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.
Anisotropic halo model: implementation and numerical results
NASA Astrophysics Data System (ADS)
Sgró, Mario A.; Paz, Dante J.; Merchán, Manuel
2013-07-01
In the present work, we extend the classic halo model for the large-scale matter distribution including a triaxial model for the halo profiles and their alignments. In particular, we derive general expressions for the halo-matter cross-correlation function. In addition, by numerical integration, we obtain instances of the cross-correlation function depending on the directions given by halo shape axes. These functions are called anisotropic cross-correlations. With the aim of comparing our theoretical results with the simulations, we compute averaged anisotropic correlations in cones with their symmetry axis along each shape direction of the centre halo. From these comparisons we characterize and quantify the alignment of dark matter haloes on the Λcold dark matter context by means of the presented anisotropic halo model. Since our model requires multidimensional integral computation we implement a Monte Carlo method on GPU hardware which allows us to increase the precision of the results and it improves the performance of the computation.
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.
Testing Numerical Dynamo Models Against Experimental Results
NASA Astrophysics Data System (ADS)
Gissinger, C. J.; Fauve, S.; Dormy, E.
2007-12-01
Significant progress has been achieved over the past few years in describing the geomagnetic field using computer models for dynamo action. Such models are so far limited to parameter regimes which are very remote from actual values relevant to the Earth core or any liquid metal (the magnetic Prandtl number is always over estimated by a factor at least 104). While existing models successfully reproduce many of the magnetic observations, it is difficult to assert their validity. The recent success of an experimental homogeneous unconstrained dynamo (VKS) provides a new way to investigate dynamo action in turbulent conducting flows, but it also offers a chance to test the validity of exisiting numerical models. We use a code originaly written for the Geodynamo (Parody) and apply it to the experimental configuration. The direct comparison of simulations and experiments is of great interest to test the predictive value of numerical simulations for dynamo action. These turbulent simulations allow us to approach issues which are very relevant for geophysical dynamos, especially the competition between different magnetic modes and the dynamics of reversals.
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.
Numerical results for extended field method applications. [thin plates
NASA Technical Reports Server (NTRS)
Donaldson, B. K.; Chander, S.
1973-01-01
This paper presents the numerical results obtained when a new method of analysis, called the extended field method, was applied to several thin plate problems including one with non-rectangular geometry, and one problem involving both beams and a plate. The numerical results show that the quality of the single plate solutions was satisfactory for all cases except those involving a freely deflecting plate corner. The results for the beam and plate structure were satisfactory even though the structure had a freely deflecting corner.
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
Numerical Simulation of Micronozzles with Comparison to Experimental Results
NASA Astrophysics Data System (ADS)
Thornber, B.; Chesta, E.; Gloth, O.; Brandt, R.; Schwane, R.; Perigo, D.; Smith, P.
2004-10-01
A numerical analysis of conical micronozzle flows has been conducted using the commercial software package CFD-RC FASTRAN [13]. The numerical results have been validated by comparison with direct thrust and mass flow measurements recently performed in ESTEC Propulsion Laboratory on Polyflex Space Ltd. 10mN Cold-Gas thrusters in the frame of ESA CryoSat mission. The flow is viscous dominated, with a throat Reynolds number of 5000, and the relatively large length of the nozzle causes boundary layer effects larger than usual for nozzles of this size. This paper discusses in detail the flow physics such as boundary layer growth and structure, and the effects of rarefaction. Furthermore a number of different domain sizes and exit boundary conditions are used to determine the optimum combination of computational time and accuracy.
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.
Modeling extracellular electrical stimulation: II. Computational validation and numerical results.
Tahayori, Bahman; Meffin, Hamish; Dokos, Socrates; Burkitt, Anthony N; Grayden, David B
2012-12-01
The validity of approximate equations describing the membrane potential under extracellular electrical stimulation (Meffin et al 2012 J. Neural Eng. 9 065005) is investigated through finite element analysis in this paper. To this end, the finite element method is used to simulate a cylindrical neurite under extracellular stimulation. Laplace's equations with appropriate boundary conditions are solved numerically in three dimensions and the results are compared to the approximate analytic solutions. Simulation results are in agreement with the approximate analytic expressions for longitudinal and transverse modes of stimulation. The range of validity of the equations describing the membrane potential for different values of stimulation and neurite parameters are presented as well. The results indicate that the analytic approach can be used to model extracellular electrical stimulation for realistic physiological parameters with a high level of accuracy.
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.
Numerical Method for the Design of Healing Chamber in Additive-Manufactured Dental Implants.
Lee, Hsiao-Chien; Tsai, Pei-I; Huang, Chih-Chieh; Chen, San-Yuan; Chao, Chuen-Guang; Tsou, Nien-Ti
2017-01-01
The inclusion of a healing chamber in dental implants has been shown to promote biological healing. In this paper, a novel numerical approach to the design of the healing chamber for additive-manufactured dental implants is proposed. This study developed an algorithm for the modeling of bone growth and employed finite element method in ANSYS to facilitate the design of healing chambers with a highly complex configuration. The model was then applied to the design of dental implants for insertion into the posterior maxillary bones. Two types of ITI® solid cylindrical screwed implant with extra rectangular-shaped healing chamber as an initial design are adopted, with which to evaluate the proposed system. This resulted in several configurations for the healing chamber, which were then evaluated based on the corresponding volume fraction of healthy surrounding bone. The best of these implants resulted in a healing chamber surrounded by around 9.2% more healthy bone than that obtained from the original design. The optimal design increased the contact area between the bone and implant by around 52.9%, which is expected to have a significant effect on osseointegration. The proposed approach is highly efficient which typically completes the optimization of each implant within 3-5 days on an ordinary personal computer. It is also sufficiently general to permit extension to various loading conditions.
Numerical Method for the Design of Healing Chamber in Additive-Manufactured Dental Implants
Lee, Hsiao-Chien; Tsai, Pei-I; Huang, Chih-Chieh; Chen, San-Yuan; Chao, Chuen-Guang
2017-01-01
The inclusion of a healing chamber in dental implants has been shown to promote biological healing. In this paper, a novel numerical approach to the design of the healing chamber for additive-manufactured dental implants is proposed. This study developed an algorithm for the modeling of bone growth and employed finite element method in ANSYS to facilitate the design of healing chambers with a highly complex configuration. The model was then applied to the design of dental implants for insertion into the posterior maxillary bones. Two types of ITI® solid cylindrical screwed implant with extra rectangular-shaped healing chamber as an initial design are adopted, with which to evaluate the proposed system. This resulted in several configurations for the healing chamber, which were then evaluated based on the corresponding volume fraction of healthy surrounding bone. The best of these implants resulted in a healing chamber surrounded by around 9.2% more healthy bone than that obtained from the original design. The optimal design increased the contact area between the bone and implant by around 52.9%, which is expected to have a significant effect on osseointegration. The proposed approach is highly efficient which typically completes the optimization of each implant within 3–5 days on an ordinary personal computer. It is also sufficiently general to permit extension to various loading conditions. PMID:28293628
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.
Comparison of experimental results with numerical simulations for pulsed thermographic NDE
NASA Astrophysics Data System (ADS)
Sripragash, Letchuman; Sundaresan, Mannur
2017-02-01
This paper examines pulse thermographic nondestructive evaluation of flat bottom holes of isotropic materials. Different combinations of defect diameters and depths are considered. Thermographic Signal Reconstruction (TSR) method is used to analyze these results. In addition, a new normalization procedure is used to remove the dependence of thermographic results on the material properties and instrumentation settings during these experiments. Hence the normalized results depend only on the geometry of the specimen and the defects. These thermographic NDE procedures were also simulated using finite element technique for a variety of defect configurations. The data obtained from numerical simulations were also processed using the normalization scheme. Excellent agreement was seen between the results obtained from experiments and numerical simulations. Therefore, the scheme is extended to introduce a correlation technique by which numerical simulations are used to quantify the defect parameters.
Additional Results of Glaze Icing Scaling in SLD Conditions
NASA Technical Reports Server (NTRS)
Tsao, Jen-Ching
2016-01-01
This presentation reports results from recent icing scaling tests in NASA Glenn Icing Research Tunnel (IRT) to evaluate how well the scaling method recommended for Appendix C conditions might apply to SLD conditions.
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.
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 inches and the scale model had a chord of 21 inches. Reference tests were run with airspeeds of 100 and 130.3 knots and with MVD's of 85 and 170 microns. Two scaling methods were considered. One was based on the modified Ruff method with scale velocity found by matching the Weber number W (sub eL). 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 non-dimensional water-film thickness expression and the film Weber number W (sub ef). All tests were conducted at 0 degrees angle of arrival. Results will be presented for stagnation freezing fractions of 0.2 and 0.3. For non-dimensional reference and scale ice shape comparison, a new post-scanning ice shape digitization procedure was developed for extracting 2-dimensional ice shape profiles at any selected span-wise location from the high fidelity 3-dimensional scanned ice shapes obtained in the IRT.
Naito, M; Miura, H
2001-03-01
Using a cutoff design (J. Bisanz, F. J. Morrison, & M. Dunn, 1995) to separate school-related influences from those that are age related, the study investigated the development of number concepts and addition skills in Japanese children. Three groups of kindergarten and 1st grade children who differed in age and/or school experiences completed tasks on their numerical competencies 1 and 6 months after school entrance. Children's use of addition strategies, rather than their solution accuracy, changed primarily as a function of schooling, not age. Children's Base 10 number concepts improved with the amount of schooling, as well as with other social and age-related factors. Results suggest that schooling is an important determinant in developing Japanese-speaking children's numerical competencies, which were not explained solely by their language characteristics or by age-related factors.
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 Astrophysics Data System (ADS)
Behrens, B.-A.; Bonk, C.; Grbic, N.; Vucetic, M.
2017-02-01
By sheet metal forming processes the forming limits and part characteristics are defined through the process specific loads. In deep drawing processes the maximum deep draw ratios as well as the springback behaviour of the metal parts are depending on the stress distribution in the part material during the forming process. While exceeding the load limits, a failure in the material occurs, which can be avoided by additional force transmission activated in the deep drawing process before the forming limit of material is achieved. This contribution deals with numerical investigation of process effect caused by additional force transmission regarding the extension of the process limits. Here, the steel material HCT 600X+Z (1.0941) in thickness s 0 = 1.0 mm is analyzed numerically using the anisotropic model Hill48. This model is validated by the means of cup test by Swift. Both, the FEA of conventional and forming process with additional force transmission are carried out. The numerical results are compared with reference geometry of rectangle cup.
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.
An original traffic additional emission model and numerical simulation on a signalized road
NASA Astrophysics Data System (ADS)
Zhu, Wen-Xing; Zhang, Jing-Yu
2017-02-01
Based on VSP (Vehicle Specific Power) model traffic real emissions were theoretically classified into two parts: basic emission and additional emission. An original additional emission model was presented to calculate the vehicle's emission due to the signal control effects. Car-following model was developed and used to describe the traffic behavior including cruising, accelerating, decelerating and idling at a signalized intersection. Simulations were conducted under two situations: single intersection and two adjacent intersections with their respective control policy. Results are in good agreement with the theoretical analysis. It is also proved that additional emission model may be used to design the signal control policy in our modern traffic system to solve the serious environmental problems.
Aeolian Simulations: A Comparison of Numerical and Experimental Results
NASA Astrophysics Data System (ADS)
Mathews, O.; Burr, D. M.; Bridges, N. T.; Lyne, J. E.; Marshall, J. R.; Greeley, R.; White, B. R.; Hills, J.; Smith, K.; Prissel, T. C.; Aliaga-Caro, J. F.
2010-12-01
Aeolian processes are a major geomorphic agent on solid planetary bodies with atmospheres (Earth, Mars, Venus, and Titan). This paper describes preliminary efforts to model aeolian saltation using computational fluid dynamics (CFD) and to compare the results with those obtained in wind tunnel testing conducted in the Planetary Aeolian Laboratory at NASA Ames Research Center at ambient pressure. The end goal of the project is to develop an experimentally validated CFD approach for modeling aeolian sediment transport on Titan and other planetary bodies. The MARSWIT open-circuit tunnel in this work was specifically designed for atmospheric boundary layer studies. It is a variable-speed, continuous flow tunnel with a test section 1.0 m by 1.2 m in size; the tunnel is able to operate at pressures from 10 millibar to one atmosphere. Flow trips near the tunnel inlet ensure a fully developed, turbulent boundary layer in the test section. Wind speed and axial velocity profiles can be measured with a traversing pitot tube. In this study, sieved walnut shell particles (Greeley et al. 1976) with a density of ~1.1 g/cm3 were used to correlate the low gravity conditions and low sediment density on a body of interest to that of Earth. This sediment was placed in the tunnel, and the freestream airspeed raised to 5.4 m/s. A Phantom v12 camera imaged the resulting particle motion at 1000 frames per second, which was analyzed with ImageJ open-source software (Fig. 1). Airflow in the tunnel was modeled with FLUENT, a commercial CFD program. The turbulent scheme used in FLUENT to obtain closed-form solutions to the Navier-Stokes equations was a 1st Order, k-epsilon model. These methods produced computational velocity profiles that agree with experimental data to within 5-10%. Once modeling of the flow field had been achieved, a Euler-Lagrangian scheme was employed, treating the particles as spheres and tracking each particle at its center. The particles are assumed to interact with
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.
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
Macroscopic laws for immiscible two-phase flow in porous media: Results From numerical experiments
NASA Astrophysics Data System (ADS)
Rothman, Daniel H.
1990-06-01
Flow through porous media may be described at either of two length scales. At the scale of a single pore, fluids flow according to the Navier-Stokes equations and the appropriate boundary conditions. At a larger, volume-averaged scale, the flow is usually thought to obey a linear Darcy law relating flow rates to pressure gradients and body forces via phenomenological permeability coefficients. Aside from the value of the permeability coefficient, the slow flow of a single fluid in a porous medium is well-understood within this framework. The situation is considerably different, however, for the simultaneous flow of two or more fluids: not only are the phenomenological coefficients poorly understood, but the form of the macroscopic laws themselves is subject to question. I describe a numerical study of immiscible two-phase flow in an idealized two-dimensional porous medium constructed at the pore scale. Results show that the macroscopic flow is a nonlinear function of the applied forces for sufficiently low levels of forcing, but linear thereafter. The crossover, which is not predicted by conventional models, occurs when viscous forces begin to dominate capillary forces; i.e., at a sufficiently high capillary number. In the linear regime, the flow may be described by the linear phenomenological law ui = ΣjLijfj, where the flow rate ui of the ith fluid is related to the force fj applied to the jth fluid by the matrix of phenomenological coefficients Lij which depends on the relative concentrations of the two fluids. The diagonal terms are proportional to quantities commonly referred to as "relative permeabilities." The cross terms represent viscous coupling between the two fluids; they are conventionally assumed to be negligible and require special experimental procedures to observe in a laboratory. In contrast, in this numerical study the cross terms are straightforward to measure and are found to be of significant size. The cross terms are additionally observed to
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.
NASA Astrophysics Data System (ADS)
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.
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.
Addition theorem of Slater type orbitals: a numerical evaluation of Barnett Coulson/Löwdin functions
NASA Astrophysics Data System (ADS)
Bouferguene, Ahmed
2005-04-01
When using the one-centre two-range expansion method to evaluate multicentre integrals over Slater type orbitals (STOs), it may become necessary to compute numerical values of the corresponding Fourier coefficients, also known as Barnett-Coulson/Löwdin Functions (BCLFs) (Bouferguene and Jones 1998 J. Chem. Phys. 109 5718). To carry out this task, it is crucial to not only have a stable numerical procedure but also a fast algorithm. In previous work (Bouferguene and Rinaldi 1994 Int. J. Quantum Chem. 50 21), BCLFs were represented by a double integral which led to a numerically stable algorithm but this turned out to be disappointingly time consuming. The present work aims at exploring another path in which BCLFs are represented either by an infinite series involving modified Bessel functions {\\bf K}_{\
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.
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.
Some Numerical Results of Multipoints Bomndary Value Problems Arise in Environmental Protection
NASA Astrophysics Data System (ADS)
Pop, Daniel N.
2016-12-01
In this paper, we investigate two problems arise in pollutant transport in rivers, and we give some numerical results to approximate this solutions. We determined the approximate solutions using two numerical methods: 1. B-splines combined with Runge-Kutta methods, 2. BVP4C solver of MATLAB and then we compare the run-times.
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.
NASA Astrophysics Data System (ADS)
Dimitropoulos, Costas D.; Beris, Antony N.; Sureshkumar, R.; Handler, Robert A.
1998-11-01
This work continues our attempts to elucidate theoretically the mechanism of polymer-induced drag reduction through direct numerical simulations of turbulent channel flow, using an independently evaluated rheological model for the polymer stress. Using appropriate scaling to accommodate effects due to viscoelasticity reveals that there exists a great consistency in the results for different combinations of the polymer concentration and chain extension. This helps demonstrate that our obervations are applicable to very dilute systems, currently not possible to simulate. It also reinforces the hypothesis that one of the prerequisites for the phenomenon of drag reduction is sufficiently enhanced extensional viscosity, corresponding to the level of intensity and duration of extensional rates typically encountered during the turbulent flow. Moreover, these results motivate a study of the turbulence structure at larger Reynolds numbers and for different periodic computational cell sizes. In addition, the Reynolds stress budgets demonstrate that flow elasticity adversely affects the activities represented by the pressure-strain correlations, leading to a redistribution of turbulent kinetic energy amongst all directions. Finally, we discuss the influence of viscoelasticity in reducing the production of streamwise vorticity.
Exact and numerical results for a dimerized coupled spin- 1/2 chain
Martins; Nienhuis
2000-12-04
We establish exact results for coupled spin-1/2 chains for special values of the four-spin interaction V and dimerization parameter delta. The first exact result is at delta = 1/2 and V = -2. Because we find a very small but finite gap in this dimerized chain, this can serve as a very strong test case for numerical and approximate analytical techniques. The second result is for the homogeneous chain with V = -4 and gives evidence that the system has a spontaneously dimerized ground state. Numerical diagonalization and bosonization techniques indicate that the interplay between dimerization and interaction could result in gapless phases in the regime 0
Role of numerical scheme choice on the results of mathematical modeling of combustion and detonation
NASA Astrophysics Data System (ADS)
Yakovenko, I. S.; Kiverin, A. D.; Pinevich, S. G.; Ivanov, M. F.
2016-11-01
The present study discusses capabilities of dissipation-free CABARET numerical method application to unsteady reactive gasdynamic flows modeling. In framework of present research the method was adopted for reactive flows governed by real gas equation of state and applied for several typical problems of unsteady gas dynamics and combustion modeling such as ignition and detonation initiation by localized energy sources. Solutions were thoroughly analyzed and compared with that derived by using of the modified Euler-Lagrange method of “coarse” particles. Obtained results allowed us to distinguish range of phenomena where artificial effects of numerical approach may counterfeit their physical nature and to develop guidelines for numerical approach selection appropriate for unsteady reactive gasdynamic flows numerical modeling.
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…
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.
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.
1986-01-01
In-space docking and separation maneuvers of spacecraft that have large fluid mass fractions may cause undersirable 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.
Cerbelaud, Manuella; Lestriez, Bernard; Ferrando, Riccardo; Videcoq, Arnaud; Richard-Plouet, Mireille; Caldes, Maria Teresa; Guyomard, Dominique
2014-03-18
Suspensions of carbon blacks and spherical carbon particles are studied experimentally and numerically to understand the role of the particle shape on the tendency to percolation. Two commercial carbon blacks and one lab-synthesized spherical carbon are used. The percolation thresholds in suspensions are experimentally determined by two complementary methods: impedance spectroscopy and rheology. Brownian dynamics simulations are performed to explain the experimental results taking into account the fractal shape of the aggregates in the carbon blacks. The results of Brownian dynamics simulations are in good agreement with the experimental results and allow one to explain the experimental behavior of suspensions.
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…
Guo, Hongsheng; Neill, W. Stuart
2009-02-15
This paper investigates the effects of hydrogen/reformate gas addition on flame temperature and NO formation in strained methane/air diffusion flames by numerical simulation. The results reveal that flame temperature changes due to the combined effects of adiabatic temperature, fuel Lewis number and radiation heat loss, when hydrogen/reformate gas is added to the fuel of a methane/air diffusion flame. The effect of Lewis number causes the flame temperature to increase much faster than the corresponding adiabatic equilibrium temperature when hydrogen is added, and results in a qualitatively different variation from the adiabatic equilibrium temperature as reformate gas is added. At some conditions, the addition of hydrogen results in a super-adiabatic flame temperature. The addition of hydrogen/reformate gas causes NO formation to change because of the variations in flame temperature, structure and NO formation mechanism, and the effect becomes more significant with increasing strain rate. The addition of a small amount of hydrogen or reformate gas has little effect on NO formation at low strain rates, and results in an increase in NO formation at moderate or high strain rates. However, the addition of a large amount of hydrogen increases NO formation at all strain rates, except near pure hydrogen condition. Conversely, the addition of a large amount of reformate gas results in a reduction in NO formation. (author)
Exploring vortex dynamics in the presence of dissipation: Analytical and numerical results
NASA Astrophysics Data System (ADS)
Yan, D.; Carretero-González, R.; Frantzeskakis, D. J.; Kevrekidis, P. G.; Proukakis, N. P.; Spirn, D.
2014-04-01
In this paper, we examine the dynamical properties of vortices in atomic Bose-Einstein condensates in the presence of phenomenological dissipation, used as a basic model for the effect of finite temperatures. In the context of this so-called dissipative Gross-Pitaevskii model, we derive analytical results for the motion of single vortices and, importantly, for vortex dipoles, which have become very relevant experimentally. Our analytical results are shown to compare favorably to the full numerical solution of the dissipative Gross-Pitaevskii equation where appropriate. We also present results on the stability of vortices and vortex dipoles, revealing good agreement between numerical and analytical results for the internal excitation eigenfrequencies, which extends even beyond the regime of validity of this equation for cold atoms.
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
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.
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.
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.
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.
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.
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
Landau-Zener transitions in a dissipative environment: numerically exact results.
Nalbach, P; Thorwart, M
2009-11-27
We study Landau-Zener transitions in a dissipative environment by means of the numerically exact quasiadiabatic propagator path integral. It allows to cover the full range of the involved parameters. We discover a nonmonotonic dependence of the transition probability on the sweep velocity which is explained in terms of a simple phenomenological model. This feature, not captured by perturbative approaches, results from a nontrivial competition between relaxation and the external sweep.
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.
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) and 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.
Raghavan, Narendran; Dehoff, Ryan; Pannala, Sreekanth; ...
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
Numerical results of the shape optimization problem for the insulation barrier
NASA Astrophysics Data System (ADS)
Salač, Petr
2016-12-01
The contribution deals with the numerical results for the shape optimization problem of the system mould, glass piece, plunger, insulation barrier and plunger cavity used in glass forming industry, which was formulated in details at AMEE'15. We used the software FreeFem++ to compute the numerical example for the real vase made from lead crystal glassware of the height 267 [mm] and of the mass 1, 55 [kg]. The plunger and the mould were made from steal, the insulation barrier was made from Murpec with the coefficient of thermal conductivity k = 2, 5 [W/m.K] and the coefficient of heat-transfer between the mould and the environment was chosen to be α = 14 [W/m2.K]. The cooling was implemented by the volume V = 10 [l/min] of water with the temperature 15°C at the entrance and the temperature 100°C at the exit. The results of the numerical optimization to required target temperature 800°C of the outward plunger surface together with the distribution of temperatures on the interface between the plunger and heat source before and after the optimization process are presented.
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
Temperature Fields in Soft Tissue during LPUS Treatment: Numerical Prediction and Experiment Results
NASA Astrophysics Data System (ADS)
Kujawska, Tamara; Wójcik, Janusz; Nowicki, Andrzej
2010-03-01
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/cm2, 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 the
NASA Astrophysics Data System (ADS)
Zemlyanaya, E. V.; Bashashin, M. V.; Rahmonov, I. R.; Shukrinov, Yu. M.; Atanasova, P. Kh.; Volokhova, A. V.
2016-10-01
We consider a model of system of long Josephson junctions (LJJ) with inductive and capacitive coupling. Corresponding system of nonlinear partial differential equations is solved by means of the standard three-point finite-difference approximation in the spatial coordinate and utilizing the Runge-Kutta method for solution of the resulting Cauchy problem. A parallel algorithm is developed and implemented on a basis of the MPI (Message Passing Interface) technology. Effect of the coupling between the JJs on the properties of LJJ system is demonstrated. Numerical results are discussed from the viewpoint of effectiveness of parallel implementation.
Electrostatic modes in dense dusty plasmas with high fugacity: Numerical results
NASA Astrophysics Data System (ADS)
Rao, N. N.
2000-08-01
The existence of ultra low-frequency wave modes in dusty plasmas has been investigated over a wide range of dust fugacity [defined by f≡4πnd0λD2R, where nd0 is the dust number density, λD is the plasma Debye length, and R is the grain size (radius)] and the grain charging frequency (ω1) by numerically solving the dispersion relation obtained from the kinetic (Vlasov) theory. A detailed comparison between the numerical and the analytical results applicable for the tenuous (low fugacity, f≪1), the dilute (medium fugacity, f˜1), and the dense (high fugacity, f≫1) regimes has been carried out. In the long wavelength limit and for frequencies ω≪ω1, the dispersion curves obtained from the numerical solutions of the real as well as the complex (kinetic) dispersion relations agree, both qualitatively and quantitatively, with the analytical expressions derived from the fluid and the kinetic theories, and are thus identified with the ultra low-frequency electrostatic dust modes, namely, the dust-acoustic wave (DAW), the dust charge-density wave (DCDW) and the dust-Coulomb wave (DCW) discussed earlier [N. N. Rao, Phys. Plasmas 6, 4414 (1999); 7, 795 (2000)]. In particular, the analytical scaling between the phase speeds of the DCWs and the DAWs predicted from theoretical considerations, namely, (ω/k)DCW=(ω/k)DAW/√fδ (where δ is the ratio of the charging frequencies) is in excellent agreement with the numerical results. A simple physical picture of the DCWs has been proposed by defining an effective pressure called "Coulomb pressure" as PC≡nd0qd02/R, where qd0 is the grain surface charge. Accordingly, the DCW dispersion relation is given, in the lowest order, by (ω/k)DCW=√PC/ρdδ , where ρd≡nd0md is the dust mass density. Thus, the DCWs which are driven by the Coulomb pressure can be considered as the electrostatic analogue of the hydromagnetic (Alfvén or magnetoacoustic) waves which are driven by the magnetic field pressure. For the frequency
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.
Distribution of Steps with Finite-Range Interactions: Analytic Approximations and Numerical Results
NASA Astrophysics Data System (ADS)
GonzáLez, Diego Luis; Jaramillo, Diego Felipe; TéLlez, Gabriel; Einstein, T. L.
2013-03-01
While most Monte Carlo simulations assume only nearest-neighbor steps interact elastically, most analytic frameworks (especially the generalized Wigner distribution) posit that each step elastically repels all others. In addition to the elastic repulsions, we allow for possible surface-state-mediated interactions. We investigate analytically and numerically how next-nearest neighbor (NNN) interactions and, more generally, interactions out to q'th nearest neighbor alter the form of the terrace-width distribution and of pair correlation functions (i.e. the sum over n'th neighbor distribution functions, which we investigated recently.[2] For physically plausible interactions, we find modest changes when NNN interactions are included and generally negligible changes when more distant interactions are allowed. We discuss methods for extracting from simulated experimental data the characteristic scale-setting terms in assumed potential forms.
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.
Laboratory simulations of lidar returns from clouds - Experimental and numerical results
NASA Astrophysics Data System (ADS)
Zaccanti, Giovanni; Bruscaglioni, Piero; Gurioli, Massimo; Sansoni, Paola
1993-03-01
The experimental results of laboratory simulations of lidar returns from clouds are presented. Measurements were carried out on laboratory-scaled cloud models by using a picosecond laser and a streak-camera system. The turbid structures simulating clouds were suspensions of polystyrene spheres in water. The geometrical situation was similar to that of an actual lidar sounding a cloud 1000 m distant and with a thickness of 300 m. Measurements were repeated for different concentrations and different sizes of spheres. The results show how the effect of multiple scattering depends on the scattering coefficient and on the phase function of the diffusers. The depolarization introduced by multiple scattering was also investigated. The results were also compared with numerical results obtained by Monte Carlo simulations. Substantially good agreement between numerical and experimental results was found. The measurements showed the adequacy of modern electro-optical systems to study the features of multiple-scattering effects on lidar echoes from atmosphere or ocean by means of experiments on well-controlled laboratory-scaled models. This adequacy provides the possibility of studying the influence of different effects in the laboratory in well-controlled situations.
Laboratory simulations of lidar returns from clouds: experimental and numerical results.
Zaccanti, G; Bruscaglioni, P; Gurioli, M; Sansoni, P
1993-03-20
The experimental results of laboratory simulations of lidar returns from clouds are presented. Measurements were carried out on laboratory-scaled cloud models by using a picosecond laser and a streak-camera system. The turbid structures simulating clouds were suspensions of polystyrene spheres in water. The geometrical situation was similar to that of an actual lidar sounding a cloud 1000 m distant and with a thickness of 300 m. Measurements were repeated for different concentrations and different sizes of spheres. The results show how the effect of multiple scattering depends on the scattering coefficient and on the phase function of the diffusers. The depolarization introduced by multiple scattering was also investigated. The results were also compared with numerical results obtained by Monte Carlo simulations. Substantially good agreement between numerical and experimental results was found. The measurements showed the adequacy of modern electro-optical systems to study the features of multiple-scattering effects on lidar echoes from atmosphere or ocean by means of experiments on well-controlled laboratory-scaled models. This adequacy provides the possibility of studying the influence of different effects in the laboratory in well-controlled situations.
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
NASA Astrophysics Data System (ADS)
Janković, I.; Fiori, A.; Dagan, G.
2003-09-01
In parts 1 [, 2003] and 2 [, 2003] a multi-indicator model of heterogeneous formations is devised in order to solve flow and transport in highly heterogeneous formations. The isotropic medium is made up from circular (2-D) or spherical (3-D) inclusions of different conductivities K, submerged in a matrix of effective conductivity. This structure is different from the multi-Gaussian one, even for equal log conductivity distribution and integral scale. A snapshot of a two-dimensional plume in a highly heterogeneous medium of lognormal conductivity distribution shows that the model leads to a complex transport picture. The present study was limited, however, to investigating the statistical moments of ergodic plumes. Two approximate semianalytical solutions, based on a self-consistent model (SC) and on a first-order perturbation in the log conductivity variance (FO), are used in parts 1 and 2 in order to compute the statistical moments of flow and transport variables for a lognormal conductivity pdf. In this paper an efficient and accurate numerical procedure, based on the analytic-element method [, 1989], is used in order to validate the approximate results. The solution satisfies exactly the continuity equation and at high-accuracy the continuity of heads at inclusion boundaries. The dimensionless dependent variables depend on two parameters: the volume fraction n of inclusions in the medium and the log conductivity variance σY2. For inclusions of uniform radius, the largest n was 0.9 (2-D) and 0.7 (3-D), whereas the largest σY2 was equal to 10. The SC approximation underestimates the longitudinal Eulerian velocity variance for increasing n and increasing σY2 in 2-D and, to a lesser extent, in 3-D, as compared to numerical results. The FO approximation overestimates these variances, and these effects are larger in the transverse direction. The longitudinal velocity pdf is highly skewed and negative velocities are present at high σY2, especially in 2-D. The main
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.
Velocity distribution of meteoroids colliding with planets and satellites. II. Numerical results
NASA Astrophysics Data System (ADS)
Kholshevnikov, K. V.; Shor, V. A.
In the first part of the paper we proposed algorithm for describing velocity distribution of meteoroids colliding with planets and satellites. In the present part we show numerical characteristics of the distribution function. Namely, for each of terrestrial planets and their satellites we consider a swarm of encountering particles of asteroidal origin. They form a field of relative collisional velocities v. We consider momenta k (mathematical expectation of vk), k = -1, 1, 2, 3, 4. The data are calculated under two different assumptions: taking into account gravitation of target body or without it. The main results are presented in a series of tables each containing five numbers and several useful functions of them.
Effect of product form upon fatigue-crack growth behavior in Alloy 718: additional results
James, L A
1980-08-01
A previous study had characterized the fatigue-crack growth behavior of four wrought product forms (sheet, plate, bar and forging) from a single heat of Alloy 718 and concluded that there were no consistent trends in the crack growth rate results that could be attributed to product form variability. The present study adds one additional product form (gas-tungsten-arc weldments) from the same heat, and compares the behavior to that exhibited by the wrought product forms. Two different precipitation heat-treatments were employed at each of five test temperatures (24, 316, 427, 538, and 649{sup 0}C).
The effect of product form upon fatigue-crack growth behavior in Alloy 718: Additional results
James, L.A.
1980-08-01
A previous study had characterized the fatigue-crack growth behavior of four wrought product forms (sheet, plate, bar and forging) from a single heat of Alloy 718 and concluded that there were no consistent trends in the crack growth rate results that could be attributed to product form variability. The present study adds one additional product form (gas-tungsten-arc weldments) from the same heat, and compares the behavior to that exhibited by the wrought product forms. Two different precipitation heat-treatments were employed at each of five test temperatures. 11 refs., 5 figs., 3 tabs.
NASA Astrophysics Data System (ADS)
Sultanov, Albert H.; Gayfulin, Renat R.; Vinogradova, Irina L.
2008-04-01
Fiber optic telecommunication systems with duplex data transmitting over single fiber require reflection minimization. Moreover reflections may be so high that causes system deactivating by misoperation of conventional alarm, and system can not automatically adjudge the collision, so operator manual control is required. In this paper we proposed technical solution of mentioned problem based on additional analysis subsystem, realized on the installed Ufa-city fiber optic CTV system "Crystal". Experience of it's maintenance and results of investigations of the fault tolerance parameters are represented
Propagation of CMEs in the interplanetary medium: Numerical and analytical results
NASA Astrophysics Data System (ADS)
González-Esparza, J. A.; Cantó, J.; González, R. F.; Lara, A.; Raga, A. C.
2003-08-01
We study the propagation of coronal mass ejections (CMES) from near the Sun to 1 AU by comparing results from two different models: a 1-D, hydrodynamic, single-fluid, numerical model (González-Esparza et al., 2003a) and an analytical model to study the dynamical evolution of supersonic velocity's fluctuations at the base of the solar wind applied to the propagation of CMES (Cantó et al., 2002). Both models predict that a fast CME moves initially in the inner heliosphere with a quasi-constant velocity (which has an intermediate value between the initial CME velocity and the ambient solar wind velocity ahead) until a 'critical distance' at which the CME velocity begins to decelerate approaching to the ambient solar wind velocity. This critical distance depends on the characteristics of the CME (initial velocity, density and temperature) as well as of the ambient solar wind. Given typical parameters based on observations, this critical distance can vary from 0.3 to beyond 1 AU from the Sun. These results explain the radial evolution of the velocity of fast CMEs in the inner heliosphere inferred from interplanetary scintillation (IPS) observations (Manoharan et al., 2001, 2003, Tokumaru et al., 2003). On the other hand, the numerical results show that a fast CME and its associated interplanetary (IP) shock follow different heliocentric evolutions: the IP shock always propagates faster than its CME driver and the latter begins to decelerate well before the shock.
NASA Astrophysics Data System (ADS)
Liu, Xin; Ben-Zion, Yehuda
2013-09-01
We study analytically and numerically effects of attenuation on cross-correlation functions of ambient noise in a 2-D model with different attenuation constants between and outside a pair of stations. The attenuation is accounted for by quality factor Q(ω) and complex phase velocity. The analytical results are derived for isotropic far-field source distribution assuming the Fresnel approximation and mild attenuation. More general situations including cases with non-isotropic source distributions are examined with numerical simulations. The results show that homogeneous attenuation in the interstation regions produces symmetric amplitude decay of the causal and anticausal parts of the noise cross-correlation function. The attenuation between the receivers and far-field sources generates symmetric exponential amplitude decay and may also cause asymmetric reduction of the causal/anticausal parts that increases with frequency. This frequency dependence can be used to distinguish asymmetric amplitudes due to attenuation from frequency-independent asymmetry in noise correlations generated by non-isotropic source distribution. The attenuations both between and outside station pairs also produce phase shifts that could affect measurements of group and phase velocities. In terms of noise cross-spectra, the interstation attenuation is governed by Struve functions while the attenuation between the far-field sources and receivers is associated with exponential decay and the imaginary part of complex Bessel function. These results are fundamentally different from previous studies of attenuated coherency that append the Bessel function with an exponential decay that depends on the interstation distance.
Silk-Eglit, Graham M; Stenclik, Jessica H; Miele, Andrea S; Lynch, Julie K; McCaffrey, Robert J
2015-01-01
Several studies have documented improvements in the classification accuracy of performance validity tests (PVTs) when they are combined to form aggregated models. Fewer studies have evaluated the impact of aggregating additional PVTs and changing the classification threshold within these models. A recent Monte Carlo simulation demonstrated that to maintain a false-positive rate (FPR) of ≤.10, only 1, 4, 8, 10, and 15 PVTs should be analyzed at classification thresholds of failing at least 1, at least 2, at least 3, at least 4, and at least 5 PVTs, respectively. The current study sought to evaluate these findings with embedded PVTs in a sample of real-life litigants and to highlight a potential danger in analytic flexibility with embedded PVTs. Results demonstrated that to maintain an FPR of ≤.10, only 3, 7, 10, 14, and 15 PVTs should be analyzed at classification thresholds of failing at least 1, at least 2, at least 3, at least 4, and at least 5 PVTs, respectively. Analyzing more than these numbers of PVTs resulted in a dramatic increase in the FPR. In addition, in the most extreme case, flexibility in analyzing and reporting embedded PVTs increased the FPR by 67%. Given these findings, a more objective approach to analyzing and reporting embedded PVTs should be introduced.
Swinging Atwood Machine: Experimental and numerical results, and a theoretical study
NASA Astrophysics Data System (ADS)
Pujol, O.; Pérez, J. P.; Ramis, J. P.; Simó, C.; Simon, S.; Weil, J. A.
2010-06-01
A Swinging Atwood Machine ( SAM) is built and some experimental results concerning its dynamic behaviour are presented. Experiments clearly show that pulleys play a role in the motion of the pendulum, since they can rotate and have non-negligible radii and masses. Equations of motion must therefore take into account the moment of inertia of the pulleys, as well as the winding of the rope around them. Their influence is compared to previous studies. A preliminary discussion of the role of dissipation is included. The theoretical behaviour of the system with pulleys is illustrated numerically, and the relevance of different parameters is highlighted. Finally, the integrability of the dynamic system is studied, the main result being that the machine with pulleys is non-integrable. The status of the results on integrability of the pulley-less machine is also recalled.
NASA Astrophysics Data System (ADS)
Fossum, Kristian; Mannseth, Trond
2014-11-01
We assess and compare parameter sampling capabilities of one sequential and one simultaneous Bayesian, ensemble-based, joint state-parameter (JS) estimation method. In the companion paper, part I (Fossum and Mannseth 2014 Inverse Problems 30 114002), analytical investigations lead us to propose three claims, essentially stating that the sequential method can be expected to outperform the simultaneous method for weakly nonlinear forward models. Here, we assess the reliability and robustness of these claims through statistical analysis of results from a range of numerical experiments. Samples generated by the two approximate JS methods are compared to samples from the posterior distribution generated by a Markov chain Monte Carlo method, using four approximate measures of distance between probability distributions. Forward-model nonlinearity is assessed from a stochastic nonlinearity measure allowing for sufficiently large model dimensions. Both toy models (with low computational complexity, and where the nonlinearity is fairly easy to control) and two-phase porous-media flow models (corresponding to down-scaled versions of problems to which the JS methods have been frequently applied recently) are considered in the numerical experiments. Results from the statistical analysis show strong support of all three claims stated in part I.
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.
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.
Fernandes, Henrique; Zhang, Hai; Figueiredo, Alisson; Ibarra-Castanedo, Clemente; Guimarares, Gilmar; Maldague, Xavier
2016-12-01
Composite materials are widely used in the aeronautic industry. One of the reasons is because they have strength and stiffness comparable to metals, with the added advantage of significant weight reduction. Infrared thermography (IT) is a safe nondestructive testing technique that has a fast inspection rate. In active IT, an external heat source is used to stimulate the material being inspected in order to generate a thermal contrast between the feature of interest and the background. In this paper, carbon-fiber-reinforced polymers are inspected using IT. More specifically, carbon/PEEK (polyether ether ketone) laminates with square Kapton inserts of different sizes and at different depths are tested with three different IT techniques: pulsed thermography, vibrothermography, and line scan thermography. The finite element method is used to simulate the pulsed thermography experiment. Numerical results displayed a very good agreement with experimental results.
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)
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.
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.
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)
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 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.
Numerical simulation and experimental results of filament wound CFRP tubes tested under biaxial load
NASA Astrophysics Data System (ADS)
Amaldi, A.; Giannuzzi, M.; Marchetti, M.; Miliozzi, A.
1992-10-01
The analysis of angle ply carbon/epoxy laminated composites when subjected to uniaxial and biaxial stresses is presented. Three classes of interwoven pattern filament wound cylindrical specimens are studied in order to compare the influence of angle on the mechanical behavior of the laminate. Three dimensional finite element and thin shell analyses were first applied to the problem in order to predict global elastic behavior of specimens subjected to uniaxial loads. Different failure criteria were then adopted to investigate specimens' failure and experimental tests were carried out for a comparison with numerical results. Biaxial stress conditions were produced by applying combinations of internal pressure and axial tensile and compressive loads to the specimens.
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.
Marom, Gil; Bluestein, Danny
2016-01-01
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.
Marom, Gil; Bluestein, Danny
2016-01-01
Summary 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
Interacting steps with finite-range interactions: Analytical approximation and numerical results
NASA Astrophysics Data System (ADS)
Jaramillo, Diego Felipe; Téllez, Gabriel; González, Diego Luis; Einstein, T. L.
2013-05-01
We calculate an analytical expression for the terrace-width distribution P(s) for an interacting step system with nearest- and next-nearest-neighbor interactions. Our model is derived by mapping the step system onto a statistically equivalent one-dimensional system of classical particles. The validity of the model is tested with several numerical simulations and experimental results. We explore the effect of the range of interactions q on the functional form of the terrace-width distribution and pair correlation functions. For physically plausible interactions, we find modest changes when next-nearest neighbor interactions are included and generally negligible changes when more distant interactions are allowed. We discuss methods for extracting from simulated experimental data the characteristic scale-setting terms in assumed potential forms.
Ultimate tensile strength of embedded I-sections: a comparison of experimental and numerical results
NASA Astrophysics Data System (ADS)
Heristchian, Mahmoud; Pourakbar, Pouyan; Imeni, Saeed; Ramezani, M. Reza Adib
2014-12-01
Exposed baseplates together with anchor bolts are the customary method of connection of steel structures to the concrete footings. Post-Kobe studies revealed that the embedded column bases respond better to the earthquake uplift forces. The embedded column bases also, offer higher freedom in achieving the required strength, rigidity and ductility. The paper presents the results of the pullout failure of three embedded IPE140 sections, tested under different conditions. The numerical models are then, generated in Abaqus 6.10-1 software. It is concluded that, the steel profiles could be directly anchored in concrete without using anchor bolts as practiced in the exposed conventional column bases. Such embedded column bases can develop the required resistance against pullout forces at lower constructional costs.
NASA Astrophysics Data System (ADS)
Wang, Bin; Popescu, Radu; Prevost, Jean H.
2004-08-01
Owing to imperfect boundary conditions in laboratory soil tests and the possibility of water diffusion inside the soil specimen in undrained tests, the assumption of uniform stress/strain over the sample is not valid. This study presents a qualitative assessment of the effects of non-uniformities in stresses and strains, as well as effects of water diffusion within the soil sample on the global results of undrained cyclic simple shear tests. The possible implications of those phenomena on the results of liquefaction strength assessment are also discussed. A state-of-the-art finite element code for transient analysis of multi-phase systems is used to compare results of the so-called element tests (numerical constitutive experiments assuming uniform stress/strain/pore pressure distribution throughout the sample) with results of actual simulations of undrained cyclic simple shear tests using a finite element mesh and realistic boundary conditions. The finite element simulations are performed under various conditions, covering the entire range of practical situations: (1) perfectly drained soil specimen with constant volume, (2) perfectly undrained specimen, and (3) undrained test with possibility of water diffusion within the sample. The results presented here are restricted to strain-driven tests performed for a loose uniform fine sand with relative density Dr=40%. Effects of system compliance in undrained laboratory simple shear tests are not investigated here. Copyright
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.
Bragg's rule of stopping power additivity: a compilation and summary of results
Thwaites, D.I.
1983-09-01
Stopping power additivity, as expressed by Bragg's rule, is an important concept in many practical situations involving charged particles. Its validity has been investigated in a large number of studies and the wide range of data is confusing and at times conflicting. No previous comprehensive survey of the data has been undertaken. Thus a compilation is attempted here of a hundred or so papers which have included tests of Bragg's rule. Their main results are indicated and a summary is given of the effects of chemical binding and phase on the stopping power of heavy charged particles. Such effects are confirmed on the evidence available. Chemical binding effects become more significant for materials containing low-Z constituents and as energy falls into and through the transition region. Deviations of up to 50% have been observed in atomic stopping cross sections extracted from measurements on hydrocarbons. There is still some conflicting evidence appearing on phase effects. However, in general a broad consensus is emerging indicating significant differences in H/sub 2/O and organic and similar materials. Stopping cross sections in the vapor phase are greater by up to approx. 5 or 10% at energies around those of the stopping power maximum for protons and He ions. The effects decrease as energy increases.
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)
EPA Update on Gold King Mine Response: Additional Data Results and Public Records
WASHINGTON - Today the U.S. Environmental Protection Agency (EPA) released an update on water quality and sediment data for the Animas and San Juan Rivers, as well as additional public records on the Gold King Mine response.
Atom-probe tomography of tribological boundary films resulting from boron-based oil additives
Kim, Yoon-Jun; Baik, Sung-Il; Bertolucci-Coelho, Leonardo; Mazzaferro, Lucca; Ramirez, Giovanni; Erdemir, Ali; Seidman, D K
2016-01-15
Correlative characterization using atom-probe tomography (APT) and transmission electron microscopy (TEM) was performed on a tribofilm formed during sliding frictional testing with a fully formulated engine oil, which also contains a boron-based additive. The tribofilm formed is ~15 nm thick and consists of oxides of iron and compounds of B, Ca, P, and S, which are present in the additive. This study provides strong evidence for boron being embedded in the tribofilm, which effectively reduces friction and wear losses.
