Streamline-curvature effect in three-dimensional boundary layers

NASA Technical Reports Server (NTRS)

Reed, Helen L.; Lin, Ray-Sing; Petraglia, Media M.

1992-01-01

The effect of including wall and streamline curvature terms in swept-wing boundary-layer stability calculations is studied. The linear disturbance equations are cast on a fixed, body-intrinsic, curvilinear coordinate system. Those nonparallel terms which contribute mainly to the streamline-curvature effect are retained in this formulation and approximated by their local finite-difference values. Convex-wall curvature has a stabilizing effect, while streamline curvature is destabilizing if the curvature exceeds a critical value.

Kasei Vallis Streamlined Island

NASA Image and Video Library

2002-12-13

Except for the loss of its ring of ejecta, the crater at the leading edge of this streamlined island in Kasei Vallis, imaged here by NASA Mars Odyssey, shows no hint of the catastrophic floods that passed by it. Kasei Vallis is one of several major outflow channel systems that were active over 3 billion years ago. The intense floods scoured the landscape, eroding craters and producing streamlined islands. But in a close-up view, the evidence for these floods is not apparent. This true of the most similar terrestrial example, the channeled scablands of eastern Washington which also were formed by a catastrophic flood. http://photojournal.jpl.nasa.gov/catalog/PIA04022

Investigation of smoothness-increasing accuracy-conserving filters for improving streamline integration through discontinuous fields.

PubMed

Steffen, Michael; Curtis, Sean; Kirby, Robert M; Ryan, Jennifer K

2008-01-01

Streamline integration of fields produced by computational fluid mechanics simulations is a commonly used tool for the investigation and analysis of fluid flow phenomena. Integration is often accomplished through the application of ordinary differential equation (ODE) integrators--integrators whose error characteristics are predicated on the smoothness of the field through which the streamline is being integrated--smoothness which is not available at the inter-element level of finite volume and finite element data. Adaptive error control techniques are often used to ameliorate the challenge posed by inter-element discontinuities. As the root of the difficulties is the discontinuous nature of the data, we present a complementary approach of applying smoothness-enhancing accuracy-conserving filters to the data prior to streamline integration. We investigate whether such an approach applied to uniform quadrilateral discontinuous Galerkin (high-order finite volume) data can be used to augment current adaptive error control approaches. We discuss and demonstrate through numerical example the computational trade-offs exhibited when one applies such a strategy.

Implications of streamlining theory for microbial ecology

PubMed Central

Giovannoni, Stephen J; Cameron Thrash, J; Temperton, Ben

2014-01-01

Whether a small cell, a small genome or a minimal set of chemical reactions with self-replicating properties, simplicity is beguiling. As Leonardo da Vinci reportedly said, ‘simplicity is the ultimate sophistication'. Two diverging views of simplicity have emerged in accounts of symbiotic and commensal bacteria and cosmopolitan free-living bacteria with small genomes. The small genomes of obligate insect endosymbionts have been attributed to genetic drift caused by small effective population sizes (Ne). In contrast, streamlining theory attributes small cells and genomes to selection for efficient use of nutrients in populations where Ne is large and nutrients limit growth. Regardless of the cause of genome reduction, lost coding potential eventually dictates loss of function. Consequences of reductive evolution in streamlined organisms include atypical patterns of prototrophy and the absence of common regulatory systems, which have been linked to difficulty in culturing these cells. Recent evidence from metagenomics suggests that streamlining is commonplace, may broadly explain the phenomenon of the uncultured microbial majority, and might also explain the highly interdependent (connected) behavior of many microbial ecosystems. Streamlining theory is belied by the observation that many successful bacteria are large cells with complex genomes. To fully appreciate streamlining, we must look to the life histories and adaptive strategies of cells, which impose minimum requirements for complexity that vary with niche. PMID:24739623

Probabilistic Simulation of Multi-Scale Composite Behavior

NASA Technical Reports Server (NTRS)

Chamis, Christos C.

2012-01-01

A methodology is developed to computationally assess the non-deterministic composite response at all composite scales (from micro to structural) due to the uncertainties in the constituent (fiber and matrix) properties, in the fabrication process and in structural variables (primitive variables). The methodology is computationally efficient for simulating the probability distributions of composite behavior, such as material properties, laminate and structural responses. Bi-products of the methodology are probabilistic sensitivities of the composite primitive variables. The methodology has been implemented into the computer codes PICAN (Probabilistic Integrated Composite ANalyzer) and IPACS (Integrated Probabilistic Assessment of Composite Structures). The accuracy and efficiency of this methodology are demonstrated by simulating the uncertainties in composite typical laminates and comparing the results with the Monte Carlo simulation method. Available experimental data of composite laminate behavior at all scales fall within the scatters predicted by PICAN. Multi-scaling is extended to simulate probabilistic thermo-mechanical fatigue and to simulate the probabilistic design of a composite redome in order to illustrate its versatility. Results show that probabilistic fatigue can be simulated for different temperature amplitudes and for different cyclic stress magnitudes. Results also show that laminate configurations can be selected to increase the redome reliability by several orders of magnitude without increasing the laminate thickness--a unique feature of structural composites. The old reference denotes that nothing fundamental has been done since that time.

Fiber Composite Sandwich Thermostructural Behavior: Computational Simulation

NASA Technical Reports Server (NTRS)

Chamis, C. C.; Aiello, R. A.; Murthy, P. L. N.

1986-01-01

Several computational levels of progressive sophistication/simplification are described to computationally simulate composite sandwich hygral, thermal, and structural behavior. The computational levels of sophistication include: (1) three-dimensional detailed finite element modeling of the honeycomb, the adhesive and the composite faces; (2) three-dimensional finite element modeling of the honeycomb assumed to be an equivalent continuous, homogeneous medium, the adhesive and the composite faces; (3) laminate theory simulation where the honeycomb (metal or composite) is assumed to consist of plies with equivalent properties; and (4) derivations of approximate, simplified equations for thermal and mechanical properties by simulating the honeycomb as an equivalent homogeneous medium. The approximate equations are combined with composite hygrothermomechanical and laminate theories to provide a simple and effective computational procedure for simulating the thermomechanical/thermostructural behavior of fiber composite sandwich structures.

Enhanced Performance of Streamline-Traced External-Compression Supersonic Inlets

NASA Technical Reports Server (NTRS)

Slater, John W.

2015-01-01

A computational design study was conducted to enhance the aerodynamic performance of streamline-traced, external-compression inlets for Mach 1.6. Compared to traditional external-compression, two-dimensional and axisymmetric inlets, streamline-traced inlets promise reduced cowl wave drag and sonic boom, but at the expense of reduced total pressure recovery and increased total pressure distortion. The current study explored a new parent flowfield for the streamline tracing and several variations of inlet design factors, including the axial displacement and angle of the subsonic cowl lip, the vertical placement of the engine axis, and the use of porous bleed in the subsonic diffuser. The performance was enhanced over that of an earlier streamline-traced inlet such as to increase the total pressure recovery and reduce total pressure distortion.

Enhanced Performance of Streamline-Traced External-Compression Supersonic Inlets

NASA Technical Reports Server (NTRS)

Slater, John W.

2015-01-01

A computational design study was conducted to enhance the aerodynamic performance of streamline-traced, external-compression inlets for Mach 1.6. The current study explored a new parent flowfield for the streamline tracing and several variations of inlet design factors, including the axial displacement and angle of the subsonic cowl lip, the vertical placement of the engine axis, and the use of porous bleed in the subsonic diffuser. The performance was enhanced over that of an earlier streamline-traced inlet such as to increase the total pressure recovery and reduce total pressure distortion

Animating streamlines with repeated asymmetric patterns for steady flow visualization

NASA Astrophysics Data System (ADS)

Yeh, Chih-Kuo; Liu, Zhanping; Lee, Tong-Yee

2012-01-01

Animation provides intuitive cueing for revealing essential spatial-temporal features of data in scientific visualization. This paper explores the design of Repeated Asymmetric Patterns (RAPs) in animating evenly-spaced color-mapped streamlines for dense accurate visualization of complex steady flows. We present a smooth cyclic variable-speed RAP animation model that performs velocity (magnitude) integral luminance transition on streamlines. This model is extended with inter-streamline synchronization in luminance varying along the tangential direction to emulate orthogonal advancing waves from a geometry-based flow representation, and then with evenly-spaced hue differing in the orthogonal direction to construct tangential flow streaks. To weave these two mutually dual sets of patterns, we propose an energy-decreasing strategy that adopts an iterative yet efficient procedure for determining the luminance phase and hue of each streamline in HSL color space. We also employ adaptive luminance interleaving in the direction perpendicular to the flow to increase the contrast between streamlines.

The impact of groundwater velocity fields on streamlines in an aquifer system with a discontinuous aquitard (Inner Mongolia, China)

NASA Astrophysics Data System (ADS)

Wu, Qiang; Zhao, Yingwang; Xu, Hua

2018-04-01

Many numerical methods that simulate groundwater flow, particularly the continuous Galerkin finite element method, do not produce velocity information directly. Many algorithms have been proposed to improve the accuracy of velocity fields computed from hydraulic potentials. The differences in the streamlines generated from velocity fields obtained using different algorithms are presented in this report. The superconvergence method employed by FEFLOW, a popular commercial code, and some dual-mesh methods proposed in recent years are selected for comparison. The applications to depict hydrogeologic conditions using streamlines are used, and errors in streamlines are shown to lead to notable errors in boundary conditions, the locations of material interfaces, fluxes and conductivities. Furthermore, the effects of the procedures used in these two types of methods, including velocity integration and local conservation, are analyzed. The method of interpolating velocities across edges using fluxes is shown to be able to eliminate errors associated with refraction points that are not located along material interfaces and streamline ends at no-flow boundaries. Local conservation is shown to be a crucial property of velocity fields and can result in more accurate streamline densities. A case study involving both three-dimensional and two-dimensional cross-sectional models of a coal mine in Inner Mongolia, China, are used to support the conclusions presented.

Creating customer value by streamlining business processes.

PubMed

Vantrappen, H

1992-02-01

Much of the strategic preoccupation of senior managers in the 1990s is focusing on the creation of customer value. Companies are seeking competitive advantage by streamlining the three processes through which they interact with their customers: product creation, order handling and service assurance. 'Micro-strategy' is a term which has been coined for the trade-offs and decisions on where and how to streamline these three processes. The article discusses micro-strategies applied by successful companies.

Air Permitting Streamlining Techniques and Approaches for Greenhouse Gases, 2012

EPA Pesticide Factsheets

This report presents potential GHG permit streamlining options and observations developed by the Clean Air Act Advisory Committee (CAAAC): Permits, New Source Review and Toxics Subcommittee GHG Permit Streamlining Workgroup

Simulations of carbon fiber composite delamination tests

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kay, G

2007-10-25

Simulations of mode I interlaminar fracture toughness tests of a carbon-reinforced composite material (BMS 8-212) were conducted with LSDYNA. The fracture toughness tests were performed by U.C. Berkeley. The simulations were performed to investigate the validity and practicality of employing decohesive elements to represent interlaminar bond failures that are prevalent in carbon-fiber composite structure penetration events. The simulations employed a decohesive element formulation that was verified on a simple two element model before being employed to perform the full model simulations. Care was required during the simulations to ensure that the explicit time integration of LSDYNA duplicate the near steady-statemore » testing conditions. In general, this study validated the use of employing decohesive elements to represent the interlaminar bond failures seen in carbon-fiber composite structures, but the practicality of employing the elements to represent the bond failures seen in carbon-fiber composite structures during penetration events was not established.« less

ACHP | News | Nationwide Programmatic Agreement Streamlines 106 Process for

Science.gov Websites

Publications Search skip specific nav links Home arrow News arrow Nationwide Programmatic Agreement Streamlines 106 Process for NPS Nationwide Programmatic Agreement Streamlines 106 Process for NPS Pursuant to Service (NPS) on November 14, 2008, executed a nationwide Programmatic Agreement (PA) with the Advisory

A streamlined failure mode and effects analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ford, Eric C., E-mail: eford@uw.edu; Smith, Koren; Terezakis, Stephanie

Purpose: Explore the feasibility and impact of a streamlined failure mode and effects analysis (FMEA) using a structured process that is designed to minimize staff effort. Methods: FMEA for the external beam process was conducted at an affiliate radiation oncology center that treats approximately 60 patients per day. A structured FMEA process was developed which included clearly defined roles and goals for each phase. A core group of seven people was identified and a facilitator was chosen to lead the effort. Failure modes were identified and scored according to the FMEA formalism. A risk priority number,RPN, was calculated and usedmore » to rank failure modes. Failure modes with RPN > 150 received safety improvement interventions. Staff effort was carefully tracked throughout the project. Results: Fifty-two failure modes were identified, 22 collected during meetings, and 30 from take-home worksheets. The four top-ranked failure modes were: delay in film check, missing pacemaker protocol/consent, critical structures not contoured, and pregnant patient simulated without the team's knowledge of the pregnancy. These four failure modes hadRPN > 150 and received safety interventions. The FMEA was completed in one month in four 1-h meetings. A total of 55 staff hours were required and, additionally, 20 h by the facilitator. Conclusions: Streamlined FMEA provides a means of accomplishing a relatively large-scale analysis with modest effort. One potential value of FMEA is that it potentially provides a means of measuring the impact of quality improvement efforts through a reduction in risk scores. Future study of this possibility is needed.« less

A streamlined failure mode and effects analysis.

