relative velocity.
Numerical taxonomy on data: Experimental results
Cohen, J.; Farach, M.
1997-12-01
The numerical taxonomy problems associated with most of the optimization criteria described above are NP - hard [3, 5, 1, 4]. In, the first positive result for numerical taxonomy was presented. They showed that if e is the distance to the closest tree metric under the L{sub {infinity}} norm. i.e., e = min{sub T} [L{sub {infinity}} (T-D)], then it is possible to construct a tree T such that L{sub {infinity}} (T-D) {le} 3e, that is, they gave a 3-approximation algorithm for this problem. We will refer to this algorithm as the Single Pivot (SP) heuristic.
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.
Saturn's North Polar Hexagon Numerical Modeling Results
NASA Astrophysics Data System (ADS)
Morales-Juberias, R.; Sayanagi, K. M.; Dowling, T. E.
2008-12-01
In 1980, Voyager images revealed the presence of a circumpolar wave at 78 degrees planetographic latitude in the northern hemisphere of Saturn. It was notable for having a dominant planetary wavenumber-six zonal mode, and for being stationary with respect to Saturn's Kilometric Radiation rotation rate measured by Voyager. The center of this hexagonal feature was coincident with the center of a sharp eastward jet with a peak speed of 100 ms-1 and it had a meridional width of about 4 degrees. This hexagonal feature was confirmed in 1991 through ground-based observations, and it was observed again in 2006 with the Cassini VIMS instrument. The latest observations highlight the longevity of the hexagon and suggest that it extends at least several bars deep into the atmosphere. We use the Explicit Planetary Isentropic Code (EPIC) to perform high-resolution numerical simulations of this unique feature. We show that a wavenumber six instability mode arises naturally from initially barotropic jets when seeded with weak random turbulence. We also discuss the properties of the wave activity on the background vertical stability, zonal wind, planetary rotation rate and adjacent vortices. Computational resources were provided by the New Mexico Computing Applications Center and New Mexico Institute of Mining and Technology and the Comparative Planetology Laboratory at the University of Louisville.
Numerical results for the WFNDEC 2012 eddy current benchmark problem
NASA Astrophysics Data System (ADS)
Theodoulidis, T. P.; Martinos, J.; Poulakis, N.
2013-01-01
We present numerical results for the World Federation of NDE Centers (WFNDEC) 2012 eddy current benchmark problem obtained with a commercial FEM package (Comsol Multiphysics). The measurements of the benchmark problem consist of coil impedance values acquired when an inspection probe coil is moved inside an Inconel tube along an axial through-wall notch. The simulation runs smoothly with minimal user interference (default settings used for mesh and solver) and agreement between numerical and experimental results is excellent for all five inspection frequencies. Comments are made for the pros and cons of FEM and also some good practice rules are presented when using such numerical tools.
Sheet Hydroforming Process Numerical Model Improvement Through Experimental Results Analysis
NASA Astrophysics Data System (ADS)
Gabriele, Papadia; Antonio, Del Prete; Alfredo, Anglani
2010-06-01
The increasing application of numerical simulation in metal forming field has helped engineers to solve problems one after another to manufacture a qualified formed product reducing the required time [1]. Accurate simulation results are fundamental for the tooling and the product designs. The wide application of numerical simulation is encouraging the development of highly accurate simulation procedures to meet industrial requirements. Many factors can influence the final simulation results and many studies have been carried out about materials [2], yield criteria [3] and plastic deformation [4,5], process parameters [6] and their optimization. In order to develop a reliable hydromechanical deep drawing (HDD) numerical model the authors have been worked out specific activities based on the evaluation of the effective stiffness of the blankholder structure [7]. In this paper after an appropriate tuning phase of the blankholder force distribution, the experimental activity has been taken into account to improve the accuracy of the numerical model. In the first phase, the effective capability of the blankholder structure to transfer the applied load given by hydraulic actuators to the blank has been explored. This phase ended with the definition of an appropriate subdivision of the blankholder active surface in order to take into account the effective pressure map obtained for the given loads configuration. In the second phase the numerical results obtained with the developed subdivision have been compared with the experimental data of the studied model. The numerical model has been then improved, finding the best solution for the blankholder force distribution.
Interaction between subducting plates: results from numerical and analogue modeling
NASA Astrophysics Data System (ADS)
Kiraly, Agnes; Capitanio, Fabio A.; Funiciello, Francesca; Faccenna, Claudio
2016-04-01
The tectonic setting of the Alpine-Mediterranean area is achieved during the late Cenozoic subduction, collision and suturing of several oceanic fragments and continental blocks. In this stage, processes such as interactions among subducting slabs, slab migrations and related mantle flow played a relevant role on the resulting tectonics. Here, we use numerical models to first address the mantle flow characteristic in 3D. During the subduction of a single plate the strength of the return flow strongly depends on the slab pull force, that is on the plate's buoyancy, however the physical properties of the slab, such as density, viscosity or width, do not affect largely the morphology of the toroidal cell. Instead, dramatic effects on the geometry and the dynamics of the toroidal cell result in models where the thickness of the mantle is varied. The vertical component of the vorticity vector is used to define the characteristic size of the toroidal cell, which is ~1.2-1.3 times the mantle depth. This latter defines the range of viscous stress propagation through the mantle and consequent interactions with other slabs. We thus further investigate on this setup where two separate lithospheric plates subduct in opposite sense, developing opposite polarities and convergent slab retreat, and model different initial sideways distance between the plates. The stress profiles in time illustrate that the plates interacts when slabs are at the characteristic distance and the two slabs toroidal cells merge. Increased stress and delayed slab migrations are the results. Analogue models of double-sided subduction show similar maximum distance and allow testing the additional role of stress propagated through the plates. We use a silicon plate subducting on its two opposite margins, which is either homogeneous or comprises oceanic and continental lithospheres, differing in buoyancy. The modeling results show that the double-sided subduction is strongly affected by changes in plate
Numerical Results of 3-D Modeling of Moon Accumulation
NASA Astrophysics Data System (ADS)
Khachay, Yurie; Anfilogov, Vsevolod; Antipin, Alexandr
2014-05-01
For the last time for the model of the Moon usually had been used the model of mega impact in which the forming of the Earth and its sputnik had been the consequence of the Earth's collision with the body of Mercurial mass. But all dynamical models of the Earth's accumulation and the estimations after the Pb-Pb system, lead to the conclusion that the duration of the planet accumulation was about 1 milliard years. But isotopic results after the W-Hf system testify about a very early (5-10) million years, dividing of the geochemical reservoirs of the core and mantle. In [1,2] it is shown, that the account of energy dissipating by the decay of short living radioactive elements and first of all Al26,it is sufficient for heating even small bodies with dimensions about (50-100) km up to the iron melting temperature and can be realized a principal new differentiation mechanism. The inner parts of the melted preplanets can join and they are mainly of iron content, but the cold silicate fragments return to the supply zone and additionally change the content of Moon forming to silicates. Only after the increasing of the gravitational radius of the Earth, the growing area of the future Earth's core can save also the silicate envelope fragments [3]. For understanding the further system Earth-Moon evolution it is significant to trace the origin and evolution of heterogeneities, which occur on its accumulation stage.In that paper we are modeling the changing of temperature,pressure,velocity of matter flowing in a block of 3d spherical body with a growing radius. The boundary problem is solved by the finite-difference method for the system of equations, which include equations which describe the process of accumulation, the Safronov equation, the equation of impulse balance, equation Navier-Stocks, equation for above litho static pressure and heat conductivity in velocity-pressure variables using the Businesque approach.The numerical algorithm of the problem solution in velocity
Some theoretical and numerical results for delayed neural field equations
NASA Astrophysics Data System (ADS)
Faye, Grégory; Faugeras, Olivier
2010-05-01
In this paper we study neural field models with delays which define a useful framework for modeling macroscopic parts of the cortex involving several populations of neurons. Nonlinear delayed integro-differential equations describe the spatio-temporal behavior of these fields. Using methods from the theory of delay differential equations, we show the existence and uniqueness of a solution of these equations. A Lyapunov analysis gives us sufficient conditions for the solutions to be asymptotically stable. We also present a fairly detailed study of the numerical computation of these solutions. This is, to our knowledge, the first time that a serious analysis of the problem of the existence and uniqueness of a solution of these equations has been performed. Another original contribution of ours is the definition of a Lyapunov functional and the result of stability it implies. We illustrate our numerical schemes on a variety of examples that are relevant to modeling in neuroscience.
Additional results on orbits of Hilda-type asteroids
NASA Astrophysics Data System (ADS)
Schubart, J.
1991-01-01
The long period evolution of the Hilda-type orbits is studied by numerical integration. Three characteristic parameters are derived for Hildas numbered during the 1982-89 period. The distribution of orbits and subgroups of orbits is considered with respect to these parameters. Special attention is given to low-eccentricity orbits and to the observation conditions. The numerical integrations depend on a model of the forces due to Jupiter and Saturn.
Integrating Numerical Groundwater Modeling Results With Geographic Information Systems
NASA Astrophysics Data System (ADS)
Witkowski, M. S.; Robinson, B. A.; Linger, S. P.
2001-12-01
Many different types of data are used to create numerical models of flow and transport of groundwater in the vadose zone. Results from water balance studies, infiltration models, hydrologic properties, and digital elevation models (DEMs) are examples of such data. Because input data comes in a variety of formats, for consistency the data need to be assembled in a coherent fashion on a single platform. Through the use of a geographic information system (GIS), all data sources can effectively be integrated on one platform to store, retrieve, query, and display data. In our vadoze zone modeling studies in support of Los Alamos National Laboratory's Environmental Restoration Project, we employ a GIS comprised of a Raid storage device, an Oracle database, ESRI's spatial database engine (SDE), ArcView GIS, and custom GIS tools for three-dimensional (3D) analysis. We store traditional GIS data, such as, contours, historical building footprints, and study area locations, as points, lines, and polygons with attributes. Numerical flow and transport model results from the Finite Element Heat and Mass Transfer Code (FEHM) are stored as points with attributes, such as fluid saturation, or pressure, or contaminant concentration at a given location. We overlay traditional types of GIS data with numerical model results, thereby allowing us to better build conceptual models and perform spatial analyses. We have also developed specialized analysis tools to assist in the data and model analysis process. This approach provides an integrated framework for performing tasks such as comparing the model to data and understanding the relationship of model predictions to existing contaminant source locations and water supply wells. Our process of integrating GIS and numerical modeling results allows us to answer a wide variety of questions about our conceptual model design: - Which set of locations should be identified as contaminant sources based on known historical building operations
NASA Astrophysics Data System (ADS)
Jiang, C. X.; Cheng, J. P.; Li, F. C.
2015-01-01
This paper attempts to introduce a numerical simulation procedure to simulate water-entry problems influenced by turbulent drag-reducing additives in a viscous incompressible medium. Firstly we performed a numerical investigation on water-entry supercavities in water and turbulent drag-reducing solution at the impact velocity of 28.4 m/s to confirm the accuracy of the numerical method. Based on the verification, projectile entering water and turbulent drag-reducing solution at relatively high velocity of 142.7 m/s (phase transition is considered) is simulated. The cross viscosity equation was adopted to represent the shear-thinning characteristic of aqueous solution of drag-reducing additives. The configuration and dynamic characteristics of water entry supercavity, flow resistance were discussed respectively. It was obtained that the numerical simulation results are in consistence with experimental data. Numerical results show that the supercavity length in drag-reducing solution is larger than one in water and the velocity attenuates faster at high velocity than at low velocity; the influence of drag-reducing solution is more obvious at high impact velocity. Turbulent drag-reducing additives have the great potential for enhancement of supercavity.
Path Integrals and Exotic Options:. Methods and Numerical Results
NASA Astrophysics Data System (ADS)
Bormetti, G.; Montagna, G.; Moreni, N.; Nicrosini, O.
2005-09-01
In the framework of Black-Scholes-Merton model of financial derivatives, a path integral approach to option pricing is presented. A general formula to price path dependent options on multidimensional and correlated underlying assets is obtained and implemented by means of various flexible and efficient algorithms. As an example, we detail the case of Asian call options. The numerical results are compared with those obtained with other procedures used in quantitative finance and found to be in good agreement. In particular, when pricing at the money (ATM) and out of the money (OTM) options, path integral exhibits competitive performances.
Slump Flows inside Pipes: Numerical Results and Comparison with Experiments
NASA Astrophysics Data System (ADS)
Malekmohammadi, S.; Naccache, M. F.; Frigaard, I. A.; Martinez, D. M.
2008-07-01
In this work an analysis of the buoyancy-driven slumping flow inside a pipe is presented. This flow usually occurs when an oil well is sealed by a plug cementing process, where a cement plug is placed inside the pipe filled with a lower density fluid, displacing it towards the upper cylinder wall. Both the cement and the surrounding fluids have a non Newtonian behavior. The cement is viscoplastic and the surrounding fluid presents a shear thinning behavior. A numerical analysis was performed to evaluate the effects of some governing parameters on the slump length development. The conservation equations of mass and momentum were solved via a finite volume technique, using Fluent software (Ansys Inc.). The Volume of Fluid surface-tracking method was used to obtain the interface between the fluids and the slump length as a function of time. The results were obtained for different values of fluids densities differences, fluids rheology and pipe inclinations. The effects of these parameters on the interface shape and on the slump length versus time curve were analyzed. Moreover, the numerical results were compared to experimental ones, but some differences are observed, possibly due to chemical effects at the interface.
Synthetic jet parameter identification and numerical results validation
NASA Astrophysics Data System (ADS)
Sabbatini, Danilo; Rimasauskiene, Ruta; Matejka, Milan; Kurowski, Marcin; Wandowski, Tomasz; Malinowski, Paweł; Doerffer, Piotr
2012-06-01
The design of a synthetic jet requires a careful identification of the components' parameters, in order to be able to perform accurate numerical simulations, this identification must be done by mean of a series of measurements that, due to the small dimensions of the components, are required to be non-contact techniques. The activities described in this paper have been performed in the frame of the STA-DY-WI-CO project, whose purpose is the design of a synthetic jet and demonstrate its effectiveness and efficiency for a real application. To measure the energy saving, due to the synthetic jet effects on the separation, the increased performances of the profile must be compared to the energy absorbed by the actuator and the weight of the system. In design phase a series of actuators has being considered as well as a series of cavity layout, in order to obtain the most effective, efficient and durable package. The modal characteristics of piezoelectric component was assessed by means of tests performed with a 3D scanning laser vibrometer, measuring the frequency response to voltage excitation. Analyzed the effects of the parameters, and chosen components and layout, the system can be dimensioned by means of numeric simulations. The outcome of the simulation is the effect of the synthetic jet, in an assumed flow, for the selected profile. The numerical results on the field of the separated flow with recirculating area were validated by means of tests performed in an Eiffel type wind tunnel. The last test performed on the synthetic jet aims to understand the acoustic impact, noise measurements were performed to have full analysis and synthesis.
Mars-GRAM 2010: Additions and Resulting Improvements
NASA Technical Reports Server (NTRS)
Justh, Hilary L.; Burns, K. Lee
2013-01-01
factors. The adjustment factors generated by this process had to satisfy the gas law as well as the hydrostatic relation and are expressed as a function of height (z), Latitude (Lat) and areocentric solar longitude (Ls). The greatest adjustments are made at large optical depths such as tau greater than 1. The addition of the adjustment factors has led to better correspondence to TES Limb data from 0-60 km altitude as well as better agreement with MGS, ODY and MRO data at approximately 90-130 km altitude. Improved Mars-GRAM atmospheric simulations for various locations, times and dust conditions on Mars will be presented at the workshop session. The latest results validating Mars-GRAM 2010 versus Mars Climate Sounder data will also be presented. Mars-GRAM 2010 updates have resulted in improved atmospheric simulations which will be very important when beginning systems design, performance analysis, and operations planning for future aerocapture, aerobraking or landed missions to Mars.
Additional Results of Ice-Accretion Scaling at SLD Conditions
NASA Technical Reports Server (NTRS)
Bond, Thomas H. (Technical Monitor); Anderson, David N.; Tsao, Jen-Ching
2005-01-01
To determine scale velocity an additional similarity parameter is needed to supplement the Ruff scaling method. A Weber number based on water droplet MVD has been included in several studies because the effect of droplet splashing on ice accretion was believed to be important, particularly for SLD conditions. In the present study, ice shapes recorded at Appendix-C conditions and recent results at SLD conditions are reviewed to show that droplet diameter cannot be important to main ice shape, and for low airspeeds splashing does not appear to affect SLD ice shapes. Evidence is presented to show that while a supplementary similarity parameter probably has the form of a Weber number, it must be based on a length proportional to model size rather than MVD. Scaling comparisons were made between SLD reference conditions and Appendix-C scale conditions using this Weber number. Scale-to-reference model size ratios were 1:1.7 and 1:3.4. The reference tests used a 91-cm-chord NACA 0012 model with a velocity of approximately 50 m/s and an MVD of 160 m. Freezing fractions of 0.3, 0.4, and 0.5 were included in the study.
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.
Tsai, Pei-I; Hsu, Ching-Chi; Chen, San-Yuan; Wu, Tsung-Han; Huang, Chih-Chieh
2016-09-01
Traditional solid cages have been widely used in posterior lumbar interbody fusion (PLIF) surgery. However, solid cages significantly affect the loading mechanism of the human spine due to their extremely high structural stiffness. Previous studies proposed and investigated porous additive manufactured (AM) cages; however, their biomechanical performances were analyzed using oversimplified bone-implant numerical models. Thus, the aim of this study was to investigate the outer shape and inner porous structure of the AM cages. The outer shape of the AM cages was discovered using a simulation-based genetic algorithm; their inner porous structure was subsequently analyzed parametrically using T10-S1 multilevel spine models. Finally, six types of the AM cages, which were manufactured using selective laser melting, were tested to validate the numerical outcomes. The subsidence resistance of the optimum design was superior to the conventional cage designs. A porous AM cage with a pillar diameter of 0.4mm, a pillar angle of 40°, and a porosity of between 69% and 80% revealed better biomechanical performances. Both the numerical and experimental outcomes can help surgeons to understand the biomechanics of PLIF surgery combined with the use of AM cages. PMID:27392226
Small-Scale Spray Releases: Additional Aerosol Test Results
Schonewill, Philip P.; Gauglitz, Phillip A.; Kimura, Marcia L.; Brown, G. N.; Mahoney, Lenna A.; Tran, Diana N.; Burns, Carolyn A.; Kurath, Dean E.
2013-08-01
One of the events postulated in the hazard analysis at the Waste Treatment and Immobilization Plant (WTP) and other U.S. Department of Energy (DOE) nuclear facilities is a breach in process piping that produces aerosols with droplet sizes in the respirable range. The current approach for predicting the size and concentration of aerosols produced in a spray leak involves extrapolating from correlations reported in the literature. These correlations are based on results obtained from small engineered spray nozzles using pure liquids with Newtonian fluid behavior. The narrow ranges of physical properties on which the correlations are based do not cover the wide range of slurries and viscous materials that will be processed in the WTP and across processing facilities in the DOE complex. To expand the data set upon which the WTP accident and safety analyses were based, an aerosol spray leak testing program was conducted by Pacific Northwest National Laboratory (PNNL). PNNL’s test program addressed two key technical areas to improve the WTP methodology (Larson and Allen 2010). The first technical area was to quantify the role of slurry particles in small breaches where slurry particles may plug the hole and prevent high-pressure sprays. The results from an effort to address this first technical area can be found in Mahoney et al. (2012a). The second technical area was to determine aerosol droplet size distribution and total droplet volume from prototypic breaches and fluids, including sprays from larger breaches and sprays of slurries for which literature data are largely absent. To address the second technical area, the testing program collected aerosol generation data at two scales, commonly referred to as small-scale and large-scale. The small-scale testing and resultant data are described in Mahoney et al. (2012b) and the large-scale testing and resultant data are presented in Schonewill et al. (2012). In tests at both scales, simulants were used to mimic the
Large-Scale Spray Releases: Additional Aerosol Test Results
Daniel, Richard C.; Gauglitz, Phillip A.; Burns, Carolyn A.; Fountain, Matthew S.; Shimskey, Rick W.; Billing, Justin M.; Bontha, Jagannadha R.; Kurath, Dean E.; Jenks, Jeromy WJ; MacFarlan, Paul J.; Mahoney, Lenna A.
2013-08-01
One of the events postulated in the hazard analysis for the Waste Treatment and Immobilization Plant (WTP) and other U.S. Department of Energy (DOE) nuclear facilities is a breach in process piping that produces aerosols with droplet sizes in the respirable range. The current approach for predicting the size and concentration of aerosols produced in a spray leak event involves extrapolating from correlations reported in the literature. These correlations are based on results obtained from small engineered spray nozzles using pure liquids that behave as a Newtonian fluid. The narrow ranges of physical properties on which the correlations are based do not cover the wide range of slurries and viscous materials that will be processed in the WTP and in processing facilities across the DOE complex. To expand the data set upon which the WTP accident and safety analyses were based, an aerosol spray leak testing program was conducted by Pacific Northwest National Laboratory (PNNL). PNNL’s test program addressed two key technical areas to improve the WTP methodology (Larson and Allen 2010). The first technical area was to quantify the role of slurry particles in small breaches where slurry particles may plug the hole and prevent high-pressure sprays. The results from an effort to address this first technical area can be found in Mahoney et al. (2012a). The second technical area was to determine aerosol droplet size distribution and total droplet volume from prototypic breaches and fluids, including sprays from larger breaches and sprays of slurries for which literature data are mostly absent. To address the second technical area, the testing program collected aerosol generation data at two scales, commonly referred to as small-scale and large-scale testing. The small-scale testing and resultant data are described in Mahoney et al. (2012b), and the large-scale testing and resultant data are presented in Schonewill et al. (2012). In tests at both scales, simulants were used
Additional Results of Glaze Icing Scaling in SLD Conditions
NASA Technical Reports Server (NTRS)
Tsao, Jen-Ching
2016-01-01
New guidance of acceptable means of compliance with the super-cooled large drops (SLD) conditions has been issued by the U.S. Department of Transportation's Federal Aviation Administration (FAA) in its Advisory Circular AC 25-28 in November 2014. The Part 25, Appendix O is developed to define a representative icing environment for super-cooled large drops. Super-cooled large drops, which include freezing drizzle and freezing rain conditions, are not included in Appendix C. This paper reports results from recent glaze icing scaling tests conducted in NASA Glenn Icing Research Tunnel (IRT) to evaluate how well the scaling methods recommended for Appendix C conditions might apply to SLD conditions. The models were straight NACA 0012 wing sections. The reference model had a chord of 72 in. and the scale model had a chord of 21 in. Reference tests were run with airspeeds of 100 and 130.3 kn and with MVD's of 85 and 170 micron. Two scaling methods were considered. One was based on the modified Ruff method with scale velocity found by matching the Weber number WeL. The other was proposed and developed by Feo specifically for strong glaze icing conditions, in which the scale liquid water content and velocity were found by matching reference and scale values of the nondimensional water-film thickness expression and the film Weber number Wef. All tests were conducted at 0 deg AOA. Results will be presented for stagnation freezing fractions of 0.2 and 0.3. For nondimensional reference and scale ice shape comparison, a new post-scanning ice shape digitization procedure was developed for extracting 2-D ice shape profiles at any selected span-wise location from the high fidelity 3-D scanned ice shapes obtained in the IRT.
Busted Butte: Achieving the Objectives and Numerical Modeling Results
W.E. Soll; M. Kearney; P. Stauffer; P. Tseng; H.J. Turin; Z. Lu
2002-10-07
The Unsaturated Zone Transport Test (UZTT) at Busted Butte is a mesoscale field/laboratory/modeling investigation designed to address uncertainties associated with flow and transport in the UZ site-process models for Yucca Mountain. The UZTT test facility is located approximately 8 km southeast of the potential Yucca Mountain repository area. The UZTT was designed in two phases, to address five specific objectives in the UZ: the effect of heterogeneities, flow and transport (F&T) behavior at permeability contrast boundaries, migration of colloids , transport models of sorbing tracers, and scaling issues in moving from laboratory scale to field scale. Phase 1A was designed to assess the influence of permeability contrast boundaries in the hydrologic Calico Hills. Visualization of fluorescein movement , mineback rock analyses, and comparison with numerical models demonstrated that F&T are capillary dominated with permeability contrast boundaries distorting the capillary flow. Phase 1B was designed to assess the influence of fractures on F&T and colloid movement. The injector in Phase 1B was located at a fracture, while the collector, 30 cm below, was placed at what was assumed to be the same fracture. Numerical simulations of nonreactive (Br) and reactive (Li) tracers show the experimental data are best explained by a combination of molecular diffusion and advective flux. For Phase 2, a numerical model with homogeneous unit descriptions was able to qualitatively capture the general characteristics of the system. Numerical simulations and field observations revealed a capillary dominated flow field. Although the tracers showed heterogeneity in the test block, simulation using heterogeneous fields did not significantly improve the data fit over homogeneous field simulations. In terms of scaling, simulations of field tracer data indicate a hydraulic conductivity two orders of magnitude higher than measured in the laboratory. Simulations of Li, a weakly sorbing tracer
Numerical Results of Earth's Core Accumulation 3-D Modelling
NASA Astrophysics Data System (ADS)
Khachay, Yurie; Anfilogov, Vsevolod
2013-04-01
For a long time as a most convenient had been the model of mega impact in which the early forming of the Earth's core and mantle had been the consequence of formed protoplanet collision with the body of Mercurial mass. But all dynamical models of the Earth's accumulation and the estimations after the Pb-Pb system, lead to the conclusion that the duration of the planet accumulation was about 1 milliard years. But isotopic results after the W-Hf system testify about a very early (5-10) million years, dividing of the geochemical reservoirs of the core and mantle. In [1,3] it is shown, that the account of energy dissipating by the decay of short living radioactive elements and first of all Al,it is sufficient for heating even small bodies with dimensions about (50-100) km up to the iron melting temperature and can be realized a principal new differentiation mechanism. The inner parts of the melted preplanets can join and they are mainly of iron content, but the cold silicate fragments return to the supply zone. Only after the increasing of the gravitational radius, the growing area of the future core can save also the silicate envelope fragments. All existing dynamical accumulation models are constructed by using a spherical-symmetrical model. Hence for understanding the further planet evolution it is significant to trace the origin and evolution of heterogeneities, which occur on the planet accumulation stage. In that paper we are modeling distributions of temperature, pressure, velocity of matter flowing in a block of 3D- spherical body with a growing radius. The boundary problem is solved by the finite-difference method for the system of equations, which include equations which describe the process of accumulation, the Safronov equation, the equation of impulse balance, equation Navier-Stocks, equation for above litho static pressure and heat conductivity in velocity-pressure variables using the Businesque approach. The numerical algorithm of the problem solution in
Numerical calculations of high-altitude differential charging: Preliminary results
NASA Technical Reports Server (NTRS)
Laframboise, J. G.; Godard, R.; Prokopenko, S. M. L.
1979-01-01
A two dimensional simulation program was constructed in order to obtain theoretical predictions of floating potential distributions on geostationary spacecraft. The geometry was infinite-cylindrical with angle dependence. Effects of finite spacecraft length on sheath potential profiles can be included in an approximate way. The program can treat either steady-state conditions or slowly time-varying situations, involving external time scales much larger than particle transit times. Approximate, locally dependent expressions were used to provide space charge, density profiles, but numerical orbit-following is used to calculate surface currents. Ambient velocity distributions were assumed to be isotropic, beam-like, or some superposition of these.
NASA Technical Reports Server (NTRS)
Smalheer, C. V.
1973-01-01
The chemistry of lubricant additives is discussed to show what the additives are chemically and what functions they perform in the lubrication of various kinds of equipment. Current theories regarding the mode of action of lubricant additives are presented. The additive groups discussed include the following: (1) detergents and dispersants, (2) corrosion inhibitors, (3) antioxidants, (4) viscosity index improvers, (5) pour point depressants, and (6) antifouling agents.
Spurious frequencies as a result of numerical boundary treatments
NASA Technical Reports Server (NTRS)
Abarbanel, Saul; Gottlieb, David
1990-01-01
The stability theory for finite difference Initial Boundary-Value approximations to systems of hyperbolic partial differential equations states that the exclusion of eigenvalues and generalized eigenvalues is a sufficient condition for stability. The theory, however, does not discuss the nature of numerical approximations in the presence of such eigenvalues. In fact, as was shown previously, for the problem of vortex shedding by a 2-D cylinder in subsonic flow, stating boundary conditions in terms of the primitive (non-characteristic) variables may lead to such eigenvalues, causing perturbations that decay slowly in space and remain periodic time. Characteristic formulation of the boundary conditions avoided this problem. A more systematic study of the behavior of the (linearized) one-dimensional gas dynamic equations under various sets of oscillation-inducing legal boundary conditions is reported.
Numerical Studies of Magnetohydrodynamic Activity Resulting from Inductive Transients Final Report
Sovinec, Carl R.
2005-08-29
This report describes results from numerical studies of transients in magnetically confined plasmas. The work has been performed by University of Wisconsin graduate students James Reynolds and Giovanni Cone and by the Principal Investigator through support from contract DE-FG02-02ER54687, a Junior Faculty in Plasma Science award from the DOE Office of Science. Results from the computations have added significantly to our knowledge of magnetized plasma relaxation in the reversed-field pinch (RFP) and spheromak. In particular, they have distinguished relaxation activity expected in sustained configurations from transient effects that can persist over a significant fraction of the plasma discharge. We have also developed the numerical capability for studying electrostatic current injection in the spherical torus (ST). These configurations are being investigated as plasma confinement schemes in the international effort to achieve controlled thermonuclear fusion for environmentally benign energy production. Our numerical computations have been performed with the NIMROD code (http://nimrodteam.org) using local computing resources and massively parallel computing hardware at the National Energy Research Scientific Computing Center. Direct comparisons of simulation results for the spheromak with laboratory measurements verify the effectiveness of our numerical approach. The comparisons have been published in refereed journal articles by this group and by collaborators at Lawrence Livermore National Laboratory (see Section 4). In addition to the technical products, this grant has supported the graduate education of the two participating students for three years.
Trescott, Peter C.; Pinder, George Francis; Larson, S.P.
1976-01-01
The model will simulate ground-water flow in an artesian aquifer, a water-table aquifer, or a combined artesian and water-table aquifer. The aquifer may be heterogeneous and anisotropic and have irregular boundaries. The source term in the flow equation may include well discharge, constant recharge, leakage from confining beds in which the effects of storage are considered, and evapotranspiration as a linear function of depth to water. The theoretical development includes presentation of the appropriate flow equations and derivation of the finite-difference approximations (written for a variable grid). The documentation emphasizes the numerical techniques that can be used for solving the simultaneous equations and describes the results of numerical experiments using these techniques. Of the three numerical techniques available in the model, the strongly implicit procedure, in general, requires less computer time and has fewer numerical difficulties than do the iterative alternating direction implicit procedure and line successive overrelaxation (which includes a two-dimensional correction procedure to accelerate convergence). The documentation includes a flow chart, program listing, an example simulation, and sections on designing an aquifer model and requirements for data input. It illustrates how model results can be presented on the line printer and pen plotters with a program that utilizes the graphical display software available from the Geological Survey Computer Center Division. In addition the model includes options for reading input data from a disk and writing intermediate results on a disk.