Eschen, René; Müller-Schärer, Heinz; Schaffner, Urs
2013-01-01
Soil nutrient availability and colonization by arbuscular mycorrhizal fungi are important and potentially interacting factors shaping vegetation composition and succession. We investigated the effect of carbon (C) addition, aimed at reducing soil nutrient availability, on arbuscular mycorrhizal colonization. Seedlings of 27 plant species with different sets of life-history traits (functional group affiliation, life history strategy and nitrophilic status) were grown in pots filled with soil from a nutrient-rich set-aside field and amended with different amounts of C. Mycorrhizal colonization was progressively reduced along the gradient of increasing C addition in 17 out of 27 species, but not in the remaining species. Grasses had lower colonization levels than forbs and legumes and the decline in AM fungal colonization was more pronounced in legumes than in other forbs and grasses. Mycorrhizal colonization did not differ between annual and perennial species, but decreased more rapidly along the gradient of increasing C addition in plants with high Ellenberg N values than in plants with low Ellenberg N values. Soil C addition not only limits plant growth through a reduction in available nutrients, but also reduces mycorrhizal colonization of plant roots. The effect of C addition on mycorrhizal colonization varies among plant functional groups, with legumes experiencing an overproportional reduction in AM fungal colonization along the gradient of increasing C addition. We therefore propose that for a better understanding of vegetation succession on set-aside fields one may consider the interrelationship between plant growth, soil nutrient availability and mycorrhizal colonization of plant roots.
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
NASA Astrophysics Data System (ADS)
Beniaiche, Ahmed; Ghenaiet, Adel; Carcasci, Carlo; Facchini, Bruno
2017-02-01
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.
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.
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)
Klapp, J.; Cervantes-Cota, J.; Chauvet, P.
1990-11-01
RESUMEN. A nivel cosmol6gico pensamos que se ha estado prodticiendo radiaci6n gravitacional en cantidades considerables dentro de las galaxias. Si los eventos prodnctores de radiaci6n gravitatoria han venido ocurriendo desde Ia epoca de Ia formaci6n de las galaxias, cuando menos, sus efectos cosmol6gicos pueden ser tomados en cuenta con simplicidad y elegancia al representar la producci6n de radiaci6n y, por consiguiente, su interacci6n con materia ordinaria fenomenol6gicamente a trave's de una ecuaci6n de estado politr6pica, como lo hemos mostrado en otros trabajos. Presentamos en este articulo resultados nunericos de este modelo. ABSTRACT A common believe in cosmology is that gravitational radiation in considerable quantities is being produced within the galaxies. Ifgravitational radiation production has been running since the galaxy formation epoch, at least, its cosmological effects can be assesed with simplicity and elegance by representing the production of radiation and, therefore, its interaction with ordinary matter phenomenologically through a polytropic equation of state as shown already elsewhere. We present in this paper the numerical results of such a model. K words: COSMOLOGY - GRAVITATION
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
ERIC Educational Resources Information Center
Romberg, Thomas A.; And Others
The purpose of this study was to relate children's cognitive processing capabilities and their grade level to their performance and to the strategies they used when working addition and subtraction problems. From two sets of data which assessed memory capacity and cognitive processing capacities, six groups of children with different cognitive…
Code of Federal Regulations, 2012 CFR
2012-04-01
... 21 Food and Drugs 6 2012-04-01 2012-04-01 false Indirect food additives resulting from packaging..., 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
... 21 Food and Drugs 6 2013-04-01 2013-04-01 false Indirect food additives resulting from packaging..., 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, 2012 CFR
2012-04-01
... 21 Food and Drugs 6 2012-04-01 2012-04-01 false Indirect food additives resulting from packaging materials prior sanctioned for animal feed and pet food. 570.13 Section 570.13 Food and Drugs FOOD AND DRUG... FOOD ADDITIVES General Provisions § 570.13 Indirect food additives resulting from packaging...
Code of Federal Regulations, 2014 CFR
2014-04-01
... 21 Food and Drugs 6 2014-04-01 2014-04-01 false Indirect food additives resulting from packaging..., 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
... 21 Food and Drugs 6 2013-04-01 2013-04-01 false Indirect food additives resulting from packaging materials prior sanctioned for animal feed and pet food. 570.13 Section 570.13 Food and Drugs FOOD AND DRUG... FOOD ADDITIVES General Provisions § 570.13 Indirect food additives resulting from packaging...
Code of Federal Regulations, 2014 CFR
2014-04-01
... 21 Food and Drugs 6 2014-04-01 2014-04-01 false Indirect food additives resulting from packaging materials prior sanctioned for animal feed and pet food. 570.13 Section 570.13 Food and Drugs FOOD AND DRUG... FOOD ADDITIVES General Provisions § 570.13 Indirect food additives resulting from packaging...
The vertical age profile in sea ice: Theory and numerical results
NASA Astrophysics Data System (ADS)
Lietaer, Olivier; Deleersnijder, Eric; Fichefet, Thierry; Vancoppenolle, Martin; Comblen, Richard; Bouillon, Sylvain; Legat, Vincent
The sea ice age is an interesting diagnostic tool because it may provide a proxy for the sea ice thickness and is easier to infer from observations than the sea ice thickness. Remote sensing algorithms and modeling approaches proposed in the literature indicate significant methodological uncertainties, leading to different ice age values and physical interpretations. In this work, we focus on the vertical age distribution in sea ice. Based on the age theory developed for marine modeling, we propose a vertically-variable sea ice age definition which gives a measure of the time elapsed since the accretion of the ice particle under consideration. An analytical solution is derived from Stefan's law for a horizontally homogeneous ice layer with a periodic ice thickness seasonal cycle. Two numerical methods to solve the age equation are proposed. In the first one, the domain is discretized adaptively in space thanks to Lagrangian particles in order to capture the age profile and its discontinuities. The second one focuses on the mean age of the ice using as few degrees of freedom as possible and is based on an Arbitrary Lagrangian-Eulerian (ALE) spatial discretization and the finite element method. We observe an excellent agreement between the Lagrangian particles and the analytical solution. The mean value and the standard deviation of the finite element solution agree with the analytical solution and a linear approximation is found to represent the age profile the better, the older the ice gets. Both methods are finally applied to a stand-alone thermodynamic sea ice model of the Arctic. Computing the vertically-averaged ice age reduces by a factor of about 2 the simulated ice age compared to the oldest particle of the ice columns. A high correlation is found between the ice thickness and the age of the oldest particle. However, whether or not this will remain valid once ice dynamics is included should be investigated. In addition, the present study, based on
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.
Numerical and experimental results on the spectral wave transfer in finite depth
NASA Astrophysics Data System (ADS)
Benassai, Guido
2016-04-01
Determination of the form of the one-dimensional surface gravity wave spectrum in water of finite depth is important for many scientific and engineering applications. Spectral parameters of deep water and intermediate depth waves serve as input data for the design of all coastal structures and for the description of many coastal processes. Moreover, the wave spectra are given as an input for the response and seakeeping calculations of high speed vessels in extreme sea conditions and for reliable calculations of the amount of energy to be extracted by wave energy converters (WEC). Available data on finite depth spectral form is generally extrapolated from parametric forms applicable in deep water (e.g., JONSWAP) [Hasselmann et al., 1973; Mitsuyasu et al., 1980; Kahma, 1981; Donelan et al., 1992; Zakharov, 2005). The present paper gives a contribution in this field through the validation of the offshore energy spectra transfer from given spectral forms through the measurement of inshore wave heights and spectra. The wave spectra on deep water were recorded offshore Ponza by the Wave Measurement Network (Piscopia et al.,2002). The field regressions between the spectral parameters, fp and the nondimensional energy with the fetch length were evaluated for fetch-limited sea conditions. These regressions gave the values of the spectral parameters for the site of interest. The offshore wave spectra were transfered from the measurement station offshore Ponza to a site located offshore the Gulf of Salerno. The offshore local wave spectra so obtained were transfered on the coastline with the TMA model (Bouws et al., 1985). Finally the numerical results, in terms of significant wave heights, were compared with the wave data recorded by a meteo-oceanographic station owned by Naples Hydrographic Office on the coastline of Salerno in 9m depth. Some considerations about the wave energy to be potentially extracted by Wave Energy Converters were done and the results were discussed.
Numerical results on noise-induced dynamics in the subthreshold regime for thermoacoustic systems
NASA Astrophysics Data System (ADS)
Gupta, Vikrant; Saurabh, Aditya; Paschereit, Christian Oliver; Kabiraj, Lipika
2017-03-01
Thermoacoustic instability is a serious issue in practical combustion systems. Such systems are inherently noisy, and hence the influence of noise on the dynamics of thermoacoustic instability is an aspect of practical importance. The present work is motivated by a recent report on the experimental observation of coherence resonance, or noise-induced coherence with a resonance-like dependence on the noise intensity as the system approaches the stability margin, for a prototypical premixed laminar flame combustor (Kabiraj et al., Phys. Rev. E, 4 (2015)). We numerically investigate representative thermoacoustic models for such noise-induced dynamics. Similar to the experiments, we study variation in system dynamics in response to variations in the noise intensity and in a critical control parameter as the systems approach their stability margins. The qualitative match identified between experimental results and observations in the representative models investigated here confirms that coherence resonance is a feature of thermoacoustic systems. We also extend the experimental results, which were limited to the case of subcritical Hopf bifurcation, to the case of supercritical Hopf bifurcation. We identify that the phenomenon has qualitative differences for the systems undergoing transition via subcritical and supercritical Hopf bifurcations. Two important practical implications are associated with the findings. Firstly, the increase in noise-induced coherence as the system approaches the onset of thermoacoustic instability can be considered as a precursor to the instability. Secondly, the dependence of noise-induced dynamics on the bifurcation type can be utilised to distinguish between subcritical and supercritical bifurcation prior to the onset of the instability.
Preliminary result on the enhancement of Ufer electrodes using recycle additives materials
NASA Astrophysics Data System (ADS)
Zulkifli, Muhammad Haziq Aniq Bin; Ahmad, Hussein Bin
2016-11-01
Ground building pillars is to be used as ground rod. The pillars are design, fabricated, and formulated with new ground fillers. The additives will be used from recycle waste materials mainly from the palm oil plant process. Micro scale building pillars will be fabricated and install in the test ground at all of the location. Earth tester meter are used to measure and collect the data of the soil resistivity when the research is conducted. In collecting these data, 3-terminal methods are used to carry the measurements. This experiment will be conducted for 30 weeks and regular measurements at the test ground copper grids will be conducted to measure the ground electrode resistance. The study will mainly base on IEC 62503-3. The used of reinforcing rods and mixture of recycle additives could produce a better grounding system that are suitable and can be used in all kind of soil condition and large industries.
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
NASA Astrophysics Data System (ADS)
Aguiar, P.; González-Castaño, D. M.; Gómez, F.; Pardo-Montero, J.
2014-10-01
Liquid-filled ionisation chambers (LICs) are used in radiotherapy for dosimetry and quality assurance. Volume recombination can be quite important in LICs for moderate dose rates, causing non-linearities in the dose rate response of these detectors, and needs to be corrected for. This effect is usually described with Greening and Boag models for continuous and pulsed radiation respectively. Such models assume that the charge is carried by two different species, positive and negative ions, each of those species with a given mobility. However, LICs operating in non-ultrapure mode can contain different types of electronegative impurities with different mobilities, thus increasing the number of different charge carriers. If this is the case, Greening and Boag models can be no longer valid and need to be reformulated. In this work we present a theoretical and numerical study of volume recombination in parallel-plate LICs with multiple charge carrier species, extending Boag and Greening models. Results from a recent publication that reported three different mobilities in an isooctane-filled LIC have been used to study the effect of extra carrier species on recombination. We have found that in pulsed beams the inclusion of extra mobilities does not affect volume recombination much, a behaviour that was expected because Boag formula for charge collection efficiency does not depend on the mobilities of the charge carriers if the Debye relationship between mobilities and recombination constant holds. This is not the case in continuous radiation, where the presence of extra charge carrier species significantly affects the amount of volume recombination.
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).
Reinforcing mechanism of anchors in slopes: a numerical comparison of results of LEM and FEM
NASA Astrophysics Data System (ADS)
Cai, Fei; Ugai, Keizo
2003-06-01
This paper reports the limitation of the conventional Bishop's simplified method to calculate the safety factor of slopes stabilized with anchors, and proposes a new approach to considering the reinforcing effect of anchors on the safety factor. The reinforcing effect of anchors can be explained using an additional shearing resistance on the slip surface. A three-dimensional shear strength reduction finite element method (SSRFEM), where soil-anchor interactions were simulated by three-dimensional zero-thickness elasto-plastic interface elements, was used to calculate the safety factor of slopes stabilized with anchors to verify the reinforcing mechanism of anchors. The results of SSRFEM were compared with those of the conventional and proposed approaches for Bishop's simplified method for various orientations, positions, and spacings of anchors, and shear strengths of soil-grouted body interfaces. For the safety factor, the proposed approach compared better with SSRFEM than the conventional approach. The additional shearing resistance can explain the influence of the orientation, position, and spacing of anchors, and the shear strength of soil-grouted body interfaces on the safety factor of slopes stabilized with anchors.
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
Water-waves on linear shear currents. A comparison of experimental and numerical results.
NASA Astrophysics Data System (ADS)
Simon, Bruno; Seez, William; Touboul, Julien; Rey, Vincent; Abid, Malek; Kharif, Christian
2016-04-01
Propagation of water waves can be described for uniformly sheared current conditions. Indeed, some mathematical simplifications remain applicable in the study of waves whether there is no current or a linearly sheared current. However, the widespread use of mathematical wave theories including shear has rarely been backed by experimental studies of such flows. New experimental and numerical methods were both recently developed to study wave current interactions for constant vorticity. On one hand, the numerical code can simulate, in two dimensions, arbitrary non-linear waves. On the other hand, the experimental methods can be used to generate waves with various shear conditions. Taking advantage of the simplicity of the experimental protocol and versatility of the numerical code, comparisons between experimental and numerical data are discussed and compared with linear theory for validation of the methods. ACKNOWLEDGEMENTS The DGA (Direction Générale de l'Armement, France) is acknowledged for its financial support through the ANR grant N° ANR-13-ASTR-0007.
Numerical Predictions and Experimental Results of Air Flow in a Smooth Quarter-Scale Nacelle
BLACK, AMALIA R.; SUO-ANTTILA, JILL M.; GRITZO, LOUIS A.; DISIMILE, PETER J.; TUCKER, JAMES R.
2002-06-01
Fires in aircraft engine nacelles must be rapidly suppressed to avoid loss of life and property. The design of new and retrofit suppression systems has become significantly more challenging due to the ban on production of Halon 1301 for environmental concerns. Since fire dynamics and the transport of suppressants within the nacelle are both largely determined by the available air flow, efforts to define systems using less effective suppressants greatly benefit from characterization of nacelle air flow fields. A combined experimental and computational study of nacelle air flow therefore has been initiated. Calculations have been performed using both CFD-ACE (a Computational Fluid Dynamics (CFD) model with a body-fitted coordinate grid) and WLCAN (a CFD-based fire field model with a Cartesian ''brick'' shaped grid). The flow conditions examined in this study correspond to the same Reynolds number as test data from the full-scale nacelle simulator at the 46 Test Wing. Pre-test simulations of a quarter-scale test fixture were performed using CFD-ACE and WLCAN prior to fabrication. Based on these pre-test simulations, a quarter-scale test fixture was designed and fabricated for the purpose of obtaining spatially-resolved measurements of velocity and turbulence intensity in a smooth nacelle. Post-test calculations have been performed for the conditions of the experiment and compared with experimental results obtained from the quarter-scale test fixture. In addition, several different simulations were performed to assess the sensitivity of the predictions to the grid size, to the turbulence models, and to the use of wall functions. In general, the velocity predictions show very good agreement with the data in the center of the channel but deviate near the walls. The turbulence intensity results tend to amplify the differences in velocity, although most of the trends are in agreement. In addition, there were some differences between WLCAN and CFD-ACE results in the angled
Additional results on 'Reducing geometric dilution of precision using ridge regression'
NASA Astrophysics Data System (ADS)
Kelly, Robert J.
1990-07-01
Kelly (1990) presented preliminary results on the feasibility of using ridge regression (RR) to reduce the effects of geometric dilution of precision (GDOP) error inflation in position-fix navigation systems. Recent results indicate that RR will not reduce GDOP bias inflation when biaslike measurement errors last much longer than the aircraft guidance-loop response time. This conclusion precludes the use of RR on navigation systems whose dominant error sources are biaslike; e.g., the GPS selective-availability error source. The simulation results given by Kelly are, however, valid for the conditions defined. Although RR has not yielded a satisfactory solution to the general GDOP problem, it has illuminated the role that multicollinearity plays in navigation signal processors such as the Kalman filter. Bias inflation, initial position guess errors, ridge-parameter selection methodology, and the recursive ridge filter are discussed.
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.
Montague, Timothy H; Potvin, Diane; Diliberti, Charles E; Hauck, Walter W; Parr, Alan F; Schuirmann, Donald J
2012-01-01
In 2008, this group published a paper on approaches for two-stage crossover bioequivalence (BE) studies that allowed for the reestimation of the second-stage sample size based on the variance estimated from the first-stage results. The sequential methods considered used an assumed GMR of 0.95 as part of the method for determining power and sample size. This note adds results for an assumed GMR = 0.90. Two of the methods recommended for GMR = 0.95 in the earlier paper have some unacceptable increases in Type I error rate when the GMR is changed to 0.90. If a sponsor wants to assume 0.90 for the GMR, Method D is recommended. Copyright © 2011 John Wiley & Sons, Ltd.
Experimental and numerical results on a shear layer excited by a sound pulse
NASA Technical Reports Server (NTRS)
Maestrello, L.; Bayliss, A.; Turkel, E.
1979-01-01
The behavior of a sound in a jet was investigated. It is verified that the far-field acoustic power increased with flow velocity for the lower and medium frequency range. Experimentally, an attenuation at higher frequencies is also observed. This increase is found numerically to be due primarily to the interactions between the mean vorticity and the fluctuation velocities. Spectral decomposition of the real time data indicates that the power increase occurs in the low and middle frequency range, where the local instability waves have the largest spatial growth rate. The connection between this amplification and the local instability waves is discussed.
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.
Hansson, Kenny M; Björkqvist, Jenny; Deinum, Johanna
2014-12-01
In the activated partial thromboplastin time (APTT) assay, a variety of nonphysiological reagents is used to induce contact activation. The sensitivity of the APTT response for different thrombin inhibitors has previously been found to be dependent on the used reagent. Recently, infusion of prothrombin (FII) has been used in in-vivo coagulopathy models and its effect has been analyzed in different assays. Therefore, we investigated whether the FII plasma concentration might affect APTT using different commercial reagents, applying both turbidimetry and viscometry. We compared both plasma-derived human FII (pd-hFII) and recombinant human FII (r-hFII). Similar results were found for pd-hFII and r-hFII with different APTT reagents. As expected, no effect on APTT was found by increasing the plasma concentration of FII using APTT reagents consisting of ellagic acid (Actin FS or Actin). Although with Pathromtin SL, consisting of SiO2, only a slight increase was found, with most other commercial APTT reagents, consisting of SiO2 or kaolin, APTT dose-dependently increased by increasing concentration of FII. Therefore, both Pathromtin SL and Actin FS were used to compare r-hFII and pd-hFII by determining the KM at 37C using FII-depleted plasma, providing values of 6 ± 0.3 nmol/l FII for both. Thus, at normal plasma concentrations of FII, the maximal initial thrombin generation rate should be reached and no effect on the coagulation time is expected at higher FII concentrations. To completely avoid the paradoxical effect in the APTT assay at FII concentrations higher than normal, Actin or Actin FS is the preferable reagent.
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.
Nonlinear instability and chaos in plasma wave-wave interactions. II. Numerical methods and results
Kueny, C.S.; Morrison, P.J.
1995-05-01
In Part I of this work and Physics of Plasmas, June 1995, the behavior of linearly stable, integrable systems of waves in a simple plasma model was described using a Hamiltonian formulation. It was shown that explosive instability arises from nonlinear coupling between modes of positive and negative energy, with well-defined threshold amplitudes depending on the physical parameters. In this concluding paper, the nonintegrable case is treated numerically. Several sets of waves are considered, comprising systems of two and three degrees of freedom. The time evolution is modelled with an explicit symplectic integration algorithm derived using Lie algebraic methods. When initial wave amplitudes are large enough to support two-wave decay interactions, strongly chaotic motion destroys the separatrix bounding the stable region for explosive triplets. Phase space orbits then experience diffusive growth to amplitudes that are sufficient for explosive instability, thus effectively reducing the threshold amplitude. For initial amplitudes too small to drive decay instability, small perturbations might still grow to arbitrary size via Arnold diffusion. Numerical experiments do not show diffusion in this case, although the actual diffusion rate is probably underestimated due to the simplicity of the model.
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.
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.
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 Technical Reports Server (NTRS)
Kessinger, C. J.; Wilson, J. W.; Weisman, M.; Klemp, J.
1984-01-01
Data from three NCAR radars are used in both single and dual Doppler analyses to trace the evolution of a June 30, 1982 Colorado convective storm containing downburst-type winds and strong vortices 1-2 km in diameter. The analyses show that a series of small circulations formed along a persistent cyclonic shear boundary; at times as many as three misocyclones were present with vertical vorticity values as large as 0.1/s using a 0.25 km grid interval. The strength of the circulations suggests the possibility of accompanying tornadoes or funnels, although none were observed. Dual-Doppler analyses show that strong, small-scale downdrafts develop in close proximity to the misocyclones. A midlevel mesocyclone formed in the same general region of the storm where the misocylones later developed. The observations are compared with numerical simulations from a three-dimensional cloud model initialized with sounding data from the same day.
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.
NASA Astrophysics Data System (ADS)
Szilagyi, Jozsef; Gribovszki, Zoltan; Kalicz, Peter
2007-03-01
SummaryBy applying a nonlinear reservoir approach for groundwater drainage, catchment-scale evapotranspiration (ET) during flow recessions can be expressed with the help of the lumped version of the water balance equation for the catchment. The attractiveness of the approach is that ET, in theory, can be obtained by the sole use of observed flow values for which relatively abundant and long records are available. A 2D finite element numerical model of subsurface flow in the unsaturated and saturated zones, capable of simulating moisture removal by vegetation, was first successfully employed to verify the water balance approach under ideal conditions. Subsequent practical applications over four catchments with widely varying climatic conditions however showed large disparities in comparison with monthly ET estimates of Morton's WREVAP model.
NASA Astrophysics Data System (ADS)
Abtahizadeh, Seyed Ebrahim; van Oijen, Jeroen; de Goey, Philip
2012-11-01
Recently Mild combustion is subjected to intensive research because of its unique ability to provide high efficiency and low pollutant combustion simultaneously in industrial heating processes. In most practical Mild combustion applications, a fuel jet is ignited due to recirculation of hot burned gases. The impact of burned gases on autoignition and flame stabilization has been studied in a laboratory jet-in-hot-coflow (JHC) burner. Results of this study help us to understand recent experimental observations of the Delft group (DJHC burner) in which Dutch Natural Gas (DNG) is mixed with various amounts of H2. The main focus is on the modeling of autoignition in the DJHC burner by using the Flamelet Generated Manifolds (FGM) technique. In this technique, kinetic information is tabulated with a few controlling variables which results in a significant decrease in simulation time. The FGM tabulation has been performed using igniting laminar counterflow diffusion flames. Since H2 is present in the fuel composition, it is essential to include preferential diffusion effects in the table due to the high diffusivity of H2. Based on results, the FGM table is capable to reproduce the autoignition of hydrogen containing fuel predicted by detailed chemistry in 1D counterflow flames. The Authors gratefully acknowledge financial support of the Dutch Technology Foundation STW.
Ding, Lei; Van Renterghem, Timothy; Botteldooren, Dick; Horoshenkov, Kirill; Khan, Amir
2013-12-01
The influence of loose plant leaves on the acoustic absorption of a porous substrate is experimentally and numerically studied. Such systems are typical in vegetative walls, where the substrate has strong acoustical absorbing properties. Both experiments in an impedance tube and theoretical predictions show that when a leaf is placed in front of such a porous substrate, its absorption characteristics markedly change (for normal incident sound). Typically, there is an unaffected change in the low frequency absorption coefficient (below 250 Hz), an increase in the middle frequency absorption coefficient (500-2000 Hz) and a decrease in the absorption at higher frequencies. The influence of leaves becomes most pronounced when the substrate has a low mass density. A combination of the Biot's elastic frame porous model, viscous damping in the leaf boundary layers and plate vibration theory is implemented via a finite-difference time-domain model, which is able to predict accurately the absorption spectrum of a leaf above a porous substrate system. The change in the absorption spectrum caused by the leaf vibration can be modeled reasonably well assuming the leaf and porous substrate properties are uniform.
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.
NASA Astrophysics Data System (ADS)
Mazza, Fabio; Vulcano, Alfonso
2008-07-01
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.
NASA Technical Reports Server (NTRS)
Horstman, C. C.; Settles, G. S.; Vas, I. E.; Bogdonoff, S. M.; Hung, C. M.
1977-01-01
An experiment is described that tests and guides computations of a shock-wave turbulent boundary-layer interaction flow over a 20-deg compression corner at Mach 2.85. Numerical solutions of the time-averaged Navier-Stokes equations for the entire flow field, employing various turbulence models, are compared with the data. Each model is critically evaluated by comparisons with the details of the experimental data. Experimental results for the extent of upstream pressure influence and separation location are compared with numerical predictions for a wide range of Reynolds numbers and shock-wave strengths.
NASA Astrophysics Data System (ADS)
Yin, Xiaohong; Huang, Zhijiong; Zheng, Junyu; Yuan, Zibing; Zhu, Wenbo; Huang, Xiaobo; Chen, Duohong
2017-04-01
As one of the most populous and developed provinces in China, Guangdong province (GD) has been experiencing regional haze problems. Identification of source contributions to ambient PM2.5 level is essential for developing effective control strategies. In this study, using the most up-to-date emission inventory and validated numerical model, source contributions to ambient PM2.5 from eight emission source sectors (agriculture, biogenic, dust, industry, power plant, residential, mobile and others) in GD in 2012 were quantified. Results showed that mobile sources are the dominant contributors to the ambient PM2.5 (24.0%) in the Pearl River Delta (PRD) region, the central and most developed area of GD, while industry sources are the major contributors (21.5% 23.6%) to those in the Northeastern GD (NE-GD) region and the Southwestern GD (SW-GD) region. Although many industries have been encouraged to move from the central GD to peripheral areas such as NE-GD and SW-GD, their emissions still have an important impact on the PM2.5 level in the PRD. In addition, agriculture sources are responsible for 17.5% to ambient PM2.5 in GD, indicating the importance of regulations on agricultural activities, which has been largely ignored in the current air quality management. Super-regional contributions were also quantified and their contributions to the ambient PM2.5 in GD are significant with notable seasonal differences. But they might be overestimated and further studies are needed to better quantify the transport impacts.
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.
Renormalized stress tensor in Kerr space-time: Numerical results for the Hartle-Hawking vacuum
Duffy, Gavin; Ottewill, Adrian C.
2008-01-15
We show that the pathology which afflicts the Hartle-Hawking vacuum on the Kerr black hole space-time can be regarded as due to rigid rotation of the state with the horizon in the sense that, when the region outside the speed-of-light surface is removed by introducing a mirror, there is a state with the defining features of the Hartle-Hawking vacuum. In addition, we show that, when the field is in this state, the expectation value of the energy-momentum stress tensor measured by an observer close to the horizon and rigidly rotating with it corresponds to that of a thermal distribution at the Hawking temperature rigidly rotating with the horizon.
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.
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,…
Results from a limited area mesoscale numerical simulation for 10 April 1979
NASA Technical Reports Server (NTRS)
Kalb, M. W.
1985-01-01
Results are presented from a nine-hour limited area fine mesh (35-km) mesoscale model simulation initialized with SESAME-AVE I radiosonde data for Apr. 10, 1979 at 2100 GMT. Emphasis is on the diagnosis of mesoscale structure in the mass and precipitation fields. Along the Texas/Oklahoma border, independent of the short wave, convective precipitation formed several hours into the simulation and was organized into a narrow band suggestive of the observed April 10 squall line.
NASA Technical Reports Server (NTRS)
Deluca, E. E.; Werne, J.; Rosner, R.; Cattaneo, F.
1990-01-01
Results on the transition from soft to hard turbulence in simulations of two-dimensional Boussinesq convection are reported. The computed probability densities for temperature fluctuations are exponential in form in both soft and hard turbulence, unlike what is observed in experiments. In contrast, a change is obtained in the Nusselt number scaling on Rayleigh number in good agreement with the three-dimensional experiments.
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.
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.
CRSP, numerical results for an electrical resistivity array to detect underground cavities
NASA Astrophysics Data System (ADS)
Amini, Amin; Ramazi, Hamidreza
2017-01-01
This paper is devoted to the application of the Combined Resistivity Sounding and Profiling electrode configuration (CRSP) to detect underground cavities. Electrical resistivity surveying is among the most favorite geophysical methods due to its nondestructive and economical properties in a wide range of geosciences. Several types of the electrode arrays are applied to detect different certain objectives. In one hand, the electrode array plays an important role in determination of output resolution and depth of investigations in all resistivity surveys. On the other hand, they have their own merits and demerits in terms of depth of investigations, signal strength, and sensitivity to resistivity variations. In this article several synthetic models, simulating different conditions of cavity occurrence, were used to examine the responses of some conventional electrode arrays and also CRSP array. The results showed that CRSP electrode configuration can detect the desired objectives with a higher resolution rather than some other types of arrays. Also a field case study was discussed in which electrical resistivity approach was conducted in Abshenasan expressway (Tehran, Iran) U-turn bridge site for detecting potential cavities and/or filling loose materials. The results led to detect an aqueduct tunnel passing beneath the study area.
Geometrical optics approach to the nematic liquid crystal grating: numerical results.
Kosmopoulos, J A; Zenginoglou, H M
1987-05-01
The problem of the grating action of a periodically distorted nematic liquid crystal layer, in the geometrical optics ray approximation is considered, and a theory for the calculation of the fringe powers is proposed. A nonabsorbing nematic phase is assumed, and the direction of incidence is taken to be normal to the layer. The powers of the resulting diffraction fringes are related to the spatial and angular deviation of the rays propagating across the layer and to the perturbation of the phase of the wave associated with the ray. The theory is applied to the simple case of a harmonically distorted nematic layer. In the case of a weakly distorted nematic layer the results agree with the predictions of Carroll's model, where only even-order fringes are important. As the distortion becomes larger, odd-order fringes (with the exception of the first order) become equally important, and particularly those at relatively large orders (e.g., seven and nine) exhibit maxima greater than that of the even-order neighbors. Finally, the dependence of the powers of odd-order fringes on the distortion angle is quite different from that of the even-order fringes.
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.
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.
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.
NASA Technical Reports Server (NTRS)
Burley, J. R., II; Carlson, J. R.; Henderson, W. P.
1986-01-01
Static pressure measurements were made on the afterbody, nozzle and tails of a generic single-engine axisymmetric fighter configuration. Data were recorded at Mach numbers of 0.6, 0.9, and 1.2. NPR was varied from 1.0 to 8.0 and angle of attack was varied from -3 deg. to 9 deg. Experimental data were compared with numerical results from two state-of-the-art computer codes.
New numerical results and novel effective string predictions for Wilson loops
NASA Astrophysics Data System (ADS)
Billó, M.; Caselle, M.; Pellegrini, R.
2012-01-01
We compute the prediction of the Nambu-Goto effective string model for a rectangular Wilson loop up to three loops. This is done through the use of an operatorial, first order formulation and of the open string analogues of boundary states. This result is interesting since there are universality theorems stating that the predictions up to three loops are common to all effective string models. To test the effective string prediction, we use a Montecarlo evaluation, in the 3 d Ising gauge model, of an observable (the ratio of two Wilson loops with the same perimeter) for which boundary effects are relatively small. Our simulation attains a level of precision which is sufficient to test the two-loop correction. The three-loop correction seems to go in the right direction, but is actually yet beyond the reach of our simulation, since its effect is comparable with the statistical errors of the latter.
Bathymetry Determination via X-Band Radar Data: A New Strategy and Numerical Results
Serafino, Francesco; Lugni, Claudio; Borge, Jose Carlos Nieto; Zamparelli, Virginia; Soldovieri, Francesco
2010-01-01
This work deals with the question of sea state monitoring using marine X-band radar images and focuses its attention on the problem of sea depth estimation. We present and discuss a technique to estimate bathymetry by exploiting the dispersion relation for surface gravity waves. This estimation technique is based on the correlation between the measured and the theoretical sea wave spectra and a simple analysis of the approach is performed through test cases with synthetic data. More in detail, the reliability of the estimate technique is verified through simulated data sets that are concerned with different values of bathymetry and surface currents for two types of sea spectrum: JONSWAP and Pierson-Moskowitz. The results show how the estimated bathymetry is fairly accurate for low depth values, while the estimate is less accurate as the bathymetry increases, due to a less significant role of the bathymetry on the sea surface waves as the water depth increases. PMID:22163565
NASA Astrophysics Data System (ADS)
Tselentis, G.-A.; Stavrakakis, G.; Sokos, E.; Gkika, F.; Serpetsidaki, A.
2010-05-01
In spite of the fact that the great majority of seismic tsunami is generated in ocean domains, smaller basins like the Ionian Sea sometimes experience this phenomenon. In this investigation, we study the tsunami hazard associated with the Ionian Sea fault system. A scenario-based method is used to provide an estimation of the tsunami hazard in this region for the first time. Realistic faulting parameters related to four probable seismic sources, with tsunami potential, are used to model expected coseismic deformation, which is translated directly to the water surface and used as an initial condition for the tsunami propagation. We calculate tsunami propagation snapshots and mareograms for the four seismic sources in order to estimate the expected values of tsunami maximum amplitudes and arrival times at eleven tourist resorts along the Ionian shorelines. The results indicate that, from the four examined sources, only one possesses a seismic threat causing wave amplitudes up to 4 m at some tourist resorts along the Ionian shoreline.
Insight into collision zone dynamics from topography: numerical modelling results and observations
NASA Astrophysics Data System (ADS)
Bottrill, A. D.; van Hunen, J.; Allen, M. B.
2012-07-01
Dynamic models of subduction and continental collision are used to predict dynamic topography changes on the overriding plate. The modelling results show a distinct evolution of topography on the overriding plate, during subduction, continental collision and slab break-off. A prominent topographic feature is a temporary (few Myrs) deepening in the area of the back arc-basin after initial collision. This collisional mantle dynamic basin (CMDB) is caused by slab steepening drawing material away from the base of the overriding plate. Also during this initial collision phase, surface uplift is predicted on the overriding plate between the suture zone and the CMDB, due to the subduction of buoyant continental material and its isostatic compensation. After slab detachment, redistribution of stresses and underplating of the overriding plate causes the uplift to spread further into the overriding plate. This topographic evolution fits the stratigraphy found on the overriding plate of the Arabia-Eurasia collision zone in Iran and south east Turkey. The sedimentary record from the overriding plate contains Upper Oligocene-Lower Miocene marine carbonates deposited between terrestrial clastic sedimentary rocks, in units such as the Qom Formation and its lateral equivalents. This stratigraphy shows that during the Late Oligocene-Early Miocene the surface of the overriding plate sank below sea level before rising back above sea level, without major compressional deformation recorded in the same area. This uplift and subsidence pattern correlates well with our modelled topography changes.
Insight into collision zone dynamics from topography: numerical modelling results and observations
NASA Astrophysics Data System (ADS)
Bottrill, A. D.; van Hunen, J.; Allen, M. B.
2012-11-01
Dynamic models of subduction and continental collision are used to predict dynamic topography changes on the overriding plate. The modelling results show a distinct evolution of topography on the overriding plate, during subduction, continental collision and slab break-off. A prominent topographic feature is a temporary (few Myrs) basin on the overriding plate after initial collision. This "collisional mantle dynamic basin" (CMDB) is caused by slab steepening drawing, material away from the base of the overriding plate. Also, during this initial collision phase, surface uplift is predicted on the overriding plate between the suture zone and the CMDB, due to the subduction of buoyant continental material and its isostatic compensation. After slab detachment, redistribution of stresses and underplating of the overriding plate cause the uplift to spread further into the overriding plate. This topographic evolution fits the stratigraphy found on the overriding plate of the Arabia-Eurasia collision zone in Iran and south east Turkey. The sedimentary record from the overriding plate contains Upper Oligocene-Lower Miocene marine carbonates deposited between terrestrial clastic sedimentary rocks, in units such as the Qom Formation and its lateral equivalents. This stratigraphy shows that during the Late Oligocene-Early Miocene the surface of the overriding plate sank below sea level before rising back above sea level, without major compressional deformation recorded in the same area. Our modelled topography changes fit well with this observed uplift and subsidence.
NASA Astrophysics Data System (ADS)
Baird, Alan F.; McKinnon, Stephen D.
2007-03-01
Analysis of stress measurement data from the near-surface to crustal depths in southern Ontario show a misalignment between the direction of tectonic loading and the orientation of the major horizontal principal stress. The compressive stress field instead appears to be oriented sub-parallel to the major terrane boundaries such as the Grenville Front, the Central Metasedimentary Belt boundary zone and the Elzevir Frontenac boundary zone. This suggests that the stress field has been modified by these deep crustal scale deformation zones. In order to test this hypothesis, a geomechanical model was constructed using the three-dimensional discontinuum stress analysis code 3DEC. The model consists of a 45 km thick crust of southern Ontario in which the major crustal scale deformation zones are represented as discrete faults. Lateral velocity boundary conditions were applied to the sides of the model in the direction of tectonic loading in order to generate the horizontal compressive stress field. Modelling results show that for low strength (low friction angle and cohesion), fault slip causes the stress field to rotate toward the strike of the faults, consistent with the observed direction of misalignment with the tectonic loading direction. Observed distortions to the regional stress field may be explained by this relatively simple mechanism of slip on deep first-order structures in response to the neotectonic driving forces.
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.
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.
Haji Abolhassani, A. A.; Matte, J.-P.
2012-10-15
Electron energy distribution functions are expressed as a sum of 6-12 Maxwellians or a sum of 3, but each multiplied by a finite series of generalized Laguerre polynomials. We fitted several distribution functions obtained from the finite difference Fokker-Planck code 'FPI'[Matte and Virmont, Phys. Rev. Lett. 49, 1936 (1982)] to these forms, by matching the moments, and showed that they can represent very well the coexistence of hot and cold populations, with a temperature ratio as high as 1000. This was performed for two types of problems: (1) the collisional relaxation of a minority hot component in a uniform plasma and (2) electron heat flow down steep temperature gradients, from a hot to a much colder plasma. We find that the multi-Maxwellian representation is particularly good if we accept complex temperatures and coefficients, and it is always better than the representation with generalized Laguerre polynomials for an equal number of moments. For the electron heat flow problem, the method was modified to also fit the first order anisotropy f{sub 1}(x,v,t), again with excellent results. We conclude that this multi-Maxwellian representation can provide a viable alternative to the finite difference speed or energy grid in kinetic codes.
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.
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.
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.
NASA Astrophysics Data System (ADS)
Gilmore, M.; Desjardins, T. R.; Fisher, D. M.
2016-10-01
Ongoing experiments and numerical modeling on the effects of flow shear on electrostatic turbulence in the presence of electrode biasing are being conducted in helicon plasmas in the linear HelCat (Helicon-Cathode) device. It is found that changes in flow shear, affected by electrode biasing through Er x Bz rotation, can strongly affect fluctuation dynamics, including fully suppressing the fluctuations or inducing chaos. The fundamental underlying instability, at least in the case of low magnetic field, is identified as a hybrid resistive drift-Kelvin-Helmholtz mode. At higher magnetic fields, multiple modes (resistive drift, rotation-driven interchange and/or Kelvin-Helmholtz) are present, and interact nonlinearly. At high positive electrode bias (V >10Te), a large amplitude, global instability, identified as the potential relaxation instability is observed. Numerical modeling is also being conducted, using a 3 fluid global Braginskii solver for no or moderate bias cases, and a 1D PIC code for high bias cases. Recent experimental and numerical results will be presented. Supported by U.S. National Science Foundation Award 1500423.
Vouk, D; Nakic, D; Štirmer, N; Baricevic, A
2017-02-01
Final disposal of sewage sludge is important not only in terms of satisfying the regulations, but the aspect of choosing the optimal wastewater treatment technology, including the sludge treatment. In most EU countries, significant amounts of stabilized and dewatered sludge are incinerated, and sewage sludge ash (SSA) is generated as a by product. At the same time, lime is one of the commonly used additives in the sewage sludge treatment primarily to stabilize the sludge. In doing so, the question arose how desirable is such addition of lime if the sludge is subsequently incinerated, and the generated ash is further used in the production of cementitious materials. A series of mortars were prepared where 10-20% of the cement fraction was replaced by SSA. Since all three types of analyzed SSA (without lime, with lime added during sludge stabilization and with extra lime added during sludge incineration) yielded nearly same results, it can be concluded that if sludge incineration is accepted solution, lime addition during sludge treatment is unnecessary even from the standpoint of preserving the pozzolanic properties of the resulting SSA. Results of the research carried out on cement mortars point to the great possibilities of using SSA in concrete industry.
Monir, Md. Mamun; Zhu, Jun
2017-01-01
Most of the genome-wide association studies (GWASs) for human complex diseases have ignored dominance, epistasis and ethnic interactions. We conducted comparative GWASs for total cholesterol using full model and additive models, which illustrate the impacts of the ignoring genetic variants on analysis results and demonstrate how genetic effects of multiple loci could differ across different ethnic groups. There were 15 quantitative trait loci with 13 individual loci and 3 pairs of epistasis loci identified by full model, whereas only 14 loci (9 common loci and 5 different loci) identified by multi-loci additive model. Again, 4 full model detected loci were not detected using multi-loci additive model. PLINK-analysis identified two loci and GCTA-analysis detected only one locus with genome-wide significance. Full model identified three previously reported genes as well as several new genes. Bioinformatics analysis showed some new genes are related with cholesterol related chemicals and/or diseases. Analyses of cholesterol data and simulation studies revealed that the full model performs were better than the additive-model performs in terms of detecting power and unbiased estimations of genetic variants of complex traits. PMID:28079101
Connor, Rebecca F; Hurd, David; Pettenati, Mark J; Koty, Patrick; Molnár, István
2006-10-01
Imatinib mesylate, an inhibitor of BCR/ABL tyrosine kinase, has remarkable activity in chronic myeloid leukemia resulting in an 87% major cytogenetic response. We describe a woman who failed to achieve any cytogenetic response after 2.5 years of imatinib, 400mg daily. When daily sargramostim (GM-CSF) 100 microg/m2 was added, cytogenetic studies revealed a gradual increase in percentage of normal cells from start, 4, 9, and 15 months at 0%, 10%, 55%, and 85%, respectively. She became transfusion independent after starting GM-CSF. The addition of GM-CSF to imatinib resulted in a clinical benefit and a major cytogenetic response in this patient.
Shirakusa, T
2000-10-01
This time, in 3008 lung cancer patients, the postoperative results were analyzed under the new stage grouping of TNM classification. All of those patients underwent the operation in 1989, and the 5 year-survival rates had beeb surveyed in 1996 by JACS (The Japanese Association for Chest Surgery). Under the new TNM classification established in 1996 worldwidey, T3N0M0 was transferred from IIIA to IIB. This report is the additional one in the focus of the results accompanied with the change of TNM classification.
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.
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.
LeBlanc, J. P. F.; Antipov, Andrey E.; Becca, Federico; ...
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
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.
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.
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.
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.
Hand, J W; Li, Y; Hajnal, J V
2010-02-21
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 SAR(MWB) < or = 2 W kg(-1) (continuous or time-averaged over 6 min)), whole foetal SAR, local foetal SAR(10 g) and average foetal temperature are within international safety limits. For continuous RF exposure at SAR(MWB) = 2 W kg(-1) over periods of 7.5 min or longer, a maximum local foetal temperature >38 degrees 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 SAR(MWB) = 2 W kg(-1), some local SAR(10g) values in the mother's trunk and extremities exceed recommended limits.
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).
Optimization of SiO2-TiNxOy-Cu interference absorbers: numerical and experimental results
NASA Astrophysics Data System (ADS)
Lazarov, Michel P.; Sizmann, R.; Frei, Ulrich
1993-10-01
SiO2 - TiNxOy-Cu absorbers were prepared with activated reactive evaporation (ARE). The deposition parameters for the ARE process were adjusted according to the results of the numerical optimizations by a genetic algorithm. We present spectral reflectance, calorimetric and grazing incidence X-ray reflection (GXR) measurements. Best coatings for applications as selective absorber in the range of T equals 100 (DOT)(DOT)(DOT) 200 degree(s)C exhibit a solar absorptance of 0.94 and a near normal emittance of 0.044 at 100 degree(s)C. This emittance is correlated with the hemispherical emittance of 0.061 obtained from calorimetric measurements at 200 degree(s)C. First results on lifetime studies show that the coatings are thermally stable under vacuum up to 400 degree(s)C. The SiO2 film passivates the absorber, a substantial slow down of degradation in dry air is observed. Our tests demonstrate that the coating will withstand break down in cooling fluid and vacuum if mounted in an evacuated collector.
NASA Astrophysics Data System (ADS)
Shokrollahi, Mahvash; Semnani, Dariush; Morshed, Mohammad; Rezaei, Behzad; Mirsoofian, Mehdi
2013-12-01
PVA-TiO2 nanocomposite polymer electrolytes (PEs) were produced with different amounts of TiO2 (0, 5, 10, 15, and 20 wt.%) using the electrospinning process. Morphological studies of PVA-TiO2 nanofibers were accomplished with SEM. PVA-TiO2 membranes exhibited a high porosity of 79-91%. The impedance results showed that incorporation of TiO2 into the nanofiber membrane improved its ionic conductivity from 0.7 × 10-5 to 2.5 × 10-5 S/cm at room temperature. Nanofiber PEs showed very good reversibility and electrochemical stability up to 4.7 V. Diffusion coefficient of Li ion into PVA-TiO2 nanocomposite PEs was estimated by using a complex numerical model of partial differential equation for evaluation of ion transmission. Diffusion coefficient of PVA-TiO2 PEs containing different amounts of TiO2 (0, 5, 10, 15, and 20 wt.%) increased with increasing the nanoparticles content.
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.
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 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.
Varret, M; Rabés, J P; Thiart, R; Kotze, M J; Baron, H; Cenarro, A; Descamps, O; Ebhardt, M; Hondelijn, J C; Kostner, G M; Miyake, Y; Pocovi, M; Schmidt, H; Schuster, H; Stuhrmann, M; Yamamura, T; Junien, C; Béroud, C; Boileau, C
1998-01-01
Mutations in the LDL receptor gene (LDLR) cause familial hypercholesterolemia (FH), a common autosomal dominant disorder. The LDLR database is a computerized tool that has been developed to provide tools to analyse the numerous mutations that have been identified in the LDLR gene. The second version of the LDLR database contains 140 new entries and the software has been modified to accommodate four new routines. The analysis of the updated data (350 mutations) gives the following informations: (i) 63% of the mutations are missense, and only 20% occur in CpG dinucleotides; (ii) although the mutations are widely distributed throughout the gene, there is an excess of mutations in exons 4 and 9, and a deficit in exons 13 and 15; (iii) the analysis of the distribution of mutations located within the ligand-binding domain shows that 74% of the mutations in this domain affect a conserved amino-acid, and that they are mostly confined in the C-terminal region of the repeats. Conversely, the same analysis in the EGF-like domain shows that 64% of the mutations in this domain affect a non-conserved amino-acid, and, that they are mostly confined in the N-terminal half of the repeats. The database is now accessible on the World Wide Web at http://www.umd.necker.fr PMID:9399845
NASA Astrophysics Data System (ADS)
Crow, W.; Gasda, S. E.; Williams, D. B.; Celia, M. A.; Carey, J. W.