PubMed

Ford, Eric C; Smith, Koren; Terezakis, Stephanie; Croog, Victoria; Gollamudi, Smitha; Gage, Irene; Keck, Jordie; DeWeese, Theodore; Sibley, Greg

2014-06-01

Explore the feasibility and impact of a streamlined failure mode and effects analysis (FMEA) using a structured process that is designed to minimize staff effort. FMEA for the external beam process was conducted at an affiliate radiation oncology center that treats approximately 60 patients per day. A structured FMEA process was developed which included clearly defined roles and goals for each phase. A core group of seven people was identified and a facilitator was chosen to lead the effort. Failure modes were identified and scored according to the FMEA formalism. A risk priority number,RPN, was calculated and used to rank failure modes. Failure modes with RPN > 150 received safety improvement interventions. Staff effort was carefully tracked throughout the project. Fifty-two failure modes were identified, 22 collected during meetings, and 30 from take-home worksheets. The four top-ranked failure modes were: delay in film check, missing pacemaker protocol/consent, critical structures not contoured, and pregnant patient simulated without the team's knowledge of the pregnancy. These four failure modes had RPN > 150 and received safety interventions. The FMEA was completed in one month in four 1-h meetings. A total of 55 staff hours were required and, additionally, 20 h by the facilitator. Streamlined FMEA provides a means of accomplishing a relatively large-scale analysis with modest effort. One potential value of FMEA is that it potentially provides a means of measuring the impact of quality improvement efforts through a reduction in risk scores. Future study of this possibility is needed.

Hierarchical Simulation of Hot Composite Structures

NASA Technical Reports Server (NTRS)

Chamis, C. C.; Murthy, P. L. N.; Singhal, S. N.

1993-01-01

Computational procedures are described to simulate the thermal and mechanical behavior of high temperature metal matrix composites (HT-MMC) in the following three broad areas: (1) Behavior of HT-MMC's from micromechanics to laminate via Metal Matrix Composite Analyzer (METCAN), (2) tailoring of HT-MMC behavior for optimum specific performance via Metal Matrix Laminate Tailoring (MMLT), and (3) HT-MMC structural response for hot structural components via High Temperature Composite Analyzer (HITCAN). Representative results from each area are presented to illustrate the effectiveness of computational simulation procedures. The sample case results show that METCAN can be used to simulate material behavior such as strength, stress-strain response, and cyclic life in HTMMC's; MMLT can be used to tailor the fabrication process for optimum performance such as that for in-service load carrying capacity of HT-MMC's; and HITCAN can be used to evaluate static fracture and fatigue life of hot pressurized metal matrix composite rings.

Probabilistic simulation of multi-scale composite behavior

NASA Technical Reports Server (NTRS)

Liaw, D. G.; Shiao, M. C.; Singhal, S. N.; Chamis, Christos C.

1993-01-01

A methodology is developed to computationally assess the probabilistic composite material properties at all composite scale levels due to the uncertainties in the constituent (fiber and matrix) properties and in the fabrication process variables. The methodology is computationally efficient for simulating the probability distributions of material properties. The sensitivity of the probabilistic composite material property to each random variable is determined. This information can be used to reduce undesirable uncertainties in material properties at the macro scale of the composite by reducing the uncertainties in the most influential random variables at the micro scale. This methodology was implemented into the computer code PICAN (Probabilistic Integrated Composite ANalyzer). The accuracy and efficiency of this methodology are demonstrated by simulating the uncertainties in the material properties of a typical laminate and comparing the results with the Monte Carlo simulation method. The experimental data of composite material properties at all scales fall within the scatters predicted by PICAN.

Structural Composites Corrosive Management by Computational Simulation

NASA Technical Reports Server (NTRS)

Chamis, Christos C.; Minnetyan, Levon

2006-01-01

A simulation of corrosive management on polymer composites durability is presented. The corrosive environment is assumed to manage the polymer composite degradation on a ply-by-ply basis. The degradation is correlated with a measured Ph factor and is represented by voids, temperature, and moisture which vary parabolically for voids and linearly for temperature and moisture through the laminate thickness. The simulation is performed by a computational composite mechanics computer code which includes micro, macro, combined stress failure, and laminate theories. This accounts for starting the simulation from constitutive material properties and up to the laminate scale which exposes the laminate to the corrosive environment. Results obtained for one laminate indicate that the ply-by-ply managed degradation degrades the laminate to the last one or the last several plies. Results also demonstrate that the simulation is applicable to other polymer composite systems as well.

Polymer Composites Corrosive Degradation: A Computational Simulation

NASA Technical Reports Server (NTRS)

Chamis, Christos C.; Minnetyan, Levon

2007-01-01

A computational simulation of polymer composites corrosive durability is presented. The corrosive environment is assumed to manage the polymer composite degradation on a ply-by-ply basis. The degradation is correlated with a measured pH factor and is represented by voids, temperature and moisture which vary parabolically for voids and linearly for temperature and moisture through the laminate thickness. The simulation is performed by a computational composite mechanics computer code which includes micro, macro, combined stress failure and laminate theories. This accounts for starting the simulation from constitutive material properties and up to the laminate scale which exposes the laminate to the corrosive environment. Results obtained for one laminate indicate that the ply-by-ply degradation degrades the laminate to the last one or the last several plies. Results also demonstrate that the simulation is applicable to other polymer composite systems as well.

LOADING SIMULATION PROGRAM C

EPA Pesticide Factsheets

LSPC is the Loading Simulation Program in C++, a watershed modeling system that includes streamlined Hydrologic Simulation Program Fortran (HSPF) algorithms for simulating hydrology, sediment, and general water quality

Process simulations for manufacturing of thick composites

NASA Astrophysics Data System (ADS)

Kempner, Evan A.

The availability of manufacturing simulations for composites can significantly reduce the costs associated with process development. Simulations provide a tool for evaluating the effect of processing conditions on the quality of parts produced without requiring numerous experiments. This is especially significant in parts that have troublesome features such as large thickness. The development of simulations for thick walled composites has been approached by examining the mechanics of resin flow and fiber deformation during processing, applying these evaluations to develop simulations, and evaluating the simulation with experimental results. A unified analysis is developed to describe the three-dimensional resin flow and fiber preform deformation during processing regardless of the manufacturing process used. It is shown how the generic governing evaluations in the unified analysis can be applied to autoclave molding, compression molding, pultrusion, filament winding, and resin transfer molding. A comparison is provided with earlier models derived individually for these processes. The evaluations described for autoclave curing were used to produce a one-dimensional cure simulation for autoclave curing of thick composites. The simulation consists of an analysis for heat transfer and resin flow in the composite as well as bleeder plies used to absorb resin removed from the part. Experiments were performed in a hot press to approximate curing in an autoclave. Graphite/epoxy laminates of 3 cm and 5 cm thickness were cured while monitoring temperatures at several points inside the laminate and thickness. The simulation predicted temperatures fairly closely, but difficulties were encountered in correlation of thickness results. This simulation was also used to study the effects of prepreg aging on processing of thick composites. An investigation was also performed on filament winding with prepreg tow. Cylinders were wound of approximately 12 mm thickness with pressure

Harmonization of experimental approach and data collection to streamline analysis of biomass composition from algae in an inter-laboratory setting

DOE Office of Scientific and Technical Information (OSTI.GOV)

Laurens, Lieve M. L.; Van Wychen, Stefanie; Pienkos, Philip T.

In order to establish and design long-term algae cultivation experiments, inter-laboratory projects need to harmonize the requirements of techno-economic and life-cycle analysis models, with standardized data inputs. In order to provide a consistent foundation and allow for integration and analysis of the results in computational technical and resource analysis models, we implemented closely coordinated, harmonized and objective analytical protocols along with a common language for measuring growth and productivity for the major algal components. We describe here the process by which we developed a harmonization framework for analysis across five geographically diverse testbed sites. Our goal was to align analyticalmore » procedures to ensure consistent reporting on biomass and lipid content, quality and yields to eliminate measurement variability as a source of uncertainty in production data. Developing standards for analysis that streamline reporting on composition and expected fuel yields from biomass is one of the major outcomes of this work and this provides a starting place for further advanced characterization of algae to support the techno-economical process analyses and account for the mass balance accounting of algal biomass. In conclusion, initial analysis of data obtained from field studies shows trends in compositional shifts of lipid and protein content of the biomass that are in support of the physiological experiments demonstrated in the first geographically distributed unified outdoor cultivation trials.« less

Harmonization of experimental approach and data collection to streamline analysis of biomass composition from algae in an inter-laboratory setting

DOE PAGES

Laurens, Lieve M. L.; Van Wychen, Stefanie; Pienkos, Philip T.; ...

2017-04-26

In order to establish and design long-term algae cultivation experiments, inter-laboratory projects need to harmonize the requirements of techno-economic and life-cycle analysis models, with standardized data inputs. In order to provide a consistent foundation and allow for integration and analysis of the results in computational technical and resource analysis models, we implemented closely coordinated, harmonized and objective analytical protocols along with a common language for measuring growth and productivity for the major algal components. We describe here the process by which we developed a harmonization framework for analysis across five geographically diverse testbed sites. Our goal was to align analyticalmore » procedures to ensure consistent reporting on biomass and lipid content, quality and yields to eliminate measurement variability as a source of uncertainty in production data. Developing standards for analysis that streamline reporting on composition and expected fuel yields from biomass is one of the major outcomes of this work and this provides a starting place for further advanced characterization of algae to support the techno-economical process analyses and account for the mass balance accounting of algal biomass. In conclusion, initial analysis of data obtained from field studies shows trends in compositional shifts of lipid and protein content of the biomass that are in support of the physiological experiments demonstrated in the first geographically distributed unified outdoor cultivation trials.« less

Computational simulation of progressive fracture in fiber composites

NASA Technical Reports Server (NTRS)

Chamis, C. C.

1986-01-01

Computational methods for simulating and predicting progressive fracture in fiber composite structures are presented. These methods are integrated into a computer code of modular form. The modules include composite mechanics, finite element analysis, and fracture criteria. The code is used to computationally simulate progressive fracture in composite laminates with and without defects. The simulation tracks the fracture progression in terms of modes initiating fracture, damage growth, and imminent global (catastrophic) laminate fracture.

Streamlining genomes: toward the generation of simplified and stabilized microbial systems.

PubMed

Leprince, Audrey; van Passel, Mark W J; dos Santos, Vitor A P Martins

2012-10-01

At the junction between systems and synthetic biology, genome streamlining provides a solid foundation both for increased understanding of cellular circuitry, and for the tailoring of microbial chassis towards innovative biotechnological applications. Iterative genomic deletions (targeted and random) helps to generate simplified, stabilized and predictable genomes, whereas multiplexing genome engineering reveals a broad functional genetic diversity. The decrease in oligo and gene synthesis costs promises effective combinatorial tools for the generation of chassis based on streamlined and tractable genomes. Here we review recent progresses in streamlining genomes through recombineering techniques aiming to generate insights into cellular mechanisms and responses towards the design and assembly of streamlined genome chassis together with new cellular modules in diverse biotechnological applications. Copyright © 2012 Elsevier Ltd. All rights reserved.

Probabilistic simulation of stress concentration in composite laminates

NASA Technical Reports Server (NTRS)

Chamis, C. C.; Murthy, P. L. N.; Liaw, L.

1993-01-01

A computational methodology is described to probabilistically simulate the stress concentration factors in composite laminates. This new approach consists of coupling probabilistic composite mechanics with probabilistic finite element structural analysis. The probabilistic composite mechanics is used to probabilistically describe all the uncertainties inherent in composite material properties while probabilistic finite element is used to probabilistically describe the uncertainties associated with methods to experimentally evaluate stress concentration factors such as loads, geometry, and supports. The effectiveness of the methodology is demonstrated by using it to simulate the stress concentration factors in composite laminates made from three different composite systems. Simulated results match experimental data for probability density and for cumulative distribution functions. The sensitivity factors indicate that the stress concentration factors are influenced by local stiffness variables, by load eccentricities and by initial stress fields.

Probabilistic Simulation of Stress Concentration in Composite Laminates

NASA Technical Reports Server (NTRS)

Chamis, C. C.; Murthy, P. L. N.; Liaw, D. G.

1994-01-01

A computational methodology is described to probabilistically simulate the stress concentration factors (SCF's) in composite laminates. This new approach consists of coupling probabilistic composite mechanics with probabilistic finite element structural analysis. The composite mechanics is used to probabilistically describe all the uncertainties inherent in composite material properties, whereas the finite element is used to probabilistically describe the uncertainties associated with methods to experimentally evaluate SCF's, such as loads, geometry, and supports. The effectiveness of the methodology is demonstrated by using is to simulate the SCF's in three different composite laminates. Simulated results match experimental data for probability density and for cumulative distribution functions. The sensitivity factors indicate that the SCF's are influenced by local stiffness variables, by load eccentricities, and by initial stress fields.

The self streamlining wind tunnel. [wind tunnel walls

NASA Technical Reports Server (NTRS)

Goodyer, M. J.