Numerical Simulation of High Drag Reduction in a Turbulent Channel Flow with Polymer Additives
NASA Technical Reports Server (NTRS)
Dubief, Yves
2003-01-01
The addition of small amounts of long chain polymer molecules to wall-bounded flows can lead to dramatic drag reduction. Although this phenomenon has been known for about fifty years, the action of the polymers and its effect on turbulent structures are still unclear. Detailed experiments have characterized two distinct regimes (Warholic et al. 1999), which are referred to as low drag reduction (LDR) and high drag reduction (HDR). The first regime exhibits similar statistical trends as Newtonian flow: the log-law region of the mean velocity profile remains parallel to that of the Newtonian ow but its lower bound moves away from the wall and the upward shift of the log-region is a function of drag reduction, DR. Although streamwise fluctuations are increased and transverse ones are reduced, the shape of the rms velocity profiles is not qualitatively modified. At higher drag reductions, of the order of 40-50%, the ow enters the HDR regime for which the slope of the log-law is dramatically augmented and the Reynolds shear stress is small (Warholic et al. 1999; Ptasinski et al. 2001). The drag reduction is eventually bounded by a maximum drag reduction (MDR) (Virk & Mickley 1970) which is a function of the Reynolds number. While several experiments report mean velocity profiles very close to the empirical profile of Virk & Mickley (1970) for MDR conditions, the observations regarding the structure of turbulence can differ significantly. For instance, Warholic et al. (1999) measured a near-zero Reynolds shear stress, whereas a recent experiment (Ptasinski et al. 2001) shows evidence of non-negligible Reynolds stress in their MDR flow. To the knowledge of the authors, only the LDR regime has been documented in numerical simulations (Sureshkumar et al. 1997; Dimitropoulos et al. 1998; Min et al. 2001; Dubief & Lele 2001; Sibilla & Baron 2002). This paper discusses the simulation of polymer drag reduced channel ow at HDR using the FENE-P (Finite Elastic non
Hurtado, Pablo I; Garrido, Pedro L
2010-04-01
Most systems, when pushed out of equilibrium, respond by building up currents of locally conserved observables. Understanding how microscopic dynamics determines the averages and fluctuations of these currents is one of the main open problems in nonequilibrium statistical physics. The additivity principle is a theoretical proposal that allows to compute the current distribution in many one-dimensional nonequilibrium systems. Using simulations, we validate this conjecture in a simple and general model of energy transport, both in the presence of a temperature gradient and in canonical equilibrium. In particular, we show that the current distribution displays a Gaussian regime for small current fluctuations, as prescribed by the central limit theorem, and non-Gaussian (exponential) tails for large current deviations, obeying in all cases the Gallavotti-Cohen fluctuation theorem. In order to facilitate a given current fluctuation, the system adopts a well-defined temperature profile different from that of the steady state and in accordance with the additivity hypothesis predictions. System statistics during a large current fluctuation is independent of the sign of the current, which implies that the optimal profile (as well as higher-order profiles and spatial correlations) are invariant upon current inversion. We also demonstrate that finite-time joint fluctuations of the current and the profile are well described by the additivity functional. These results suggest the additivity hypothesis as a general and powerful tool to compute current distributions in many nonequilibrium systems. PMID:20481672
Zargarian, A; Esfahanian, M; Kadkhodapour, J; Ziaei-Rad, S
2016-03-01
In this paper, the effects of cell geometry and relative density on the high-cycle fatigue behavior of Titanium scaffolds produced by selective laser melting and electron beam melting techniques were numerically investigated by finite element analysis. The regular titanium lattice samples with three different unit cell geometries, namely, diamond, rhombic dodecahedron and truncated cuboctahedron, and the relative density range of 0.1-0.3 were analyzed under uniaxial cyclic compressive loading. A failure event based algorithm was employed to simulate fatigue failure in the cellular material. Stress-life approach was used to model fatigue failure of both bulk (struts) and cellular material. The predicted fatigue life and the damage pattern of all three structures were found to be in good agreement with the experimental fatigue investigations published in the literature. The results also showed that the relationship between fatigue strength and cycles to failure obeyed the power law. The coefficient of power function was shown to depend on relative density, geometry and fatigue properties of the bulk material while the exponent was only dependent on the fatigue behavior of the bulk material. The results also indicated the failure surface at an angle of 45° to the loading direction. PMID:26706539
Sediment Pathways Across Trench Slopes: Results From Numerical Modeling
NASA Astrophysics Data System (ADS)
Cormier, M. H.; Seeber, L.; McHugh, C. M.; Fujiwara, T.; Kanamatsu, T.; King, J. W.
2015-12-01
Until the 2011 Mw9.0 Tohoku earthquake, the role of earthquakes as agents of sediment dispersal and deposition at erosional trenches was largely under-appreciated. A series of cruises carried out after the 2011 event has revealed a variety of unsuspected sediment transport mechanisms, such as tsunami-triggered sheet turbidites, suggesting that great earthquakes may in fact be important agents for dispersing sediments across trench slopes. To complement these observational data, we have modeled the pathways of sediments across the trench slope based on bathymetric grids. Our approach assumes that transport direction is controlled by slope azimuth only, and ignores obstacles smaller than 0.6-1 km; these constraints are meant to approximate the behavior of turbidites. Results indicate that (1) most pathways issued from the upper slope terminate near the top of the small frontal wedge, and thus do not reach the trench axis; (2) in turn, sediments transported to the trench axis are likely derived from the small frontal wedge or from the subducting Pacific plate. These results are consistent with the stratigraphy imaged in seismic profiles, which reveals that the slope apron does not extend as far as the frontal wedge, and that the thickness of sediments at the trench axis is similar to that of the incoming Pacific plate. We further applied this modeling technique to the Cascadia, Nankai, Middle-America, and Sumatra trenches. Where well-defined canyons carve the trench slopes, sediments from the upper slope may routinely reach the trench axis (e.g., off Costa Rica and Cascadia). In turn, slope basins that are isolated from the canyons drainage systems must mainly accumulate locally-derived sediments. Therefore, their turbiditic infill may be diagnostic of seismic activity only - and not from storm or flood activity. If correct, this would make isolated slope basins ideal targets for paleoseismological investigation.
Guo, Hongsheng; Liu, Fengshan; Smallwood, Gregory J.; Guelder, OEmer L.
2006-04-15
The influence of hydrogen addition to the fuel of an atmosphere pressure coflow laminar ethylene-air diffusion flame on soot formation was studied by numerical simulation. A detailed gas-phase reaction mechanism, which includes aromatic chemistry up to four rings, and complex thermal and transport properties were used. The fully coupled elliptic governing equations were solved. The interactions between soot and gas-phase chemistry were taken into account. Radiation heat transfer from CO{sub 2}, CO, H{sub 2}O, and soot was calculated using the discrete-ordinates method coupled to a statistical narrow-band-correlated K-based wide-band model. The predicted results were compared with the available experimental data and analyzed. It is indicated that the addition of hydrogen to the fuel in an ethylene-air diffusion flame suppresses soot formation through the effects of dilution and chemistry. This result is in agreement with available experiments. The simulations further suggest that the chemically inhibiting effect of hydrogen addition on soot formation is due to the decrease of hydrogen atom concentration in soot surface growth regions and higher concentration of molecular hydrogen in the lower flame region. (author)
Influence of Ar addition on ozone generation in a non-thermal plasma—a numerical investigation
NASA Astrophysics Data System (ADS)
Chen, Hsin Liang; Lee, How Ming; Chen, Shiaw Huei; Wei, Ta Chin; Been Chang, Moo
2010-10-01
A numerical model based on a dielectric barrier discharge is developed in this study to investigate the influence of Ar addition on ozone generation. The simulation results show good agreement with the experimental data, confirming the validity of the numerical model. The mechanisms regarding how the Ar addition affects ozone generation are investigated with the assistance of a numerical simulation by probing into the following two questions, (1) why the ozone concentration just slightly decreases in the low specific input energy (SIE, the ratio of discharge power to gas flow rate) region even if the inlet O2 concentration is substantially decreased and (2) why the variation of the increased rate of ozone concentration with SIE (i.e. the variation in the slope of ozone concentration versus SIE) is more significant for an O2/Ar mixture plasma. As SIE is relatively low, ozone decomposition through electron-impact and radical attack reactions is less significant because of low ozone concentration and gas temperature. Therefore, the ozone concentration depends mainly on the amount of oxygen atoms generated. The simulation results indicate that the amount of oxygen atoms generated per electronvolt for Ar concentrations of 0%, 10%, 30%, 50% and 80% are 0.178, 0.174, 0.169, 0.165 and 0.166, respectively, explaining why the ozone concentration does not decrease linearly with the inlet O2 concentration in the low SIE region. On the other hand, the simulation results show that increasing Ar concentration would lead to a lower reduced field and a higher gas temperature. The former would lead to an increase in the rate constant of e + O3 → e + O + O2 while the latter would result in a decrease in the rate constant of O + O2 + M → O3 + M and an increase in that of O3 + O → 2O2. The changes in the rate constants of these reactions would have a negative effect on ozone generation, which is the rationale for the second question.
Numerical study of the effect of water addition on gas explosion.
Liang, Yuntao; Zeng, Wen
2010-02-15
Through amending the SENKIN code of CHEMKIN III chemical kinetics package, a computational model of gas explosion in a constant volume bomb was built, and the detailed reaction mechanism (GRI-Mech 3.0) was adopted. The mole fraction profiles of reactants, some selected free radicals and catastrophic gases in the process of gas explosion were analyzed by this model. Furthermore, through the sensitivity analysis of the reaction mechanism of gas explosion, the dominant reactions that affect gas explosion and the formation of catastrophic gases were found out. At the same time, the inhibition mechanisms of water on gas explosion and the formation of catastrophic gases were analyzed. The results show that the induced explosion time is prolonged, and the mole fractions of reactant species such as CH(4), O(2) and catastrophic gases such as CO, CO(2) and NO are decreased as water is added to the mixed gas. With the water fraction in the mixed gas increasing, the sensitivities of the dominant reactions contributing to CH(4), CO(2) are decreased and the sensitivity coefficients of CH(4), CO and NO mole fractions are also decreased. The inhibition of gas explosion with water addition can be ascribed to the significant decrease of H, O and OH in the process of gas explosion due to the water presence. PMID:19811873
O'Brien, James Edward; Sohal, Manohar Singh; Huff, George Albert
2002-08-01
A combined experimental and numerical investigation is under way to investigate heat transfer enhancement techniques that may be applicable to large-scale air-cooled condensers such as those used in geothermal power applications. The research is focused on whether air-side heat transfer can be improved through the use of finsurface vortex generators (winglets,) while maintaining low heat exchanger pressure drop. A transient heat transfer visualization and measurement technique has been employed in order to obtain detailed distributions of local heat transfer coefficients on model fin surfaces. Pressure drop measurements have also been acquired in a separate multiple-tube row apparatus. In addition, numerical modeling techniques have been developed to allow prediction of local and average heat transfer for these low-Reynolds-number flows with and without winglets. Representative experimental and numerical results presented in this paper reveal quantitative details of local fin-surface heat transfer in the vicinity of a circular tube with a single delta winglet pair downstream of the cylinder. The winglets were triangular (delta) with a 1:2 height/length aspect ratio and a height equal to 90% of the channel height. Overall mean fin-surface Nusselt-number results indicate a significant level of heat transfer enhancement (average enhancement ratio 35%) associated with the deployment of the winglets with oval tubes. Pressure drop measurements have also been obtained for a variety of tube and winglet configurations using a single-channel flow apparatus that includes four tube rows in a staggered array. Comparisons of heat transfer and pressure drop results for the elliptical tube versus a circular tube with and without winglets are provided. Heat transfer and pressure-drop results have been obtained for flow Reynolds numbers based on channel height and mean flow velocity ranging from 700 to 6500.
Numerical prediction of freezing fronts in cryosurgery: comparison with experimental results.
Fortin, André; Belhamadia, Youssef
2005-08-01
Recent developments in scientific computing now allow to consider realistic applications of numerical modelling to medicine. In this work, a numerical method is presented for the simulation of phase change occurring in cryosurgery applications. The ultimate goal of these simulations is to accurately predict the freezing front position and the thermal history inside the ice ball which is essential to determine if cancerous cells have been completely destroyed. A semi-phase field formulation including blood flow considerations is employed for the simulations. Numerical results are enhanced by the introduction of an anisotropic remeshing strategy. The numerical procedure is validated by comparing the predictions of the model with experimental results. PMID:16298846
NASA Astrophysics Data System (ADS)
Aleksandrova, A. G.; Galushina, T. Yu.
2015-12-01
The paper describes the software package developed for the numerical simulation of the breakups of natural and artificial objects and algorithms on which it is based. A new software "Numerical model of breakups" includes models of collapse of the spacecraft (SC) as a result of the explosion and collision as well as two models of the explosion of an asteroid.
NASA Technical Reports Server (NTRS)
Smutek, C.; Bontoux, P.; Roux, B.; Schiroky, G. H.; Hurford, A. C.
1985-01-01
The results of a three-dimensional numerical simulation of Boussinesq free convection in a horizontal differentially heated cylinder are presented. The computation was based on a Samarskii-Andreyev scheme (described by Leong, 1981) and a false-transient advancement in time, with vorticity, velocity, and temperature as dependent variables. Solutions for velocity and temperature distributions were obtained for Rayleigh numbers (based on the radius) Ra = 74-18,700, thus covering the core- and boundary-layer-driven regimes. Numerical solutions are compared with asymptotic analytical solutions and experimental data. The numerical results well represent the complex three-dimensional flows found experimentally.
Manzini, Gianmarco; Cangiani, Andrea; Sutton, Oliver
2014-10-02
This document presents the results of a set of preliminary numerical experiments using several possible conforming virtual element approximations of the convection-reaction-diffusion equation with variable coefficients.
Comparison of results of experimental research with numerical calculations of a model one-sided seal
NASA Astrophysics Data System (ADS)
Joachimiak, Damian; Krzyślak, Piotr
2015-06-01
Paper presents the results of experimental and numerical research of a model segment of a labyrinth seal for a different wear level. The analysis covers the extent of leakage and distribution of static pressure in the seal chambers and the planes upstream and downstream of the segment. The measurement data have been compared with the results of numerical calculations obtained using commercial software. Based on the flow conditions occurring in the area subjected to calculations, the size of the mesh defined by parameter y+ has been analyzed and the selection of the turbulence model has been described. The numerical calculations were based on the measurable thermodynamic parameters in the seal segments of steam turbines. The work contains a comparison of the mass flow and distribution of static pressure in the seal chambers obtained during the measurement and calculated numerically in a model segment of the seal of different level of wear.
Height of burst explosions: a comparative study of numerical and experimental results
NASA Astrophysics Data System (ADS)
Omang, M.; Christensen, S. O.; Børve, S.; Trulsen, J.
2009-06-01
In the current work, we use the Constant Volume model and the numerical method, Regularized Smoothed Particle Hydrodynamics (RSPH) to study propagation and reflection of blast waves from detonations of the high explosives C-4 and TNT. The results from simulations of free-field TNT explosions are compared to previously published data, and good agreement is found. Measurements from height of burst tests performed by the Norwegian Defence Estates Agency are used to compare against numerical simulations. The results for shock time of arrival and the pressure levels are well represented by the numerical results. The results are also found to be in good agreement with results from a commercially available code. The effect of allowing different ratios of specific heat capacities in the explosive products are studied. We also evaluate the effect of changing the charge shape and height of burst on the triple point trajectory.
ERIC Educational Resources Information Center
Iler, H. Darrell; Brown, Amber; Landis, Amanda; Schimke, Greg; Peters, George
2014-01-01
A numerical analysis of the free radical addition polymerization system is described that provides those teaching polymer, physical, or advanced organic chemistry courses the opportunity to introduce students to numerical methods in the context of a simple but mathematically stiff chemical kinetic system. Numerical analysis can lead students to an…
NASA Astrophysics Data System (ADS)
Wojcik, J.; Powalowski, T.; Trawinski, Z.
2008-02-01
The aim of this paper is to compare the results of the mathematical modeling and experimental results of the ultrasonic waves scattering in the inhomogeneous dissipative medium. The research was carried out for an artery model (a pipe made of a latex), with internal diameter of 5 mm and wall thickness of 1.25 mm. The numerical solver was created for calculation of the fields of ultrasonic beams and scattered fields under different boundary conditions, different angles and transversal displacement of ultrasonic beams with respect to the position of the arterial wall. The investigations employed the VED ultrasonic apparatus. The good agreement between the numerical calculation and experimental results was obtained.
Dameron, O; Gibaud, B; Morandi, X
2004-06-01
The human cerebral cortex anatomy describes the brain organization at the scale of gyri and sulci. It is used as landmarks for neurosurgery as well as localization support for functional data analysis or inter-subject data comparison. Existing models of the cortex anatomy either rely on image labeling but fail to represent variability and structural properties or rely on a conceptual model but miss the inner 3D nature and relations of anatomical structures. This study was therefore conducted to propose a model of sulco-gyral anatomy for the healthy human brain. We hypothesized that both numeric knowledge (i.e., image-based) and symbolic knowledge (i.e., concept-based) have to be represented and coordinated. In addition, the representation of this knowledge should be application-independent in order to be usable in various contexts. Therefore, we devised a symbolic model describing specialization, composition and spatial organization of cortical anatomical structures. We also collected numeric knowledge such as 3D models of shape and shape variation about cortical anatomical structures. For each numeric piece of knowledge, a companion file describes the concept it refers to and the nature of the relationship. Demonstration software performs a mapping between the numeric and the symbolic aspects for browsing the knowledge base. PMID:15118839
NASA Technical Reports Server (NTRS)
Kwon, J. H.
1977-01-01
Numerical solution of two dimensional, time dependent, compressible viscous Navier-Stokes equations about arbitrary bodies was treated using density gradients as additional dependent variables. Thus, six dependent variables were computed with the SOR iteration method. Besides formulation for pressure gradient terms, a formulation for computing the body density was presented. To approximate the governing equations, an implicit finite difference method was employed. In computing the solution for the flow about a circular cylinder, a problem arose near the wall at both stagnation points. Thus, computations with various conditions were tried to examine the problem. Also, computations with and without formulations are compared. The flow variables were computed on 37 by 40 field first, then on an 81 by 40 field.
The Modern U.S. High School Astronomy Course, Its Status and Makeup II: Additional Results
ERIC Educational Resources Information Center
Krumenaker, Larry
2009-01-01
A postal survey of high school astronomy teachers strongly confirms many results of an earlier electronic survey. Additional and new results include a measure of the level of inquiry (more structured inquiry and teacher-led) in the classroom as well as data showing that more emphasis is given to traditional topics than to contemporary astronomy…
Numerical modeling of on-orbit propellant motion resulting from an impulsive acceleration
NASA Technical Reports Server (NTRS)
Aydelott, John C.; Mjolsness, Raymond C.; Torrey, Martin D.; Hochstein, John I.
1987-01-01
In-space docking and separation maneuvers of spacecraft that have large fluid mass fractions may cause undesirable spacecraft motion in response to the impulsive-acceleration-induced fluid motion. An example of this potential low gravity fluid management problem arose during the development of the shuttle/Centaur vehicle. Experimentally verified numerical modeling techniques were developed to establish the propellant dynamics, and subsequent vehicle motion, associated with the separation of the Centaur vehicle from the shuttle orbiter cargo bay. Although the shuttle/Centaur development activity was suspended, the numerical modeling techniques are available to predict on-orbit liquid motion resulting from impulsive accelerations for other missions and spacecraft.
Lee, Chia-Ching; Lin, Shang-Chih; Wu, Shu-Wei; Li, Yu-Ching; Fu, Ping-Yuen
2012-10-01
The holding power of the bone-screw interfaces is one of the key factors in the clinical performance of screw design. The value of the holding power can be experimentally measured by pullout tests. Historically, some researchers have used the finite-element method to simulate the holding power of the different screws. Among them, however, the assumed displacement of the screw withdrawal is unreasonably small (about 0.005-1.0 mm). In addition, the chosen numerical indices are quite different, including maximum stress, strain energy, and reaction force. This study systematically uses dental, traumatic, and spinal screws to experimentally measure and numerically simulate their bone-purchasing ability within the synthetic bone. The testing results (pullout displacement and holding power) and numerical indices (maximum stress, total strain energy, and reaction forces) are chosen to calculate their correlation coefficients. The pullout displacement is divided into five regions from initial to final withdrawal. The experimental results demonstrate that the pullout displacement consistently occurs at the final region (0.6-1.6 mm) and is significantly higher than the assumed value of the literature studies. For all screw groups, the measured holding power within the initial region is not highly or even negatively correlated with the experimental and numerical results within the final region. The observation from the simulative results shows the maximum stress only reflects the loads concentrated at some local site(s) and is the least correlated to the measured holding power. Comparatively, both energy and force are more global indices to correlate with the gross failure at the bone-screw interfaces. However, the energy index is not suitable for the screw groups with rather tiny threads compared with the other specifications. In conclusion, the underestimated displacement leads to erroneous results in the screw-pullout simulation. Among three numerical indices the reaction
Naghieh, S; Karamooz Ravari, M R; Badrossamay, M; Foroozmehr, E; Kadkhodaei, M
2016-06-01
In recent years, thanks to additive manufacturing technology, researchers have gone towards the optimization of bone scaffolds for the bone reconstruction. Bone scaffolds should have appropriate biological as well as mechanical properties in order to play a decisive role in bone healing. Since the fabrication of scaffolds is time consuming and expensive, numerical methods are often utilized to simulate their mechanical properties in order to find a nearly optimum one. Finite element analysis is one of the most common numerical methods that is used in this regard. In this paper, a parametric finite element model is developed to assess the effects of layers penetration׳s effect on inter-layer adhesion, which is reflected on the mechanical properties of bone scaffolds. To be able to validate this model, some compression test specimens as well as bone scaffolds are fabricated with biocompatible and biodegradable poly lactic acid using fused deposition modeling. All these specimens are tested in compression and their elastic modulus is obtained. Using the material parameters of the compression test specimens, the finite element analysis of the bone scaffold is performed. The obtained elastic modulus is compared with experiment indicating a good agreement. Accordingly, the proposed finite element model is able to predict the mechanical behavior of fabricated bone scaffolds accurately. In addition, the effect of post-heating of bone scaffolds on their elastic modulus is investigated. The results demonstrate that the numerically predicted elastic modulus of scaffold is closer to experimental outcomes in comparison with as-built samples. PMID:26874065
Raghavan, Narendran; Dehoff, Ryan; Pannala, Sreekanth; Simunovic, Srdjan; Kirka, Michael; Turner, John; Carlson, Neil; Babu, Sudarsanam S.
2016-04-26
The fabrication of 3-D parts from CAD models by additive manufacturing (AM) is a disruptive technology that is transforming the metal manufacturing industry. The correlation between solidification microstructure and mechanical properties has been well understood in the casting and welding processes over the years. This paper focuses on extending these principles to additive manufacturing to understand the transient phenomena of repeated melting and solidification during electron beam powder melting process to achieve site-specific microstructure control within a fabricated component. In this paper, we have developed a novel melt scan strategy for electron beam melting of nickel-base superalloy (Inconel 718) andmore » also analyzed 3-D heat transfer conditions using a parallel numerical solidification code (Truchas) developed at Los Alamos National Laboratory. The spatial and temporal variations of temperature gradient (G) and growth velocity (R) at the liquid-solid interface of the melt pool were calculated as a function of electron beam parameters. By manipulating the relative number of voxels that lie in the columnar or equiaxed region, the crystallographic texture of the components can be controlled to an extent. The analysis of the parameters provided optimum processing conditions that will result in columnar to equiaxed transition (CET) during the solidification. Furthermore, the results from the numerical simulations were validated by experimental processing and characterization thereby proving the potential of additive manufacturing process to achieve site-specific crystallographic texture control within a fabricated component.« less
Field Testing of a Wet FGD Additive for Enhanced Mercury Control - Pilot-Scale Test Results
Gary M. Blythe
2006-03-01
Texas Lignite Flue Gas; Task 3 - Full-scale FGD Additive Testing in High Sulfur Eastern Bituminous Flue Gas; Task 4 - Pilot Wet Scrubber Additive Tests at Yates; and Task 5 - Full-scale Additive Tests at Plant Yates. This topical report presents the results from the Task 2 and Task 4 pilot-scale additive tests. The Task 3 and Task 5 full-scale additive tests will be conducted later in calendar year 2006.
Improving the trust in results of numerical simulations and scientific data analytics
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
Additional results on space environmental effects on polymer matrix composites: Experiment A0180
NASA Technical Reports Server (NTRS)
Tennyson, R. C.
1992-01-01
Additional experimental results on the atomic oxygen erosion of boron, Kevlar, and graphite fiber reinforced epoxy matrix composites are presented. Damage of composite laminates due to micrometeoroid/debris impacts is also examined with particular emphasis on the relationship between damage area and actual hole size due to particle penetration. Special attention is given to one micrometeoroid impact on an aluminum base plate which resulted in ejecta visible on an adjoining vertical flange structure.
Dragna, Didier; Blanc-Benon, Philippe; Poisson, Franck
2014-03-01
Results from outdoor acoustic measurements performed in a railway site near Reims in France in May 2010 are compared to those obtained from a finite-difference time-domain solver of the linearized Euler equations. During the experiments, the ground profile and the different ground surface impedances were determined. Meteorological measurements were also performed to deduce mean vertical profiles of wind and temperature. An alarm pistol was used as a source of impulse signals and three microphones were located along a propagation path. The various measured parameters are introduced as input data into the numerical solver. In the frequency domain, the numerical results are in good accordance with the measurements up to a frequency of 2 kHz. In the time domain, except a time shift, the predicted waveforms match the measured waveforms with a close agreement. PMID:24606253
Forecasting Energy Market Contracts by Ambit Processes: Empirical Study and Numerical Results
Di Persio, Luca; Marchesan, Michele
2014-01-01
In the present paper we exploit the theory of ambit processes to develop a model which is able to effectively forecast prices of forward contracts written on the Italian energy market. Both short-term and medium-term scenarios are considered and proper calibration procedures as well as related numerical results are provided showing a high grade of accuracy in the obtained approximations when compared with empirical time series of interest. PMID:27437500
Chaotic scattering in an open vase-shaped cavity: Topological, numerical, and experimental results
NASA Astrophysics Data System (ADS)
Novick, Jaison Allen
point to each "detector point". We then construct the wave function directly from these classical trajectories using the two-dimensional WKB approximation. The wave function is Fourier Transformed using a Fast Fourier Transform algorithm resulting in a spectrum in which each peak corresponds to an interpolated trajectory. Our predictions are based on an imagined experiment that uses microwave propagation within an electromagnetic waveguide. Such an experiment exploits the fact that under suitable conditions both Maxwell's Equations and the Schrodinger Equation can be reduced to the Helmholtz Equation. Therefore, our predictions, while compared to the electromagnetic experiment, contain information about the quantum system. Identifying peaks in the transmission spectrum with chaotic trajectories will allow for an additional experimental verification of the intermediate recursive structure. Finally, we summarize our results and discuss possible extensions of this project.
Nonlinearities of waves propagating over a mild-slope beach: laboratory and numerical results
NASA Astrophysics Data System (ADS)
Rocha, Mariana V. L.; Michallet, Hervé; Silva, Paulo A.; Cienfuegos, Rodrigo
2014-05-01
As surface gravity waves propagate from deeper waters to the shore, their shape changes, primarily due to nonlinear wave interactions and further on due to breaking. The nonlinear effects amplify the higher harmonics and cause the oscillatory flow to transform from nearly sinusoidal in deep water, through velocity-skewed in the shoaling zone, to velocity asymmetric in the inner-surf and swash zones. In addition to short-wave nonlinearities, the presence of long waves and wave groups also results in a supplementary wave-induced velocity and influences the short-waves. Further, long waves can themselves contribute to velocity skewness and asymmetry at low frequencies, particularly for very dissipative mild-slope beach profiles, where long wave shoaling and breaking can also occur. The Hydralab-IV GLOBEX experiments were performed in a 110-m-long flume, with a 1/80 rigid-bottom slope and allowed the acquisition of high-resolution free-surface elevation and velocity data, obtained during 90-min long simulations of random and bichromatic wave conditions, and also of a monochromatic long wave (Ruessink et al., Proc. Coastal Dynamics, 2013). The measurements are compared to numerical results obtained with the SERR-1D Boussinesq-type model, which is designed to reproduce the complex dynamics of high-frequency wave propagation, including the energy transfer mechanisms that enhance infragravity-wave generation. The evolution of skewness and asymmetry along the beach profile until the swash zone is analyzed, relatively to that of the wave groupiness and long wave propagation. Some particularities of bichromatic wave groups are further investigated, such as partially-standing long-wave patterns and short-wave reformation after the first breakpoint, which is seen to influence particularly the skewness trends. Decreased spectral width (for random waves) and increased modulation (for bichromatic wave groups) are shown to enhance energy transfers between super- and sub
NASA Astrophysics Data System (ADS)
Kitaygorsky, J.; Amburgey, C.; Elliott, J. R.; Fisher, R.; Perala, R. A.
A broadband (100 MHz-1.2 GHz) plane wave electric field source was used to evaluate electric field penetration inside a simplified Boeing 707 aircraft model with a finite-difference time-domain (FDTD) method using EMA3D. The role of absorption losses inside the simplified aircraft was investigated. It was found that, in this frequency range, none of the cavities inside the Boeing 707 model are truly reverberant when frequency stirring is applied, and a purely statistical electromagnetics approach cannot be used to predict or analyze the field penetration or shielding effectiveness (SE). Thus it was our goal to attempt to understand the nature of losses in such a quasi-statistical environment by adding various numbers of absorbing objects inside the simplified aircraft and evaluating the SE, decay-time constant τ, and quality factor Q. We then compare our numerical results with experimental results obtained by D. Mark Johnson et al. on a decommissioned Boeing 707 aircraft.
Some numerical simulation results of swirling flow in d.c. plasma torch
NASA Astrophysics Data System (ADS)
Felipini, C. L.; Pimenta, M. M.
2015-03-01
We present and discuss some results of numerical simulation of swirling flow in d.c. plasma torch, obtained with a two-dimensional mathematical model (MHD model) which was developed to simulate the phenomena related to the interaction between the swirling flow and the electric arc in a non-transferred arc plasma torch. The model was implemented in a computer code based on the Finite Volume Method (FVM) to enable the numerical solution of the governing equations. For the study, cases were simulated with different operating conditions (gas flow rate; swirl number). Some obtained results were compared to the literature and have proved themselves to be in good agreement in most part of computational domain regions. The numerical simulations performed with the computer code enabled the study of the behaviour of the flow in the plasma torch and also study the effects of different swirl numbers on temperature and axial velocity of the plasma flow. The results demonstrated that the developed model is suitable to obtain a better understanding of the involved phenomena and also for the development and optimization of plasma torches.
A method for data handling numerical results in parallel OpenFOAM simulations
NASA Astrophysics Data System (ADS)
Anton, Alin; Muntean, Sebastian
2015-12-01
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®[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.
A method for data handling numerical results in parallel OpenFOAM simulations
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.
NASA Technical Reports Server (NTRS)
Pline, Alexander D.; Werner, Mark P.; Hsieh, Kwang-Chung
1991-01-01
The Surface Tension Driven Convection Experiment (STDCE) is a Space Transportation System flight experiment to study both transient and steady thermocapillary fluid flows aboard the United States Microgravity Laboratory-1 (USML-1) Spacelab mission planned for June, 1992. One of the components of data collected during the experiment is a video record of the flow field. This qualitative data is then quantified using an all electric, two dimensional Particle Image Velocimetry (PIV) technique called Particle Displacement Tracking (PDT), which uses a simple space domain particle tracking algorithm. Results using the ground based STDCE hardware, with a radiant flux heating mode, and the PDT system are compared to numerical solutions obtained by solving the axisymmetric Navier Stokes equations with a deformable free surface. The PDT technique is successful in producing a velocity vector field and corresponding stream function from the raw video data which satisfactorily represents the physical flow. A numerical program is used to compute the velocity field and corresponding stream function under identical conditions. Both the PDT system and numerical results were compared to a streak photograph, used as a benchmark, with good correlation.
NASA Technical Reports Server (NTRS)
Pline, Alexander D.; Wernet, Mark P.; Hsieh, Kwang-Chung
1991-01-01
The Surface Tension Driven Convection Experiment (STDCE) is a Space Transportation System flight experiment to study both transient and steady thermocapillary fluid flows aboard the United States Microgravity Laboratory-1 (USML-1) Spacelab mission planned for June, 1992. One of the components of data collected during the experiment is a video record of the flow field. This qualitative data is then quantified using an all electric, two dimensional Particle Image Velocimetry (PIV) technique called Particle Displacement Tracking (PDT), which uses a simple space domain particle tracking algorithm. Results using the ground based STDCE hardware, with a radiant flux heating mode, and the PDT system are compared to numerical solutions obtained by solving the axisymmetric Navier Stokes equations with a deformable free surface. The PDT technique is successful in producing a velocity vector field and corresponding stream function from the raw video data which satisfactorily represents the physical flow. A numerical program is used to compute the velocity field and corresponding stream function under identical conditions. Both the PDT system and numerical results were compared to a streak photograph, used as a benchmark, with good correlation.
Wave interpretation of numerical results for the vibration in thin conical shells
NASA Astrophysics Data System (ADS)
Ni, Guangjian; Elliott, Stephen J.
2014-05-01
The dynamic behaviour of thin conical shells can be analysed using a number of numerical methods. Although the overall vibration response of shells has been thoroughly studied using such methods, their physical insight is limited. The purpose of this paper is to interpret some of these numerical results in terms of waves, using the wave finite element, WFE, method. The forced response of a thin conical shell at different frequencies is first calculated using the dynamic stiffness matrix method. Then, a wave finite element analysis is used to calculate the wave properties of the shell, in terms of wave type and wavenumber, as a function of position along it. By decomposing the overall results from the dynamic stiffness matrix analysis, the responses of the shell can then be interpreted in terms of wave propagation. A simplified theoretical analysis of the waves in the thin conical shell is also presented in terms of the spatially-varying ring frequency, which provides a straightforward interpretation of the wave approach. The WFE method provides a way to study the types of wave that travel in thin conical shell structures and to decompose the response of the numerical models into the components due to each of these waves. In this way the insight provided by the wave approach allows us to analyse the significance of different waves in the overall response and study how they interact, in particular illustrating the conversion of one wave type into another along the length of the conical shell.
Recent Analytical and Numerical Results for The Navier-Stokes-Voigt Model and Related Models
NASA Astrophysics Data System (ADS)
Larios, Adam; Titi, Edriss; Petersen, Mark; Wingate, Beth
2010-11-01
The equations which govern the motions of fluids are notoriously difficult to handle both mathematically and computationally. Recently, a new approach to these equations, known as the Voigt-regularization, has been investigated as both a numerical and analytical regularization for the 3D Navier-Stokes equations, the Euler equations, and related fluid models. This inviscid regularization is related to the alpha-models of turbulent flow; however, it overcomes many of the problems present in those models. I will discuss recent work on the Voigt-regularization, as well as a new criterion for the finite-time blow-up of the Euler equations based on their Voigt-regularization. Time permitting, I will discuss some numerical results, as well as applications of this technique to the Magnetohydrodynamic (MHD) equations and various equations of ocean dynamics.