2008-12-01
An important aspect of the risk associated with geological CO2 sequestration is the integrity of existing wellbores that penetrate geological layers targeted for CO2 injection. CO2 leakage may occur through multiple pathways along a wellbore, including through micro-fractures and micro-annuli within the "disturbed zone" surrounding the well casing. The effective permeability of this zone is a key parameter of wellbore integrity required for validation of numerical models. This parameter depends on a number of complex factors, including long-term attack by aggressive fluids, poor well completion and actions related to production of fluids through the wellbore. Recent studies have sought to replicate downhole conditions in the laboratory to identify the mechanisms and rates at which cement deterioration occurs. However, field tests are essential to understanding the in situ leakage properties of the millions of wells that exist in the mature sedimentary basins in North America. In this study, we present results from a field study of a 30-year-old production well from a natural CO2 reservoir. The wellbore was potentially exposed to a 96% CO2 fluid from the time of cement placement, and therefore cement degradation may be a significant factor leading to leakage pathways along this wellbore. A series of downhole tests was performed, including bond logs and extraction of sidewall cores. The cores were analyzed in the laboratory for mineralogical and hydrologic properties. A pressure test was conducted over an 11-ft section of well to determine the extent of hydraulic communication along the exterior of the well casing. Through analysis of this pressure test data, we are able estimate the effective permeability of the disturbed zone along the exterior of wellbore over this 11-ft section. We find the estimated range of effective permeability from the field test is consistent with laboratory analysis and bond log data. The cement interfaces with casing and/or formation are
NASA Astrophysics Data System (ADS)
Lo Russo, S.; Taddia, G.; Gnavi, L.
2012-04-01
KEY WORDS: Open-loop ground water heat pump; Feflow; Low-enthalpy; Thermal Affected Zone; Turin; Italy The increasing diffusion of low-enthalpy geothermal open-loop Groundwater Heat Pumps (GWHP) providing buildings air conditioning requires a careful assessment of the overall effects on groundwater system, especially in the urban areas where several plants can be close together and interfere. One of the fundamental aspects in the realization of an open loop low-enthalpy geothermal system is therefore the capacity to forecast the effects of thermal alteration produced in the ground, induced by the geothermal system itself. The impact on the groundwater temperature in the surrounding area of the re-injection well (Thermal Affected Zone - TAZ) is directly linked to the aquifer properties. The transient dynamic of groundwater discharge and temperature variations should be also considered to assess the subsurface environmental effects of the plant. The experimental groundwater heat pump system used in this study is installed at the "Politecnico di Torino" (NW Italy, Piedmont Region). This plant provides summer cooling needs for the university buildings. This system is composed by a pumping well, a downgradient injection well and a control piezometer. The system is constantly monitored by multiparameter probes measuring the dynamic of groundwater temperature. A finite element subsurface flow and transport simulator (FEFLOW) was used to investigate the thermal aquifer alteration. Simulations were continuously performed during May-October 2010 (cooling period). The numerical simulation of the heat transport in the aquifer was solved with transient conditions. The simulation was performed by considering only the heat transfer within the saturated aquifer, without any heat dispersion above or below the saturated zone due to the lack of detailed information regarding the unsaturated zone. Model results were compared with experimental temperature data derived from groundwater
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.
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 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
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.
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
Aschengrau, Ann; Rogers, Sarah; Ozonoff, David
2003-01-01
In 1998 we published the results of a study suggesting an association between breast cancer and perchloroethylene (PCE; also called tetrachloroethylene) exposure from public drinking water. The present case-control study was undertaken to evaluate this association further. The cases were composed of female residents of eight towns in the Cape Cod region of Massachusetts who had been diagnosed with breast cancer from 1987 through 1993 (n = 672). Controls were composed of demographically similar women from the same towns (n = 616). Women were exposed to PCE when it leached from the vinyl lining of water distribution pipes from the late 1960s through the early 1980s. A relative delivered dose of PCE that entered a home was estimated using an algorithm that took into account residential history, water flow, and pipe characteristics. Small to moderate elevations in risk were seen among women whose exposure levels were above the 75th and 90th percentiles when 0-15 years of latency were considered (adjusted odds ratios, 1.5-1.9 for > 75th percentile, 1.3-2.8 for > 90th percentile). When data from the present and prior studies were combined, small to moderate increases in risk were also seen among women whose exposure levels were above the 75th and 90th percentiles when 0-15 years of latency were considered (adjusted odds ratios, 1.6-1.9 for > 75th percentile, 1.3-1.9 for > 90th percentile). The results of the present study confirm those of the previous one and suggest that women with the highest PCE exposure levels have a small to moderate increased risk of breast cancer. PMID:12573900
Gramatges, Maria M.; Qi, Xiaodong; Sasa, Ghadir S.; Chen, Julian J.-L.
2013-01-01
Hoyeraal Hreidarsson syndrome (HHS) is a form of dyskeratosis congenita (DC) characterized by bone marrow failure, intrauterine growth retardation, developmental delay, microcephaly, cerebellar hypoplasia, immunodeficiency, and extremely short telomeres. As with DC, mutations in genes encoding factors required for telomere maintenance, such as telomerase reverse transcriptase (TERT), have been found in patients with HHS. We describe 2 sibling HHS cases caused by a homozygous mutation (p.T567M) within the TERT T motif. This mutation resulted in a marked reduction in the capacity of telomerase to processively synthesize telomeric repeats, indicating a role for the T motif in this unique aspect of telomerase function. We support this finding by demonstrating defective processivity in the previously reported p.K570N T-motif mutation. The consanguineous, heterozygous p.T567M parents exhibited telomere lengths around the first percentile and no evidence of a DC phenotype. Although heterozygous processivity defects have been associated with familial, adult-onset pulmonary fibrosis, these cases demonstrate the severe clinical and functional impact of biallelic processivity mutations. Thus, despite retaining the capacity to add short stretches of telomeric repeats onto the shortest telomeres, sole expression of telomerase processivity mutants can lead to a profound failure of telomere maintenance and early-onset multisystem disease. PMID:23538340
NASA Astrophysics Data System (ADS)
Nick, F. M.; van der Veen, C. J.; Vieli, A.; Pattyn, F.; Hubbard, A.; Box, J. E.
2010-12-01
Calving of icebergs and bottom melting from ice shelves accounts for roughly half the ice transferred from the Greenland Ice Sheet into the surrounding ocean, and virtually all of the ice loss from the Antarctic Ice Sheet. Petermann Glacier (north Greenland) with its ~17 km wide and ~ 60 km long floating ice-shelf is experiencing high rates of bottom melting. The recent partial disintegration of its shelf (in August 2010) presents a natural experiment to investigate the dynamic response of the ice sheet to its shelf retreat. We apply a numerical ice flow model using a physically-based calving criterion based on crevasse depth to investigate the contribution of processes such as shelf disintegration, bottom melting, sea ice or sikkusak disintegration and surface run off to the mass balance of Petermann Glacier and assess its stability. Our modeling study provides insights into the role of ice-ocean interaction, and on response of Petermann Glacier to its recent massive ice loss.
NASA Astrophysics Data System (ADS)
Nick, Faezeh M.; Hubbard, Alun; van der Veen, Kees; Vieli, Andreas
2010-05-01
Calving of icebergs and bottom melting from ice shelves accounts for roughly half the ice transferred from the Greenland Ice Sheet into the surrounding ocean, and virtually all of the ice loss from the Antarctic Ice Sheet. Petermann Glacier (north Greenland) with its 16 km wide and 80 km long floating tongue, experiences massive bottom melting. We apply a numerical ice flow model using a physically-based calving criterion based on crevasse depth to investigate the contribution of processes such as bottom melting, sea ice or sikkusak disintegration, surface run off and iceberg calving to the mass balance and instability of Petermann Glacier and its ice shelf. Our modelling study provides insights into the role of ice-ocean interaction, and on how to incorporate calving in ice sheet models, improving our ability to predict future ice sheet change.
NASA Astrophysics Data System (ADS)
Nick, F.; Hubbard, A.; Vieli, A.; van der Veen, C. J.; Box, J. E.; Bates, R.; Luckman, A. J.
2009-12-01
Calving of icebergs and bottom melting from ice shelves accounts for roughly half the ice transferred from the Greenland Ice Sheet into the surrounding ocean, and virtually all of the ice loss from the Antarctic Ice Sheet. Petermann Glacier (north Greenland) with its 16 km wide and 80 km long floating tongue, experiences massive bottom melting. We apply a numerical ice flow model using a physically-based calving criterion based on crevasse depth to investigate the contribution of processes such as bottom melting, sea ice or sikkusak disintegration, surface run off and iceberg calving to the mass balance and instability of Petermann Glacier and its ice shelf. Our modeling study provides insights into the role of ice-ocean interaction, and on how to incorporate calving in ice sheet models, improving our ability to predict future ice sheet change.
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)
Tinti, S.; Tonini, R.; Armigliato, A.; Zaniboni, F.; Pagnoni, G.; Gallazzi, Sara; Bressan, Lidia
2010-05-01
The tsunamigenic earthquake (M 8.8) that occurred offshore central Chile on 27 February 2010 can be classified as a typical subduction-zone earthquake. The effects of the ensuing tsunami have been devastating along the Chile coasts, and especially between the cities of Valparaiso and Talcahuano, and in the Juan Fernandez islands. The tsunami propagated across the entire Pacific Ocean, hitting with variable intensity almost all the coasts facing the basin. While the far-field propagation was quite well tracked almost in real-time by the warning centres and reasonably well reproduced by the forecast models, the toll of lives and the severity of the damage caused by the tsunami in the near-field occurred with no local alert nor warning and sadly confirms that the protection of the communities placed close to the tsunami sources is still an unresolved problem in the tsunami early warning field. The purpose of this study is two-fold. On one side we perform numerical simulations of the tsunami starting from different earthquake models which we built on the basis of the preliminary seismic parameters (location, magnitude and focal mechanism) made available by the seismological agencies immediately after the event, or retrieved from more detailed and refined studies published online in the following days and weeks. The comparison with the available records of both offshore DART buoys and coastal tide-gauges is used to put some preliminary constraints on the best-fitting fault model. The numerical simulations are performed by means of the finite-difference code UBO-TSUFD, developed and maintained by the Tsunami Research Team of the University of Bologna, Italy, which can solve both the linear and non-linear versions of the shallow-water equations on nested grids. The second purpose of this study is to use the conclusions drawn in the previous part in a tsunami early warning perspective. In the framework of the EU-funded project DEWS (Distant Early Warning System), we will
NASA Astrophysics Data System (ADS)
Donmez, Orhan
The shocked wave created on the accretion disk after different physical phenomena (accretion flows with pressure gradients, star-disk interaction etc.) may be responsible observed Quasi Periodic Oscillations (QPOs) in X-ray binaries. We present the set of characteristics frequencies associated with accretion disk around the rotating and non-rotating black holes for one particle case. These persistent frequencies are results of the rotating pattern in an accretion disk. We compare the frequency's from two different numerical results for fluid flow around the non-rotating black hole with one particle case. The numerical results are taken from Refs. 1 and 2 using fully general relativistic hydrodynamical code with non-selfgravitating disk. While the first numerical result has a relativistic tori around the black hole, the second one includes one-armed spiral shock wave produced from star-disk interaction. Some physical modes presented in the QPOs can be excited in numerical simulation of relativistic tori and spiral waves on the accretion disk. The results of these different dynamical structures on the accretion disk responsible for QPOs are discussed in detail.
NASA Astrophysics Data System (ADS)
Khan, Sheema; Morton, Thomas L.; Ronis, David
1987-05-01
The static correlations in highly charged colloidal and micellar suspensions, with and without added electrolyte, are examined using the hypernetted-chain approximation (HNC) for the macro-ion-macro-ion correlations and the mean-spherical approximation for the other correlations. By taking the point-ion limit for the counter-ions, an analytic solution for the counter-ion part of the problem can be obtained; this maps the macro-ion part of the problem onto a one-component problem where the macro-ions interact via a screened Coulomb potential with the Gouy-Chapman form for the screening length and an effective charge that depends on the macro-ion-macro-ion pair correlations. Numerical solutions of the effective one-component equation in the HNC approximation are presented, and in particular, the effects of macro-ion charge, nonadditive core diameters, and added electrolyte are examined. As we show, there can be a strong renormalization of the effective macro-ion charge and reentrant melting in colloidal crystals.
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)
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.; 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
NASA Astrophysics Data System (ADS)
Jurjiu, Aurel; Galiceanu, Mircea; Farcasanu, Alexandru; Chiriac, Liviu; Turcu, Flaviu
2016-12-01
In this paper, we focus on the relaxation dynamics of Sierpinski hexagon fractal polymer. The relaxation dynamics of this fractal polymer is investigated in the framework of the generalized Gaussian structure model using both Rouse and Zimm approaches. In the Rouse-type approach, by performing real-space renormalization transformations, we determine analytically the complete eigenvalue spectrum of the connectivity matrix. Based on the eigenvalues obtained through iterative algebraic relations we calculate the averaged monomer displacement and the mechanical relaxation moduli (storage modulus and loss modulus). The evaluation of the dynamical properties in the Rouse-type approach reveals that they obey scaling in the intermediate time/frequency domain. In the Zimm-type approach, which includes the hydrodynamic interactions, the relaxation quantities do not show scaling. The theoretical findings with respect to scaling in the intermediate domain of the relaxation quantities are well supported by experimental results.
NASA Astrophysics Data System (ADS)
van Poppel, Bret; Owkes, Mark; Nelson, Thomas; Lee, Zachary; Sowell, Tyler; Benson, Michael; Vasquez Guzman, Pablo; Fahrig, Rebecca; Eaton, John; Kurman, Matthew; Kweon, Chol-Bum; Bravo, Luis
2014-11-01
In this work, we present high-fidelity Computational Fluid Dynamics (CFD) results of liquid fuel injection from a pressure-swirl atomizer and compare the simulations to experimental results obtained using both shadowgraphy and phase-averaged X-ray computed tomography (CT) scans. The CFD and experimental results focus on the dense near-nozzle region to identify the dominant mechanisms of breakup during primary atomization. Simulations are performed using the NGA code of Desjardins et al (JCP 227 (2008)) and employ the volume of fluid (VOF) method proposed by Owkes and Desjardins (JCP 270 (2013)), a second order accurate, un-split, conservative, three-dimensional VOF scheme providing second order density fluxes and capable of robust and accurate high density ratio simulations. Qualitative features and quantitative statistics are assessed and compared for the simulation and experimental results, including the onset of atomization, spray cone angle, and drop size and distribution.
NASA Astrophysics Data System (ADS)
Ji, B.; Peng, X. X.; Long, X. P.; Luo, X. W.; Wu, Y. L.
2015-12-01
Results of cavitating turbulent flow simulation around a twisted hydrofoil were presented in the paper using the Partially-Averaged Navier-Stokes (PANS) method (Ji et al. 2013a), Large-Eddy Simulation (LES) (Ji et al. 2013b) and Reynolds-Averaged Navier-Stokes (RANS). The results are compared with available experimental data (Foeth 2008). The PANS and LES reasonably reproduce the cavitation shedding patterns around the twisted hydrofoil with primary and secondary shedding, while the RANS model fails to simulate the unsteady cavitation shedding phenomenon and yields an almost steady flow with a constant cavity shape and vapor volume. Besides, it is noted that the predicted shedding vapor cavity by PANS is more turbulent and the shedding vortex is stronger than that by LES, which is more consistent with experimental photos.
NASA Astrophysics Data System (ADS)
Wang, Huihui; Sukhomlinov, Vladimir S.; Kaganovich, Igor D.; Mustafaev, Alexander S.
2017-02-01
Using the Monte Carlo collision method, we have performed simulations of ion velocity distribution functions (IVDF) taking into account both elastic collisions and charge exchange collisions of ions with atoms in uniform electric fields for argon and helium background gases. The simulation results are verified by comparison with the experiment data of the ion mobilities and the ion transverse diffusion coefficients in argon and helium. The recently published experimental data for the first seven coefficients of the Legendre polynomial expansion of the ion energy and angular distribution functions are used to validate simulation results for IVDF. Good agreement between measured and simulated IVDFs shows that the developed simulation model can be used for accurate calculations of IVDFs.
Influence of the quantum well models on the numerical simulation of planar InGaN/GaN LED results
NASA Astrophysics Data System (ADS)
Podgórski, J.; Woźny, J.; Lisik, Z.
2016-04-01
Within this paper, we present electric model of a light emitting diode (LED) made of gallium nitride (GaN) followed by examples of simulation results obtained by means of Sentaurus software, which is the part of the TCAD package. The aim of this work is to answer the question of whether physical models of quantum wells used in commercial software are suitable for a correct analysis of the lateral LEDs made of GaN.
ERIC Educational Resources Information Center
Zemsky, Robert; Shaman, Susan; Shapiro, Daniel B.
2001-01-01
Describes the Collegiate Results Instrument (CRI), which measures a range of collegiate outcomes for alumni 6 years after graduation. The CRI was designed to target alumni from institutions across market segments and assess their values, abilities, work skills, occupations, and pursuit of lifelong learning. (EV)
NASA Astrophysics Data System (ADS)
Mosteller, R.
2014-04-01
Results obtained with the MCNP5 Monte Carlo code and the ENDF/B-VII.1 and ENDF/B-VII.0 nuclear data libraries have been compared for the 119 benchmarks in the expanded criticality validation suite for MCNP and for 23 additional benchmarks. ENDF/B-VII.1 was found to produce improvements relative to ENDF/B-VII.0 for benchmarks that contain significant amounts of tungsten, zirconium, cadmium, or beryllium, although the results for the benchmarks with beryllium suggest that further improvement still may be needed. In addition, a number of deficiencies previously identified for ENDF/B-VII.0 still remain in ENDF/B-VII.1.
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 Astrophysics Data System (ADS)
Tamiya, K.; Tamagaki, R.
1981-10-01
Results obtained by applying a formulation based on the reaction matrix theory developed in I are given. Calculations by making use of a modified realistic potential, the Reid soft-core potential with the OPEP-part enhanced due to the isobar (Δ)-mixing, show that the transition to the [ALS] phase of quasi-neutrons corresponding to a typical π0 condensation occurs in the region of (2 ˜ 3) times the nuclear density. The most important ingredients responsible for this transition are the growth of the attractive 3P2 + 3F2 contribution mainly from the spin-parallel pairs in the same leyers and the reduction of the repulsive 3P1 contribution mainly from the spin-antiparallel pairs in the nearest layers; these mainfest themselves as the [ALS]-type localization develops. Properties of the matter under the new phase thus obtained such as the shape of the Fermi surface and the effective mass are discussed.
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.
Ndiaye, L G; Caillat, S; Chinnayya, A; Gambier, D; Baudoin, B
2010-07-01
In order to simulate granular materials structure in a rotary kiln under the steady-state regime, a mathematical model has been developed by Saeman (1951). This model enables the calculation of the bed profiles, the axial velocity and solids flow rate along the kiln. This model can be coupled with a thermochemical model, in the case of a reacting moving bed. This dynamic model was used to calculate the bed profile for an industrial size kiln and the model projections were validated by measurements in a 4 m diameter by 16 m long industrial rotary kiln. The effect of rotation speed under solids bed profile and the effect of the feed rate under filling degree were established. On the basis of the calculations and the experimental results a phenomenological relation for the residence time estimation was proposed for the rotary kiln.
NASA Astrophysics Data System (ADS)
Yu, Hua-Gen
2004-02-01
Two quantum mechanical Hamiltonians have been derived in orthogonal polyspherical coordinates, which can be formed by Jacobi and/or Radau vectors etc., for the study of the vibrational spectra of six-atom molecules. The Hamiltonians are expressed in an explicit Hermitian form in the spatial representation. Their matrix representations are described in both full discrete variable representation (DVR) and mixed DVR/nondirect product finite basis representation (FBR) bases. The two-layer Lanczos iteration algorithm [H.-G. Yu, J. Chem. Phys. 117, 8190 (2002)] is employed to solve the eigenvalue problem of the system. A strategy regarding how to carry out the Hamiltonian-vector products for a high-dimensional problem is discussed. By exploiting the inversion symmetry of molecules, a unitary sequential 1D matrix-vector multiplication algorithm is proposed to perform the action of the Hamiltonian on the wavefunction in a symmetrically adapted DVR or FBR basis in the azimuthal angular variables. An application to the vibrational energy levels of the molecular hydrogen trimer (H2)3 in full dimension (12D) is presented. Results show that the rigid-H2 approximation can underestimate the binding energy of the trimer by 27%. Finally, it is demonstrated that the two-layer Lanczos algorithm is also capable of computing the eigenvectors of the system with minor effort.
NASA Astrophysics Data System (ADS)
Mecikalski, J. R.; Hain, C. R.; Anderson, M. C.
2006-05-01
behavior of the four layers used in the land-surface models. This presentation will first overview how volumetric soil moisture estimates from ALEXI, NAM (EDAS), and LDAS will be validated against observations taken over the continental United States during the years of 2003/2004. Results will be quantified through statistical techniques. Second, upon successful validation of ALEXI-derived volumetric soil moisture, these estimates will be used to initialize mesoscale simulations using both the Weather and Forecasting Model (WRF) and MM5. The process used is a unique implementation of GOES satellite-estimated soil moisture, a process which has not yet been attempted. The focus of this presentation is to examine the effects of ALEXI-derived volumetric soil moisture on the simulations during several case study days in 2003 and 2004. The soil moisture estimates from ALEXI will initially be used to initialize these models at a spatial resolution of 10 km. Initialization of high-resolution land-surface characteristic datasets within our model simulations such as fraction of vegetative cover and leaf area index (LAI) will also be examined as these datasets are native to the calculation of parameters used in the derivation of ALEXI soil moisture. This process will help to quantify the sensitivity and importance of a higher-resolution soil moisture dataset, and one that does not rely on the assimilation of antecedent precipitation. Results will be quantified through statistical verification techniques.
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.
SLAC E155 and E155x Numeric Data Results and Data Plots: Nucleon Spin Structure Functions
The nucleon spin structure functions g1 and g2 are important tools for testing models of nucleon structure and QCD. Experiments at CERN, DESY, and SLAC have measured g1 and g2 using deep inelastic scattering of polarized leptons on polarized nucleon targets. The results of these experiments have established that the quark component of the nucleon helicity is much smaller than naive quark-parton model predictions. The Bjorken sum rule has been confirmed within the uncertainties of experiment and theory. The experiment E155 at SLAC collected data in March and April of 1997. Approximately 170 million scattered electron events were recorded to tape. (Along with several billion inclusive hadron events.) The data were collected using three independent fixed-angle magnetic spectrometers, at approximately 2.75, 5.5, and 10.5 degrees. The momentum acceptance of the 2.75 and 5.5 degree spectrometers ranged from 10 to 40 GeV, with momentum resolution of 2-4%. The 10.5 degree spectrometer, new for E155, accepted events of 7 GeV to 20 GeV. Each spectrometer used threshold gas Cerenkov counters (for particle ID), a segmented lead-glass calorimeter (for energy measurement and particle ID), and plastic scintillator hodoscopes (for tracking and momentum measurement). The polarized targets used for E155 were 15NH3 and 6LiD, as targets for measuring the proton and deuteron spin structure functions respectively. Experiment E155x recently concluded a successful two-month run at SLAC. The experiment was designed to measure the transverse spin structure functions of the proton and deuteron. The E155 target was also recently in use at TJNAF's Hall C (E93-026) and was returned to SLAC for E155x. E155x hopes to reduce the world data set errors on g2 by a factor of three. [Copied from http://www.slac.stanford.edu/exp/e155/e155_nickeltour.html, an information summary linked off the E155 home page at http://www.slac.stanford.edu/exp/e155/e155_home.html. The extension run, E155x, also makes
Reverter, A; Henshall, J M; McCulloch, R; Sasazaki, S; Hawken, R; Lehnert, S A
2014-05-01
these approaches are applied to the estimation of allele frequencies, the resulting estimates allow for the development of cost-effective and reliable GWAS.
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.
Park, Bu S; Rajan, Sunder S; Guag, Joshua W; Angelone, Leonardo M
2015-04-01
Materials with high dielectric constant (HDC) have been used in high field MRI to decrease specific absorption rate (SAR), increase magnetic field intensity, and increase signal-to-noise ratio. In previous studies, the HDC materials were placed inside the RF coil decreasing the space available. This study describes an alternative approach that considers an HDC-based sleeve placed outside the RF coil. The effects of an HDC on the electromagnetic (EM) field were studied using numerical simulations with a coil unloaded and loaded with a human head model. In addition, experimental EM measurements at 128 MHz were performed inside a custom-made head coil, fitted with a distilled water sleeve. The numerical simulations showed up to 40% decrease in maximum 10 g-avg. SAR on the surface of the head model with an HDC material of barium titanate. Experimental measurements also showed up to 20% decrease of maximum electric field using an HDC material of distilled water. The proposed method can be incorporated in the design of high field transmit RF coils.
NASA Technical Reports Server (NTRS)
Westphalen, H.; Spjeldvik, W. N.
1982-01-01
A theoretical method by which the energy dependence of the radial diffusion coefficient may be deduced from spectral observations of the particle population at the inner edge of the earth's radiation belts is presented. This region has previously been analyzed with numerical techniques; in this report an analytical treatment that illustrates characteristic limiting cases in the L shell range where the time scale of Coulomb losses is substantially shorter than that of radial diffusion (L approximately 1-2) is given. It is demonstrated both analytically and numerically that the particle spectra there are shaped by the energy dependence of the radial diffusion coefficient regardless of the spectral shapes of the particle populations diffusing inward from the outer radiation zone, so that from observed spectra the energy dependence of the diffusion coefficient can be determined. To insure realistic simulations, inner zone data obtained from experiments on the DIAL, AZUR, and ESRO 2 spacecraft have been used as boundary conditions. Excellent agreement between analytic and numerical results is reported.
Bottenus, Danny; Jubery, Talukder Zaki; Dutta, Prashanta; Ivory, Cornelius F
2011-02-01
This paper describes both the experimental application and 3-D numerical simulation of isotachophoresis (ITP) in a 3.2 cm long "cascade" poly(methyl methacrylate) (PMMA) microfluidic chip. The microchip includes 10 × reductions in both the width and depth of the microchannel, which decreases the overall cross-sectional area by a factor of 100 between the inlet (cathode) and outlet (anode). A 3-D numerical simulation of ITP is outlined and is a first example of an ITP simulation in three dimensions. The 3-D numerical simulation uses COMSOL Multiphysics v4.0a to concentrate two generic proteins and monitor protein migration through the microchannel. In performing an ITP simulation on this microchip platform, we observe an increase in concentration by over a factor of more than 10,000 due to the combination of ITP stacking and the reduction in cross-sectional area. Two fluorescent proteins, green fluorescent protein and R-phycoerythrin, were used to experimentally visualize ITP through the fabricated microfluidic chip. The initial concentration of each protein in the sample was 1.995 μg/mL and, after preconcentration by ITP, the final concentrations of the two fluorescent proteins were 32.57 ± 3.63 and 22.81 ± 4.61 mg/mL, respectively. Thus, experimentally the two fluorescent proteins were concentrated by over a factor of 10,000 and show good qualitative agreement with our simulation results.
NASA Astrophysics Data System (ADS)
Wachowicz-Pyzik, A.; Sowiżdżał, A.; Pająk, L.
2016-09-01
The numerical modeling enables us to reduce the risk related to the selection of best localization of wells. Moreover, at the stage of production, modeling is a suitable tool for optimization of well operational parameters, which guarantees the long life of doublets. The thorough selection of software together with relevant methodology applied to generation of numerical models significantly improve the quality of obtained results. In the following paper, we discuss the impact of density of calculation grid on the results of geothermal doublet simulation with the TOUGH2 code, which applies the finite-difference method. The study area is located between the Szczecin Trough and the Fore-sudetic Monocline, where the Choszczno IG-1 well has been completed. Our research was divided into the two stages. At the first stage, we examined the changes of density of polygon calculation grids used in computations of operational parameters of geothermal doublets. At the second stage, we analyzed the influence of distance between the production and the injection wells on variability in time of operational parameters. The results demonstrated that in both studied cases, the largest differences occurred in pressures measured in production and injection wells whereas the differences in temperatures were less pronounced.
NASA Technical Reports Server (NTRS)
Baker, John G.
2009-01-01
Recent advances in numerical relativity have fueled an explosion of progress in understanding the predictions of Einstein's theory of gravity, General Relativity, for the strong field dynamics, the gravitational radiation wave forms, and consequently the state of the remnant produced from the merger of compact binary objects. I will review recent results from the field, focusing on mergers of two black holes.
NASA Technical Reports Server (NTRS)
Cabra, R.; Chen, J. Y.; Dibble, R. W.; Myhrvold, T.; Karpetis, A. N.; Barlow, R. S.
2002-01-01
An experiment and numerical investigation is presented of a lifted turbulent H2/N2 jet flame in a coflow of hot, vitiated gases. The vitiated coflow burner emulates the coupling of turbulent mixing and chemical kinetics exemplary of the reacting flow in the recirculation region of advanced combustors. It also simplifies numerical investigation of this coupled problem by removing the complexity of recirculating flow. Scalar measurements are reported for a lifted turbulent jet flame of H2/N2 (Re = 23,600, H/d = 10) in a coflow of hot combustion products from a lean H2/Air flame ((empty set) = 0.25, T = 1,045 K). The combination of Rayleigh scattering, Raman scattering, and laser-induced fluorescence is used to obtain simultaneous measurements of temperature and concentrations of the major species, OH, and NO. The data attest to the success of the experimental design in providing a uniform vitiated coflow throughout the entire test region. Two combustion models (PDF: joint scalar Probability Density Function and EDC: Eddy Dissipation Concept) are used in conjunction with various turbulence models to predict the lift-off height (H(sub PDF)/d = 7,H(sub EDC)/d = 8.5). Kalghatgi's classic phenomenological theory, which is based on scaling arguments, yields a reasonably accurate prediction (H(sub K)/d = 11.4) of the lift-off height for the present flame. The vitiated coflow admits the possibility of auto-ignition of mixed fluid, and the success of the present parabolic implementation of the PDF model in predicting a stable lifted flame is attributable to such ignition. The measurements indicate a thickened turbulent reaction zone at the flame base. Experimental results and numerical investigations support the plausibility of turbulent premixed flame propagation by small scale (on the order of the flame thickness) recirculation and mixing of hot products into reactants and subsequent rapid ignition of the mixture.
NASA Astrophysics Data System (ADS)
Nick, F. M.; Vieli, A.; Pattyn, F.; Van de Wal, R.
2011-12-01
Oceanic forcing has been suggested as a major trigger for dynamic changes of Greenland outlet glaciers. Significant melting near their calving front or beneath the floating tongue and reduced support from sea ice or ice melange in front of their calving front can result in retreat of the terminus or the grounding line, and an increase in calving activities. Depending on the geometry and basal topography of the glacier, these oceanic forcing can affect the glacier dynamic differently. Here, we carry out a comparison study between three major outlet glaciers in Greenland and investigate the impact of a warmer ocean on glacier dynamics and ice discharge. We present results from a numerical ice-flow model applied to Petermann Glacier in the north, Jakobshavn Glacier in the west, and Helheim Glacier in the southeast of Greenland.
NASA Astrophysics Data System (ADS)
Agus, M.; Mascia, M. L.; Fastame, M. C.; Melis, V.; Pilloni, M. C.; Penna, M. P.
2015-02-01
A body of literature shows the significant role of visual-spatial skills played in the improvement of mathematical skills in the primary school. The main goal of the current study was to investigate the impact of a combined visuo-spatial and mathematical training on the improvement of mathematical skills in 146 second graders of several schools located in Italy. Participants were presented single pencil-and-paper visuo-spatial or mathematical trainings, computerised version of the above mentioned treatments, as well as a combined version of computer-assisted and pencil-and-paper visuo-spatial and mathematical trainings, respectively. Experimental groups were presented with training for 3 months, once a week. All children were treated collectively both in computer-assisted or pencil-and-paper modalities. At pre and post-test all our participants were presented with a battery of objective tests assessing numerical and visuo-spatial abilities. Our results suggest the positive effect of different types of training for the empowerment of visuo-spatial and numerical abilities. Specifically, the combination of computerised and pencil-and-paper versions of visuo-spatial and mathematical trainings are more effective than the single execution of the software or of the pencil-and-paper treatment.
Numerical Boundary Condition Procedures
NASA Technical Reports Server (NTRS)
1981-01-01
Topics include numerical procedures for treating inflow and outflow boundaries, steady and unsteady discontinuous surfaces, far field boundaries, and multiblock grids. In addition, the effects of numerical boundary approximations on stability, accuracy, and convergence rate of the numerical solution are discussed.
NASA Technical Reports Server (NTRS)
Cabra, R.; Chen, J. Y.; Dibble, R. W.; Hamano, Y.; Karpetis, A. N.; Barlow, R. S.
2002-01-01
An experimental and numerical investigation is presented of a H2/N2 turbulent jet flame burner that has a novel vitiated coflow. The vitiated coflow emulates the recirculation region of most combustors, such as gas turbines or furnaces. Additionally, since the vitiated gases are coflowing, the burner allows for exploration of recirculation chemistry without the corresponding fluid mechanics of recirculation. Thus the vitiated coflow burner design facilitates the development of chemical kinetic combustion models without the added complexity of recirculation fluid mechanics. Scalar measurements are reported for a turbulent jet flame of H2/N2 in a coflow of combustion products from a lean ((empty set) = 0.25) H2/Air flame. The combination of laser-induced fluorescence, Rayleigh scattering, and Raman scattering is used to obtain simultaneous measurements of the temperature, major species, as well as OH and NO. Laminar flame calculation with equal diffusivity do agree when the premixing and preheating that occurs prior to flame stabilization is accounted for in the boundary conditions. Also presented is an exploratory pdf model that predicts the flame's axial profiles fairly well, but does not accurately predict the lift-off height.
NASA Astrophysics Data System (ADS)
Boerstoel, J. W.
1988-01-01
The current status of a computer program system for the numerical simulation of Euler flows is presented. Preliminary test calculation results are shown. They concern the three-dimensional flow around a wing-nacelle-propeller-outlet configuration. The system is constructed to execute four major tasks: block decomposition of the flow domain around given, possibly complex, three-dimensional aerodynamic surfaces; grid generation on the blocked flow domain; Euler-flow simulation on the blocked grid; and graphical visualization of the computed flow on the blocked grid, and postprocessing. The system consists of about 20 codes interfaced by files. Most of the required tasks can be executed. The geometry of complex aerodynamic surfaces in three-dimensional space can be handled. The validation test showed that the system must be improved to increase the speed of the grid generation process.
2013-01-01
Background Pretreatment of lignocellulosic biomass generates a number of undesired degradation products that can inhibit microbial metabolism. Two of these compounds, the furan aldehydes 5-hydroxymethylfurfural (HMF) and 2-furaldehyde (furfural), have been shown to be an impediment for viable ethanol production. In the present study, HMF and furfural were pulse-added during either the glucose or the xylose consumption phase in order to dissect the effects of these inhibitors on energy state, redox metabolism, and gene expression of xylose-consuming Saccharomyces cerevisiae. Results Pulsed addition of 3.9 g L-1 HMF and 1.2 g L-1 furfural during either the glucose or the xylose consumption phase resulted in distinct physiological responses. Addition of furan aldehydes in the glucose consumption phase was followed by a decrease in the specific growth rate and the glycerol yield, whereas the acetate yield increased 7.3-fold, suggesting that NAD(P)H for furan aldehyde conversion was generated by acetate synthesis. No change in the intracellular levels of NAD(P)H was observed 1 hour after pulsing, whereas the intracellular concentration of ATP increased by 58%. An investigation of the response at transcriptional level revealed changes known to be correlated with perturbations in the specific growth rate, such as protein and nucleotide biosynthesis. Addition of furan aldehydes during the xylose consumption phase brought about an increase in the glycerol and acetate yields, whereas the xylitol yield was severely reduced. The intracellular concentrations of NADH and NADPH decreased by 58 and 85%, respectively, hence suggesting that HMF and furfural drained the cells of reducing power. The intracellular concentration of ATP was reduced by 42% 1 hour after pulsing of inhibitors, suggesting that energy-requiring repair or maintenance processes were activated. Transcriptome profiling showed that NADPH-requiring processes such as amino acid biosynthesis and sulfate and
Zened, A; Enjalbert, F; Nicot, M C; Troegeler-Meynadier, A
2013-01-01
Trans fatty acids (FA), exhibit different biological properties. Among them, cis-9,trans-11 conjugated linoleic acid has some interesting putative health properties, whereas trans-10,cis-12 conjugated linoleic acid has negative effects on cow milk fat production and would negatively affect human health. In high-yielding dairy cows, a shift from trans-11 to trans-10 pathway of biohydrogenation (BH) can occur in the rumen of cows receiving high-concentrate diets, especially when the diet is supplemented with unsaturated fat sources. To study this shift, 4 rumen-fistulated nonlactating Holstein cows were assigned to a 4×4 Latin square design with 4 different diets during 4 periods. Cows received 12 kg of dry matter per day of 4 diets based on corn silage during 4 successive periods: a control diet (22% starch, <3% crude fat on DM basis), a high-starch diet supplemented with wheat plus barley (35% starch, <3% crude fat), a sunflower oil diet supplemented with 5% of sunflower oil (20% starch, 7.6% crude fat), and a high-starch plus sunflower oil diet (33% starch, 7.3% crude fat). Five hours after feeding, proportions of trans-11 BH isomers greatly increased in the rumen content with the addition of sunflower oil, without change in ruminal pH compared with the control diet. Addition of starch to the control diet had no effect on BH pathways but decreased ruminal pH. The addition of a large amount of starch in association with sunflower oil increased trans-10 FA at the expense of trans-11 FA in the rumen content, revealing a trans-11 to trans-10 shift. Interestingly, with this latter diet, ruminal pH did not change compared with a single addition of starch. This trans-11 to trans-10 shift occurred progressively, after a decrease in the proportion of trans-11 FA in the rumen, suggesting that this shift could result from a dysbiosis in the rumen in favor of trans-10-producing bacteria at the expense of those producing trans-11 or a modification of bacterial activities.
Rudolf Keller
2004-08-10
In this project, a concept to improve the performance of aluminum production cells by introducing potlining additives was examined and tested. Boron oxide was added to cathode blocks, and titanium was dissolved in the metal pool; this resulted in the formation of titanium diboride and caused the molten aluminum to wet the carbonaceous cathode surface. Such wetting reportedly leads to operational improvements and extended cell life. In addition, boron oxide suppresses cyanide formation. This final report presents and discusses the results of this project. Substantial economic benefits for the practical implementation of the technology are projected, especially for modern cells with graphitized blocks. For example, with an energy savings of about 5% and an increase in pot life from 1500 to 2500 days, a cost savings of $ 0.023 per pound of aluminum produced is projected for a 200 kA pot.
1996-05-30
Tests were conducted at Southwestern Electric Power Company`s (SWEPCo) Henry W. Pirkey Station wet limestone flue gas desulfurization (FGD) system to evaluate options for achieving high sulfur dioxide removal efficiency. The Pirkey FGD system includes four absorber modules, each with dual slurry recirculation loops and with a perforated plate tray in the upper loop. The options tested involved the use of dibasic acid (DBA) or sodium formate as a performance additive. The effectiveness of other potential options was simulated with the Electric Power Research Institute`s (EPRI) FGD PRocess Integration and Simulation Model (FGDPRISM) after it was calibrated to the system. An economic analysis was done to determine the cost effectiveness of the high-efficiency options. Results are-summarized below.
NASA Astrophysics Data System (ADS)
Mazoyer, Johan; Pueyo, Laurent; Norman, Colin; N'Diaye, Mamadou; van der Marel, Roeland P.; Soummer, Rémi
2016-03-01
The new frontier in the quest for the highest contrast levels in the focal plane of a coronagraph is now the correction of the large diffraction artifacts introduced at the science camera by apertures of increasing complexity. Indeed, the future generation of space- and ground-based coronagraphic instruments will be mounted on on-axis and/or segmented telescopes; the design of coronagraphic instruments for such observatories is currently a domain undergoing rapid progress. One approach consists of using two sequential deformable mirrors (DMs) to correct for aberrations introduced by secondary mirror structures and segmentation of the primary mirror. The coronagraph for the WFIRST-AFTA mission will be the first of such instruments in space with a two-DM wavefront control system. Regardless of the control algorithm for these multiple DMs, they will have to rely on quick and accurate simulation of the propagation effects introduced by the out-of-pupil surface. In the first part of this paper, we present the analytical description of the different approximations to simulate these propagation effects. In Appendix A, we prove analytically that in the special case of surfaces inducing a converging beam, the Fresnel method yields high fidelity for simulations of these effects. We provide numerical simulations showing this effect. In the second part, we use these tools in the framework of the active compensation of aperture discontinuities (ACAD) technique applied to pupil geometries similar to WFIRST-AFTA. We present these simulations in the context of the optical layout of the high-contrast imager for complex aperture telescopes, which will test ACAD on a optical bench. The results of this analysis show that using the ACAD method, an apodized pupil Lyot coronagraph, and the performance of our current DMs, we are able to obtain, in numerical simulations, a dark hole with a WFIRST-AFTA-like. Our numerical simulation shows that we can obtain contrast better than 2×10-9 in
NASA Astrophysics Data System (ADS)
Dubovik, O.; Litvinov, P.; Lapyonok, T.; Herman, M.; Fedorenko, A.; Lopatin, A.; Goloub, P.; Ducos, F.; Aspetsberger, M.; Planer, W.; Federspiel, C.
2013-12-01
During last few years we were developing GRASP (Generalized Retrieval of Aerosol and Surface Properties) algorithm designed for the enhanced characterization of aerosol properties from spectral, multi-angular polarimetric remote sensing observations. The concept of GRASP essentially relies on the accumulated positive research heritage from previous remote sensing aerosol retrieval developments, in particular those from the AERONET and POLDER retrieval activities. The details of the algorithm are described by Dubovik et al. (Atmos. Meas. Tech., 4, 975-1018, 2011). The GRASP retrieves properties of both aerosol and land surface reflectance in cloud-free environments. It is based on highly advanced statistically optimized fitting and deduces nearly 50 unknowns for each observed site. The algorithm derives a similar set of aerosol parameters as AERONET including detailed particle size distribution, the spectrally dependent the complex index of refraction and the fraction of non-spherical particles. The algorithm uses detailed aerosol and surface models and fully accounts for all multiple interactions of scattered solar light with aerosol, gases and the underlying surface. All calculations are done on-line without using traditional look-up tables. In addition, the algorithm uses the new multi-pixel retrieval concept - a simultaneous fitting of a large group of pixels with additional constraints limiting the time variability of surface properties and spatial variability of aerosol properties. This principle is expected to result in higher consistency and accuracy of aerosol products compare to conventional approaches especially over bright surfaces where information content of satellite observations in respect to aerosol properties is limited. The GRASP is a highly versatile algorithm that allows input from both satellite and ground-based measurements. It also has essential flexibility in measurement processing. For example, if observation data set includes spectral
Sebbarand, Nadia; Bockhorn, Henning; Bozzelli, Joseph W
2005-03-17
Oxidation of unsaturated and aromatic hydrocarbons in atmospheric and combustion processes results in formation of linear and cyclic unsaturated, oxygenated-hydrocarbon intermediates. The thermochemical parameters delatafH degrees 298, S degrees 298, and C(p)(f298)(T) for these intermediates are needed to understand their stability and reaction paths in further oxidation. These properties are not available for a majority of these unsaturated oxy-hydrocarbons and their corresponding radicals, even via group additivity methods. Enthalpy, entropy, and heat capacity of a series of 40 oxygenated and non-oxygenated molecules, or radicals corresponding to hydrogen atom loss from the parent stable molecules are determined in this study. Enthalpy (delatafH degrees 298 in kcal mol(-1)) is derived from the density function calculations at the B3LYP/6-311g(d,p) calculated enthalpy of reaction (delatafH degrees rxn,298) and by use of isodesmic (work) reactions. Estimation of error in enthalpy delatafH degrees 298, from use of computational chemistry coupled with work reactions analysis, is presented using comparisons between the calculated and literature enthalpies of reaction. Entropies (S degrees 298) and heat capacities (C(p)(f298)(T)) were calculated using the B3LYP/6-311G(d,p) determined frequencies and geometries. Potential barriers for internal rotors in each molecule were determined and used (in place of torsion frequencies) to calculate contributions to S and C(p)(T) from the hindered rotors. Twenty-six groups for use in group additivity (GA) are also developed.
Gregoire, C.; Joesten, P.K.; Lane, J.W.
2006-01-01
Ground penetrating radar is an efficient geophysical method for the detection and location of fractures and fracture zones in electrically resistive rocks. In this study, the use of down-hole (borehole) radar reflection logs to monitor the injection of steam in fractured rocks was tested as part of a field-scale, steam-enhanced remediation pilot study conducted at a fractured limestone quarry contaminated with chlorinated hydrocarbons at the former Loring Air Force Base, Limestone, Maine, USA. In support of the pilot study, borehole radar reflection logs were collected three times (before, during, and near the end of steam injection) using broadband 100 MHz electric dipole antennas. Numerical modelling was performed to predict the effect of heating on radar-frequency electromagnetic (EM) wave velocity, attenuation, and fracture reflectivity. The modelling results indicate that EM wave velocity and attenuation change substantially if heating increases the electrical conductivity of the limestone matrix. Furthermore, the net effect of heat-induced variations in fracture-fluid dielectric properties on average medium velocity is insignificant because the expected total fracture porosity is low. In contrast, changes in fracture fluid electrical conductivity can have a significant effect on EM wave attenuation and fracture reflectivity. Total replacement of water by steam in a fracture decreases fracture reflectivity of a factor of 10 and induces a change in reflected wave polarity. Based on the numerical modelling results, a reflection amplitude analysis method was developed to delineate fractures where steam has displaced water. Radar reflection logs collected during the three acquisition periods were analysed in the frequency domain to determine if steam had replaced water in the fractures (after normalizing the logs to compensate for differences in antenna performance between logging runs). Analysis of the radar reflection logs from a borehole where the temperature
NASA Technical Reports Server (NTRS)
Iguchi, Takamichi; Matsui, Toshihisa; Shi, Jainn J.; Tao, Wei-Kuo; Khain, Alexander P.; Hao, Arthur; Cifelli, Robert; Heymsfield, Andrew; Tokay, Ali
2012-01-01
Two distinct snowfall events are observed over the region near the Great Lakes during 19-23 January 2007 under the intensive measurement campaign of the Canadian CloudSat/CALIPSO validation project (C3VP). These events are numerically investigated using the Weather Research and Forecasting model coupled with a spectral bin microphysics (WRF-SBM) scheme that allows a smooth calculation of riming process by predicting the rimed mass fraction on snow aggregates. The fundamental structures of the observed two snowfall systems are distinctly characterized by a localized intense lake-effect snowstorm in one case and a widely distributed moderate snowfall by the synoptic-scale system in another case. Furthermore, the observed microphysical structures are distinguished by differences in bulk density of solid-phase particles, which are probably linked to the presence or absence of supercooled droplets. The WRF-SBM coupled with Goddard Satellite Data Simulator Unit (G-SDSU) has successfully simulated these distinctive structures in the three-dimensional weather prediction run with a horizontal resolution of 1 km. In particular, riming on snow aggregates by supercooled droplets is considered to be of importance in reproducing the specialized microphysical structures in the case studies. Additional sensitivity tests for the lake-effect snowstorm case are conducted utilizing different planetary boundary layer (PBL) models or the same SBM but without the riming process. The PBL process has a large impact on determining the cloud microphysical structure of the lake-effect snowstorm as well as the surface precipitation pattern, whereas the riming process has little influence on the surface precipitation because of the small height of the system.