1975-01-01

A two dimensional test section in a low speed wind tunnel capable of producing flow conditions free from wall interference is presented. Flexible top and bottom walls, and rigid sidewalls from which models were mounted spanning the tunnel are shown. All walls were unperforated, and the flexible walls were positioned by screw jacks. To eliminate wall interference, the wind tunnel itself supplied the information required in the streamlining process, when run with the model present. Measurements taken at the flexible walls were used by the tunnels computer check wall contours. Suitable adjustments based on streamlining criteria were then suggested by the computer. The streamlining criterion adopted when generating infinite flowfield conditions was a matching of static pressures in the test section at a wall with pressures computed for an imaginary inviscid flowfield passing over the outside of the same wall. Aerodynamic data taken on a cylindrical model operating under high blockage conditions are presented to illustrate the operation of the tunnel in its various modes.

A case study of development and application of a streamlined control and response modeling system for PM2.5 attainment assessment in China.

PubMed

Long, Shicheng; Zhu, Yun; Jang, Carey; Lin, Che-Jen; Wang, Shuxiao; Zhao, Bin; Gao, Jian; Deng, Shuang; Xie, Junping; Qiu, Xuezhen

2016-03-01

This article describes the development and application of a streamlined air control and response modeling system with a novel response surface modeling-linear coupled fitting method and a new module to provide streamlined model data for PM2.5 attainment assessment in China. This method is capable of significantly reducing the dimensions required to establish a response surface model, as well as capturing more realistic response of PM2.5 to emission changes with a limited number of model simulations. The newly developed module establishes a data link between the system and the Software for Model Attainment Test-Community Edition (SMAT-CE), and has the ability to rapidly provide model responses to emission control scenarios for SMAT-CE using a simple interface. The performance of this streamlined system is demonstrated through a case study of the Yangtze River Delta (YRD) in China. Our results show that this system is capable of reproducing the Community Multi-Scale Air Quality (CMAQ) model simulation results with maximum mean normalized error<3.5%. It is also demonstrated that primary emissions make a major contribution to ambient levels of PM2.5 in January and August (e.g., more than 50% contributed by primary emissions in Shanghai), and Shanghai needs to have regional emission control both locally and in its neighboring provinces to meet China's annual PM2.5 National Ambient Air Quality Standard. The streamlined system provides a real-time control/response assessment to identify the contributions of major emission sources to ambient PM2.5 (and potentially O3 as well) and streamline air quality data for SMAT-CE to perform attainment assessments. Copyright © 2015. Published by Elsevier B.V.

Streamlined Livestock Trailer

NASA Technical Reports Server (NTRS)

1980-01-01

Bull Nose livestock trailer, manufactured by American Trailer, Inc. is one of a line of highway transport vehicles manufactured by American Trailers, Inc. The slant side front end is a streamlining feature based on a NASA Research Program which investigated the aerodynamic characteristics of trailer/tractor combinations and suggested ways of reducing air resistance. Application of NASA's aerodynamic research technology to the bull nose design resulted in a 10 percent reduction in air drag, which translates into annual fuel savings of several hundred dollars.

Simulating Microfracture In Metal-Matrix Composites

NASA Technical Reports Server (NTRS)

Mital, Subodh K.; Chamis, Christos C.; Gotsis, Pascal K.

1994-01-01

Computational procedures developed for simulating microfracture in metal-matrix/fiber composite materials under mechanical and/or thermal loads at ambient and high temperatures. Procedures evaluate microfracture behavior of composites, establish hierarchies and sequences of fracture modes, and examine influences of compliant layers and partial debonding on properties of composites and on initiation of microfractures in them.

Surface-Streamline Flow Visualization

NASA Technical Reports Server (NTRS)

Langston, L.; Boyle, M.

1985-01-01

Matrix of ink dots covers matte surface of polyester drafting film. Film placed against wind-tunnel wall. Layer of methyl salicylate (oil of wintergreen) sprayed over dotted area. Ink dot streaklines show several characteristics of flow, including primary saddle point of separations, primary horseshoe vortex and smaller vortex at cylinder/ endwall junction. Surface streamline flow visualization technique suitable for use in low-speed windtunnels or other low-speed gas flows.

On a modified streamline curvature method for the Euler equations

NASA Technical Reports Server (NTRS)

Cordova, Jeffrey Q.; Pearson, Carl E.

1988-01-01

A modification of the streamline curvature method leads to a quasilinear second-order partial differential equation for the streamline coordinate function. The existence of a stream function is not required. The method is applied to subsonic and supersonic nozzle flow, and to axially symmetric flow with swirl. For many situations, the associated numerical method is both fast and accurate.

Clustered streamlined forms in Athabasca Valles, Mars: Evidence for sediment deposition during floodwater ponding

USGS Publications Warehouse

Burr, D.

2005-01-01

A unique clustering of layered streamlined forms in Athabasca Valles is hypothesized to reflect a significant hydraulic event. The forms, interpreted as sedimentary, are attributed to extensive sediment deposition during ponding and then streamlining of this sediment behind flow obstacles during ponded water outflow. These streamlined forms are analogous to those found in depositional basins and other loci of ponding in terrestrial catastrophic flood landscapes. These terrestrial streamlined forms can provide the best opportunity for reconstructing the history of the terrestrial flooding. Likewise, the streamlined forms in Athabasca Valles may provide the best opportunity to reconstruct the recent geologic history of this young Martian outflow channel. ?? 2005 Elsevier B.V. All rights reserved.

Simulated Data for High Temperature Composite Design

NASA Technical Reports Server (NTRS)

Chamis, Christos C.; Abumeri, Galib H.

2006-01-01

The paper describes an effective formal method that can be used to simulate design properties for composites that is inclusive of all the effects that influence those properties. This effective simulation method is integrated computer codes that include composite micromechanics, composite macromechanics, laminate theory, structural analysis, and multi-factor interaction model. Demonstration of the method includes sample examples for static, thermal, and fracture reliability for a unidirectional metal matrix composite as well as rupture strength and fatigue strength for a high temperature super alloy. Typical results obtained for a unidirectional composite show that the thermal properties are more sensitive to internal local damage, the longitudinal properties degrade slowly with temperature, the transverse and shear properties degrade rapidly with temperature as do rupture strength and fatigue strength for super alloys.

STREAMLINED LIFE CYCLE ASSESSMENT: A FINAL REPORT FROM THE SETAC-NORTH AMERICA STREAMLINED LCA WORKGROUP

EPA Science Inventory

The original goal of the Streamlined LCA workgroup was to define and document a process for a shortened form of LCA. At the time, because of the large amount of data needed to do a cradle-to-grave evaluation, it was believed that in addition to such a "full" LCA approach there w...

Streamlined Island

NASA Technical Reports Server (NTRS)

2003-01-01

MGS MOC Release No. MOC2-514, 15 October 2003

This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) picture shows a streamlined island in Marte Vallis, a large outflow channel system that crosses the 180oW meridian between the Elysium and Amazonis regions of Mars. The flow patterns on the floor of Marte Vallis might be the remains of lava flows or mud flows. Marte is the Spanish word for Mars. Most of the largest valleys on the red planet are named for 'Mars' in various languages. This island is located near 21.8oN, 175.3oW. The picture covers an area 3 km (1.9 mi) wide and is illuminated by sunlight from the lower left.

Computational Simulation of Composite Structural Fatigue

NASA Technical Reports Server (NTRS)

Minnetyan, Levon; Chamis, Christos C. (Technical Monitor)

2005-01-01

Progressive damage and fracture of composite structures subjected to monotonically increasing static, tension-tension cyclic, pressurization, and flexural cyclic loading are evaluated via computational simulation. Constituent material properties, stress and strain limits are scaled up to the structure level to evaluate the overall damage and fracture propagation for composites. Damage initiation, growth, accumulation, and propagation to fracture due to monotonically increasing static and cyclic loads are included in the simulations. Results show the number of cycles to failure at different temperatures and the damage progression sequence during different degradation stages. A procedure is outlined for use of computational simulation data in the assessment of damage tolerance, determination of sensitive parameters affecting fracture, and interpretation of results with insight for design decisions.

Computational Simulation of Composite Structural Fatigue

NASA Technical Reports Server (NTRS)

Minnetyan, Levon

2004-01-01

Progressive damage and fracture of composite structures subjected to monotonically increasing static, tension-tension cyclic, pressurization, and flexural cyclic loading are evaluated via computational simulation. Constituent material properties, stress and strain limits are scaled up to the structure level to evaluate the overall damage and fracture propagation for composites. Damage initiation, growth, accumulation, and propagation to fracture due to monotonically increasing static and cyclic loads are included in the simulations. Results show the number of cycles to failure at different temperatures and the damage progression sequence during different degradation stages. A procedure is outlined for use of computational simulation data in the assessment of damage tolerance, determination of sensitive parameters affecting fracture, and interpretation of results with insight for design decisions.

Probabilistic simulation of uncertainties in composite uniaxial strengths

NASA Technical Reports Server (NTRS)

Chamis, C. C.; Stock, T. A.

1990-01-01

Probabilistic composite micromechanics methods are developed that simulate uncertainties in unidirectional fiber composite strengths. These methods are in the form of computational procedures using composite mechanics with Monte Carlo simulation. The variables for which uncertainties are accounted include constituent strengths and their respective scatter. A graphite/epoxy unidirectional composite (ply) is studied to illustrate the procedure and its effectiveness to formally estimate the probable scatter in the composite uniaxial strengths. The results show that ply longitudinal tensile and compressive, transverse compressive and intralaminar shear strengths are not sensitive to single fiber anomalies (breaks, intergacial disbonds, matrix microcracks); however, the ply transverse tensile strength is.

Out-of-Core Streamline Visualization on Large Unstructured Meshes

NASA Technical Reports Server (NTRS)

Ueng, Shyh-Kuang; Sikorski, K.; Ma, Kwan-Liu

1997-01-01

It's advantageous for computational scientists to have the capability to perform interactive visualization on their desktop workstations. For data on large unstructured meshes, this capability is not generally available. In particular, particle tracing on unstructured grids can result in a high percentage of non-contiguous memory accesses and therefore may perform very poorly with virtual memory paging schemes. The alternative of visualizing a lower resolution of the data degrades the original high-resolution calculations. This paper presents an out-of-core approach for interactive streamline construction on large unstructured tetrahedral meshes containing millions of elements. The out-of-core algorithm uses an octree to partition and restructure the raw data into subsets stored into disk files for fast data retrieval. A memory management policy tailored to the streamline calculations is used such that during the streamline construction only a very small amount of data are brought into the main memory on demand. By carefully scheduling computation and data fetching, the overhead of reading data from the disk is significantly reduced and good memory performance results. This out-of-core algorithm makes possible interactive streamline visualization of large unstructured-grid data sets on a single mid-range workstation with relatively low main-memory capacity: 5-20 megabytes. Our test results also show that this approach is much more efficient than relying on virtual memory and operating system's paging algorithms.

Ultrasonic NDE Simulation for Composite Manufacturing Defects

NASA Technical Reports Server (NTRS)

Leckey, Cara A. C.; Juarez, Peter D.

2016-01-01

The increased use of composites in aerospace components is expected to continue into the future. The large scale use of composites in aerospace necessitates the development of composite-appropriate nondestructive evaluation (NDE) methods to quantitatively characterize defects in as-manufactured parts and damage incurred during or post manufacturing. Ultrasonic techniques are one of the most common approaches for defect/damage detection in composite materials. One key technical challenge area included in NASA's Advanced Composite's Project is to develop optimized rapid inspection methods for composite materials. Common manufacturing defects in carbon fiber reinforced polymer (CFRP) composites include fiber waviness (in-plane and out-of-plane), porosity, and disbonds; among others. This paper is an overview of ongoing work to develop ultrasonic wavefield based methods for characterizing manufacturing waviness defects. The paper describes the development and implementation of a custom ultrasound simulation tool that is used to model ultrasonic wave interaction with in-plane fiber waviness (also known as marcelling). Wavefield data processing methods are applied to the simulation data to explore possible routes for quantitative defect characterization.

CFD Prediction on the Pressure Distribution and Streamlines around an Isolated Single-Storey House Considering the Effect of Topographic Characteristics

NASA Astrophysics Data System (ADS)

Abdullah, J.; Zaini, S. S.; Aziz, M. S. A.; Majid, T. A.; Deraman, S. N. C.; Yahya, W. N. W.

2018-04-01

Single-storey houses are classified as low rise building and vulnerable to damages under windstorm event. This study was carried out with the aim to investigate the pressure distribution and streamlines around an isolated house by considering the effect of terrain characteristics. The topographic features such as flat, depression, ridge, and valley, are considered in this study. This simulation were analysed with Ansys FLUENT 14.0 software package. The result showed the topography characteristics influence the value of pressure coefficient and streamlines especially when the house was located at ridge terrain. The findings strongly suggested that wind analysis should include all topographic features in the analysis in order to establish the true wind force exerted on any structure.