Van den Schoor, F; Norman, F; Vandebroek, L; Verplaetsen, F; Berghmans, J
2009-05-30
In this study the auto-ignition limit of ammonia/methane/air mixtures is calculated based upon a perfectly stirred reactor model with convective heat transfer. The results of four different reaction mechanisms are compared with existing experimental data at an initial temperature of 723 K with ammonia concentrations of 0-20 mol.% and methane concentrations of 2.5-10 mol.%. It is found that the calculation of the auto-ignition limit pressure at constant temperature leads to larger relative deviations between calculated and experimental results than the calculation of the auto-ignition temperature at constant pressure. In addition to the calculations, a reaction path analysis is performed to explain the observed lowering of the auto-ignition limit of methane/air mixtures by ammonia addition. It is found that this decrease is caused by the formation of NO and NO(2), which enhance the oxidation of methane at low temperatures. PMID:18926632
Temperature Fields in Soft Tissue during LPUS Treatment: Numerical Prediction and Experiment Results
Kujawska, Tamara; Wojcik, Janusz; Nowicki, Andrzej
2010-03-09
Recent research has shown that beneficial therapeutic effects in soft tissues can be induced by the low power ultrasound (LPUS). For example, increasing of cells immunity to stress (among others thermal stress) can be obtained through the enhanced heat shock proteins (Hsp) expression induced by the low intensity ultrasound. The possibility to control the Hsp expression enhancement in soft tissues in vivo stimulated by ultrasound can be the potential new therapeutic approach to the neurodegenerative diseases which utilizes the known feature of cells to increase their immunity to stresses through the Hsp expression enhancement. The controlling of the Hsp expression enhancement by adjusting of exposure level to ultrasound energy would allow to evaluate and optimize the ultrasound-mediated treatment efficiency. Ultrasonic regimes are controlled by adjusting the pulsed ultrasound waves intensity, frequency, duration, duty cycle and exposure time. Our objective was to develop the numerical model capable of predicting in space and time temperature fields induced by a circular focused transducer generating tone bursts in multilayer nonlinear attenuating media and to compare the numerically calculated results with the experimental data in vitro. The acoustic pressure field in multilayer biological media was calculated using our original numerical solver. For prediction of temperature fields the Pennes' bio-heat transfer equation was employed. Temperature field measurements in vitro were carried out in a fresh rat liver using the 15 mm diameter, 25 mm focal length and 2 MHz central frequency transducer generating tone bursts with the spatial peak temporal average acoustic intensity varied between 0.325 and 1.95 W/cm{sup 2}, duration varied from 20 to 500 cycles at the same 20% duty cycle and the exposure time varied up to 20 minutes. The measurement data were compared with numerical simulation results obtained under experimental boundary conditions. Good agreement between
NASA Astrophysics Data System (ADS)
Zueco, Joaquín; López-González, Luis María
2016-04-01
We have studied decompression processes when pressure changes that take place, in blood and tissues using a technical numerical based in electrical analogy of the parameters that involved in the problem. The particular problem analyzed is the behavior dynamics of the extravascular bubbles formed in the intercellular cavities of a hypothetical tissue undergoing decompression. Numerical solutions are given for a system of equations to simulate gas exchanges of bubbles after decompression, with particular attention paid to the effect of bubble size, nitrogen tension, nitrogen diffusivity in the intercellular fluid and in the tissue cell layer in a radial direction, nitrogen solubility, ambient pressure and specific blood flow through the tissue over the different molar diffusion fluxes of nitrogen per time unit (through the bubble surface, between the intercellular fluid layer and blood and between the intercellular fluid layer and the tissue cell layer). The system of nonlinear equations is solved using the Network Simulation Method, where the electric analogy is applied to convert these equations into a network-electrical model, and a computer code (electric circuit simulator, Pspice). In this paper, numerical results new (together to a network model improved with interdisciplinary electrical analogies) are provided.
Bearup, Daniel; Petrovskaya, Natalia; Petrovskii, Sergei
2015-05-01
Monitoring of pest insects is an important part of the integrated pest management. It aims to provide information about pest insect abundance at a given location. This includes data collection, usually using traps, and their subsequent analysis and/or interpretation. However, interpretation of trap count (number of insects caught over a fixed time) remains a challenging problem. First, an increase in either the population density or insects activity can result in a similar increase in the number of insects trapped (the so called "activity-density" problem). Second, a genuine increase of the local population density can be attributed to qualitatively different ecological mechanisms such as multiplication or immigration. Identification of the true factor causing an increase in trap count is important as different mechanisms require different control strategies. In this paper, we consider a mean-field mathematical model of insect trapping based on the diffusion equation. Although the diffusion equation is a well-studied model, its analytical solution in closed form is actually available only for a few special cases, whilst in a more general case the problem has to be solved numerically. We choose finite differences as the baseline numerical method and show that numerical solution of the problem, especially in the realistic 2D case, is not at all straightforward as it requires a sufficiently accurate approximation of the diffusion fluxes. Once the numerical method is justified and tested, we apply it to the corresponding boundary problem where different types of boundary forcing describe different scenarios of pest insect immigration and reveal the corresponding patterns in the trap count growth. PMID:25744607
2015-01-01
Background Due to the limited number of experimental studies that mechanically characterise human atherosclerotic plaque tissue from the femoral arteries, a recent trend has emerged in current literature whereby one set of material data based on aortic plaque tissue is employed to numerically represent diseased femoral artery tissue. This study aims to generate novel vessel-appropriate material models for femoral plaque tissue and assess the influence of using material models based on experimental data generated from aortic plaque testing to represent diseased femoral arterial tissue. Methods Novel material models based on experimental data generated from testing of atherosclerotic femoral artery tissue are developed and a computational analysis of the revascularisation of a quarter model idealised diseased femoral artery from a 90% diameter stenosis to a 10% diameter stenosis is performed using these novel material models. The simulation is also performed using material models based on experimental data obtained from aortic plaque testing in order to examine the effect of employing vessel appropriate material models versus those currently employed in literature to represent femoral plaque tissue. Results Simulations that employ material models based on atherosclerotic aortic tissue exhibit much higher maximum principal stresses within the plaque than simulations that employ material models based on atherosclerotic femoral tissue. Specifically, employing a material model based on calcified aortic tissue, instead of one based on heavily calcified femoral tissue, to represent diseased femoral arterial vessels results in a 487 fold increase in maximum principal stress within the plaque at a depth of 0.8 mm from the lumen. Conclusions Large differences are induced on numerical results as a consequence of employing material models based on aortic plaque, in place of material models based on femoral plaque, to represent a diseased femoral vessel. Due to these large
Equations of state of freely jointed hard-sphere chain fluids: Numerical results
Stell, G.; Lin, C.; Kalyuzhnyi, Y.V.
1999-03-01
We continue our series of studies in which the equations of state (EOS) are derived based on the product-reactant Ornstein{endash}Zernike approach (PROZA) and first-order thermodynamic perturbation theory (TPT1). These include two compressibility EOS, two virial EOS, and one TPT1 EOS (TPT1-D) that uses the structural information of the dimer fluid as input. In this study, we carry out the numerical implementation for these five EOS and compare their numerical results as well as those obtained from Attard{close_quote}s EOS and GF-D (generalized Flory-dimer) EOS with computer simulation results for the corresponding chain models over a wide range of densities and chain length. The comparison shows that our compressibility EOS, GF-D, and TPT1-D are in quantitative agreement with simulation results, and TPT1-D is the best among various EOS according to its average absolute deviation (AAD). On the basis of a comparison of limited data, our virial EOS appears to be superior to the predictions of Attard{close_quote}s approximate virial EOS and the approximate virial EOS derived by Schweizer and Curro in the context of the PRISM approach; all of them are only qualitatively accurate. The degree of accuracy predicted by our compressibility EOS is comparable to that of GF-D EOS, and both of them overestimate the compressibility factor at low densities and underestimate it at high densities. The compressibility factor of a polydisperse homonuclear chain system is also investigated in this work via our compressibility EOS; the numerical results are identical to those of a monodisperse system with the same chain length. {copyright} {ital 1999 American Institute of Physics.}
Numerical model of the lowermost Mississippi River as an alluvial-bedrock reach: preliminary results
NASA Astrophysics Data System (ADS)
Viparelli, E.; Nittrouer, J. A.; Mohrig, D. C.; Parker, G.
2012-12-01
level are accounted for in terms of a specified rate of sea level rise. In addition, the model allows a subsidence rate that varies in space and time. The time rate of change of channel bed elevation is computed solving the equation of mass conservation of the bed material. Validation of the model against field data is currently in progress in a relatively simplified setting, in which the bed material is characterized in terms of a single grain size. In addition, due to the lack of information on the geometry and the grain size characteristics of the floodplain, the modeling effort is restricted to the channel bed, and the procedure to route the washload through the system is not implemented. Having clearly in mind that the present Lowermost Mississippi River is not in equilibrium, validation runs are performed in two steps. The model is first run under pre-1930 conditions, under the assumption that the natural Mississippi River was not too far from long-term steady-state. The model is then run from the 1930s to the 2010s with the prevailing inputs of water and sediment and the model results are compared against field data. In the near future we plan to test the model with non-uniform bed material, and extend it to include inundation of the floodplain, and deposition of washload on it.
Numerical computation of the effective-one-body potential q using self-force results
NASA Astrophysics Data System (ADS)
Akcay, Sarp; van de Meent, Maarten
2016-03-01
The effective-one-body theory (EOB) describes the conservative dynamics of compact binary systems in terms of an effective Hamiltonian approach. The Hamiltonian for moderately eccentric motion of two nonspinning compact objects in the extreme mass-ratio limit is given in terms of three potentials: a (v ) , d ¯ (v ) , q (v ) . By generalizing the first law of mechanics for (nonspinning) black hole binaries to eccentric orbits, [A. Le Tiec, Phys. Rev. D 92, 084021 (2015).] recently obtained new expressions for d ¯(v ) and q (v ) in terms of quantities that can be readily computed using the gravitational self-force approach. Using these expressions we present a new computation of the EOB potential q (v ) by combining results from two independent numerical self-force codes. We determine q (v ) for inverse binary separations in the range 1 /1200 ≤v ≲1 /6 . Our computation thus provides the first-ever strong-field results for q (v ) . We also obtain d ¯ (v ) in our entire domain to a fractional accuracy of ≳10-8 . We find that our results are compatible with the known post-Newtonian expansions for d ¯(v ) and q (v ) in the weak field, and agree with previous (less accurate) numerical results for d ¯(v ) in the strong field.
Fluid Instabilities in the Crab Nebula Jet: Results from Numerical Simulations
NASA Astrophysics Data System (ADS)
Mignone, A.; Striani, E.; Bodo, G.; Anjiri, M.
2014-09-01
We present an overview of high-resolution relativistic MHD numerical simulations of the Crab Nebula South-East jet. The models are based on hot and relativistic hollow outflows initially carrying a purely toroidal magnetic field. Our results indicate that weakly relativistic (γ˜ 2) and strongly magnetized jets are prone to kink instabilities leading to a noticeable deflection of the jet. These conclusions are in good agreement with the recent X-ray (Chandra) data of Crab Nebula South-East jet indicating a change in the direction of propagation on a time scale of the order of few years.
Oki, Delwyn S.
1998-01-01
-calculated freshwater-saltwater interface location for the future recharge and pumping conditions. Model results indicate that an additional 10 million gallons per day (beyond the 1995-allocated rates) of freshwater can potentially be developed from northern Oahu. Various distributions of pumping can be used to obtain the additional 10 million gallons per day of water. The quality of the water pumped will be dependent on site-specific factors and cannot be predicted on the basis of model results. If the additional 10 million gallons per day pumpage is restricted to the Kawailoa and Waialua areas, model results indicate that a regional drawdown (relative to the water-level distribution associated with the 1995-allocated pumping rates) of less than 0.6 foot can be maintained in these two areas. The additional pumping, however, would cause salinity increases in water pumped by existing deep wells. In addition, increases in salinity may occur at other wells in areas where the model indicates no significant problem with upconing.
Noninvasive assessment of mitral inertness: clinical results with numerical model validation
NASA Technical Reports Server (NTRS)
Firstenberg, M. S.; Greenberg, N. L.; Smedira, N. G.; McCarthy, P. M.; Garcia, M. J.; Thomas, J. D.
2001-01-01
Inertial forces (Mdv/dt) are a significant component of transmitral flow, but cannot be measured with Doppler echo. We validated a method of estimating Mdv/dt. Ten patients had a dual sensor transmitral (TM) catheter placed during cardiac surgery. Doppler and 2D echo was performed while acquiring LA and LV pressures. Mdv/dt was determined from the Bernoulli equation using Doppler velocities and TM gradients. Results were compared with numerical modeling. TM gradients (range: 1.04-14.24 mmHg) consisted of 74.0 +/- 11.0% inertial forcers (range: 0.6-12.9 mmHg). Multivariate analysis predicted Mdv/dt = -4.171(S/D (RATIO)) + 0.063(LAvolume-max) + 5. Using this equation, a strong relationship was obtained for the clinical dataset (y=0.98x - 0.045, r=0.90) and the results of numerical modeling (y=0.96x - 0.16, r=0.84). TM gradients are mainly inertial and, as validated by modeling, can be estimated with echocardiography.
NASA Astrophysics Data System (ADS)
Lahaye, Noé; Paci, Alexandre; Smith, Stefan Llewellyn
2016-04-01
We examine the instability of lenticular vortices -- or lenses -- in a stratified rotating fluid. The simplest configuration is one in which the lenses overlay a deep layer and have a free surface, and this can be studied using a two-layer rotating shallow water model. We report results from laboratory experiments and high-resolution direct numerical simulations of the destabilization of vortices with constant potential vorticity, and compare these to a linear stability analysis. The stability properties of the system are governed by two parameters: the typical upper-layer potential vorticity and the size (depth) of the vortex. Good agreement is found between analytical, numerical and experimental results for the growth rate and wavenumber of the instability. The nonlinear saturation of the instability is associated with conversion from potential to kinetic energy and weak emission of gravity waves, giving rise to the formation of coherent vortex multipoles with trapped waves. The impact of flow in the lower layer is examined. In particular, it is shown that the growth rate can be strongly affected and the instability can be suppressed for certain types of weak co-rotating flow.
Re-Computation of Numerical Results Contained in NACA Report No. 496
NASA Technical Reports Server (NTRS)
Perry, Boyd, III
2015-01-01
An extensive examination of NACA Report No. 496 (NACA 496), "General Theory of Aerodynamic Instability and the Mechanism of Flutter," by Theodore Theodorsen, is described. The examination included checking equations and solution methods and re-computing interim quantities and all numerical examples in NACA 496. The checks revealed that NACA 496 contains computational shortcuts (time- and effort-saving devices for engineers of the time) and clever artifices (employed in its solution methods), but, unfortunately, also contains numerous tripping points (aspects of NACA 496 that have the potential to cause confusion) and some errors. The re-computations were performed employing the methods and procedures described in NACA 496, but using modern computational tools. With some exceptions, the magnitudes and trends of the original results were in fair-to-very-good agreement with the re-computed results. The exceptions included what are speculated to be computational errors in the original in some instances and transcription errors in the original in others. Independent flutter calculations were performed and, in all cases, including those where the original and re-computed results differed significantly, were in excellent agreement with the re-computed results. Appendix A contains NACA 496; Appendix B contains a Matlab(Reistered) program that performs the re-computation of results; Appendix C presents three alternate solution methods, with examples, for the two-degree-of-freedom solution method of NACA 496; Appendix D contains the three-degree-of-freedom solution method (outlined in NACA 496 but never implemented), with examples.
Castro, A. P. G.; Paul, C. P. L.; Detiger, S. E. L.; Smit, T. H.; van Royen, B. J.; Pimenta Claro, J. C.; Mullender, M. G.; Alves, J. L.
2014-01-01
The loaded disk culture system is an intervertebral disk (IVD)-oriented bioreactor developed by the VU Medical Center (VUmc, Amsterdam, The Netherlands), which has the capacity of maintaining up to 12 IVDs in culture, for approximately 3 weeks after extraction. Using this system, eight goat IVDs were provided with the essential nutrients and submitted to compression tests without losing their biomechanical and physiological properties, for 22 days. Based on previous reports (Paul et al., 2012, 2013; Detiger et al., 2013), four of these IVDs were kept in physiological condition (control) and the other four were previously injected with chondroitinase ABC (CABC), in order to promote degenerative disk disease (DDD). The loading profile intercalated 16 h of activity loading with 8 h of loading recovery to express the standard circadian variations. The displacement behavior of these eight IVDs along the first 2 days of the experiment was numerically reproduced, using an IVD osmo-poro-hyper-viscoelastic and fiber-reinforced finite element (FE) model. The simulations were run on a custom FE solver (Castro et al., 2014). The analysis of the experimental results allowed concluding that the effect of the CABC injection was only significant in two of the four IVDs. The four control IVDs showed no signs of degeneration, as expected. In what concerns to the numerical simulations, the IVD FE model was able to reproduce the generic behavior of the two groups of goat IVDs (control and injected). However, some discrepancies were still noticed on the comparison between the injected IVDs and the numerical simulations, namely on the recovery periods. This may be justified by the complexity of the pathways for DDD, associated with the multiplicity of physiological responses to each direct or indirect stimulus. Nevertheless, one could conclude that ligaments, muscles, and IVD covering membranes could be added to the FE model, in order to improve its accuracy and properly
Castro, A P G; Paul, C P L; Detiger, S E L; Smit, T H; van Royen, B J; Pimenta Claro, J C; Mullender, M G; Alves, J L
2014-01-01
The loaded disk culture system is an intervertebral disk (IVD)-oriented bioreactor developed by the VU Medical Center (VUmc, Amsterdam, The Netherlands), which has the capacity of maintaining up to 12 IVDs in culture, for approximately 3 weeks after extraction. Using this system, eight goat IVDs were provided with the essential nutrients and submitted to compression tests without losing their biomechanical and physiological properties, for 22 days. Based on previous reports (Paul et al., 2012, 2013; Detiger et al., 2013), four of these IVDs were kept in physiological condition (control) and the other four were previously injected with chondroitinase ABC (CABC), in order to promote degenerative disk disease (DDD). The loading profile intercalated 16 h of activity loading with 8 h of loading recovery to express the standard circadian variations. The displacement behavior of these eight IVDs along the first 2 days of the experiment was numerically reproduced, using an IVD osmo-poro-hyper-viscoelastic and fiber-reinforced finite element (FE) model. The simulations were run on a custom FE solver (Castro et al., 2014). The analysis of the experimental results allowed concluding that the effect of the CABC injection was only significant in two of the four IVDs. The four control IVDs showed no signs of degeneration, as expected. In what concerns to the numerical simulations, the IVD FE model was able to reproduce the generic behavior of the two groups of goat IVDs (control and injected). However, some discrepancies were still noticed on the comparison between the injected IVDs and the numerical simulations, namely on the recovery periods. This may be justified by the complexity of the pathways for DDD, associated with the multiplicity of physiological responses to each direct or indirect stimulus. Nevertheless, one could conclude that ligaments, muscles, and IVD covering membranes could be added to the FE model, in order to improve its accuracy and properly
Interpretation of high-dimensional numerical results for the Anderson transition
Suslov, I. M.
2014-12-15
The existence of the upper critical dimension d{sub c2} = 4 for the Anderson transition is a rigorous consequence of the Bogoliubov theorem on renormalizability of φ{sup 4} theory. For d ≥ 4 dimensions, one-parameter scaling does not hold and all existent numerical data should be reinterpreted. These data are exhausted by the results for d = 4, 5 from scaling in quasi-one-dimensional systems and the results for d = 4, 5, 6 from level statistics. All these data are compatible with the theoretical scaling dependences obtained from Vollhardt and Wolfle’s self-consistent theory of localization. The widespread viewpoint that d{sub c2} = ∞ is critically discussed.
Asymptotic expansion for stellarator equilibria with a non-planar magnetic axis: Numerical results
NASA Astrophysics Data System (ADS)
Freidberg, Jeffrey; Cerfon, Antoine; Parra, Felix
2012-10-01
We have recently presented a new asymptotic expansion for stellarator equilibria that generalizes the classic Greene-Johnson expansion [1] to allow for 3D equilibria with a non-planar magnetic axis [2]. Our expansion achieves the two goals of reducing the complexity of the three-dimensional MHD equilibrium equations and of describing equilibria in modern stellarator experiments. The end result of our analysis is a set of two coupled partial differential equations for the plasma pressure and the toroidal vector potential which fully determine the stellarator equilibrium. Both equations are advection equations in which the toroidal angle plays the role of time. We show that the method of characteristics, following magnetic field lines, is a convenient way of solving these equations, avoiding the difficulties associated with the periodicity of the solution in the toroidal angle. By combining the method of characteristics with Green's function integrals for the evaluation of the magnetic field due to the plasma current, we obtain an efficient numerical solver for our expansion. Numerical equilibria thus calculated will be given.[4pt] [1] J.M. Greene and J.L. Johnson, Phys. Fluids 4, 875 (1961)[0pt] [2] A.J. Cerfon, J.P. Freidberg, and F.I. Parra, Bull. Am. Phys. Soc. 56, 16 GP9.00081 (2011)
Verification of Numerical Weather Prediction Model Results for Energy Applications in Latvia
NASA Astrophysics Data System (ADS)
Sīle, Tija; Cepite-Frisfelde, Daiga; Sennikovs, Juris; Bethers, Uldis
2014-05-01
A resolution to increase the production and consumption of renewable energy has been made by EU governments. Most of the renewable energy in Latvia is produced by Hydroelectric Power Plants (HPP), followed by bio-gas, wind power and bio-mass energy production. Wind and HPP power production is sensitive to meteorological conditions. Currently the basis of weather forecasting is Numerical Weather Prediction (NWP) models. There are numerous methodologies concerning the evaluation of quality of NWP results (Wilks 2011) and their application can be conditional on the forecast end user. The goal of this study is to evaluate the performance of Weather Research and Forecast model (Skamarock 2008) implementation over the territory of Latvia, focusing on forecasting of wind speed and quantitative precipitation forecasts. The target spatial resolution is 3 km. Observational data from Latvian Environment, Geology and Meteorology Centre are used. A number of standard verification metrics are calculated. The sensitivity to the model output interpretation (output spatial interpolation versus nearest gridpoint) is investigated. For the precipitation verification the dichotomous verification metrics are used. Sensitivity to different precipitation accumulation intervals is examined. Skamarock, William C. and Klemp, Joseph B. A time-split nonhydrostatic atmospheric model for weather research and forecasting applications. Journal of Computational Physics. 227, 2008, pp. 3465-3485. Wilks, Daniel S. Statistical Methods in the Atmospheric Sciences. Third Edition. Academic Press, 2011.
NASA Astrophysics Data System (ADS)
Carrano, Charles S.; Rino, Charles L.
2016-06-01
We extend the power law phase screen theory for ionospheric scintillation to account for the case where the refractive index irregularities follow a two-component inverse power law spectrum. The two-component model includes, as special cases, an unmodified power law and a modified power law with spectral break that may assume the role of an outer scale, intermediate break scale, or inner scale. As such, it provides a framework for investigating the effects of a spectral break on the scintillation statistics. Using this spectral model, we solve the fourth moment equation governing intensity variations following propagation through two-dimensional field-aligned irregularities in the ionosphere. A specific normalization is invoked that exploits self-similar properties of the structure to achieve a universal scaling, such that different combinations of perturbation strength, propagation distance, and frequency produce the same results. The numerical algorithm is validated using new theoretical predictions for the behavior of the scintillation index and intensity correlation length under strong scatter conditions. A series of numerical experiments are conducted to investigate the morphologies of the intensity spectrum, scintillation index, and intensity correlation length as functions of the spectral indices and strength of scatter; retrieve phase screen parameters from intensity scintillation observations; explore the relative contributions to the scintillation due to large- and small-scale ionospheric structures; and quantify the conditions under which a general spectral break will influence the scintillation statistics.
Chaoticity threshold in magnetized plasmas: Numerical results in the weak coupling regime
Carati, A. Benfenati, F.; Maiocchi, A.; Galgani, L.; Zuin, M.
2014-03-15
The present paper is a numerical counterpart to the theoretical work [Carati et al., Chaos 22, 033124 (2012)]. We are concerned with the transition from order to chaos in a one-component plasma (a system of point electrons with mutual Coulomb interactions, in a uniform neutralizing background), the plasma being immersed in a uniform stationary magnetic field. In the paper [Carati et al., Chaos 22, 033124 (2012)], it was predicted that a transition should take place when the electron density is increased or the field decreased in such a way that the ratio ω{sub p}/ω{sub c} between plasma and cyclotron frequencies becomes of order 1, irrespective of the value of the so-called Coulomb coupling parameter Γ. Here, we perform numerical computations for a first principles model of N point electrons in a periodic box, with mutual Coulomb interactions, using as a probe for chaoticity the time-autocorrelation function of magnetization. We consider two values of Γ (0.04 and 0.016) in the weak coupling regime Γ ≪ 1, with N up to 512. A transition is found to occur for ω{sub p}/ω{sub c} in the range between 0.25 and 2, in fairly good agreement with the theoretical prediction. These results might be of interest for the problem of the breakdown of plasma confinement in fusion machines.
NASA Astrophysics Data System (ADS)
Soares, Edson J.; Thompson, Roney L.; Niero, Debora C.
2015-08-01
The immiscible displacement of one viscous liquid by another in a capillary tube is experimentally and numerically analyzed in the low inertia regime with negligible buoyancy effects. The dimensionless numbers that govern the problem are the capillary number Ca and the viscosity ratio of the displaced to the displacing fluids Nμ. In general, there are two output quantities of interest. One is associated to the relation between the front velocity, Ub, and the mean velocity of the displaced fluid, U ¯ 2 . The other is the layer thickness of the displaced fluid that remains attached to the wall. We compute these quantities as mass fractions in order to make them able to be compared. In this connection, the efficiency mass fraction, me, is defined as the complement of the mass fraction of the displaced fluid that leaves the tube while the displacing fluid crosses its length. The geometric mass fraction, mg, is defined as the fraction of the volume of the layer that remains attached to the wall. Because in gas-liquid displacement, these two quantities coincide, it is not uncommon in the literature to use mg as a measure of the displacement efficiency for liquid-liquid displacements. However, as is shown in the present paper, these two quantities have opposite tendencies when we increase the viscosity of the displacing fluid, making this distinction a crucial aspect of the problem. Results from a Galerkin finite element approach are also presented in order to make a comparison. Experimental and numerical results show that while the displacement efficiency decreases, the geometrical fraction increases when the viscosity ratio decreases. This fact leads to different decisions depending on the quantity to be optimized. The quantitative agreement between the numerical and experimental results was not completely achieved, especially for intermediate values of Ca. The reasons for that are still under investigation. The experiments conducted were able to achieve a wide range
Sletvold, Nina; Moritz, Kim K; Agren, Jon
2015-01-01
Mutualists and antagonists are known to respond to similar floral cues, and may thus cause opposing selection on floral traits. However, we lack a quantitative understanding of their independent and interactive effects. In a population of the orchid Gymnadenia conopsea, we manipulated the intensity of pollination and herbivory in a factorial design to examine whether both interactions influence selection on flowering phenology, floral display, and morphology. Supplemental hand-pollination increased female fitness by 31% and one-quarter of all plants were damaged by herbivores. Both interactions contributed to selection. Pollinators mediated selection for later flowering and herbivores for earlier flowering, while both selected for longer spurs. The strength of selection was similar for both agents, and their effects were additive. As a consequence, there was no. net selection on phenology, whereas selection on spur length was strong. The experimental results demonstrate that both pollinators and herbivores can markedly influence the strength of selection on flowering phenology and floral morphology, and cause both conflicting and reinforcing selection. They also indicate that the direction of selection on phenology will vary with the relative intensity of the mutualistic and antagonistic interaction, potentially resulting in both temporal and among-population variation in optimal flowering time. PMID:26236906
Preliminary Results from Numerical Experiments on the Summer 1980 Heat Wave and Drought
NASA Technical Reports Server (NTRS)
Wolfson, N.; Atlas, R.; Sud, Y. C.
1985-01-01
During the summer of 1980, a prolonged heat wave and drought affected the United States. A preliminary set of experiments has been conducted to study the effect of varying boundary conditions on the GLA model simulation of the heat wave. Five 10-day numerical integrations with three different specifications of boundary conditions were carried out: a control experiment which utilized climatological boundary conditions, an SST experiment which utilized summer 1980 sea-surface temperatures in the North Pacific, but climatological values elsewhere, and a Soil Moisture experiment which utilized the values of Mintz-Serafini for the summer, 1980. The starting dates for the five forecasts were 11 June, 7 July, 21 July, 22 August, and 6 September of 1980. These dates were specifically chosen as days when a heat wave was already established in order to investigate the effect of soil moistures or North Pacific sea-surface temperatures on the model's ability to maintain the heat wave pattern. The experiments were evaluated in terms of the heat wave index for the South Plains, North Plains, Great Plains and the entire U.S. In addition a subjective comparison of map patterns has been performed.
NASA Astrophysics Data System (ADS)
Chiu, Ming-Hung; Lai, Chin-Fa; Tan, Chen-Tai; Lin, Yi-Zhi
2011-03-01
This paper presents a study of the lateral and axial resolutions of a transmission laser-scanning angle-deviation microscope (TADM) with different numerical aperture (NA) values. The TADM is based on geometric optics and surface plasmon resonance principles. The surface height is proportional to the phase difference between two marginal rays of the test beam, which is passed through the test medium. We used common-path heterodyne interferometry to measure the phase difference in real time, and used a personal computer to calculate and plot the surface profile. The experimental results showed that the best lateral and axial resolutions for NA = 0.41 were 0.5 μm and 3 nm, respectively, and the lateral resolution breaks through the diffraction limits.
NASA Astrophysics Data System (ADS)
Milošević, M.; Dimitrijević, D. D.; Djordjević, G. S.; Stojanović, M. D.
2016-06-01
The role tachyon fields may play in evolution of early universe is discussed in this paper. We consider the evolution of a flat and homogeneous universe governed by a tachyon scalar field with the DBI-type action and calculate the slow-roll parameters of inflation, scalar spectral index (n), and tensor-scalar ratio (r) for the given potentials. We pay special attention to the inverse power potential, first of all to V(x)˜ x^{-4}, and compare the available results obtained by analytical and numerical methods with those obtained by observation. It is shown that the computed values of the observational parameters and the observed ones are in a good agreement for the high values of the constant X_0. The possibility that influence of the radion field can extend a range of the acceptable values of the constant X_0 to the string theory motivated sector of its values is briefly considered.
Solar flare model: Comparison of the results of numerical simulations and observations
NASA Astrophysics Data System (ADS)
Podgorny, I. M.; Vashenyuk, E. V.; Podgorny, A. I.
2009-12-01
The electrodynamic flare model is based on numerical 3D simulations with the real magnetic field of an active region. An energy of ˜1032 erg necessary for a solar flare is shown to accumulate in the magnetic field of a coronal current sheet. The thermal X-ray source in the corona results from plasma heating in the current sheet upon reconnection. The hard X-ray sources are located on the solar surface at the loop foot-points. They are produced by the precipitation of electron beams accelerated in field-aligned currents. Solar cosmic rays appear upon acceleration in the electric field along a singular magnetic X-type line. The generation mechanism of the delayed cosmic-ray component is also discussed.
NASA Astrophysics Data System (ADS)
Xu, Hengyi; Heinzel, T.; Zozoulenko, I. V.
2011-09-01
We derive analytical expressions for the conductivity of bilayer graphene (BLG) using the Boltzmann approach within the the Born approximation for a model of Gaussian disorders describing both short- and long-range impurity scattering. The range of validity of the Born approximation is established by comparing the analytical results to exact tight-binding numerical calculations. A comparison of the obtained density dependencies of the conductivity with experimental data shows that the BLG samples investigated experimentally so far are in the quantum scattering regime where the Fermi wavelength exceeds the effective impurity range. In this regime both short- and long-range scattering lead to the same linear density dependence of the conductivity. Our calculations imply that bilayer and single-layer graphene have the same scattering mechanisms. We also provide an upper limit for the effective, density-dependent spatial extension of the scatterers present in the experiments.
Marom, Gil; Bluestein, Danny
2016-02-01
This paper evaluated the influence of various numerical implementation assumptions on predicting blood damage in cardiovascular devices using Lagrangian methods with Eulerian computational fluid dynamics. The implementation assumptions that were tested included various seeding patterns, stochastic walk model, and simplified trajectory calculations with pathlines. Post processing implementation options that were evaluated included single passage and repeated passages stress accumulation and time averaging. This study demonstrated that the implementation assumptions can significantly affect the resulting stress accumulation, i.e., the blood damage model predictions. Careful considerations should be taken in the use of Lagrangian models. Ultimately, the appropriate assumptions should be considered based the physics of the specific case and sensitivity analysis, similar to the ones presented here, should be employed. PMID:26679833
NASA Astrophysics Data System (ADS)
Cotel, Aline; Junghans, Lars; Wang, Xiaoxiang
2014-11-01
In recent years, a recognition of the scope of the negative environmental impact of existing buildings has spurred academic and industrial interest in transforming existing building design practices and disciplinary knowledge. For example, buildings alone consume 72% of the electricity produced annually in the United States; this share is expected to rise to 75% by 2025 (EPA, 2009). Significant reductions in overall building energy consumption can be achieved using green building methods such as natural ventilation. An office was instrumented on campus to acquire CO2 concentrations and temperature profiles at multiple locations while a single occupant was present. Using openFOAM, numerical calculations were performed to allow for comparisons of the CO2 concentration and temperature profiles for different ventilation strategies. Ultimately, these results will be the inputs into a real time feedback control system that can adjust actuators for indoor ventilation and utilize green design strategies. Funded by UM Office of Vice President for Research.