NASA Technical Reports Server (NTRS)
Benyo, Theresa L.
2011-01-01
Flow matching has been successfully achieved for an MHD energy bypass system on a supersonic turbojet engine. The Numerical Propulsion System Simulation (NPSS) environment helped perform a thermodynamic cycle analysis to properly match the flows from an inlet employing a MHD energy bypass system (consisting of an MHD generator and MHD accelerator) on a supersonic turbojet engine. Working with various operating conditions (such as the applied magnetic field, MHD generator length and flow conductivity), interfacing studies were conducted between the MHD generator, the turbojet engine, and the MHD accelerator. This paper briefly describes the NPSS environment used in this analysis. This paper further describes the analysis of a supersonic turbojet engine with an MHD generator/accelerator energy bypass system. Results from this study have shown that using MHD energy bypass in the flow path of a supersonic turbojet engine increases the useful Mach number operating range from 0 to 3.0 Mach (not using MHD) to a range of 0 to 7.0 Mach with specific net thrust range of 740 N-s/kg (at ambient Mach = 3.25) to 70 N-s/kg (at ambient Mach = 7). These results were achieved with an applied magnetic field of 2.5 Tesla and conductivity levels in a range from 2 mhos/m (ambient Mach = 7) to 5.5 mhos/m (ambient Mach = 3.5) for an MHD generator length of 3 m.
Sullivan, A; Ding, G
2015-06-15
Purpose: The use of image-guided radiation therapy (IGRT) has become increasingly common, but the additional radiation exposure resulting from repeated image guidance procedures raises concerns. Although there are many studies reporting imaging dose from different image guidance devices, imaging dose for the CyberKnife Robotic Radiosurgery System is not available. This study provides estimated organ doses resulting from image guidance procedures on the CyberKnife system. Methods: Commercially available Monte Carlo software, PCXMC, was used to calculate average organ doses resulting from x-ray tubes used in the CyberKnife system. There are seven imaging protocols with kVp ranging from 60 – 120 kV and 15 mAs for treatment sites in the Cranium, Head and Neck, Thorax, and Abdomen. The output of each image protocol was measured at treatment isocenter. For each site and protocol, Adult body sizes ranging from anorexic to extremely obese were simulated since organ dose depends on patient size. Doses for all organs within the imaging field-of-view of each site were calculated for a single image acquisition from both of the orthogonal x-ray tubes. Results: Average organ doses were <1.0 mGy for every treatment site and imaging protocol. For a given organ, dose increases as kV increases or body size decreases. Higher doses are typically reported for skeletal components, such as the skull, ribs, or clavicles, than for softtissue organs. Typical organ doses due to a single exposure are estimated as 0.23 mGy to the brain, 0.29 mGy to the heart, 0.08 mGy to the kidneys, etc., depending on the imaging protocol and site. Conclusion: The organ doses vary with treatment site, imaging protocol and patient size. Although the organ dose from a single image acquisition resulting from two orthogonal beams is generally insignificant, the sum of repeated image acquisitions (>100) could reach 10–20 cGy for a typical treatment fraction.
2010-01-01
Background Hypertriglyceridemia (HTG) is a well-established independent risk factor for cardiovascular disease and the influence of several genetic variants in genes related with triglyceride (TG) metabolism has been described, including LPL, APOA5 and APOE. The combined analysis of these polymorphisms could produce clinically meaningful complementary information. Methods A subgroup of the ICARIA study comprising 1825 Spanish subjects (80% men, mean age 36 years) was genotyped for the LPL-HindIII (rs320), S447X (rs328), D9N (rs1801177) and N291S (rs268) polymorphisms, the APOA5-S19W (rs3135506) and -1131T/C (rs662799) variants, and the APOE polymorphism (rs429358; rs7412) using PCR and restriction analysis and TaqMan assays. We used regression analyses to examine their combined effects on TG levels (with the log-transformed variable) and the association of variant combinations with TG levels and hypertriglyceridemia (TG ≥ 1.69 mmol/L), including the covariates: gender, age, waist circumference, blood glucose, blood pressure, smoking and alcohol consumption. Results We found a significant lowering effect of the LPL-HindIII and S447X polymorphisms (p < 0.0001). In addition, the D9N, N291S, S19W and -1131T/C variants and the APOE-ε4 allele were significantly associated with an independent additive TG-raising effect (p < 0.05, p < 0.01, p < 0.001, p < 0.0001 and p < 0.001, respectively). Grouping individuals according to the presence of TG-lowering or TG-raising polymorphisms showed significant differences in TG levels (p < 0.0001), with the lowest levels exhibited by carriers of two lowering variants (10.2% reduction in TG geometric mean with respect to individuals who were homozygous for the frequent alleles of all the variants), and the highest levels in carriers of raising combinations (25.1% mean TG increase). Thus, carrying two lowering variants was protective against HTG (OR = 0.62; 95% CI, 0.39-0.98; p = 0.042) and having one single raising polymorphism (OR
Murphy, J.
1997-02-14
Tests were conducted at New York State Gas & Electric`s (NYSEG`s) Kintigh Station to evaluate options for achieving high sulfur dioxide (SO{sub 2}) removal efficiency in the wet limestone flue gas desulfurization (FGD) system. This test program was one of six conducted by the U.S. Department of Energy to evaluate low-capital-cost upgrades to existing FGD systems as a means for utilities to comply with the requirements of the 1990 Clean Air Act Amendments. The upgrade option tested at Kintigh was sodium formate additive. Results from the tests were used to calibrate the Electric Power Research Institute`s (EPRI) FGD PRocess Integration and Simulation Model (FGDPRISM) to the Kintigh scrubber configuration. FGDPRISM was then used to predict system performance for evaluating conditions other than those tested. An economic evaluation was then done to determine the cost effectiveness of various high-efficiency upgrade options. These costs can be compared with the estimated market value of SO{sub 2} allowance or the expected costs of allowances generated by other means, such as fuel switching or new scrubbers, to arrive at the most cost-effective strategy for Clean Air Act compliance.
Beaudoin, Trevor; Lafayette, Shantelle; Nguyen, Dao; Rousseau, Simon
2012-11-09
The presence of the mucoid phenotype of Pseudomonas aeruginosa is a marker of poor survival in cystic fibrosis. As CF lung disease results from chronic infection leading to airway inflammation, we determined whether the switch to a mucoid phenotype by P. aeruginosa has an impact on the inflammatory response of airway epithelial cells. Exposure of airway epithelial cells to non-mucoid and mucoid P. aeruginosa-derived material leads to p38α MAPK activation, a key protein kinase involved in transmitting inflammatory signals. However, while the non-mucoid strain PAO1 activates p38α MAPK pathway solely via TLR5, the mucoid strain PACF508 activates p38α MAPK via both TLR5 and TLR2. Inactivation of mucA (the gene responsible for the mucoid phenotype) in PAO1 leads to p38α MAPK activation by both TLR2 and TLR5, as observed in the clinical mucoid isolate PACF508. Therefore, the switch to mucoid phenotype may contribute to more inflammation via TLR2 activation in addition to TLR5. Our findings highlight an important and under recognized role for TLR2 in the response of airway epithelial cells to infection.
NASA Technical Reports Server (NTRS)
Witte, J. C.; Thompson, A. M.; Schmidlin, F. J.; Oltmans, S. J.; McPeters, R. D.; Smit, H. G. J.
2003-01-01
A network of 12 southern hemisphere tropical and subtropical stations in the Southern Hemisphere ADditional OZonesondes (SHADOZ) project has provided over 2000 profiles of stratospheric and tropospheric ozone since 1998. Balloon-borne electrochemical concentration cell (ECC) ozonesondes are used with standard radiosondes for pressure, temperature and relative humidity measurements. The archived data are available at:http: //croc.gsfc.nasa.gov/shadoz. In Thompson et al., accuracies and imprecisions in the SHADOZ 1998- 2000 dataset were examined using ground-based instruments and the TOMS total ozone measurement (version 7) as references. Small variations in ozonesonde technique introduced possible biases from station-to-station. SHADOZ total ozone column amounts are now compared to version 8 TOMS; discrepancies between the two datasets are reduced 2\\% on average. An evaluation of ozone variations among the stations is made using the results of a series of chamber simulations of ozone launches (JOSIE-2000, Juelich Ozonesonde Intercomparison Experiment) in which a standard reference ozone instrument was employed with the various sonde techniques used in SHADOZ. A number of variations in SHADOZ ozone data are explained when differences in solution strength, data processing and instrument type (manufacturer) are taken into account.
Lin, Heng-Teng; Chiu, Chong-Chi; Wang, Jhi-Joung; Hung, Ching-Hsia; Chen, Yu-Wen
2015-03-04
The impact of coadministration of transcutaneous electrical nerve stimulation (TENS) and diphenidol is not well established. Here we estimated the effects of diphenidol in combination with TENS on mechanical allodynia and tumor necrosis factor-α (TNF-α) expression. Using an animal chronic constriction injury (CCI) model, the rat was estimated for evidence of mechanical sensitivity via von Frey hair stimulation and TNF-α expression in the sciatic nerve using the ELISA assay. High frequency (100Hz) TENS or intraperitoneal injection of diphenidol (2.0μmol/kg) was applied daily, starting on postoperative day 1 (POD1) and lasting for the next 13 days. We demonstrated that both high frequency TENS and diphenidol groups had an increase in mechanical withdrawal thresholds of 60%. Coadministration of high frequency TENS and diphenidol gives better results of paw withdrawal thresholds in comparison with high frequency TENS alone or diphenidol alone. Both diphenidol and coadministration of high frequency TENS with diphenidol groups showed a significant reduction of the TNF-α level compared with the CCI or HFS group (P<0.05) in the sciatic nerve on POD7, whereas the CCI or high frequency TENS group exhibited a higher TNF-α level than the sham group (P<0.05). Our resulting data revealed that diphenidol alone, high frequency TENS alone, and the combination produced a reduction of neuropathic allodynia. Both diphenidol and the combination of diphenidol with high frequency TENS inhibited TNF-α expression. A moderately effective dose of diphenidol appeared to have an additive effect with high frequency TENS. Therefore, multidisciplinary treatments could be considered for this kind of mechanical allodynia.
NASA Technical Reports Server (NTRS)
Benyo, Theresa L.
2010-01-01
Preliminary flow matching has been demonstrated for a MHD energy bypass system on a supersonic turbojet engine. The Numerical Propulsion System Simulation (NPSS) environment was used to perform a thermodynamic cycle analysis to properly match the flows from an inlet to a MHD generator and from the exit of a supersonic turbojet to a MHD accelerator. Working with various operating conditions such as the enthalpy extraction ratio and isentropic efficiency of the MHD generator and MHD accelerator, interfacing studies were conducted between the pre-ionizers, the MHD generator, the turbojet engine, and the MHD accelerator. This paper briefly describes the NPSS environment used in this analysis and describes the NPSS analysis of a supersonic turbojet engine with a MHD generator/accelerator energy bypass system. Results from this study have shown that using MHD energy bypass in the flow path of a supersonic turbojet engine increases the useful Mach number operating range from 0 to 3.0 Mach (not using MHD) to an explored and desired range of 0 to 7.0 Mach.
Vafaeian, B; Le, L H; Tran, T N H T; El-Rich, M; El-Bialy, T; Adeeb, S
2016-05-01
The present study investigated the accuracy of micro-scale finite element modeling for simulating broadband ultrasound propagation in water-saturated trabecular bone-mimicking phantoms. To this end, five commercially manufactured aluminum foam samples as trabecular bone-mimicking phantoms were utilized for ultrasonic immersion through-transmission experiments. Based on micro-computed tomography images of the same physical samples, three-dimensional high-resolution computational samples were generated to be implemented in the micro-scale finite element models. The finite element models employed the standard Galerkin finite element method (FEM) in time domain to simulate the ultrasonic experiments. The numerical simulations did not include energy dissipative mechanisms of ultrasonic attenuation; however, they expectedly simulated reflection, refraction, scattering, and wave mode conversion. The accuracy of the finite element simulations were evaluated by comparing the simulated ultrasonic attenuation and velocity with the experimental data. The maximum and the average relative errors between the experimental and simulated attenuation coefficients in the frequency range of 0.6-1.4 MHz were 17% and 6% respectively. Moreover, the simulations closely predicted the time-of-flight based velocities and the phase velocities of ultrasound with maximum relative errors of 20 m/s and 11 m/s respectively. The results of this study strongly suggest that micro-scale finite element modeling can effectively simulate broadband ultrasound propagation in water-saturated trabecular bone-mimicking structures.
NASA Astrophysics Data System (ADS)
Eberts, S.; Bohlke, J. K.
2009-12-01
Estimates of groundwater age distributions at public-supply wells can provide insight into the vulnerability of these wells to contamination. Such estimates can be used to explore past and future water-quality trends and contaminant peak concentrations when combined with information on contaminant input at the water table. Information on groundwater age distributions, however, is not routinely applied to water quality issues at public-supply wells. This may be due, in part, to the difficulty in obtaining such estimates from poorly characterized aquifers with limited environmental tracer data. To this end, we compared distributions of groundwater ages in discharge from public-supply wells estimated from age tracer data (SF6, CFCs, 3H, 3He) using two different inverse modeling approaches: relatively simple lumped parameter models and more complex distributed-parameter numerical flow models with particle tracking. These comparisons were made in four contrasting hydrogeologic settings across the United States: unconsolidated alluvial fan sediments, layered confined unconsolidated sediments, unconsolidated valley-fill sediments, and carbonate rocks. In all instances, multiple age tracer measurements for the public-supply well of interest were available. We compared the following quantities, which were derived from simulated breakthrough curves that were generated using the various estimated age distributions for the selected wells and assuming the same hypothetical contaminant input: time lag to peak concentration, dilution at peak concentration, and contaminant arrival and flush times. Apparent tracer-based ages and mean and median simulated ages also were compared. For each setting, both types of models yielded similar age distributions and concentration trends, when based on similar conceptual models of local hydrogeology and calibrated to the same tracer measurements. Results indicate carefully chosen and calibrated simple lumped parameter age distribution models
NASA Astrophysics Data System (ADS)
Sarkadi, N.; Geresdi, I.; Thompson, G.
2016-11-01
In this study, results of bulk and bin microphysical schemes are compared in the case of idealized simulations of pre-frontal orographic clouds with enhanced embedded convection. The description graupel formation by intensive riming of snowflakes was improved compared to prior versions of each scheme. Two methods of graupel melting coincident with collisions with water drops were considered: (1) all simulated melting and collected water drops increase the amount of melted water on the surface of graupel particles with no shedding permitted; (2) also no shedding permitted due to melting, but the collision with the water drops can induce shedding from the surface of the graupel particles. The results of the numerical experiments show: (i) The bin schemes generate graupel particles more efficiently by riming than the bulk scheme does; the intense riming of snowflakes was the most dominant process for the graupel formation. (ii) The collision-induced shedding significantly affects the evolution of the size distribution of graupel particles and water drops below the melting level. (iii) The three microphysical schemes gave similar values for the domain integrated surface precipitation, but the patterns reveal meaningful differences. (iv) Sensitivity tests using the bulk scheme show that the depth of the melting layer is sensitive to the description of the terminal velocity of the melting snow. (v) Comparisons against Convair-580 flight measurements suggest that the bin schemes simulate well the evolution of the pristine ice particles and liquid drops, while some inaccuracy can occur in the description of snowflakes riming. (vi) The bin scheme with collision-induced shedding reproduced well the quantitative characteristics of the observed bright band.
NASA Technical Reports Server (NTRS)
Gomberg, Joan; Ellis, Michael
1994-01-01
We present results of a series of numerical experiments designed to test hypothetical mechanisms that derive deformation in the New Madrid seismic zone. Experiments are constrained by subtle topography and the distribution of seismicity in the region. We use a new boundary element algorithm that permits calcuation of the three-dimensional deformation field. Surface displacement fields are calculated for the New Madrid zone under both far-field (plate tectonics scale) and locally derived driving strains. Results demonstrate that surface displacement fields cannot distinguish between either a far-field simple or pure shear strain field or one that involves a deep shear zone beneath the upper crustal faults. Thus, neither geomorphic nor geodetic studies alone are expected to reveal the ultimate driving mechanism behind the present-day deformation. We have also tested hypotheses about strain accommodation within the New Madrid contractional step-over by including linking faults, two southwest dipping and one vertical, recently inferred from microearthquake data. Only those models with step-over faults are able to predict the observed topography. Surface displacement fields for long-term, relaxed deformation predict the distribution of uplift and subsidence in the contractional step-over remarkably well. Generation of these displacement fields appear to require slip on both the two northeast trending vertical faults and the two dipping faults in the step-over region, with very minor displacements occurring during the interseismic period when the northeast trending vertical faults are locked. These models suggest that the gently dippling central step-over fault is a reverse fault and that the steeper fault, extending to the southeast of the step-over, acts as a normal fault over the long term.
NASA Astrophysics Data System (ADS)
Dordevic, Mladen; Georgen, Jennifer
2016-03-01
Mantle plumes rising in the vicinity of mid-ocean ridges often generate anomalies in melt production and seafloor depth. This study investigates the dynamical interactions between a mantle plume and a ridge-ridge-ridge triple junction, using a parameter space approach and a suite of steady state, three-dimensional finite element numerical models. The top domain boundary is composed of three diverging plates, with each assigned half-spreading rates with respect to a fixed triple junction point. The bottom boundary is kept at a constant temperature of 1350°C except where a two-dimensional, Gaussian-shaped thermal anomaly simulating a plume is imposed. Models vary plume diameter, plume location, the viscosity contrast between plume and ambient mantle material, and the use of dehydration rheology in calculating viscosity. Importantly, the model results quantify how plume-related anomalies in mantle temperature pattern, seafloor depth, and crustal thickness depend on the specific set of parameters. To provide an example, one way of assessing the effect of conduit position is to calculate normalized area, defined to be the spatial dispersion of a given plume at specific depth (here selected to be 50 km) divided by the area occupied by the same plume when it is located under the triple junction. For one particular case modeled where the plume is centered in an intraplate position 100 km from the triple junction, normalized area is just 55%. Overall, these models provide a framework for better understanding plateau formation at triple junctions in the natural setting and a tool for constraining subsurface geodynamical processes and plume properties.
Wójcik, J; Kujawska, T; Nowicki, A; Lewin, P A
2008-12-01
The primary goal of this work was to verify experimentally the applicability of the recently introduced time-averaged wave envelope (TAWE) method [J. Wójcik, A. Nowicki, P.A. Lewin, P.E. Bloomfield, T. Kujawska, L. Filipczyński, Wave envelopes method for description of nonlinear acoustic wave propagation, Ultrasonics 44 (2006) 310-329.] as a tool for fast prediction of four dimensional (4D) pulsed nonlinear pressure fields from arbitrarily shaped acoustic sources in attenuating media. The experiments were performed in water at the fundamental frequency of 2.8 MHz for spherically focused (focal length F=80 mm) square (20 x 20 mm) and rectangular (10 x 25mm) sources similar to those used in the design of 1D linear arrays operating with ultrasonic imaging systems. The experimental results obtained with 10-cycle tone bursts at three different excitation levels corresponding to linear, moderately nonlinear and highly nonlinear propagation conditions (0.045, 0.225 and 0.45 MPa on-source pressure amplitude, respectively) were compared with those yielded using the TAWE approach [J. Wójcik, A. Nowicki, P.A. Lewin, P.E. Bloomfield, T. Kujawska, L. Filipczyński, Wave envelopes method for description of nonlinear acoustic wave propagation, Ultrasonics 44 (2006) 310-329.]. The comparison of the experimental results and numerical simulations has shown that the TAWE approach is well suited to predict (to within+/-1 dB) both the spatial-temporal and spatial-spectral pressure variations in the pulsed nonlinear acoustic beams. The obtained results indicated that implementation of the TAWE approach enabled shortening of computation time in comparison with the time needed for prediction of the full 4D pulsed nonlinear acoustic fields using a conventional (Fourier-series) approach [P.T. Christopher, K.J. Parker, New approaches to nonlinear diffractive field propagation, J. Acoust. Soc. Am. 90 (1) (1991) 488-499.]. The reduction in computation time depends on several parameters
Spencer, Michael
1974-01-01
Food additives are discussed from the food technology point of view. The reasons for their use are summarized: (1) to protect food from chemical and microbiological attack; (2) to even out seasonal supplies; (3) to improve their eating quality; (4) to improve their nutritional value. The various types of food additives are considered, e.g. colours, flavours, emulsifiers, bread and flour additives, preservatives, and nutritional additives. The paper concludes with consideration of those circumstances in which the use of additives is (a) justified and (b) unjustified. PMID:4467857
Orth, R.J.; Zacher, A.H.; Schmidt, A.J.; Elmore, M.R.; Elliott, K.R.; Neuenschwander, G.G.; Gano, S.R.
1995-09-01
Chelating organics and some of their degradation products in the Hanford tank waste, such as EDTA, HEDTA, and NTA act to solubilize strontium and transuranics (TRU) in the tank waste supernatant. Displacement of strontium and TRU will facilitate the removal of these radionuclides via precipitation/filtration, ion exchange, or solvent extraction so that low-level waste feed specifications can be met. Pacific Northwest Laboratory has investigated two methods for releasing organic-complexed strontium and TRU components to allow for effective pretreatment of tank waste supernatant: metal cation addition (to promote displacement and flocculation) and chemical oxidant (pennanganate) addition (to promote chelator destruction/defunctionalization and possibly flocculation). These methods, which can be conducted at near-ambient. temperatures and pressures, could be deployed as intank processes.
ERIC Educational Resources Information Center
Goold, Vernell C.
1977-01-01
Numerical control (a technique involving coded, numerical instructions for the automatic control and performance of a machine tool) does not replace fundamental machine tool training. It should be added to the training program to give the student an additional tool to accomplish production rates and accuracy that were not possible before. (HD)
NASA Astrophysics Data System (ADS)
El-Asrag, Hossam A.; Ju, Yiguang
2013-04-01
Direct numerical simulations (DNSs) of a stratified flow in a homogeneous compression charge ignition (HCCI) engine are performed to investigate the exhaust gas recirculation (EGR) and temperature/mixture stratification effects on the autoignition of synthetic dimethyl ether (DME) in the negative temperature combustion region. Detailed chemistry for a DME/air mixture is employed and solved by a hybrid multi-time scale (HMTS) algorithm to reduce the computational cost. The effect of ? to mimic the EGR effect on autoignition are studied. The results show that adding ? enhances autoignition by rapid OH radical pool formation (34-46% reduction in ignition delay time) and changes the ignition heat release rates at different ignition stages. Sensitivity analysis is performed and the important reactions pathways affecting the autoignition are specified. The DNS results show that the scales introduced by thermal and mixture stratifications have a strong effect after the low temperature chemistry (LTC) ignition especially at the locations of high scalar dissipation rates. Compared to homogenous ignition, stratified ignitions show similar first autoignition delay times, but 18% reduction in the second and third ignition delay times. The results also show that molecular transport plays an important role in stratified low temperature ignition, and that the scalar mixing time scale is strongly affected by local ignition in the stratified flow. Two ignition-kernel propagation modes are observed: a wave-like, low-speed, deflagrative mode and a spontaneous, high-speed, ignition mode. Three criteria are introduced to distinguish these modes by different characteristic time scales and Damkhöler numbers using a progress variable conditioned by an ignition kernel indicator. The low scalar dissipation rate flame front is characterized by high displacement speeds and high mixing Damkhöler number. The proposed criteria are applied successfully at the different ignition stages and
... or natural. Natural food additives include: Herbs or spices to add flavor to foods Vinegar for pickling ... Certain colors improve the appearance of foods. Many spices, as well as natural and man-made flavors, ...
Hughes, M S; Marsh, J N; Wickline, S A; McCarthy, J E
2015-01-01
Previous results on the use of joint entropy for detection of targeted nanoparticles accumulating in the neovasculature of MDA435 tumors [Fig. 7 of M. S. Hughes et al., J. Acoust. Soc. Am. 133, 283-300 (2013)] are extended, with sensitivity improving by nearly another factor of 2. This result is obtained using a "quasi-optimal" reference waveform in the computation of the joint entropy imaging technique used to image the accumulating nanoparticles.
Franke, O. Lehn; Reilly, Thomas E.
1987-01-01
The most critical and difficult aspect of defining a groundwater system or problem for conceptual analysis or numerical simulation is the selection of boundary conditions . This report demonstrates the effects of different boundary conditions on the steady-state response of otherwise similar ground-water systems to a pumping stress. Three series of numerical experiments illustrate the behavior of three hypothetical groundwater systems that are rectangular sand prisms with the same dimensions but with different combinations of constant-head, specified-head, no-flow, and constant-flux boundary conditions. In the first series of numerical experiments, the heads and flows in all three systems are identical, as are the hydraulic conductivity and system geometry . However, when the systems are subjected to an equal stress by a pumping well in the third series, each differs significantly in its response . The highest heads (smallest drawdowns) and flows occur in the systems most constrained by constant- or specified-head boundaries. These and other observations described herein are important in steady-state calibration, which is an integral part of simulating many ground-water systems. Because the effects of boundary conditions on model response often become evident only when the system is stressed, a close match between the potential distribution in the model and that in the unstressed natural system does not guarantee that the model boundary conditions correctly represent those in the natural system . In conclusion, the boundary conditions that are selected for simulation of a ground-water system are fundamentally important to groundwater systems analysis and warrant continual reevaluation and modification as investigation proceeds and new information and understanding are acquired.
Lindberg, Ulrika; Carlsson, Malin; Hellmark, Thomas; Segelmark, Mårten
2015-01-01
Patients with cystic fibrosis (CF) colonized with Pseudomonas aeruginosa (P. aeruginosa) have worse prognosis compared with patients who are not. BPI-ANCA is an anti-neutrophil cytoplasmic antibody against BPI (bactericidal/permeability increasing protein) correlating with P. aeruginosa colonization and adverse long time prognosis. Whether it provides additional information as compared to standard anti-P. aeruginosa serology tests is not known. 117 nontransplanted CF patients at the CF centre in Lund, Sweden, were followed prospectively for ten years. Bacterial colonisation was classified according to the Leeds criteria. IgA BPI-ANCA was compared with assays for antibodies against alkaline protease (AP), Elastase (ELA), and Exotoxin A (ExoA). Lung function and patient outcome, alive, lung transplanted, or dead, were registered. BPI-ANCA showed the highest correlation with lung function impairment with an r-value of 0.44. Forty-eight of the 117 patients were chronically colonized with P. aeruginosa. Twenty of these patients experienced an adverse outcome. Receiver operator curve (ROC) analysis revealed that this could be predicted by BPI-ANCA (AUC = 0.77), (p = 0.002) to a better degree compared with serology tests. BPI-ANCA correlates better with lung function impairment and long time prognosis than anti-P. aeruginosa serology and has similar ability to identify patients with chronic P. aeruginosa.
Serafino, Francesco; Lugni, Claudio; Nieto Borge, Josè Carlos; Soldovieri, Francesco
2011-01-01
For moderate and high speed values of the sea surface current, an aliasing phenomenon, due to an under-sampling in the time-domain, can strongly affect the reconstruction of the sea surface elevation derived from X-band radar images. Here, we propose a de-aliasing strategy that exploits the physical information provided by the dispersion law for gravity waves. In particular, we utilize simplifying hypotheses and numerical tests with synthetic data are presented to demonstrate the effectiveness of the presented method. PMID:22346616
NASA Astrophysics Data System (ADS)
Boerstoel, J. W.
1988-12-01
A framework is provided for numerical accuracy assessment. The purpose of numerical flow simulations is formulated. This formulation concerns the classes of aeronautical configurations (boundaries), the desired flow physics (flow equations and their properties), the classes of flow conditions on flow boundaries (boundary conditions), and the initial flow conditions. Next, accuracy and economical performance requirements are defined; the final numerical flow simulation results of interest should have a guaranteed accuracy, and be produced for an acceptable FLOP-price. Within this context, the validation of numerical processes with respect to the well known topics of consistency, stability, and convergence when the mesh is refined must be done by numerical experimentation because theory gives only partial answers. This requires careful design of text cases for numerical experimentation. Finally, the results of a few recent evaluation exercises of numerical experiments with a large number of codes on a few test cases are summarized.
Rule, Simon; Smith, Paul; Johnson, Peter W.M.; Bolam, Simon; Follows, George; Gambell, Joanne; Hillmen, Peter; Jack, Andrew; Johnson, Stephen; Kirkwood, Amy A; Kruger, Anton; Pocock, Christopher; Seymour, John F.; Toncheva, Milena; Walewski, Jan; Linch, David
2016-01-01
Mantle cell lymphoma is an incurable and generally aggressive lymphoma that is more common in elderly patients. Whilst a number of different chemotherapeutic regimens are active in this disease, there is no established gold standard therapy. Rituximab has been used widely to good effect in B-cell malignancies but there is no evidence that it improves outcomes when added to chemotherapy in this disease. We performed a randomized, open-label, multicenter study looking at the addition of rituximab to the standard chemotherapy regimen of fludarabine and cyclophosphamide in patients with newly diagnosed mantle cell lymphoma. A total of 370 patients were randomized. With a median follow up of six years, rituximab improved the median progression-free survival from 14.9 to 29.8 months (P<0.001) and overall survival from 37.0 to 44.5 months (P=0.005). This equates to absolute differences of 9.0% and 22.1% for overall and progression-free survival, respectively, at two years. Overall response rates were similar, but complete response rates were significantly higher in the rituximab arm: 52.7% vs. 39.9% (P=0.014). There was no clinically significant additional toxicity observed with the addition of rituximab. Overall, approximately 18% of patients died of non-lymphomatous causes, most commonly infections. The addition of rituximab to fludarabine and cyclophosphamide chemotherapy significantly improves outcomes in patients with mantle cell lymphoma. However, these regimens have significant late toxicity and should be used with caution. This trial has been registered (ISRCTN81133184 and clinicaltrials.gov:00641095) and is supported by the UK National Cancer Research Network. PMID:26611473
Rule, Simon; Smith, Paul; Johnson, Peter W M; Bolam, Simon; Follows, George; Gambell, Joanne; Hillmen, Peter; Jack, Andrew; Johnson, Stephen; Kirkwood, Amy A; Kruger, Anton; Pocock, Christopher; Seymour, John F; Toncheva, Milena; Walewski, Jan; Linch, David
2016-02-01
Mantle cell lymphoma is an incurable and generally aggressive lymphoma that is more common in elderly patients. Whilst a number of different chemotherapeutic regimens are active in this disease, there is no established gold standard therapy. Rituximab has been used widely to good effect in B-cell malignancies but there is no evidence that it improves outcomes when added to chemotherapy in this disease. We performed a randomized, open-label, multicenter study looking at the addition of rituximab to the standard chemotherapy regimen of fludarabine and cyclophosphamide in patients with newly diagnosed mantle cell lymphoma. A total of 370 patients were randomized. With a median follow up of six years, rituximab improved the median progression-free survival from 14.9 to 29.8 months (P<0.001) and overall survival from 37.0 to 44.5 months (P=0.005). This equates to absolute differences of 9.0% and 22.1% for overall and progression-free survival, respectively, at two years. Overall response rates were similar, but complete response rates were significantly higher in the rituximab arm: 52.7% vs. 39.9% (P=0.014). There was no clinically significant additional toxicity observed with the addition of rituximab. Overall, approximately 18% of patients died of non-lymphomatous causes, most commonly infections. The addition of rituximab to fludarabine and cyclophosphamide chemotherapy significantly improves outcomes in patients with mantle cell lymphoma. However, these regimens have significant late toxicity and should be used with caution. This trial has been registered (ISRCTN81133184 and clinicaltrials.gov:00641095) and is supported by the UK National Cancer Research Network.
ERIC Educational Resources Information Center
Siegler, Robert S.; Braithwaite, David W.
2016-01-01
In this review, we attempt to integrate two crucial aspects of numerical development: learning the magnitudes of individual numbers and learning arithmetic. Numerical magnitude development involves gaining increasingly precise knowledge of increasing ranges and types of numbers: from non-symbolic to small symbolic numbers, from smaller to larger…
ERIC Educational Resources Information Center
Bright, William
In most languages encountered by linguists, the numerals, considered as a paradigmatic set, constitute a morpho-syntactic problem of only moderate complexity. The Indo-Aryan language family of North India, however, presents a curious contrast. The relatively regular numeral system of Sanskrit, as it has developed historically into the modern…
Pauling, Linus
1977-01-01
A general theory of the structure of complexes of the transition metals is developed on the basis of the enneacovalence of the metals and the requirements of the electroneutrality principle. An extra orbital may be provided through the small but not negligible amount of f and g character of spd bond orbitals, and an extra electron or electron pair may be accepted in this orbital for a single metal or a cluster to neutralize the positive electric charge resulting from the partial ionic character of the bonds with ligands, such as the carbonyl group. Examples of cluster compounds of cobalt, ruthenium, rhodium, osmium, and gold are discussed. PMID:16592470
Zhao, Chong-Ke; Xu, Hui-Xiong; Xu, Jun-Mei; Sun, Cheng-Yu; Chen, Wei; Liu, Bo-Ji; Bo, Xiao-Wan; Wang, Dan; Qu, Shen
2017-01-01
To assess the value of conventional ultrasound, conventional strain elastography (CSE) and acoustic radiation force impulse (ARFI) elastography in differentiating likelihood of malignancy for Bethesda category III thyroid nodules. 103 thyroid nodules with Bethesda category III results on fine-needle aspiration cytology (FNAC) in 103 patients were included and all were pathologically confirmed after surgery. Conventional ultrasound, CSE and ARFI elastography including ARFI imaging and point shear wave speed (SWS) measurement were performed. Univariate and multivariate analyses were performed to identify the independent factors associated with malignancy. Area under the receiver operating characteristic curve (Az) was calculated to assess the diagnostic performance. Pathologically, 65 nodules were benign and 38 were malignant. Significant differences were found between benign and malignant nodules in ARFI. The cut-off points were ARFI imaging grade ≥ 4, SWS > 2.94 m/s and SWS ratio > 1.09, respectively. ARFI imaging (Az: 0.861) had the highest diagnostic performance to differentiate malignant from benign nodules, following by conventional ultrasound (Az: 0.606 - 0.744), CSE (Az: 0.660) and point SWS measurement (Az: 0.725 - 0.735). Multivariate logistic regression analysis showed that ARFI imaging grade ≥ 4 was the most significant independent predictor. The combination of ARFI imaging with point SWS measurement significantly improved the specificity (100% vs. 80.0%) and positive predictive value (100 % vs. 72.9%) in comparison with ARFI imaging alone. ARFI elastography is a useful tool in differentiating malignant from benign thyroid nodules with Bethesda category III results on FNAC. PMID:27906671
Black, J A; Sharp, S J; Wareham, N J; Sandbæk, A; Rutten, G E H M; Lauritzen, T; Khunti, K; Davies, M J; Borch-Johnsen, K; Griffin, S J; Simmons, R K
2014-01-01
Aims Little is known about the long-term effects of intensive multifactorial treatment early in the diabetes disease trajectory. In the absence of long-term data on hard outcomes, we described change in 10-year modelled cardiovascular risk in the 5 years following diagnosis, and quantified the impact of intensive treatment on 10-year modelled cardiovascular risk at 5 years. Methods In a pragmatic, cluster-randomized, parallel-group trial in Denmark, the Netherlands and the UK, 3057 people with screen-detected Type 2 diabetes were randomized by general practice to receive (1) routine care of diabetes according to national guidelines (1379 patients) or (2) intensive multifactorial target-driven management (1678 patients). Ten-year modelled cardiovascular disease risk was calculated at baseline and 5 years using the UK Prospective Diabetes Study Risk Engine (version 3β). Results Among 2101 individuals with complete data at follow up (73.4%), 10-year modelled cardiovascular disease risk was 27.3% (sd 13.9) at baseline and 21.3% (sd 13.8) at 5-year follow-up (intensive treatment group difference –6.9, sd 9.0; routine care group difference –5.0, sd 12.2). Modelled 10-year cardiovascular disease risk was lower in the intensive treatment group compared with the routine care group at 5 years, after adjustment for baseline cardiovascular disease risk and clustering (–2.0; 95% CI –3.1 to –0.9). Conclusions Despite increasing age and diabetes duration, there was a decline in modelled cardiovascular disease risk in the 5 years following diagnosis. Compared with routine care, 10-year modelled cardiovascular disease risk was lower in the intensive treatment group at 5 years. Our results suggest that patients benefit from intensive treatment early in the diabetes disease trajectory, where the rate of cardiovascular disease risk progression may be slowed. PMID:24533664
Zhao, Chong-Ke; Xu, Hui-Xiong; Xu, Jun-Mei; Sun, Cheng-Yu; Chen, Wei; Liu, Bo-Ji; Bo, Xiao-Wan; Wang, Dan; Qu, Shen
2017-01-03
To assess the value of conventional ultrasound, conventional strain elastography (CSE) and acoustic radiation force impulse (ARFI) elastography in differentiating likelihood of malignancy for Bethesda category III thyroid nodules. 103 thyroid nodules with Bethesda category III results on fine-needle aspiration cytology (FNAC) in 103 patients were included and all were pathologically confirmed after surgery. Conventional ultrasound, CSE and ARFI elastography including ARFI imaging and point shear wave speed (SWS) measurement were performed. Univariate and multivariate analyses were performed to identify the independent factors associated with malignancy. Area under the receiver operating characteristic curve (Az) was calculated to assess the diagnostic performance. Pathologically, 65 nodules were benign and 38 were malignant. Significant differences were found between benign and malignant nodules in ARFI. The cut-off points were ARFI imaging grade ≥ 4, SWS > 2.94 m/s and SWS ratio > 1.09, respectively. ARFI imaging (Az: 0.861) had the highest diagnostic performance to differentiate malignant from benign nodules, following by conventional ultrasound (Az: 0.606 - 0.744), CSE (Az: 0.660) and point SWS measurement (Az: 0.725 - 0.735). Multivariate logistic regression analysis showed that ARFI imaging grade ≥ 4 was the most significant independent predictor. The combination of ARFI imaging with point SWS measurement significantly improved the specificity (100% vs. 80.0%) and positive predictive value (100 % vs. 72.9%) in comparison with ARFI imaging alone. ARFI elastography is a useful tool in differentiating malignant from benign thyroid nodules with Bethesda category III results on FNAC.
Lee, Gun-Ill; Chun, Hyoung-Joon; Choi, Kyu-Sun
2016-01-01
Objective We conducted this study to report the efficacy of local application of vancomycin powder in the setting of surgical site infection (SSI) of posterior lumbar surgical procedures and to figure out risk factors of SSIs. Methods From February 2013 to December 2013, SSI rates following 275 posterior lumbar surgeries of which intrawound vancomycin powder was used in combination with intravenous antibiotics (Vanco group) were assessed. Compared with 296 posterior lumbar procedures with intravenous antibiotic only group from February 2012 to December 2012 (non-Vanco group), various infection rates were assessed. Univariate and multivariate analysis to figure out risk factors of infection among Vanco group were done. Results Statistically significant reduction of SSI in Vanco group (5.5%) from non-Vanco group (10.5%) was confirmed (p=0.028). Mean follow-up period was 8 months. Rate of acute staphylococcal SSIs reduced statistically significantly to 4% compared to 7.4% of non-Vanco group (p=0.041). Deep staphylococcal infection decreased to 2 compared to 8 and deep methicillin-resistant Staphylococcus aureus infection also decreased to 1 compared to 5 in non-Vanco group. No systemic complication was observed. Statistically significant risk factors associated with SSI were diabetes mellitus, history of cardiovascular disease, length of hospital stay, number of instrumented level and history of previous surgery. Conclusion In this series of 571 patients, intrawound vancomycin powder usage resulted in significant decrease in SSI rates in our posterior lumbar surgical procedures. Patients at high risk of infection are highly recommended as a candidate for this technique. PMID:27437012
Beesley, Jonathan; Jordan, Susan J.; Spurdle, Amanda B.; Song, Honglin; Ramus, Susan J.; Kjaer, Suzanne Kruger; Hogdall, Estrid; DiCioccio, Richard A.; McGuire, Valerie; Whittemore, Alice S.; Gayther, Simon A.; Pharoah, Paul D.P.; Webb, Penelope M.; Chenevix-Trench, Georgia
2009-01-01
Although some high-risk ovarian cancer genes have been identified, it is likely that common low penetrance alleles exist that confer some increase in ovarian cancer risk. We have genotyped nine putative functional single-nucleotide polymorphisms (SNP) in genes involved in steroid hormone synthesis (SRD5A2, CYP19A1, HSB17B1, and HSD17B4) and DNA repair (XRCC2, XRCC3, BRCA2, and RAD52) using two Australian ovarian cancer case-control studies, comprising a total of 1,466 cases and 1,821 controls of Caucasian origin. Genotype frequencies in cases and controls were compared using logistic regression. The only SNP we found to be associated with ovarian cancer risk in both of these two studies was SRD5A2 V89L (rs523349), which showed a significant trend of increasing risk per rare allele (P = 0.00002). We then genotyped another SNP in this gene (rs632148; r2 = 0.945 with V89L) in an attempt to validate this finding in an independent set of 1,479 cases and 2,452 controls from United Kingdom, United States, and Denmark. There was no association between rs632148 and ovarian cancer risk in the validation samples, and overall, there was no significant heterogeneity between the results of the five studies. Further analyses of SNPs in this gene are therefore warranted to determine whether SRD5A2 plays a role in ovarian cancer predisposition. PMID:18086758
Harrup, Mason K; Rollins, Harry W
2013-11-26
An additive comprising a phosphazene compound that has at least two reactive functional groups and at least one capping functional group bonded to phosphorus atoms of the phosphazene compound. One of the at least two reactive functional groups is configured to react with cellulose and the other of the at least two reactive functional groups is configured to react with a resin, such as an amine resin of a polycarboxylic acid resin. The at least one capping functional group is selected from the group consisting of a short chain ether group, an alkoxy group, or an aryloxy group. Also disclosed are an additive-resin admixture, a method of treating a wood product, and a wood product.
von Holst, Hans; Li, Xiaogai
2013-07-01
Although the consequences of traumatic brain injury (TBI) and its treatment have been improved, there is still a substantial lack of understanding the mechanisms. Numerical simulation of the impact can throw further lights on site and mechanism of action. A finite element model of the human head and brain tissue was used to simulate TBI. The consequences of gradually increased kinetic energy transfer was analyzed by evaluating the impact intracranial pressure (ICP), strain level, and their potential influences on binding forces in folded protein structures. The gradually increased kinetic energy was found to have the potential to break apart bonds of Van der Waals in all impacts and hydrogen bonds at simulated impacts from 6 m/s and higher, thereby superseding the energy in folded protein structures. Further, impacts below 6 m/s showed none or very slight increase in impact ICP and strain levels, whereas impacts of 6 m/s or higher showed a gradual increase of the impact ICP and strain levels reaching over 1000 KPa and over 30%, respectively. The present simulation study shows that the free kinetic energy transfer, impact ICP, and strain levels all have the potential to initiate cytotoxic brain tissue edema by unfolding protein structures. The definition of mild, moderate, and severe TBI should thus be looked upon as the same condition and separated only by a gradual severity of impact.
NASA Astrophysics Data System (ADS)
Starchenko, Alexander V.; Bart, Andrey A.; Kizhner, Lyubov I.; Barashkova, Nadezhda K.; Volkova, Marina A.; Zhuravlev, Georgi G.; Kuzhevskaya, Irina V.; Terenteva, Maria V.
2015-11-01
The results of calculation of meteorological parameters using a meteorological model, TSU-NM3, as well as prediction of some indices of atmospheric air pollution in the city of Tomsk obtained from a mesoscale photochemical model are presented. The calculation results are compared with observational data on the atmosphere and pollutants.
ERIC Educational Resources Information Center
Sozio, Gerry
2009-01-01
Senior secondary students cover numerical integration techniques in their mathematics courses. In particular, students would be familiar with the "midpoint rule," the elementary "trapezoidal rule" and "Simpson's rule." This article derives these techniques by methods which secondary students may not be familiar with and an approach that…
Chiriac, S; Dissaux, C; Bruant-Rodier, C; Djerada, Z; Bodin, F; François, C
2016-11-17
The position of the skin paddle on the breast area is a fundamental element for the breast reconstructions by latissimus dorsi flap and prosthesis implantation. Should, as Millard advocated, to recreate the initial defect and include it in the mastectomy scar or is it better in an additional incision as have others authors. This study compares the long-term morphological results of these two attitudes, with or without additional incision.
NASA Technical Reports Server (NTRS)
Li, Yi-Wei; Elishakoff, Isaac; Starnes, James H., Jr.; Bushnell, David
1998-01-01
This study is an extension of a previous investigation of the combined effect of axisymmetric thickness variation and axisymmetric initial geometric imperfection on buckling of isotropic shells under uniform axial compression. Here the anisotropic cylindrical shells are investigated by means of Koiter's energy criterion. An asymptotic formula is derived which can be used to determine the critical buckling load for composite shells with combined initial geometric imperfection and thickness variation. Results are compared with those obtained by the software packages BOSOR4 and PANDA2.
NASA Astrophysics Data System (ADS)
Beniaiche, Ahmed; Ghenaiet, Adel; Facchini, Bruno
2017-02-01
The aero-thermal behavior of the flow field inside 30:1 scaled model reproducing an innovative smooth trailing edge of shaped wedge discharge duct with one row of enlarged pedestals have been investigated in order to determine the effect of rotation, inlet velocity and blowing conditions effects, for Re = 20,000 and 40,000 and Ro = 0-0.23. Two configurations are presented: with and without open tip configurations. Thermo-chromic liquid crystals technique is used to ensure a local measurement of the heat transfer coefficient on the blade suction side under stationary and rotation conditions. Results are reported in terms of detailed 2D HTC maps on the suction side surface as well as the averaged Nusselt number inside the pedestal ducts. Two correlations are proposed, for both closed and open tip configurations, based on the Re, Pr, Ro and a new non-dimensional parameter based on the position along the radial distance, to assess a reliable estimation of the averaged Nusselt number at the inter-pedestal region. A good agreement is found between prediction and experimental data with about ±10 to ±12 % of uncertainty, for the simple form correlation, and about ±16 % using a complex form. 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.