NDE and SHM Simulation for CFRP Composites

NASA Technical Reports Server (NTRS)

Leckey, Cara A. C.; Parker, F. Raymond

2014-01-01

Ultrasound-based nondestructive evaluation (NDE) is a common technique for damage detection in composite materials. There is a need for advanced NDE that goes beyond damage detection to damage quantification and characterization in order to enable data driven prognostics. The damage types that exist in carbon fiber-reinforced polymer (CFRP) composites include microcracking and delaminations, and can be initiated and grown via impact forces (due to ground vehicles, tool drops, bird strikes, etc), fatigue, and extreme environmental changes. X-ray microfocus computed tomography data, among other methods, have shown that these damage types often result in voids/discontinuities of a complex volumetric shape. The specific damage geometry and location within ply layers affect damage growth. Realistic threedimensional NDE and structural health monitoring (SHM) simulations can aid in the development and optimization of damage quantification and characterization techniques. This paper is an overview of ongoing work towards realistic NDE and SHM simulation tools for composites, and also discusses NASA's need for such simulation tools in aeronautics and spaceflight. The paper describes the development and implementation of a custom ultrasound simulation tool that is used to model ultrasonic wave interaction with realistic 3-dimensional damage in CFRP composites. The custom code uses elastodynamic finite integration technique and is parallelized to run efficiently on computing cluster or multicore machines.

Streamline-based microfluidic device

NASA Technical Reports Server (NTRS)

Tai, Yu-Chong (Inventor); Zheng, Siyang (Inventor); Kasdan, Harvey (Inventor)

2013-01-01

The present invention provides a streamline-based device and a method for using the device for continuous separation of particles including cells in biological fluids. The device includes a main microchannel and an array of side microchannels disposed on a substrate. The main microchannel has a plurality of stagnation points with a predetermined geometric design, for example, each of the stagnation points has a predetermined distance from the upstream edge of each of the side microchannels. The particles are separated and collected in the side microchannels.

Crashworthiness simulation of composite automotive structures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Botkin, M E; Johnson, N L; Simunovic, S

1998-06-01

In 1990 the Automotive Composites Consortium (ACC) began the investigation of crash worthiness simulation methods for composite materials. A contract was given to Livermore Software Technology Corporation (LSTC) to implement a new damage model in LS-DYNA3D TM specifically for composite structures. This model is in LS-DYNA3D TM and is in use by the ACC partners. In 1994 USCAR, a partnership of American auto companies, entered into a partnership called SCAAP (Super Computing Automotive Applications Partnership) for the express purpose of working with the National Labs on computational oriented research. A CRADA (Cooperative Research and Development Agreement) was signed with Lawrencemore » Livermore National Laboratory, Oak Ridge National Laboratory, Sandia National Laboratory, Argonne National Laboratory, and Los Alamos National Laboratory to work in three distinctly different technical areas, one of which was composites material modeling for crash worthiness. Each Laboratory was assigned a specific modeling task. The ACC was responsible for the technical direction of the composites project and provided all test data for code verification. All new models were to be implemented in DYNA3D and periodically distributed to all partners for testing. Several new models have been developed and implemented. Excellent agreement has been shown between tube crush simulation and experiments.« less

Streamlining: Reducing costs and increasing STS operations effectiveness

NASA Technical Reports Server (NTRS)

Petersburg, R. K.

1985-01-01

The development of streamlining as a concept, its inclusion in the space transportation system engineering and operations support (STSEOS) contract, and how it serves as an incentive to management and technical support personnel is discussed. The mechanics of encouraging and processing streamlining suggestions, reviews, feedback to submitters, recognition, and how individual employee performance evaluations are used to motivation are discussed. Several items that were implemented are mentioned. Information reported and the methodology of determining estimated dollar savings are outlined. The overall effect of this activity on the ability of the McDonnell Douglas flight preparation and mission operations team to support a rapidly increasing flight rate without a proportional increase in cost is illustrated.

User's guide and description of the streamline divergence computer program. [turbulent convective heat transfer

NASA Technical Reports Server (NTRS)

Sulyma, P. R.; Mcanally, J. V.

1975-01-01

The streamline divergence program was developed to demonstrate the capability to trace inviscid surface streamlines and to calculate outflow-corrected laminar and turbulent convective heating rates on surfaces subjected to exhaust plume impingement. The analytical techniques used in formulating this program are discussed. A brief description of the streamline divergence program is given along with a user's guide. The program input and output for a sample case are also presented.

A Study of Two-Equation Turbulence Models on the Elliptic Streamline Flow

NASA Technical Reports Server (NTRS)

Blaisdell, Gregory A.; Qin, Jim H.; Shariff, Karim; Rai, Man Mohan (Technical Monitor)

1995-01-01

Several two-equation turbulence models are compared to data from direct numerical simulations (DNS) of the homogeneous elliptic streamline flow, which combines rotation and strain. The models considered include standard two-equation models and models with corrections for rotational effects. Most of the rotational corrections modify the dissipation rate equation to account for the reduced dissipation rate in rotating turbulent flows, however, the DNS data shows that the production term in the turbulent kinetic energy equation is not modeled correctly by these models. Nonlinear relations for the Reynolds stresses are considered as a means of modifying the production term. Implications for the modeling of turbulent vortices will be discussed.

Overhead Projection Cell for Streamline Flow

ERIC Educational Resources Information Center

Waage, Harold M.

1969-01-01

Describes the construction and operation of an overhead projection apparatus designed to demonstrate streamline flow of a liquid. The apparatus consists of a Plexiglass tank containing water in which plates forming the cell are submerged, a constant level reservoir, an overflow device and a system for marking the flow lines with a dye. (LC)

Aerofoil testing in a self-streamlining flexible walled wind tunnel. Ph.D. Thesis - Jul. 1987

NASA Technical Reports Server (NTRS)

Lewis, Mark Charles

1988-01-01

Two-dimensional self-streamlining flexible walled test sections eliminate, as far as experimentally possible, the top and bottom wall interference effects in transonic airfoil testing. The test section sidewalls are rigid, while the impervious top and bottom walls are flexible and contoured to streamline shapes by a system of jacks, without reference to the airfoil model. The concept of wall contouring to eliminate or minimize test section boundary interference in 2-D testing was first demonstrated by NPL in England during the early 40's. The transonic streamlining strategy proposed, developed and used by NPL has been compared with several modern strategies. The NPL strategy has proved to be surprisingly good at providing a wall interference-free test environment, giving model performance indistinguishable from that obtained using the modern strategies over a wide range of test conditions. In all previous investigations the achievement of wall streamlining in flexible walled test sections has been limited to test sections up to those resulting in the model's shock just extending to a streamlined wall. This work however, has also successfully demonstrated the feasibility of 2-D wall streamlining at test conditions where both model shocks have reached and penetrated through their respective flexible walls. Appropriate streamlining procedures have been established and are uncomplicated, enabling flexible walled test sections to cope easily with these high transonic flows.

48 CFR 252.211-7000 - Acquisition streamlining.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 48 Federal Acquisition Regulations System 3 2010-10-01 2010-10-01 false Acquisition streamlining. 252.211-7000 Section 252.211-7000 Federal Acquisition Regulations System DEFENSE ACQUISITION REGULATIONS SYSTEM, DEPARTMENT OF DEFENSE CLAUSES AND FORMS SOLICITATION PROVISIONS AND CONTRACT CLAUSES Text...

Coupled multi-disciplinary composites behavior simulation

NASA Technical Reports Server (NTRS)

Singhal, Surendra N.; Murthy, Pappu L. N.; Chamis, Christos C.

1993-01-01

The capabilities of the computer code CSTEM (Coupled Structural/Thermal/Electro-Magnetic Analysis) are discussed and demonstrated. CSTEM computationally simulates the coupled response of layered multi-material composite structures subjected to simultaneous thermal, structural, vibration, acoustic, and electromagnetic loads and includes the effect of aggressive environments. The composite material behavior and structural response is determined at its various inherent scales: constituents (fiber/matrix), ply, laminate, and structural component. The thermal and mechanical properties of the constituents are considered to be nonlinearly dependent on various parameters such as temperature and moisture. The acoustic and electromagnetic properties also include dependence on vibration and electromagnetic wave frequencies, respectively. The simulation is based on a three dimensional finite element analysis in conjunction with composite mechanics and with structural tailoring codes, and with acoustic and electromagnetic analysis methods. An aircraft engine composite fan blade is selected as a typical structural component to demonstrate the CSTEM capabilities. Results of various coupled multi-disciplinary heat transfer, structural, vibration, acoustic, and electromagnetic analyses for temperature distribution, stress and displacement response, deformed shape, vibration frequencies, mode shapes, acoustic noise, and electromagnetic reflection from the fan blade are discussed for their coupled effects in hot and humid environments. Collectively, these results demonstrate the effectiveness of the CSTEM code in capturing the coupled effects on the various responses of composite structures subjected to simultaneous multiple real-life loads.

Self streamlining wind tunnel: Low speed testing and transonic test section design

NASA Technical Reports Server (NTRS)

Wolf, S. W. D.; Goodyer, M. J.

1977-01-01

Comprehensive aerodynamic data on an airfoil section were obtained through a wide range of angles of attack, both stalled and unstalled. Data were gathered using a self streamlining wind tunnel and were compared to results obtained on the same section in a conventional wind tunnel. The reduction of wall interference through streamline was demonstrated.

Characterization of an improved 1-3 piezoelectric composite by simulation and experiment.

PubMed

Zhong, Chao; Wang, Likun; Qin, Lei; Zhang, Yanjun

2017-06-16

To increase electromechanical coupling factor of 1-3 piezoelectric composite and reduce its bending deformation under external stress, an improved 1-3 piezoelectric composite is developed. In the improved structure, both epoxy resin and silicone rubber are used as polymer material. The simulation model of the improved 1-3 piezoelectric composite was established using the finite element software ANSYS. The relationship of the performance of the improved composite to the volume percentage of silicone rubber was determined by harmonic response analysis and the bending deformation under external stress was simulated by static analysis. The improved composite samples were prepared by cutting and filling methods, and the performance was tested. The feasibility of the improved structure was verified by finite element simulation and experiment. The electromechanical coupling factor of the improved composite can reach 0.67 and meanwhile the characteristic impedance can decline to 13 MRayl. The electromechanical coupling factor of the improved composite is higher than that of the composite with only epoxy resin as the polymer and the improved composite can reduce bending deformation. Comparison of simulation and experiment, the results of the experiment are in general agreement with those from the simulation. However, most experimental values were higher than the simulation results, and the abnormality of the test results was also more obvious than that of the simulation. These findings may be attributed to slight difference in the material parameters of simulation and experiment.

Effectiveness of and obstacles to antibiotic streamlining to amoxicillin monotherapy in bacteremic pneumococcal pneumonia.

PubMed

Blot, Mathieu; Pivot, Diane; Bourredjem, Abderrahmane; Salmon-Rousseau, Arnaud; de Curraize, Claire; Croisier, Delphine; Chavanet, Pascal; Binquet, Christine; Piroth, Lionel

2017-09-01

Antibiotic streamlining is pivotal to reduce the emergence of resistant bacteria. However, whether streamlining is frequently performed and safe in difficult situations, such as bacteremic pneumococcal pneumonia (BPP), has still to be assessed. All adult patients admitted to Dijon Hospital (France) from 2005 to 2013 who had BPP without complications, and were alive on the third day were enrolled. Clinical, biological, radiological, microbiological and therapeutic data were recorded. A first analysis was conducted to assess factors associated with being on amoxicillin on the third day. A second analysis, adjusting for a propensity score, was performed to determine whether 30-day mortality was associated with streamlining to amoxicillin monotherapy. Of the 196 patients hospitalized for BPP, 161 were still alive on the third day and were included in the study. Treatment was streamlined to amoxicillin in 60 patients (37%). Factors associated with not streamlining were severe pneumonia (OR 3.11, 95%CI [1.23-7.87]) and a first-line antibiotic combination (OR 3.08, 95%CI [1.34-7.09]). By contrast, starting with amoxicillin monotherapy correlated inversely with the risk of subsequent treatment with antibiotics other than amoxicillin (OR 0.06, 95%CI [0.01-0.30]). The Cox model adjusted for the propensity-score analysis showed that streamlining to amoxicillin during BPP was not significantly associated with a higher risk of 30-day mortality (HR 0.38, 95%CI [0.08-1.87]). Streamlining to amoxicillin is insufficiently implemented during BPP. This strategy is safe and potentially associated with ecological and economic benefits; therefore, it should be further encouraged, particularly when antibiotic combinations are started for severe pneumonia. Copyright © 2017. Published by Elsevier B.V.

Research on Streamlines and Aerodynamic Heating for Unstructured Grids on High-Speed Vehicles

NASA Technical Reports Server (NTRS)

DeJarnette, Fred R.; Hamilton, H. Harris (Technical Monitor)

2001-01-01

Engineering codes are needed which can calculate convective heating rates accurately and expeditiously on the surfaces of high-speed vehicles. One code which has proven to meet these needs is the Langley Approximate Three-Dimensional Convective Heating (LATCH) code. It uses the axisymmetric analogue in an integral boundary-layer method to calculate laminar and turbulent heating rates along inviscid surface streamlines. It requires the solution of the inviscid flow field to provide the surface properties needed to calculate the streamlines and streamline metrics. The LATCH code has been used with inviscid codes which calculated the flow field on structured grids, Several more recent inviscid codes calculate flow field properties on unstructured grids. The present research develops a method to calculate inviscid surface streamlines, the streamline metrics, and heating rates using the properties calculated from inviscid flow fields on unstructured grids. Mr. Chris Riley, prior to his departure from NASA LaRC, developed a preliminary code in the C language, called "UNLATCH", to accomplish these goals. No publication was made on his research. The present research extends and improves on the code developed by Riley. Particular attention is devoted to the stagnation region, and the method is intended for programming in the FORTRAN 90 language.