NASA Technical Reports Server (NTRS)
Holman, Gordon
2010-01-01
Accelerated electrons play an important role in the energetics of solar flares. Understanding the process or processes that accelerate these electrons to high, nonthermal energies also depends on understanding the evolution of these electrons between the acceleration region and the region where they are observed through their hard X-ray or radio emission. Energy losses in the co-spatial electric field that drives the current-neutralizing return current can flatten the electron distribution toward low energies. This in turn flattens the corresponding bremsstrahlung hard X-ray spectrum toward low energies. The lost electron beam energy also enhances heating in the coronal part of the flare loop. Extending earlier work by Knight & Sturrock (1977), Emslie (1980), Diakonov & Somov (1988), and Litvinenko & Somov (1991), I have derived analytical and semi-analytical results for the nonthermal electron distribution function and the self-consistent electric field strength in the presence of a steady-state return-current. I review these results, presented previously at the 2009 SPD Meeting in Boulder, CO, and compare them and computed X-ray spectra with numerical results obtained by Zharkova & Gordovskii (2005, 2006). The phYSical significance of similarities and differences in the results will be emphasized. This work is supported by NASA's Heliophysics Guest Investigator Program and the RHESSI Project.
Lima da Silva, M.; Sauvage, E.; Brun, P.; Gagnoud, A.; Fautrelle, Y.; Riva, R.
2013-07-01
The process of vitrification in a cold crucible heated by direct induction is used in the fusion of oxides. Its feature is the production of high-purity materials. The high-level of purity of the molten is achieved because this melting technique excludes the contamination of the charge by the crucible. The aim of the present paper is to analyze the hydrodynamic of the vitrification process by direct induction, with the focus in the effects associated with the interaction between the mechanical stirrer and bubbling. Considering the complexity of the analyzed system and the goal of the present work, we simplified the system by not taking into account the thermal and electromagnetic phenomena. Based in the concept of hydraulic similitude, we performed an experimental study and a numerical modeling of the simplified model. The results of these two studies were compared and showed a good agreement. The results presented in this paper in conjunction with the previous work contribute to a better understanding of the hydrodynamics effects resulting from the interaction between the mechanical stirrer and air bubbling in the cold crucible heated by direct induction. Further works will take into account thermal and electromagnetic phenomena in the presence of mechanical stirrer and air bubbling. (authors)
NASA Astrophysics Data System (ADS)
Peukert, P.; Hrubý, J.
2013-04-01
The paper describes new results for an experimental heat exchanger equipped with a single corrugated capillary tube, basic information about the measurements and the experimental setup. Some of the results were compared with numerical simulations.
Pathmanathan, P; Bernabeu, M O; Niederer, S A; Gavaghan, D J; Kay, D
2012-08-01
A recent verification study compared 11 large-scale cardiac electrophysiology solvers on an unambiguously defined common problem. An unexpected amount of variation was observed between the codes, including significant error in conduction velocity in the majority of the codes at certain spatial resolutions. In particular, the results of the six finite element codes varied considerably despite each using the same order of interpolation. In this present study, we compare various algorithms for cardiac electrophysiological simulation, which allows us to fully explain the differences between the solvers. We identify the use of mass lumping as the fundamental cause of the largest variations, specifically the combination of the commonly used techniques of mass lumping and operator splitting, which results in a slightly different form of mass lumping to that supported by theory and leads to increased numerical error. Other variations are explained through the manner in which the ionic current is interpolated. We also investigate the effect of different forms of mass lumping in various types of simulation. PMID:25099569
TANK 40 FINAL SB5 CHEMICAL CHARACTERIZATION RESULTS PRIOR TO NP ADDITION
Bannochie, C.; Click, D.
2010-01-06
A sample of Sludge Batch 5 (SB5) was pulled from Tank 40 in order to obtain radionuclide inventory analyses necessary for compliance with the Waste Acceptance Product Specifications (WAPS). This sample was also analyzed for chemical composition including noble metals. Prior to radionuclide inventory analyses, a final sample of the H-canyon Np stream will be added to bound the Np addition anticipated for Tank 40. These analyses along with the WAPS radionuclide analyses will help define the composition of the sludge in Tank 40 that is currently being fed to DWPF as SB5. At the Savannah River National Laboratory (SRNL) the 3-L Tank 40 SB5 sample was transferred from the shipping container into a 4-L high density polyethylene vessel and solids allowed to settle overnight. Supernate was then siphoned off and circulated through the shipping container to complete the transfer of the sample. Following thorough mixing of the 3-L sample, a 239 g sub-sample was removed. This sub-sample was then utilized for all subsequent analytical samples. Eight separate aliquots of the slurry were digested, four with HNO{sub 3}/HCl (aqua regia) in sealed Teflon{reg_sign} vessels and four in Na{sub 2}O{sub 2} (alkali or peroxide fusion) using Zr crucibles. Due to the use of Zr crucibles and Na in the peroxide fusions, Na and Zr cannot be determined from this preparation. Additionally, other alkali metals, such as Li and K that may be contaminants in the Na{sub 2}O{sub 2} are not determined from this preparation. Three Analytical Reference Glass - 14 (ARG-1) standards were digested along with a blank for each preparation. The ARG-1 glass allows for an assessment of the completeness of each digestion. Each aqua regia digestion and blank was diluted to 1:100 mL with deionized water and submitted to Analytical Development (AD) for inductively coupled plasma - atomic emission spectroscopy (ICPAES) analysis, inductively coupled plasma - mass spectrometry (ICP-MS) analysis of masses 81-209 and 230
TANK 40 FINAL SB5 CHEMICAL CHARACTERIZATION RESULTS PRIOR TO NP ADDITION
Bannochie, C; Damon Click, D
2009-02-26
A sample of Sludge Batch 5 (SB5) was pulled from Tank 40 in order to obtain radionuclide inventory analyses necessary for compliance with the Waste Acceptance Product Specifications (WAPS). This sample was also analyzed for chemical composition including noble metals. Prior to radionuclide inventory analyses, a final sample of the H-canyon Np stream will be added to bound the Np addition anticipated for Tank 40. These analyses along with the WAPS radionuclide analyses will help define the composition of the sludge in Tank 40 that is currently being fed to DWPF as SB5. At the Savannah River National Laboratory (SRNL) the 3-L Tank 40 SB5 sample was transferred from the shipping container into a 4-L high density polyethylene vessel and solids allowed to settle overnight. Supernate was then siphoned off and circulated through the shipping container to complete the transfer of the sample. Following thorough mixing of the 3-L sample, a 239 g sub-sample was removed. This sub-sample was then utilized for all subsequent analytical samples. Eight separate aliquots of the slurry were digested, four with HNO{sub 3}/HCl (aqua regia) in sealed Teflon{reg_sign} vessels and four in Na{sub 2}O{sub 2} (alkali or peroxide fusion) using Zr crucibles. Due to the use of Zr crucibles and Na in the peroxide fusions, Na and Zr cannot be determined from this preparation. Additionally, other alkali metals, such as Li and K that may be contaminants in the Na{sub 2}O{sub 2} are not determined from this preparation. Three Analytical Reference Glass-1 (ARG-1) standards were digested along with a blank for each preparation. The ARG-1 glass allows for an assessment of the completeness of each digestion. Each aqua regia digestion and blank was diluted to 1:100 mL with deionized water and submitted to Analytical Development (AD) for inductively coupled plasma--atomic emission spectroscopy (ICPAES) analysis, inductively coupled plasma--mass spectrometry (ICP-MS) analysis of masses 81-209 and 230
NASA Astrophysics Data System (ADS)
Beniaiche, Ahmed; Ghenaiet, Adel; Carcasci, Carlo; Facchini, Bruno
2016-05-01
This paper presents a numerical validation of the aero-thermal study of a 30:1 scaled model reproducing an innovative trailing edge with one row of enlarged pedestals under stationary and rotating conditions. A CFD analysis was performed by means of commercial ANSYS-Fluent modeling the isothermal air flow and using k-ω SST turbulence model and an isothermal air flow for both static and rotating conditions (Ro up to 0.23). The used numerical model is validated first by comparing the numerical velocity profiles distribution results to those obtained experimentally by means of PIV technique for Re = 20,000 and Ro = 0-0.23. The second validation is based on the comparison of the numerical results of the 2D HTC maps over the heated plate to those of TLC experimental data, for a smooth surface for a Reynolds number = 20,000 and 40,000 and Ro = 0-0.23. Two-tip conditions were considered: open tip and closed tip conditions. Results of the average Nusselt number inside the pedestal ducts region are presented too. The obtained results help to predict the flow field visualization and the evaluation of the aero-thermal performance of the studied blade cooling system during the design step.
Liberatore, S.; Jaouen, S.; Tabakhoff, E.; Canaud, B.
2009-04-15
Magnetic Rayleigh-Taylor instability is addressed in compressible hydrostatic media. A full model is presented and compared to numerical results from a linear perturbation code. A perfect agreement between both approaches is obtained in a wide range of parameters. Compressibility effects are examined and substantial deviations from classical Chandrasekhar growth rates are obtained and confirmed by the model and the numerical calculations.
Numerical modeling of protocore destabilization during planetary accretion: Methodology and results
NASA Astrophysics Data System (ADS)
Lin, Ja-Ren; Gerya, Taras V.; Tackley, Paul J.; Yuen, David A.; Golabek, Gregor J.
2009-12-01
We developed and tested an efficient 2D numerical methodology for modeling gravitational redistribution processes in a quasi spherical planetary body based on a simple Cartesian grid. This methodology allows one to implement large viscosity contrasts and to handle properly a free surface and self-gravitation. With this novel method we investigated in a simplified way the evolution of gravitationally unstable global three-layer structures in the interiors of large metal-silicate planetary bodies like those suggested by previous models of cold accretion [Sasaki, S., Nakazawa, K., 1986. J. Geophys. Res. 91, 9231-9238; Karato, S., Murthy, V.R., 1997. Phys. Earth Planet Interios 100, 61-79; Senshu, H., Kuramoto, K., Matsui, T., 2002. J. Geophys. Res. 107 (E12), 5118. 10.1029/2001JE001819]: an innermost solid protocore (either undifferentiated or partly differentiated), an intermediate metal-rich layer (either continuous or disrupted), and an outermost silicate-rich layer. Long-wavelength (degree-one) instability of this three-layer structure may strongly contribute to core formation dynamics by triggering planetary-scale gravitational redistribution processes. We studied possible geometrical modes of the resulting planetary reshaping using scaled 2D numerical experiments for self-gravitating planetary bodies with Mercury-, Mars- and Earth-size. In our simplified model the viscosity of each material remains constant during the experiment and rheological effects of gravitational energy dissipation are not taken into account. However, in contrast to a previously conducted numerical study [Honda, R., Mizutani, H., Yamamoto, T., 1993. J. Geophys. Res. 98, 2075-2089] we explored a freely deformable planetary surface and a broad range of viscosity ratios between the metallic layer and the protocore (0.001-1000) as well as between the silicate layer and the protocore (0.001-1000). An important new prediction from our study is that realistic modes of planetary reshaping
Speech Perception Results for Children Using Cochlear Implants Who Have Additional Special Needs
ERIC Educational Resources Information Center
Dettman, Shani J.; Fiket, Hayley; Dowell, Richard C.; Charlton, Margaret; Williams, Sarah S.; Tomov, Alexandra M.; Barker, Elizabeth J.
2004-01-01
Speech perception outcomes in young children with cochlear implants are affected by a number of variables including the age of implantation, duration of implantation, mode of communication, and the presence of a developmental delay or additional disability. The aim of this study is to examine the association between degree of developmental delay…
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.
NASA Astrophysics Data System (ADS)
Xing, H. L.; Ding, R. W.; Yuen, D. A.
2015-08-01
Australia is surrounded by the Pacific Ocean and the Indian Ocean and, thus, may suffer from tsunamis due to its proximity to the subduction earthquakes around the boundary of Australian Plate. Potential tsunami risks along the eastern coast, where more and more people currently live, are numerically investigated through a scenario-based method to provide an estimation of the tsunami hazard in this region. We have chosen and calculated the tsunami waves generated at the New Hebrides Trench and the Puysegur Trench, and we further investigated the relevant tsunami hazards along the eastern coast and their sensitivities to various sea floor frictions and earthquake parameters (i.e. the strike, the dip and the slip angles and the earthquake magnitude/rupture length). The results indicate that the Puysegur trench possesses a seismic threat causing wave amplitudes over 1.5 m along the coast of Tasmania, Victoria, and New South Wales, and even reaching over 2.6 m at the regions close to Sydney, Maria Island, and Gabo Island for a certain worse case, while the cities along the coast of Queensland are potentially less vulnerable than those on the southeastern Australian coast.
Sprenger, Lisa Lange, Adrian; Odenbach, Stefan
2014-02-15
Ferrofluids consist of magnetic nanoparticles dispersed in a carrier liquid. Their strong thermodiffusive behaviour, characterised by the Soret coefficient, coupled with the dependency of the fluid's parameters on magnetic fields is dealt with in this work. It is known from former experimental investigations on the one hand that the Soret coefficient itself is magnetic field dependent and on the other hand that the accuracy of the coefficient's experimental determination highly depends on the volume concentration of the fluid. The thermally driven separation of particles and carrier liquid is carried out with a concentrated ferrofluid (φ = 0.087) in a horizontal thermodiffusion cell and is compared to equally detected former measurement data. The temperature gradient (1 K/mm) is applied perpendicular to the separation layer. The magnetic field is either applied parallel or perpendicular to the temperature difference. For three different magnetic field strengths (40 kA/m, 100 kA/m, 320 kA/m) the diffusive separation is detected. It reveals a sign change of the Soret coefficient with rising field strength for both field directions which stands for a change in the direction of motion of the particles. This behaviour contradicts former experimental results with a dilute magnetic fluid, in which a change in the coefficient's sign could only be detected for the parallel setup. An anisotropic behaviour in the current data is measured referring to the intensity of the separation being more intense in the perpendicular position of the magnetic field: S{sub T‖} = −0.152 K{sup −1} and S{sub T⊥} = −0.257 K{sup −1} at H = 320 kA/m. The ferrofluiddynamics-theory (FFD-theory) describes the thermodiffusive processes thermodynamically and a numerical simulation of the fluid's separation depending on the two transport parameters ξ{sub ‖} and ξ{sub ⊥} used within the FFD-theory can be implemented. In the case of a parallel aligned magnetic field, the parameter can
NASA Astrophysics Data System (ADS)
Chan, P. W.
2009-03-01
The Hong Kong International Airport (HKIA) is situated in an area of complex terrain. Turbulent flow due to terrain disruption could occur in the vicinity of HKIA when winds from east to southwest climb over Lantau Island, a mountainous island to the south of the airport. Low-level turbulence is an aviation hazard to the aircraft flying into and out of HKIA. It is closely monitored using remote-sensing instruments including Doppler LIght Detection And Ranging (LIDAR) systems and wind profilers in the airport area. Forecasting of low-level turbulence by numerical weather prediction models would be useful in the provision of timely turbulence warnings to the pilots. The feasibility of forecasting eddy dissipation rate (EDR), a measure of turbulence intensity adopted in the international civil aviation community, is studied in this paper using the Regional Atmospheric Modelling System (RAMS). Super-high resolution simulation (within the regime of large eddy simulation) is performed with a horizontal grid size down to 50 m for some typical cases of turbulent airflow at HKIA, such as spring-time easterly winds in a stable boundary layer and gale-force southeasterly winds associated with a typhoon. Sensitivity of the simulation results with respect to the choice of turbulent kinetic energy (TKE) parameterization scheme in RAMS is also examined. RAMS simulation with Deardorff (1980) TKE scheme is found to give the best result in comparison with actual EDR observations. It has the potential for real-time forecasting of low-level turbulence in short-term aviation applications (viz. for the next several hours).
A Hydrodynamic Theory for Spatially Inhomogeneous Semiconductor Lasers. 2; Numerical Results
NASA Technical Reports Server (NTRS)
Li, Jianzhong; Ning, C. Z.; Biegel, Bryan A. (Technical Monitor)
2001-01-01
We present numerical results of the diffusion coefficients (DCs) in the coupled diffusion model derived in the preceding paper for a semiconductor quantum well. These include self and mutual DCs in the general two-component case, as well as density- and temperature-related DCs under the single-component approximation. The results are analyzed from the viewpoint of free Fermi gas theory with many-body effects incorporated. We discuss in detail the dependence of these DCs on densities and temperatures in order to identify different roles played by the free carrier contributions including carrier statistics and carrier-LO phonon scattering, and many-body corrections including bandgap renormalization and electron-hole (e-h) scattering. In the general two-component case, it is found that the self- and mutual- diffusion coefficients are determined mainly by the free carrier contributions, but with significant many-body corrections near the critical density. Carrier-LO phonon scattering is dominant at low density, but e-h scattering becomes important in determining their density dependence above the critical electron density. In the single-component case, it is found that many-body effects suppress the density coefficients but enhance the temperature coefficients. The modification is of the order of 10% and reaches a maximum of over 20% for the density coefficients. Overall, temperature elevation enhances the diffusive capability or DCs of carriers linearly, and such an enhancement grows with density. Finally, the complete dataset of various DCs as functions of carrier densities and temperatures provides necessary ingredients for future applications of the model to various spatially inhomogeneous optoelectronic devices.
NASA Astrophysics Data System (ADS)
Barnes, T.
In this article we review numerical studies of the quantum Heisenberg antiferromagnet on a square lattice, which is a model of the magnetic properties of the undoped “precursor insulators” of the high temperature superconductors. We begin with a brief pedagogical introduction and then discuss zero and nonzero temperature properties and compare the numerical results to analytical calculations and to experiment where appropriate. We also review the various algorithms used to obtain these results, and discuss algorithm developments and improvements in computer technology which would be most useful for future numerical work in this area. Finally we list several outstanding problems which may merit further investigation.
Spinel dissolution via addition of glass forming chemicals. Results of preliminary experiments
Fox, K. M.; Johnson, F. C.
2015-11-01
Increased loading of high level waste in glass can lead to crystallization within the glass. Some crystalline species, such as spinel, have no practical impact on the chemical durability of the glass, and therefore may be acceptable from both a processing and a product performance standpoint. In order to operate a melter with a controlled amount of crystallization, options must be developed for remediating an unacceptable accumulation of crystals. This report describes preliminary experiments designed to evaluate the ability to dissolve spinel crystals in simulated waste glass melts via the addition of glass forming chemicals (GFCs).
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
Preliminary results of numerical investigations at SECARB Cranfield, MS field test site
NASA Astrophysics Data System (ADS)
Choi, J.; Nicot, J.; Meckel, T. A.; Chang, K.; Hovorka, S. D.
2008-12-01
The Southeast Regional Carbon Sequestration partnership sponsored by DOE has chosen the Cranfield, MS field as a test site for its Phase II experiment. It will provide information on CO2 storage in oil and gas fields, in particular on storage permanence, storage capacity, and pressure buildup as well as on sweep efficiency. The 10,300 ft-deep reservoir produced 38 MMbbl of oil and 677 MMSCF of gas from the 1940's to the 1960's and is being retrofitted by Denbury Resources for tertiary recovery. CO2 injection started in July 2008 with a scheduled ramp up during the next few months. The Cranfield modeling team selected the northern section of the field for development of a numerical model using the multiphase-flow, compositional CMG-GEM software. Model structure was determined through interpretation of logs from old and recently-drilled wells and geophysical data. PETREL was used to upscale and export permeability and porosity data to the GEM model. Preliminary sensitivity analyses determined that relative permeability parameters and oil composition had the largest impact on CO2 behavior. The first modeling step consisted in history-matching the total oil, gas, and water production out of the reservoir starting from its natural state to determine the approximate current conditions of the reservoir. The fact that pressure recovered in the 40 year interval since end of initial production helps in constraining boundary conditions. In a second step, the modeling focused on understanding pressure evolution and CO2 transport in the reservoir. The presentation will introduce preliminary results of the simulations and confirm/explain discrepancies with field measurements.
NASA Astrophysics Data System (ADS)
Henne, Stephan; Kaufmann, Pirmin; Schraner, Martin; Brunner, Dominik
2013-04-01
The Lagrangian particle dispersion model FLEXPART is a well-known and robust research tool used by many atmospheric scientists worldwide. In its standard version FLEXPART was developed for the use with global or limited area input files from the European Centre for Medium Range Weather Forecast (ECMWF). Further versions exist for input from the NCEP (National Centers for Environmental Prediction) GFS (Global Forecasting System) model and for regional scale input from the MM5 model and its successor WRF. In Europe several national weather services and research groups develop and operate the non-hydrostatic limited-area atmospheric model COSMO (Consortium for Small-scale Modeling). At MeteoSwiss COSMO is operationally run with data assimilation on two grids with approximately 7 km x 7 km and 2 km x 2 km horizontal resolution centered over Switzerland This offers the exceptional opportunity of studying atmospheric transport over complex terrain on an long-term basis. To this end, we have developed a new version of FLEXPART that is offline coupled to COSMO output (FLEXPART-COSMO hereafter) and supports output from multiple COSMO nests. The version features several new developments as compared to the standard version. Most importantly, particles are internally referenced against the native vertical coordinate system used in COSMO and not, as in standard FLEXPART, in a terrain following z-system. This eliminates the need for an additional interpolation step. A new flux deaccumulation scheme was introduced that removes the need for additional preprocessing of the input files. In addition to the existing Emmanuel based convection parameterisation, a convection parameterisation based on the Tiedtke scheme, which is identical to the one implemented in COSMO itself, was introduced. A possibility for offline nesting of a FLEXPART-COSMO run into a FLEXPART-ECMWF run for backward simulations was developed that only requires minor modifications on the FLEXPART-ECMWF version and
Fujimoto, Hiroyuki; Kato, Koichi; Iwata, Hiroo
2009-01-01
The electroporation microarray is a useful tool for high-throughput analysis of gene functions. However, transfection efficiency is greatly impaired by storage of the microarrays, due to water evaporation from arrayed nucleotides. In this study, we aimed at evaluating the effect of saccharides and sugar alcohols, added to the solution of the plasmid DNA or small interfering RNA (siRNA). Microarrays loaded with plasmids and siRNAs were prepared with various polyols including sugars and sugar alcohols. After storage of these microarrays at different temperatures for various time periods, transfection efficiency was evaluated using human embryonic kidney cells. In the case of plasmid-loaded microarrays, addition of monosaccharides (glucose, fructose), disaccharides (trehalose, sucrose), and trisaccharide (raffinose) served to retain transfection efficiency at a reasonably high level after storage at -20 degrees C. The observed effects may be because moisture retention serves to maintain the solubility of DNA. In contrast, polysaccharide (dextran) and sugar alcohol (glycerol) had insignificant effects on retention of transfection efficiency. On the other hand, addition of saccharides and sugar alcohols had insignificant effects on the transfection of siRNA after storage of a microarray at 25 degrees C for 7 days, presumably due to the intrinsically-high solubility of siRNA which consists of short nucleotides. PMID:18989662
NASA Astrophysics Data System (ADS)
Gliko, A. O.; Molodenskii, S. M.
2015-01-01
) are not only capable of significantly changing the magnitude of the radial displacements of the geoid but also altering their sign. Moreover, even in the uniform Earth's model, the effects of sphericity of its external surface and self-gravitation can also provide a noticeable contribution, which determines the signs of the coefficients in the expansion of the geoid's shape in the lower-order spherical functions. In order to separate these effects, below we present the results of the numerical calculations of the total effects of thermoelastic deformations for the two simplest models of spherical Earth without and with self-gravitation with constant density and complex-valued shear moduli and for the real Earth PREM model (which describes the depth distributions of density and elastic moduli for the high-frequency oscillations disregarding the rheology of the medium) and the modern models of the mantle rheology. Based on the calculations, we suggest the simplest interpretation of the present-day data on the relationship between the coefficients of spherical expansion of temperature, velocities of seismic body waves, the topography of the Earth's surface and geoid, and the data on the correlation between the lower-order coefficients in the expansions of the geoid and the corresponding terms of the expansions of horizontal inhomogeneities in seismic velocities. The suggested interpretation includes the estimates of the sign and magnitude for the ratios between the first coefficients of spherical expansions of seismic velocities, topography, and geoid. The presence of this correlation and the relationship between the signs and absolute values of these coefficients suggests that both the long-period oscillations of the geoid and the long-period variations in the velocities of seismic body waves are largely caused by thermoelastic deformations.
NASA Astrophysics Data System (ADS)
Heinze, Thomas; Galvan, Boris; Miller, Stephen
2013-04-01
Fluid-rock interactions are mechanically fundamental to many earth processes, including fault zones and hydrothermal/volcanic systems, and to future green energy solutions such as enhanced geothermal systems and carbon capture and storage (CCS). Modeling these processes is challenging because of the strong coupling between rock fracture evolution and the consequent large changes in the hydraulic properties of the system. In this talk, we present results of a numerical model that includes poro-elastic plastic rheology (with hardening, softening, and damage), and coupled to a non-linear diffusion model for fluid pressure propagation and two-phase fluid flow. Our plane strain model is based on the poro- elastic plastic behavior of porous rock and is advanced with hardening, softening and damage using the Mohr- Coulomb failure criteria. The effective stress model of Biot (1944) is used for coupling the pore pressure and the rock behavior. Frictional hardening and cohesion softening are introduced following Vermeer and de Borst (1984) with the angle of internal friction and the cohesion as functions of the principal strain rates. The scalar damage coefficient is assumed to be a linear function of the hardening parameter. Fluid injection is modeled as a two phase mixture of water and air using the Richards equation. The theoretical model is solved using finite differences on a staggered grid. The model is benchmarked with experiments on the laboratory scale in which fluid is injected from below in a critically-stressed, dry sandstone (Stanchits et al. 2011). We simulate three experiments, a) the failure a dry specimen due to biaxial compressive loading, b) the propagation a of low pressure fluid front induced from the bottom in a critically stressed specimen, and c) the failure of a critically stressed specimen due to a high pressure fluid intrusion. Comparison of model results with the fluid injection experiments shows that the model captures most of the experimental
Numerical Analysis of Large Telescopes in Terms of Induced Loads and Resulting Geometrical Stability
NASA Astrophysics Data System (ADS)
Upnere, S.; Jekabsons, N.; Joffe, R.
2013-03-01
Comprehensive numerical studies, involving structural and Computational Fluid Dynamics (CFD) analysis, have been carried out at the Engineering Research Institute "Ventspils International Radio Astron- omy Center" (VIRAC) of the Ventspils University College to investigate the gravitational and wind load effects on large, ground-based radio tele- scopes RT-32 performance. Gravitational distortions appear to be the main limiting factor for the reflector performance in everyday operation. Random loads caused by wind gusts (unavoidable at zenith) contribute to the fatigue accumulation.
Chaotic structures of nonlinear magnetic fields. I - Theory. II - Numerical results
NASA Technical Reports Server (NTRS)
Lee, Nam C.; Parks, George K.
1992-01-01
A study of the evolutionary properties of nonlinear magnetic fields in flowing MHD plasmas is presented to illustrate that nonlinear magnetic fields may involve chaotic dynamics. It is shown how a suitable transformation of the coupled equations leads to Duffing's form, suggesting that the behavior of the general solution can also be chaotic. Numerical solutions of the nonlinear magnetic field equations that have been cast in the form of Duffing's equation are presented.
XLF deficiency results in reduced N-nucleotide addition during V(D)J recombination
IJspeert, Hanna; Rozmus, Jacob; Schwarz, Klaus; Warren, René L.; van Zessen, David; Holt, Robert A.; Pico-Knijnenburg, Ingrid; Simons, Erik; Jerchel, Isabel; Wawer, Angela; Lorenz, Myriam; Patıroğlu, Turkan; Akar, Himmet Haluk; Leite, Ricardo; Verkaik, Nicole S.; Stubbs, Andrew P.; van Gent, Dik C.; van Dongen, Jacques J. M.
2016-01-01
Repair of DNA double-strand breaks (DSBs) by the nonhomologous end-joining pathway (NHEJ) is important not only for repair of spontaneous breaks but also for breaks induced in developing lymphocytes during V(D)J (variable [V], diversity [D], and joining [J] genes) recombination of their antigen receptor loci to create a diverse repertoire. Mutations in the NHEJ factor XLF result in extreme sensitivity for ionizing radiation, microcephaly, and growth retardation comparable to mutations in LIG4 and XRCC4, which together form the NHEJ ligation complex. However, the effect on the immune system is variable (mild to severe immunodeficiency) and less prominent than that seen in deficiencies of NHEJ factors ARTEMIS and DNA-dependent protein kinase catalytic subunit, with defects in the hairpin opening step, which is crucial and unique for V(D)J recombination. Therefore, we aimed to study the role of XLF during V(D)J recombination. We obtained clinical data from 9 XLF-deficient patients and performed immune phenotyping and antigen receptor repertoire analysis of immunoglobulin (Ig) and T-cell receptor (TR) rearrangements, using next-generation sequencing in 6 patients. The results were compared with XRCC4 and LIG4 deficiency. Both Ig and TR rearrangements showed a significant decrease in the number of nontemplated (N) nucleotides inserted by terminal deoxynucleotidyl transferase, which resulted in a decrease of 2 to 3 amino acids in the CDR3. Such a reduction in the number of N-nucleotides has a great effect on the junctional diversity, and thereby on the total diversity of the Ig and TR repertoire. This shows that XLF has an important role during V(D)J recombination in creating diversity of the repertoire by stimulating N-nucleotide insertion. PMID:27281794
XLF deficiency results in reduced N-nucleotide addition during V(D)J recombination.
IJspeert, Hanna; Rozmus, Jacob; Schwarz, Klaus; Warren, René L; van Zessen, David; Holt, Robert A; Pico-Knijnenburg, Ingrid; Simons, Erik; Jerchel, Isabel; Wawer, Angela; Lorenz, Myriam; Patıroğlu, Turkan; Akar, Himmet Haluk; Leite, Ricardo; Verkaik, Nicole S; Stubbs, Andrew P; van Gent, Dik C; van Dongen, Jacques J M; van der Burg, Mirjam
2016-08-01
Repair of DNA double-strand breaks (DSBs) by the nonhomologous end-joining pathway (NHEJ) is important not only for repair of spontaneous breaks but also for breaks induced in developing lymphocytes during V(D)J (variable [V], diversity [D], and joining [J] genes) recombination of their antigen receptor loci to create a diverse repertoire. Mutations in the NHEJ factor XLF result in extreme sensitivity for ionizing radiation, microcephaly, and growth retardation comparable to mutations in LIG4 and XRCC4, which together form the NHEJ ligation complex. However, the effect on the immune system is variable (mild to severe immunodeficiency) and less prominent than that seen in deficiencies of NHEJ factors ARTEMIS and DNA-dependent protein kinase catalytic subunit, with defects in the hairpin opening step, which is crucial and unique for V(D)J recombination. Therefore, we aimed to study the role of XLF during V(D)J recombination. We obtained clinical data from 9 XLF-deficient patients and performed immune phenotyping and antigen receptor repertoire analysis of immunoglobulin (Ig) and T-cell receptor (TR) rearrangements, using next-generation sequencing in 6 patients. The results were compared with XRCC4 and LIG4 deficiency. Both Ig and TR rearrangements showed a significant decrease in the number of nontemplated (N) nucleotides inserted by terminal deoxynucleotidyl transferase, which resulted in a decrease of 2 to 3 amino acids in the CDR3. Such a reduction in the number of N-nucleotides has a great effect on the junctional diversity, and thereby on the total diversity of the Ig and TR repertoire. This shows that XLF has an important role during V(D)J recombination in creating diversity of the repertoire by stimulating N-nucleotide insertion. PMID:27281794
Coupled transport processes in semipermeable media. Part 2: Numerical method and results
NASA Astrophysics Data System (ADS)
Jacobsen, Janet S.; Carnahan, Chalon L.
1990-04-01
A numerical simulator has been developed to investigate the effects of coupled processes on heat and mass transport in semipermeable media. The governing equations on which the simulator is based were derived using the thermodynamics of irreversible processes. The equations are nonlinear and have been solved numerically using the n-dimensional Newton's method. As an example of an application, the numerical simulator has been used to investigate heat and solute transport in the vicinity of a heat source buried in a saturated clay-like medium, in part to study solute transport in bentonite packing material surrounding a nuclear waste canister. The coupled processes considered were thermal filtration, thermal osmosis, chemical osmosis and ultrafiltration. In the simulations, heat transport by coupled processes was negligible compared to heat conduction, but pressure and solute migration were affected. Solute migration was retarded relative to the uncoupled case when only chemical osmosis was considered. When both chemical osmosis and thermal osmosis were included, solute migration was enhanced.
Aircraft-Produced Ice Particles (APIPs): Additional Results and Further Insights.