NASA Astrophysics Data System (ADS)
Macario Galang, Jan Albert; Narod Eco, Rodrigo; Mahar Francisco Lagmay, Alfredo
2015-04-01
The M 7.2 October 15, 2013 Bohol earthquake is the most destructive earthquake to hit the Philippines since 2012. The epicenter was located in Sagbayan municipality, central Bohol and was generated by a previously unmapped reverse fault called the "Inabanga Fault". Its name, taken after the barangay (village) where the fault is best exposed and was first seen. The earthquake resulted in 209 fatalities and over 57 billion USD worth of damages. The earthquake generated co-seismic landslides most of which were related to fault structures. Unlike rainfall induced landslides, the trigger for co-seismic landslides happen without warning. Preparedness against this type of landslide therefore, relies heavily on the identification of fracture-related unstable slopes. To mitigate the impacts of co-seismic landslide hazards, morpho-structural orientations or discontinuity sets were mapped in the field with the aid of a 2012 IFSAR Digital Terrain Model (DTM) with 5-meter pixel resolution and < 0.5 meter vertical accuracy. Coltop 3D software was then used to identify similar structures including measurement of their dip and dip directions. The chosen discontinuity sets were then keyed into Matterocking software to identify potential rock slide zones due to planar or wedged discontinuities. After identifying the structurally-controlled unstable slopes, the rock mass propagation extent of the possible rock slides was simulated using Conefall. The results were compared to a post-earthquake landslide inventory of 456 landslides. Out the total number of landslides identified from post-earthquake high-resolution imagery, 366 or 80% intersect the structural-controlled hazard areas of Bohol. The results show the potential of this method to identify co-seismic landslide hazard areas for disaster mitigation. Along with computer methods to simulate shallow landslides, and debris flow paths, located structurally-controlled unstable zones can be used to mark unsafe areas for settlement. The
1992-12-01
fisica matematica . ABSTRACT - We consider a new method for the numerical solution both of non- linear systems of equations and of cornplementauity... Matematica , Serie V11 Volume 9 , Roma (1989), 521-543 An Inexact Continuous Method for the Solution of Large Systems of Equations and Complementarity...34 - 00185 Roma - Italy APPENDIX 2 A Quadratically Convergent Method for Unear Programming’ Stefano Herzel Dipartimento di Matematica -G. Castelnuovo
NASA Astrophysics Data System (ADS)
Matang, Rex A. S.; Owens, Kay
2014-09-01
The Government of Papua New Guinea undertook a significant step in developing curriculum reform policy that promoted the use of Indigenous knowledge systems in teaching formal school subjects in any of the country's 800-plus Indigenous languages. The implementation of the Elementary Cultural Mathematics Syllabus is in line with the above curriculum emphasis. Given the aims of the reform, the research reported here investigated the influence of children's own mother tongue (Tok Ples) and traditional counting systems on their development of early number knowledge formally taught in schools. The study involved 272 school children from 22 elementary schools in four provinces. Each child participated in a task-based assessment interview focusing on eight task groups relating to early number knowledge. The results obtained indicate that, on average, children learning their traditional counting systems in their own language spent shorter time and made fewer mistakes in solving each task compared to those taught without Tok Ples (using English and/or the lingua franca, Tok Pisin). Possible reasons accounting for these differences are also discussed.
NASA Astrophysics Data System (ADS)
Bordogna, Clelia María; Albano, Ezequiel V.
2007-02-01
The aim of this paper is twofold. On the one hand we present a brief overview on the application of statistical physics methods to the modelling of social phenomena focusing our attention on models for opinion formation. On the other hand, we discuss and present original results of a model for opinion formation based on the social impact theory developed by Latané. The presented model accounts for the interaction among the members of a social group under the competitive influence of a strong leader and the mass media, both supporting two different states of opinion. Extensive simulations of the model are presented, showing that they led to the observation of a rich scenery of complex behaviour including, among others, critical behaviour and phase transitions between a state of opinion dominated by the leader and another dominated by the mass media. The occurrence of interesting finite-size effects reveals that, in small communities, the opinion of the leader may prevail over that of the mass media. This observation is relevant for the understanding of social phenomena involving a finite number of individuals, in contrast to actual physical phase transitions that take place in the thermodynamic limit. Finally, we give a brief outlook of open questions and lines for future work.
Numerical methods used in fusion science numerical modeling
NASA Astrophysics Data System (ADS)
Yagi, M.
2015-04-01
The dynamics of burning plasma is very complicated physics, which is dominated by multi-scale and multi-physics phenomena. To understand such phenomena, numerical simulations are indispensable. Fundamentals of numerical methods used in fusion science numerical modeling are briefly discussed in this paper. In addition, the parallelization technique such as open multi processing (OpenMP) and message passing interface (MPI) parallel programing are introduced and the loop-level parallelization is shown as an example.
Polyimide processing additives
NASA Technical Reports Server (NTRS)
Pratt, J. R.; St. Clair, T. L.; Burks, H. D.; Stoakley, D. M.
1987-01-01
A method has been found for enhancing the melt flow of thermoplastic polyimides during processing. A high molecular weight 422 copoly(amic acid) or copolyimide was fused with approximately 0.05 to 5 pct by weight of a low molecular weight amic acid or imide additive, and this melt was studied by capillary rheometry. Excellent flow and improved composite properties on graphite resulted from the addition of a PMDA-aniline additive to LARC-TPI. Solution viscosity studies imply that amic acid additives temporarily lower molecular weight and, hence, enlarge the processing window. Thus, compositions containing the additive have a lower melt viscosity for a longer time than those unmodified.
NASA Astrophysics Data System (ADS)
Mikhailov, V. E.; Tupitsyn, S. P.; Sokolov, V. V.; Chebakova, G. F.; Malygin, V. I.; Yazykov, Yu. V.; Kharchenko, A. V.; Chetverikov, A. N.
2012-08-01
Results from expert tests of separated combustion of Grade T and Grade ASh anthracite culm in the TP-100A boiler No. 15 at the Lugansk thermal power station carried out with and without addition of RA-GEN-F anaklarid are presented. The possibility of extending the boiler load adjustment range and excluding the use of natural gas for supporting the flame at minimal loads is considered.
The Teaching of Numerical Extensions: The Case of Negative Numbers.
ERIC Educational Resources Information Center
Bruno, Alicia; Martinon, Antonio
1999-01-01
Presents some results of a study on teaching negative numbers. Focuses on the identification of addition and subtraction, the use of the number line, additive problem solving, and the possibility of following several sequences of numerical extensions. Indicates the importance of previous ideas on positive numbers and how these ideas influence the…
NASA Astrophysics Data System (ADS)
Swanson, Charles; Kaganovich, I. D.
2016-09-01
The technique of suppressing secondary electron emission (SEE) from a surface by texturing it is developing rapidly in recent years. We have specific and general results in support of this technique: We have performed numerical and analytic calculations for determining the effective secondary electron yield (SEY) from velvet, which is an array of long cylinders on the micro-scale, and found velvet to be suitable for suppressing SEY from a normally incident primary distribution. We have performed numerical and analytic calculations also for metallic foams, which are an isotropic lattice of fibers on the micro-scale, and found foams to be suitable for suppressing SEY from an isotropic primary distribution. More generally, we have created a geometric weighted view factor model for determining the SEY suppression of a given surface geometry, which has optimization of SEY as a natural application. The optimal surface for suppressing SEY does not have finite area and has no smallest feature size, making it fractal in nature. This model gives simple criteria for a physical, non-fractal surface to suppress SEY. We found families of optimal surfaces to suppress SEY given a finite surface area. The research is supported by Air Force Office of Scientific Research (AFSOR).
NASA Astrophysics Data System (ADS)
Bogdanov, E. V.; Minina, N. Ya.; Tomm, J. W.; Kissel, H.
2012-11-01
The effects of uniaxial compression in [110] direction on energy-band structures, heavy and light hole mixing, optical matrix elements, and gain in laser diodes with "light hole up" configuration of valence band levels in GaAsP quantum wells with different widths and phosphorus contents are numerically calculated. The development of light and heavy hole mixing caused by symmetry lowering and converging behavior of light and heavy hole levels in such quantum wells under uniaxial compression is displayed. The light or heavy hole nature of each level is established for all considered values of uniaxial stress. The results of optical gain calculations for TM and TE polarization modes show that uniaxial compression leads to a significant increase of the TE mode and a minor decrease of the TM mode. Electroluminescence experiments were performed under uniaxial compression up to 5 kbar at 77 K on a model laser diode structure (p-AlxGa1-xAs/GaAs1-yPy/n-AlxGa1-xAs) with y = 0.16 and a quantum well width of 14 nm. They reveal a maximum blue shift of 27 meV of the electroluminescence spectra that is well described by the calculated change of the optical gap and the increase of the intensity being referred to a TE mode enhancement. Numerical calculations and electroluminescence data indicate that uniaxial compression may be used for a moderate wavelength and TM/TE intensity ratio tuning.
Numerical Investigation of Boiling
NASA Astrophysics Data System (ADS)
Sagan, Michael; Tanguy, Sebastien; Colin, Catherine
2012-11-01
In this work, boiling is numerically investigated, using two phase flow direct numerical simulation based on a level set / Ghost Fluid method. Nucleate boiling implies both thermal issue and multiphase dynamics issues at different scales and at different stages of bubble growth. As a result, the different phenomena are investigated separately, considering their nature and the scale at which they occur. First, boiling of a static bubble immersed in an overheated liquid is analysed. Numerical simulations have been performed at different Jakob numbers in the case of strong density discontinuity through the interface. The results show a good agreement on bubble radius evolution between the theoretical evolution and numerical simulation. After the validation of the code for the Scriven test case, interaction of a bubble with a wall is studied. A numerical method taking into account contact angle is evaluated by comparing simulations of the spreading of a liquid droplet impacting on a plate, with experimental data. Then the heat transfer near the contact line is investigated, and simulations of nucleate boiling are performed considering different contact angles values. Finally, the relevance of including a model to take into account the evaporation of the micro layer is discussed.
Frontiers in Numerical Relativity
NASA Astrophysics Data System (ADS)
Evans, Charles R.; Finn, Lee S.; Hobill, David W.
2011-06-01
Preface; Participants; Introduction; 1. Supercomputing and numerical relativity: a look at the past, present and future David W. Hobill and Larry L. Smarr; 2. Computational relativity in two and three dimensions Stuart L. Shapiro and Saul A. Teukolsky; 3. Slowly moving maximally charged black holes Robert C. Ferrell and Douglas M. Eardley; 4. Kepler's third law in general relativity Steven Detweiler; 5. Black hole spacetimes: testing numerical relativity David H. Bernstein, David W. Hobill and Larry L. Smarr; 6. Three dimensional initial data of numerical relativity Ken-ichi Oohara and Takashi Nakamura; 7. Initial data for collisions of black holes and other gravitational miscellany James W. York, Jr.; 8. Analytic-numerical matching for gravitational waveform extraction Andrew M. Abrahams; 9. Supernovae, gravitational radiation and the quadrupole formula L. S. Finn; 10. Gravitational radiation from perturbations of stellar core collapse models Edward Seidel and Thomas Moore; 11. General relativistic implicit radiation hydrodynamics in polar sliced space-time Paul J. Schinder; 12. General relativistic radiation hydrodynamics in spherically symmetric spacetimes A. Mezzacappa and R. A. Matzner; 13. Constraint preserving transport for magnetohydrodynamics John F. Hawley and Charles R. Evans; 14. Enforcing the momentum constraints during axisymmetric spacelike simulations Charles R. Evans; 15. Experiences with an adaptive mesh refinement algorithm in numerical relativity Matthew W. Choptuik; 16. The multigrid technique Gregory B. Cook; 17. Finite element methods in numerical relativity P. J. Mann; 18. Pseudo-spectral methods applied to gravitational collapse Silvano Bonazzola and Jean-Alain Marck; 19. Methods in 3D numerical relativity Takashi Nakamura and Ken-ichi Oohara; 20. Nonaxisymmetric rotating gravitational collapse and gravitational radiation Richard F. Stark; 21. Nonaxisymmetric neutron star collisions: initial results using smooth particle hydrodynamics
Hiraguchi, Hisako; Iwasaki, Yukiko; Iwasaki, Eriko; Kikuchi, Hisaji; Hirose, Hideharu; Yoneyama, Takayuki
2015-01-01
If impression materials could be immersed in disinfectant solutions for a longer period, then this form of disinfection would be easier to incorporate into dental preparation procedures. This study investigated the dimensional changes in stone models resulting from immersion of medium-viscosity hydrophilic addition-type silicone rubber impression material in disinfectant solutions for 30 min and 24 h. Impressions of a master die designed to simulate a full crown preparation with adjacent teeth were immersed in 2% glutaraldehyde and 0.55% ortho-phthalaldehyde solutions. The dimensional changes in the mesiodistal and buccolingual dimensions in the stone models were then measured using a three-dimensional coordinate system. It was found that the dimensional changes in the stone models caused by immersion of the impression materials were less than 15 μm. Immersion in 2% glutaraldehyde or 0.55% ortho-phthalaldehyde for 24 h was as clinically acceptable for medium-viscosity hydrophilic addition-type silicone rubber impressions as immersion for 30 min.
Klein, Kim; Kaspers, Gertjan; Harrison, Christine J.; Beverloo, H. Berna; Reedijk, Ardine; Bongers, Mathilda; Cloos, Jacqueline; Pession, Andrea; Reinhardt, Dirk; Zimmerman, Martin; Creutzig, Ursula; Dworzak, Michael; Alonzo, Todd; Johnston, Donna; Hirsch, Betsy; Zapotocky, Michal; De Moerloose, Barbara; Fynn, Alcira; Lee, Vincent; Taga, Takashi; Tawa, Akio; Auvrignon, Anne; Zeller, Bernward; Forestier, Erik; Salgado, Carmen; Balwierz, Walentyna; Popa, Alexander; Rubnitz, Jeffrey; Raimondi, Susana; Gibson, Brenda
2015-01-01
Purpose This retrospective cohort study aimed to determine the predictive relevance of clinical characteristics, additional cytogenetic aberrations, and cKIT and RAS mutations, as well as to evaluate whether specific treatment elements were associated with outcomes in pediatric t(8;21)-positive patients with acute myeloid leukemia (AML). Patients and Methods Karyotypes of 916 pediatric patients with t(8;21)-AML were reviewed for the presence of additional cytogenetic aberrations, and 228 samples were screened for presence of cKIT and RAS mutations. Multivariable regression models were used to assess the relevance of anthracyclines, cytarabine, and etoposide during induction and overall treatment. End points were the probability of achieving complete remission, cumulative incidence of relapse (CIR), probability of event-free survival, and probability of overall survival. Results Of 838 patients included in final analyses, 92% achieved complete remission. The 5-year overall survival, event-free survival, and CIR were 74%, 58%, and 26%, respectively. cKIT mutations and RAS mutations were not significantly associated with outcome. Patients with deletions of chromosome arm 9q [del(9q); n = 104] had a lower probability of complete remission (P = .01). Gain of chromosome 4 (+4; n = 21) was associated with inferior CIR and survival (P < .01). Anthracycline doses greater than 150 mg/m2 and etoposide doses greater than 500 mg/m2 in the first induction course and high-dose cytarabine 3 g/m2 during induction were associated with better outcomes on various end points. Cumulative doses of cytarabine greater than 30 g/m2 and etoposide greater than 1,500 mg/m2 were associated with lower CIR rates and better probability of event-free survival. Conclusion Pediatric patients with t(8;21)-AML and additional del(9q) or additional +4 might not be considered at good risk. Patients with t(8;21)-AML likely benefit from protocols that have high doses of anthracyclines, etoposide, and
Lundby, W.
1993-06-29
A method is described of controlling, reducing or eliminating, ozone and related smog resulting from photochemical reactions between ozone and automotive or industrial gases comprising the addition of iodine or compounds of iodine to hydrocarbon-base fuels prior to or during combustion in an amount of about 1 part iodine per 240 to 10,000,000 parts fuel, by weight, to be accomplished by: (a) the addition of these inhibitors during or after the refining or manufacturing process of liquid fuels; (b) the production of these inhibitors for addition into fuel tanks, such as automotive or industrial tanks; or (c) the addition of these inhibitors into combustion chambers of equipment utilizing solid fuels for the purpose of reducing ozone.
Numerical discretization for nonlinear diffusion filter
NASA Astrophysics Data System (ADS)
Mustaffa, I.; Mizuar, I.; Aminuddin, M. M. M.; Dasril, Y.
2015-05-01
Nonlinear diffusion filters are famously used in machine vision for image denoising and restoration. This paper presents a study on the effects of different numerical discretization of nonlinear diffusion filter. Several numerical discretization schemes are presented; namely semi-implicit, AOS, and fully implicit schemes. The results of these schemes are compared by visual results, objective measurement e.g. PSNR and MSE. The results are also compared to a Daubechies wavelet denoising method. It is acknowledged that the two preceding scheme have already been discussed in literature, however comparison to the latter scheme has not been made. The semi-implicit scheme uses an additive operator splitting (AOS) developed to overcome the shortcoming of the explicit scheme i.e., stability for very small time steps. Although AOS has proven to be efficient, from the nonlinear diffusion filter results with different discretization schemes, examples shows that implicit schemes are worth pursuing.
Numerical and physical magnitudes are mapped into time.
Ben-Meir, Shachar; Ganor-Stern, Dana; Tzelgov, Joseph
2012-01-01
In two experiments we investigated mapping of numerical and physical magnitudes with temporal order. Pairs of digits were presented sequentially for a size comparison task. An advantage for numbers presented in ascending order was found when participants were comparing the numbers' physical and numerical magnitudes. The effect was more robust for comparisons of physical size, as it was found using both select larger and select smaller instructions, while for numerical comparisons it was found only for select larger instructions. Varying both the digits' numerical and physical sizes resulted in a size congruity effect, indicating automatic processing of the irrelevant magnitude dimension. Temporal order and the congruency between numerical and physical magnitudes affected comparisons in an additive manner, thus suggesting that they affect different stages of the comparison process.
Numerical Propulsion System Simulation Architecture
NASA Technical Reports Server (NTRS)
Naiman, Cynthia G.
2004-01-01
The Numerical Propulsion System Simulation (NPSS) is a framework for performing analysis of complex systems. Because the NPSS was developed using the object-oriented paradigm, the resulting architecture is an extensible and flexible framework that is currently being used by a diverse set of participants in government, academia, and the aerospace industry. NPSS is being used by over 15 different institutions to support rockets, hypersonics, power and propulsion, fuel cells, ground based power, and aerospace. Full system-level simulations as well as subsystems may be modeled using NPSS. The NPSS architecture enables the coupling of analyses at various levels of detail, which is called numerical zooming. The middleware used to enable zooming and distributed simulations is the Common Object Request Broker Architecture (CORBA). The NPSS Developer's Kit offers tools for the developer to generate CORBA-based components and wrap codes. The Developer's Kit enables distributed multi-fidelity and multi-discipline simulations, preserves proprietary and legacy codes, and facilitates addition of customized codes. The platforms supported are PC, Linux, HP, Sun, and SGI.
Abrahamson, S.; Bender, M.A.; Boecker, B.B.; Scott, B.R.; Gilbert, E.S.
1993-05-01
The Nuclear Regulatory Commission (NRC) has sponsored several studies to identify and quantify, through the use of models, the potential health effects of accidental releases of radionuclides from nuclear power plants. The Reactor Safety Study provided the basis for most of the earlier estimates related to these health effects. Subsequent efforts by NRC-supported groups resulted in improved health effects models that were published in the report entitled {open_quotes}Health Effects Models for Nuclear Power Plant Consequence Analysis{close_quotes}, NUREG/CR-4214, 1985 and revised further in the 1989 report NUREG/CR-4214, Rev. 1, Part 2. The health effects models presented in the 1989 NUREG/CR-4214 report were developed for exposure to low-linear energy transfer (LET) (beta and gamma) radiation based on the best scientific information available at that time. Since the 1989 report was published, two addenda to that report have been prepared to (1) incorporate other scientific information related to low-LET health effects models and (2) extend the models to consider the possible health consequences of the addition of alpha-emitting radionuclides to the exposure source term. The first addendum report, entitled {open_quotes}Health Effects Models for Nuclear Power Plant Accident Consequence Analysis, Modifications of Models Resulting from Recent Reports on Health Effects of Ionizing Radiation, Low LET Radiation, Part 2: Scientific Bases for Health Effects Models,{close_quotes} was published in 1991 as NUREG/CR-4214, Rev. 1, Part 2, Addendum 1. This second addendum addresses the possibility that some fraction of the accident source term from an operating nuclear power plant comprises alpha-emitting radionuclides. Consideration of chronic high-LET exposure from alpha radiation as well as acute and chronic exposure to low-LET beta and gamma radiations is a reasonable extension of the health effects model.
Numerical Relativistic Quantum Optics
2013-11-08
Introduction 1 II. Relativistic Wave Equations 2 III. Stationary States 4 A. Analytical Solutions for Coulomb Potentials 4 B. Numerical Solutions...C. Relativistic Ionization Example 15 V. Computational Performance 18 VI. Conclusions 21 VII. Acknowledgements 22 References 23 1 I. INTRODUCTION ...peculiar result that B0 = 1 TG is a weak field. At present, such fields are observed only in connection with astrophysical phenomena [14]. The highest
Numerical simulation of Bootstrap Current
Wu, Yanlin; White, R.B.
1993-05-01
The neoclassical theory of Bootstrap Current in toroidal systems is calculated in magnetic flux coordinates and confirmed by numerical simulation. The effects of magnetic ripple, loop voltage, and magnetic and electrostatic perturbations on bootstrap current for the cases of zero and finite plasma pressure are studied. The numerical results are in reasonable agreement with analytical estimates.
Numerical simulation of dusty plasmas
Winske, D.
1995-09-01
The numerical simulation of physical processes in dusty plasmas is reviewed, with emphasis on recent results and unresolved issues. Three areas of research are discussed: grain charging, weak dust-plasma interactions, and strong dust-plasma interactions. For each area, we review the basic concepts that are tested by simulations, present some appropriate examples, and examine numerical issues associated with extending present work.
Phenylethynyl Containing Reactive Additives
NASA Technical Reports Server (NTRS)
Connell, John W. (Inventor); Smith, Joseph G., Jr. (Inventor); Hergenrother, Paul M. (Inventor)
2002-01-01
Phenylethynyl containing reactive additives were prepared from aromatic diamine, containing phenylethvnvl groups and various ratios of phthalic anhydride and 4-phenylethynviphthalic anhydride in glacial acetic acid to form the imide in one step or in N-methyl-2-pvrrolidinone to form the amide acid intermediate. The reactive additives were mixed in various amounts (10% to 90%) with oligomers containing either terminal or pendent phenylethynyl groups (or both) to reduce the melt viscosity and thereby enhance processability. Upon thermal cure, the additives react and become chemically incorporated into the matrix and effect an increase in crosslink density relative to that of the host resin. This resultant increase in crosslink density has advantageous consequences on the cured resin properties such as higher glass transition temperature and higher modulus as compared to that of the host resin.
Phenylethynyl Containing Reactive Additives
NASA Technical Reports Server (NTRS)
Connell, John W. (Inventor); Smith, Joseph G., Jr. (Inventor); Hergenrother, Paul M. (Inventor)
2002-01-01
Phenylethynyl containing reactive additives were prepared from aromatic diamines containing phenylethynyl groups and various ratios of phthalic anhydride and 4-phenylethynylphthalic anhydride in glacial acetic acid to form the imide in one step or in N-methyl-2-pyrrolidi none to form the amide acid intermediate. The reactive additives were mixed in various amounts (10% to 90%) with oligomers containing either terminal or pendent phenylethynyl groups (or both) to reduce the melt viscosity and thereby enhance processability. Upon thermal cure, the additives react and become chemically incorporated into the matrix and effect an increase in crosslink density relative to that of the host resin. This resultant increase in crosslink density has advantageous consequences on the cured resin properties such as higher glass transition temperature and higher modulus as compared to that of the host resin.
Bernardeau, M; Vernoux, J-P
2013-04-01
For many years, microbial adjuncts have been used to supplement the diets of farm animals and humans. They have evolved since the 1990s to become known as probiotics, i.e. functional food with health benefits. After the discovery of a possible link between manipulation of gut microflora in mice and obesity, a focus on the use of these beneficial microbes that act on gut microflora in animal farming was undertaken and compared with the use of probiotics for food. Beneficial microbes added to feed are classified at a regulatory level as zootechnical additives, in the category of gut flora stabilizers for healthy animals and are regulated up to strain level in Europe. Intended effects are improvement of performance characteristics, which are strain dependent and growth enhancement is not a prerequisite. In fact, increase of body weight is not commonly reported and its frequency is around 25% of the published data examined here. However, when a Body Weight Gain (BWG) was found in the literature, it was generally moderate (lower than or close to 10%) and this over a reduced period of their short industrial life. When it was higher than 10%, it could be explained as an indirect consequence of the alleviation of the weight losses linked to stressful intensive rearing conditions or health deficiency. However, regulations on feed do not consider the health effects because animals are supposed to be healthy, so there is no requirement for reporting healthy effects in the standard European dossier. The regulations governing the addition of beneficial microorganisms to food are less stringent than for feed and no dossier is required if a species has a Qualified Presumption of Safety status. The microbial strain marketed is not submitted to any regulation and its properties (including BWG) do not need to be studied. Only claims for functional or healthy properties are regulated and again growth effect is not included. However, recent studies on probiotic effects showed that BWG
Amorosa, Valerianna K.; Luetkemeyer, Anne; Kang, Minhee; Johnson, Victoria A.; Umbleja, Triin; Haas, David W.; Yesmin, Suria; Bardin, Matthew C.; Chung, Ray T.; Alston-Smith, Beverly; Tebas, Pablo; Peters, Marion G.
2014-01-01
Background We hypothesized that nitazoxanide (NTZ) added to pegylated inter-feron alfa-2a (PEG-IFN) and weight-based ribavirin (WBR) would improve hepatitis C virus (HCV) virologic responses in HCV treatment-naïve HIV-1/HCV genotype 1 coin-fected persons. Methods Prospective, single-arm study in which subjects received 4-week lead-in (NTZ 500 mg twice daily) followed by 48 weeks of NTZ, PEG-IFN, and WBR. We compared the HCV virologic responses of these subjects to historical controls from the completed ACTG study A5178 who received PEG-IFN and WBR and had similar subject characteristics. Primary endpoints were early virologic response and complete early virologic response (EVR and cEVR). Results Among 67 subjects (78% male; 48% Black; median age, 50 years), EVR was achieved in 65.7% (90% CI, 55.0%–75.3%), cEVR in 38.8% (28.8%–49.6%). and SVR in 32.8% (23.4%–43.5%). EVR was higher with NTZ (51.4% in A5178; P = .03), but the sustained virologic response (SVR) proportion was similar (27.3% in A5178; P = .24). In contrast to A5178, SVR was similar across IL28B genotypes. Overall, NTZ was safe and well-tolerated. Conclusion Whereas EVR proportion improved significantly in this pilot study, the addition of NTZ to PEG-IFN/WBR did not significantly improve SVR compared to historical controls. NTZ may be associated with an attenuation of the effect of IL28B on HCV treatment response. PMID:24334180
NASA Astrophysics Data System (ADS)
Magnoli, M. V.; Maiwald, M.
2014-03-01
Francis turbines have been running more and more frequently in part load conditions, in order to satisfy the new market requirements for more dynamic and flexible energy generation, ancillary services and grid regulation. The turbines should be able to be operated for longer durations with flows below the optimum point, going from part load to deep part load and even speed-no-load. These operating conditions are characterised by important unsteady flow phenomena taking place at the draft tube cone and in the runner channels, in the respective cases of part load and deep part load. The current expectations are that new Francis turbines present appropriate hydraulic stability and moderate pressure pulsations at overload, part load, deep part load and speed-no-load with high efficiency levels at normal operating range. This study presents series of investigations performed by Voith Hydro with the objective to improve the hydraulic stability of Francis turbines at overload, part load and deep part load, reduce pressure pulsations and enlarge the know-how about the transient fluid flow through the turbine at these challenging conditions. Model test measurements showed that distinct runner designs were able to influence the pressure pulsation level in the machine. Extensive experimental investigations focused on the runner deflector geometry, on runner features and how they could reduce the pressure oscillation level. The impact of design variants and machine configurations on the vortex rope at the draft tube cone at overload and part load and on the runner channel vortex at deep part load were experimentally observed and evaluated based on the measured pressure pulsation amplitudes. Numerical investigations were employed for improving the understanding of such dynamic fluid flow effects. As example for the design and experimental investigations, model test observations and pressure pulsation curves for Francis machines in mid specific speed range, around nqopt = 50 min
Electrophilic addition of astatine
Norseev, Yu.V.; Vasaros, L.; Nhan, D.D.; Huan, N.K.
1988-03-01
It has been shown for the first time that astatine is capable of undergoing addition reactions to unsaturated hydrocarbons. A new compound of astatine, viz., ethylene astatohydrin, has been obtained, and its retention numbers of squalane, Apiezon, and tricresyl phosphate have been found. The influence of various factors on the formation of ethylene astatohydrin has been studied. It has been concluded on the basis of the results obtained that the univalent cations of astatine in an acidic medium is protonated hypoastatous acid.
A numerical and experimental study of coaxial jets
NASA Technical Reports Server (NTRS)
Nikjooy, M.; Karki, K. C.; Mongia, H. C.; Mcdonell, V. G.; Samuelsen, G. S.
1989-01-01
An algebraic stress model and the standard k-epsilon model is applied to predict the mean and turbulence quantities for axisymmetric, nonswirling coaxial jets without confinement. To investigate the effects of numerical (false) diffusion on the predicted results, three different discretization schemes, namely, hybrid, power-law, and the flux-spline, are employed. In addition, an experimental study is conducted to provide data of good quality, especially near the inlet, for model assessment. The results show that the use of the algebraic stress model leads to better agreement between the numerical results and experimental data.
Bermingham, Douglas; Hill, Robert D; Woltz, Dan; Gardner, Michael K
2013-01-01
The goals of this study were to assess the primary effects of the use of cognitive strategy and a combined measure of numeric ability on recall of every-day numeric information (i.e. prices). Additionally, numeric ability was assessed as a moderator in the relationship between strategy use and memory for prices. One hundred participants memorized twelve prices that varied from 1 to 6 digits; they recalled these immediately and after 7 days. The use of strategies, assessed through self-report, was associated with better overall recall, but not forgetting. Numeric ability was not associated with either better overall recall or forgetting. A small moderating interaction was found, in which higher levels of numeric ability enhanced the beneficial effects of strategy use on overall recall. Exploratory analyses found two further small moderating interactions: simple strategy use enhanced overall recall at higher levels of numeric ability, compared to complex strategy use; and complex strategy use was associated with lower levels of forgetting, but only at higher levels of numeric ability, compared to the simple strategy use. These results provide support for an objective measure of numeric ability, as well as adding to the literature on memory and the benefits of cognitive strategy use.
[Intolerance to food additives: an update].
Cardinale, F; Mangini, F; Berardi, M; Sterpeta Loffredo, M; Chinellato, I; Dellino, A; Cristofori, F; Di Domenico, F; Mastrototaro, M F; Cappiello, A; Centoducati, T; Carella, F; Armenio, L
2008-12-01
Contrary to common believing, the prevalence of the intolerance to food additives in the general population is rather low. Nowadays many doubts persist with regard both to the pathogenetic mechanisms and to the clinical and diagnostic aspects in this field. Symptoms due to, or exacerbated from, food additives usually involve non-IgE-mediate mechanisms (pseudo-allergic reactions, PAR) and are usually less severe of those induced by food allergy. The most frequent clinical feature of the intolerance to food additives still remains the urticaria-angioedema syndrome, although these substances are really involved only in a minority of patients. Other possible clinical features include anaphylaxis, atopic eczema, behaviour disturbances, asthma and non-allergic rhinitis. The diagnostic approach consists in diary cards, reporting symptoms and food habits, elimination diet and double blinded placebo-controlled oral challenge with suspected additives. However, such procedure still remains poorly standardized and numerous uncertainties persist with regard to optimal conditions for performing and interpret the challenge results. The therapeutic approach consists in the exclusion of foods and products containing the additive involved, and, in patients not compliant to the diet, in treatment with symptomatic drugs.
Vinyl capped addition polyimides
NASA Technical Reports Server (NTRS)
Vannucci, Raymond D. (Inventor); Malarik, Diane C. (Inventor); Delvigs, Peter (Inventor)
1991-01-01
Polyimide resins (PMR) are generally useful where high strength and temperature capabilities are required (at temperatures up to about 700 F). Polyimide resins are particularly useful in applications such as jet engine compressor components, for example, blades, vanes, air seals, air splitters, and engine casing parts. Aromatic vinyl capped addition polyimides are obtained by reacting a diamine, an ester of tetracarboxylic acid, and an aromatic vinyl compound. Low void materials with improved oxidative stability when exposed to 700 F air may be fabricated as fiber reinforced high molecular weight capped polyimide composites. The aromatic vinyl capped polyimides are provided with a more aromatic nature and are more thermally stable than highly aliphatic, norbornenyl-type end-capped polyimides employed in PMR resins. The substitution of aromatic vinyl end-caps for norbornenyl end-caps in addition polyimides results in polymers with improved oxidative stability.
Numerical and experimental investigation of aeroviscoelastic systems
NASA Astrophysics Data System (ADS)
Martins, Polliana C. O.; Guimarães, Thiago A. M.; Pereira, Daniel de A.; Marques, Flávio D.; Rade, Domingos A.
2017-02-01
Viscoelastic materials have been widely used for the purpose of passive vibration mitigation in various types of mechanical systems, including, industrial machinery, civil structures and vehicles. In this paper, the use of those materials in aeroelastic systems is investigated, with emphasis placed on the influence of the viscoelastic behavior on the flutter speeds of two-degree-of-freedom typical section models, in which viscoelastic elements are introduced in addition to elastic elements associated to heave and pitch motions. The equations of motion of the aeroelastic system are modified to account for the dependence of the viscoelastic behavior on frequency and temperature, by using the concepts of complex modulus and shift factor. The aerodynamic forces and moments in subsonic regime are modeled according to Theodorsen's method. Numerical simulations are conducted to evaluate the influence of the addition of viscoelastic elements on the flutter speed and elucidate the separated influences of stiffness and damping additions. An experimental wind tunnel setup consisting of a rigid wing supported by flexible elements in pitch and plunge motions has been modified to enable the introduction of viscoelastic elements in parallel to those flexible elements. For various configurations of viscoelastic additions, the flutter instability is characterized from vibration measurements performed for increasing flow speeds in the vicinity of the stability boundary. The experimental results are used to validate the numerical model derived for the aeroviscoelastic system and confirm both qualitatively and quantitatively the predictions of the simulations, especially the possibility of increasing the flutter speed by the inclusion of viscoelastic materials.
James, Nicholas D; Sydes, Matthew R; Clarke, Noel W; Mason, Malcolm D; Dearnaley, David P; Spears, Melissa R; Ritchie, Alastair W S; Parker, Christopher C; Russell, J Martin; Attard, Gerhardt; de Bono, Johann; Cross, William; Jones, Rob J; Thalmann, George; Amos, Claire; Matheson, David; Millman, Robin; Alzouebi, Mymoona; Beesley, Sharon; Birtle, Alison J; Brock, Susannah; Cathomas, Richard; Chakraborti, Prabir; Chowdhury, Simon; Cook, Audrey; Elliott, Tony; Gale, Joanna; Gibbs, Stephanie; Graham, John D; Hetherington, John; Hughes, Robert; Laing, Robert; McKinna, Fiona; McLaren, Duncan B; O'Sullivan, Joe M; Parikh, Omi; Peedell, Clive; Protheroe, Andrew; Robinson, Angus J; Srihari, Narayanan; Srinivasan, Rajaguru; Staffurth, John; Sundar, Santhanam; Tolan, Shaun; Tsang, David; Wagstaff, John; Parmar, Mahesh K B
2016-01-01
Summary Background Long-term hormone therapy has been the standard of care for advanced prostate cancer since the 1940s. STAMPEDE is a randomised controlled trial using a multiarm, multistage platform design. It recruits men with high-risk, locally advanced, metastatic or recurrent prostate cancer who are starting first-line long-term hormone therapy. We report primary survival results for three research comparisons testing the addition of zoledronic acid, docetaxel, or their combination to standard of care versus standard of care alone. Methods Standard of care was hormone therapy for at least 2 years; radiotherapy was encouraged for men with N0M0 disease to November, 2011, then mandated; radiotherapy was optional for men with node-positive non-metastatic (N+M0) disease. Stratified randomisation (via minimisation) allocated men 2:1:1:1 to standard of care only (SOC-only; control), standard of care plus zoledronic acid (SOC + ZA), standard of care plus docetaxel (SOC + Doc), or standard of care with both zoledronic acid and docetaxel (SOC + ZA + Doc). Zoledronic acid (4 mg) was given for six 3-weekly cycles, then 4-weekly until 2 years, and docetaxel (75 mg/m2) for six 3-weekly cycles with prednisolone 10 mg daily. There was no blinding to treatment allocation. The primary outcome measure was overall survival. Pairwise comparisons of research versus control had 90% power at 2·5% one-sided α for hazard ratio (HR) 0·75, requiring roughly 400 control arm deaths. Statistical analyses were undertaken with standard log-rank-type methods for time-to-event data, with hazard ratios (HRs) and 95% CIs derived from adjusted Cox models. This trial is registered at ClinicalTrials.gov (NCT00268476) and ControlledTrials.com (ISRCTN78818544). Findings 2962 men were randomly assigned to four groups between Oct 5, 2005, and March 31, 2013. Median age was 65 years (IQR 60–71). 1817 (61%) men had M+ disease, 448 (15%) had N+/X M0, and 697 (24%) had N0M0. 165 (6
Pluta, Agnieszka; Robak, Tadeusz; Wrzesien-Kus, Agata; Katarzyna Budziszewska, Bozena; Sulek, Kazimierz; Wawrzyniak, Ewa; Czemerska, Magdalena; Zwolinska, Malgorzata; Golos, Aleksandra; Holowiecka-Goral, Aleksandra; Kyrcz-Krzemien, Slawomira; Piszcz, Jaroslaw; Kloczko, Janusz; Mordak-Domagala, Monika; Lange, Andrzej; Razny, Małgorzata; Madry, Krzysztof; Wiktor-Jedrzejczak, Wieslaw; Grosicki, Sebastian; Butrym, Aleksandra; Kuliczkowski, Kazimierz; Warzocha, Krzysztof; Holowiecki, Jerzy; Giebel, Sebastian; Szydlo, Richard; Wierzbowska, Agnieszka
2017-04-01
Intensive induction chemotherapy using anthracycline and cytarabine backbone is considered the most effective upfront therapy in physically fit older patients with acute myeloid leukemia (AML). However, outcomes of the standard induction in elderly AML are inferior to those observed in younger patients, and they are still unsatisfactory. As addition of cladribine to the standard induction therapy is known to improve outcome in younger AML patients. The present randomized phase II study compares efficacy and toxicity of the DAC (daunorubicin plus cytarabine plus cladribine) regimen with the standard DA (daunorubicin plus cytarabine) regimen in the newly diagnosed AML patients over 60 years of age. A total of 171 patients were enrolled in the study (DA, 86; DAC, 85). A trend toward higher complete remission (CR) was observed in the DAC arm compared to the DA arm (44% vs. 34%; P = .19), which did not lead to improved median overall survival, which in the case of the DAC group was 8.6 months compared to in 9.1 months in the DA group (P = .64). However, DAC appeared to be superior in the group of patients aged 60-65 (CR rate: DAC 51% vs. DA 29%; P = .02). What is more, a subgroup of patients, with good and intermediate karyotypes, benefited from addition of cladribine also in terms of overall survival (P = .02). No differences in hematological and nonhematological toxicity between the DA and DAC regimens were observed.
Milligan, Donald W; Wheatley, Keith; Littlewood, Timothy; Craig, Jenny I O; Burnett, Alan K
2006-06-15
The optimum chemotherapy schedule for reinduction of patients with high-risk acute myeloid leukemia (relapsed, resistant/refractory, or adverse genetic disease) is uncertain. The MRC AML (Medical Research Council Acute Myeloid Leukemia) Working Group designed a trial comparing fludarabine and high-dose cytosine (FLA) with standard chemotherapy comprising cytosine arabinoside, daunorubicin, and etoposide (ADE). Patients were also randomly assigned to receive filgrastim (G-CSF) from day 0 until neutrophil count was greater than 0.5 x 10(9)/L (or for a maximum of 28 days) and all-trans retinoic acid (ATRA) for 90 days. Between 1998 and 2003, 405 patients were entered: 250 were randomly assigned between FLA and ADE; 356 to G-CSF versus no G-CSF; 362 to ATRA versus no ATRA. The complete remission rate was 61% with 4-year disease-free survival of 29%. There were no significant differences in the CR rate, deaths in CR, relapse rate, or DFS between ADE and FLA, although survival at 4 years was worse with FLA (16% versus 27%, P = .05). Neither the addition of ATRA nor G-CSF demonstrated any differences in the CR rate, relapse rate, DFS, or overall survival between the groups. In conclusion these findings indicate that FLA may be inferior to standard chemotherapy in high-risk AML and that the outcome is not improved with the addition of either G-CSF or ATRA.
New addition curing polyimides
NASA Technical Reports Server (NTRS)
Frimer, Aryeh A.; Cavano, Paul
1991-01-01
In an attempt to improve the thermal-oxidative stability (TOS) of PMR-type polymers, the use of 1,4-phenylenebis (phenylmaleic anhydride) PPMA, was evaluated. Two series of nadic end-capped addition curing polyimides were prepared by imidizing PPMA with either 4,4'-methylene dianiline or p-phenylenediamine. The first resulted in improved solubility and increased resin flow while the latter yielded a compression molded neat resin sample with a T(sub g) of 408 C, close to 70 C higher than PME-15. The performance of these materials in long term weight loss studies was below that of PMR-15, independent of post-cure conditions. These results can be rationalized in terms of the thermal lability of the pendant phenyl groups and the incomplete imidization of the sterically congested PPMA. The preparation of model compounds as well as future research directions are discussed.
Numerical Optimization Using Computer Experiments
NASA Technical Reports Server (NTRS)
Trosset, Michael W.; Torczon, Virginia
1997-01-01
Engineering design optimization often gives rise to problems in which expensive objective functions are minimized by derivative-free methods. We propose a method for solving such problems that synthesizes ideas from the numerical optimization and computer experiment literatures. Our approach relies on kriging known function values to construct a sequence of surrogate models of the objective function that are used to guide a grid search for a minimizer. Results from numerical experiments on a standard test problem are presented.
Numerical modeling of preburner flowfield
NASA Astrophysics Data System (ADS)
Chow, A. S.; Mo, J. D.; Jin, K. R.
1993-06-01
This work is intended to numerically predict the flowfields inside the preburner of the Space Shuttle Main Engine. The computer code (FDNS) based on pressure correction method is modified and adapted with an elliptic grid generator. The original configuration of the preburner in conjunction with downstream gas turbines has been simplified geometrically and numerically modeled at its full power in this work. The computational results are presented and qualitatively discussed with test data collected in NASA/MSFC.
Grigor'ev, Iu G; Grigor'ev, O A; Ivanov, A A; Liaginskaia, A M; Merkulov, A V; Stepanov, V S; Shagina, N B
2010-01-01
Mobile communications provides a new source of electromagnetic exposure for almost the whole population of the Russian Federation. For the first time in the history of civilization the brain of mobile phone users was exposed to localized radiofrequency (RF) electromagnetic fields (EMF). Population exposure from the base stations is also considered to be specific. However, existing standards for limiting the exposure do not account for this special EMF source and may not ensure the absence of health effects. There was a need for reliable information that would extend databases used for development of new standards. As recommended by the World Health Organization an additional experiment was performed under the supervision of foreign experts, which showed changes in autoimmune status in rats after long-term low-level RF EMF exposure with an incident power density of 500 microW/cm2.
An Additional Symmetry in the Weinberg-Salam Model
Bakker, B.L.G.; Veselov, A.I.; Zubkov, M.A.
2005-06-01
An additional Z{sub 6} symmetry hidden in the fermion and Higgs sectors of the Standard Model has been found recently. It has a singular nature and is connected to the centers of the SU(3) and SU(2) subgroups of the gauge group. A lattice regularization of the Standard Model was constructed that possesses this symmetry. In this paper, we report our results on the numerical simulation of its electroweak sector.
Ochi, Yasuo; Yamada, Hiroyuki; Mori, Hiroshi; Kawada, Naoki; Tanaka, Makoto; Imagawa, Akira; Ohmoto, Kazuyuki; Kawabata, Kazuhito
2016-01-01
This study examined the effects of a novel cathepsin K inhibitor, ONO-KK1-300-01 (KK1-300), used concurrently with parathyroid hormone (PTH) in ovariectomized (OVX) rats. KK1-300 (3 mg/kg, twice daily), alendronate (1 mg/kg, once daily) or vehicle were orally administered to OVX rats for 56 days, starting the day after ovariectomy, followed by combination treatment with or without PTH (3 μg/kg, subcutaneously three times a week) for another 28 days. OVX control animals exhibited a significant increase in both bone resorption (urinary deoxypyridinoline; DPD) and formation markers (serum osteocalcin) as well as microstructural changes associated with decreased bone mineral density (BMD). Combination treatment with KK1-300 and PTH significantly decreased urinary DPD and increased serum osteocalcin, indicating a sustained beneficial effect compared to the effect of each mono-therapy. On the other hand, combination therapy with alendronate and PTH weakened the PTH-induced increase in osteocalcin. In proximal tibia, combination treatment with KK1-300 and PTH increased BMD to a level significantly higher than that achieved following single treatment with KK1-300 or PTH alone. On the other hand, combination treatment with alendronate and PTH failed to produce any significant additive effect on BMD following single treatment with alendronate or PTH alone. Microstructural analysis revealed that the PTH-induced increase in bone formation (MS/BS and BFR/BS) was fully maintained following combination treatment with KK1-300 and PTH, but not following combination treatment with alendronate and PTH. These findings indicate that KK1-300, unlike alendronate, has an additive effect on the preventive action of PTH on bone loss in OVX rats.
Fagard, Catherine; Grondin, Carine; Descamps, Diane; Yazdanpanah, Yazdan; Charpentier, Charlotte; Colin de Verdiere, Nathalie; Tabuteau, Sophie; Raffi, François; Cabie, André; Chene, Geneviève; Yeni, Patrick
2013-01-01
We studied whether addition of enfuvirtide (ENF) to a background combination antiretroviral therapy (cART) would improve the CD4 cell count response at week 24 in naive patients with advanced HIV disease. ANRS 130 Apollo is a randomized study, conducted in naive HIV-1-infected patients, either asymptomatic with CD4 counts of <100/mm3 or stage B/C disease with CD4 counts of <200/mm3. Patients received tenofovir-emtricitabine with lopinavir-ritonavir (LPV/r) or efavirenz and were randomized to receive ENF for 24 weeks (ENF arm) or not (control arm). The primary endpoint was the proportion of patients with CD4 counts of ≥200/mm3 at week 24. A total of 195 patients were randomized: 73% had stage C disease, 78% were male, the mean age was 44 years, the median CD4 count was 30/mm3, and the median HIV-1 RNA load was 5.4 log10 copies/ml. Eighty-one percent of patients received LPV/r. One patient was lost to follow-up, and eight discontinued the study (four in each arm). The proportions of patients with CD4 counts of ≥200/mm3 at week 24 were 34% and 38% in the ENF and control arms, respectively (P = 0.53). The proportions of patients with HIV-1 RNA loads of <50 copies/ml were 74% and 58% at week 24 in the ENF and control arms, respectively (P < 0.02), and the proportion reached 79% in both arms at week 48. Twenty (20%) and 12 patients (13%) in the ENF and control arms, respectively, experienced at least one AIDS event during follow-up (P = 0.17). Although inducing a more rapid virological response, addition of ENF to a standard cART does not improve the immunological outcome in naive HIV-infected patients with severe immunosuppression. PMID:23165467
Joly, Véronique; Fagard, Catherine; Grondin, Carine; Descamps, Diane; Yazdanpanah, Yazdan; Charpentier, Charlotte; Colin de Verdiere, Nathalie; Tabuteau, Sophie; Raffi, François; Cabie, André; Chene, Geneviève; Yeni, Patrick
2013-02-01
We studied whether addition of enfuvirtide (ENF) to a background combination antiretroviral therapy (cART) would improve the CD4 cell count response at week 24 in naive patients with advanced HIV disease. ANRS 130 Apollo is a randomized study, conducted in naive HIV-1-infected patients, either asymptomatic with CD4 counts of <100/mm(3) or stage B/C disease with CD4 counts of <200/mm(3). Patients received tenofovir-emtricitabine with lopinavir-ritonavir (LPV/r) or efavirenz and were randomized to receive ENF for 24 weeks (ENF arm) or not (control arm). The primary endpoint was the proportion of patients with CD4 counts of ≥ 200/mm(3) at week 24. A total of 195 patients were randomized: 73% had stage C disease, 78% were male, the mean age was 44 years, the median CD4 count was 30/mm(3), and the median HIV-1 RNA load was 5.4 log(10) copies/ml. Eighty-one percent of patients received LPV/r. One patient was lost to follow-up, and eight discontinued the study (four in each arm). The proportions of patients with CD4 counts of ≥ 200/mm(3) at week 24 were 34% and 38% in the ENF and control arms, respectively (P = 0.53). The proportions of patients with HIV-1 RNA loads of <50 copies/ml were 74% and 58% at week 24 in the ENF and control arms, respectively (P < 0.02), and the proportion reached 79% in both arms at week 48. Twenty (20%) and 12 patients (13%) in the ENF and control arms, respectively, experienced at least one AIDS event during follow-up (P = 0.17). Although inducing a more rapid virological response, addition of ENF to a standard cART does not improve the immunological outcome in naive HIV-infected patients with severe immunosuppression.