Control software for two dimensional airfoil tests using a self-streamlining flexible walled transonic test section

NASA Technical Reports Server (NTRS)

Wolf, S. W. D.; Goodyer, M. J.

1982-01-01

Operation of the Transonic Self-Streamlining Wind Tunnel (TSWT) involved on-line data acquisition with automatic wall adjustment. A tunnel run consisted of streamlining the walls from known starting contours in iterative steps and acquiring model data. Each run performs what is described as a streamlining cycle. The associated software is presented.

Streamlining the Bankability Process using International Standards

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kurtz, Sarah; Repins, Ingrid L; Kelly, George

NREL has supported the international efforts to create a streamlined process for documenting bankability and/or completion of each step of a PV project plan. IECRE was created for this purpose in 2014. This poster describes the goals, current status of this effort, and how individuals and companies can become involved.

Graphical simulation for aerospace manufacturing

NASA Technical Reports Server (NTRS)

Babai, Majid; Bien, Christopher

1994-01-01

Simulation software has become a key technological enabler for integrating flexible manufacturing systems and streamlining the overall aerospace manufacturing process. In particular, robot simulation and offline programming software is being credited for reducing down time and labor cost, while boosting quality and significantly increasing productivity.

The effects of streamline curvature and swirl on turbulent flows in curved ducts

NASA Technical Reports Server (NTRS)

Cheng, Chih-Hsiung; Farokhi, Saeed

1990-01-01

A technique for improving the numerical predictions of turbulent flows with the effect of streamline curvature is developed. Separated flows, the flow in a curved duct, and swirling flows are examples of flow fields where streamline curvature plays a dominant role. A comprehensive literature review on the effect of streamline curvature was conducted. New algebraic formulations for the eddy viscosity incorporating the kappa-epsilon turbulence model are proposed to account for various effects of streamline curvature. The loci of flow reversal of the separated flows over various backward-facing steps are employed to test the capability of the proposed turbulence model in capturing the effect of local curvature. The inclusion of the effect of longitudinal curvature in the proposed turbulence model is validated by predicting the distributions of the static pressure coefficients in an S-bend duct and in 180 degree turn-around ducts. The proposed turbulence model embedded with transverse curvature modification is substantiated by predicting the decay of the axial velocities in the confined swirling flows. The numerical predictions of different curvature effects by the proposed turbulence models are also reported.

Dynamic Investigation of Release Characteristics of a Streamlined Internal Store from a Simulated Bomb Bay of the Republic F-105 Airplane at Mach Numbers of 0.8, 1.4, and 1.98, Coord. No. AF-222

NASA Technical Reports Server (NTRS)

Lee, John B.

1956-01-01

An investigation has been conducted in the 27- by 27-inch preflight jet of the Langley Pilotless Aircraft Research Station at Wallops Island, Va., of the release characteristics of a dynamically scaled streamlined-type internally carried store from a simulated bomb bay at Mach numbers M(sub o) of 0.8, 1.4, and 1.98. A l/17-scale model of the Republic F-105 half-fuselage and bomb-bay configuration was used with a streamlined store shape of a fineness ratio of 6.00. Simulated altitudes were 3,400 feet at M(sub o) = 0.8, 3,400, and 29,000 feet at M(sub o) = 1.4, and 29,000 feet at M(sub o) = 1.98. At supersonic speeds, high pitching moments are induced on the store in the vicinity of the bomb bay at high dynamic pressures. Successful ejections could not be made with the original configuration at supersonic speeds at near sea-level conditions. The pitching moments caused by unsymmetrical pressures on the store in a disturbed flow field were overcome by replacing the high-aspect-ratio fin with a low-aspect-ratio fin that had a 30-percent area increase which was less subject to aeroelastic effects. Release characteristics of the store were improved by orienting the fins so that they were in a more uniform flow field at the point of store release. The store pitching moments were shown to be reduced by increasing the simulated altitude. Favorable ejections were made at subsonic speeds at near sea-level conditions.

Fast Realistic MRI Simulations Based on Generalized Multi-Pool Exchange Tissue Model

PubMed Central

Velikina, Julia V.; Block, Walter F.; Kijowski, Richard; Samsonov, Alexey A.

2017-01-01

We present MRiLab, a new comprehensive simulator for large-scale realistic MRI simulations on a regular PC equipped with a modern graphical processing unit (GPU). MRiLab combines realistic tissue modeling with numerical virtualization of an MRI system and scanning experiment to enable assessment of a broad range of MRI approaches including advanced quantitative MRI methods inferring microstructure on a sub-voxel level. A flexibl representation of tissue microstructure is achieved in MRiLab by employing the generalized tissue model with multiple exchanging water and macromolecular proton pools rather than a system of independent proton isochromats typically used in previous simulators. The computational power needed for simulation of the biologically relevant tissue models in large 3D objects is gained using parallelized execution on GPU. Three simulated and one actual MRI experiments were performed to demonstrate the ability of the new simulator to accommodate a wide variety of voxel composition scenarios and demonstrate detrimental effects of simplifie treatment of tissue micro-organization adapted in previous simulators. GPU execution allowed ∼200× improvement in computational speed over standard CPU. As a cross-platform, open-source, extensible environment for customizing virtual MRI experiments, MRiLab streamlines the development of new MRI methods, especially those aiming to infer quantitatively tissue composition and microstructure. PMID:28113746

Fast Realistic MRI Simulations Based on Generalized Multi-Pool Exchange Tissue Model.

PubMed

Liu, Fang; Velikina, Julia V; Block, Walter F; Kijowski, Richard; Samsonov, Alexey A

2017-02-01

We present MRiLab, a new comprehensive simulator for large-scale realistic MRI simulations on a regular PC equipped with a modern graphical processing unit (GPU). MRiLab combines realistic tissue modeling with numerical virtualization of an MRI system and scanning experiment to enable assessment of a broad range of MRI approaches including advanced quantitative MRI methods inferring microstructure on a sub-voxel level. A flexible representation of tissue microstructure is achieved in MRiLab by employing the generalized tissue model with multiple exchanging water and macromolecular proton pools rather than a system of independent proton isochromats typically used in previous simulators. The computational power needed for simulation of the biologically relevant tissue models in large 3D objects is gained using parallelized execution on GPU. Three simulated and one actual MRI experiments were performed to demonstrate the ability of the new simulator to accommodate a wide variety of voxel composition scenarios and demonstrate detrimental effects of simplified treatment of tissue micro-organization adapted in previous simulators. GPU execution allowed  ∼ 200× improvement in computational speed over standard CPU. As a cross-platform, open-source, extensible environment for customizing virtual MRI experiments, MRiLab streamlines the development of new MRI methods, especially those aiming to infer quantitatively tissue composition and microstructure.

Effects of complex terrain on atmospheric flow: dividing streamline observations and quantification

NASA Astrophysics Data System (ADS)

Thompson, Michael; Fernando, Harindra; di Sabatino, Silvana; Leo, Laura; University of Notre Dame Team

2013-11-01

As part of the MATERHORN field campaign on atmospheric flow in mountainous terrain, the dividing streamline concept for stratified flow over obstacles was investigated using smoke flow visualization and meteorological measurements. At small Froude numbers (Fr < 1), a stratified flow approaching a mountain either possesses enough kinetic energy to pass over the summit or else flow around the sides, with dividing streamlines separating the two scenarios. An isolated northwestern peak of the Granite Mountain, approximately 60 m in height, was used for the study. Incoming flow velocities and temperature profiles were measured upstream using sonic anemometers and thermocouples mounted on a 32 m tower, while onsite measurements were taken with portable weather stations. Sufficiently strong stratification was developed around 3:00AM GMT, with Froude numbers in the range for dividing streamlines to exist. In the first trial, suitably placed red smoke releases were used and in another trial white smoke was released from a 25 m crane. In both cases well-defined dividing streamlines were observed and its vertical location was at a height about half of the mountain height, which is consistent with theoretical results based on Shepard's formula. This research was supported by the Office of Naval Research (ONR) grant number N00014-11-1-0709.

Streamlining Collaborative Planning in Spacecraft Mission Architectures

NASA Technical Reports Server (NTRS)

Misra, Dhariti; Bopf, Michel; Fishman, Mark; Jones, Jeremy; Kerbel, Uri; Pell, Vince

2000-01-01

During the past two decades, the planning and scheduling community has substantially increased the capability and efficiency of individual planning and scheduling systems. Relatively recently, research work to streamline collaboration between planning systems is gaining attention. Spacecraft missions stand to benefit substantially from this work as they require the coordination of multiple planning organizations and planning systems. Up to the present time this coordination has demanded a great deal of human intervention and/or extensive custom software development efforts. This problem will become acute with increased requirements for cross-mission plan coordination and multi -spacecraft mission planning. The Advanced Architectures and Automation Branch of NASA's Goddard Space Flight Center is taking innovative steps to define collaborative planning architectures, and to identify coordinated planning tools for Cross-Mission Campaigns. Prototypes are being developed to validate these architectures and assess the usefulness of the coordination tools by the planning community. This presentation will focus on one such planning coordination too], named Visual Observation Layout Tool (VOLT), which is currently being developed to streamline the coordination between astronomical missions

Numerical simulation of multi-layered textile composite reinforcement forming

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, P.; Hamila, N.; Boisse, P.

2011-05-04

One important perspective in aeronautics is to produce large, thick or/and complex structural composite parts. The forming stage presents an important role during the whole manufacturing process, especially for LCM processes (Liquid Composites Moulding) or CFRTP (Continuous Fibre Reinforcements and Thermoplastic resin). Numerical simulations corresponding to multi-layered composite forming allow the prediction for a successful process to produce the thick parts, and importantly, the positions of the fibres after forming to be known. This paper details a set of simulation examples carried out by using a semi-discrete shell finite element made up of unit woven cells. The internal virtual workmore » is applied on all woven cells of the element taking into account tensions, in-plane shear and bending effects. As one key problem, the contact behaviours of tool/ply and ply/ply are described in the numerical model. The simulation results not only improve our understanding of the multi-layered composite forming process but also point out the importance of the fibre orientation and inter-ply friction during formability.« less

The impact of a streamlined funding application process on application time: two cross-sectional surveys of Australian researchers

PubMed Central

Barnett, Adrian G; Graves, Nicholas; Clarke, Philip; Herbert, Danielle

2015-01-01

Objective To examine if streamlining a medical research funding application process saved time for applicants. Design Cross-sectional surveys before and after the streamlining. Setting The National Health and Medical Research Council (NHMRC) of Australia. Participants Researchers who submitted one or more NHMRC Project Grant applications in 2012 or 2014. Main outcome measures Average researcher time spent preparing an application and the total time for all applications in working days. Results The average time per application increased from 34 working days before streamlining (95% CI 33 to 35) to 38 working days after streamlining (95% CI 37 to 39; mean difference 4 days, bootstrap p value <0.001). The estimated total time spent by all researchers on applications after streamlining was 614 working years, a 67-year increase from before streamlining. Conclusions Streamlined applications were shorter but took longer to prepare on average. Researchers may be allocating a fixed amount of time to preparing funding applications based on their expected return, or may be increasing their time in response to increased competition. Many potentially productive years of researcher time are still being lost to preparing failed applications. PMID:25596201

Challenges of NDE simulation tool validation, optimization, and utilization for composites

NASA Astrophysics Data System (ADS)

Leckey, Cara A. C.; Seebo, Jeffrey P.; Juarez, Peter

2016-02-01

Rapid, realistic nondestructive evaluation (NDE) simulation tools can aid in inspection optimization and prediction of inspectability for advanced aerospace materials and designs. NDE simulation tools may someday aid in the design and certification of aerospace components; potentially shortening the time from material development to implementation by industry and government. Furthermore, ultrasound modeling and simulation are expected to play a significant future role in validating the capabilities and limitations of guided wave based structural health monitoring (SHM) systems. The current state-of-the-art in ultrasonic NDE/SHM simulation is still far from the goal of rapidly simulating damage detection techniques for large scale, complex geometry composite components/vehicles containing realistic damage types. Ongoing work at NASA Langley Research Center is focused on advanced ultrasonic simulation tool development. This paper discusses challenges of simulation tool validation, optimization, and utilization for composites. Ongoing simulation tool development work is described along with examples of simulation validation and optimization challenges that are more broadly applicable to all NDE simulation tools. The paper will also discuss examples of simulation tool utilization at NASA to develop new damage characterization methods for composites, and associated challenges in experimentally validating those methods.

Case studies in geographic information systems for environmental streamlining

DOT National Transportation Integrated Search

2012-05-31

This 2012 summary report addresses the current use of geographic information systems (GIS) and related technologies by State Departments of Transportation (DOTs) for environmental streamlining and stewardship, particularly in relation to the National...

Two-dimensional Lagrangian simulation of suspended sediment

USGS Publications Warehouse

Schoellhamer, David H.

1988-01-01

A two-dimensional laterally averaged model for suspended sediment transport in steady gradually varied flow that is based on the Lagrangian reference frame is presented. The layered Lagrangian transport model (LLTM) for suspended sediment performs laterally averaged concentration. The elevations of nearly horizontal streamlines and the simulation time step are selected to optimize model stability and efficiency. The computational elements are parcels of water that are moved along the streamlines in the Lagrangian sense and are mixed with neighboring parcels. Three applications show that the LLTM can accurately simulate theoretical and empirical nonequilibrium suspended sediment distributions and slug injections of suspended sediment in a laboratory flume.