NASA Astrophysics Data System (ADS)
Woodley, William L.; Gordon, Glenn; Henderson, Thomas J.; Vonnegut, Bernard; Rosenfeld, Daniel; Detwiler, Andrew
2003-05-01
This paper presents new results from studies of aircraft-produced ice particles (APIPs) in supercooled fog and clouds. Nine aircraft, including a Beech King Air 200T cloud physics aircraft, a Piper Aztec, a Cessna 421-C, two North American T-28s, an Aero Commander, a Piper Navajo, a Beech Turbo Baron, and a second four-bladed King Air were involved in the tests. The instrumented King Air served as the monitoring aircraft for trails of ice particles created, or not created, when the other aircraft were flown through clouds at various temperatures and served as both the test and monitoring aircraft when it itself was tested. In some cases sulfur hexafluoride (SF6) gas was released by the test aircraft during its test run and was detected by the King Air during its monitoring passes to confirm the location of the test aircraft wake. Ambient temperatures for the tests ranged between 5° and 12°C. The results confirm earlier published results and provide further insights into the APIPs phenomenon. The King Air at ambient temperatures less than 8°C can produce APIPs readily. The Piper Aztec and the Aero Commander also produced APIPs under the test conditions in which they were flown. The Cessna 421, Piper Navajo, and Beech Turbo Baron did not. The APIPs production potential of a T-28 is still indeterminate because a limited range of conditions was tested. Homogeneous nucleation in the adiabatically cooled regions where air is expanding around the rapidly rotating propeller tips is the cause of APIPs. An equation involving the propeller efficiency, engine thrust, and true airspeed of the aircraft is used along with the published thrust characteristics of the propellers to predict when the aircraft will produce APIPs. In most cases the predictions agree well with the field tests. Of all of the aircraft tested, the Piper Aztec, despite its small size and low horsepower, was predicted to be the most prolific producer of APIPs, and this was confirmed in field tests. The
NASA Astrophysics Data System (ADS)
Morvan, D.
2010-12-01
behaviour of forest fires, based on a multiphase formulation. This approach consists in solving the balance equations (mass, momentum, energy, chemical species, radiation intensity …) governing the coupled system formed by the vegetation and the surrounding atmosphere. The vegetation was represented as a collection of solid fuel particles, regrouped in families, each one characterized by its own set of physical variables (mass fraction of water, of dry matter, of char, temperature, volume fraction, density, surface area to volume ratio …) necessary to describe the evolution of its state during the propagation of fire. Some numerical results were then presented and compared with available experimental data. A particular attention was taken to simulate surface fires propagating through grassland and Mediterranean shrubland for which a large experimental data base exists. We conclude our paper, in presenting some recent results obtained in a more operational context, to simulate the interaction between two fire fronts (head fire and backfire) in conditions similar to two those encountered during a suppression fire operation.
Kam, Seung I.; Gauglitz, Phillip A. ); Rossen, William R.
2000-12-01
The goal of this study is to fit model parameters to changes in waste level in response to barometric pressure changes in underground storage tanks at the Hanford Site. This waste compressibility is a measure of the quantity of gas, typically hydrogen and other flammable gases that can pose a safety hazard, retained in the waste. A one-dimensional biconical-pore-network model for compressibility of a bubbly slurry is presented in a companion paper. Fitting these results to actual waste level changes in the tanks implies that bubbles are long in the slurry layer and the ratio of pore-body radius to pore-throat radius is close to one; unfortunately, capillary effects can not be quantified unambiguously from the data without additional information on pore geometry. Therefore determining the quantity of gas in the tanks requires more than just slurry volume data. Similar ambiguity also exists with two other simple models: a capillary-tube model with contact angle hysteresis and spherical-p ore model.
Durham, M.D.
1993-04-16
Several tasks have been completed in a program to evaluate additives to improve fine particle collection in electrostatic precipitators. Screening tests and laboratory evaluations of additives are summarized in this report. Over 20 additives were evaluated; four were found to improve flyash precipitation rates. The Insitec particle analyzer was also evaluated; test results show that the analyzer will provide accurate sizing and counting information for particles in the size range of {le} 10 {mu}m dia.
Nitrogen Addition as a Result of Long-Term Root Removal Affects Soil Organic Matter Dynamics
NASA Astrophysics Data System (ADS)
Crow, S. E.; Lajtha, K.
2004-12-01
A long-term field litter manipulation site was established in a mature coniferous forest stand at the H.J. Andrews Experimental Forest, OR, USA in 1997 in order to address how detrital inputs influence soil organic matter formation and accumulation. Soils at this site are Andisols and are characterized by high carbon (C) and low nitrogen (N) contents, due largely to the legacy of woody debris and extremely low atmospheric N deposition. Detrital treatments include trenching to remove roots, doubling wood and needle litter, and removing aboveground litter. In order to determine whether five years of detrital manipulation had altered organic matter quantity and lability at this site, soil from the top 0-5 cm of the A horizon was density fractionated to separate the labile light fraction (LF) from the more recalcitrant mineral soil in the heavy fraction (HF). Both density fractions and whole soils were incubated for one year in chambers designed such that repeated measurements of soil respiration and leachate chemistry could be made. Trenching resulted in the removal of labile root inputs from root exudates and turnover of fine roots and active mycorrhizal communities as well as an increase of available N by removing plant uptake. Since 1999, soil solution chemistry from tension lysimeters has shown greater total N and dissolved organic nitrogen (DON) flux and less dissolved organic carbon (DOC) flux to stream flow in the trenched plots relative to the other detrital treatments. C/N ratio and C content of both light and heavy fractions from the trenched plots were greater than other detrital treatments. In the lab incubation, over the course of a year C mineralization from these soils was suppressed. Cumulative DOC losses and CO2 efflux both were significantly less in soils from trenched plots than in other detrital treatments including controls. After day 150 of the incubation, leachates from the HF of plots with trenched treatments had a DOC/DON ratio significantly
Ponderomotive stabilization of flute modes in mirrors Feedback control and numerical results
NASA Technical Reports Server (NTRS)
Similon, P. L.
1987-01-01
Ponderomotive stabilization of rigid plasma flute modes is numerically investigated by use of a variational principle, for a simple geometry, without eikonal approximation. While the near field of the studied antenna can be stabilizing, the far field has a small contribution only, because of large cancellation by quasi mode-coupling terms. The field energy for stabilization is evaluated and is a nonnegligible fraction of the plasma thermal energy. A new antenna design is proposed, and feedback stabilization is investigated. Their use drastically reduces power requirements.
Code of Federal Regulations, 2012 CFR
2012-04-01
... materials for animal feed and pet food. 570.14 Section 570.14 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL DRUGS, FEEDS, AND RELATED PRODUCTS FOOD ADDITIVES General Provisions § 570.14 Indirect food additives resulting from packaging materials for animal feed...
Code of Federal Regulations, 2010 CFR
2010-04-01
... materials for animal feed and pet food. 570.14 Section 570.14 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL DRUGS, FEEDS, AND RELATED PRODUCTS FOOD ADDITIVES General Provisions § 570.14 Indirect food additives resulting from packaging materials for animal feed...
Code of Federal Regulations, 2013 CFR
2013-04-01
... materials for animal feed and pet food. 570.14 Section 570.14 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL DRUGS, FEEDS, AND RELATED PRODUCTS FOOD ADDITIVES General Provisions § 570.14 Indirect food additives resulting from packaging materials for animal feed...
Code of Federal Regulations, 2014 CFR
2014-04-01
... materials for animal feed and pet food. 570.14 Section 570.14 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL DRUGS, FEEDS, AND RELATED PRODUCTS FOOD ADDITIVES General Provisions § 570.14 Indirect food additives resulting from packaging materials for animal feed...
Code of Federal Regulations, 2011 CFR
2011-04-01
... materials for animal feed and pet food. 570.14 Section 570.14 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL DRUGS, FEEDS, AND RELATED PRODUCTS FOOD ADDITIVES General Provisions § 570.14 Indirect food additives resulting from packaging materials for animal feed...
Fanselau, R.W.; Thakkar, J.G.; Hiestand, J.W.; Cassell, D.
1981-03-01
The Comparative Thermal-Hydraulic Evaluation of Steam Generators program represents an analytical investigation of the thermal-hydraulic characteristics of four PWR steam generators. The analytical tool utilized in this investigation is the CALIPSOS code, a three-dimensional flow distribution code. This report presents the steady state thermal-hydraulic characteristics on the secondary side of a Westinghouse Model 51 steam generator. Details of the CALIPSOS model with accompanying assumptions, operating parameters, and transport correlations are identified. Comprehensive graphical and numerical results are presented to facilitate the desired comparison with other steam generators analyzed by the same flow distribution code.
NASA Astrophysics Data System (ADS)
Conti, Livia; De Gregorio, Paolo; Bonaldi, Michele; Borrielli, Antonio; Crivellari, Michele; Karapetyan, Gagik; Poli, Charles; Serra, Enrico; Thakur, Ram-Krishna; Rondoni, Lamberto
2012-06-01
We study experimentally, numerically, and theoretically the elastic response of mechanical resonators along which the temperature is not uniform, as a consequence of the onset of steady-state thermal gradients. Two experimental setups and designs are employed, both using low-loss materials. In both cases, we monitor the resonance frequencies of specific modes of vibration, as they vary along with variations of temperatures and of temperature differences. In one case, we consider the first longitudinal mode of vibration of an aluminum alloy resonator; in the other case, we consider the antisymmetric torsion modes of a silicon resonator. By defining the average temperature as the volume-weighted mean of the temperatures of the respective elastic sections, we find out that the elastic response of an object depends solely on it, regardless of whether a thermal gradient exists and, up to 10% imbalance, regardless of its magnitude. The numerical model employs a chain of anharmonic oscillators, with first- and second-neighbor interactions and temperature profiles satisfying Fourier's Law to a good degree. Its analysis confirms, for the most part, the experimental findings and it is explained theoretically from a statistical mechanics perspective with a loose notion of local equilibrium.
Estimation of geopotential from satellite-to-satellite range rate data: Numerical results
NASA Technical Reports Server (NTRS)
Thobe, Glenn E.; Bose, Sam C.
1987-01-01
A technique for high-resolution geopotential field estimation by recovering the harmonic coefficients from satellite-to-satellite range rate data is presented and tested against both a controlled analytical simulation of a one-day satellite mission (maximum degree and order 8) and then against a Cowell method simulation of a 32-day mission (maximum degree and order 180). Innovations include: (1) a new frequency-domain observation equation based on kinetic energy perturbations which avoids much of the complication of the usual Keplerian element perturbation approaches; (2) a new method for computing the normalized inclination functions which unlike previous methods is both efficient and numerically stable even for large harmonic degrees and orders; (3) the application of a mass storage FFT to the entire mission range rate history; (4) the exploitation of newly discovered symmetries in the block diagonal observation matrix which reduce each block to the product of (a) a real diagonal matrix factor, (b) a real trapezoidal factor with half the number of rows as before, and (c) a complex diagonal factor; (5) a block-by-block least-squares solution of the observation equation by means of a custom-designed Givens orthogonal rotation method which is both numerically stable and tailored to the trapezoidal matrix structure for fast execution.
Interaction of a mantle plume and a segmented mid-ocean ridge: Results from numerical modeling
NASA Astrophysics Data System (ADS)
Georgen, Jennifer E.
2014-04-01
Previous investigations have proposed that changes in lithospheric thickness across a transform fault, due to the juxtaposition of seafloor of different ages, can impede lateral dispersion of an on-ridge mantle plume. The application of this “transform damming” mechanism has been considered for several plume-ridge systems, including the Reunion hotspot and the Central Indian Ridge, the Amsterdam-St. Paul hotspot and the Southeast Indian Ridge, the Cobb hotspot and the Juan de Fuca Ridge, the Iceland hotspot and the Kolbeinsey Ridge, the Afar plume and the ridges of the Gulf of Aden, and the Marion/Crozet hotspot and the Southwest Indian Ridge. This study explores the geodynamics of the transform damming mechanism using a three-dimensional finite element numerical model. The model solves the coupled steady-state equations for conservation of mass, momentum, and energy, including thermal buoyancy and viscosity that is dependent on pressure and temperature. The plume is introduced as a circular thermal anomaly on the bottom boundary of the numerical domain. The center of the plume conduit is located directly beneath a spreading segment, at a distance of 200 km (measured in the along-axis direction) from a transform offset with length 100 km. Half-spreading rate is 0.5 cm/yr. In a series of numerical experiments, the buoyancy flux of the modeled plume is progressively increased to investigate the effects on the temperature and velocity structure of the upper mantle in the vicinity of the transform. Unlike earlier studies, which suggest that a transform always acts to decrease the along-axis extent of plume signature, these models imply that the effect of a transform on plume dispersion may be complex. Under certain ranges of plume flux modeled in this study, the region of the upper mantle undergoing along-axis flow directed away from the plume could be enhanced by the three-dimensional velocity and temperature structure associated with ridge
NASA Astrophysics Data System (ADS)
Blecka, Maria I.
2010-05-01
The passive remote spectrometric methods are important in examinations the atmospheres of planets. The radiance spectra inform us about values of thermodynamical parameters and composition of the atmospheres and surfaces. The spectral technology can be useful in detection of the trace aerosols like biological substances (if present) in the environments of the planets. We discuss here some of the aspects related to the spectroscopic search for the aerosols and dust in planetary atmospheres. Possibility of detection and identifications of biological aerosols with a passive InfraRed spectrometer in an open-air environment is discussed. We present numerically simulated, based on radiative transfer theory, spectroscopic observations of the Earth atmosphere. Laboratory measurements of transmittance of various kinds of aerosols, pollens and bacterias were used in modeling.
NASA Technical Reports Server (NTRS)
Aveiro, H. C.; Hysell, D. L.; Caton, R. G.; Groves, K. M.; Klenzing, J.; Pfaff, R. F.; Stoneback, R.; Heelis, R. A.
2012-01-01
A three-dimensional numerical simulation of plasma density irregularities in the postsunset equatorial F region ionosphere leading to equatorial spread F (ESF) is described. The simulation evolves under realistic background conditions including bottomside plasma shear flow and vertical current. It also incorporates C/NOFS satellite data which partially specify the forcing. A combination of generalized Rayleigh-Taylor instability (GRT) and collisional shear instability (CSI) produces growing waveforms with key features that agree with C/NOFS satellite and ALTAIR radar observations in the Pacific sector, including features such as gross morphology and rates of development. The transient response of CSI is consistent with the observation of bottomside waves with wavelengths close to 30 km, whereas the steady state behavior of the combined instability can account for the 100+ km wavelength waves that predominate in the F region.
Numerical results on the transcendence of constants involving pi, e, and Euler's constant
NASA Technical Reports Server (NTRS)
Bailey, David H.
1988-01-01
The existence of simple polynomial equations (integer relations) for the constants e/pi, e + pi, log pi, gamma (Euler's constant), e exp gamma, gamma/e, gamma/pi, and log gamma is investigated by means of numerical computations. The recursive form of the Ferguson-Fourcade algorithm (Ferguson and Fourcade, 1979; Ferguson, 1986 and 1987) is implemented on the Cray-2 supercomputer at NASA Ames, applying multiprecision techniques similar to those described by Bailey (1988) except that FFTs are used instead of dual-prime-modulus transforms for multiplication. It is shown that none of the constants has an integer relation of degree eight or less with coefficients of Euclidean norm 10 to the 9th or less.
NASA Technical Reports Server (NTRS)
Rigby, D. L.; Van Fossen, G. J.
1992-01-01
A study of the effect of spanwise variation on leading edge heat transfer is presented. Experimental and numerical results are given for a circular leading edge and for a 3:1 elliptical leading edge. It is demonstrated that increases in leading edge heat transfer due to spanwise variations in freestream momentum are comparable to those due to freestream turbulence.
Numerical study of the wind energy potential in Bulgaria - Some preliminary results
NASA Astrophysics Data System (ADS)
Jordanov, G.; Gadzhev, G.; Ganev, K.; Miloshev, N.; Syrakov, D.; Prodanova, M.
2012-10-01
The new energy efficiency politics of the EU requires till year 2020 16% of Bulgarian electricity to be produced from renewable sources. The wind is one of renewable energy sources. The ecological benefits of all the kinds of "green" energy are obvious. It is desirable, however, the utilization of renewable energy sources to be as much as possible economically effective. This means that installment of the respective devices (wind farms, solar farms, etc.) should be based on a detailed and reliable evaluation of the real potential of the country. Detailed study of the wind energy potential of the country - spatial distribution, temporal variation, mean and extreme values, fluctuations and statistical characteristics; evaluation from a point of view of industrial applicability can not be made only on the basis of the existing routine meteorological data - the measuring network is not dense enough to catch all the details of the local flow systems, hence of the real wind energy potential of the country spatial distribution. That is why the measurement data has to be supplemented by numerical modeling. The wind field simulations were performed applying the 5th generation PSU/NCAR Meso-Meteorological Model MM5 for years 2000-2007 with a spatial resolution of 3 km over Bulgaria. Some preliminary evaluations of the country wind energy potential, based on the simulation output are demonstrated in the paper.
Mazza, Fabio; Vulcano, Alfonso
2008-07-08
For a widespread application of dissipative braces to protect framed buildings against seismic loads, practical and reliable design procedures are needed. In this paper a design procedure based on the Direct Displacement-Based Design approach is adopted, assuming the elastic lateral storey-stiffness of the damped braces proportional to that of the unbraced frame. To check the effectiveness of the design procedure, presented in an associate paper, a six-storey reinforced concrete plane frame, representative of a medium-rise symmetric framed building, is considered as primary test structure; this structure, designed in a medium-risk region, is supposed to be retrofitted as in a high-risk region, by insertion of diagonal braces equipped with hysteretic dampers. A numerical investigation is carried out to study the nonlinear static and dynamic responses of the primary and the damped braced test structures, using step-by-step procedures described in the associate paper mentioned above; the behaviour of frame members and hysteretic dampers is idealized by bilinear models. Real and artificial accelerograms, matching EC8 response spectrum for a medium soil class, are considered for dynamic analyses.
Accretion of rotating fluids by barytropes - Numerical results for white-dwarf models
NASA Technical Reports Server (NTRS)
Durisen, R. H.
1977-01-01
Numerical sequences of rotating axisymmetric nonmagnetic equilibrium models are constructed which represent the evolution of a barytropic star as it accretes material from a rotating medium. Two accretion geometries are considered - one approximating accretion from a rotating cloud and the other, accretion from a Keplerian disk. It is assumed that some process, such as Ekman spin-up or nonequilibrium oscillations, maintains nearly constant angular velocity along cylinders about the rotation axis. Transport of angular momentum in the cylindrically radial direction by viscosity is included. Fluid instabilities and other physical processes leading to enhancement of this transport are discussed. Particular application is made to zero-temperature white-dwarf models, using the degenerate electron equation of state. An initially nonrotating 0.566-solar-mass white dwarf is followed during the accretion of more than one solar mass of material. Applications to degenerate stellar cores, to mass-transfer binary systems containing white dwarfs, such as novae and dwarf novae, to Type I supernovae, and to galactic X-ray sources are considered.
NASA Astrophysics Data System (ADS)
Szeremley, Daniel; Mussenbrock, Thomas; Brinkmann, Ralf Peter; Zimmermanns, Marc; Rolfes, Ilona; Eremin, Denis; Ruhr-University Bochum, Theoretical Electrical Engineering Team; Ruhr-University Bochum, Institute of Microwave Systems Team
2015-09-01
The market shows in recent years a growing demand for bottles made of polyethylene terephthalate (PET). Therefore, fast and efficient sterilization processes as well as barrier coatings to decrease gas permeation are required. A specialized microwave plasma source - referred to as the plasmaline - has been developed to allow for depositing thin films of e.g. silicon oxid on the inner surface of such PET bottles. The plasmaline is a coaxial waveguide combined with a gas-inlet which is inserted into the empty bottle and initiates a reactive plasma. To optimize and control the different surface processes, it is essential to fully understand the microwave power coupling to the plasma and the related heating of electrons inside the bottle and thus the electromagnetic wave propagation along the plasmaline. In this contribution, we present a detailed dispersion analysis based on a numerical approach. We study how modes of guided waves are propagating under different conditions, if at all. The authors gratefully acknowledge the financial support of the German Research Foundation (DFG) within the framework of the collaborative research centre TRR87.
Recent results from numerical models of the Caribbean Sea and Gulf of Mexico: Do they all agree?
NASA Astrophysics Data System (ADS)
Sheinbaum, J.
2013-05-01
A great variety of numerical models of the Caribbean Sea and Gulf of Mexico have been developed over the years. They all reproduce the basic features of the circulation in the region but do not necessarily agree in the dynamics that explains them. We review recent results related to: 1) semiannual and interannual eddy variability in the Caribbean and their possible role in determining the extension of the western Atlantic warm pool. 2) Loop Current and its eddy shedding dynamics and 3) the deep circulation in the Gulf of Mexico. Recent observations of inertial wave trapping by eddies suggest new veins for numerical research and model comparisons.
Hidden modes in open disordered media: analytical, numerical, and experimental results
NASA Astrophysics Data System (ADS)
Bliokh, Yury P.; Freilikher, Valentin; Shi, Z.; Genack, A. Z.; Nori, Franco
2015-11-01
We explore numerically, analytically, and experimentally the relationship between quasi-normal modes (QNMs) and transmission resonance (TR) peaks in the transmission spectrum of one-dimensional (1D) and quasi-1D open disordered systems. It is shown that for weak disorder there exist two types of the eigenstates: ordinary QNMs which are associated with a TR, and hidden QNMs which do not exhibit peaks in transmission or within the sample. The distinctive feature of the hidden modes is that unlike ordinary ones, their lifetimes remain constant in a wide range of the strength of disorder. In this range, the averaged ratio of the number of transmission peaks {N}{{res}} to the number of QNMs {N}{{mod}}, {N}{{res}}/{N}{{mod}}, is insensitive to the type and degree of disorder and is close to the value \\sqrt{2/5}, which we derive analytically in the weak-scattering approximation. The physical nature of the hidden modes is illustrated in simple examples with a few scatterers. The analogy between ordinary and hidden QNMs and the segregation of superradiant states and trapped modes is discussed. When the coupling to the environment is tuned by an external edge reflectors, the superradiance transition is reproduced. Hidden modes have been also found in microwave measurements in quasi-1D open disordered samples. The microwave measurements and modal analysis of transmission in the crossover to localization in quasi-1D systems give a ratio of {N}{{res}}/{N}{{mod}} close to \\sqrt{2/5}. In diffusive quasi-1D samples, however, {N}{{res}}/{N}{{mod}} falls as the effective number of transmission eigenchannels M increases. Once {N}{{mod}} is divided by M, however, the ratio {N}{{res}}/{N}{{mod}} is close to the ratio found in 1D.
NASA Astrophysics Data System (ADS)
Alhammoud, B.; Béranger, K.; Mortier, L.; Crépon, M.
The Eastern Mediterranean hydrology and circulation are studied by comparing the results of a high resolution primitive equation model (described in dedicated session: Béranger et al.) with observations. The model has a horizontal grid mesh of 1/16o and 43 z-levels in the vertical. The model was initialized with the MODB5 climatology and has been forced during 11 years by the daily sea surface fluxes provided by the European Centre for Medium-range Weather Forecasts analysis in a perpetual year mode corresponding to the year March 1998-February 1999. At the end of the run, the numerical model is able to accurately reproduce the major water masses of the Eastern Mediterranean Basin (Levantine Surface Water, modi- fied Atlantic Water, Levantine Intermediate Water, and Eastern Mediterranean Deep Water). Comparisons with the POEM observations reveal good agreement. While the initial conditions of the model are somewhat different from POEM observations, dur- ing the last year of the simulation, we found that the water mass stratification matches that of the observations quite well in the seasonal mean. During the 11 years of simulation, the model drifts slightly in the layers below the thermocline. Nevertheless, many important physical processes were reproduced. One example is that the dispersal of Adriatic Deep Water into the Levantine Basin is rep- resented. In addition, convective activity located in the northern part of the Levantine Basin occurs in Spring as expected. The surface circulation is in agreement with in-situ and satellite observations. Some well known mesoscale features of the upper thermocline circulation are shown. Sea- sonal variability of transports through Sicily, Otranto and Cretan straits are inves- tigated as well. This work was supported by the french MERCATOR project and SHOM.
Spiegal, R.J.
1984-08-01
For humans exposed to electromagnetic (EM) radiation, the resulting thermophysiologic response is not well understood. Because it is unlikely that this information will be determined from quantitative experimentation, it is necessary to develop theoretical models which predict the resultant thermal response after exposure to EM fields. These calculations are difficult and involved because the human thermoregulatory system is very complex. In this paper, the important numerical models are reviewed and possibilities for future development are discussed.
222Rn transport in a fractured crystalline rock aquifer: Results from numerical simulations
Folger, P.F.; Poeter, E.; Wanty, R.B.; Day, W.; Frishman, D.
1997-01-01
Dissolved 222Rn concentrations in ground water from a small wellfield underlain by fractured Middle Proterozoic Pikes Peak Granite southwest of Denver, Colorado range from 124 to 840 kBq m-3 (3360-22700 pCi L-1). Numerical simulations of flow and transport between two wells show that differences in equivalent hydraulic aperture of transmissive fractures, assuming a simplified two-fracture system and the parallel-plate model, can account for the different 222Rn concentrations in each well under steady-state conditions. Transient flow and transport simulations show that 222Rn concentrations along the fracture profile are influenced by 222Rn concentrations in the adjoining fracture and depend on boundary conditions, proximity of the pumping well to the fracture intersection, transmissivity of the conductive fractures, and pumping rate. Non-homogeneous distribution (point sources) of 222Rn parent radionuclides, uranium and 226Ra, can strongly perturb the dissolved 222Rn concentrations in a fracture system. Without detailed information on the geometry and hydraulic properties of the connected fracture system, it may be impossible to distinguish the influence of factors controlling 222Rn distribution or to determine location of 222Rn point sources in the field in areas where ground water exhibits moderate 222Rn concentrations. Flow and transport simulations of a hypothetical multifracture system consisting of ten connected fractures, each 10 m in length with fracture apertures ranging from 0.1 to 1.0 mm, show that 222Rn concentrations at the pumping well can vary significantly over time. Assuming parallel-plate flow, transmissivities of the hypothetical system vary over four orders of magnitude because transmissivity varies with the cube of fracture aperture. The extreme hydraulic heterogeneity of the simple hypothetical system leads to widely ranging 222Rn values, even assuming homogeneous distribution of uranium and 226Ra along fracture walls. Consequently, it is
Image restoration by the method of convex projections: part 2 applications and numerical results.
Sezan, M I; Stark, H
1982-01-01
The image restoration theory discussed in a previous paper by Youla and Webb [1] is applied to a simulated image and the results compared with the well-known method known as the Gerchberg-Papoulis algorithm. The results show that the method of image restoration by projection onto convex sets, by providing a convenient technique for utilizing a priori information, performs significantly better than the Gerchberg-Papoulis method. PMID:18238262
Field Testing of a Wet FGD Additive for Enhanced Mercury Control - Task 3 Full-scale Test Results
Gary Blythe
2007-05-01
in Texas Lignite Flue Gas; Task 3 - Full-scale FGD Additive Testing in High-sulfur Eastern Bituminous Flue Gas; Task 4 - Pilot Wet Scrubber Additive Tests at Plant Yates; and Task 5 - Full-scale Additive Tests at Plant Yates. The pilot-scale tests were completed in 2005 and have been previously reported. This topical report presents the results from the Task 3 full-scale additive tests, conducted at IPL's Petersburg Station Unit 2. The Task 5 full-scale additive tests will be conducted later in calendar year 2007.
Code of Federal Regulations, 2010 CFR
2010-10-01
... 49 Transportation 8 2010-10-01 2010-10-01 false Additional requirements when filing after an unsatisfactory result from a State, local, or municipal authority affecting the siting of the facility. 1155.23 Section 1155.23 Transportation Other Regulations Relating to Transportation (Continued) SURFACE TRANSPORTATION BOARD, DEPARTMENT...
Multi-Country Experience in Delivering a Joint Course on Software Engineering--Numerical Results
ERIC Educational Resources Information Center
Budimac, Zoran; Putnik, Zoran; Ivanovic, Mirjana; Bothe, Klaus; Zdravkova, Katerina; Jakimovski, Boro
2014-01-01
A joint course, created as a result of a project under the auspices of the "Stability Pact of South-Eastern Europe" and DAAD, has been conducted in several Balkan countries: in Novi Sad, Serbia, for the last six years in several different forms, in Skopje, FYR of Macedonia, for two years, for several types of students, and in Tirana,…
A numerically efficient finite element hydroelastic analysis. Volume 1: Theory and results
NASA Technical Reports Server (NTRS)
Coppolino, R. N.
1976-01-01
Symmetric finite element matrix formulations for compressible and incompressible hydroelasticity are developed on the basis of Toupin's complementary formulation of classical mechanics. Results of implementation of the new technique in the NASTRAN structural analysis program are presented which demonstrate accuracy and efficiency.
NASA Astrophysics Data System (ADS)
Khokhlov, A.; Domínguez, I.; Bacon, C.; Clifford, B.; Baron, E.; Hoeflich, P.; Krisciunas, K.; Suntzeff, N.; Wang, L.
2012-07-01
We describe a new astrophysical version of a cell-based adaptive mesh refinement code ALLA for reactive flow fluid dynamic simulations, including a new implementation of α-network nuclear kinetics, and present preliminary results of first three-dimensional simulations of incomplete carbon-oxygen detonation in Type Ia Supernovae.
NASA Technical Reports Server (NTRS)
Rigby, D. L.; Vanfossen, G. J.
1992-01-01
A study of the effect of spanwise variation in momentum on leading edge heat transfer is discussed. Numerical and experimental results are presented for both a circular leading edge and a 3:1 elliptical leading edge. Reynolds numbers in the range of 10,000 to 240,000 based on leading edge diameter are investigated. The surface of the body is held at a constant uniform temperature. Numerical and experimental results with and without spanwise variations are presented. Direct comparison of the two-dimensional results, that is, with no spanwise variations, to the analytical results of Frossling is very good. The numerical calculation, which uses the PARC3D code, solves the three-dimensional Navier-Stokes equations, assuming steady laminar flow on the leading edge region. Experimentally, increases in the spanwise-averaged heat transfer coefficient as high as 50 percent above the two-dimensional value were observed. Numerically, the heat transfer coefficient was seen to increase by as much as 25 percent. In general, under the same flow conditions, the circular leading edge produced a higher heat transfer rate than the elliptical leading edge. As a percentage of the respective two-dimensional values, the circular and elliptical leading edges showed similar sensitivity to span wise variations in momentum. By equating the root mean square of the amplitude of the spanwise variation in momentum to the turbulence intensity, a qualitative comparison between the present work and turbulent results was possible. It is shown that increases in leading edge heat transfer due to spanwise variations in freestream momentum are comparable to those due to freestream turbulence.
Kunioshi, Nilson; Komori, Seisaku; Fukutani, Seishiro
2006-10-15
A modification of the CHEMKIN II package has been proposed for modeling addition of an arbitrary species at an arbitrary temperature to an arbitrary distance from the burner along a flat flame. The modified program was applied to the problem of addition of acetylene or benzene to different positions of a 40-Torr, {phi}=2.4 benzene/O{sub 2}/40%-N{sub 2} premixed flame to reach final equivalence ratios of {phi}=2.5 and 2.681. The results obtained showed that acetylene addition to early positions of the flame led to significant increase in pyrene production rates, but pyrene concentrations were lower in the flames with acetylene addition in both the {phi}=2.5 and 2.681 cases. Addition of benzene to the flame did not alter pyrene production rates in either the {phi}=2.5 or 2.681 cases; however, for {phi}=2.5, pyrene concentrations increased with benzene addition, while for {phi}=2.681, pyrene contents decreased in comparison to the correspondent flames with no addition. Acetylene addition led to a significant increase in pyrene production rates, but the pyrene levels dropped due to increase in the flow velocity. Pyrene production rates were not sensitive to benzene addition, but pyrene contents increased with benzene addition when the flow velocity decreased. These results show that PAH concentration changes accompanying species addition to flames should be interpreted carefully, because an increase or decrease in the content of a PAH species does not necessarily reflect an effect on its formation rate or mechanism. (author)
Preliminary numerical modeling results - cone penetrometer (CPT) tip used as an electrode
Ramirez, A L
2006-12-19
Figure 1 shows the resistivity models considered in this study; log10 of the resistivity is shown. The graph on the upper left hand side shows a hypothetical resisitivity well log measured along a well in the upper layered model; 10% Gaussian noise has been added to the well log data. The lower model is identical to the upper one except for one square area located within the second deepest layer. Figure 2 shows the electrode configurations considered. The ''reference'' case (upper frame) considers point electrodes located along the surface and along a vertical borehole. The ''CPT electrode'' case (middle frame) assumes that the CPT tip serves as an electrode that is electrically connected to the push rod; the surface electrodes are used in conjuction with the moving CPT electrode. The ''isolated CPT electrode'' case assumes that the electrode at the CPT tip is electrically isolated from the pushrod. Note that the separate CPT push rods in the middle and lower frames are shown separated to clarify the figure; in reality, there is only one pushrod that is changing length as the probe advances. Figure 3 shows three pole-pole measurement schemes were considered; in all cases, the ''get lost'' electrodes were the leftmost and rightmost surface electrodes. The top frame shows the reference scheme where all surface and borehole electrodes can be used. The middle frame shows two possible configurations available when a CPT mounted electrode is used. Note that only one of the four poles can be located along the borehole at any given time; electrode combinations such as the one depicted in blue (upper frame) are not possible in this case. The bottom frame shows a sample configuration where only the surface electrodes are used. Figure 4 shows the results obtained for the various measurement schemes. The white lines show the outline of the true model (shown in Figure 1, upper frame). The starting initial model for these inversions is based on the electrical resistivity log
Spallative nucleosynthesis in supernova remnants. II. Time-dependent numerical results
NASA Astrophysics Data System (ADS)
Parizot, Etienne; Drury, Luke
1999-06-01
We calculate the spallative production of light elements associated with the explosion of an isolated supernova in the interstellar medium, using a time-dependent model taking into account the dilution of the ejected enriched material and the adiabatic energy losses. We first derive the injection function of energetic particles (EPs) accelerated at both the forward and the reverse shock, as a function of time. Then we calculate the Be yields obtained in both cases and compare them to the value implied by the observational data for metal-poor stars in the halo of our Galaxy, using both O and Fe data. We find that none of the processes investigated here can account for the amount of Be found in these stars, which confirms the analytical results of Parizot & Drury (1999). We finally analyze the consequences of these results for Galactic chemical evolution, and suggest that a model involving superbubbles might alleviate the energetics problem in a quite natural way.