Preattentive Processing of Numerical Visual Information
Hesse, Philipp N.; Schmitt, Constanze; Klingenhoefer, Steffen; Bremmer, Frank
2017-01-01
Humans can perceive and estimate approximate numerical information, even when accurate counting is impossible e.g., due to short presentation time. If the number of objects to be estimated is small, typically around 1–4 items, observers are able to give very fast and precise judgments with high confidence—an effect that is called subitizing. Due to its speed and effortless nature subitizing has usually been assumed to be preattentive, putting it into the same category as other low level visual features like color or orientation. More recently, however, a number of studies have suggested that subitizing might be dependent on attentional resources. In our current study we investigated the potentially preattentive nature of visual numerical perception in the subitizing range by means of EEG. We presented peripheral, task irrelevant sequences of stimuli consisting of a certain number of circular patches while participants were engaged in a demanding, non-numerical detection task at the fixation point drawing attention away from the number stimuli. Within a sequence of stimuli of a given number of patches (called “standards”) we interspersed some stimuli of different numerosity (“oddballs”). We compared the evoked responses to visually identical stimuli that had been presented in two different conditions, serving as standard in one condition and as oddball in the other. We found significant visual mismatch negativity (vMMN) responses over parieto-occipital electrodes. In addition to the event-related potential (ERP) analysis, we performed a time-frequency analysis (TFA) to investigate whether the vMMN was accompanied by additional oscillatory processes. We found a concurrent increase in evoked theta power of similar strength over both hemispheres. Our results provide clear evidence for a preattentive processing of numerical visual information in the subitizing range. PMID:28261078
Preattentive Processing of Numerical Visual Information.
Hesse, Philipp N; Schmitt, Constanze; Klingenhoefer, Steffen; Bremmer, Frank
2017-01-01
Humans can perceive and estimate approximate numerical information, even when accurate counting is impossible e.g., due to short presentation time. If the number of objects to be estimated is small, typically around 1-4 items, observers are able to give very fast and precise judgments with high confidence-an effect that is called subitizing. Due to its speed and effortless nature subitizing has usually been assumed to be preattentive, putting it into the same category as other low level visual features like color or orientation. More recently, however, a number of studies have suggested that subitizing might be dependent on attentional resources. In our current study we investigated the potentially preattentive nature of visual numerical perception in the subitizing range by means of EEG. We presented peripheral, task irrelevant sequences of stimuli consisting of a certain number of circular patches while participants were engaged in a demanding, non-numerical detection task at the fixation point drawing attention away from the number stimuli. Within a sequence of stimuli of a given number of patches (called "standards") we interspersed some stimuli of different numerosity ("oddballs"). We compared the evoked responses to visually identical stimuli that had been presented in two different conditions, serving as standard in one condition and as oddball in the other. We found significant visual mismatch negativity (vMMN) responses over parieto-occipital electrodes. In addition to the event-related potential (ERP) analysis, we performed a time-frequency analysis (TFA) to investigate whether the vMMN was accompanied by additional oscillatory processes. We found a concurrent increase in evoked theta power of similar strength over both hemispheres. Our results provide clear evidence for a preattentive processing of numerical visual information in the subitizing range.
Numerical investigation of multi-element airfoils
NASA Technical Reports Server (NTRS)
Cummings, Russell M.
1993-01-01
The flow over multi-element airfoils with flat-plate lift-enhancing tabs was numerically investigated. Tabs ranging in height from 0.25 percent to 1.25 percent of the reference airfoil chord were studied near the trailing edge of the main-element. This two-dimensional numerical simulation employed an incompressible Navier-Stokes solver on a structured, embedded grid topology. New grid refinements were used to improve the accuracy of the solution near the overlapping grid boundaries. The effects of various tabs were studied at a constant Reynolds number on a two-element airfoil with a slotted flap. Both computed and measured results indicated that a tab in the main-element cove improved the maximum lift and lift-to-drag ratio relative to the baseline airfoil without a tab. Computed streamlines revealed that the additional turning caused by the tab may reduce the amount of separated flow on the flap. A three-element airfoil was also studied over a range of Reynolds numbers. For the optimized flap rigging, the computed and measured Reynolds number effects were similar. When the flap was moved from the optimum position, numerical results indicated that a tab may help to reoptimize the airfoil to within 1 percent of the optimum flap case.
Numerical Propulsion System Simulation
NASA Technical Reports Server (NTRS)
Naiman, Cynthia
2006-01-01
The NASA Glenn Research Center, in partnership with the aerospace industry, other government agencies, and academia, is leading the effort to develop an advanced multidisciplinary analysis environment for aerospace propulsion systems called the Numerical Propulsion System Simulation (NPSS). NPSS is a framework for performing analysis of complex systems. The initial development of NPSS focused on the analysis and design of airbreathing aircraft engines, but the resulting NPSS framework may be applied to any system, for example: aerospace, rockets, hypersonics, power and propulsion, fuel cells, ground based power, and even human system modeling. NPSS provides increased flexibility for the user, which reduces the total development time and cost. It is currently being extended to support the NASA Aeronautics Research Mission Directorate Fundamental Aeronautics Program and the Advanced Virtual Engine Test Cell (AVETeC). NPSS focuses on the integration of multiple disciplines such as aerodynamics, structure, and heat transfer with numerical zooming on component codes. Zooming is the coupling of analyses at various levels of detail. NPSS development includes capabilities to facilitate collaborative engineering. The NPSS will provide improved tools to develop custom components and to use capability for zooming to higher fidelity codes, coupling to multidiscipline codes, transmitting secure data, and distributing simulations across different platforms. These powerful capabilities extend NPSS from a zero-dimensional simulation tool to a multi-fidelity, multidiscipline system-level simulation tool for the full development life cycle.
ERIC Educational Resources Information Center
Sattath, Shmuel; Tversky, Amos
1977-01-01
Tree representations of similarity data are investigated. Hierarchical clustering is critically examined, and a more general procedure, called the additive tree, is presented. The additive tree representation is then compared to multidimensional scaling. (Author/JKS)
1993-05-01
been Sponsored by the Nuclear Regulatory Commission. Report NUREG /CR-2l4, Rev. 1, Part II (NRC, 1989a) describes in detail the most recent health...that address early-occurring and continuing effects, late somatic effects, and genetic effects. These results should be used with the basic NUREG
A numerical comparison of discrete Kalman filtering algorithms: An orbit determination case study
NASA Technical Reports Server (NTRS)
Thornton, C. L.; Bierman, G. J.
1976-01-01
The numerical stability and accuracy of various Kalman filter algorithms are thoroughly studied. Numerical results and conclusions are based on a realistic planetary approach orbit determination study. The case study results of this report highlight the numerical instability of the conventional and stabilized Kalman algorithms. Numerical errors associated with these algorithms can be so large as to obscure important mismodeling effects and thus give misleading estimates of filter accuracy. The positive result of this study is that the Bierman-Thornton U-D covariance factorization algorithm is computationally efficient, with CPU costs that differ negligibly from the conventional Kalman costs. In addition, accuracy of the U-D filter using single-precision arithmetic consistently matches the double-precision reference results. Numerical stability of the U-D filter is further demonstrated by its insensitivity of variations in the a priori statistics.
Numerical simulation of steady supersonic flow. [spatial marching
NASA Technical Reports Server (NTRS)
Schiff, L. B.; Steger, J. L.
1981-01-01
A noniterative, implicit, space-marching, finite-difference algorithm was developed for the steady thin-layer Navier-Stokes equations in conservation-law form. The numerical algorithm is applicable to steady supersonic viscous flow over bodies of arbitrary shape. In addition, the same code can be used to compute supersonic inviscid flow or three-dimensional boundary layers. Computed results from two-dimensional and three-dimensional versions of the numerical algorithm are in good agreement with those obtained from more costly time-marching techniques.
Printability of alloys for additive manufacturing
Mukherjee, T.; Zuback, J. S.; De, A.; DebRoy, T.
2016-01-01
Although additive manufacturing (AM), or three dimensional (3D) printing, provides significant advantages over existing manufacturing techniques, metallic parts produced by AM are susceptible to distortion, lack of fusion defects and compositional changes. Here we show that the printability, or the ability of an alloy to avoid these defects, can be examined by developing and testing appropriate theories. A theoretical scaling analysis is used to test vulnerability of various alloys to thermal distortion. A theoretical kinetic model is used to examine predisposition of different alloys to AM induced compositional changes. A well-tested numerical heat transfer and fluid flow model is used to compare susceptibilities of various alloys to lack of fusion defects. These results are tested and validated with independent experimental data. The findings presented in this paper are aimed at achieving distortion free, compositionally sound and well bonded metallic parts. PMID:26796864
Printability of alloys for additive manufacturing
NASA Astrophysics Data System (ADS)
Mukherjee, T.; Zuback, J. S.; de, A.; Debroy, T.
2016-01-01
Although additive manufacturing (AM), or three dimensional (3D) printing, provides significant advantages over existing manufacturing techniques, metallic parts produced by AM are susceptible to distortion, lack of fusion defects and compositional changes. Here we show that the printability, or the ability of an alloy to avoid these defects, can be examined by developing and testing appropriate theories. A theoretical scaling analysis is used to test vulnerability of various alloys to thermal distortion. A theoretical kinetic model is used to examine predisposition of different alloys to AM induced compositional changes. A well-tested numerical heat transfer and fluid flow model is used to compare susceptibilities of various alloys to lack of fusion defects. These results are tested and validated with independent experimental data. The findings presented in this paper are aimed at achieving distortion free, compositionally sound and well bonded metallic parts.
Printability of alloys for additive manufacturing.
Mukherjee, T; Zuback, J S; De, A; DebRoy, T
2016-01-22
Although additive manufacturing (AM), or three dimensional (3D) printing, provides significant advantages over existing manufacturing techniques, metallic parts produced by AM are susceptible to distortion, lack of fusion defects and compositional changes. Here we show that the printability, or the ability of an alloy to avoid these defects, can be examined by developing and testing appropriate theories. A theoretical scaling analysis is used to test vulnerability of various alloys to thermal distortion. A theoretical kinetic model is used to examine predisposition of different alloys to AM induced compositional changes. A well-tested numerical heat transfer and fluid flow model is used to compare susceptibilities of various alloys to lack of fusion defects. These results are tested and validated with independent experimental data. The findings presented in this paper are aimed at achieving distortion free, compositionally sound and well bonded metallic parts.
Printability of alloys for additive manufacturing
Mukherjee, T.; Zuback, J. S.; De, A.; DebRoy, T.
2016-01-22
Although additive manufacturing (AM), or three dimensional (3D) printing, provides significant advantages over existing manufacturing techniques, metallic parts produced by AM are susceptible to distortion, lack of fusion defects and compositional changes. Here we show that the printability, or the ability of an alloy to avoid these defects, can be examined by developing and testing appropriate theories. A theoretical scaling analysis is used to test vulnerability of various alloys to thermal distortion. A theoretical kinetic model is used to examine predisposition of different alloys to AM induced compositional changes. A well-tested numerical heat transfer and fluid flow model is used to compare susceptibilities of various alloys to lack of fusion defects. These results are tested and validated with independent experimental data. Here, the findings presented in this paper are aimed at achieving distortion free, compositionally sound and well bonded metallic parts.
Printability of alloys for additive manufacturing
Mukherjee, T.; Zuback, J. S.; De, A.; ...
2016-01-22
Although additive manufacturing (AM), or three dimensional (3D) printing, provides significant advantages over existing manufacturing techniques, metallic parts produced by AM are susceptible to distortion, lack of fusion defects and compositional changes. Here we show that the printability, or the ability of an alloy to avoid these defects, can be examined by developing and testing appropriate theories. A theoretical scaling analysis is used to test vulnerability of various alloys to thermal distortion. A theoretical kinetic model is used to examine predisposition of different alloys to AM induced compositional changes. A well-tested numerical heat transfer and fluid flow model is usedmore » to compare susceptibilities of various alloys to lack of fusion defects. These results are tested and validated with independent experimental data. Here, the findings presented in this paper are aimed at achieving distortion free, compositionally sound and well bonded metallic parts.« less
[Food additives and healthiness].
Heinonen, Marina
2014-01-01
Additives are used for improving food structure or preventing its spoilage, for example. Many substances used as additives are also naturally present in food. The safety of additives is evaluated according to commonly agreed principles. If high concentrations of an additive cause adverse health effects for humans, a limit of acceptable daily intake (ADI) is set for it. An additive is a risk only when ADI is exceeded. The healthiness of food is measured on the basis of nutrient density and scientifically proven effects.
Holloway, Ian D; Ansari, Daniel
2009-05-01
Although it is often assumed that abilities that reflect basic numerical understanding, such as numerical comparison, are related to children's mathematical abilities, this relationship has not been tested rigorously. In addition, the extent to which symbolic and nonsymbolic number processing play differential roles in this relationship is not yet understood. To address these questions, we collected mathematics achievement measures from 6- to 8-year-olds as well as reaction times from a numerical comparison task. Using the reaction times, we calculated the size of the numerical distance effect exhibited by each child. In a correlational analysis, we found that the individual differences in the distance effect were related to mathematics achievement but not to reading achievement. This relationship was found to be specific to symbolic numerical comparison. Implications for the role of basic numerical competency and the role of accessing numerical magnitude information from Arabic numerals for the development of mathematical skills and their impairment are discussed.
Linsen, Sarah; Torbeyns, Joke; Verschaffel, Lieven; Reynvoet, Bert; De Smedt, Bert
2016-03-01
There are two well-known computation methods for solving multi-digit subtraction items, namely mental and algorithmic computation. It has been contended that mental and algorithmic computation differentially rely on numerical magnitude processing, an assumption that has already been examined in children, but not yet in adults. Therefore, in this study, we examined how numerical magnitude processing was associated with mental and algorithmic computation, and whether this association with numerical magnitude processing was different for mental versus algorithmic computation. We also investigated whether the association between numerical magnitude processing and mental and algorithmic computation differed for measures of symbolic versus nonsymbolic numerical magnitude processing. Results showed that symbolic, and not nonsymbolic, numerical magnitude processing was associated with mental computation, but not with algorithmic computation. Additional analyses showed, however, that the size of this association with symbolic numerical magnitude processing was not significantly different for mental and algorithmic computation. We also tried to further clarify the association between numerical magnitude processing and complex calculation by also including relevant arithmetical subskills, i.e. arithmetic facts, needed for complex calculation that are also known to be dependent on numerical magnitude processing. Results showed that the associations between symbolic numerical magnitude processing and mental and algorithmic computation were fully explained by individual differences in elementary arithmetic fact knowledge.
Trees, bialgebras and intrinsic numerical algorithms
NASA Technical Reports Server (NTRS)
Crouch, Peter; Grossman, Robert; Larson, Richard
1990-01-01
Preliminary work about intrinsic numerical integrators evolving on groups is described. Fix a finite dimensional Lie group G; let g denote its Lie algebra, and let Y(sub 1),...,Y(sub N) denote a basis of g. A class of numerical algorithms is presented that approximate solutions to differential equations evolving on G of the form: dot-x(t) = F(x(t)), x(0) = p is an element of G. The algorithms depend upon constants c(sub i) and c(sub ij), for i = 1,...,k and j is less than i. The algorithms have the property that if the algorithm starts on the group, then it remains on the group. In addition, they also have the property that if G is the abelian group R(N), then the algorithm becomes the classical Runge-Kutta algorithm. The Cayley algebra generated by labeled, ordered trees is used to generate the equations that the coefficients c(sub i) and c(sub ij) must satisfy in order for the algorithm to yield an rth order numerical integrator and to analyze the resulting algorithms.
Blaabjerg, K; Thomassen, A-M; Poulsen, H D
2015-02-01
The objective was to evaluate the effect of microbial phytase (1250 FTU/kg diet with 88% dry matter (DM)) on apparent total tract digestibility (ATTD) of phosphorus (P) in pigs fed a dry or soaked diet. Twenty-four pigs (65±3 kg) from six litters were used. Pigs were housed in metabolism crates and fed one of four diets for 12 days; 5 days for adaptation and 7 days for total, but separate collection of feces and urine. The basal diet was composed of wheat, barley, maize, soybean meal and no mineral phosphate. Dietary treatments were: basal dry-fed diet (BDD), BDD with microbial phytase (BDD+phy), BDD soaked for 24 h at 20°C before feeding (BDS) and BDS with microbial phytase (BDS+phy). Supplementation of microbial phytase increased ATTD of DM and crude protein (N×6.25) by 2 and 3 percentage units (P<0.0001; P<0.001), respectively. The ATTD of P was affected by the interaction between microbial phytase and soaking (P=0.02). This was due to a greater increase in ATTD of P by soaking of the diet containing solely plant phytase compared with the diet supplemented with microbial phytase: 35%, 65%, 44% and 68% for BDD, BDD+phy, BSD and BSD+phy, respectively. As such, supplementation of microbial phytase increased ATTD of P in the dry-fed diet, but not in the soaked diet. The higher ATTD of P for BDS compared with BDD resulted from the degradation of 54% of the phytate in BDS by wheat and barley phytases during soaking. On the other hand, soaking of BDS+phy did not increase ATTD of P significantly compared with BDD+phy despite that 76% of the phytate in BDS+phy was degraded before feeding. In conclusion, soaking of BDS containing solely plant phytase provided a great potential for increasing ATTD of P. However, this potential was not present when microbial phytase (1250 FTU/kg diet) was supplemented, most likely because soaking of BDS+phy for 24 h at 20°C did not result in a complete degradation of phytate before feeding.
Chijimatsu, M.; Nguyen, T.S.; Jing, L.; De Jonge, J.; Kohlmeier, M.; Millard, A.; Rejeb, A.; Rutqvist, J.; Souley, M.; Sugita, Y.
2004-06-30
Geological disposal of the spent nuclear fuel uses often the concept of multiple barrier systems. In order to predict the performance of these barriers, mathematical models have been developed, verified and validated against analytical solutions, laboratory tests and field experiments within the international DECOVALEX III project. These models in general consider the full coupling of thermal (T), hydraulic (H) and mechanical (M) processes that would prevail in the geological media around the repository. For Bench Mark Test no. 1 (BMT1) of the DECOVALEX III project, seven multinational research teams studied the implications of coupled THM processes on the safety of a hypothetical nuclear waste repository at the near-field and are presented in three accompany papers in this issue. This paper is the first of the three companion papers, which provides the conceptualization and characterization of the BMT1 as well as some general conclusions based on the findings of the numerical studies. It also shows the process of building confidence in the mathematical models by calibration with a reference T-H-M experiment with realistic rock mass conditions and bentonite properties and measured outputs of thermal, hydraulic and mechanical variables.
Deiterding, Ralf
2011-01-01
Numerical simulation can be key to the understanding of the multidimensional nature of transient detonation waves. However, the accurate approximation of realistic detonations is demanding as a wide range of scales needs to be resolved. This paper describes a successful solution strategy that utilizes logically rectangular dynamically adaptive meshes. The hydrodynamic transport scheme and the treatment of the nonequilibrium reaction terms are sketched. A ghost fluid approach is integrated into the method to allow for embedded geometrically complex boundaries. Large-scale parallel simulations of unstable detonation structures of Chapman-Jouguet detonations in low-pressure hydrogen-oxygen-argon mixtures demonstrate the efficiency of the described techniquesmore » in practice. In particular, computations of regular cellular structures in two and three space dimensions and their development under transient conditions, that is, under diffraction and for propagation through bends are presented. Some of the observed patterns are classified by shock polar analysis, and a diagram of the transition boundaries between possible Mach reflection structures is constructed.« less
Study on the numerical schemes for hypersonic flow simulation
NASA Astrophysics Data System (ADS)
Nagdewe, S. P.; Shevare, G. R.; Kim, Heuy-Dong
2009-10-01
Hypersonic flow is full of complex physical and chemical processes, hence its investigation needs careful analysis of existing schemes and choosing a suitable scheme or designing a brand new scheme. The present study deals with two numerical schemes Harten, Lax, and van Leer with Contact (HLLC) and advection upstream splitting method (AUSM) to effectively simulate hypersonic flow fields, and accurately predict shock waves with minimal diffusion. In present computations, hypersonic flows have been modeled as a system of hyperbolic equations with one additional equation for non-equilibrium energy and relaxing source terms. Real gas effects, which appear typically in hypersonic flows, have been simulated through energy relaxation method. HLLC and AUSM methods are modified to incorporate the conservation laws for non-equilibrium energy. Numerical implementation have shown that non-equilibrium energy convect with mass, and hence has no bearing on the basic numerical scheme. The numerical simulation carried out shows good comparison with experimental data available in literature. Both numerical schemes have shown identical results at equilibrium. Present study has demonstrated that real gas effects in hypersonic flows can be modeled through energy relaxation method along with either AUSM or HLLC numerical scheme.
Revised numerical wrapper for PIES code
NASA Astrophysics Data System (ADS)
Raburn, Daniel; Reiman, Allan; Monticello, Donald
2015-11-01
A revised external numerical wrapper has been developed for the Princeton Iterative Equilibrium Solver (PIES code), which is capable of calculating 3D MHD equilibria with islands. The numerical wrapper has been demonstrated to greatly improve the rate of convergence in numerous cases corresponding to equilibria in the TFTR device where magnetic islands are present. The numerical wrapper makes use of a Jacobian-free Newton-Krylov solver along with adaptive preconditioning and a sophisticated subspace-restricted Levenberg-Marquardt backtracking algorithm. The details of the numerical wrapper and several sample results are presented.
Polylactides in additive biomanufacturing.
Poh, Patrina S P; Chhaya, Mohit P; Wunner, Felix M; De-Juan-Pardo, Elena M; Schilling, Arndt F; Schantz, Jan-Thorsten; van Griensven, Martijn; Hutmacher, Dietmar W
2016-12-15
New advanced manufacturing technologies under the alias of additive biomanufacturing allow the design and fabrication of a range of products from pre-operative models, cutting guides and medical devices to scaffolds. The process of printing in 3 dimensions of cells, extracellular matrix (ECM) and biomaterials (bioinks, powders, etc.) to generate in vitro and/or in vivo tissue analogue structures has been termed bioprinting. To further advance in additive biomanufacturing, there are many aspects that we can learn from the wider additive manufacturing (AM) industry, which have progressed tremendously since its introduction into the manufacturing sector. First, this review gives an overview of additive manufacturing and both industry and academia efforts in addressing specific challenges in the AM technologies to drive toward AM-enabled industrial revolution. After which, considerations of poly(lactides) as a biomaterial in additive biomanufacturing are discussed. Challenges in wider additive biomanufacturing field are discussed in terms of (a) biomaterials; (b) computer-aided design, engineering and manufacturing; (c) AM and additive biomanufacturing printers hardware; and (d) system integration. Finally, the outlook for additive biomanufacturing was discussed.
Additive Manufactured Product Integrity
NASA Technical Reports Server (NTRS)
Waller, Jess; Wells, Doug; James, Steve; Nichols, Charles
2017-01-01
NASA is providing key leadership in an international effort linking NASA and non-NASA resources to speed adoption of additive manufacturing (AM) to meet NASA's mission goals. Participants include industry, NASA's space partners, other government agencies, standards organizations and academia. Nondestructive Evaluation (NDE) is identified as a universal need for all aspects of additive manufacturing.
Vogel, Stephan E; Grabner, Roland H; Schneider, Michael; Siegler, Robert S; Ansari, Daniel
2013-04-01
How are numerical and non-numerical magnitudes processed in the brain? Brain imaging research, primarily using comparison paradigms (i.e. judging which of two magnitudes is larger), has provided strong evidence demonstrating that the intraparietal sulcus (IPS) is a key region for processing both numerical (e.g. Arabic numerals, arrays of dots) and non-numerical magnitudes (e.g. height, brightness). These studies have suggested that there is both activation overlap and segregation in the brain regions involved in processing different dimensions of magnitude. In the present functional Magnetic Resonance Imaging (fMRI) study, we extended this line of investigation by probing the brain mechanisms underlying the mapping of numerical (Arabic numerals) and non-numerical magnitudes (brightness levels) onto a number line. Consistent with previous studies the present results revealed that number and brightness estimation was associated with overlapping activation within right lateralized areas of the posterior IPS. In addition, the contrast between number and brightness estimation revealed that bilateral anterior regions of the IPS are specifically involved in the process of estimating the position of symbolic numbers onto a number line. Furthermore, we found a significant influence of landmark reference points (0, 50 and 100) on brain activation in the right IPS for number estimation only. No regions were found to be specifically associated with brightness estimation. The results of this study reveal that the estimation of both numerical and non-numerical magnitude are associated with the engagement of a right lateralized magnitude system, but that symbolic number estimation is associated with additional engagement of bilateral regions of the anterior IPS.
Polyimide processing additives
NASA Technical Reports Server (NTRS)
Fletcher, James C. (Inventor); Pratt, J. Richard (Inventor); St.clair, Terry L. (Inventor); Stoakley, Diane M. (Inventor); Burks, Harold D. (Inventor)
1992-01-01
A process for preparing polyimides having enhanced melt flow properties is described. The process consists of heating a mixture of a high molecular weight poly-(amic acid) or polyimide with a low molecular weight amic acid or imide additive in the range of 0.05 to 15 percent by weight of additive. The polyimide powders so obtained show improved processability, as evidenced by lower melt viscosity by capillary rheometry. Likewise, films prepared from mixtures of polymers with additives show improved processability with earlier onset of stretching by TMA.
Polyimide processing additives
NASA Technical Reports Server (NTRS)
Pratt, J. Richard (Inventor); St.clair, Terry L. (Inventor); Stoakley, Diane M. (Inventor); Burks, Harold D. (Inventor)
1993-01-01
A process for preparing polyimides having enhanced melt flow properties is described. The process consists of heating a mixture of a high molecular weight poly-(amic acid) or polyimide with a low molecular weight amic acid or imide additive in the range of 0.05 to 15 percent by weight of the additive. The polyimide powders so obtained show improved processability, as evidenced by lower melt viscosity by capillary rheometry. Likewise, films prepared from mixtures of polymers with additives show improved processability with earlier onset of stretching by TMA.
Numerical Modelling of Electrical Discharges
NASA Astrophysics Data System (ADS)
Durán-Olivencia, F. J.; Pontiga, F.; Castellanos, A.
2014-03-01
The problem of the propagation of an electrical discharge between a spherical electrode and a plane has been solved by means of finite element methods (FEM) using a fluid approximation and assuming weak ionization and local equilibrium with the electric field. The numerical simulation of this type of problems presents the usual difficulties of convection-diffusion-reaction problems, in addition to those associated with the nonlinearities of the charged species velocities, the formation of steep gradients of the electric field and particle densities, and the coexistence of very different temporal scales. The effect of using different temporal discretizations for the numerical integration of the corresponding system of partial differential equations will be here investigated. In particular, the so-called θ-methods will be used, which allows to implement implicit, semi-explicit and fully explicit schemes in a simple way.
Food Additives and Hyperkinesis
ERIC Educational Resources Information Center
Wender, Ester H.
1977-01-01
The hypothesis that food additives are causally associated with hyperkinesis and learning disabilities in children is reviewed, and available data are summarized. Available from: American Medical Association 535 North Dearborn Street Chicago, Illinois 60610. (JG)
A numerical method of regenerator
NASA Astrophysics Data System (ADS)
Zhu, Shaowei; Matsubara, Yoichi
2004-02-01
A numerical method for regenerators is introduced in this paper. It is not only suitable for the regenerators in cryocoolers and Stirling engines, but also suitable for the stacks in acoustic engines and the pulse tubes in pulse tube refrigerators. The numerical model is one dimensional periodic unsteady flow model. The numerical method is based on the control volume concept with the implicitly solve method. The iteration acceleration method, which considers the one-dimensional periodic unsteady problem as the steady two-dimensional problem, is used for decreasing the calculation time. By this method, the regenerator in an inertance tube pulse tube refrigerator was simulated. The result is useful for understanding how the inefficiency of the regenerator changes with the inertance effect.
Numerical Simulation of Black Holes
NASA Astrophysics Data System (ADS)
Teukolsky, Saul
2003-04-01
Einstein's equations of general relativity are prime candidates for numerical solution on supercomputers. There is some urgency in being able to carry out such simulations: Large-scale gravitational wave detectors are now coming on line, and the most important expected signals cannot be predicted except numerically. Problems involving black holes are perhaps the most interesting, yet also particularly challenging computationally. One difficulty is that inside a black hole there is a physical singularity that cannot be part of the computational domain. A second difficulty is the disparity in length scales between the size of the black hole and the wavelength of the gravitational radiation emitted. A third difficulty is that all existing methods of evolving black holes in three spatial dimensions are plagued by instabilities that prohibit long-term evolution. I will describe the ideas that are being introduced in numerical relativity to deal with these problems, and discuss the results of recent calculations of black hole collisions.
Quantum turbulence: Theoretical and numerical problems
NASA Astrophysics Data System (ADS)
Nemirovskii, Sergey K.
2013-03-01
The term “quantum turbulence” (QT) unifies the wide class of phenomena where the chaotic set of one dimensional quantized vortex filaments (vortex tangles) appear in quantum fluids and greatly influence various physical features. Quantum turbulence displays itself differently depending on the physical situation, and ranges from quasi-classical turbulence in flowing fluids to a near equilibrium set of loops in phase transition. The statistical configurations of the vortex tangles are certainly different in, say, the cases of counterflowing helium and a rotating bulk, but in all the physical situations very similar theoretical and numerical problems arise. Furthermore, quite similar situations appear in other fields of physics, where a chaotic set of one dimensional topological defects, such as cosmic strings, or linear defects in solids, or lines of darkness in nonlinear light fields, appear in the system. There is an interpenetration of ideas and methods between these scientific topics which are far apart in other respects. The main purpose of this review is to bring together some of the most commonly discussed results on quantum turbulence, focusing on analytic and numerical studies. We set out a series of results on the general theory of quantum turbulence which aim to describe the properties of the chaotic vortex configuration, starting from vortex dynamics. In addition we insert a series of particular questions which are important both for the whole theory and for the various applications. We complete the article with a discussion of the hot topic, which is undoubtedly mainstream in this field, and which deals with the quasi-classical properties of quantum turbulence. We discuss this problem from the point of view of the theoretical results stated in the previous sections. We also included section, which is devoted to the experimental and numerical suggestions based on the discussed theoretical models.
Yin, Junming; Chen, Xi; Xing, Eric P.
2016-01-01
We consider the problem of sparse variable selection in nonparametric additive models, with the prior knowledge of the structure among the covariates to encourage those variables within a group to be selected jointly. Previous works either study the group sparsity in the parametric setting (e.g., group lasso), or address the problem in the nonparametric setting without exploiting the structural information (e.g., sparse additive models). In this paper, we present a new method, called group sparse additive models (GroupSpAM), which can handle group sparsity in additive models. We generalize the ℓ1/ℓ2 norm to Hilbert spaces as the sparsity-inducing penalty in GroupSpAM. Moreover, we derive a novel thresholding condition for identifying the functional sparsity at the group level, and propose an efficient block coordinate descent algorithm for constructing the estimate. We demonstrate by simulation that GroupSpAM substantially outperforms the competing methods in terms of support recovery and prediction accuracy in additive models, and also conduct a comparative experiment on a real breast cancer dataset.
Additive Manufacturing Infrared Inspection
NASA Technical Reports Server (NTRS)
Gaddy, Darrell
2014-01-01
Additive manufacturing is a rapid prototyping technology that allows parts to be built in a series of thin layers from plastic, ceramics, and metallics. Metallic additive manufacturing is an emerging form of rapid prototyping that allows complex structures to be built using various metallic powders. Significant time and cost savings have also been observed using the metallic additive manufacturing compared with traditional techniques. Development of the metallic additive manufacturing technology has advanced significantly over the last decade, although many of the techniques to inspect parts made from these processes have not advanced significantly or have limitations. Several external geometry inspection techniques exist such as Coordinate Measurement Machines (CMM), Laser Scanners, Structured Light Scanning Systems, or even traditional calipers and gages. All of the aforementioned techniques are limited to external geometry and contours or must use a contact probe to inspect limited internal dimensions. This presentation will document the development of a process for real-time dimensional inspection technique and digital quality record of the additive manufacturing process using Infrared camera imaging and processing techniques.
Rocket engine numerical simulation
NASA Technical Reports Server (NTRS)
Davidian, Ken
1993-01-01
The topics are presented in view graph form and include the following: a definition of the rocket engine numerical simulator (RENS); objectives; justification; approach; potential applications; potential users; RENS work flowchart; RENS prototype; and conclusions.
Rocket engine numerical simulator
NASA Technical Reports Server (NTRS)
Davidian, Ken
1993-01-01
The topics are presented in viewgraph form and include the following: a rocket engine numerical simulator (RENS) definition; objectives; justification; approach; potential applications; potential users; RENS work flowchart; RENS prototype; and conclusion.
Petersen, Ashley; Witten, Daniela; Simon, Noah
2016-01-01
We consider the problem of predicting an outcome variable using p covariates that are measured on n independent observations, in a setting in which additive, flexible, and interpretable fits are desired. We propose the fused lasso additive model (FLAM), in which each additive function is estimated to be piecewise constant with a small number of adaptively-chosen knots. FLAM is the solution to a convex optimization problem, for which a simple algorithm with guaranteed convergence to a global optimum is provided. FLAM is shown to be consistent in high dimensions, and an unbiased estimator of its degrees of freedom is proposed. We evaluate the performance of FLAM in a simulation study and on two data sets. Supplemental materials are available online, and the R package flam is available on CRAN. PMID:28239246
Numerical Relativity and Astrophysics
NASA Astrophysics Data System (ADS)
Lehner, Luis; Pretorius, Frans
2014-08-01
Throughout the Universe many powerful events are driven by strong gravitational effects that require general relativity to fully describe them. These include compact binary mergers, black hole accretion, and stellar collapse, where velocities can approach the speed of light and extreme gravitational fields (ΦNewt/c2≃1) mediate the interactions. Many of these processes trigger emission across a broad range of the electromagnetic spectrum. Compact binaries further source strong gravitational wave emission that could directly be detected in the near future. This feat will open up a gravitational wave window into our Universe and revolutionize our understanding of it. Describing these phenomena requires general relativity, and—where dynamical effects strongly modify gravitational fields—the full Einstein equations coupled to matter sources. Numerical relativity is a field within general relativity concerned with studying such scenarios that cannot be accurately modeled via perturbative or analytical calculations. In this review, we examine results obtained within this discipline, with a focus on its impact in astrophysics.
Numerical Techniques in Acoustics
NASA Technical Reports Server (NTRS)
Baumeister, K. J. (Compiler)
1985-01-01
This is the compilation of abstracts of the Numerical Techniques in Acoustics Forum held at the ASME's Winter Annual Meeting. This forum was for informal presentation and information exchange of ongoing acoustic work in finite elements, finite difference, boundary elements and other numerical approaches. As part of this forum, it was intended to allow the participants time to raise questions on unresolved problems and to generate discussions on possible approaches and methods of solution.
Deanin, R D
1975-01-01
The polymers used in plastics are generally harmless. However, they are rarely used in pure form. In almost all commercial plastics, they are "compounded" with monomeric ingredients to improve their processing and end-use performance. In order of total volume used, these monomeric additives may be classified as follows: reinforcing fibers, fillers, and coupling agents; plasticizers; colorants; stabilizers (halogen stabilizers, antioxidants, ultraviolet absorbers, and biological preservatives); processing aids (lubricants, others, and flow controls); flame retardants, peroxides; and antistats. Some information is already available, and much more is needed, on potential toxicity and safe handling of these additives during processing and manufacture of plastics products. PMID:1175566
Deanin, R D
1975-06-01
The polymers used in plastics are generally harmless. However, they are rarely used in pure form. In almost all commercial plastics, they are "compounded" with monomeric ingredients to improve their processing and end-use performance. In order of total volume used, these monomeric additives may be classified as follows: reinforcing fibers, fillers, and coupling agents; plasticizers; colorants; stabilizers (halogen stabilizers, antioxidants, ultraviolet absorbers, and biological preservatives); processing aids (lubricants, others, and flow controls); flame retardants, peroxides; and antistats. Some information is already available, and much more is needed, on potential toxicity and safe handling of these additives during processing and manufacture of plastics products.
Direct Numerical Simulations of Transient Dispersion
NASA Astrophysics Data System (ADS)
Porter, M.; Valdes-Parada, F.; Wood, B.
2008-12-01
Transient dispersion is important in many engineering applications, including transport in porous media. A common theoretical approach involves upscaling the micro-scale mass balance equations for convection- diffusion to macro-scale equations that contain effective medium quantities. However, there are a number of assumptions implicit in the various upscaling methods. For example, results obtained from volume averaging are often dependent on a given set of length and time scale constraints. Additionally, a number of the classical models for dispersion do not fully capture the early-time dispersive behavior of the solute for a general set of initial conditions. In this work, we present direct numerical simulations of micro-scale transient mass balance equations for convection-diffusion in both capillary tubes and porous media. Special attention is paid to analysis of the influence of a new time- decaying coefficient that filters the effects of the initial conditions. The direct numerical simulations were compared to results obtained from solving the closure problem associated with volume averaging. These comparisons provide a quantitative measure of the significance of (1) the assumptions implicit in the volume averaging method and (2) the importance of the early-time dispersive behavior of the solute due to various initial conditions.
Validation of numerical models for flow simulation in labyrinth seals
NASA Astrophysics Data System (ADS)
Frączek, D.; Wróblewski, W.
2016-10-01
CFD results were compared with the results of experiments for the flow through the labyrinth seal. RANS turbulence models (k-epsilon, k-omega, SST and SST-SAS) were selected for the study. Steady and transient results were analyzed. ANSYS CFX was used for numerical computation. The analysis included flow through sealing section with the honeycomb land. Leakage flows and velocity profiles in the seal were compared. In addition to the comparison of computational models, the divergence of modeling and experimental results has been determined. Tips for modeling these problems were formulated.
Technology Transfer Automated Retrieval System (TEKTRAN)
Fully biobased lubricants are those formulated using all biobased ingredients, i.e. biobased base oils and biobased additives. Such formulations provide the maximum environmental, safety, and economic benefits expected from a biobased product. Currently, there are a number of biobased base oils that...
ERIC Educational Resources Information Center
CEFP Journal, 1973
1973-01-01
A much needed addition to the Jamestown Elementary School turned out to be more than an expansion of walls for more space. A new educational program, a limited budget, and a short time line were tackled on a team approach basis and were successfully resolved. (Author)
Numerical Methods For Chemically Reacting Flows
NASA Technical Reports Server (NTRS)
Leveque, R. J.; Yee, H. C.
1990-01-01
Issues related to numerical stability, accuracy, and resolution discussed. Technical memorandum presents issues in numerical solution of hyperbolic conservation laws containing "stiff" (relatively large and rapidly changing) source terms. Such equations often used to represent chemically reacting flows. Usually solved by finite-difference numerical methods. Source terms generally necessitate use of small time and/or space steps to obtain sufficient resolution, especially at discontinuities, where incorrect mathematical modeling results in unphysical solutions.
Numerical estimation of densities
NASA Astrophysics Data System (ADS)
Ascasibar, Y.; Binney, J.
2005-01-01
We present a novel technique, dubbed FIESTAS, to estimate the underlying density field from a discrete set of sample points in an arbitrary multidimensional space. FIESTAS assigns a volume to each point by means of a binary tree. Density is then computed by integrating over an adaptive kernel. As a first test, we construct several Monte Carlo realizations of a Hernquist profile and recover the particle density in both real and phase space. At a given point, Poisson noise causes the unsmoothed estimates to fluctuate by a factor of ~2 regardless of the number of particles. This spread can be reduced to about 1dex (~26 per cent) by our smoothing procedure. The density range over which the estimates are unbiased widens as the particle number increases. Our tests show that real-space densities obtained with an SPH kernel are significantly more biased than those yielded by FIESTAS. In phase space, about 10 times more particles are required in order to achieve a similar accuracy. As a second application we have estimated phase-space densities in a dark matter halo from a cosmological simulation. We confirm the results of Arad, Dekel & Klypin that the highest values of f are all associated with substructure rather than the main halo, and that the volume function v(f) ~f-2.5 over about four orders of magnitude in f. We show that a modified version of the toy model proposed by Arad et al. explains this result and suggests that the departures of v(f) from power-law form are not mere numerical artefacts. We conclude that our algorithm accurately measures the phase-space density up to the limit where discreteness effects render the simulation itself unreliable. Computationally, FIESTAS is orders of magnitude faster than the method based on Delaunay tessellation that Arad et al. employed, making it practicable to recover smoothed density estimates for sets of 109 points in six dimensions.
Verbal structure of numerals and digits handwriting: new evidence from kinematics.
Lochy, Aliette; Pillon, Agnesa; Zesiger, Pascal; Seron, Xavier
2002-01-01
Two experiments used a digitizing tablet to analyse the temporal, spatial, and kinematic characteristics of handwritten production of arabic numbers. They addressed a specific issue of the numerical domain: Does the lexical and syntactic structure of verbal numerals influence the production of arabic numerals (Experiments 1 and 2), even after enforced semantic processing in a comparison task (Experiment 2)? Subjects had to write multi-digit arabic numerals (e.g., 1200) presented in two different verbal structures: a multiplicative one (e.g., teen-hundred, douze cents (twelve hundred)) or an additive one (e.g., thousand-unit-hundred, mille deux cents (one thousand two hundred)). Results show differences in the inter-digit jumps that reflect the influence of the structure of verbal numerals, even after the semantic task. This finding is discussed with regard to different models of number transcoding (McCloskey, Caramazza, & Basili, 1985; Power & Dal Martello, 1990, 1997).
Hydroforming Of Patchwork Blanks — Numerical Modeling And Experimental Validation
NASA Astrophysics Data System (ADS)
Lamprecht, Klaus; Merklein, Marion; Geiger, Manfred
2005-08-01
In comparison to the commonly applied technology of tailored blanks the concept of patchwork blanks offers a number of additional advantages. Potential application areas for patchwork blanks in automotive industry are e.g. local reinforcements of automotive closures, structural reinforcements of rails and pillars as well as shock towers. But even if there is a significant application potential for patchwork blanks in automobile production, industrial realization of this innovative technique is decelerated due to a lack of knowledge regarding the forming behavior and the numerical modeling of patchwork blanks. Especially for the numerical simulation of hydroforming processes, where one part of the forming tool is replaced by a fluid under pressure, advanced modeling techniques are required to ensure an accurate prediction of the blanks' forming behavior. The objective of this contribution is to provide an appropriate model for the numerical simulation of patchwork blanks' forming processes. Therefore, different finite element modeling techniques for patchwork blanks are presented. In addition to basic shell element models a combined finite element model consisting of shell and solid elements is defined. Special emphasis is placed on the modeling of the weld seam. For this purpose the local mechanical properties of the weld metal, which have been determined by means of Martens-hardness measurements and uniaxial tensile tests, are integrated in the finite element models. The results obtained from the numerical simulations are compared to experimental data from a hydraulic bulge test. In this context the focus is laid on laser- and spot-welded patchwork blanks.
Multiscale Modeling of Powder Bed-Based Additive Manufacturing
NASA Astrophysics Data System (ADS)
Markl, Matthias; Körner, Carolin
2016-07-01
Powder bed fusion processes are additive manufacturing technologies that are expected to induce the third industrial revolution. Components are built up layer by layer in a powder bed by selectively melting confined areas, according to sliced 3D model data. This technique allows for manufacturing of highly complex geometries hardly machinable with conventional technologies. However, the underlying physical phenomena are sparsely understood and difficult to observe during processing. Therefore, an intensive and expensive trial-and-error principle is applied to produce components with the desired dimensional accuracy, material characteristics, and mechanical properties. This review presents numerical modeling approaches on multiple length scales and timescales to describe different aspects of powder bed fusion processes. In combination with tailored experiments, the numerical results enlarge the process understanding of the underlying physical mechanisms and support the development of suitable process strategies and component topologies.
Requirements definition by numerical simulation
NASA Astrophysics Data System (ADS)
Hickman, James J.; Kostas, Chris; Tsang, Kang T.
1994-10-01
We are investigating the issues involved in requirements definition for narcotics interdiction: how much of a particular signature is possible, how does this amount change for different conditions, and what is the temporal relationship in various scenarios. Our approach has been to simulate numerically the conditions that arise during vapor or particulate transport. The advantages of this approach are that (1) a broad range of scenarios can be rapidly and inexpensively analyzed by simulation, and (2) simulations can display quantities that are difficult or impossible to measure. The drawback of this approach is that simulations cannot include all of the phenomena present in a real measurement, and therefore the fidelity of the simulation results is always an issue. To address this limitation, we will ultimately combine the results of numerical simulations with measurements of physical parameters for inclusion in the simulation. In this paper, we discuss these issues and how they apply to the current problems in narcotics interdictions, especially cargo containers. We also show the results of 1D and 3D numerical simulations, and compare these results with analytical solutions. The results indicate that this approach is viable. We also present data from 3D simulations of vapor transport in a loaded cargo container and some of the issues present in this ongoing work.
Numerical simulation of excited jet mixing layers
NASA Astrophysics Data System (ADS)
Scott, J. N.; Hankey, W. L.
1987-01-01
A numerical simulation of unsteady flow in jet mixing layers, both with and without external excitation, has been performed by solving the time-dependent compressible Navier-Stokes equations. Computations were performed on a CRAY X-MP computer using MacCormick's explicit finite difference algorithm. Different excitation methods were investigated and were shown to be very effective in controlling the well organized periodic production, shedding and pairing of large scale vortex structures. It is found that pressure excitation was generally more effective than temperature excitation, and that grid refinement results in substantial improvement in the resolution of unsteady features. The location and orientation, in addition to the frequency, of the excitation source are shown to have a significant influence on the production and interaction of large scale vortex structures in the jet mixing layer.