The impact of a streamlined funding application process on application time: two cross-sectional surveys of Australian researchers.

PubMed

Barnett, Adrian G; Graves, Nicholas; Clarke, Philip; Herbert, Danielle

2015-01-16

To examine if streamlining a medical research funding application process saved time for applicants. Cross-sectional surveys before and after the streamlining. The National Health and Medical Research Council (NHMRC) of Australia. Researchers who submitted one or more NHMRC Project Grant applications in 2012 or 2014. Average researcher time spent preparing an application and the total time for all applications in working days. The average time per application increased from 34 working days before streamlining (95% CI 33 to 35) to 38 working days after streamlining (95% CI 37 to 39; mean difference 4 days, bootstrap p value <0.001). The estimated total time spent by all researchers on applications after streamlining was 614 working years, a 67-year increase from before streamlining. Streamlined applications were shorter but took longer to prepare on average. Researchers may be allocating a fixed amount of time to preparing funding applications based on their expected return, or may be increasing their time in response to increased competition. Many potentially productive years of researcher time are still being lost to preparing failed applications. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

Analysis of Jupiter's Oval BA: A Streamlined Approach

NASA Technical Reports Server (NTRS)

Sussman, Michael G.; Chanover, Nancy J.; Simon-Miller, Amy A.; Vasavada, Ashwin R.; Beebe, Reta F.

2010-01-01

We present a novel method of constructing streamlines to derive wind speeds within jovian vortices and demonstrate its application to Oval BA for 2001 pre-reddened Cassini flyby data, 2007 post-reddened New Horizons flyby data, and 1998 Galileo data of precursor Oval DE. Our method, while automated, attempts to combine the advantages of both automated and manual cloud tracking methods. The southern maximum wind speed of Oval BA does not show significant changes between these data sets to within our measurement uncertainty. The northern maximum dries appear to have increased in strength during this time interval, tvhich likely correlates with the oval's return to a symmetric shape. We demonstrate how the use of closed streamlines can provide measurements of vorticity averaged over the encircled area with no a priori assumptions concerning oval shape. We find increased averaged interior vorticity between pre- and post-reddened Oval BA, with the precursor Oval DE occupying a middle value of vorticity between these two.

Composite laminate failure parameter optimization through four-point flexure experimentation and analysis

DOE PAGES

Nelson, Stacy; English, Shawn; Briggs, Timothy

2016-05-06

Fiber-reinforced composite materials offer light-weight solutions to many structural challenges. In the development of high-performance composite structures, a thorough understanding is required of the composite materials themselves as well as methods for the analysis and failure prediction of the relevant composite structures. However, the mechanical properties required for the complete constitutive definition of a composite material can be difficult to determine through experimentation. Therefore, efficient methods are necessary that can be used to determine which properties are relevant to the analysis of a specific structure and to establish a structure's response to a material parameter that can only be definedmore » through estimation. The objectives of this paper deal with demonstrating the potential value of sensitivity and uncertainty quantification techniques during the failure analysis of loaded composite structures; and the proposed methods are applied to the simulation of the four-point flexural characterization of a carbon fiber composite material. Utilizing a recently implemented, phenomenological orthotropic material model that is capable of predicting progressive composite damage and failure, a sensitivity analysis is completed to establish which material parameters are truly relevant to a simulation's outcome. Then, a parameter study is completed to determine the effect of the relevant material properties' expected variations on the simulated four-point flexural behavior as well as to determine the value of an unknown material property. This process demonstrates the ability to formulate accurate predictions in the absence of a rigorous material characterization effort. Finally, the presented results indicate that a sensitivity analysis and parameter study can be used to streamline the material definition process as the described flexural characterization was used for model validation.« less

Ceramic matrix composite behavior -- Computational simulation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chamis, C.C.; Murthy, P.L.N.; Mital, S.K.

Development of analytical modeling and computational capabilities for the prediction of high temperature ceramic matrix composite behavior has been an ongoing research activity at NASA-Lewis Research Center. These research activities have resulted in the development of micromechanics based methodologies to evaluate different aspects of ceramic matrix composite behavior. The basis of the approach is micromechanics together with a unique fiber substructuring concept. In this new concept the conventional unit cell (the smallest representative volume element of the composite) of micromechanics approach has been modified by substructuring the unit cell into several slices and developing the micromechanics based equations at themore » slice level. Main advantage of this technique is that it can provide a much greater detail in the response of composite behavior as compared to a conventional micromechanics based analysis and still maintains a very high computational efficiency. This methodology has recently been extended to model plain weave ceramic composites. The objective of the present paper is to describe the important features of the modeling and simulation and illustrate with select examples of laminated as well as woven composites.« less

Fast Automatic Segmentation of White Matter Streamlines Based on a Multi-Subject Bundle Atlas.

PubMed

Labra, Nicole; Guevara, Pamela; Duclap, Delphine; Houenou, Josselin; Poupon, Cyril; Mangin, Jean-François; Figueroa, Miguel

2017-01-01

This paper presents an algorithm for fast segmentation of white matter bundles from massive dMRI tractography datasets using a multisubject atlas. We use a distance metric to compare streamlines in a subject dataset to labeled centroids in the atlas, and label them using a per-bundle configurable threshold. In order to reduce segmentation time, the algorithm first preprocesses the data using a simplified distance metric to rapidly discard candidate streamlines in multiple stages, while guaranteeing that no false negatives are produced. The smaller set of remaining streamlines is then segmented using the original metric, thus eliminating any false positives from the preprocessing stage. As a result, a single-thread implementation of the algorithm can segment a dataset of almost 9 million streamlines in less than 6 minutes. Moreover, parallel versions of our algorithm for multicore processors and graphics processing units further reduce the segmentation time to less than 22 seconds and to 5 seconds, respectively. This performance enables the use of the algorithm in truly interactive applications for visualization, analysis, and segmentation of large white matter tractography datasets.

Coupled multi-disciplinary simulation of composite engine structures in propulsion environment

NASA Technical Reports Server (NTRS)

Chamis, Christos C.; Singhal, Surendra N.

1992-01-01

A computational simulation procedure is described for the coupled response of multi-layered multi-material composite engine structural components which are subjected to simultaneous multi-disciplinary thermal, structural, vibration, and acoustic loadings including the effect of hostile environments. The simulation is based on a three dimensional finite element analysis technique in conjunction with structural mechanics codes and with acoustic analysis methods. The composite material behavior is assessed at the various composite scales, i.e., the laminate/ply/constituents (fiber/matrix), via a nonlinear material characterization model. Sample cases exhibiting nonlinear geometrical, material, loading, and environmental behavior of aircraft engine fan blades, are presented. Results for deformed shape, vibration frequency, mode shapes, and acoustic noise emitted from the fan blade, are discussed for their coupled effect in hot and humid environments. Results such as acoustic noise for coupled composite-mechanics/heat transfer/structural/vibration/acoustic analyses demonstrate the effectiveness of coupled multi-disciplinary computational simulation and the various advantages of composite materials compared to metals.

Trace gas composition in the Asian summer monsoon anticyclone: a case study based on aircraft observations and model simulations

NASA Astrophysics Data System (ADS)

Gottschaldt, Klaus-D.; Schlager, Hans; Baumann, Robert; Bozem, Heiko; Eyring, Veronika; Hoor, Peter; Jöckel, Patrick; Jurkat, Tina; Voigt, Christiane; Zahn, Andreas; Ziereis, Helmut

2017-05-01

We present in situ measurements of the trace gas composition of the upper tropospheric (UT) Asian summer monsoon anticyclone (ASMA) performed with the High Altitude and Long Range Research Aircraft (HALO) in the frame of the Earth System Model Validation (ESMVal) campaign. Air masses with enhanced O3 mixing ratios were encountered after entering the ASMA at its southern edge at about 150 hPa on 18 September 2012. This is in contrast to the presumption that the anticyclone's interior is dominated by recently uplifted air with low O3 in the monsoon season. We also observed enhanced CO and HCl in the ASMA, which are tracers for boundary layer pollution and tropopause layer (TL) air or stratospheric in-mixing respectively. In addition, reactive nitrogen was enhanced in the ASMA. Along the HALO flight track across the ASMA boundary, strong gradients of these tracers separate anticyclonic from outside air. Lagrangian trajectory calculations using HYSPLIT show that HALO sampled a filament of UT air three times, which included air masses uplifted from the lower or mid-troposphere north of the Bay of Bengal. The trace gas gradients between UT and uplifted air masses were preserved during transport within a belt of streamlines fringing the central part of the anticyclone (fringe), but are smaller than the gradients across the ASMA boundary. Our data represent the first in situ observations across the southern part and downstream of the eastern ASMA flank. Back-trajectories starting at the flight track furthermore indicate that HALO transected the ASMA where it was just splitting into a Tibetan and an Iranian part. The O3-rich filament is diverted from the fringe towards the interior of the original anticyclone, and is at least partially bound to become part of the new Iranian eddy. A simulation with the ECHAM/MESSy Atmospheric Chemistry (EMAC) model is found to reproduce the observations reasonably well. It shows that O3-rich air is entrained by the outer streamlines of the

Empty test section streamlining of the transonic self-streamlining wind tunnel fitted with new walls

NASA Technical Reports Server (NTRS)

Lewis, M. C.

1988-01-01

The original flexible top and bottom walls of the Transonic Self-Streamlining Wind Tunnel (TSWT), at the University of Southampton, have been replaced with new walls featuring a larger number of static pressure tappings and detailed mechanical improvements. This report describes the streamling method, results, and conclusions of a series of tests aimed at defining sets of aerodynamically straight wall contours for the new flexible walls. This procedure is a necessary prelude to model testing. The quality of data obtained compares favorably with the aerodynamically straight data obtained with the old walls. No operational difficulties were experienced with the new walls.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mehmani, Yashar; Oostrom, Martinus; Balhoff, Matthew

2014-03-20

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

Analysis of Streamline Separation at Infinity Using Time-Discrete Markov Chains.

PubMed

Reich, W; Scheuermann, G

2012-12-01

Existing methods for analyzing separation of streamlines are often restricted to a finite time or a local area. In our paper we introduce a new method that complements them by allowing an infinite-time-evaluation of steady planar vector fields. Our algorithm unifies combinatorial and probabilistic methods and introduces the concept of separation in time-discrete Markov-Chains. We compute particle distributions instead of the streamlines of single particles. We encode the flow into a map and then into a transition matrix for each time direction. Finally, we compare the results of our grid-independent algorithm to the popular Finite-Time-Lyapunov-Exponents and discuss the discrepancies.

An overview of computational simulation methods for composite structures failure and life analysis

NASA Technical Reports Server (NTRS)

Chamis, Christos C.

1993-01-01

Three parallel computational simulation methods are being developed at the LeRC Structural Mechanics Branch (SMB) for composite structures failure and life analysis: progressive fracture CODSTRAN; hierarchical methods for high-temperature composites; and probabilistic evaluation. Results to date demonstrate that these methods are effective in simulating composite structures failure/life/reliability.

Effect of nose shape on three-dimensional stagnation region streamlines and heating rates

NASA Technical Reports Server (NTRS)

Hassan, Basil; Dejarnette, Fred R.; Zoby, E. V.

1991-01-01

A new method for calculating the three-dimensional inviscid surface streamlines and streamline metrics using Cartesian coordinates and time as the independent variable of integration has been developed. The technique calculates the streamline from a specified point on the body to a point near the stagnation point by using a prescribed pressure distribution in the Euler equations. The differential equations, which are singular at the stagnation point, are of the two point boundary value problem type. Laminar heating rates are calculated using the axisymmetric analog concept for three-dimensional boundary layers and approximate solutions to the axisymmetric boundary layer equations. Results for elliptic conic forebody geometries show that location of the point of maximum heating depends on the type of conic in the plane of symmetry and the angle of attack, and that this location is in general different from the stagnation point. The new method was found to give smooth predictions of heat transfer in the nose region where previous methods gave oscillatory results.

The effects of simulated space environmental parameters on six commercially available composite materials

NASA Technical Reports Server (NTRS)

Funk, Joan G.; Sykes, George F., Jr.

1989-01-01

The effects of simulated space environmental parameters on microdamage induced by the environment in a series of commercially available graphite-fiber-reinforced composite materials were determined. Composites with both thermoset and thermoplastic resin systems were studied. Low-Earth-Orbit (LEO) exposures were simulated by thermal cycling; geosynchronous-orbit (GEO) exposures were simulated by electron irradiation plus thermal cycling. The thermal cycling temperature range was -250 F to either 200 F or 150 F. The upper limits of the thermal cycles were different to ensure that an individual composite material was not cycled above its glass transition temperature. Material response was characterized through assessment of the induced microcracking and its influence on mechanical property changes at both room temperature and -250 F. Microdamage was induced in both thermoset and thermoplastic advanced composite materials exposed to the simulated LEO environment. However, a 350 F cure single-phase toughened epoxy composite was not damaged during exposure to the LEO environment. The simuated GEO environment produced microdamage in all materials tested.