Collisional evolution in the Eos and Koronis asteroid families - Observational and numerical results
NASA Technical Reports Server (NTRS)
Binzel, Richard P.
1988-01-01
The origin and evolution of the Eos and Koronis families are addressed by an analysis of Binzel's (1987) observational results. The Maxwellian distribution of the Eos family's rotation rates implies a collisionally-evolved population; these rates are also faster than those of the Koronis family and nonfamily asteroids. While the age of the Eos family may be comparable to the solar system's, that of the Koronis family could be considerably younger. Greater shape irregularity may account for the Koronis family's higher mean lightcurve amplitude.
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. PMID:24881370
Analytical and Numerical Results for an Adhesively Bonded Joint Subjected to Pure Bending
NASA Technical Reports Server (NTRS)
Smeltzer, Stanley S., III; Lundgren, Eric
2006-01-01
A one-dimensional, semi-analytical methodology that was previously developed for evaluating adhesively bonded joints composed of anisotropic adherends and adhesives that exhibit inelastic material behavior is further verified in the present paper. A summary of the first-order differential equations and applied joint loading used to determine the adhesive response from the methodology are also presented. The method was previously verified against a variety of single-lap joint configurations from the literature that subjected the joints to cases of axial tension and pure bending. Using the same joint configuration and applied bending load presented in a study by Yang, the finite element analysis software ABAQUS was used to further verify the semi-analytical method. Linear static ABAQUS results are presented for two models, one with a coarse and one with a fine element meshing, that were used to verify convergence of the finite element analyses. Close agreement between the finite element results and the semi-analytical methodology were determined for both the shear and normal stress responses of the adhesive bondline. Thus, the semi-analytical methodology was successfully verified using the ABAQUS finite element software and a single-lap joint configuration subjected to pure bending.
NASA Astrophysics Data System (ADS)
Helsdon, John H.; Farley, Richard D.
1987-05-01
A recently developed Storm Electrification Model (SEM) has been used to simulate the July 19, 1981, Cooperative Convective Precipitation Experiment (CCOPE) case study cloud. This part of the investigation examines the comparison between the model results and the observations of the actual cloud with respect to its nonelectrical aspects. A timing equivalence is established between the simulation and observations based on an explosive growth phase which was both observed and modeled. This timing equivalence is used as a basis upon which the comparisons are made. The model appears to do a good job of reproducing (in both space and time) many of the observed characteristics of the cloud. These include: (1) the general cloud appearance; (2) cloud size; (3) cloud top rise rate; (4) rapid growth phase; (5) updraft structure; (6) first graupel appearance; (7) first radar echo; (8) qualitative radar range-height indicator evolution; (9) cloud decay; and (10) the location of hydrometers with respect to the updraft/-downdraft structure. Some features that are not accurately modeled are the cloud base height, the maximum liquid water content, and the time from first formation of precipitation until it reaches the ground. While the simulation is not perfect, the faithfulness of the model results to the observations is sufficient to give us confidence that the microphysical processes active in this storm are adequately represented in the model physics. Areas where model improvement is indicated are also discussed.
Numerical predictions and experimental results of a dry bay fire environment.
Suo-Anttila, Jill Marie; Gill, Walter; Black, Amalia Rebecca
2003-11-01
The primary objective of the Safety and Survivability of Aircraft Initiative is to improve the safety and survivability of systems by using validated computational models to predict the hazard posed by a fire. To meet this need, computational model predictions and experimental data have been obtained to provide insight into the thermal environment inside an aircraft dry bay. The calculations were performed using the Vulcan fire code, and the experiments were completed using a specially designed full-scale fixture. The focus of this report is to present comparisons of the Vulcan results with experimental data for a selected test scenario and to assess the capability of the Vulcan fire field model to accurately predict dry bay fire scenarios. Also included is an assessment of the sensitivity of the fire model predictions to boundary condition distribution and grid resolution. To facilitate the comparison with experimental results, a brief description of the dry bay fire test fixture and a detailed specification of the geometry and boundary conditions are included. Overall, the Vulcan fire field model has shown the capability to predict the thermal hazard posed by a sustained pool fire within a dry bay compartment of an aircraft; although, more extensive experimental data and rigorous comparison are required for model validation.
Urban Surface Network In Marseille: Network Optimization Using Numerical Simulations and Results
NASA Astrophysics Data System (ADS)
Pigeon, G.; Lemonsu, A.; Durand, P.; Masson, V.
During the ESCOMPTE program (Field experiment to constrain models of atmo- spheric pollution and emissions transport) in Marseille between june and july 2001 an important device has been set up to describe the urban boundary layer over the built-up aera of Marseille. There was notably a network of 20 temperature and humid- ity sensors which has mesured the spatial and temporal variability of these parameters. Before the experiment the arrangement of the network had been optimized to get the maximum of information about these two varaibilities. We have worked on results of high resolution simulations containing the TEB scheme which represents the energy budgets associated with the gobal street geometry of the mesh. First, a qualitative analysis had enabled the identification of the characteristical phenomenons over the town of Marseille. There are narrows links beetween urban effects and local effects : marine advection and orography. Then, a quantitative analysis of the field has been developped. EOF (empirical orthogonal functions) have been used to characterised the spatial and temporal structures of the field evolution. Instrumented axis have been determined with all these results. Finally, we have choosen very carefully the locations of the instruments at the scale of the street to avoid that micro-climatic effects interfere with the meso-scale effect of the town. The recording of the mesurements, every 10 minutes, had started on the 12th of june and had finished on the 16th of july. We did not get any problem with the instrument and so all the period has been recorded every 10 minutes. The analysis of the datas will be led on different way. First, will be done a temporal study. We want to determine if the times when occur phenomenons are linked to the location in the town. We will interest particulary to the warming during the morning and the cooling during the evening. Then, we will look for correlation between the temperature and mixing ratio with the wind
Numerical results for near surface time domain electromagnetic exploration: a full waveform approach
NASA Astrophysics Data System (ADS)
Sun, H.; Li, K.; Li, X., Sr.; Liu, Y., Sr.; Wen, J., Sr.
2015-12-01
Time domain or Transient electromagnetic (TEM) survey including types with airborne, semi-airborne and ground play important roles in applicants such as geological surveys, ground water/aquifer assess [Meju et al., 2000; Cox et al., 2010], metal ore exploration [Yang and Oldenburg, 2012], prediction of water bearing structures in tunnels [Xue et al., 2007; Sun et al., 2012], UXO exploration [Pasion et al., 2007; Gasperikova et al., 2009] etc. The common practice is introducing a current into a transmitting (Tx) loop and acquire the induced electromagnetic field after the current is cut off [Zhdanov and Keller, 1994]. The current waveforms are different depending on instruments. Rectangle is the most widely used excitation current source especially in ground TEM. Triangle and half sine are commonly used in airborne and semi-airborne TEM investigation. In most instruments, only the off time responses are acquired and used in later analysis and data inversion. Very few airborne instruments acquire the on time and off time responses together. Although these systems acquire the on time data, they usually do not use them in the interpretation.This abstract shows a novel full waveform time domain electromagnetic method and our recent modeling results. The benefits comes from our new algorithm in modeling full waveform time domain electromagnetic problems. We introduced the current density into the Maxwell's equation as the transmitting source. This approach allows arbitrary waveforms, such as triangle, half-sine, trapezoidal waves or scatter record from equipment, being used in modeling. Here, we simulate the establishing and induced diffusion process of the electromagnetic field in the earth. The traditional time domain electromagnetic with pure secondary fields can also be extracted from our modeling results. The real time responses excited by a loop source can be calculated using the algorithm. We analyze the full time gates responses of homogeneous half space and two
Pham, VT.; Silva, L.; Digonnet, H.; Combeaud, C.; Billon, N.; Coupez, T.
2011-05-04
The objective of this work is to model the viscoelastic behaviour of polymer from the solid state to the liquid state. With this objective, we perform experimental tensile tests and compare with simulation results. The chosen polymer is a PMMA whose behaviour depends on its temperature. The computation simulation is based on Navier-Stokes equations where we propose a mixed finite element method with an interpolation P1+/P1 using displacement (or velocity) and pressure as principal variables. The implemented technique uses a mesh composed of triangles (2D) or tetrahedra (3D). The goal of this approach is to model the viscoelastic behaviour of polymers through a fluid-structure coupling technique with a multiphase approach.
Active behavior of abdominal wall muscles: Experimental results and numerical model formulation.
Grasa, J; Sierra, M; Lauzeral, N; Muñoz, M J; Miana-Mena, F J; Calvo, B
2016-08-01
In the present study a computational finite element technique is proposed to simulate the mechanical response of muscles in the abdominal wall. This technique considers the active behavior of the tissue taking into account both collagen and muscle fiber directions. In an attempt to obtain the computational response as close as possible to real muscles, the parameters needed to adjust the mathematical formulation were determined from in vitro experimental tests. Experiments were conducted on male New Zealand White rabbits (2047±34g) and the active properties of three different muscles: Rectus Abdominis, External Oblique and multi-layered samples formed by three muscles (External Oblique, Internal Oblique, and Transversus Abdominis) were characterized. The parameters obtained for each muscle were incorporated into a finite strain formulation to simulate active behavior of muscles incorporating the anisotropy of the tissue. The results show the potential of the model to predict the anisotropic behavior of the tissue associated to fibers and how this influences on the strain, stress and generated force during an isometric contraction. PMID:27111629
Zlochiver, Sharon; Radai, M Michal; Abboud, Shimon; Rosenfeld, Moshe; Dong, Xiu-Zhen; Liu, Rui-Gang; You, Fu-Sheng; Xiang, Hai-Yan; Shi, Xue-Tao
2004-02-01
In electrical impedance tomography (EIT), measurements of developed surface potentials due to applied currents are used for the reconstruction of the conductivity distribution. Practical implementation of EIT systems is known to be problematic due to the high sensitivity to noise of such systems, leading to a poor imaging quality. In the present study, the performance of an induced current EIT (ICEIT) system, where eddy current is applied using magnetic induction, was studied by comparing the voltage measurements to simulated data, and examining the imaging quality with respect to simulated reconstructions for several phantom configurations. A 3-coil, 32-electrode ICEIT system was built, and an iterative modified Newton-Raphson algorithm was developed for the solution of the inverse problem. The RMS norm between the simulated and the experimental voltages was found to be 0.08 +/- 0.05 mV (<3%). Two regularization methods were implemented and compared: the Marquardt regularization and the Laplacian regularization (a bounded second-derivative regularization). While the Laplacian regularization method was found to be preferred for simulated data, it resulted in distinctive spatial artifacts for measured data. The experimental reconstructed images were found to be indicative of the angular positioning of the conductivity perturbations, though the radial sensitivity was low, especially when using the Marquardt regularization method. PMID:15005319
Restricted diffusion in a model acinar labyrinth by NMR: Theoretical and numerical results
NASA Astrophysics Data System (ADS)
Grebenkov, D. S.; Guillot, G.; Sapoval, B.
2007-01-01
A branched geometrical structure of the mammal lungs is known to be crucial for rapid access of oxygen to blood. But an important pulmonary disease like emphysema results in partial destruction of the alveolar tissue and enlargement of the distal airspaces, which may reduce the total oxygen transfer. This effect has been intensively studied during the last decade by MRI of hyperpolarized gases like helium-3. The relation between geometry and signal attenuation remained obscure due to a lack of realistic geometrical model of the acinar morphology. In this paper, we use Monte Carlo simulations of restricted diffusion in a realistic model acinus to compute the signal attenuation in a diffusion-weighted NMR experiment. We demonstrate that this technique should be sensitive to destruction of the branched structure: partial removal of the interalveolar tissue creates loops in the tree-like acinar architecture that enhance diffusive motion and the consequent signal attenuation. The role of the local geometry and related practical applications are discussed.
Buoyancy-driven melt segregation in the earth's moon. I - Numerical results
NASA Technical Reports Server (NTRS)
Delano, J. W.
1990-01-01
The densities of lunar mare magmas have been estimated at liquidus temperatures for pressures from 0 to 47 kbar (0.4 GPa; center of the moon) using a third-order Birch-Murnaghan equation and compositionally dependent parameters from Large and Carmichael (1987). Results on primary magmatic compositions represented by pristine volcanic glasses suggest that the density contrast between very-high-Ti melts and their liquidus olivines may approach zero at pressures of about 25 kbar (2.5 GPa). Since this is the pressure regime of the mantle source regions for these magmas, a compositional limit of eruptability for mare liquids may exist that is similar to the highest Ti melt yet observed among the lunar samples. Although the moon may have generated magmas having greater than 16.4 wt pct TiO2, those melts would probably not have reached the lunar surface due to their high densities, and may have even sunk deeper into the moon's interior as negatively buoyant diapirs. This process may have been important for assimilative interactions in the lunar mantle. The phenomenon of melt/solid density crossover may therefore occur not only in large terrestrial-type objects but also in small objects where, despite low pressures, the range of melt compositions is extreme.
NASA Astrophysics Data System (ADS)
Salcedo-Castro, Julio; Bourgault, Daniel; deYoung, Brad
2011-09-01
The flow caused by the discharge of freshwater underneath a glacier into an idealized fjord is simulated with a 2D non-hydrostatic model. As the freshwater leaves horizontally the subglacial opening into a fjord of uniformly denser water it spreads along the bottom as a jet, until buoyancy forces it to rise. During the initial rising phase, the plume meanders into complex flow patterns while mixing with the surrounding fluid until it reaches the surface and then spreads horizontally as a surface seaward flowing plume of brackish water. The process induces an estuarine-like circulation. Once steady-state is reached, the flow consists of an almost undiluted buoyant plume rising straight along the face of the glacier that turns into a horizontal surface layer thickening as it flows seaward. Over the range of parameters examined, the estuarine circulation is dynamically unstable with gradient Richardson number at the sheared interface having values of <1/4. The surface velocity and dilution factors are strongly and non-linearly related to the Froude number. It is the buoyancy flux that primarily controls the resulting circulation with the momentum flux playing a secondary role.
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.
NASA Astrophysics Data System (ADS)
Pearson, A.; Pizzuto, J. E.
2015-12-01
Previous work at run-of-river (ROR) dams in northern Delaware has shown that bedload supplied to ROR impoundments can be transported over the dam when impoundments remain unfilled. Transport is facilitated by high levels of sand in the impoundment that lowers the critical shear stresses for particle entrainment, and an inversely sloping sediment ramp connecting the impoundment bed (where the water depth is typically equal to the dam height) with the top of the dam (Pearson and Pizzuto, in press). We demonstrate with one-dimensional bed material transport modeling that bed material can move through impoundments and that equilibrium transport (i.e., a balance between supply to and export from the impoundment, with a constant bed elevation) is possible even when the bed elevation is below the top of the dam. Based on our field work and previous HEC-RAS modeling, we assess bed material transport capacity at the base of the sediment ramp (and ignore detailed processes carrying sediment up and ramp and over the dam). The hydraulics at the base of the ramp are computed using a weir equation, providing estimates of water depth, velocity, and friction, based on the discharge and sediment grain size distribution of the impoundment. Bedload transport rates are computed using the Wilcock-Crowe equation, and changes in the impoundment's bed elevation are determined by sediment continuity. Our results indicate that impoundments pass the gravel supplied from upstream with deep pools when gravel supply rate is low, gravel grain sizes are relatively small, sand supply is high, and discharge is high. Conversely, impoundments will tend to fill their pools when gravel supply rate is high, gravel grain sizes are relatively large, sand supply is low, and discharge is low. The rate of bedload supplied to an impoundment is the primary control on how fast equilibrium transport is reached, with discharge having almost no influence on the timing of equilibrium.
NASA Astrophysics Data System (ADS)
Radhakrishnan, Sreeram
Harbor observation and prediction system (NYHOPS) which provides 48-hour forecasts of salinity and temperature profiles. Initial results indicate that the NYHOPS forecast of sound speed profiles used in conjunction with the acoustic propagation model is able to make realistic forecasts of TL in the Hudson River Estuary.
NASA Technical Reports Server (NTRS)
Schonberg, William P.; Peck, Jeffrey A.
1992-01-01
Over the last three decades, multiwall structures have been analyzed extensively, primarily through experiment, as a means of increasing the protection afforded to spacecraft structure. However, as structural configurations become more varied, the number of tests required to characterize their response increases dramatically. As an alternative, numerical modeling of high-speed impact phenomena is often being used to predict the response of a variety of structural systems under impact loading conditions. This paper presents the results of a preliminary numerical/experimental investigation of the hypervelocity impact response of multiwall structures. The results of experimental high-speed impact tests are compared against the predictions of the HULL hydrodynamic computer code. It is shown that the hypervelocity impact response characteristics of a specific system cannot be accurately predicted from a limited number of HULL code impact simulations. However, if a wide range of impact loadings conditions are considered, then the ballistic limit curve of the system based on the entire series of numerical simulations can be used as a relatively accurate indication of actual system response.
Field Testing of a Wet FGD Additive for Enhanced Mercury Control - Task 5 Full-Scale Test Results
Gary Blythe; MariJon Owens
2007-12-01
and reporting. The other four tasks involve field testing on FGD systems, either at pilot or full scale. The four tasks include: Task 2 - Pilot Additive Testing in Texas Lignite Flue Gas; Task 3 - Full-scale FGD Additive Testing in High-sulfur Eastern Bituminous Flue Gas; Task 4 - Pilot Wet Scrubber Additive Tests at Plant Yates; and Task 5 - Full-scale Additive Tests at Plant Yates. The pilot-scale tests and the full-scale test using high-sulfur coal were completed in 2005 and 2006 and have been previously reported. This topical report presents the results from the Task 5 full-scale additive tests, conducted at Southern Company's Plant Yates Unit 1. Both additives were tested there.
Numerical Modeling of Anti-icing Systems and Comparison to Test Results on a NACA 0012 Airfoil
NASA Technical Reports Server (NTRS)
Al-Khalil, Kamel M.; Potapczuk, Mark G.
1993-01-01
A series of experimental tests were conducted in the NASA Lewis IRT on an electro-thermally heated NACA 0012 airfoil. Quantitative comparisons between the experimental results and those predicted by a computer simulation code were made to assess the validity of a recently developed anti-icing model. An infrared camera was utilized to scan the instantaneous temperature contours of the skin surface. Despite some experimental difficulties, good agreement between the numerical predictions and the experiment results were generally obtained for the surface temperature and the possibility for each runback to freeze. Some recommendations were given for an efficient operation of a thermal anti-icing system.
NASA Astrophysics Data System (ADS)
LeBlanc, J. P. F.; Antipov, Andrey E.; Becca, Federico; Bulik, Ireneusz W.; Chan, Garnet Kin-Lic; Chung, Chia-Min; Deng, Youjin; Ferrero, Michel; Henderson, Thomas M.; Jiménez-Hoyos, Carlos A.; Kozik, E.; Liu, Xuan-Wen; Millis, Andrew J.; Prokof'ev, N. V.; Qin, Mingpu; Scuseria, Gustavo E.; Shi, Hao; Svistunov, B. V.; Tocchio, Luca F.; Tupitsyn, I. S.; White, Steven R.; Zhang, Shiwei; Zheng, Bo-Xiao; Zhu, Zhenyue; Gull, Emanuel; Simons Collaboration on the Many-Electron Problem
2015-10-01
Numerical results for ground-state and excited-state properties (energies, double occupancies, and Matsubara-axis self-energies) of the single-orbital Hubbard model on a two-dimensional square lattice are presented, in order to provide an assessment of our ability to compute accurate results in the thermodynamic limit. Many methods are employed, including auxiliary-field quantum Monte Carlo, bare and bold-line diagrammatic Monte Carlo, method of dual fermions, density matrix embedding theory, density matrix renormalization group, dynamical cluster approximation, diffusion Monte Carlo within a fixed-node approximation, unrestricted coupled cluster theory, and multireference projected Hartree-Fock methods. Comparison of results obtained by different methods allows for the identification of uncertainties and systematic errors. The importance of extrapolation to converged thermodynamic-limit values is emphasized. Cases where agreement between different methods is obtained establish benchmark results that may be useful in the validation of new approaches and the improvement of existing methods.
NASA Astrophysics Data System (ADS)
Wu, Yang; Kelly, Damien P.
2014-12-01
The distribution of the complex field in the focal region of a lens is a classical optical diffraction problem. Today, it remains of significant theoretical importance for understanding the properties of imaging systems. In the paraxial regime, it is possible to find analytical solutions in the neighborhood of the focus, when a plane wave is incident on a focusing lens whose finite extent is limited by a circular aperture. For example, in Born and Wolf's treatment of this problem, two different, but mathematically equivalent analytical solutions, are presented that describe the 3D field distribution using infinite sums of ? and ? type Lommel functions. An alternative solution expresses the distribution in terms of Zernike polynomials, and was presented by Nijboer in 1947. More recently, Cao derived an alternative analytical solution by expanding the Fresnel kernel using a Taylor series expansion. In practical calculations, however, only a finite number of terms from these infinite series expansions is actually used to calculate the distribution in the focal region. In this manuscript, we compare and contrast each of these different solutions to a numerically calculated result, paying particular attention to how quickly each solution converges for a range of different spatial locations behind the focusing lens. We also examine the time taken to calculate each of the analytical solutions. The numerical solution is calculated in a polar coordinate system and is semi-analytic. The integration over the angle is solved analytically, while the radial coordinate is sampled with a sampling interval of ? and then numerically integrated. This produces an infinite set of replicas in the diffraction plane, that are located in circular rings centered at the optical axis and each with radii given by ?, where ? is the replica order. These circular replicas are shown to be fundamentally different from the replicas that arise in a Cartesian coordinate system.
Wu, Yang; Kelly, Damien P.
2014-01-01
The distribution of the complex field in the focal region of a lens is a classical optical diffraction problem. Today, it remains of significant theoretical importance for understanding the properties of imaging systems. In the paraxial regime, it is possible to find analytical solutions in the neighborhood of the focus, when a plane wave is incident on a focusing lens whose finite extent is limited by a circular aperture. For example, in Born and Wolf’s treatment of this problem, two different, but mathematically equivalent analytical solutions, are presented that describe the 3D field distribution using infinite sums of Un and Vn type Lommel functions. An alternative solution expresses the distribution in terms of Zernike polynomials, and was presented by Nijboer in 1947. More recently, Cao derived an alternative analytical solution by expanding the Fresnel kernel using a Taylor series expansion. In practical calculations, however, only a finite number of terms from these infinite series expansions is actually used to calculate the distribution in the focal region. In this manuscript, we compare and contrast each of these different solutions to a numerically calculated result, paying particular attention to how quickly each solution converges for a range of different spatial locations behind the focusing lens. We also examine the time taken to calculate each of the analytical solutions. The numerical solution is calculated in a polar coordinate system and is semi-analytic. The integration over the angle is solved analytically, while the radial coordinate is sampled with a sampling interval of Δρ and then numerically integrated. This produces an infinite set of replicas in the diffraction plane, that are located in circular rings centered at the optical axis and each with radii given by 2πm/Δρ, where m is the replica order. These circular replicas are shown to be fundamentally different from the replicas that arise in a Cartesian coordinate system. PMID
NASA Astrophysics Data System (ADS)
Baharun, A. Tarmizi; Maimun, Adi; Ahmed, Yasser M.; Mobassher, M.; Nakisa, M.
2015-05-01
In this paper, three dimensional data and behavior of incompressible and steady air flow around a small scale Wing in Ground Effect Craft (WIG) were investigated and studied numerically then compared to the experimental result and also published data. This computational simulation (CFD) adopted two turbulence models, which were k-ɛ and k-ω in order to determine which model produces minimum difference to the experimental result of the small scale WIG tested in wind tunnel. Unstructured mesh was used in the simulation and data of drag coefficient (Cd) and lift coefficient (Cl) were obtained with angle of attack (AoA) of the WIG model as the parameter. Ansys ICEM was used for the meshing process while Ansys Fluent was used for solution. Aerodynamic forces, Cl, Cd and Cl/Cd along with fluid flow pattern of the small scale WIG craft was shown and discussed.
Meyer, H. O.
The PINTEX group studied proton-proton and proton-deuteron scattering and reactions between 100 and 500 MeV at the Indiana University Cyclotron Facility (IUCF). More than a dozen experiments made use of electron-cooled polarized proton or deuteron beams, orbiting in the 'Indiana Cooler' storage ring, and of a polarized atomic-beam target of hydrogen or deuterium in the path of the stored beam. The collaboration involved researchers from several midwestern universities, as well as a number of European institutions. The PINTEX program ended when the Indiana Cooler was shut down in August 2002. The website contains links to some of the numerical results, descriptions of experiments, and a complete list of publications resulting from PINTEX.
NASA Astrophysics Data System (ADS)
Fontana, A.; Marzari, F.
2016-05-01
Context. Planetesimals and planets embedded in a circumstellar disk are dynamically perturbed by the disk gravity. It causes an apsidal line precession at a rate that depends on the disk density profile and on the distance of the massive body from the star. Aims: Different analytical models are exploited to compute the precession rate of the perihelion ϖ˙. We compare them to verify their equivalence, in particular after analytical manipulations performed to derive handy formulas, and test their predictions against numerical models in some selected cases. Methods: The theoretical precession rates were computed with analytical algorithms found in the literature using the Mathematica symbolic code, while the numerical simulations were performed with the hydrodynamical code FARGO. Results: For low-mass bodies (planetesimals) the analytical approaches described in Binney & Tremaine (2008, Galactic Dynamics, p. 96), Ward (1981, Icarus, 47, 234), and Silsbee & Rafikov (2015a, ApJ, 798, 71) are equivalent under the same initial conditions for the disk in terms of mass, density profile, and inner and outer borders. They also match the numerical values computed with FARGO away from the outer border of the disk reasonably well. On the other hand, the predictions of the classical Mestel disk (Mestel 1963, MNRAS, 126, 553) for disks with p = 1 significantly depart from the numerical solution for radial distances beyond one-third of the disk extension because of the underlying assumption of the Mestel disk is that the outer disk border is equal to infinity. For massive bodies such as terrestrial and giant planets, the agreement of the analytical approaches is progressively poorer because of the changes in the disk structure that are induced by the planet gravity. For giant planets the precession rate changes sign and is higher than the modulus of the theoretical value by a factor ranging from 1.5 to 1.8. In this case, the correction of the formula proposed by Ward (1981) to
Siddique, Waseem; El-Gabry, Lamyaa; Shevchuk, Igor V; Fransson, Torsten H
2013-01-01
High inlet temperatures in a gas turbine lead to an increase in the thermal efficiency of the gas turbine. This results in the requirement of cooling of gas turbine blades/vanes. Internal cooling of the gas turbine blade/vanes with the help of two-pass channels is one of the effective methods to reduce the metal temperatures. In particular, the trailing edge of a turbine vane is a critical area, where effective cooling is required. The trailing edge can be modeled as a trapezoidal channel. This paper describes the numerical validation of the heat transfer and pressure drop in a trapezoidal channel with and without orthogonal ribs at the bottom surface. A new concept of ribbed trailing edge has been introduced in this paper which presents a numerical study of several trailing edge cooling configurations based on the placement of ribs at different walls. The baseline geometries are two-pass trapezoidal channels with and without orthogonal ribs at the bottom surface of the channel. Ribs induce secondary flow which results in enhancement of heat transfer; therefore, for enhancement of heat transfer at the trailing edge, ribs are placed at the trailing edge surface in three different configurations: first without ribs at the bottom surface, then ribs at the trailing edge surface in-line with the ribs at the bottom surface, and finally staggered ribs. Heat transfer and pressure drop is calculated at Reynolds number equal to 9400 for all configurations. Different turbulent models are used for the validation of the numerical results. For the smooth channel low-Re k-ɛ model, realizable k-ɛ model, the RNG k-ω model, low-Re k-ω model, and SST k-ω models are compared, whereas for ribbed channel, low-Re k-ɛ model and SST k-ω models are compared. The results show that the low-Re k-ɛ model, which predicts the heat transfer in outlet pass of the smooth channels with difference of +7%, underpredicts the heat transfer by -17% in case of ribbed channel compared to
NASA Astrophysics Data System (ADS)
Sanz-Enguita, G.; Ortega, J.; Folcia, C. L.; Aramburu, I.; Etxebarria, J.
2016-02-01
We have studied the performance characteristics of a dye-doped cholesteric liquid crystal (CLC) laser as a function of the sample thickness. The study has been carried out both from the experimental and theoretical points of view. The theoretical model is based on the kinetic equations for the population of the excited states of the dye and for the power of light generated within the laser cavity. From the equations, the threshold pump radiation energy Eth and the slope efficiency η are numerically calculated. Eth is rather insensitive to thickness changes, except for small thicknesses. In comparison, η shows a much more pronounced variation, exhibiting a maximum that determines the sample thickness for optimum laser performance. The predictions are in good accordance with the experimental results. Approximate analytical expressions for Eth and η as a function of the physical characteristics of the CLC laser are also proposed. These expressions present an excellent agreement with the numerical calculations. Finally, we comment on the general features of CLC layer and dye that lead to the best laser performance.
Tarr, James C.
2010-01-01
We report the full account of our efforts on the lanthanum tricyanide-catalyzed acyl silane-ketone benzoin reaction. The reaction exhibits a wide scope in both acyl silane (aryl, alkyl) and ketone (aryl-alkyl, alkyl-alkyl, aryl-aryl, alkenyl-alkyl, alkynyl-alkyl) coupling partners. The diastereoselectivity of the reaction has been examined in both cyclic and acyclic systems. Cyclohexanones give products arising from equatorial attack by the acyl silane. The diastereoselectivity of acyl silane addition to acyclic α-hydroxy ketones can be controlled by varying the protecting group to obtain either Felkin-Ahn or chelation control. The resultant α-silyloxyketone products can be resolved with selectivity factors from 10 to 15 by subjecting racemic ketone benzoin products to CBS reduction. PMID:20392127
Marini, Cecilia; Bianchi, Giovanna; Buschiazzo, Ambra; Ravera, Silvia; Martella, Roberto; Bottoni, Gianluca; Petretto, Andrea; Emionite, Laura; Monteverde, Elena; Capitanio, Selene; Inglese, Elvira; Fabbi, Marina; Bongioanni, Francesca; Garaboldi, Lucia; Bruzzi, Paolo; Orengo, Anna Maria; Raffaghello, Lizzia; Sambuceti, Gianmario
2016-01-01
Emerging evidence demonstrates that targeting energy metabolism is a promising strategy to fight cancer. Here we show that combining metformin and short-term starvation markedly impairs metabolism and growth of colon and breast cancer. The impairment in glycolytic flux caused by starvation is enhanced by metformin through its interference with hexokinase II activity, as documented by measurement of 18F-fluorodeoxyglycose uptake. Oxidative phosphorylation is additively compromised by combined treatment: metformin virtually abolishes Complex I function; starvation determines an uncoupled status of OXPHOS and amplifies the activity of respiratory Complexes II and IV thus combining a massive ATP depletion with a significant increase in reactive oxygen species. More importantly, the combined treatment profoundly impairs cancer glucose metabolism and virtually abolishes lesion growth in experimental models of breast and colon carcinoma. Our results strongly suggest that energy metabolism is a promising target to reduce cancer progression. PMID:26794854
Marini, Cecilia; Bianchi, Giovanna; Buschiazzo, Ambra; Ravera, Silvia; Martella, Roberto; Bottoni, Gianluca; Petretto, Andrea; Emionite, Laura; Monteverde, Elena; Capitanio, Selene; Inglese, Elvira; Fabbi, Marina; Bongioanni, Francesca; Garaboldi, Lucia; Bruzzi, Paolo; Orengo, Anna Maria; Raffaghello, Lizzia; Sambuceti, Gianmario
2016-01-01
Emerging evidence demonstrates that targeting energy metabolism is a promising strategy to fight cancer. Here we show that combining metformin and short-term starvation markedly impairs metabolism and growth of colon and breast cancer. The impairment in glycolytic flux caused by starvation is enhanced by metformin through its interference with hexokinase II activity, as documented by measurement of 18F-fluorodeoxyglycose uptake. Oxidative phosphorylation is additively compromised by combined treatment: metformin virtually abolishes Complex I function; starvation determines an uncoupled status of OXPHOS and amplifies the activity of respiratory Complexes II and IV thus combining a massive ATP depletion with a significant increase in reactive oxygen species. More importantly, the combined treatment profoundly impairs cancer glucose metabolism and virtually abolishes lesion growth in experimental models of breast and colon carcinoma. Our results strongly suggest that energy metabolism is a promising target to reduce cancer progression. PMID:26794854
NASA Astrophysics Data System (ADS)
de'Michieli Vitturi, M.; Todesco, M.; Neri, A.; Esposti Ongaro, T.; Tola, E.; Rocco, G.