Numerical simulation of centrifugal casting of pipes
NASA Astrophysics Data System (ADS)
Kaschnitz, E.
2012-07-01
A numerical simulation model for the horizontal centrifugal pipe casting process was developed with the commercial simulation package Flow3D. It considers - additionally to mass, energy and momentum conservation equations and free surface tracking - the fast radial and slower horizontal movement of the mold. The iron inflow is not steady state but time dependent. Of special importance is the friction between the liquid and the mold in connection with the viscosity and turbulence of the iron. Experiments with the mold at controlled revolution speeds were carried out using a high-speed camera. From these experiments friction coefficients for the description of the interaction between mold and melt were obtained. With the simulation model, the influence of typical process parameters (e.g. melts inflow, mold movement, melt temperature, cooling media) on the wall thickness of the pipes can be studied. The comparison to results of pipes from production shows a good agreement between simulation and reality.
Functional Generalized Additive Models.
McLean, Mathew W; Hooker, Giles; Staicu, Ana-Maria; Scheipl, Fabian; Ruppert, David
2014-01-01
We introduce the functional generalized additive model (FGAM), a novel regression model for association studies between a scalar response and a functional predictor. We model the link-transformed mean response as the integral with respect to t of F{X(t), t} where F(·,·) is an unknown regression function and X(t) is a functional covariate. Rather than having an additive model in a finite number of principal components as in Müller and Yao (2008), our model incorporates the functional predictor directly and thus our model can be viewed as the natural functional extension of generalized additive models. We estimate F(·,·) using tensor-product B-splines with roughness penalties. A pointwise quantile transformation of the functional predictor is also considered to ensure each tensor-product B-spline has observed data on its support. The methods are evaluated using simulated data and their predictive performance is compared with other competing scalar-on-function regression alternatives. We illustrate the usefulness of our approach through an application to brain tractography, where X(t) is a signal from diffusion tensor imaging at position, t, along a tract in the brain. In one example, the response is disease-status (case or control) and in a second example, it is the score on a cognitive test. R code for performing the simulations and fitting the FGAM can be found in supplemental materials available online.
Numerical simulation of interplanetary dynamics
NASA Astrophysics Data System (ADS)
Wu, Chin-Chun
This dissertation discusses investigations into the physics of the propagation of solar generated disturbances in the interplanetary medium. The motivation to initiate this study was two-fold: (1) understanding the fundamental physics of the nonlinear interactions of solar generated MHD shocks and non-homogeneous interplanetary medium, and (2) understanding the physics of solar generated disturbance effects on the Earth's environment, (i.e. the solar connection to the geomagnetic storm). In order to achieve these goals, the authors employed two numerical models to encompass these studies. In the first part, a one-dimensional MHD code with adaptive grids is used to study the evolution of interplanetary slow shocks (ISS), the interaction of a forward slow shock with a reverse slow shock, and the interaction of a fast shock with a slow shock. Results show that the slow shocks can be generated by a decreasing density, velocity or temperature perturbation or by a pressure pulse by following a forward fast shock and that slow shocks can propagate over 1 AU; results also show that the ISS never evolves into fast shocks. Interestingly, it is also found that an ISS could be 'eaten up' by an interplanetary fast shock (IFS) catching up from behind. This could be a reason that the slow shock has been difficult to observe near 1 AU. In addition, a forward slow shock could be dissipated by following a strong forward fast shock (Mach number greater than 1.7). In the second part, a fully three-dimensional (3D), time-dependent, MHD interplanetary global model (3D IGM) is used to study the relationship between different forms of solar activity and transient variations of the north-south component, Bx, of the interplanetary magnetic field, IMF, at 1 AU. One form of solar activity, the flare, is simulated by using a pressure pulse at different locations near the solar surface and observing the simulated IMF evolution of Btheta (= -Bx) at 1 AU. Results show that, for a given pressure
Toward Scientific Numerical Modeling
NASA Technical Reports Server (NTRS)
Kleb, Bil
2007-01-01
Ultimately, scientific numerical models need quantified output uncertainties so that modeling can evolve to better match reality. Documenting model input uncertainties and verifying that numerical models are translated into code correctly, however, are necessary first steps toward that goal. Without known input parameter uncertainties, model sensitivities are all one can determine, and without code verification, output uncertainties are simply not reliable. To address these two shortcomings, two proposals are offered: (1) an unobtrusive mechanism to document input parameter uncertainties in situ and (2) an adaptation of the Scientific Method to numerical model development and deployment. Because these two steps require changes in the computational simulation community to bear fruit, they are presented in terms of the Beckhard-Harris-Gleicher change model.
NASA Astrophysics Data System (ADS)
Molodenskii, S. M.; Molodenskii, M. S.; Molodenskaya, M. S.
2014-09-01
In the first part of the paper, we obtained the refined estimates for the periods and Q-factors of the fundamental modes and overtones of spherical and toroidal oscillations with periods longer than 3 min from the data on the free oscillations of the Earth, which were excited by the earthquakes with magnitude 9 that occurred in Sumatra, Japan, and the Sea of Okhotsk. In (Molodenskii et al., 2013), we analyzed the limits of the admissible density distributions in the mantle and liquid core of the Earth, using the data on the amplitudes and phases of the forced nutations, as well as the periods and attenuation factors of the fundamental modes of the free spheroidal and toroidal oscillations of the Earth. These studies were conducted with the fixed values of the total mass and total moment of inertia of the Earth and the fixed distributions of the body seismic waves in the mantle and in the core. The solution was obtained by orthogonalizing the kernels of the integral equations that link the residuals of the observed frequencies and attenuation factors of the free oscillations, as well as the amplitudes and phases of the forced nutations, with the sought densities and Q-factors of the mantle and liquid core. Below, we present the solution of the same problem with allowance for the results obtained in the first part of this paper, namely, the new data on the periods and attenuation factors of the fundamental modes of free oscillations of the Earth and on the periods of the first four overtones of the free spheroidal and toroidal oscillations. Despite the involvement of the new data on the overtones, which have not been considered in our calculations, the weighted root mean square deviations of the theoretical predictions from the observed periods and attenuation factors of the free oscillations, as well as the amplitudes and phases of the forced nutations, have significantly decreased. This is due to (1) the noticeable reduction of the real errors in estimating the
Numerical model of Fanuc AM100iB robot
NASA Astrophysics Data System (ADS)
Cholewa, A.; Świder, J.; Zbilski, A.
2016-08-01
The article presents a numerical model of Fanuc AM 100iB robot, prepared in the form of a block diagram in Simulink software, using the SimMechanics toolbox. The main task of the numerical model of Fanuc AM 100iB robot is to calculate the value of torques putting a load on motor shafts, and to calculate the values of kinematic parameters of the robot's arms in real time and in interactive mode. The values and format of torques putting a load on subsequent joints, and then on the motor shafts, resulted from the effect of the simultaneous action of all torques and the delay, resulting from the implementation of numerical calculations in real time. The numerical model developed is a result of design focused on recreating the effects of simultaneous action of all these factors, which are present in the actual drives and affect the consumption of electricity. A very important criterion, taken into account when designing the model, was also its computational efficiency. In addition, the model was used to visualise the work of the tested machine in three-dimensional space.
Processing biobased polymers using plasticizers: Numerical simulations versus experiments
NASA Astrophysics Data System (ADS)
Desplentere, Frederik; Cardon, Ludwig; Six, Wim; Erkoç, Mustafa
2016-03-01
In polymer processing, the use of biobased products shows lots of possibilities. Considering biobased materials, biodegradability is in most cases the most important issue. Next to this, bio based materials aimed at durable applications, are gaining interest. Within this research, the influence of plasticizers on the processing of the bio based material is investigated. This work is done for an extrusion grade of PLA, Natureworks PLA 2003D. Extrusion through a slit die equipped with pressure sensors is used to compare the experimental pressure values to numerical simulation results. Additional experimental data (temperature and pressure data along the extrusion screw and die are recorded) is generated on a dr. Collin Lab extruder producing a 25mm diameter tube. All these experimental data is used to indicate the appropriate functioning of the numerical simulation tool Virtual Extrusion Laboratory 6.7 for the simulation of both the industrial available extrusion grade PLA and the compound in which 15% of plasticizer is added. Adding the applied plasticizer, resulted in a 40% lower pressure drop over the extrusion die. The combination of different experiments allowed to fit the numerical simulation results closely to the experimental values. Based on this experience, it is shown that numerical simulations also can be used for modified bio based materials if appropriate material and process data are taken into account.
Direct numerical simulation of incompressible axisymmetric flows
NASA Technical Reports Server (NTRS)
Loulou, Patrick
1994-01-01
In the present work, we propose to conduct direct numerical simulations (DNS) of incompressible turbulent axisymmetric jets and wakes. The objectives of the study are to understand the fundamental behavior of axisymmetric jets and wakes, which are perhaps the most technologically relevant free shear flows (e.g. combuster injectors, propulsion jet). Among the data to be generated are various statistical quantities of importance in turbulence modeling, like the mean velocity, turbulent stresses, and all the terms in the Reynolds-stress balance equations. In addition, we will be interested in the evolution of large-scale structures that are common in free shear flow. The axisymmetric jet or wake is also a good problem in which to try the newly developed b-spline numerical method. Using b-splines as interpolating functions in the non-periodic direction offers many advantages. B-splines have local support, which leads to sparse matrices that can be efficiently stored and solved. Also, they offer spectral-like accuracy that are C(exp O-1) continuous, where O is the order of the spline used; this means that derivatives of the velocity such as the vorticity are smoothly and accurately represented. For purposes of validation against existing results, the present code will also be able to simulate internal flows (ones that require a no-slip boundary condition). Implementation of no-slip boundary condition is trivial in the context of the b-splines.
Introduction to Numerical Methods
Schoonover, Joseph A.
2016-06-14
These are slides for a lecture for the Parallel Computing Summer Research Internship at the National Security Education Center. This gives an introduction to numerical methods. Repetitive algorithms are used to obtain approximate solutions to mathematical problems, using sorting, searching, root finding, optimization, interpolation, extrapolation, least squares regresion, Eigenvalue problems, ordinary differential equations, and partial differential equations. Many equations are shown. Discretizations allow us to approximate solutions to mathematical models of physical systems using a repetitive algorithm and introduce errors that can lead to numerical instabilities if we are not careful.
Siloxane containing addition polyimides
NASA Technical Reports Server (NTRS)
Maudgal, S.; St. Clair, T. L.
1984-01-01
Addition polyimide oligomers have been synthesized from bis(gamma-aminopropyl) tetramethyldisiloxane and 3, 3', 4, 4'-benzophenonetetracarboxylic dianhydride using a variety of latent crosslinking groups as endcappers. The prepolymers were isolated and characterized for solubility (in amide, chlorinated and ether solvents), melt flow and cure properties. The most promising systems, maleimide and acetylene terminated prepolymers, were selected for detailed study. Graphite cloth reinforced composites were prepared and properties compared with those of graphite/Kerimid 601, a commercially available bismaleimide. Mixtures of the maleimide terminated system with Kerimid 601, in varying proportions, were also studied.
Addition and subtraction by students with Down syndrome
NASA Astrophysics Data System (ADS)
Noda Herrera, Aurelia; Bruno, Alicia; González, Carina; Moreno, Lorenzo; Sanabria, Hilda
2011-01-01
We present a research report on addition and subtraction conducted with Down syndrome students between the ages of 12 and 31. We interviewed a group of students with Down syndrome who executed algorithms and solved problems using specific materials and paper and pencil. The results show that students with Down syndrome progress through the same procedural levels as those without disabilities though they have difficulties in reaching the most abstract level (numerical facts). The use of fingers or concrete representations (balls) appears as a fundamental process among these students. As for errors, these vary widely depending on the students, and can be attributed mostly to an incomplete knowledge of the decimal number system.
Numerical thermalization in particle-in-cell simulations with Monte-Carlo collisions
NASA Astrophysics Data System (ADS)
Lai, P. Y.; Lin, T. Y.; Lin-Liu, Y. R.; Chen, S. H.
2014-12-01
Numerical thermalization in collisional one-dimensional (1D) electrostatic (ES) particle-in-cell (PIC) simulations was investigated. Two collision models, the pitch-angle scattering of electrons by the stationary ion background and large-angle collisions between the electrons and the neutral background, were included in the PIC simulation using Monte-Carlo methods. The numerical results show that the thermalization times in both models were considerably reduced by the additional Monte-Carlo collisions as demonstrated by comparisons with Turner's previous simulation results based on a head-on collision model [M. M. Turner, Phys. Plasmas 13, 033506 (2006)]. However, the breakdown of Dawson's scaling law in the collisional 1D ES PIC simulation is more complicated than that was observed by Turner, and the revised scaling law of the numerical thermalization time with numerical parameters are derived on the basis of the simulation results obtained in this study.
Numerical thermalization in particle-in-cell simulations with Monte-Carlo collisions
Lai, P. Y.; Lin, T. Y.; Lin-Liu, Y. R.; Chen, S. H.
2014-12-15
Numerical thermalization in collisional one-dimensional (1D) electrostatic (ES) particle-in-cell (PIC) simulations was investigated. Two collision models, the pitch-angle scattering of electrons by the stationary ion background and large-angle collisions between the electrons and the neutral background, were included in the PIC simulation using Monte-Carlo methods. The numerical results show that the thermalization times in both models were considerably reduced by the additional Monte-Carlo collisions as demonstrated by comparisons with Turner's previous simulation results based on a head-on collision model [M. M. Turner, Phys. Plasmas 13, 033506 (2006)]. However, the breakdown of Dawson's scaling law in the collisional 1D ES PIC simulation is more complicated than that was observed by Turner, and the revised scaling law of the numerical thermalization time with numerical parameters are derived on the basis of the simulation results obtained in this study.
Numerical simulation of Ulysses nutation
NASA Technical Reports Server (NTRS)
Marirrodriga, C. Garcia; Zeischka, J.; Boslooper, E. C.
1993-01-01
A numerical simulation has been performed on the in-orbit instability of the Ulysses Spacecraft. The thermal excitation from the solar flux, the flexible axial boom and its deployment mechanism have been modeled and analyzed. The simulation shows that the nutation build-up has been originated by the solar input on the axial boom coupled with the system nutation frequency of the spacecraft. The results agree with the observed behavior.
Nonclassicality thresholds for multiqubit states: Numerical analysis
Gruca, Jacek; Zukowski, Marek; Laskowski, Wieslaw; Kiesel, Nikolai; Wieczorek, Witlef; Weinfurter, Harald; Schmid, Christian
2010-07-15
States that strongly violate Bell's inequalities are required in many quantum-informational protocols as, for example, in cryptography, secret sharing, and the reduction of communication complexity. We investigate families of such states with a numerical method which allows us to reveal nonclassicality even without direct knowledge of Bell's inequalities for the given problem. An extensive set of numerical results is presented and discussed.
Platelet additive solution - electrolytes.
Azuma, Hiroshi; Hirayama, Junichi; Akino, Mitsuaki; Ikeda, Hisami
2011-06-01
Recent attention to solutions that replace most or all plasma in platelet concentrates, while maintaining satisfactory platelet function, is motivated by the potential of plasma reduction or depletion to mitigate various transfusion-related adverse events. This report considers the electrolytic composition of previously described platelet additive solutions, in order to draw general conclusions about what is required for platelet function and longevity. The optimal concentrations of Na(+) and Cl(-) are 69-115 mM. The presence of both K(+) and Mg(2+) in platelet suspension at nearly physiological concentrations (3-5mM and 1.5-3mM, respectively) is indispensable for good preservation capacity because both electrolytes are required to prevent platelet activation. In contrast to K(+) and Mg(2+), Ca(2+) may not be important because no free Ca(2+) is available in M-sol, which showed excellent platelet preservation capacity at less than 5% plasma concentration. The importance of bicarbonate (approximately 40 mM) can be recognized when the platelets are suspended in additive solution under less than 5% residual plasma concentration.
NASA Astrophysics Data System (ADS)
Mespoulet, Jérôme; Plassard, Fabien; Hereil, Pierre-Louis
2015-09-01
Response of pressurized composite-Al vessels to hypervelocity impact of aluminum spheres have been numerically investigated to evaluate the influence of initial pressure on the vulnerability of these vessels. Investigated tanks are carbon-fiber overwrapped prestressed Al vessels. Explored internal air pressure ranges from 1 bar to 300 bar and impact velocity are around 4400 m/s. Data obtained from experiments (Xray radiographies, particle velocity measurement and post-mortem vessels) have been compared to numerical results given from LS-DYNA ALE-Lagrange-SPH full coupling models. Simulations exhibit an under estimation in term of debris cloud evolution and shock wave propagation in pressurized air but main modes of damage/rupture on the vessels given by simulations are coherent with post-mortem recovered vessels from experiments. First results of this numerical work are promising and further simulation investigations with additional experimental data will be done to increase the reliability of the simulation model. The final aim of this crossed work is to numerically explore a wide range of impact conditions (impact angle, projectile weight, impact velocity, initial pressure) that cannot be explore experimentally. Those whole results will define a rule of thumbs for the definition of a vulnerability analytical model for a given pressurized vessel.
Numerical-Optimization Program
NASA Technical Reports Server (NTRS)
Vanderplaats, Garret N.
1991-01-01
Automated Design Synthesis (ADS) computer program is general-purpose numerical-optimization program for design engineering. Provides wide range of options for solution of constrained and unconstrained function minimization problems. Suitable for such applications as minimum-weight design. Written in FORTRAN 77.
Numerical Estimation in Preschoolers
ERIC Educational Resources Information Center
Berteletti, Ilaria; Lucangeli, Daniela; Piazza, Manuela; Dehaene, Stanislas; Zorzi, Marco
2010-01-01
Children's sense of numbers before formal education is thought to rely on an approximate number system based on logarithmically compressed analog magnitudes that increases in resolution throughout childhood. School-age children performing a numerical estimation task have been shown to increasingly rely on a formally appropriate, linear…
NASA Astrophysics Data System (ADS)
Mehrmann, Volker; Xu, Hongguo
2000-11-01
We study classical control problems like pole assignment, stabilization, linear quadratic control and H[infinity] control from a numerical analysis point of view. We present several examples that show the difficulties with classical approaches and suggest reformulations of the problems in a more general framework. We also discuss some new algorithmic approaches.
Analytical, Numerical, and Experimental Results on Turbulent Boundary Layers
1976-07-01
Cl.O+O+OCOS(3.141S9Z6~O. 10*ETA»/Z.0+0+CONSFS* CETA -0.030+0) .__..--1.E..W.£.Q• .2..ANO.l....EQ.l ) F CJ , 1) II 0 .0+ 0- 11 CONTINUE . t CALCULATION...ANo.ETA.LE.O.6o+0)VLIIIII-O,10+0*VCI).O,380+0-0ELTA IF CETA .GT. 0.60+0 .AN()~ETA·,LE’-O~1o.(ny[8-"o .20.0*’ (1r.-o ’-44D+O*O’E~L’::"T=-Ao----- IfCETA.GT.O
Study of inhomogeneities in turbid media: experimental and numerical results
NASA Astrophysics Data System (ADS)
Carbone, N. A.; di Rocco, Héctor O.; Iriarte, Daniela I.; Pomarico, Juan A.; Ranea-Sandoval, Héctor F.; Pardini, Pamela; Waks-Serra, M. Victoria
2011-08-01
Near Infrared diffuse transmission of light through tissue is a tool for noninvasive imaging for diagnostic purposes. Most of the research has been focused over breast cancer imaging; however, major efforts have been done in cerebral tomography and topography imaging, as well as small animal organs imaging systems. In this work, we investigate the transmitted light profiles when scattering and absorbing cylindrical inhomogeneities are submerged at different depths inside slabs of turbid media. We analyze the transilluminance profiles when the phantom is scanned using both, CW and time resolved detection. The study of the spatial profiles obtained with CW light, shows an apparently contradictory effect when the absorption coefficient of the inclusion is higher than that of the bulk. In this case, the intensity profiles displays a peak of higher intensity where the inclusion is located, as it would be expected for a less absorbing inclusion. The experiments were compared and analyzed with a theoretical model for cylindrical inclusions and Monte Carlo simulations implemented in a Graphic Processing Unit (GPU).
Electron transport in the solar wind -results from numerical simulations
NASA Astrophysics Data System (ADS)
Smith, Håkan; Marsch, Eckart; Helander, Per
A conventional fluid approach is in general insufficient for a correct description of electron trans-port in weakly collisional plasmas such as the solar wind. The classical Spitzer-Hürm theory is a not valid when the Knudsen number (the mean free path divided by the length scale of tem-perature variation) is greater than ˜ 10-2 . Despite this, the heat transport from Spitzer-Hürm a theory is widely used in situations with relatively long mean free paths. For realistic Knud-sen numbers in the solar wind, the electron distribution function develops suprathermal tails, and the departure from a local Maxwellian can be significant at the energies which contribute the most to the heat flux moment. To accurately model heat transport a kinetic approach is therefore more adequate. Different techniques have been used previously, e.g. particle sim-ulations [Landi, 2003], spectral methods [Pierrard, 2001], the so-called 16 moment method [Lie-Svendsen, 2001], and approximation by kappa functions [Dorelli, 2003]. In the present study we solve the Fokker-Planck equation for electrons in one spatial dimension and two velocity dimensions. The distribution function is expanded in Laguerre polynomials in energy, and a finite difference scheme is used to solve the equation in the spatial dimension and the velocity pitch angle. The ion temperature and density profiles are assumed to be known, but the electric field is calculated self-consistently to guarantee quasi-neutrality. The kinetic equation is of a two-way diffusion type, for which the distribution of particles entering the computational domain in both ends of the spatial dimension must be specified, leaving the outgoing distributions to be calculated. The long mean free path of the suprathermal electrons has the effect that the details of the boundary conditions play an important role in determining the particle and heat fluxes as well as the electric potential drop across the domain. Dorelli, J. C., and J. D. Scudder, J. D. 2003, J. Geophys. Res. 108, 1294. Landi, S., and Pantellini, F. G. E. 2003, Astron. Astrophys., 400, 769. Lie-Svendsen, Ø., Leer, E., and Hansteen, V. H. 2001, J. Geophys. Res., 106, 8217. Pierrard, V., Maksimovic, M., and Lemaire, J. 2001, J. Geophys. Res., 106, 29305.
Determining Conductivity by Boundary Measurements: Some Numerical Results
1988-05-01
continuous, then -:Let B, ~ - 71iAl. If, 71i and 7y2 are Lipschitz continuous, and for some /3, V-yJ ,3 for i =1, 2, then JIB, - B2111/2,..1/2 <C 3jj1h...case of anisotropic conductors we face a problem of nonuniqueness . One way to avoid the nonuniqueness issue is to convert the matrix conductivity to an
Additive composition, for gasoline
Vataru, M.
1989-01-10
An admixture is described that comprises Diesel fuel and an additive composition added thereto which is between about 0.05 to about 2.0 percent by weight of the fuel, the composition comprising: (a) between about 0.05 and 25% relative weight parts of an organic peroxide, and (b) between about 0.1 and 25% relative weight parts of detergent selected from the component group that consists of: (i) fatty amines; (ii) ethoxylated and propoxylated derivatives of fatty amines; (iii) fatty diamines; (iv) fatty imidazlines; (v) polymeric amines and derivatives thereof; (vi) combination of one or more of the (i) through (v) components with carboxylic acid or acids having from three to forth carbon atoms, (c) from about 99.0 to about 50% by weight of a hydrocarbon solvent.
Teardrop bladder: additional considerations
Wechsler, R.J.; Brennan, R.E.
1982-07-01
Nine cases of teardrop bladder (TDB) seen at excretory urography are presented. In some of these patients, the iliopsoas muscles were at the upper limit of normal in size, and additional evaluation of the perivesical structures with computed tomography (CT) was necessary. CT demonstrated only hypertrophied muscles with or without perivesical fat. The psoas muscles and pelvic width were measured in 8 patients and compared with the measurements of a control group of males without TDB. Patients with TDB had large iliopsoas muscles and narrow pelves compared with the control group. The psoas muscle width/pelvic width ratio was significantly greater (p < 0.0005) in patients with TDB than in the control group, with values of 1.04 + 0.05 and 0.82 + 0.09, respectively. It is concluded that TDB is not an uncommon normal variant in black males. Both iliopsoas muscle hypertrophy and a narrow pelvis are factors that predispose a patient to TDB.
Perspectives on Additive Manufacturing
NASA Astrophysics Data System (ADS)
Bourell, David L.
2016-07-01
Additive manufacturing (AM) has skyrocketed in visibility commercially and in the public sector. This article describes the development of this field from early layered manufacturing approaches of photosculpture, topography, and material deposition. Certain precursors to modern AM processes are also briefly described. The growth of the field over the last 30 years is presented. Included is the standard delineation of AM technologies into seven broad categories. The economics of AM part generation is considered, and the impacts of the economics on application sectors are described. On the basis of current trends, the future outlook will include a convergence of AM fabricators, mass-produced AM fabricators, enabling of topology optimization designs, and specialization in the AM legal arena. Long-term developments with huge impact are organ printing and volume-based printing.
NASA Technical Reports Server (NTRS)
Kalvinskas, J. J.; Mueller, W. A.; Ingham, J. D. (Inventor)
1980-01-01
The additive is for a raw sewage treatment process of the type where settling tanks are used for the purpose of permitting the suspended matter in the raw sewage to be settled as well as to permit adsorption of the dissolved contaminants in the water of the sewage. The sludge, which settles down to the bottom of the settling tank is extracted, pyrolyzed and activated to form activated carbon and ash which is mixed with the sewage prior to its introduction into the settling tank. The sludge does not provide all of the activated carbon and ash required for adequate treatment of the raw sewage. It is necessary to add carbon to the process and instead of expensive commercial carbon, coal is used to provide the carbon supplement.
Evolution of solidification texture during additive manufacturing
Wei, H. L.; Mazumder, J.; DebRoy, T.
2015-01-01
Striking differences in the solidification textures of a nickel based alloy owing to changes in laser scanning pattern during additive manufacturing are examined based on theory and experimental data. Understanding and controlling texture are important because it affects mechanical and chemical properties. Solidification texture depends on the local heat flow directions and competitive grain growth in one of the six <100> preferred growth directions in face centered cubic alloys. Therefore, the heat flow directions are examined for various laser beam scanning patterns based on numerical modeling of heat transfer and fluid flow in three dimensions. Here we show that numerical modeling can not only provide a deeper understanding of the solidification growth patterns during the additive manufacturing, it also serves as a basis for customizing solidification textures which are important for properties and performance of components. PMID:26553246
Evolution of solidification texture during additive manufacturing
Wei, H. L.; Mazumder, J.; DebRoy, T.
2015-11-10
Striking differences in the solidification textures of a nickel based alloy owing to changes in laser scanning pattern during additive manufacturing are examined based on theory and experimental data. Understanding and controlling texture are important because it affects mechanical and chemical properties. Solidification texture depends on the local heat flow directions and competitive grain growth in one of the six <100> preferred growth directions in face centered cubic alloys. Furthermore, the heat flow directions are examined for various laser beam scanning patterns based on numerical modeling of heat transfer and fluid flow in three dimensions. Here we show that numerical modeling can not only provide a deeper understanding of the solidification growth patterns during the additive manufacturing, it also serves as a basis for customizing solidification textures which are important for properties and performance of components.
Evolution of solidification texture during additive manufacturing.
Wei, H L; Mazumder, J; DebRoy, T
2015-11-10
Striking differences in the solidification textures of a nickel based alloy owing to changes in laser scanning pattern during additive manufacturing are examined based on theory and experimental data. Understanding and controlling texture are important because it affects mechanical and chemical properties. Solidification texture depends on the local heat flow directions and competitive grain growth in one of the six <100> preferred growth directions in face centered cubic alloys. Therefore, the heat flow directions are examined for various laser beam scanning patterns based on numerical modeling of heat transfer and fluid flow in three dimensions. Here we show that numerical modeling can not only provide a deeper understanding of the solidification growth patterns during the additive manufacturing, it also serves as a basis for customizing solidification textures which are important for properties and performance of components.
Evolution of solidification texture during additive manufacturing
NASA Astrophysics Data System (ADS)
Wei, H. L.; Mazumder, J.; Debroy, T.
2015-11-01
Striking differences in the solidification textures of a nickel based alloy owing to changes in laser scanning pattern during additive manufacturing are examined based on theory and experimental data. Understanding and controlling texture are important because it affects mechanical and chemical properties. Solidification texture depends on the local heat flow directions and competitive grain growth in one of the six <100> preferred growth directions in face centered cubic alloys. Therefore, the heat flow directions are examined for various laser beam scanning patterns based on numerical modeling of heat transfer and fluid flow in three dimensions. Here we show that numerical modeling can not only provide a deeper understanding of the solidification growth patterns during the additive manufacturing, it also serves as a basis for customizing solidification textures which are important for properties and performance of components.
Additive manufacturing of hybrid circuits
Bell, Nelson S.; Sarobol, Pylin; Cook, Adam; Clem, Paul G.; Keicher, David M.; Hirschfeld, Deidre; Hall, Aaron Christopher
2016-03-26
There is a rising interest in developing functional electronics using additively manufactured components. Considerations in materials selection and pathways to forming hybrid circuits and devices must demonstrate useful electronic function; must enable integration; and must complement the complex shape, low cost, high volume, and high functionality of structural but generally electronically passive additively manufactured components. This article reviews several emerging technologies being used in industry and research/development to provide integration advantages of fabricating multilayer hybrid circuits or devices. First, we review a maskless, noncontact, direct write (DW) technology that excels in the deposition of metallic colloid inks for electrical interconnects. Second, we review a complementary technology, aerosol deposition (AD), which excels in the deposition of metallic and ceramic powder as consolidated, thick conformal coatings and is additionally patternable through masking. As a result, we show examples of hybrid circuits/devices integrated beyond 2-D planes, using combinations of DW or AD processes and conventional, established processes.
Numerical Modeling of Electroacoustic Logging Including Joule Heating
NASA Astrophysics Data System (ADS)
Plyushchenkov, Boris D.; Nikitin, Anatoly A.; Turchaninov, Victor I.
It is well known that electromagnetic field excites acoustic wave in a porous elastic medium saturated with fluid electrolyte due to electrokinetic conversion effect. Pride's equations describing this process are written in isothermal approximation. Update of these equations, which allows to take influence of Joule heating on acoustic waves propagation into account, is proposed here. This update includes terms describing the initiation of additional acoustic waves excited by thermoelastic stresses and the heat conduction equation with right side defined by Joule heating. Results of numerical modeling of several problems of propagation of acoustic waves excited by an electric field source with and without consideration of Joule heating effect in their statements are presented. From these results, it follows that influence of Joule heating should be taken into account at the numerical simulation of electroacoustic logging and at the interpretation of its log data.
Nonlinear dynamics of additive pulse modelocked lasers
Sucha, G.; Bolton, S.R.; Chemla, D.S.
1995-04-01
Nonlinear dynamics have been studied in a number of modelocked laser systems, primarily in actively modelocked systems. However, less attention has been paid to the dynamics of passively modelocked laser systems. With the recent revolutionary advances in femtosecond modelocked laser technology, the understanding of instabilities and dynamics in passively modelocked lasers is an important issue. Here, the authors present experimental and numerical studies of the dynamics of an additive-pulse modelocked (APM) color-center laser.
Numerical Hydrodynamics in Special Relativity.
Martí, José Maria; Müller, Ewald
2003-01-01
This review is concerned with a discussion of numerical methods for the solution of the equations of special relativistic hydrodynamics (SRHD). Particular emphasis is put on a comprehensive review of the application of high-resolution shock-capturing methods in SRHD. Results of a set of demanding test bench simulations obtained with different numerical SRHD methods are compared. Three applications (astrophysical jets, gamma-ray bursts and heavy ion collisions) of relativistic flows are discussed. An evaluation of various SRHD methods is presented, and future developments in SRHD are analyzed involving extension to general relativistic hydrodynamics and relativistic magneto-hydrodynamics. The review further provides FORTRAN programs to compute the exact solution of a 1D relativistic Riemann problem with zero and nonzero tangential velocities, and to simulate 1D relativistic flows in Cartesian Eulerian coordinates using the exact SRHD Riemann solver and PPM reconstruction.
Castle, Toen; Sussman, Daniel M; Tanis, Michael; Kamien, Randall D
2016-09-01
Kirigami uses bending, folding, cutting, and pasting to create complex three-dimensional (3D) structures from a flat sheet. In the case of lattice kirigami, this cutting and rejoining introduces defects into an underlying 2D lattice in the form of points of nonzero Gaussian curvature. A set of simple rules was previously used to generate a wide variety of stepped structures; we now pare back these rules to their minimum. This allows us to describe a set of techniques that unify a wide variety of cut-and-paste actions under the rubric of lattice kirigami, including adding new material and rejoining material across arbitrary cuts in the sheet. We also explore the use of more complex lattices and the different structures that consequently arise. Regardless of the choice of lattice, creating complex structures may require multiple overlapping kirigami cuts, where subsequent cuts are not performed on a locally flat lattice. Our additive kirigami method describes such cuts, providing a simple methodology and a set of techniques to build a huge variety of complex 3D shapes.
Ceramics with Different Additives
NASA Astrophysics Data System (ADS)
Wang, Juanjuan; Feng, Lajun; Lei, Ali; Zhao, Kang; Yan, Aijun
2014-09-01
Li2CO3, MgCO3, BaCO3, and Bi2O3 dopants were introduced into CaCu3Ti4O12 (CCTO) ceramics in order to improve the dielectric properties. The CCTO ceramics were prepared by conventional solid-state reaction method. The phase structure, microstructure, and dielectric behavior were carefully investigated. The pure structure without any impurity phases can be confirmed by the x-ray diffraction patterns. Scanning Electron Microscopy (SEM) analysis illuminated that the grains of Ca0.90Li0.20Cu3Ti4O12 ceramics were greater than that of pure CCTO. It was important for the properties of the CCTO ceramics to study the additives in complex impedance spectroscopy. It was found that the Ca0.90Li0.20Cu3Ti4O12 ceramics had the higher permittivity (>45000), the lower dielectric loss (<0.025) than those of CCTO at 1 kHz at room temperature and good temperature stability from -30 to 75 °C.
Castle, Toen; Sussman, Daniel M.; Tanis, Michael; Kamien, Randall D.
2016-01-01
Kirigami uses bending, folding, cutting, and pasting to create complex three-dimensional (3D) structures from a flat sheet. In the case of lattice kirigami, this cutting and rejoining introduces defects into an underlying 2D lattice in the form of points of nonzero Gaussian curvature. A set of simple rules was previously used to generate a wide variety of stepped structures; we now pare back these rules to their minimum. This allows us to describe a set of techniques that unify a wide variety of cut-and-paste actions under the rubric of lattice kirigami, including adding new material and rejoining material across arbitrary cuts in the sheet. We also explore the use of more complex lattices and the different structures that consequently arise. Regardless of the choice of lattice, creating complex structures may require multiple overlapping kirigami cuts, where subsequent cuts are not performed on a locally flat lattice. Our additive kirigami method describes such cuts, providing a simple methodology and a set of techniques to build a huge variety of complex 3D shapes. PMID:27679822
Inspection of additive-manufactured layered components.
Cerniglia, D; Scafidi, M; Pantano, A; Rudlin, J
2015-09-01
Laser powder deposition (LPD) is a rapid additive manufacturing process to produce, layer upon layer, 3D geometries or to repair high-value components. Currently there is no nondestructive technique that can guarantee absence of flaws in LPD products during manufacturing. In this paper a laser ultrasonic technique for in-line inspection of LPD components is proposed. Reference samples were manufactured from Inconel and machined flaws were created to establish the sensitivity of the technique. Numerical models of laser-generated ultrasonic waves have been created to gain a deeper understanding of physics, to optimize the set-up and to verify the experimental measurements. Results obtained on two sets of reference samples are shown. A proof-of-concept prototype has been demonstrated on some specific deposition samples with induced flaws, that were confirmed by an ultra-high sensitivity X-ray technique. Experimental outcomes prove that typical micro-defects due to the layer-by-layer deposition process, such as near-surface and surface flaws in a single layer deposit, can be detected.
IN718 Additive Manufacturing Properties and Influences
NASA Technical Reports Server (NTRS)
Lambert, Dennis M.
2015-01-01
The results of tensile, fracture, and fatigue testing of IN718 coupons produced using the selective laser melting (SLM) additive manufacturing technique are presented. The data have been "sanitized" to remove the numerical values, although certain references to material standards are provided. This document provides some knowledge of the effect of variation of controlled build parameters used in the SLM process, a snapshot of the capabilities of SLM in industry at present, and shares some of the lessons learned along the way. For the build parameter characterization, the parameters were varied over a range that was centered about the machine manufacturer's recommended value, and in each case they were varied individually, although some co-variance of those parameters would be expected. Tensile, fracture, and high-cycle fatigue properties equivalent to wrought IN718 are achievable with SLM-produced IN718. Build and post-build processes need to be determined and then controlled to established limits to accomplish this. It is recommended that a multi-variable evaluation, e.g., design-of experiment (DOE), of the build parameters be performed to better evaluate the co-variance of the parameters.
IN718 Additive Manufacturing Properties and Influences
NASA Technical Reports Server (NTRS)
Lambert, Dennis M.
2015-01-01
The results of tensile, fracture, and fatigue testing of IN718 coupons produced using the selective laser melting (SLM) additive manufacturing technique are presented. The data has been "generalized" to remove the numerical values, although certain references to material standards are provided. This document provides some knowledge of the effect of variation of controlled build parameters used in the SLM process, a snapshot of the capabilities of SLM in industry at present, and shares some of the lessons learned along the way. For the build parameter characterization, the parameters were varied over a range about the machine manufacturer's recommended value, and in each case they were varied individually, although some co-variance of those parameters would be expected. SLM-produced IN718, tensile, fracture, and high-cycle fatigue properties equivalent to wrought IN718 are achievable. Build and post-build processes need to be determined and then controlled to established limits to accomplish this. It is recommended that a multi-variable evaluation, e.g., design-of-experiment (DOE), of the build parameters be performed to better evaluate the co-variance of the parameters.
Additives in fibers and fabrics.
Barker, R H
1975-01-01
The additives and contaminants which occur in textile fibers vary widely, depending on the type of fiber and the pretreatment which it has received. Synthetic fibers such as nylon and polyester contain trace amounts of contaminants such as catalysts and catalyst deactivators which remain after the synthesis of the basic polymers. In addition, there are frequently a number of materials which are added to perform specific functions in almost all man-made fibers. Examples of these would include traces of metals or metal salts used as tracers for identification of specific lots of fiber, TiO2 or similar materials added as delustrants, and a host of organic species added for such special purposes as antistatic agents or flame retardants. There may also be considerable quantities of residual monomer or small oligomers dissolved in the polymer matrix. The situation becomes even more complex after the fibers are converted into fabric form. Numerous materials are applied at various stages of fabric preparation to act as lubricants, sizing agents, antistats, bleaches, and wetting agents to facilitate the processing, but these are normally removed before the fabric reaches the cutters of the ultimate consumers and therefore usually do not constitute potential hazards. However, there are many other chemical agents which are frequently added during the later stages of fabric preparation and which are not designed to be removed. Aside from dyes and printing pigments, the most common additive for apparel fabrics is a durable press treatment. This generally involves the use of materials capable of crosslinking cellulosics by reacting through such functions as N-methylolated amides or related compounds such as ureas and carbamates. These materials pose some potential hazards due to both the nitrogenous bases and the formaldehyde which they usually release. There is usually also some residual catalyst in fabrics which have received such treatments. Other types of chemical treatments
Numerical Speed of Sound and its Application to Schemes for all Speeds
NASA Technical Reports Server (NTRS)
Liou, Meng-Sing; Edwards, Jack R.
1999-01-01
The concept of "numerical speed of sound" is proposed in the construction of numerical flux. It is shown that this variable is responsible for the accurate resolution of' discontinuities, such as contacts and shocks. Moreover, this concept can he readily extended to deal with low speed and multiphase flows. As a results, the numerical dissipation for low speed flows is scaled with the local fluid speed, rather than the sound speed. Hence, the accuracy is enhanced the correct solution recovered, and the convergence rate improved. We also emphasize the role of mass flux and analyze the behavior of this flux. Study of mass flux is important because the numerical diffusivity introduced in it can be identified. In addition, it is the term common to all conservation equations. We show calculated results for a wide variety of flows to validate the effectiveness of using the numerical speed of sound concept in constructing the numerical flux. We especially aim at achieving these two goals: (1) improving accuracy and (2) gaining convergence rates for all speed ranges. We find that while the performance at high speed range is maintained, the flux now has the capability of performing well even with the low: speed flows. Thanks to the new numerical speed of sound, the convergence is even enhanced for the flows outside of the low speed range. To realize the usefulness of the proposed method in engineering problems, we have also performed calculations for complex 3D turbulent flows and the results are in excellent agreement with data.
Information Based Numerical Practice.
1987-02-01
N I IIi I2 LA 1.6 liii I~JIIN MARYLAND COLLEGE PARK CAMPUS INSTITUTE FOR PHYSICAL SCIENCE AND TECHNOLOGY Technical Note S1-1059 INFORMATION BASED...K-0169 9. PERFORMING ORGANIZATION NMEU AMC ADDRESS 16. PROGRAM CELEMNT. PROJECT. TASK AREA & WORK UNIT NUNSERS, Institute for Physical Science and...BASED NUMERICAL PRACTICE I. Babuska Institute for Physical Science and Technology University of Maryland, College Park, MD 20740 a Partially supported by
Hybrid undulator numerical optimization
Hairetdinov, A.H.; Zukov, A.A.
1995-12-31
3D properties of the hybrid undulator scheme arc studied numerically using PANDIRA code. It is shown that there exist two well defined sets of undulator parameters which provide either maximum on-axis field amplitude or minimal higher harmonics amplitude of the basic undulator field. Thus the alternative between higher field amplitude or pure sinusoidal field exists. The behavior of the undulator field amplitude and harmonics structure for a large set of (undulator gap)/(undulator wavelength) values is demonstrated.
Numerical Modeling of Airblast.
1987-06-01
REPORT SAIC 87/1701 June 1987 Dr.. Submitted to: cp Dr. Jay Boris Laboratory for Computational Physics Accet F4,r Naval Research Laboratory I...boundary layer physical assumptions provides an unsteady prediction of the mass flux emerging from the ground. This model was first proposed by Mirels...the physics modeled will be explained. High explosive dust cloud simulation provides a research path when combined with numerical calculations can lead
In Praise of Numerical Computation
NASA Astrophysics Data System (ADS)
Yap, Chee K.
Theoretical Computer Science has developed an almost exclusively discrete/algebraic persona. We have effectively shut ourselves off from half of the world of computing: a host of problems in Computational Science & Engineering (CS&E) are defined on the continuum, and, for them, the discrete viewpoint is inadequate. The computational techniques in such problems are well-known to numerical analysis and applied mathematics, but are rarely discussed in theoretical algorithms: iteration, subdivision and approximation. By various case studies, I will indicate how our discrete/algebraic view of computing has many shortcomings in CS&E. We want embrace the continuous/analytic view, but in a new synthesis with the discrete/algebraic view. I will suggest a pathway, by way of an exact numerical model of computation, that allows us to incorporate iteration and approximation into our algorithms’ design. Some recent results give a peek into how this view of algorithmic development might look like, and its distinctive form suggests the name “numerical computational geometry” for such activities.
Numerical simulation of conservation laws
NASA Technical Reports Server (NTRS)
Chang, Sin-Chung; To, Wai-Ming
1992-01-01
A new numerical framework for solving conservation laws is being developed. This new approach differs substantially from the well established methods, i.e., finite difference, finite volume, finite element and spectral methods, in both concept and methodology. The key features of the current scheme include: (1) direct discretization of the integral forms of conservation laws, (2) treating space and time on the same footing, (3) flux conservation in space and time, and (4) unified treatment of the convection and diffusion fluxes. The model equation considered in the initial study is the standard one dimensional unsteady constant-coefficient convection-diffusion equation. In a stability study, it is shown that the principal and spurious amplification factors of the current scheme, respectively, are structurally similar to those of the leapfrog/DuFort-Frankel scheme. As a result, the current scheme has no numerical diffusion in the special case of pure convection and is unconditionally stable in the special case of pure diffusion. Assuming smooth initial data, it will be shown theoretically and numerically that, by using an easily determined optimal time step, the accuracy of the current scheme may reach a level which is several orders of magnitude higher than that of the MacCormack scheme, with virtually identical operation count.
Numerical ability predicts mortgage default.
Gerardi, Kristopher; Goette, Lorenz; Meier, Stephan
2013-07-09
Unprecedented levels of US subprime mortgage defaults precipitated a severe global financial crisis in late 2008, plunging much of the industrialized world into a deep recession. However, the fundamental reasons for why US mortgages defaulted at such spectacular rates remain largely unknown. This paper presents empirical evidence showing that the ability to perform basic mathematical calculations is negatively associated with the propensity to default on one's mortgage. We measure several aspects of financial literacy and cognitive ability in a survey of subprime mortgage borrowers who took out loans in 2006 and 2007, and match them to objective, detailed administrative data on mortgage characteristics and payment histories. The relationship between numerical ability and mortgage default is robust to controlling for a broad set of sociodemographic variables, and is not driven by other aspects of cognitive ability. We find no support for the hypothesis that numerical ability impacts mortgage outcomes through the choice of the mortgage contract. Rather, our results suggest that individuals with limited numerical ability default on their mortgage due to behavior unrelated to the initial choice of their mortgage.
Resolution requirements for numerical simulations of transition
NASA Technical Reports Server (NTRS)
Zang, Thomas A.; Krist, Steven E.; Hussaini, M. Yousuff
1989-01-01
The resolution requirements for direct numerical simulations of transition to turbulence are investigated. A reliable resolution criterion is determined from the results of several detailed simulations of channel and boundary-layer transition.
Numerical Stimulation of Multicomponent Chromatography Using Spreadsheets.
ERIC Educational Resources Information Center
Frey, Douglas D.
1990-01-01
Illustrated is the use of spreadsheet programs for implementing finite difference numerical simulations of chromatography as an instructional tool in a separations course. Discussed are differential equations, discretization and integration, spreadsheet development, computer requirements, and typical simulation results. (CW)
Value-Engineering Review for Numerical Control
NASA Technical Reports Server (NTRS)
Warner, J. L.
1984-01-01
Selecting parts for conversion from conventional machining to numerical control, value-engineering review performed for every part to identify potential changes to part design that result in increased production efficiency.
Numerical reconstruction of optical surfaces.
Nam, Jayoung; Rubinstein, Jacob
2008-07-01
There are several problems in optics that involve the reconstruction of surfaces such as wavefronts, reflectors, and lenses. The reconstruction problem often leads to a system of first-order differential equations for the unknown surface. We compare several numerical methods for integrating differential equations of this kind. One class of methods involves a direct integration. It is shown that such a technique often fails in practice. We thus consider one method that provides an approximate direct integration; we show that it is always converging and that it provides a stable, accurate solution even in the presence of measurement noise. In addition, we consider a number of methods that are based on converting the original equation into a minimization problem.
Numerical optimization using flow equations.