A Homogenization Approach for Design and Simulation of Blast Resistant Composites

NASA Astrophysics Data System (ADS)

Sheyka, Michael

Structural composites have been used in aerospace and structural engineering due to their high strength to weight ratio. Composite laminates have been successfully and extensively used in blast mitigation. This dissertation examines the use of the homogenization approach to design and simulate blast resistant composites. Three case studies are performed to examine the usefulness of different methods that may be used in designing and optimizing composite plates for blast resistance. The first case study utilizes a single degree of freedom system to simulate the blast and a reliability based approach. The first case study examines homogeneous plates and the optimal stacking sequence and plate thicknesses are determined. The second and third case studies use the homogenization method to calculate the properties of composite unit cell made of two different materials. The methods are integrated with dynamic simulation environments and advanced optimization algorithms. The second case study is 2-D and uses an implicit blast simulation, while the third case study is 3-D and simulates blast using the explicit blast method. Both case studies 2 and 3 rely on multi-objective genetic algorithms for the optimization process. Pareto optimal solutions are determined in case studies 2 and 3. Case study 3 is an integrative method for determining optimal stacking sequence, microstructure and plate thicknesses. The validity of the different methods such as homogenization, reliability, explicit blast modeling and multi-objective genetic algorithms are discussed. Possible extension of the methods to include strain rate effects and parallel computation is also examined.

The Effects of Propulsive Jetting on Drag of a Streamlined body

NASA Astrophysics Data System (ADS)

Krieg, Michael; Mohseni, Kamran

2017-11-01

Recently an abundance of bioinspired underwater vehicles have emerged to leverage eons of evolution. Our group has developed a propulsion technique inspired by jellyfish and squid. Propulsive jets are generated by ingesting and expelling water from a flexible internal cavity. We have demonstrated thruster capabilities for maneuvering on AUV platforms, where the internal thruster geometry minimized forward drag; however, such a setup cannot characterize propulsive efficiency. Therefore, we created a new streamlined vehicle platform that produces unsteady jets for forward propulsion rather than maneuvering. The streamlined jetting body is placed in a water tunnel and held stationary while jetting frequency and background flow velocity are varied. For each frequency/velocity pair the flow field is measured around the surface and in the wake using PIV. Using the zero jetting frequency as a baseline for each background velocity, the passive body drag is related to the velocity distribution. For cases with active jetting the drag and jetting forces are estimated from the velocity field and compared to the passive case. For this streamlined body, the entrainment of surrounding flow into the propulsive jet can reduce drag forces in addition to the momentum transfer of the jet itself. Office of Naval Research.

SUPG Finite Element Simulations of Compressible Flows

NASA Technical Reports Server (NTRS)

Kirk, Brnjamin, S.

2006-01-01

The Streamline-Upwind Petrov-Galerkin (SUPG) finite element simulations of compressible flows is presented. The topics include: 1) Introduction; 2) SUPG Galerkin Finite Element Methods; 3) Applications; and 4) Bibliography.

Methods to expedite and streamline utility relocations for road projects.

DOT National Transportation Integrated Search

2014-12-01

This report describes best practices and tools to streamline and expedite utility relocations when they : are required as part of road construction projects. As part of this effort, a research team from the : Kentucky Transportation Center (KTC) cond...

Forming simulation of woven composite fibers and its influence on structural performance

NASA Astrophysics Data System (ADS)

Divine, Vincent; Beauchesne, Erwan; Roy, Subir; Palaniswamy, Hariharasudhan

2013-12-01

In recent years, the interest in composite material as a replacement for metals has been growing. The automotive industry, in its constant quest for weight reduction, is now seriously considering composite materials as a substitute for sheet metal components to meet future fuel consumption standards. However, composite forming processes are expensive and difficult to control because of its complex composition with fiber and matrix layers or plies and its dependency on many parameters, such as non-linearity of tensile stiffness, effect of shear rate, temperature and friction. Hence, numerical simulation could be a viable approach to predict material behavior during composite forming. The objective of this study is to highlight capabilities of RADIOSS®, a non-linear finite element analysis based structural solver commonly used for stamping and crash analyses, to simulate forming simulation of composite plies made from woven fibers. For validation the well-known double dome model is used with material data published in NUMISHEET'05 proceedings. It is modeled as a woven fabric with an elastic anisotropic fabric material law available in RADIOSS. This material law is able to consider properties along the two directions of anisotropy, warp and weft. The compared result is the shear angle after stamping that is, the variation of angle between warp and weft fibers, at several prescribed points on the ply. The variation of this angle has a strong impact on material characteristics which severely deteriorates when a critical value is reached. Hence, a study on crash simulations is performed, after mapping fibers angles from stamping simulation.

GENOA-PFA: Progressive Fracture in Composites Simulated Computationally

NASA Technical Reports Server (NTRS)

Murthy, Pappu L. N.

2000-01-01

GENOA-PFA is a commercial version of the Composite Durability Structural Analysis (CODSTRAN) computer program that simulates the progression of damage ultimately leading to fracture in polymer-matrix-composite (PMC) material structures under various loading and environmental conditions. GENOA-PFA offers several capabilities not available in other programs developed for this purpose, making it preferable for use in analyzing the durability and damage tolerance of complex PMC structures in which the fiber reinforcements occur in two- and three-dimensional weaves and braids. GENOA-PFA implements a progressive-fracture methodology based on the idea that a structure fails when flaws that may initially be small (even microscopic) grow and/or coalesce to a critical dimension where the structure no longer has an adequate safety margin to avoid catastrophic global fracture. Damage is considered to progress through five stages: (1) initiation, (2) growth, (3) accumulation (coalescence of propagating flaws), (4) stable propagation (up to the critical dimension), and (5) unstable or very rapid propagation (beyond the critical dimension) to catastrophic failure. The computational simulation of progressive failure involves formal procedures for identifying the five different stages of damage and for relating the amount of damage at each stage to the overall behavior of the deteriorating structure. In GENOA-PFA, mathematical modeling of the composite physical behavior involves an integration of simulations at multiple, hierarchical scales ranging from the macroscopic (lamina, laminate, and structure) to the microscopic (fiber, matrix, and fiber/matrix interface), as shown in the figure. The code includes algorithms to simulate the progression of damage from various source defects, including (1) through-the-thickness cracks and (2) voids with edge, pocket, internal, or mixed-mode delaminations.

Streamlining environmental product declarations: a stage model

NASA Astrophysics Data System (ADS)

Lefebvre, Elisabeth; Lefebvre, Louis A.; Talbot, Stephane; Le Hen, Gael

2001-02-01

General public environmental awareness and education is increasing, therefore stimulating the demand for reliable, objective and comparable information about products' environmental performances. The recently published standard series ISO 14040 and ISO 14025 are normalizing the preparation of Environmental Product Declarations (EPDs) containing comprehensive information relevant to a product's environmental impact during its life cycle. So far, only a few environmentally leading manufacturing organizations have experimented the preparation of EPDs (mostly from Europe), demonstrating its great potential as a marketing weapon. However the preparation of EPDs is a complex process, requiring collection and analysis of massive amounts of information coming from disparate sources (suppliers, sub-contractors, etc.). In a foreseeable future, the streamlining of the EPD preparation process will require product manufacturers to adapt their information systems (ERP, MES, SCADA) in order to make them capable of gathering, and transmitting the appropriate environmental information. It also requires strong functional integration all along the product supply chain in order to ensure that all the information is made available in a standardized and timely manner. The goal of the present paper is two fold: first to propose a transitional model towards green supply chain management and EPD preparation; second to identify key technologies and methodologies allowing to streamline the EPD process and subsequently the transition toward sustainable product development

Consolidation modelling for thermoplastic composites forming simulation

NASA Astrophysics Data System (ADS)

Xiong, H.; Rusanov, A.; Hamila, N.; Boisse, P.

2016-10-01

Pre-impregnated thermoplastic composites are widely used in the aerospace industry for their excellent mechanical properties, Thermoforming thermoplastic prepregs is a fast manufacturing process, the automotive industry has shown increasing interest in this manufacturing processes, in which the reconsolidation is an essential stage. The model of intimate contact is investigated as the consolidation model, compression experiments have been launched to identify the material parameters, several numerical tests show the influents of the temperature and pressure applied during processing. Finally, a new solid-shell prismatic element has been presented for the simulation of consolidation step in the thermoplastic composites forming process.

Using the Triad Approach to Streamline Brownfields Site Assessment and Cleanup

EPA Pesticide Factsheets

EPA's Brownfields Technology Support Center (BTSC) has prepared this document to provide an educational tool for site owners, project managers, and regulators to help streamline assessment and cleanup activities at brownfields sites.

A streamline curvature method for design of supercritical and subcritical airfoils

NASA Technical Reports Server (NTRS)

Barger, R. L.; Brooks, C. W., Jr.

1974-01-01

An airfoil design procedure, applicable to both subcritical and supercritical airfoils, is described. The method is based on the streamline curvature velocity equation. Several examples illustrating this method are presented and discussed.

76 FR 24339 - Streamlining Service Delivery and Improving Customer Service

Federal Register 2010, 2011, 2012, 2013, 2014

2011-05-02

... Order 13571 of April 27, 2011 Streamlining Service Delivery and Improving Customer Service By the... Customer Service Standards), issued on September 11, 1993, requires agencies that provide significant services directly to the public to identify and survey their customers, establish service standards and...

Stripping Away the Forest; Sweden's Glacially Streamlined Landscape Evaluated through Lidar

NASA Astrophysics Data System (ADS)

Dowling, T.; Spagnolo, M.; Moller, P.

2014-12-01

The newly available Swedish National Height Model (SNHM) is a 2.0 m horizontal, and 0.1 m vertical resolution digital elevation model (DEM) that is free at the point of use for researchers based at Swedish institutions. With coverage currently at ~80% of the country and due to be completed by 2015 this spatially extensive, high resolution dataset has opened up new avenues of research for Quaternary geology in the country. The work presented here utilises the SNHM to map and evaluate more than 10,000 glacially streamlined landforms in the south-east of Sweden. The subsequently extracted morphological variables of length, width and height are then used to investiagte three areas; to test recent conclusions drawn from the glacially streamlined landscapes of Great Britain and North America/Canada, to assess the impact of different core types on the morphological expression of said features and to attempt to calculate which morphological variable best accounts for the variability seen in the dataset. It is found that in common with drumlins found in the British Isles, and elsewhere, their characteristics can be described by a log-normal distribution. However the long tail of the features characteristic distributions can cause problems for many of the commonly applied statistical methods of evaluation. Furthermore a re-appraisal of some conclusions drawn by previous works as to the presence of a fundamental scaling law in streamlined feature elongation is necessary due to evidence gathered here. Additionally; based on a limited sample size it has been found that it is not possible to differentiate a streamlined landform's core type based on their morphological characteristics alone. Larger 'known'-core data sets may be able to do so, based upon the length of a feature for example, however the sample size here was not sufficient to allow significant differences to come to the fore should they exist. And lastly, the extracted variable 'height' was found to account for the

Combined bending and thermal fatigue of high-temperature metal-matrix composites - Computational simulation

NASA Technical Reports Server (NTRS)

Gotsis, Pascal K.; Chamis, Christos C.

1992-01-01

The nonlinear behavior of a high-temperature metal-matrix composite (HT-MMC) was simulated by using the metal matrix composite analyzer (METCAN) computer code. The simulation started with the fabrication process, proceeded to thermomechanical cyclic loading, and ended with the application of a monotonic load. Classical laminate theory and composite micromechanics and macromechanics are used in METCAN, along with a multifactor interaction model for the constituents behavior. The simulation of the stress-strain behavior from the macromechanical and the micromechanical points of view, as well as the initiation and final failure of the constituents and the plies in the composite, were examined in detail. It was shown that, when the fibers and the matrix were perfectly bonded, the fracture started in the matrix and then propagated with increasing load to the fibers. After the fibers fractured, the composite lost its capacity to carry additional load and fractured.

Combined thermal and bending fatigue of high-temperature metal-matrix composites: Computational simulation

NASA Technical Reports Server (NTRS)

Gotsis, Pascal K.

1991-01-01

The nonlinear behavior of a high-temperature metal-matrix composite (HT-MMC) was simulated by using the metal matrix composite analyzer (METCAN) computer code. The simulation started with the fabrication process, proceeded to thermomechanical cyclic loading, and ended with the application of a monotonic load. Classical laminate theory and composite micromechanics and macromechanics are used in METCAN, along with a multifactor interaction model for the constituents behavior. The simulation of the stress-strain behavior from the macromechanical and the micromechanical points of view, as well as the initiation and final failure of the constituents and the plies in the composite, were examined in detail. It was shown that, when the fibers and the matrix were perfectly bonded, the fracture started in the matrix and then propagated with increasing load to the fibers. After the fibers fractured, the composite lost its capacity to carry additional load and fractured.

78 FR 36677 - Radio Experimentation and Market Trials-Streamlining Rules

Federal Register 2010, 2011, 2012, 2013, 2014

2013-06-19

... Experimentation and Market Trials--Streamlining Rules AGENCY: Federal Communications Commission. ACTION: Final rule. SUMMARY: In this document the Commission modifies on its own motion the rules adopted in this... being conducted under a program, medical testing, and compliance testing license. Thus, this action will...