2011-12-01
We present a new DVD of the INGV outreach series, aimed at illustrating our research work on pyroclastic flow modeling. Pyroclastic flows (or pyroclastic density currents) are hot, devastating clouds of gas and ashes, generated during explosive eruptions. Understanding their dynamics and impact is crucial for a proper hazard assessment. We employ a 3D numerical model which describes the main features of the multi-phase and multi-component process, from the generation of the flows to their propagation along complex terrains. Our numerical results can be translated into color animations, which describe the temporal evolution of flow variables such as temperature or ash concentration. The animations provide a detailed and effective description of the natural phenomenon which can be used to present this geological process to a general public and to improve the hazard perception in volcanic areas. In our DVD, the computer animations are introduced and commented by professionals and researchers who deals at various levels with the study of pyroclastic flows and their impact. Their comments are taken as short interviews, mounted in a short video (about 10 minutes), which describes the natural process, as well as the model and its applications to some explosive volcanoes like Vesuvio, Campi Flegrei, Mt. St. Helens and Soufriere Hills (Montserrat). The ensemble of different voices and faces provides a direct sense of the multi-disciplinary effort involved in the assessment of pyroclastic flow hazard. The video also introduces the people who address this complex problem, and the personal involvement beyond the scientific results. The full, uncommented animations of the pyroclastic flow propagation on the different volcanic settings are also provided in the DVD, that is meant to be a general, flexible outreach tool.
Bondar, Yu I; Navumau, A D; Nikitin, A N; Brown, J; Dowdall, M
2014-12-01
Forest fires and wild fires are recognized as a possible cause of resuspension and redistribution of radioactive substances when occurring on lands contaminated with such materials, and as such are a matter of concern within the regions of Belarus and the Ukraine which were contaminated by the Chernobyl accident in 1986. Modelling the effects of such fires on radioactive contaminants is a complex matter given the number of variables involved. In this paper, a probabilistic model was developed using empirical data drawn from the Polessie State Radiation-Ecological Reserve (PSRER), Belarus, and the Maximum Entropy Method. Using the model, it was possible to derive estimates of the contribution of fire events to overall variability in the levels of (137)Cs and (239,240)Pu in ground air as well as estimates of the deposition of these radionuclides to specific water bodies within the contaminated areas of Belarus. Results indicate that fire events are potentially significant redistributors of radioactive contaminants within the study area and may result in additional contamination being introduced to water bodies. PMID:25240987
Banerjee, Antara; Chakrabarty, Sudipa Basu; Karmakar, Susanta Roy; Chakrabarty, Amit; Biswas, Surjyo Jyoti; Haque, Saiful; Das, Debarsi; Paul, Saili; Mandal, Biswapati; Naoual, Boujedaini; Belon, Philippe; Khuda-Bukhsh, Anisur Rahman
2010-03-01
Several homeopathic remedies, namely, Pulsatilla Nigricans (30th potency), Ceanothus Americanus (both mother tincture and 6th potency) and Ferrum Metallicum (30th potency) selected as per similia principles were administered to 38 thalassemic patients receiving Hydroxyurea (HU) therapy for a varying period of time. Levels of serum ferritin (SF), fetal hemoglobin (HbF), hemoglobin (Hb), platelet count (PC), mean corpuscular volume (MCV), mean corpuscular hemoglobin concentration (MCHC), mean corpuscular hemoglobin (MCH), white blood cell (WBC) count, bilirubin content, alanine amino transferase (ALT), aspartate amino transferase (AST) and serum total protein content of patients were determined before and 3 months after administration of the homeopathic remedies in combination with HU to evaluate additional benefits, if any, derived by the homeopathic remedies, by comparing the data with those of 38 subjects receiving only HU therapy. Preliminary results indicated that there was a significant decrease in the SF and increase in HbF levels in the combined, treated subjects. Although the changes in other parameters were not so significant, there was a significant decrease in size of spleen in most patients with spleenomegaly and improvement in general health conditions along with an increased gap between transfusions in most patients receiving the combined homeopathic treatment. The homeopathic remedies being inexpensive and without any known side-effects seem to have great potentials in bringing additional benefits to thalassemic patients; particularly in the developing world where blood transfusions suffer from inadequate screening and fall short of the stringent safety standards followed in the developed countries. Further independent studies are encouraged. PMID:18955271
LeBlanc, J. P. F.; Antipov, Andrey E.; Becca, Federico; Bulik, Ireneusz W.; Chan, Garnet Kin-Lic; Chung, Chia -Min; Deng, Youjin; Ferrero, Michel; Henderson, Thomas M.; Jiménez-Hoyos, Carlos A.; et al
2015-12-14
Numerical results for ground-state and excited-state properties (energies, double occupancies, and Matsubara-axis self-energies) of the single-orbital Hubbard model on a two-dimensional square lattice are presented, in order to provide an assessment of our ability to compute accurate results in the thermodynamic limit. Many methods are employed, including auxiliary-field quantum Monte Carlo, bare and bold-line diagrammatic Monte Carlo, method of dual fermions, density matrix embedding theory, density matrix renormalization group, dynamical cluster approximation, diffusion Monte Carlo within a fixed-node approximation, unrestricted coupled cluster theory, and multireference projected Hartree-Fock methods. Comparison of results obtained by different methods allows for the identification ofmore » uncertainties and systematic errors. The importance of extrapolation to converged thermodynamic-limit values is emphasized. Furthermore, cases where agreement between different methods is obtained establish benchmark results that may be useful in the validation of new approaches and the improvement of existing methods.« less
G. L. Hawkes; J. E. O'Brien; B. A. Haberman; A. J. Marquis; C. M. Baca; D. Tripepi; P. Costamagna
2008-06-01
A numerical study of the thermal and electrochemical performance of a single-tube Integrated Planar Solid Oxide Fuel Cell (IP-SOFC) has been performed. Results obtained from two finite-volume computational fluid dynamics (CFD) codes FLUENT and SOHAB and from a two-dimensional inhouse developed finite-volume GENOA model are presented and compared. Each tool uses physical and geometric models of differing complexity and comparisons are made to assess their relative merits. Several single-tube simulations were run using each code over a range of operating conditions. The results include polarization curves, distributions of local current density, composition and temperature. Comparisons of these results are discussed, along with their relationship to the respective imbedded phenomenological models for activation losses, fluid flow and mass transport in porous media. In general, agreement between the codes was within 15% for overall parameters such as operating voltage and maximum temperature. The CFD results clearly show the effects of internal structure on the distributions of gas flows and related quantities within the electrochemical cells.
LeBlanc, J. P. F.; Antipov, Andrey E.; Becca, Federico; Bulik, Ireneusz W.; Chan, Garnet Kin-Lic; Chung, Chia -Min; Deng, Youjin; Ferrero, Michel; Henderson, Thomas M.; Jiménez-Hoyos, Carlos A.; Kozik, E.; Liu, Xuan -Wen; Millis, Andrew J.; Prokof’ev, N. V.; Qin, Mingpu; Scuseria, Gustavo E.; Shi, Hao; Svistunov, B. V.; Tocchio, Luca F.; Tupitsyn, I. S.; White, Steven R.; Zhang, Shiwei; Zheng, Bo -Xiao; Zhu, Zhenyue; Gull, Emanuel
2015-12-14
Numerical results for ground-state and excited-state properties (energies, double occupancies, and Matsubara-axis self-energies) of the single-orbital Hubbard model on a two-dimensional square lattice are presented, in order to provide an assessment of our ability to compute accurate results in the thermodynamic limit. Many methods are employed, including auxiliary-field quantum Monte Carlo, bare and bold-line diagrammatic Monte Carlo, method of dual fermions, density matrix embedding theory, density matrix renormalization group, dynamical cluster approximation, diffusion Monte Carlo within a fixed-node approximation, unrestricted coupled cluster theory, and multireference projected Hartree-Fock methods. Comparison of results obtained by different methods allows for the identification of uncertainties and systematic errors. The importance of extrapolation to converged thermodynamic-limit values is emphasized. Furthermore, cases where agreement between different methods is obtained establish benchmark results that may be useful in the validation of new approaches and the improvement of existing methods.
NASA Astrophysics Data System (ADS)
Hand, J. W.; Li, Y.; Hajnal, J. V.
2010-02-01
Numerical simulations of specific absorption rate (SAR) and temperature changes in a 26-week pregnant woman model within typical birdcage body coils as used in 1.5 T and 3 T MRI scanners are described. Spatial distributions of SAR and the resulting spatial and temporal changes in temperature are determined using a finite difference time domain method and a finite difference bio-heat transfer solver that accounts for discrete vessels. Heat transfer from foetus to placenta via the umbilical vein and arteries as well as that across the foetal skin/amniotic fluid/uterine wall boundaries is modelled. Results suggest that for procedures compliant with IEC normal mode conditions (maternal whole-body averaged SARMWB <= 2 W kg-1 (continuous or time-averaged over 6 min)), whole foetal SAR, local foetal SAR10g and average foetal temperature are within international safety limits. For continuous RF exposure at SARMWB = 2 W kg-1 over periods of 7.5 min or longer, a maximum local foetal temperature >38 °C may occur. However, assessment of the risk posed by such maximum temperatures predicted in a static model is difficult because of frequent foetal movement. Results also confirm that when SARMWB = 2 W kg-1, some local SAR10g values in the mother's trunk and extremities exceed recommended limits.
Ermolaev, B.S.; Novozhilov, B.V.; Posvyanskii, V.S.; Sulimov, A.A.
1986-03-01
The authors analyze the results of a numerical simulation of the convective burning of explosive powders in the presence of increasing pressure. The formulation of the problem reproduces a typical experimental technique: a strong closed vessel with a channel uniformly filled with the explosive investigated is fitted with devices for initiating and recording the process of explosion. It is shown that the relation between the propagation velocities of the flame and the compression waves in the powder and the rate of pressure increase in the combustion zone is such that a narrow compaction zone is formed ahead of the ignition front. Another important result is obtained by analyzing the difference between the flame velocity and the gas flow velocity in the ignition front. A model of the process is given. The results of the investigation throw light on such aspects of the convective combustion mechanism and the transition from combustion to detonation as the role of compaction of the explosive in the process of flame propogation and the role of the rate of pressure increase and dissipative heating of the gas phase in the pores ahead of the ignition front.
NASA Astrophysics Data System (ADS)
Wang, Y.; Qin, G.; Zhang, M.
2012-12-01
Solar energetic particle (SEP) fluxes data measured by multi-spacecraft are able to provide important information of the transport process of SEPs accelerated by the interplanetary coronal mass ejection (ICME) shock. Depending on their locations, observers in interplanetary space may be connected to different parts of an ICME shock by the interplanetary magnetic field (IMF). Simultaneous observations by multi-spacecraft in the ecliptic, e.g., ACE, STEREO A and B, usually show huge differences of SEP time profiles. In this work, based on a numerical solution of the Fokker-Planck transport equation for energetic particles, we will obtain the fluxes of SEPs accelerated by ICME shocks. In addition, we will compare SEP events measured by these spacecraft, located at different longitudes, with our simulation results. The comparison has enabled us to determine the parameters of particle transport such as the parallel and perpendicular diffusion coefficients and the efficiency of particles injections at the ICME shock.
NASA Technical Reports Server (NTRS)
Witte, Jacquelyn C.; Thompson, Anne M.; Schmidlin, F. J.; Oltmans, S. J.; Smit, H. G. J.
2004-01-01
Since 1998 the Southern Hemisphere ADditional OZonesondes (SHADOZ) project has provided over 2000 ozone profiles over eleven southern hemisphere tropical and subtropical stations. Balloon-borne electrochemical concentration cell (ECC) ozonesondes are used to measure ozone. The data are archived at: &ttp://croc.gsfc.nasa.gov/shadoz>. In analysis of ozonesonde imprecision within the SHADOZ dataset, Thompson et al. [JGR, 108,8238,20031 we pointed out that variations in ozonesonde technique (sensor solution strength, instrument manufacturer, data processing) could lead to station-to-station biases within the SHADOZ dataset. Imprecisions and accuracy in the SHADOZ dataset are examined in light of new data. First, SHADOZ total ozone column amounts are compared to version 8 TOMS (2004 release). As for TOMS version 7, satellite total ozone is usually higher than the integrated column amount from the sounding. Discrepancies between the sonde and satellite datasets decline two percentage points on average, compared to version 7 TOMS offsets. Second, the SHADOZ station data are compared to results of chamber simulations (JOSE-2000, Juelich Ozonesonde Intercomparison Experiment) in which the various SHADOZ techniques were evaluated. The range of JOSE column deviations from a standard instrument (-10%) in the chamber resembles that of the SHADOZ station data. It appears that some systematic variations in the SHADOZ ozone record are accounted for by differences in solution strength, data processing and instrument type (manufacturer).
NASA Technical Reports Server (NTRS)
Peltier, L. J.; Biringen, S.
1993-01-01
The present numerical simulation explores a thermal-convective mechanism for oscillatory thermocapillary convection in a shallow Cartesian cavity for a Prandtl number 6.78 fluid. The computer program developed for this simulation integrates the two-dimensional, time-dependent Navier-Stokes equations and the energy equation by a time-accurate method on a stretched, staggered mesh. Flat free surfaces are assumed. The instability is shown to depend upon temporal coupling between large scale thermal structures within the flow field and the temperature sensitive free surface. A primary result of this study is the development of a stability diagram presenting the critical Marangoni number separating steady from the time-dependent flow states as a function of aspect ratio for the range of values between 2.3 and 3.8. Within this range, a minimum critical aspect ratio near 2.3 and a minimum critical Marangoni number near 20,000 are predicted below which steady convection is found.
Dvir, Hila; Zlochiver, Sharon
2015-01-01
A single isolated sinoatrial pacemaker cell presents intrinsic interbeat interval (IBI) variability that is believed to result from the stochastic characteristics of the opening and closing processes of membrane ion channels. To our knowledge, a novel mathematical framework was developed in this work to address the effect of current fluctuations on the IBIs of sinoatrial pacemaker cells. Using statistical modeling and employing the Fokker-Planck formalism, our mathematical analysis suggests that increased stochastic current fluctuation variance linearly increases the slope of phase-4 depolarization, hence the rate of activations. Single-cell and two-dimensional computerized numerical modeling of the sinoatrial node was conducted to validate the theoretical predictions using established ionic kinetics of the rabbit pacemaker and atrial cells. Our models also provide, to our knowledge, a novel complementary or alternative explanation to recent experimental observations showing a strong reduction in the mean IBI of Cx30 deficient mice in comparison to wild-types, not fully explicable by the effects of intercellular decoupling. PMID:25762340
2010-01-01
Background The mitosporic fungus Trichoderma harzianum (Hypocrea, Ascomycota, Hypocreales, Hypocreaceae) is an ubiquitous species in the environment with some strains commercially exploited for the biological control of plant pathogenic fungi. Although T. harzianum is asexual (or anamorphic), its sexual stage (or teleomorph) has been described as Hypocrea lixii. Since recombination would be an important issue for the efficacy of an agent of the biological control in the field, we investigated the phylogenetic structure of the species. Results Using DNA sequence data from three unlinked loci for each of 93 strains collected worldwide, we detected a complex speciation process revealing overlapping reproductively isolated biological species, recent agamospecies and numerous relict lineages with unresolved phylogenetic positions. Genealogical concordance and recombination analyses confirm the existence of two genetically isolated agamospecies including T. harzianum sensu stricto and two hypothetical holomorphic species related to but different from H. lixii. The exact phylogenetic position of the majority of strains was not resolved and therefore attributed to a diverse network of recombining strains conventionally called 'pseudoharzianum matrix'. Since H. lixii and T. harzianum are evidently genetically isolated, the anamorph - teleomorph combination comprising H. lixii/T. harzianum in one holomorph must be rejected in favor of two separate species. Conclusions Our data illustrate a complex speciation within H. lixii - T. harzianum species group, which is based on coexistence and interaction of organisms with different evolutionary histories and on the absence of strict genetic borders between them. PMID:20359347
NASA Astrophysics Data System (ADS)
Chirkov, V. A.; Komarov, D. K.; Stishkov, Y. K.; Vasilkov, S. A.
2015-10-01
The paper studies a particular electrode system, two flat parallel electrodes with a dielectric plate having a small circular hole between them. Its main feature is that the region of the strong electric field is located far from metal electrode surfaces, which permits one to preclude the injection charge formation and to observe field-enhanced dissociation (the Wien effect) leading to the emergence of electrohydrodynamic (EHD) flow. The described electrode system was studied by way of both computer simulation and experiment. The latter was conducted with the help of the particle image velocimetry (or PIV) technique. The numerical research used trusted software package COMSOL Multiphysics, which allows solving the complete set of EHD equations and obtaining the EHD flow structure. Basing on the computer simulation and the comparison with experimental investigation results, it was concluded that the Wien effect is capable of causing intense (several centimeters per second) EHD flows in low-conducting liquids and has to be taken into account when dealing with EHD devices.
Luo Xueli; Day, Christian; Haas, Horst; Varoutis, Stylianos
2011-07-15
For the torus of the nuclear fusion project ITER (originally the International Thermonuclear Experimental Reactor, but also Latin: the way), eight high-performance large-scale customized cryopumps must be designed and manufactured to accommodate the very high pumping speeds and throughputs of the fusion exhaust gas needed to maintain the plasma under stable vacuum conditions and comply with other criteria which cannot be met by standard commercial vacuum pumps. Under an earlier research and development program, a model pump of reduced scale based on active cryosorption on charcoal-coated panels at 4.5 K was manufactured and tested systematically. The present article focuses on the simulation of the true three-dimensional complex geometry of the model pump by the newly developed ProVac3D Monte Carlo code. It is shown for gas throughputs of up to 1000 sccm ({approx}1.69 Pa m{sup 3}/s at T = 0 deg. C) in the free molecular regime that the numerical simulation results are in good agreement with the pumping speeds measured. Meanwhile, the capture coefficient associated with the virtual region around the cryogenic panels and shields which holds for higher throughputs is calculated using this generic approach. This means that the test particle Monte Carlo simulations in free molecular flow can be used not only for the optimization of the pumping system but also for the supply of the input parameters necessary for the future direct simulation Monte Carlo in the full flow regime.
Dvir, Hila; Zlochiver, Sharon
2015-03-10
A single isolated sinoatrial pacemaker cell presents intrinsic interbeat interval (IBI) variability that is believed to result from the stochastic characteristics of the opening and closing processes of membrane ion channels. To our knowledge, a novel mathematical framework was developed in this work to address the effect of current fluctuations on the IBIs of sinoatrial pacemaker cells. Using statistical modeling and employing the Fokker-Planck formalism, our mathematical analysis suggests that increased stochastic current fluctuation variance linearly increases the slope of phase-4 depolarization, hence the rate of activations. Single-cell and two-dimensional computerized numerical modeling of the sinoatrial node was conducted to validate the theoretical predictions using established ionic kinetics of the rabbit pacemaker and atrial cells. Our models also provide, to our knowledge, a novel complementary or alternative explanation to recent experimental observations showing a strong reduction in the mean IBI of Cx30 deficient mice in comparison to wild-types, not fully explicable by the effects of intercellular decoupling. PMID:25762340
2013-01-01
Numerous rheological and microvascular alterations characterize the vascular pathology in patients with type 2 diabetes mellitus (T2DM). This study investigated effects of vildagliptin in comparison to glimepiride on retinal microvascular blood flow and erythrocyte deformability in T2DM. Fourty-four patients with T2DM on metformin monotherapy were included in this randomized, exploratory study over 24 weeks. Patients were randomized to receive either vildagliptin (50 mg twice daily) or glimepiride individually titrated up to 4 mg in addition to ongoing metformin treatment. Retinal microvascular blood flow (RBF) and the arteriolar wall to lumen ratio (WLR) were assessed using a laser doppler scanner. In addition, the erythrocyte elongation index (EI) was measured at different shear stresses using laserdiffractoscopy. Both treatments improved glycaemic control (p < 0.05 vs. baseline; respectively). While only slight changes in RBF and the WLR could be observed during treatment with glimepiride, vildagliptin significantly increased retinal blood flow and decreased the arterial WLR (p < 0.05 vs. baseline respectively). The EI increased during both treatments over a wide range of applied shear stresses (p < 0.05 vs. baseline). An inverse correlation could be observed between improved glycaemic control (HbA1c) and EI (r = −0.524; p < 0.0001) but not with the changes in retinal microvascular measurements. Our results suggest that vildagliptin might exert beneficial effects on retinal microvascular blood flow beyond glucose control. In contrast, the improvement in erythrocyte deformability observed in both treatment groups, seems to be a correlate of improved glycaemic control. PMID:23565740
NASA Astrophysics Data System (ADS)
Valla, Pierre G.; van der Beek, Peter A.; Lague, Dimitri; Carcaillet, Julien
2010-05-01
Bedrock gorges are frequent features in glacial or post-glacial landscapes and allow measurements of fluvial bedrock incision in mountainous relief. Using digital elevation models, aerial photographs, topographic maps and field reconnaissance in the Pelvoux-Ecrins Massif (French Western Alps), we have identified ~30 tributary hanging valleys incised by gorges toward their confluence with the trunk streams. Longitudinal profiles of these tributaries are all convex and have abrupt knickpoints at the upper limit of oversteepened gorge reaches. From morphometric analyses, we find that mean channel gradients and widths, as well as knickpoint retreat rates, display a drainage-area dependence modulated by bedrock lithology. However, there appears to be no relation between horizontal retreat and vertical downwearing of knickpoints. Numerical modeling has been performed to test the capacity of different fluvial incision models to predict the inferred evolution of the gorges. Results from simple end-member models suggest transport-limited behavior of the bedrock gorges. Using a more sophisticated model including dynamic width adjustment and sediment-dependent incision rates, we show that bedrock gorge evolution requires significant supply of sediment from the gorge sidewalls triggered by gorge deepening, combined with pronounced inhibition of bedrock incision by sediment transport and deposition. We then use in-situ produced 10Be cosmogenic nuclides to date and quantify bedrock gorge incision into a single glacial hanging valley (Gorge du Diable). We have sampled gorge sidewalls and the active channel bed to derive both long-term and present-day incision rates. 10Be ages of sidewall profiles reveal rapid incision through the late Holocene (ca 5 ka), implying either delayed initiation of gorge incision after final ice retreat from internal Alpine valleys at ca 12 ka, or post-glacial surface reburial of the gorge. Both modeling results and cosmogenic dating suggest that
Elcner, Jakub; Lizal, Frantisek; Jedelsky, Jan; Jicha, Miroslav; Chovancova, Michaela
2016-04-01
In this article, the results of numerical simulations using computational fluid dynamics (CFD) and a comparison with experiments performed with phase Doppler anemometry are presented. The simulations and experiments were conducted in a realistic model of the human airways, which comprised the throat, trachea and tracheobronchial tree up to the fourth generation. A full inspiration/expiration breathing cycle was used with tidal volumes 0.5 and 1 L, which correspond to a sedentary regime and deep breath, respectively. The length of the entire breathing cycle was 4 s, with inspiration and expiration each lasting 2 s. As a boundary condition for the CFD simulations, experimentally obtained flow rate distribution in 10 terminal airways was used with zero pressure resistance at the throat inlet. CCM+ CFD code (Adapco) was used with an SST k-[Formula: see text] low-Reynolds Number RANS model. The total number of polyhedral control volumes was 2.6 million with a time step of 0.001 s. Comparisons were made at several points in eight cross sections selected according to experiments in the trachea and the left and right bronchi. The results agree well with experiments involving the oscillation (temporal relocation) of flow structures in the majority of the cross sections and individual local positions. Velocity field simulation in several cross sections shows a very unstable flow field, which originates in the tracheal laryngeal jet and propagates far downstream with the formation of separation zones in both left and right airways. The RANS simulation agrees with the experiments in almost all the cross sections and shows unstable local flow structures and a quantitatively acceptable solution for the time-averaged flow field. PMID:26163996
NASA Astrophysics Data System (ADS)
Alekhnovich, Alexander N.; Artemjeva, Natalja V.; Bogomolov, Vladimir V.; Shchelokov, Vyacheslav I.; Petukhov, Vasilij G.
Ranging of coals according to the slagging properties of similar type and investigated coals could be made on the basis of the available reference data. However, to define the slagging and fouling properties of a random coal it is necessary to carry out additional laboratory research.
Ingram, L O
1977-01-01
Cells of Escherichia coli contain an altered fatty acid and phospholipid composition when grown in the presence of sublethal concentrations of a variety of organic solvents and food additives. The diversity of compounds examined which caused these changes indicates that no single catabolic pathway is involved. Many of the observed changes are consistent with the hypothesis that cells adapt their membrane lipids to compensate for the presence of these compounds in the environment. Both sodium benzoate and calcium propionate caused the synthesis of unusual fatty acids. PMID:327934
NASA Astrophysics Data System (ADS)
Takahashi, N.; Okei, K.; Nakatsuka, T.
Accuracies of numerical Fourier and Hankel transforms are examined with the Takahasi-Mori theory of error evaluation. The higher Moliere terms both for spatial and projected distributions derived by these methods agree very well with those derived analytically. The methods will be valuable to solve other transport problems concerning fast charged particles.
NASA Astrophysics Data System (ADS)
Declair, Stefan; Stephan, Klaus; Potthast, Roland
2015-04-01
Determining the amount of weather dependent renewable energy is a demanding task for transmission system operators (TSOs). In the project EWeLiNE funded by the German government, the German Weather Service and the Fraunhofer Institute on Wind Energy and Energy System Technology strongly support the TSOs by developing innovative weather- and power forecasting models and tools for grid integration of weather dependent renewable energy. The key in the energy prediction process chain is the numerical weather prediction (NWP) system. With focus on wind energy, we face the model errors in the planetary boundary layer, which is characterized by strong spatial and temporal fluctuations in wind speed, to improve the basis of the weather dependent renewable energy prediction. Model data can be corrected by postprocessing techniques such as model output statistics and calibration using historical observational data. On the other hand, latest observations can be used in a preprocessing technique called data assimilation (DA). In DA, the model output from a previous time step is combined such with observational data, that the new model data for model integration initialization (analysis) fits best to the latest model data and the observational data as well. Therefore, model errors can be already reduced before the model integration. In this contribution, the results of an impact study are presented. A so-called OSSE (Observation Simulation System Experiment) is performed using the convective-resoluted COSMO-DE model of the German Weather Service and a 4D-DA technique, a Newtonian relaxation method also called nudging. Starting from a nature run (treated as the truth), conventional observations and artificial wind observations at hub height are generated. In a control run, the basic model setup of the nature run is slightly perturbed to drag the model away from the beforehand generated truth and a free forecast is computed based on the analysis using only conventional
Hillhouse, J.W.; Ndombi, J.W.M.; Cox, A.; Brock, A.
1977-01-01
The magnetostratigraphy of the hominid-bearing sediments exposed east of Lake Turkana has been strengthened by new palaeomagnetic results. Ages obtained from several tuffs by the 40Ar/39Ar method suggest an approxmate match between the observed magnetozones and the geomagnetic polarity time scale; however, the palaeomagnetic results are also compatible with a younger chronology suggested by conventional K-Ar dating of the KBS Tuff. ?? 1977 Nature Publishing Group.
NASA Astrophysics Data System (ADS)
van Aalsburg, Jordan; Rundle, John B.; Grant, Lisa B.; Rundle, Paul B.; Yakovlev, Gleb; Turcotte, Donald L.; Donnellan, Andrea; Tiampo, Kristy F.; Fernandez, Jose
2010-08-01
In weather forecasting, current and past observational data are routinely assimilated into numerical simulations to produce ensemble forecasts of future events in a process termed "model steering". Here we describe a similar approach that is motivated by analyses of previous forecasts of the Working Group on California Earthquake Probabilities (WGCEP). Our approach is adapted to the problem of earthquake forecasting using topologically realistic numerical simulations for the strike-slip fault system in California. By systematically comparing simulation data to observed paleoseismic data, a series of spatial probability density functions (PDFs) can be computed that describe the probable locations of future large earthquakes. We develop this approach and show examples of PDFs associated with magnitude M > 6.5 and M > 7.0 earthquakes in California.
Sato, Kyoko; Suzuki, Ippei; Kubota, Hiroki; Furusho, Noriko; Inoue, Tomoyuki; Yasukouchi, Yoshikazu; Akiyama, Hiroshi
2014-01-01
Dietary aluminum (Al) intake by young children, children, youths, and adults in Japan was estimated using the market basket method. The Al content of food category (I–VII) samples for each age group was determined by inductively coupled plasma-atomic emission spectrometry (ICP-AES). The Al content in processed foods and unprocessed foods ranged from 0.40 to 21.7 mg/kg and from 0.32 to 0.54 mg/kg, respectively. For processed foods in all age groups, the Al content in food category VI samples, sugar and confections/savories, was the highest, followed by those in category II, cereals. The daily dietary Al intake from processed foods was much larger than that from unprocessed foods. The mean weekly percentages of the provisional tolerable weekly intake (PTWI, established by the joint FAO/WHO Expert Committee on Food Additives in 2011) from processed foods for all age groups are 43.1, 22.4, 17.6 and 15.1%, respectively. Only the highest consumer Al exposure value (>P95) of the young children group exceeded the PTWI. PMID:25473496
NASA Technical Reports Server (NTRS)
Lyons, Walter A.; Pielke, Roger A.; Cotton, William R.; Keen, Cecil S.; Moon, Dennis A.
1992-01-01
Sea breeze thunderstorms during quiescent synoptic conductions account for 40 percent of Florida rainfall, and are the dominant feature of April-October weather at the Kennedy Space Center (KSC). An effort is presently made to assess the feasibility of a mesoscale numerical model in improving the point-specific thunderstorm forecasting accuracy at the KSC, in the 2-12 hour time frame. Attention is given to the Applied Regional Atmospheric Modeling System.
NASA Astrophysics Data System (ADS)
Housen, B. A.
2015-12-01
Kent and Irving, 2010; and Kent et al, 2015 propose a monster shift in the position of Jurassic (160 to 145 Ma) paleopoles for North America- defined by results from igneous rocks. This monster shift is likely an unrecognized true polar wander occurrence. Although subject to inclination error, results from sedimentary rocks from North America, if corrected for these effects, can be used to supplement the available data for this time period. Steiner (2003) reported results from 48 stratigraphic horizons sampled from the Callovian Summerville Fm, from NE New Mexico. A recalculated mean of these results yields a mean direction of D = 332, I = 39, n=48, k = 15, α95 = 5.4°. These data were analyzed for possible inclination error-although the dataset is small, the E-I results yielded a corrected I = 53. This yields a corrected paleopole for NA at ~165 Ma located at 67° N and 168° E.Paleomagnetic results from the Black Hills- Kilanowski (2002) for the Callovian Hulett Mbr of the Sundance Fm, and Gregiore (2001) the Oxfordian-Tithonian Morrison Fm (Gregiore, 2001) have previously been interpreted to represent Eocene-aged remagnetizations- due to the nearly exact coincidence between the in-situ pole positions of these Jurassic units with the Eocene pole for NA. Both of the tilt-corrected results for these units have high latitude poles (Sundance Fm: 79° N, 146° E; Morrison Fm: 89° N, 165° E). An E-I analysis of these data will be presented- using a provisional inclination error of 10°, corrected paleopoles are: (Sundance Fm: 76° N, 220° E; Morrison Fm: 77° N, 266° E). The Black Hills 165 Ma (Sundance Fm) and 145 Ma (Morrison Fm) poles, provisionally corrected for 10° inclination error- occur fairly close to the NA APWP proposed by Kent et al, 2015- using an updated set of results from kimberlites- the agreement between the Sundance Fm and the Triple-B (158 Ma) pole would be nearly exact with a slightly lesser inclination error. The Summerville Fm- which is
David, Sean P.; Strong, David R.; Leventhal, Adam M.; Lancaster, Molly A.; McGeary, John E.; Munafò, Marcus R.; Bergen, Andrew W.; Swan, Gary E.; Benowitz, Neal L.; Tyndale, Rachel F.; Conti, David V.; Brown, Richard A.; Lerman, Caryn; Niaura, Raymond
2013-01-01
Aims To evaluate associations of treatment and an ‘additive genetic efficacy score’ (AGES) based on dopamine functional polymorphisms with time to first smoking lapse and point prevalence abstinence at end of treatment among participants enrolled in two randomized clinical trials of smoking cessation therapies. Design Double-blind pharmacogenetic efficacy trials randomizing participants to active or placebo bupropion. Study 1 also randomized participants to cognitive-behavioral smoking cessation treatment (CBT) or this treatment with CBT for depression. Study 2 provided standardized behavioural support. Setting Two Hospital-affiliated clinics (Study 1), and two University-affiliated clinics (Study 2). Participants N=792 self-identified white treatment-seeking smokers aged ≥18 years smoking ≥10 cigarettes per day over the last year. Measurements Age, gender, Fagerström Test for Nicotine Dependence, dopamine pathway genotypes (rs1800497 [ANKK1 E713K], rs4680 [COMT V158M], DRD4 exon 3 Variable Number of Tandem Repeats polymorphism [DRD4 VNTR], SLC6A3 3' VNTR) analyzed both separately and as part of an AGES, time to first lapse, and point prevalence abstinence at end of treatment. Findings Significant associations of the AGES (hazard ratio = 1.10, 95% Confidence Interval [CI] = 1.06–1.14], p=0.0099) and of the DRD4 VNTR (HR = 1.29, 95%CI 1.17–1.41, p=0.0073) were observed with time to first lapse. A significant AGES by pharmacotherapy interaction was observed (β [SE]=−0.18 [0.07], p=0.016), such that AGES predicted risk for time to first lapse only for individuals randomized to placebo. Conclusions A score based on functional polymorphisms relating to dopamine pathways appears to predict lapse to smoking following a quit attempt, and the association is mitigated in smokers using bupropion. PMID:23941313
NASA Technical Reports Server (NTRS)
Peng, S. T. J.; Landel, R. F.