Punk, Matthias
2014-12-01
We develop a method for multidimensional optimization using flow equations. This method is based on homotopy continuation in combination with a maximum entropy approach. Extrema of the optimizing functional correspond to fixed points of the flow equation. While ideas based on Bayesian inference such as the maximum entropy method always depend on a prior probability, the additional step in our approach is to perform a continuous update of the prior during the homotopy flow. The prior probability thus enters the flow equation only as an initial condition. We demonstrate the applicability of this optimization method for two paradigmatic problems in theoretical condensed matter physics: numerical analytic continuation from imaginary to real frequencies and finding (variational) ground states of frustrated (quantum) Ising models with random or long-range antiferromagnetic interactions.
Numerical optimization using flow equations
NASA Astrophysics Data System (ADS)
Punk, Matthias
2014-12-01
We develop a method for multidimensional optimization using flow equations. This method is based on homotopy continuation in combination with a maximum entropy approach. Extrema of the optimizing functional correspond to fixed points of the flow equation. While ideas based on Bayesian inference such as the maximum entropy method always depend on a prior probability, the additional step in our approach is to perform a continuous update of the prior during the homotopy flow. The prior probability thus enters the flow equation only as an initial condition. We demonstrate the applicability of this optimization method for two paradigmatic problems in theoretical condensed matter physics: numerical analytic continuation from imaginary to real frequencies and finding (variational) ground states of frustrated (quantum) Ising models with random or long-range antiferromagnetic interactions.
A novel high-efficiency methodology for metal additive manufacturing
NASA Astrophysics Data System (ADS)
Du, Jun; Wei, Zhengying; Wang, Xin; Fang, Xuewei; Zhao, Guangxi
2016-11-01
Metal additive manufacturing (AM) offers unrivalled design freedom with the ability to manufacture complex parts. However, the high capital costs and slow throughput printing have severely restricted its application. In this paper, a new metal AM process, referred to as the "metal fused-coating additive manufacturing (MFCAM)", was developed for highly efficient metal parts production. This new process is the combination of metal fused-coating process and laser surface melting process. A two-dimensional numerical model was established to provide an insight into the primary thermo-physical phenomena occurring in the MFCAM process. Experiments of single-track formation were conducted using MFCAM to validate the feasibility of the proposed process. The good agreement between experimental and simulated results demonstrated the reasonableness of the established models.
Numerical simulations of cryogenic cavitating flows
NASA Astrophysics Data System (ADS)
Kim, Hyunji; Kim, Hyeongjun; Min, Daeho; Kim, Chongam
2015-12-01
The present study deals with a numerical method for cryogenic cavitating flows. Recently, we have developed an accurate and efficient baseline numerical scheme for all-speed water-gas two-phase flows. By extending such progress, we modify the numerical dissipations to be properly scaled so that it does not show any deficiencies in low Mach number regions. For dealing with cryogenic two-phase flows, previous EOS-dependent shock discontinuity sensing term is replaced with a newly designed EOS-free one. To validate the proposed numerical method, cryogenic cavitating flows around hydrofoil are computed and the pressure and temperature depression effect in cryogenic cavitation are demonstrated. Compared with Hord's experimental data, computed results are turned out to be satisfactory. Afterwards, numerical simulations of flow around KARI turbopump inducer in liquid rocket are carried out under various flow conditions with water and cryogenic fluids, and the difference in inducer flow physics depending on the working fluids are examined.
Infants use relative numerical group size to infer social dominance
Pun, Anthea; Birch, Susan A. J.; Baron, Andrew Scott
2016-01-01
Detecting dominance relationships, within and across species, provides a clear fitness advantage because this ability helps individuals assess their potential risk of injury before engaging in a competition. Previous research has demonstrated that 10- to 13-mo-old infants can represent the dominance relationship between two agents in terms of their physical size (larger agent = more dominant), whereas younger infants fail to do so. It is unclear whether infants younger than 10 mo fail to represent dominance relationships in general, or whether they lack sensitivity to physical size as a cue to dominance. Two studies explored whether infants, like many species across the animal kingdom, use numerical group size to assess dominance relationships and whether this capacity emerges before their sensitivity to physical size. A third study ruled out an alternative explanation for our findings. Across these studies, we report that infants 6–12 mo of age use numerical group size to infer dominance relationships. Specifically, preverbal infants expect an agent from a numerically larger group to win in a right-of-way competition against an agent from a numerically smaller group. In addition, this is, to our knowledge, the first study to demonstrate that infants 6–9 mo of age are capable of understanding social dominance relations. These results demonstrate that infants’ understanding of social dominance relations may be based on evolutionarily relevant cues and reveal infants’ early sensitivity to an important adaptive function of social groups. PMID:26884199
Numerical judgments by chimpanzees (Pan troglodytes) in a token economy.
Beran, Michael J; Evans, Theodore A; Hoyle, Daniel
2011-04-01
We presented four chimpanzees with a series of tasks that involved comparing two token sets or comparing a token set to a quantity of food. Selected tokens could be exchanged for food items on a one-to-one basis. Chimpanzees successfully selected the larger numerical set for comparisons of 1 to 5 items when both sets were visible and when sets were presented through one-by-one addition of tokens into two opaque containers. Two of four chimpanzees used the number of tokens and food items to guide responding in all conditions, rather than relying on token color, size, total amount, or duration of set presentation. These results demonstrate that judgments of simultaneous and sequential sets of stimuli are made by some chimpanzees on the basis of the numerousness of sets rather than other non-numerical dimensions. The tokens were treated as equivalent to food items on the basis of their numerousness, and the chimpanzees maximized reward by choosing the larger number of items in all situations.
Numerical and measured data from the 3D salt canopy physical modeling project
Bradley, C.; House, L.; Fehler, M.; Pearson, J.; TenCate, J.; Wiley, R.
1997-11-01
The evolution of salt structures in the Gulf of Mexico have been shown to provide a mechanism for the trapping of significant hydrocarbon reserves. Most of these structures have complex geometries relative to the surrounding sedimentary layers. This aspect in addition to high velocities within the salt tend to scatter and defocus seismic energy and make imaging of subsalt lithology extremely difficult. An ongoing program the SEG/EAEG modeling project (Aminzadeh et al. 1994a: Aminzadeh et al. 1994b: Aminzadeh et al. 1995), and a follow-up project funded as part of the Advanced Computational Technology Initiative (ACTI) (House et al. 1996) have sought to investigate problems with imaging beneath complex salt structures using numerical modeling and more recently, construction of a physical model patterned after the numerical subsalt model (Wiley and McKnight. 1996). To date, no direct comparison of the numerical and physical aspects of these models has been attempted. We present the results of forward modeling a numerical realization of the 3D salt canopy physical model with the French Petroleum Institute (IFP) acoustic finite difference algorithm used in the numerical subsalt tests. We compare the results from the physical salt canopy model, the acoustic modeling of the physical/numerical model and the original numerical SEG/EAEG Salt Model. We will be testing the sensitivity of migration to the presence of converted shear waves and acquisition geometry.
"Recognizing Numerical Constants"
NASA Technical Reports Server (NTRS)
Bailey, David H.; Craw, James M. (Technical Monitor)
1995-01-01
The advent of inexpensive, high performance computer and new efficient algorithms have made possible the automatic recognition of numerically computed constants. In other words, techniques now exist for determining, within certain limits, whether a computed real or complex number can be written as a simple expression involving the classical constants of mathematics. In this presentation, some of the recently discovered techniques for constant recognition, notably integer relation detection algorithms, will be presented. As an application of these methods, the author's recent work in recognizing "Euler sums" will be described in some detail.
Physical and numerical modeling of Joule-heated melters
NASA Astrophysics Data System (ADS)
Eyler, L. L.; Skarda, R. J.; Crowder, R. S., III; Trent, D. S.; Reid, C. R.; Lessor, D. L.
1985-10-01
The Joule-heated ceramic-lined melter is an integral part of the high level waste immobilization process under development by the US Department of Energy. Scaleup and design of this waste glass melting furnace requires an understanding of the relationships between melting cavity design parameters and the furnace performance characteristics such as mixing, heat transfer, and electrical requirements. Developing empirical models of these relationships through actual melter testing with numerous designs would be a very costly and time consuming task. Additionally, the Pacific Northwest Laboratory (PNL) has been developing numerical models that simulate a Joule-heated melter for analyzing melter performance. This report documents the method used and results of this modeling effort. Numerical modeling results are compared with the more conventional, physical modeling results to validate the approach. Also included are the results of numerically simulating an operating research melter at PNL. Physical Joule-heated melters modeling results used for qualiying the simulation capabilities of the melter code included: (1) a melter with a single pair of electrodes and (2) a melter with a dual pair (two pairs) of electrodes. The physical model of the melter having two electrode pairs utilized a configuration with primary and secondary electrodes. The principal melter parameters (the ratio of power applied to each electrode pair, modeling fluid depth, electrode spacing) were varied in nine tests of the physical model during FY85. Code predictions were made for five of these tests. Voltage drops, temperature field data, and electric field data varied in their agreement with the physical modeling results, but in general were judged acceptable.
Physical and numerical modeling of Joule-heated melters
Eyler, L.L.; Skarda, R.J.; Crowder, R.S. III; Trent, D.S.; Reid, C.R.; Lessor, D.L.
1985-10-01
The Joule-heated ceramic-lined melter is an integral part of the high level waste immobilization process under development by the US Department of Energy. Scaleup and design of this waste glass melting furnace requires an understanding of the relationships between melting cavity design parameters and the furnace performance characteristics such as mixing, heat transfer, and electrical requirements. Developing empirical models of these relationships through actual melter testing with numerous designs would be a very costly and time consuming task. Additionally, the Pacific Northwest Laboratory (PNL) has been developing numerical models that simulate a Joule-heated melter for analyzing melter performance. This report documents the method used and results of this modeling effort. Numerical modeling results are compared with the more conventional, physical modeling results to validate the approach. Also included are the results of numerically simulating an operating research melter at PNL. Physical Joule-heated melters modeling results used for qualiying the simulation capabilities of the melter code included: (1) a melter with a single pair of electrodes and (2) a melter with a dual pair (two pairs) of electrodes. The physical model of the melter having two electrode pairs utilized a configuration with primary and secondary electrodes. The principal melter parameters (the ratio of power applied to each electrode pair, modeling fluid depth, electrode spacing) were varied in nine tests of the physical model during FY85. Code predictions were made for five of these tests. Voltage drops, temperature field data, and electric field data varied in their agreement with the physical modeling results, but in general were judged acceptable. 14 refs., 79 figs., 17 tabs.
Numerical methods for multibody systems
NASA Technical Reports Server (NTRS)
Glowinski, Roland; Nasser, Mahmoud G.
1994-01-01
This article gives a brief summary of some results obtained by Nasser on modeling and simulation of inequality problems in multibody dynamics. In particular, the augmented Lagrangian method discussed here is applied to a constrained motion problem with impulsive inequality constraints. A fundamental characteristic of the multibody dynamics problem is the lack of global convexity of its Lagrangian. The problem is transformed into a convex analysis problem by localization (piecewise linearization), where the augmented Lagrangian has been successfully used. A model test problem is considered and a set of numerical experiments is presented.
On Sums of Numerical Series and Fourier Series
ERIC Educational Resources Information Center
Pavao, H. Germano; de Oliveira, E. Capelas
2008-01-01
We discuss a class of trigonometric functions whose corresponding Fourier series, on a conveniently chosen interval, can be used to calculate several numerical series. Particular cases are presented and two recent results involving numerical series are recovered. (Contains 1 note.)
Entropy Splitting and Numerical Dissipation
NASA Technical Reports Server (NTRS)
Yee, H. C.; Vinokur, M.; Djomehri, M. J.
1999-01-01
A rigorous stability estimate for arbitrary order of accuracy of spatial central difference schemes for initial-boundary value problems of nonlinear symmetrizable systems of hyperbolic conservation laws was established recently by Olsson and Oliger (1994) and Olsson (1995) and was applied to the two-dimensional compressible Euler equations for a perfect gas by Gerritsen and Olsson (1996) and Gerritsen (1996). The basic building block in developing the stability estimate is a generalized energy approach based on a special splitting of the flux derivative via a convex entropy function and certain homogeneous properties. Due to some of the unique properties of the compressible Euler equations for a perfect gas, the splitting resulted in the sum of a conservative portion and a non-conservative portion of the flux derivative. hereafter referred to as the "Entropy Splitting." There are several potential desirable attributes and side benefits of the entropy splitting for the compressible Euler equations that were not fully explored in Gerritsen and Olsson. The paper has several objectives. The first is to investigate the choice of the arbitrary parameter that determines the amount of splitting and its dependence on the type of physics of current interest to computational fluid dynamics. The second is to investigate in what manner the splitting affects the nonlinear stability of the central schemes for long time integrations of unsteady flows such as in nonlinear aeroacoustics and turbulence dynamics. If numerical dissipation indeed is needed to stabilize the central scheme, can the splitting help minimize the numerical dissipation compared to its un-split cousin? Extensive numerical study on the vortex preservation capability of the splitting in conjunction with central schemes for long time integrations will be presented. The third is to study the effect of the non-conservative proportion of splitting in obtaining the correct shock location for high speed complex shock
Foehn wind detection using numerical modelling
NASA Astrophysics Data System (ADS)
Irimescu, A.; Caian, M.
2010-09-01
In Romania, foehn is a short-lived atmospheric phenomenon, of a low to average intensity, not always highlighted by weather station observations. When such situations occur additional data are resorted to, rendering a continuous, aggregate image, in comparison to the punctual information yielded by weather stations. This paper aims to describe how foehn is detected in northern Oltenia (the Inner Carpathian-Balkan Curvature), using numerical modelling. Results generated by the RegCM3 Regional Climatic Model thus represent an undisputed tool, their most important advantage being the 10-km spatial resolution. The presence of foehn in northern Oltenia and its climatic peculiarities have been disclosed through the analysis in time and space of the meteorological elements specific to the phenomenon (air temperature, wind speed and direction etc) over a 40-year interval (1961-2000). The paper presents a new methodology that can be used to estimate the probability of production and the foehn characteristics (intensity, duration etc.). Interpretation of the RegCM3 model results has led to the statistical analysis of foehn occurrences within the studied area during the cold season (December, January and February). The resulted climatology, with fine resolution, can be used in foehn forecast of predictability.
Confidence in Numerical Simulations
Hemez, Francois M.
2015-02-23
This PowerPoint presentation offers a high-level discussion of uncertainty, confidence and credibility in scientific Modeling and Simulation (M&S). It begins by briefly evoking M&S trends in computational physics and engineering. The first thrust of the discussion is to emphasize that the role of M&S in decision-making is either to support reasoning by similarity or to “forecast,” that is, make predictions about the future or extrapolate to settings or environments that cannot be tested experimentally. The second thrust is to explain that M&S-aided decision-making is an exercise in uncertainty management. The three broad classes of uncertainty in computational physics and engineering are variability and randomness, numerical uncertainty and model-form uncertainty. The last part of the discussion addresses how scientists “think.” This thought process parallels the scientific method where by a hypothesis is formulated, often accompanied by simplifying assumptions, then, physical experiments and numerical simulations are performed to confirm or reject the hypothesis. “Confidence” derives, not just from the levels of training and experience of analysts, but also from the rigor with which these assessments are performed, documented and peer-reviewed.
NASA Astrophysics Data System (ADS)
Shoev, G. V.; Bondar, Ye. A.; Oblapenko, G. P.; Kustova, E. V.
2016-03-01
Various issues of numerical simulation of supersonic gas flows with allowance for thermochemical nonequilibrium on the basis of fluid dynamic equations in the two-temperature approximation are discussed. The computational tool for modeling flows with thermochemical nonequilibrium is the commercial software package ANSYS Fluent with an additional userdefined open-code module. A comparative analysis of results obtained by various models of vibration-dissociation coupling in binary gas mixtures of nitrogen and oxygen is performed. Results of numerical simulations are compared with available experimental data.
Numerical simulations of an oblique detonation wave engine
NASA Technical Reports Server (NTRS)
Cambier, Jean-Luc; Adelman, Henry; Menees, Gene P.
1988-01-01
An account is given of the numerical methods employed in a code for the simulation of supersonic combustion, which is then applied to the simulation of attached detonations and flames associated with the oblique-detonation wave supersonic combustor concept. The addition of heat by a detonation wave results in a shorter combustor than can be obtained in more conventional scramjet designs. Pure oblique detonations have been produced in a stoichiometric, uniformly mixed hydrogen/air stream; the wave rotates upstream with energy release, according to simple analytical arguments. Flow visualization maps for Mach number and temperature are presented.
The functional architectures of addition and subtraction: Network discovery using fMRI and DCM.
Yang, Yang; Zhong, Ning; Friston, Karl; Imamura, Kazuyuki; Lu, Shengfu; Li, Mi; Zhou, Haiyan; Wang, Haiyuan; Li, Kuncheng; Hu, Bin
2017-03-27
The neuronal mechanisms underlying arithmetic calculations are not well understood but the differences between mental addition and subtraction could be particularly revealing. Using fMRI and dynamic causal modeling (DCM), this study aimed to identify the distinct neuronal architectures engaged by the cognitive processes of simple addition and subtraction. Our results revealed significantly greater activation during subtraction in regions along the dorsal pathway, including the left inferior frontal gyrus (IFG), middle portion of dorsolateral prefrontal cortex (mDLPFC), and supplementary motor area (SMA), compared with addition. Subsequent analysis of the underlying changes in connectivity - with DCM - revealed a common circuit processing basic (numeric) attributes and the retrieval of arithmetic facts. However, DCM showed that addition was more likely to engage (numeric) retrieval-based circuits in the left hemisphere, while subtraction tended to draw on (magnitude) processing in bilateral parietal cortex, especially the right intraparietal sulcus (IPS). Our findings endorse previous hypotheses about the differences in strategic implementation, dominant hemisphere, and the neuronal circuits underlying addition and subtraction. Moreover, for simple arithmetic, our connectivity results suggest that subtraction calls on more complex processing than addition: auxiliary phonological, visual, and motor processes, for representing numbers, were engaged by subtraction, relative to addition. Hum Brain Mapp, 2017. © 2017 Wiley Periodicals, Inc.
Numerical solution of a tunneling equation
Wang, C.Y.; Carter, M.D.; Batchelor, D.B.; Jaeger, E.F.
1994-04-01
A numerical method is presented to solve mode conversion equations resulting from the use of radio frequency (rf) waves to heat plasmas. The solutions of the mode conversion equations contain exponentially growing modes, and ordinary numerical techniques give large errors. To avoid the unphysical growing modes, a set of boundary conditions are found, that eliminate the unphysical modes. The mode conversion equations are then solved with the boundary conditions as a standard two-point boundary value problem. A tunneling equation (one of the mode conversion equations without power absorption) is solved as a specific example of this numerical technique although the technique itself is very general and can be easily applied to solve any mode conversion equation. The results from the numerical calculation agree very well with those found from asymptotic analysis.
Additive manufacturing of hybrid circuits
Bell, Nelson S.; Sarobol, Pylin; Cook, Adam; ...
2016-03-26
There is a rising interest in developing functional electronics using additively manufactured components. Considerations in materials selection and pathways to forming hybrid circuits and devices must demonstrate useful electronic function; must enable integration; and must complement the complex shape, low cost, high volume, and high functionality of structural but generally electronically passive additively manufactured components. This article reviews several emerging technologies being used in industry and research/development to provide integration advantages of fabricating multilayer hybrid circuits or devices. First, we review a maskless, noncontact, direct write (DW) technology that excels in the deposition of metallic colloid inks for electrical interconnects.more » Second, we review a complementary technology, aerosol deposition (AD), which excels in the deposition of metallic and ceramic powder as consolidated, thick conformal coatings and is additionally patternable through masking. As a result, we show examples of hybrid circuits/devices integrated beyond 2-D planes, using combinations of DW or AD processes and conventional, established processes.« less
Shale JP-4 Additive Evaluation
1986-10-01
8217. •% . , ’ ,,,r ,% . -- - ,.-. ’ ’ 4,w% %’. " - ,’ . . . * ’, .* . TABLE OF CONTENTS .4q ,4 . * SECTION PAGE I. INTRODUCTION 1 II. TEST PARAMETERS 2 1...42 PRECEDING PAGE BLANK TABLE OF CONTENTS (CON’T) SECT ION PAGE V. CONCLUSIONS 44 REFERENCES 46 APPENDIX A Drum to Test Sample Relationship 47 APPENDIX...B.O.C.L.E. Results 40 vii LIST OF TABLES TABLE PAGE 1 Antioxidants 3 2 Raw Shale/Petroleum Fuel Properties 10 3 Drum Sample Additive Content 13 4
Using PASCAL for numerical analysis
NASA Technical Reports Server (NTRS)
Volper, D.; Miller, T. C.
1978-01-01
The data structures and control structures of PASCAL enhance the coding ability of the programmer. Proposed extensions to the language further increase its usefulness in writing numeric programs and support packages for numeric programs.
Perspectives in numerical astrophysics:
NASA Astrophysics Data System (ADS)
Reverdy, V.
2016-12-01
In this discussion paper, we investigate the current and future status of numerical astrophysics and highlight key questions concerning the transition to the exascale era. We first discuss the fact that one of the main motivation behind high performance simulations should not be the reproduction of observational or experimental data, but the understanding of the emergence of complexity from fundamental laws. This motivation is put into perspective regarding the quest for more computational power and we argue that extra computational resources can be used to gain in abstraction. Then, the readiness level of present-day simulation codes in regard to upcoming exascale architecture is examined and two major challenges are raised concerning both the central role of data movement for performances and the growing complexity of codes. Software architecture is finally presented as a key component to make the most of upcoming architectures while solving original physics problems.
Numerical relativity beyond astrophysics.
Garfinkle, David
2017-01-01
Though the main applications of computer simulations in relativity are to astrophysical systems such as black holes and neutron stars, nonetheless there are important applications of numerical methods to the investigation of general relativity as a fundamental theory of the nature of space and time. This paper gives an overview of some of these applications. In particular we cover (i) investigations of the properties of spacetime singularities such as those that occur in the interior of black holes and in big bang cosmology. (ii) investigations of critical behavior at the threshold of black hole formation in gravitational collapse. (iii) investigations inspired by string theory, in particular analogs of black holes in more than 4 spacetime dimensions and gravitational collapse in spacetimes with a negative cosmological constant.
Numerical relativity beyond astrophysics
NASA Astrophysics Data System (ADS)
Garfinkle, David
2017-01-01
Though the main applications of computer simulations in relativity are to astrophysical systems such as black holes and neutron stars, nonetheless there are important applications of numerical methods to the investigation of general relativity as a fundamental theory of the nature of space and time. This paper gives an overview of some of these applications. In particular we cover (i) investigations of the properties of spacetime singularities such as those that occur in the interior of black holes and in big bang cosmology. (ii) investigations of critical behavior at the threshold of black hole formation in gravitational collapse. (iii) investigations inspired by string theory, in particular analogs of black holes in more than 4 spacetime dimensions and gravitational collapse in spacetimes with a negative cosmological constant.
Numerical Simulations of Thermographic Responses in Composites
NASA Technical Reports Server (NTRS)
Winfree, William P.; Cramer, K. Elliot; Zalameda, Joseph N.; Howell, Patricia A.
2015-01-01
Numerical simulations of thermographic responses in composite materials have been a useful for evaluating and optimizing thermographic analysis techniques. Numerical solutions are particularly beneficial for thermographic techniques, since the fabrication of specimens with realistic flaws is difficult. Simulations are presented with different ply layups that incorporated the anisotropic thermal properties that exist in each ply. The results are compared to analytical series solutions and thermal measurements on composites with flat bottom holes and delaminations.
Numerical Continuation of Hamiltonian Relative Periodic Orbits
NASA Astrophysics Data System (ADS)
Wulff, Claudia; Schebesch, Andreas
2008-08-01
The bifurcation theory and numerics of periodic orbits of general dynamical systems is well developed, and in recent years, there has been rapid progress in the development of a bifurcation theory for dynamical systems with structure, such as symmetry or symplecticity. But as yet, there are few results on the numerical computation of those bifurcations. The methods we present in this paper are a first step toward a systematic numerical analysis of generic bifurcations of Hamiltonian symmetric periodic orbits and relative periodic orbits (RPOs). First, we show how to numerically exploit spatio-temporal symmetries of Hamiltonian periodic orbits. Then we describe a general method for the numerical computation of RPOs persisting from periodic orbits in a symmetry breaking bifurcation. Finally, we present an algorithm for the numerical continuation of non-degenerate Hamiltonian relative periodic orbits with regular drift-momentum pair. Our path following algorithm is based on a multiple shooting algorithm for the numerical computation of periodic orbits via an adaptive Poincaré section and a tangential continuation method with implicit reparametrization. We apply our methods to continue the famous figure eight choreography of the three-body system. We find a relative period doubling bifurcation of the planar rotating eight family and compute the rotating choreographies bifurcating from it.
Numeric Databases in the Sciences.
ERIC Educational Resources Information Center
Meschel, S. V.
1984-01-01
Provides exploration into types of numeric databases available (also known as source databases, nonbibliographic databases, data-files, data-banks, fact banks); examines differences and similarities between bibliographic and numeric databases; identifies disciplines that utilize numeric databases; and surveys representative examples in the…
Analytical and numerical investigation on nonlinear internal gravity waves
NASA Astrophysics Data System (ADS)
Kshevetskii, S. P.
The propagation of long, weakly nonlinear internal waves in a stratified gas is studied. Hydrodynamic equations for an ideal fluid with the perfect gas law describe the atmospheric gas behaviour. If we neglect the term Ͽ dw/dt (product of the density and vertical acceleration), we come to a so-called quasistatic model, while we name the full hydro-dynamic model as a nonquasistatic one. Both quasistatic and nonquasistatic models are used for wave simulation and the models are compared among themselves. It is shown that a smooth classical solution of a nonlinear quasistatic problem does not exist for all t because a gradient catastrophe of non-linear internal waves occurs. To overcome this difficulty, we search for the solution of the quasistatic problem in terms of a generalised function theory as a limit of special regularised equations containing some additional dissipation term when the dissipation factor vanishes. It is shown that such solutions of the quasistatic problem qualitatively differ from solutions of a nonquasistatic nature. It is explained by the fact that in a nonquasistatic model the vertical acceleration term plays the role of a regularizator with respect to a quasistatic model, while the solution qualitatively depends on the regularizator used. The numerical models are compared with some analytical results. Within the framework of the analytical model, any internal wave is described as a system of wave modes; each wave mode interacts with others due to equation non-linearity. In the principal order of a perturbation theory, each wave mode is described by some equation of a KdV type. The analytical model reveals that, in a nonquasistatic model, an internal wave should disintegrate into solitons. The time of wave disintegration into solitons, the scales and amount of solitons generated are important characteristics of the non-linear process; they are found with the help of analytical and numerical investigations. Satisfactory coincidence of
3D Numerical simulations of oblique subduction
NASA Astrophysics Data System (ADS)
Malatesta, C.; Gerya, T.; Scambelluri, M.; Crispini, L.; Federico, L.; Capponi, G.
2012-04-01
In the past 2D numerical studies (e.g. Gerya et al., 2002; Gorczyk et al., 2007; Malatesta et al., 2012) provided evidence that during intraoceanic subduction a serpentinite channel forms above the downgoing plate. This channel forms as a result of hydration of the mantle wedge by uprising slab-fluids. Rocks buried at high depths are finally exhumed within this buoyant low-viscosity medium. Convergence rate in these 2D models was described by a trench-normal component of velocity. Several present and past subduction zones worldwide are however driven by oblique convergence between the plates, where trench-normal motion of the subducting slab is coupled with trench-parallel displacement of the plates. Can the exhumation mechanism and the exhumation rates of high-pressure rocks be affected by the shear component of subduction? And how uprise of these rocks can vary along the plate margin? We tried to address these questions performing 3D numerical models that simulate an intraoceanic oblique subduction. The models are based on thermo-mechanical equations that are solved with finite differences method and marker-in-cell techniques combined with multigrid approach (Gerya, 2010). In most of the models a narrow oceanic basin (500 km-wide) surrounded by continental margins is depicted. The basin is floored by either layered or heterogeneous oceanic lithosphere with gabbro as discrete bodies in serpentinized peridotite and a basaltic layer on the top. A weak zone in the mantle is prescribed to control the location of subduction initiation and therefore the plate margins geometry. Finally, addition of a third dimension in the simulations allowed us to test the role of different plate margin geometries on oblique subduction dynamics. In particular in each model we modified the dip angle of the weak zone and its "lateral" geometry (e.g. continuous, segmented). We consider "continuous" weak zones either parallel or increasingly moving away from the continental margins
An Additive Manufacturing Test Artifact
Moylan, Shawn; Slotwinski, John; Cooke, April; Jurrens, Kevin; Donmez, M Alkan
2014-01-01
A test artifact, intended for standardization, is proposed for the purpose of evaluating the performance of additive manufacturing (AM) systems. A thorough analysis of previously proposed AM test artifacts as well as experience with machining test artifacts have inspired the design of the proposed test artifact. This new artifact is designed to provide a characterization of the capabilities and limitations of an AM system, as well as to allow system improvement by linking specific errors measured in the test artifact to specific sources in the AM system. The proposed test artifact has been built in multiple materials using multiple AM technologies. The results of several of the builds are discussed, demonstrating how the measurement results can be used to characterize and improve a specific AM system. PMID:26601039
An Additive Manufacturing Test Artifact.
Moylan, Shawn; Slotwinski, John; Cooke, April; Jurrens, Kevin; Donmez, M Alkan
2014-01-01
A test artifact, intended for standardization, is proposed for the purpose of evaluating the performance of additive manufacturing (AM) systems. A thorough analysis of previously proposed AM test artifacts as well as experience with machining test artifacts have inspired the design of the proposed test artifact. This new artifact is designed to provide a characterization of the capabilities and limitations of an AM system, as well as to allow system improvement by linking specific errors measured in the test artifact to specific sources in the AM system. The proposed test artifact has been built in multiple materials using multiple AM technologies. The results of several of the builds are discussed, demonstrating how the measurement results can be used to characterize and improve a specific AM system.
Attenuation of numerical artefacts in the modelling of fluid interfaces
NASA Astrophysics Data System (ADS)
Evrard, Fabien; van Wachem, Berend G. M.; Denner, Fabian
2015-11-01
Numerical artefacts in the modelling of fluid interfaces, such as parasitic currents or spurious capillary waves, present a considerable problem in two-phase flow modelling. Parasitic currents result from an imperfect evaluation of the interface curvature and can severely affect the flow, whereas spatially underresolved (spurious) capillary waves impose strict limits on the time-step and, hence, dictate the required computational resources for surface-tension-dominated flows. By applying an additional shear stress term at the fluid interface, thereby dissipating the surface energy associated with small wavelengths, we have been able to considerably reduce the adverse impact of parasitic currents and mitigate the time-step limit imposed by capillary waves. However, a careful choice of the applied interface viscosity is crucial, since an excess of additional dissipation compromises the accuracy of the solution. We present the derivation of the additional interfacial shear stress term, explain the underlying physical mechanism and discuss the impact on parasitic currents and interface instabilities based on a variety of numerical experiments. We acknowledge financial support from the Engineering and Physical Sciences Research Council (EPSRC) through Grant No. EP/M021556/1 and from PETROBRAS.
Nitrogen as a friendly addition to steel
Rawers, J.C.
2006-01-01
Interstitial alloying with nitrogen or carbon is a common means of enhancing properties of iron-based alloys. Interstitial nitrogen addition to fcc-phase Fe-Cr-Mn/Ni alloys results in improved mechanical properties, whereas addition of carbon can result in the formation of unwanted carbides. Carbon addition to low alloy, bcc-phase iron alloys significantly improves strength through the formation of carbides, whereas addition of nitrogen in bcc-phase iron alloys can result in porous casting and reduced mechanical properties. This study will show that alloying iron-based alloys with both nitrogen and carbon can produce positive results. Nitrogen addition to Fe-C and Fe-Cr-C alloys, and both nitrogen and nitrogen-carbon additions to Fe-Cr-Mn/Ni alloys altered the microstructure, improved mechanical properties, increased hardness, and reduced wear by stabilizing the fcc-phase and altering (possibly eliminating) precipitate formation.
Numerical experiments in homogeneous turbulence
NASA Technical Reports Server (NTRS)
Rogallo, R. S.
1981-01-01
The direct simulation methods developed by Orszag and Patternson (1972) for isotropic turbulence were extended to homogeneous turbulence in an incompressible fluid subjected to uniform deformation or rotation. The results of simulations for irrotational strain (plane and axisymmetric), shear, rotation, and relaxation toward isotropy following axisymmetric strain are compared with linear theory and experimental data. Emphasis is placed on the shear flow because of its importance and because of the availability of accurate and detailed experimental data. The computed results are used to assess the accuracy of two popular models used in the closure of the Reynolds-stress equations. Data from a variety of the computed fields and the details of the numerical methods used in the simulation are also presented.
Numerical Simulation of Two Phase Flows
NASA Technical Reports Server (NTRS)
Liou, Meng-Sing
2001-01-01
Two phase flows can be found in broad situations in nature, biology, and industry devices and can involve diverse and complex mechanisms. While the physical models may be specific for certain situations, the mathematical formulation and numerical treatment for solving the governing equations can be general. Hence, we will require information concerning each individual phase as needed in a single phase. but also the interactions between them. These interaction terms, however, pose additional numerical challenges because they are beyond the basis that we use to construct modern numerical schemes, namely the hyperbolicity of equations. Moreover, due to disparate differences in time scales, fluid compressibility and nonlinearity become acute, further complicating the numerical procedures. In this paper, we will show the ideas and procedure how the AUSM-family schemes are extended for solving two phase flows problems. Specifically, both phases are assumed in thermodynamic equilibrium, namely, the time scales involved in phase interactions are extremely short in comparison with those in fluid speeds and pressure fluctuations. Details of the numerical formulation and issues involved are discussed and the effectiveness of the method are demonstrated for several industrial examples.
Development of Pelton turbine using numerical simulation
NASA Astrophysics Data System (ADS)
Patel, K.; Patel, B.; Yadav, M.; Foggia, T.
2010-08-01
This paper describes recent research and development activities in the field of Pelton turbine design. Flow inside Pelton turbine is most complex due to multiphase (mixture of air and water) and free surface in nature. Numerical calculation is useful to understand flow physics as well as effect of geometry on flow. The optimized design is obtained using in-house special optimization loop. Either single phase or two phase unsteady numerical calculation could be performed. Numerical results are used to visualize the flow pattern in the water passage and to predict performance of Pelton turbine at full load as well as at part load. Model tests are conducted to determine performance of turbine and it shows good agreement with numerically predicted performance.
Numerical noise in ocean and estuarine models
Walters, R.; Carey, G.F.
1984-01-01
Approximate methods for solving the shallow water equations may lead to solutions exhibiting large fictitious, numerically-induced oscillations. The analysis of the discrete dispersion relation and modal solutions of small wavelengths provides a powerful technique for assessing the sensitivity of alternative numerical schemes to irregular data which may lead to such oscillatory numerical noise. For those schemes where phase speed vanishes at a finite wavenumber or there are multiple roots for wavenumber, oscillation modes can exist which are uncoupled from the dynamics of the problem. The discrete modal analysis approach is used here to identify two classes of spurious oscillation modes associated respectively with the two different asymptotic limits corresponding to estuarine and large scale ocean models. The analysis provides further insight into recent numerical results for models which include large spatial scales and Coriolis acceleration. ?? 1984.
Mathematical modeling and numerical computation of narrow escape problems
NASA Astrophysics Data System (ADS)
Cheviakov, Alexei F.; Reimer, Ashton S.; Ward, Michael J.
2012-02-01
The narrow escape problem refers to the problem of calculating the mean first passage time (MFPT) needed for an average Brownian particle to leave a domain with an insulating boundary containing N small well-separated absorbing windows, or traps. This mean first passage time satisfies the Poisson partial differential equation subject to a mixed Dirichlet-Neumann boundary condition on the domain boundary, with the Dirichlet condition corresponding to absorbing traps. In the limit of small total trap size, a common asymptotic theory is presented to calculate the MFPT in two-dimensional domains and in the unit sphere. The asymptotic MFPT formulas depend on mutual trap locations, allowing for global optimization of trap locations. Although the asymptotic theory for the MFPT was developed in the limit of asymptotically small trap radii, and under the assumption that the traps are well-separated, a comprehensive study involving comparison with full numerical simulations shows that the full numerical and asymptotic results for the MFPT are within 1% accuracy even when total trap size is only moderately small, and for traps that may be rather close together. This close agreement between asymptotic and numerical results at finite, and not necessarily asymptotically small, values of the trap size clearly illustrates one of the key side benefits of a theory based on a systematic asymptotic analysis. In addition, for the unit sphere, numerical results are given for the optimal configuration of a collection of traps on the surface of a sphere that minimizes the average MFPT. The case of N identical traps and a pattern of traps with two different sizes are considered. The effect of trap fragmentation on the average MFPT is also discussed.
Numerical integration of asymptotic solutions of ordinary differential equations
NASA Technical Reports Server (NTRS)
Thurston, Gaylen A.
1989-01-01
Classical asymptotic analysis of ordinary differential equations derives approximate solutions that are numerically stable. However, the analysis also leads to tedious expansions in powers of the relevant parameter for a particular problem. The expansions are replaced with integrals that can be evaluated by numerical integration. The resulting numerical solutions retain the linear independence that is the main advantage of asymptotic solutions. Examples, including the Falkner-Skan equation from laminar boundary layer theory, illustrate the method of asymptotic analysis with numerical integration.
Numerical integration routines for near-earth operations
NASA Technical Reports Server (NTRS)
Powers, W. F.
1973-01-01
Two general purpose numerical integration schemes were built into the NASA-JSC computer system. The state-of-the-art of numerical integration, the particular integrators built into the JSC computer system, and the use of the new integration packages are described. Background information about numerical integration and the variable-order, variable-stepsize Adams numerical integration technique is discussed. Results concerning the PEACE parameter optimization program are given along with recommendations and conclusions.
Personalized numerical observer
NASA Astrophysics Data System (ADS)
Brankov, Jovan G.; Pretorius, P. Hendrik
2010-02-01
It is widely accepted that medical image quality should be assessed using task-based criteria, such as humanobserver (HO) performance in a lesion-detection (scoring) task. HO studies are time consuming and cost prohibitive to be used for image quality assessment during development of either reconstruction methods or imaging systems. Therefore, a numerical observer (NO), a HO surrogate, is highly desirable. In the past, we have proposed and successfully tested a NO based on a supervised-learning approach (namely a support vector machine) for cardiac gated SPECT image quality assessment. In the supervised-learning approach, the goal is to identify the relationship between measured image features and HO myocardium defect likelihood scores. Thus far we have treated multiple HO readers by simply averaging or pooling their respective scores. Due to observer variability, this may be suboptimal and less accurate. Therefore, in this work, we are setting our goal to predict individual observer scores independently in the hope to better capture some relevant lesion-detection mechanism of the human observers. This is even more important as there are many ways to get equivalent observer performance (measured by area under receiver operating curve), and simply predicting some joint (average or pooled) score alone is not likely to succeed.
Numerical Simulation of Chemically Reacting Flows
2015-09-03
interest to the Air Force. 15. SUBJECT TERMS Numerical methods, Diffusion Flames, Adaptive Gridding, Velocity-Vorticity, Compact Methods 16...robust unst tions, and s ’ unstructur acobian, as g in 2012, th ploy a full convergenc ory-efficien potentially grid adapts , he computat...the multiple-scale discretizations are precomputed (each time the grid adapts ) to save CPU time later during residual formation, and that additional
Additive interaction between heterogeneous environmental ...
BACKGROUND Environmental exposures often occur in tandem; however, epidemiological research often focuses on singular exposures. Statistical interactions among broad, well-characterized environmental domains have not yet been evaluated in association with health. We address this gap by conducting a county-level cross-sectional analysis of interactions between Environmental Quality Index (EQI) domain indices on preterm birth in the Unites States from 2000-2005.METHODS: The EQI, a county-level index constructed for the 2000-2005 time period, was constructed from five domain-specific indices (air, water, land, built and sociodemographic) using principal component analyses. County-level preterm birth rates (n=3141) were estimated using live births from the National Center for Health Statistics. Linear regression was used to estimate prevalence differences (PD) and 95% confidence intervals (CI) comparing worse environmental quality to the better quality for each model for a) each individual domain main effect b) the interaction contrast and c) the two main effects plus interaction effect (i.e. the “net effect”) to show departure from additive interaction for the all U.S counties. Analyses were also performed for subgroupings by four urban/rural strata. RESULTS: We found the suggestion of antagonistic interactions but no synergism, along with several purely additive (i.e., no interaction) associations. In the non-stratified model, we observed antagonistic interac
Evolution of solidification texture during additive manufacturing
Wei, H. L.; Mazumder, J.; DebRoy, T.
2015-11-10
Striking differences in the solidification textures of a nickel based alloy owing to changes in laser scanning pattern during additive manufacturing are examined based on theory and experimental data. Understanding and controlling texture are important because it affects mechanical and chemical properties. Solidification texture depends on the local heat flow directions and competitive grain growth in one of the six <100> preferred growth directions in face centered cubic alloys. Furthermore, the heat flow directions are examined for various laser beam scanning patterns based on numerical modeling of heat transfer and fluid flow in three dimensions. Here we show that numericalmore » modeling can not only provide a deeper understanding of the solidification growth patterns during the additive manufacturing, it also serves as a basis for customizing solidification textures which are important for properties and performance of components.« less
Numerical Study of Suspension Plasma Spraying
NASA Astrophysics Data System (ADS)
Farrokhpanah, Amirsaman; Coyle, Thomas W.; Mostaghimi, Javad
2017-01-01
A numerical study of suspension plasma spraying is presented in the current work. The liquid suspension jet is replaced with a train of droplets containing the suspension particles injected into the plasma flow. Atomization, evaporation, and melting of different components are considered for droplets and particles as they travel toward the substrate. Effect of different parameters on particle conditions during flight and upon impact on the substrate is investigated. Initially, influence of the torch operating conditions such as inlet flow rate and power is studied. Additionally, effect of injector parameters like injection location, flow rate, and angle is examined. The model used in the current study takes high-temperature gradients and non-continuum effects into account. Moreover, the important effect of change in physical properties of suspension droplets as a result of evaporation is included in the model. These mainly include variations in heat transfer properties and viscosity. Utilizing this improved model, several test cases have been considered to better evaluate the effect of different parameters on the quality of particles during flight and upon impact on the substrate.
Hybrid Numerical Simulations Of Planetesimal Accretion
NASA Astrophysics Data System (ADS)
Marzari, Francesco; Weidenschilling, S. J.
2006-09-01
The multi-zone simulation code modelling the accretion of planetesimals into planets (Spaute et al. 1991, Icarus 92, 147; Weidenschilling et al. 1997, ICARUS 128, 429) includes a statistical continuum of small bodies in logarithmic mass bins, while large bodies are discrete objects with individual masses and orbits. Formerly, gravitational interactions between large planetary embryos were treated by statistical scattering. The code has now been updated to properly handle the orbits of protoplanets in a deterministic way. The trajectories of the larger bodies are numerically computed with the symplectic integrator SyYMBA. The additional forces acting on the protoplanets due to collisions with smaller planetesimals and their gravitational perturbations, including dynamical friction, as well as gas drag and tidal interaction with the solar nebula, are incorporated in the N-body algorithm by applying a further step in the leap-frog structure of the SyMBA integrator. The changes in the orbital elements of the large bodies, computed in the stochastic part of the code with a Monte Carlo approach, are applied for half a timestep before and after the N-body Hamiltonian propagation as suggested in Lee & Peale (ApJ 567, 596, 2002). With this code we intend to study the effect of dynamical friction on terrestrial planet formation and the accretion of planetary cores in the outer solar system. We will present preliminary results of simulations performed with the updated code.
Numerical Simulation of Supersonic Gap Flow
Jing, Xu; Haiming, Huang; Guo, Huang; Song, Mo
2015-01-01
Various gaps in the surface of the supersonic aircraft have a significant effect on airflows. In order to predict the effects of attack angle, Mach number and width-to-depth ratio of gap on the local aerodynamic heating environment of supersonic flow, two-dimensional compressible Navier-Stokes equations are solved by the finite volume method, where convective flux of space term adopts the Roe format, and discretization of time term is achieved by 5-step Runge-Kutta algorithm. The numerical results reveal that the heat flux ratio is U-shaped distribution on the gap wall and maximum at the windward corner of the gap. The heat flux ratio decreases as the gap depth and Mach number increase, however, it increases as the attack angle increases. In addition, it is important to find that chamfer in the windward corner can effectively reduce gap effect coefficient. The study will be helpful for the design of the thermal protection system in reentry vehicles. PMID:25635395
Numerical dosimetry of transcranial magnetic stimulation coils
NASA Astrophysics Data System (ADS)
Crowther, Lawrence; Hadimani, Ravi; Jiles, David
2014-03-01
Transcranial magnetic stimulation (TMS) is a non-invasive neuromodulation technique capable of stimulating neurons by means of electromagnetic induction. TMS can be used to map brain function and shows promise for the diagnosis and treatment of neurological and psychiatric disorders. Calculation of fields induced in the brain are necessary to accurately identify stimulated neural tissue during TMS. This allows the development of novel TMS coil designs capable of stimulating deeper brain regions and increasing the localization of stimulation that can be achieved. We have performed numerical calculations of magnetic and electric field with high-resolution anatomically realistic human head models to find these stimulated brain regions for a variety of proposed TMS coil designs. The realistic head models contain heterogeneous tissue structures and electrical conductivities, yielding superior results to those obtained from the simplified homogeneous head models that are commonly employed. The attenuation of electric field as a function of depth in the brain and the localization of stimulating field have been methodically investigated. In addition to providing a quantitative comparison of different TMS coil designs the variation of induced field between subjects has been investigated. We also show the differences in induced fields between adult, adolescent and child head models to preemptively identify potential safety issues in the application of pediatric TMS.
Numerical Modeling of Suspension HVOF Spray
NASA Astrophysics Data System (ADS)
Jadidi, M.; Moghtadernejad, S.; Dolatabadi, A.
2016-02-01
A three-dimensional two-way coupled Eulerian-Lagrangian scheme is used to simulate suspension high-velocity oxy-fuel spraying process. The mass, momentum, energy, and species equations are solved together with the realizable k-ɛ turbulence model to simulate the gas phase. Suspension is assumed to be a mixture of solid particles [mullite powder (3Al2O3·2SiO2)], ethanol, and ethylene glycol. The process involves premixed combustion of oxygen-propylene, and non-premixed combustion of oxygen-ethanol and oxygen-ethylene glycol. One-step global reaction is used for each mentioned reaction together with eddy dissipation model to compute the reaction rate. To simulate the droplet breakup, Taylor Analogy Breakup model is applied. After the completion of droplet breakup, and solvent evaporation/combustion, the solid suspended particles are tracked through the domain to determine the characteristics of the coating particles. Numerical simulations are validated against the experimental results in the literature for the same operating conditions. Seven or possibly eight shock diamonds are captured outside the nozzle. In addition, a good agreement between the predicted particle temperature, velocity, and diameter, and the experiment is obtained. It is shown that as the standoff distance increases, the particle temperature and velocity reduce. Furthermore, a correlation is proposed to determine the spray cross-sectional diameter and estimate the particle trajectories as a function of standoff distance.
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