1983-01-01
The rheological behavior of progressively shear thickening FM-9 solutions, a time-dependent shear thickening material with characteristics of threshold behavior, is investigated as part of a study of the rheological properties of antimisting jet fuel. Flammability test results and test configurations from various sources are evaluated. A correlation is obtained between the rheological behavior and the flammability tests such that, for a given system, such as a fixed solvent system and the FM-9 polymer system, the flammability criterion can be applied to a wide range of concentrations and temperatures.
Pei, Wuhong; Xu, Lisha; Varshney, Gaurav K.; Carrington, Blake; Bishop, Kevin; Jones, MaryPat; Huang, Sunny C.; Idol, Jennifer; Pretorius, Pamela R.; Beirl, Alisha; Schimmenti, Lisa A.; Kindt, Katie S.; Sood, Raman; Burgess, Shawn M.
2016-01-01
Phosphoribosyl pyrophosphate synthetase-1 (PRPS1) is a key enzyme in nucleotide biosynthesis, and mutations in PRPS1 are found in several human diseases including nonsyndromic sensorineural deafness, Charcot-Marie-Tooth disease-5, and Arts Syndrome. We utilized zebrafish as a model to confirm that mutations in PRPS1 result in phenotypic deficiencies in zebrafish similar to those in the associated human diseases. We found two paralogs in zebrafish, prps1a and prps1b and characterized each paralogous mutant individually as well as the double mutant fish. Zebrafish prps1a mutants and prps1a;prps1b double mutants showed similar morphological phenotypes with increasingly severe phenotypes as the number of mutant alleles increased. Phenotypes included smaller eyes and reduced hair cell numbers, consistent with the optic atrophy and hearing impairment observed in human patients. The double mutant also showed abnormal development of primary motor neurons, hair cell innervation, and reduced leukocytes, consistent with the neuropathy and recurrent infection of the human patients possessing the most severe reductions of PRPS1 activity. Further analyses indicated the phenotypes were associated with a prolonged cell cycle likely resulting from reduced nucleotide synthesis and energy production in the mutant embryos. We further demonstrated the phenotypes were caused by delays in the tissues most highly expressing the prps1 genes. PMID:27425195
Pei, Wuhong; Xu, Lisha; Varshney, Gaurav K; Carrington, Blake; Bishop, Kevin; Jones, MaryPat; Huang, Sunny C; Idol, Jennifer; Pretorius, Pamela R; Beirl, Alisha; Schimmenti, Lisa A; Kindt, Katie S; Sood, Raman; Burgess, Shawn M
2016-01-01
Phosphoribosyl pyrophosphate synthetase-1 (PRPS1) is a key enzyme in nucleotide biosynthesis, and mutations in PRPS1 are found in several human diseases including nonsyndromic sensorineural deafness, Charcot-Marie-Tooth disease-5, and Arts Syndrome. We utilized zebrafish as a model to confirm that mutations in PRPS1 result in phenotypic deficiencies in zebrafish similar to those in the associated human diseases. We found two paralogs in zebrafish, prps1a and prps1b and characterized each paralogous mutant individually as well as the double mutant fish. Zebrafish prps1a mutants and prps1a;prps1b double mutants showed similar morphological phenotypes with increasingly severe phenotypes as the number of mutant alleles increased. Phenotypes included smaller eyes and reduced hair cell numbers, consistent with the optic atrophy and hearing impairment observed in human patients. The double mutant also showed abnormal development of primary motor neurons, hair cell innervation, and reduced leukocytes, consistent with the neuropathy and recurrent infection of the human patients possessing the most severe reductions of PRPS1 activity. Further analyses indicated the phenotypes were associated with a prolonged cell cycle likely resulting from reduced nucleotide synthesis and energy production in the mutant embryos. We further demonstrated the phenotypes were caused by delays in the tissues most highly expressing the prps1 genes. PMID:27425195
NASA Astrophysics Data System (ADS)
Sprenger, Lisa; Lange, Adrian; Odenbach, Stefan
2013-12-01
Ferrofluids are colloidal suspensions consisting of magnetic nanoparticles dispersed in a carrier liquid. Their thermodiffusive behaviour is rather strong compared to molecular binary mixtures, leading to a Soret coefficient (ST) of 0.16 K-1. Former experiments with dilute magnetic fluids have been done with thermogravitational columns or horizontal thermodiffusion cells by different research groups. Considering the horizontal thermodiffusion cell, a former analytical approach has been used to solve the phenomenological diffusion equation in one dimension assuming a constant concentration gradient over the cell's height. The current experimental work is based on the horizontal separation cell and emphasises the comparison of the concentration development in different concentrated magnetic fluids and at different temperature gradients. The ferrofluid investigated is the kerosene-based EMG905 (Ferrotec) to be compared with the APG513A (Ferrotec), both containing magnetite nanoparticles. The experiments prove that the separation process linearly depends on the temperature gradient and that a constant concentration gradient develops in the setup due to the separation. Analytical one dimensional and numerical three dimensional approaches to solve the diffusion equation are derived to be compared with the solution used so far for dilute fluids to see if formerly made assumptions also hold for higher concentrated fluids. Both, the analytical and numerical solutions, either in a phenomenological or a thermodynamic description, are able to reproduce the separation signal gained from the experiments. The Soret coefficient can then be determined to 0.184 K-1 in the analytical case and 0.29 K-1 in the numerical case. Former theoretical approaches for dilute magnetic fluids underestimate the strength of the separation in the case of a concentrated ferrofluid.
NASA Astrophysics Data System (ADS)
Raghavan, V.; Whitney, Scott E.; Ebmeier, Ryan J.; Padhye, Nisha V.; Nelson, Michael; Viljoen, Hendrik J.; Gogos, George
2006-09-01
In this article, experimental and numerical analyses to investigate the thermal control of an innovative vortex tube based polymerase chain reaction (VT-PCR) thermocycler are described. VT-PCR is capable of rapid DNA amplification and real-time optical detection. The device rapidly cycles six 20μl 96bp λ-DNA samples between the PCR stages (denaturation, annealing, and elongation) for 30cycles in approximately 6min. Two-dimensional numerical simulations have been carried out using computational fluid dynamics (CFD) software FLUENT v.6.2.16. Experiments and CFD simulations have been carried out to measure/predict the temperature variation between the samples and within each sample. Heat transfer rate (primarily dictated by the temperature differences between the samples and the external air heating or cooling them) governs the temperature distribution between and within the samples. Temperature variation between and within the samples during the denaturation stage has been quite uniform (maximum variation around ±0.5 and 1.6°C, respectively). During cooling, by adjusting the cold release valves in the VT-PCR during some stage of cooling, the heat transfer rate has been controlled. Improved thermal control, which increases the efficiency of the PCR process, has been obtained both experimentally and numerically by slightly decreasing the rate of cooling. Thus, almost uniform temperature distribution between and within the samples (within 1°C) has been attained for the annealing stage as well. It is shown that the VT-PCR is a fully functional PCR machine capable of amplifying specific DNA target sequences in less time than conventional PCR devices.
Sprenger, Lisa Lange, Adrian; Odenbach, Stefan
2013-12-15
Ferrofluids are colloidal suspensions consisting of magnetic nanoparticles dispersed in a carrier liquid. Their thermodiffusive behaviour is rather strong compared to molecular binary mixtures, leading to a Soret coefficient (S{sub T}) of 0.16 K{sup −1}. Former experiments with dilute magnetic fluids have been done with thermogravitational columns or horizontal thermodiffusion cells by different research groups. Considering the horizontal thermodiffusion cell, a former analytical approach has been used to solve the phenomenological diffusion equation in one dimension assuming a constant concentration gradient over the cell's height. The current experimental work is based on the horizontal separation cell and emphasises the comparison of the concentration development in different concentrated magnetic fluids and at different temperature gradients. The ferrofluid investigated is the kerosene-based EMG905 (Ferrotec) to be compared with the APG513A (Ferrotec), both containing magnetite nanoparticles. The experiments prove that the separation process linearly depends on the temperature gradient and that a constant concentration gradient develops in the setup due to the separation. Analytical one dimensional and numerical three dimensional approaches to solve the diffusion equation are derived to be compared with the solution used so far for dilute fluids to see if formerly made assumptions also hold for higher concentrated fluids. Both, the analytical and numerical solutions, either in a phenomenological or a thermodynamic description, are able to reproduce the separation signal gained from the experiments. The Soret coefficient can then be determined to 0.184 K{sup −1} in the analytical case and 0.29 K{sup −1} in the numerical case. Former theoretical approaches for dilute magnetic fluids underestimate the strength of the separation in the case of a concentrated ferrofluid.
Schubert, Frank; Wiggenhauser, Herbert; Lausch, Regine
2004-04-01
In impact-echo testing of finite concrete structures, reflections of Rayleigh and body waves from lateral boundaries significantly affect time-domain signals and spectra. In the present paper we demonstrate by numerical simulations and experimental measurements at a concrete specimen that these reflections can lead to systematic errors in thickness determination. These effects depend not only on the dimensions of the specimen, but also on the location of the actual measuring point and on the duration of the detected time-domain signal. PMID:15047403
Wendelboe, Mette Høegh; Thomsen, Jesper Skovhus; Henriksen, Kim; Vegger, Jens Bay; Brüel, Annemarie
2016-06-01
In rodents, lactation is associated with a considerable and very rapid bone loss, which almost completely recovers after weaning. The aim of the present study was to investigate whether the bisphosphonate Zoledronate (Zln) can inhibit lactation induced bone loss, and if Zln interferes with recovery of bone mass after lactation has ceased. Seventy-six 10-weeks-old NMRI mice were divided into the following groups: Baseline, Pregnant, Lactation, Lactation+Zln, Recovery, Recovery+Zln, and Virgin Control (age-matched). The lactation period was 12days, then the pups were removed, and thereafter recovery took place for 28days. Zln, 100μg/kg, was given s.c. on the day of delivery, and again 4 and 8days later. Mechanical testing, μCT, and dynamic histomorphometry were performed. At L4, lactation resulted in a substantial loss of bone strength (-55% vs. Pregnant, p<0.01), BV/TV (-40% vs. Pregnant, p<0.01), and trabecular thickness (Tb.Th) (-29% vs. Pregnant, p<0.001). Treatment with Zln completely prevented lactation induced loss of bone strength, BV/TV, and Tb.Th at L4. Full recovery of micro-architectural and mechanical properties was found 28days after weaning in vehicle-treated mice. Interestingly, the recovery group treated with Zln during the lactation period had higher BV/TV (+45%, p<0.01) and Tb.Th (+16%, p<0.05) compared with virgin controls. Similar results were found at the proximal tibia and femur. This indicates that Zln did not interfere with the bone formation taking place after weaning. On this background, we conclude that post-lactation bone formation is not dependent on a preceding lactation induced bone loss. PMID:27021151
NASA Astrophysics Data System (ADS)
Malamataris, Nikolaos; Liakos, Anastasios
2015-11-01
The exact value of the Reynolds number regarding the inception of separation in the flow around a circular cylinder is still a matter of research. This work connects the inception of separation with the calculation of a positive pressure gradient around the circumference of the cylinder. The hypothesis is that inception of separation occurs when the pressure gradient becomes positive around the circumference. From the most cited laboratory experiments that have dealt with that subject of inception of separation only Thom has measured the pressure gradient there at very low Reynolds numbers (up to Re=3.5). For this reason, the experimental conditions of his tunnel are simulated in a new numerical experiment. The full Navier Stokes equations in both two and three dimensions are solved with a home made code that utilizes Galerkin finite elements. In the two dimensional numerical experiment, inception of separation is observed at Re=4.3, which is the lowest Reynolds number where inception has been reported computationally. Currently, the three dimensional experiment is under way, in order to compare if there are effects of three dimensional theory of separation in the conditions of Thom's experiments.
Quarini, G L; Learmonth, I D; Gheduzzi, S
2006-07-01
Acrylic cements are commonly used to attach prosthetic components in joint replacement surgery. The cements set in short periods of time by a complex polymerization of initially liquid monomer compounds into solid structures with accompanying significant heat release. Two main problems arise from this form of fixation: the first is the potential damage caused by the temperature excursion, and the second is incomplete reaction leaving active monomer compounds, which can potentially be slowly released into the patient. This paper presents a numerical model predicting the temperature-time history in an idealized prosthetic-cement-bone system. Using polymerization kinetics equations from the literature, the degree of polymerization is predicted, which is found to be very dependent on the thermal history of the setting process. Using medical literature, predictions for the degree of thermal bone necrosis are also made. The model is used to identify the critical parameters controlling thermal and unreacted monomer distributions. PMID:16898219
NASA Technical Reports Server (NTRS)
Scalapino, D. J.; Sugar, R. L.; White, S. R.; Bickers, N. E.; Scalettar, R. T.
1989-01-01
Numerical simulations on the half-filled three-dimensional Hubbard model clearly show the onset of Neel order. Simulations of the two-dimensional electron-phonon Holstein model show the competition between the formation of a Peierls-CDW state and a superconducting state. However, the behavior of the partly filled two-dimensional Hubbard model is more difficult to determine. At half-filling, the antiferromagnetic correlations grow as T is reduced. Doping away from half-filling suppresses these correlations, and it is found that there is a weak attractive pairing interaction in the d-wave channel. However, the strength of the pair field susceptibility is weak at the temperatures and lattice sizes that have been simulated, and the nature of the low-temperature state of the nearly half-filled Hubbard model remains open.
NASA Astrophysics Data System (ADS)
Chevallier, L.
2010-11-01
Tests are presented of the 1D Accelerated Lambda Iteration method, which is widely used for solving the radiative transfer equation for a stellar atmosphere. We use our ARTY code as a reference solution and tables for these tests are provided. We model a static idealized stellar atmosphere, which is illuminated on its inner face and where internal sources are distributed with weak or strong gradients. This is an extension of published tests for a slab without incident radiation and gradients. Typical physical conditions for the continuum radiation and spectral lines are used, as well as typical values for the numerical parameters in order to reach a 1% accuracy. It is shown that the method is able to reach such an accuracy for most cases but the spatial discretization has to be refined for strong gradients and spectral lines, beyond the scope of realistic stellar atmospheres models. Discussion is provided on faster methods.
NASA Astrophysics Data System (ADS)
Losiak, Anna; Czechowski, Leszek; Velbel, Michael A.
2015-12-01
Gypsum, a mineral that requires water to form, is common on the surface of Mars. Most of it originated before 3.5 Gyr when the Red Planet was more humid than now. However, occurrences of gypsum dune deposits around the North Polar Residual Cap (NPRC) seem to be surprisingly young: late Amazonian in age. This shows that liquid water was present on Mars even at times when surface conditions were as cold and dry as the present-day. A recently proposed mechanism for gypsum formation involves weathering of dust within ice (e.g., Niles, P.B., Michalski, J. [2009]. Nat. Geosci. 2, 215-220.). However, none of the previous studies have determined if this process is possible under current martian conditions. Here, we use numerical modelling of heat transfer to show that during the warmest days of the summer, solar irradiation may be sufficient to melt pure water ice located below a layer of dark dust particles (albedo ⩽ 0.13) lying on the steepest sections of the equator-facing slopes of the spiral troughs within martian NPRC. During the times of high irradiance at the north pole (every 51 ka; caused by variation of orbital and rotational parameters of Mars e.g., Laskar, J. et al. [2002]. Nature 419, 375-377.) this process could have taken place over larger parts of the spiral troughs. The existence of small amounts of liquid water close to the surface, even under current martian conditions, fulfils one of the main requirements necessary to explain the formation of the extensive gypsum deposits around the NPRC. It also changes our understanding of the degree of current geological activity on Mars and has important implications for estimating the astrobiological potential of Mars.
NASA Astrophysics Data System (ADS)
Wildman, R. D.; Jenkins, J. T.; Krouskop, P. E.; Talbot, J.
2006-07-01
A comparison of the predictions of a simple kinetic theory with experimental and numerical results for a vibrated granular bed consisting of nearly elastic particles of two sizes has been performed. The results show good agreement between the data sets for a range of numbers of each size of particle, and are particularly good for particle beds containing similar proportions of each species. The agreement suggests that such a model may be a good starting point for describing polydisperse systems of granular flows.
Schäfer, Dirk; Köber, Ralf; Dahmke, Andreas
2003-09-01
The successful dechlorination of mixtures of chlorinated hydrocarbons with zero-valent metals requires information concerning the kinetics of simultaneous degradation of different contaminants. This includes intraspecies competitive effects (loading of the reactive iron surface by a single contaminant) as well as interspecies competition of several contaminants for the reactive sites available. In columns packed with zero-valent iron, the degradation behaviour of trichloroethylene (TCE), cis-dichloroethylene (DCE) and mixtures of both was measured in order to investigate interspecies competition. Although a decreasing rate of dechlorination is to be expected, when several degradable substances compete for the reactive sites on the iron surface, TCE degradation is nearly unaffected by the presence of cis-DCE. In contrast, cis-DCE degradation rates decrease significantly when TCE is added. A new modelling approach is developed in order to identify and quantify the observed competitive effects. The numerical model TBC (Transport, Biochemistry and Chemistry, Schäfer et al., 1998a) is used to describe adsorption, desorption and dechlorination in a mechanistic way. Adsorption and degradation of a contaminant based on a limited number of reactive sites leads to a combined zero- and first-order degradation kinetics for high and low concentrations, respectively. The adsorption of several contaminants with different sorption parameters to a limited reactive surface causes interspecies competition. The reaction scheme and the parameters required are successfully transferred from Arnold and Roberts (2000b) to the model TBC. The degradation behaviour of the mixed contamination observed in the column experiments can be related to the adsorption properties of TCE and cis-DCE. By predicting the degradation of the single substances TCE and cis-DCE as well as mixtures of both, the calibrated model is used to investigate the effects of interspecies competition on the design of
NASA Astrophysics Data System (ADS)
Schäfer, Dirk; Köber, Ralf; Dahmke, Andreas
2003-09-01
The successful dechlorination of mixtures of chlorinated hydrocarbons with zero-valent metals requires information concerning the kinetics of simultaneous degradation of different contaminants. This includes intraspecies competitive effects (loading of the reactive iron surface by a single contaminant) as well as interspecies competition of several contaminants for the reactive sites available. In columns packed with zero-valent iron, the degradation behaviour of trichloroethylene (TCE), cis-dichloroethylene (DCE) and mixtures of both was measured in order to investigate interspecies competition. Although a decreasing rate of dechlorination is to be expected, when several degradable substances compete for the reactive sites on the iron surface, TCE degradation is nearly unaffected by the presence of cis-DCE. In contrast, cis-DCE degradation rates decrease significantly when TCE is added. A new modelling approach is developed in order to identify and quantify the observed competitive effects. The numerical model TBC (Transport, Biochemistry and Chemistry, Schäfer et al., 1998a) is used to describe adsorption, desorption and dechlorination in a mechanistic way. Adsorption and degradation of a contaminant based on a limited number of reactive sites leads to a combined zero- and first-order degradation kinetics for high and low concentrations, respectively. The adsorption of several contaminants with different sorption parameters to a limited reactive surface causes interspecies competition. The reaction scheme and the parameters required are successfully transferred from Arnold and Roberts (2000b) to the model TBC. The degradation behaviour of the mixed contamination observed in the column experiments can be related to the adsorption properties of TCE and cis-DCE. By predicting the degradation of the single substances TCE and cis-DCE as well as mixtures of both, the calibrated model is used to investigate the effects of interspecies competition on the design of
NASA Astrophysics Data System (ADS)
Rawat, A.; Aucan, J.; Ardhuin, F.
2012-12-01
All sea level variations of the order of 1 cm at scales under 30 km are of great interest for the future Surface Water Ocean Topography (SWOT) satellite mission. That satellite should provide high-resolution maps of the sea surface height for analysis of meso to sub-mesoscale currents, but that will require a filtering of all gravity wave motions in the data. Free infragravity waves (FIGWs) are generated and radiate offshore when swells and/or wind seas and their associated bound infragravity waves impact exposed coastlines. Free infragravity waves have dominant periods comprised between 1 and 10 minutes and horizontal wavelengths of up to tens of kilometers. Given the length scales of the infragravity waves wavelength and amplitude, the infragravity wave field will can a significant fraction the signal measured by the future SWOT mission. In this study, we analyze the data from recovered bottom pressure recorders of the Deep-ocean Assessment and Reporting of Tsunami (DART) program. This analysis includes data spanning several years between 2006 and 2010, from stations at different latitudes in the North and South Pacific, the North Atlantic, the Gulf of Mexico and the Caribbean Sea. We present and discuss the following conclusions: (1) The amplitude of free infragravity waves can reach several centimeters, higher than the precision sought for the SWOT mission. (2) The free infragravity signal is higher in the Eastern North Pacific than in the Western North Pacific, possibly due to smaller incident swell and seas impacting the nearby coastlines. (3) Free infragravity waves are higher in the North Pacific than in the North Atlantic, possibly owing to different average continental shelves configurations in the two basins. (4) There is a clear seasonal cycle at the high latitudes North Atlantic and Pacific stations that is much less pronounced or absent at the tropical stations, consistent with the generation mechanism of free infragravity waves. Our numerical model
Lane, J.W., Jr.; Buursink, M.L.; Haeni, F.P.; Versteeg, R.J.
2000-01-01
The suitability of common-offset ground-penetrating radar (GPR) to detect free-phase hydrocarbons in bedrock fractures was evaluated using numerical modeling and physical experiments. The results of one- and two-dimensional numerical modeling at 100 megahertz indicate that GPR reflection amplitudes are relatively insensitive to fracture apertures ranging from 1 to 4 mm. The numerical modeling and physical experiments indicate that differences in the fluids that fill fractures significantly affect the amplitude and the polarity of electromagnetic waves reflected by subhorizontal fractures. Air-filled and hydrocarbon-filled fractures generate low-amplitude reflections that are in-phase with the transmitted pulse. Water-filled fractures create reflections with greater amplitude and opposite polarity than those reflections created by air-filled or hydrocarbon-filled fractures. The results from the numerical modeling and physical experiments demonstrate it is possible to distinguish water-filled fracture reflections from air- or hydrocarbon-filled fracture reflections, nevertheless subsurface heterogeneity, antenna coupling changes, and other sources of noise will likely make it difficult to observe these changes in GPR field data. This indicates that the routine application of common-offset GPR reflection methods for detection of hydrocarbon-filled fractures will be problematic. Ideal cases will require appropriately processed, high-quality GPR data, ground-truth information, and detailed knowledge of subsurface physical properties. Conversely, the sensitivity of GPR methods to changes in subsurface physical properties as demonstrated by the numerical and experimental results suggests the potential of using GPR methods as a monitoring tool. GPR methods may be suited for monitoring pumping and tracer tests, changes in site hydrologic conditions, and remediation activities.The suitability of common-offset ground-penetrating radar (GPR) to detect free-phase hydrocarbons
Durham, M.D.
1993-08-13
ADA Technologies, Inc. (ADA) has completed the bench-scale testing phase of a program to evaluate additives that will improve the collection of fine particles in electrostatic precipitators (ESPs). A bench-scale ESP was installed at the Consolidation Coal Company (CONSOL) combustion research and development facility in Library, PA in order to conduct the evaluation. During a two-week test, four candidate additives were injected into the flue gas ahead of a 100 acfm ESP to determine the effect on fly ash collectability. Two additives were found to reduce the emissions from the ESP. Additives ``C`` and ``D`` performed better than initially anticipated -- reducing emissions initially by 17%. Emissions were reduced by 27% after the ESP was modified by the installation of baffles to minimize sneakage. In addition to the measured improvements in performance, no detrimental effects (i.e., electrode fouling) were observed in the operation of the ESP during the testing. The measures of success identified for the bench-scale phase of the program have been surpassed. Since the additives will affect only non-rapping reentrainment particle losses, it is expected that an even greater improvement in particle collection will be observed in larger-scale ESPs. Therefore, positive results are anticipated during the pilot-scale phase of the program and during a future full-scale demonstration test. A preliminary economic analysis was performed to evaluate the cost of the additive process and to compare its costs against alternative means for reducing emissions from ESPs. The results show that conditioning with additive C at a rate of 0.05% (wt. additive to wt. fly ash) is much less expensive than adding new ESP capacity, and more cost competitive than existing chemical conditioning processes. Preliminary chemical analysis of conditioned fly ash shows that it passes the Toxicity Characteristic Leaching Procedure criteria.
Benedetti, Andrea; Platt, Robert; Atherton, Juli
2014-01-01
Background Over time, adaptive Gaussian Hermite quadrature (QUAD) has become the preferred method for estimating generalized linear mixed models with binary outcomes. However, penalized quasi-likelihood (PQL) is still used frequently. In this work, we systematically evaluated whether matching results from PQL and QUAD indicate less bias in estimated regression coefficients and variance parameters via simulation. Methods We performed a simulation study in which we varied the size of the data set, probability of the outcome, variance of the random effect, number of clusters and number of subjects per cluster, etc. We estimated bias in the regression coefficients, odds ratios and variance parameters as estimated via PQL and QUAD. We ascertained if similarity of estimated regression coefficients, odds ratios and variance parameters predicted less bias. Results Overall, we found that the absolute percent bias of the odds ratio estimated via PQL or QUAD increased as the PQL- and QUAD-estimated odds ratios became more discrepant, though results varied markedly depending on the characteristics of the dataset Conclusions Given how markedly results varied depending on data set characteristics, specifying a rule above which indicated biased results proved impossible. This work suggests that comparing results from generalized linear mixed models estimated via PQL and QUAD is a worthwhile exercise for regression coefficients and variance components obtained via QUAD, in situations where PQL is known to give reasonable results. PMID:24416249
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.
NASA Astrophysics Data System (ADS)
Shmelkov, Yuriy; Samujlov, Eugueny
2012-04-01
Comparison of calculation results of transport properties of the solid fuels combustion products was made with known experimental data. Calculation was made by means of the modified program TETRAN developed in G.M. Krzhizhanovsky Power Engineering Institute. The calculation was spent with chemical reactions and phase transformations occurring during combustion. Also ionization of products of solid fuels combustion products at high temperatures was taken into account. In the capacity of fuels various Russian coals and some other solid fuels were considered. As a result of density, viscosity and heat conductivity calculation of a gas phase of solid fuels combustion products the data has been obtained in a range of temperatures 500-20000 K. This comparison has shown good convergence of calculation results with experiment.
Abberger, T
2001-12-01
The aim of the study was to investigate melt granulation in a laboratory scale fluid-bed granulator with respect to granule growth, granule properties and resulting tablet properties. The parameters investigated were method of addition of PEG (spray-on or addition as flakes), binder concentration, PEG type (3000, 4000 and 6000, sprayed-on), size (PEG 4000, added as three different sized flakes), powder type (two different sized lactose types and corn starch) and operating conditions (volume air flow and heating temperature). Addition of binder as flakes led to layering as a growth mechanism when the size of the flakes was high. Coalescence occurred when the size was low. Coalescence also occurred when spraying was the method of addition. Due to the greater viscosity of the PEG 6000 melt it produced bigger granules than 3000 or 4000. The influence of volume air flow was moderate and the influence of heating temperature in the range of 70-90 degrees C was very low with both methods of addition. The disintegration time of tablets from granules where PEG was added as flakes was shorter than from granules where PEG was sprayed-on. The latter method of binder addition led to tablets which did not disintegrate but eroded. This was apparently caused by formation of a binder matrix, which could not be destroyed by the disintegrant. PMID:11802658
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
NASA Technical Reports Server (NTRS)
Durisen, R. H.
1975-01-01
Improved viscous evolutionary sequences of differentially rotating, axisymmetric, nonmagnetic, zero-temperature white-dwarf models are constructed using the relativistically corrected degenerate electron viscosity. The results support the earlier conclusion that angular momentum transport due to viscosity does not lead to overall uniform rotation in many interesting cases. Qualitatively different behaviors are obtained, depending on how the total mass M and angular momentum J compare with the M and J values for which uniformly rotating models exist. Evolutions roughly determine the region in M and J for which models with a particular initial angular momentum distribution can reach carbon-ignition densities in 10 b.y. Such models may represent Type I supernova precursors.
NASA Astrophysics Data System (ADS)
Wang, Ten-See; Dumas, Catherine
1993-07-01
A computational fluid dynamics (CFD) model has been applied to study the transient flow phenomena of the nozzle and exhaust plume of the Space Shuttle Main Engine (SSME), fired at sea level. The CFD model is a time accurate, pressure based, reactive flow solver. A six-species hydrogen/oxygen equilibrium chemistry is used to describe the chemical-thermodynamics. An adaptive upwinding scheme is employed for the spatial discretization, and a predictor, multiple corrector method is used for the temporal solution. Both engine start-up and shut-down processes were simulated. The elapse time is approximately five seconds for both cases. The computed results were animated and compared with the test. The images for the animation were created with PLOT3D and FAST and then animated with ABEKAS. The hysteresis effects, and the issues of free-shock separation, restricted-shock separation and the end-effects were addressed.
NASA Technical Reports Server (NTRS)
Wang, Ten-See; Dumas, Catherine
1993-01-01
A computational fluid dynamics (CFD) model has been applied to study the transient flow phenomena of the nozzle and exhaust plume of the Space Shuttle Main Engine (SSME), fired at sea level. The CFD model is a time accurate, pressure based, reactive flow solver. A six-species hydrogen/oxygen equilibrium chemistry is used to describe the chemical-thermodynamics. An adaptive upwinding scheme is employed for the spatial discretization, and a predictor, multiple corrector method is used for the temporal solution. Both engine start-up and shut-down processes were simulated. The elapse time is approximately five seconds for both cases. The computed results were animated and compared with the test. The images for the animation were created with PLOT3D and FAST and then animated with ABEKAS. The hysteresis effects, and the issues of free-shock separation, restricted-shock separation and the end-effects were addressed.
NASA Technical Reports Server (NTRS)
Uslenghi, Piergiorgio L. E.; Laxpati, Sharad R.; Kawalko, Stephen F.
1993-01-01
The third phase of the development of the computer codes for scattering by coated bodies that has been part of an ongoing effort in the Electromagnetics Laboratory of the Electrical Engineering and Computer Science Department at the University of Illinois at Chicago is described. The work reported discusses the analytical and numerical results for the scattering of an obliquely incident plane wave by impedance bodies of revolution with phi variation of the surface impedance. Integral equation formulation of the problem is considered. All three types of integral equations, electric field, magnetic field, and combined field, are considered. These equations are solved numerically via the method of moments with parametric elements. Both TE and TM polarization of the incident plane wave are considered. The surface impedance is allowed to vary along both the profile of the scatterer and in the phi direction. Computer code developed for this purpose determines the electric surface current as well as the bistatic radar cross section. The results obtained with this code were validated by comparing the results with available results for specific scatterers such as the perfectly conducting sphere. Results for the cone-sphere and cone-cylinder-sphere for the case of an axially incident plane were validated by comparing the results with the results with those obtained in the first phase of this project. Results for body of revolution scatterers with an abrupt change in the surface impedance along both the profile of the scatterer and the phi direction are presented.
NASA Astrophysics Data System (ADS)
Humeau, Anne; Buard, Benjamin; Mahé, Guillaume; Chapeau-Blondeau, François; Rousseau, David; Abraham, Pierre
2010-10-01
To contribute to the understanding of the complex dynamics in the cardiovascular system (CVS), the central CVS has previously been analyzed through multifractal analyses of heart rate variability (HRV) signals that were shown to bring useful contributions. Similar approaches for the peripheral CVS through the analysis of laser Doppler flowmetry (LDF) signals are comparatively very recent. In this direction, we propose here a study of the peripheral CVS through a multifractal analysis of LDF fluctuations, together with a comparison of the results with those obtained on HRV fluctuations simultaneously recorded. To perform these investigations concerning the biophysics of the CVS, first we have to address the problem of selecting a suitable methodology for multifractal analysis, allowing us to extract meaningful interpretations on biophysical signals. For this purpose, we test four existing methodologies of multifractal analysis. We also present a comparison of their applicability and interpretability when implemented on both simulated multifractal signals of reference and on experimental signals from the CVS. One essential outcome of the study is that the multifractal properties observed from both the LDF fluctuations (peripheral CVS) and the HRV fluctuations (central CVS) appear very close and similar over the studied range of scales relevant to physiology.