Lidar - DOE ARM StreamLine Doppler Lidar (Halo) - Raw Data

DOE Data Explorer

Newsom, Rob

2017-11-20

1. Evaluate performance of the Halo Photonics Streamline lidar against a calibrated reference (i.e. the BAO tower). 2. Provide measurements of vertical velocity for use with other scanning lidars to better constrain velocity retrievals. 3. Provide colocated reference for comparison with Vindicator lidars.

Development of an alkaline/surfactant/polymer compositional reservoir simulator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bhuyan, D.

1989-01-01

The mathematical formulation of a generalized three-dimensional compositional reservoir simulator for high-pH chemical flooding processes is presented in this work. The model assumes local thermodynamic equilibrium with respect to both reaction chemistry and phase behavior and calculates equilibrium electrolyte and phase compositions as a function of time and position. The reaction chemistry considers aqueous electrolytic chemistry, precipitation/dissolution of minerals, ion exchange reactions on matrix surface, reaction of acidic components of crude oil with the bases in the aqueous solution and cation exchange reactions with the micelles. The simulator combines this detailed reaction chemistry associated with these processes with the extensivemore » physical and flow property modeling schemes of an existing chemical flood simulator (UTCHEM) to model the multiphase, multidimensional displacement processes. The formulation of the chemical equilibrium model is quite general and is adaptable to simulate a variety of chemical descriptions. In addition to its use in the simulation of high-pH chemical flooding processes, the model will find application in the simulation of other reactive flow problems like the ground water contamination, reinjection of produced water, chemical waste disposal, etc. in one, two or three dimensions and under multiphase flow conditions. In this work, the model is used to simulate several hypothetical cases of high-pH chemical floods, which include cases from a simple alkaline preflush of a micellar/polymer flood to surfactant enhanced alkaline-polymer flooding and the results are analyzed. Finally, a few published alkaline, alkaline-polymer and surfactant-alkaline-polymer corefloods are simulated and compared with the experimental results.« less

Novel diffusion tensor imaging technique reveals developmental streamline volume changes in the corticospinal tract associated with leg motor control

PubMed Central

Kamson, David O.; Juhász, Csaba; Chugani, Harry T.; Jeong, Jeong-Won

2014-01-01

Background Diffusion tensor imaging (DTI) has expanded our knowledge of corticospinal tract (CST) anatomy and development. However, previous developmental DTI studies assessed the CST as a whole, overlooking potential differences in development of its components related to control of the upper and lower extremities. The present cross-sectional study investigated age-related changes, side and gender differences in streamline volume of the leg- and hand-related segments of the CST in children. Subjects and methods DTI data of 31 children (1–14years; mean age: 6±4years; 17 girls) with normal conventional MRI were analyzed. Leg- and hand-related CST streamline volumes were quantified separately, using a recently validated novel tractography approach. CST streamline volumes on both sides were compared between genders and correlated with age. Results Higher absolute streamline volumes were found in the left leg-related CST compared to the right (p=0.001) without a gender effect (p=0.4), whereas no differences were found in the absolute hand-related CST volumes (p>0.4). CST leg-related streamline volumes, normalized to hemispheric white matter volumes, declined with age in the right hemisphere only (R=−.51; p=0.004). Absolute leg-related CST streamline volumes showed similar, but slightly weaker correlations. Hand-related absolute or normalized CST streamline volumes showed no age-related variations on either side. Conclusion These results suggest differential development of CST segments controlling hand vs. leg movements. Asymmetric volume changes in the lower limb motor pathway may be secondary to gradually strengthening left hemispheric dominance and is consistent with previous data suggesting that footedness is a better predictor of hemispheric lateralization than handedness. PMID:25027193

Finite element simulation of a novel composite light-weight microporous cladding panel

NASA Astrophysics Data System (ADS)

Tian, Lida; Wang, Dongyan

2018-04-01

A novel composite light-weight microporous cladding panel with matched connection detailing is developed. Numerical simulation on the experiment is conducted by ABAQUS. The accuracy and rationality of the finite element model is verified by comparison between the simulation and the experiment results. It is also indicated that the novel composite cladding panel is of desirable bearing capacity, stiffness and deformability under out-of-plane load.

A Recipe for Streamlining Mission Management

NASA Technical Reports Server (NTRS)

Mitchell, Andrew E.; Semancik, Susan K.

2004-01-01

This paper describes a project's design and implementation for streamlining mission management with knowledge capture processes across multiple organizations of a NASA directorate. Thc project's focus is on standardizing processes and reports; enabling secure information access and case of maintenance; automating and tracking appropriate workflow rules through process mapping; and infusing new technologies. This paper will describe a small team's experiences using XML technologies through an enhanced vendor suite of applications integrated on Windows-based platforms called the Wallops Integrated Scheduling and Document Management System (WISDMS). This paper describes our results using this system in a variety of endeavors, including providing range project scheduling and resource management for a Range and Mission Management Office; implementing an automated Customer Feedback system for a directorate; streamlining mission status reporting across a directorate; and initiating a document management, configuration management and portal access system for a Range Safety Office's programs. The end result is a reduction of the knowledge gap through better integration and distribution of information, improved process performance, automated metric gathering, and quicker identification of problem areas and issues. However, the real proof of the pudding comes through overcoming the user's reluctance to replace familiar, seasoned processes with new technology ingredients blended with automated procedures in an untested recipe. This paper shares some of the team's observations that led to better implementation techniques, as well as an IS0 9001 Best Practices citation. This project has provided a unique opportunity to advance NASA's competency in new technologies, as well as to strategically implement them within an organizational structure, while wetting the appetite for continued improvements in mission management.

Numerical Simulation of Creep Characteristic for Composite Rock Mass with Weak Interlayer

NASA Astrophysics Data System (ADS)

Li, Jian-guang; Zhang, Zuo-liang; Zhang, Yu-biao; Shi, Xiu-wen; Wei, Jian

2017-06-01

The composite rock mass with weak interlayer is widely exist in engineering, and it’s essential to research the creep behavior which could cause stability problems of rock engineering and production accidents. However, due to it is difficult to take samples, the losses and damages in delivery and machining process, we always cannot get enough natural layered composite rock mass samples, so the indirect test method has been widely used. In this paper, we used ANSYS software (a General Finite Element software produced by American ANSYS, Inc) to carry out the numerical simulation based on the uniaxial compression creep experiments of artificial composite rock mass with weak interlayer, after experimental data fitted. The results show that the laws obtained by numerical simulations and experiments are consistent. Thus confirmed that carry out numerical simulation for the creep characteristics of rock mass with ANSYS software is feasible, and this method can also be extended to other underground engineering of simulate the weak intercalations.

The design and operational development of self-streamlining 2-dimensional flexible walled test sections. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Wolf, S. W. D.

1984-01-01

Self streamlining two dimensional flexible walled test sections eliminate the uncertainties found in data from conventional test sections particularly at transonic speeds. The test section sidewalls are rigid, while the floor and ceiling are flexible and are positioned to streamline shapes by a system of jacks, without reference to the model. The walls are therefore self streamlining. Data are taken from the model when the walls are good streamlines such that the inevitable residual wall induced interference is acceptably small and correctable. Successful two dimensional validation testing at low speeds has led to the development of a new transonic flexible walled test section. Tunnel setting times are minimized by the development of a rapid wall setting strategy coupled with on line computer control of wall shapes using motorized jacks. Two dimensional validation testing using symmetric and cambered aerofoils in the Mach number range up to about 0.85 where the walls are just supercritical, shows good agreement with reference data using small height-chord ratios between 1.5 and unity.

West Virginia peer exchange : streamlining highway safety improvement program project delivery.

DOT National Transportation Integrated Search

2015-01-01

The West Virginia Division of Highways (WV DOH) hosted a Peer Exchange to share information and experiences : for streamlining Highway Safety Improvement Program (HSIP) project delivery. The event was held September : 22 to 23, 2014 in Charleston, We...

The development of a self-streamlining flexible walled transonic test section

NASA Technical Reports Server (NTRS)

Goodyer, M. J.; Wolf, S. W. D.

1980-01-01

This design eliminates the uncertainties in data from conventional transonic test sections. Sidewalls are rigid, and the flexible floor and ceiling are positioned by motorized jacks controlled by on-line computer to minimize run times. The tunnel-computer combination is self-streamlining without reference to the model. Data is taken from the model only when the walls are good streamlines, and is corrected for the small, known but inevitable residual interferences. Two-dimensional validation testing in the Mach range up to about 0.85 where the walls are just supercritical shows good agreement with reference data using a height:chord ratio of 1.5. Techniques are under development to extend Mach number above 1. This work has demonstrated the feasibility of almost eliminating wall interferences, improving flow quality, and reducing power requirements or increasing Reynolds number. Extensions to three-dimensional testing are outlined.

Self streamlining wind tunnel: Further low speed testing and final design studies for the transonic facility

NASA Technical Reports Server (NTRS)

Wolf, S. W. D.

1977-01-01

Work has continued with the low speed self streamlining wind tunnel (SSWT) using the NACA 0012-64 airfoil in an effort to explain the discrepancies between the NASA Langley low turbulence pressure tunnel (LTPT) and SSWT results obtained with the airfoil stalled. Conventional wind tunnel corrections were applied to straight wall SSWT airfoil data, to illustrate the inadequacy of standard correction techniques in circumstances of high blockage. Also one SSWT test was re-run at different air speeds to investigate the effects of such changes on airfoil data and wall contours. Mechanical design analyses for the transonic self streamlining wind tunnel (TSWT) were completed by the application of theoretical airfoil flow field data to the elastic beam and streamline analysis. The control system for the transonic facility is outlined.

Novel diffusion tensor imaging technique reveals developmental streamline volume changes in the corticospinal tract associated with leg motor control.

PubMed

Kamson, David O; Juhász, Csaba; Chugani, Harry T; Jeong, Jeong-Won

2015-04-01

Diffusion tensor imaging (DTI) has expanded our knowledge of corticospinal tract (CST) anatomy and development. However, previous developmental DTI studies assessed the CST as a whole, overlooking potential differences in development of its components related to control of the upper and lower extremities. The present cross-sectional study investigated age-related changes, side and gender differences in streamline volume of the leg- and hand-related segments of the CST in children. DTI data of 31 children (1-14 years; mean age: 6±4 years; 17 girls) with normal conventional MRI were analyzed. Leg- and hand-related CST streamline volumes were quantified separately, using a recently validated novel tractography approach. CST streamline volumes on both sides were compared between genders and correlated with age. Higher absolute streamline volumes were found in the left leg-related CST compared to the right (p=0.001) without a gender effect (p=0.4), whereas no differences were found in the absolute hand-related CST volumes (p>0.4). CST leg-related streamline volumes, normalized to hemispheric white matter volumes, declined with age in the right hemisphere only (R=-.51; p=0.004). Absolute leg-related CST streamline volumes showed similar, but slightly weaker correlations. Hand-related absolute or normalized CST streamline volumes showed no age-related variations on either side. These results suggest differential development of CST segments controlling hand vs. leg movements. Asymmetric volume changes in the lower limb motor pathway may be secondary to gradually strengthening left hemispheric dominance and is consistent with previous data suggesting that footedness is a better predictor of hemispheric lateralization than handedness. Copyright © 2014 The Japanese Society of Child Neurology. Published by Elsevier B.V. All rights reserved.

Process to Produce Iron Nanoparticle Lunar Dust Simulant Composite

NASA Technical Reports Server (NTRS)

Hung, Ching-cheh; McNatt, Jeremiah

2010-01-01

A document discusses a method for producing nanophase iron lunar dust composite simulant by heating a mixture of carbon black and current lunar simulant types (mixed oxide including iron oxide) at a high temperature to reduce ionic iron into elemental iron. The product is a chemically modified lunar simulant that can be attracted by a magnet, and has a surface layer with an iron concentration that is increased during the reaction. The iron was found to be -iron and Fe3O4 nanoparticles. The simulant produced with this method contains iron nanoparticles not available previously, and they are stable in ambient air. These nanoparticles can be mass-produced simply.

METCAN simulation of candidate metal matrix composites for high temperature applications

NASA Technical Reports Server (NTRS)

Lee, Ho-Jun

1990-01-01

The METCAN (Metal Matrix Composite Analyzer) computer code is used to simulate the nonlinear behavior of select metal matrix composites in order to assess their potential for high temperature structural applications. Material properties for seven composites are generated at a fiber volume ratio of 0.33 for two bonding conditions (a perfect bond and a weak interphase case) at various temperatures. A comparison of the two bonding conditions studied shows a general reduction in value of all properties (except CTE) for the weak interphase case from the perfect bond case. However, in the weak interphase case, the residual stresses that develop are considerably less than those that form in the perfect bond case. Results of the computational simulation indicate that among the metal matrix composites examined, SiC/NiAl is the best candidate for high temperature applications at the given fiber volume ratio.

Eco-friendly streamlined process for sporopollenin exine capsule extraction

PubMed Central

Mundargi, Raghavendra C.; Potroz, Michael G.; Park, Jae Hyeon; Seo, Jeongeun; Tan, Ee-Lin; Lee, Jae Ho; Cho, Nam-Joon

2016-01-01

Sporopollenin exine capsules (SECs) extracted from Lycopodium clavatum spores are an attractive biomaterial possessing a highly robust structure suitable for microencapsulation strategies. Despite several decades of research into SEC extraction methods, the protocols commonly used for L. clavatum still entail processing with both alkaline and acidolysis steps at temperatures up to 180 °C and lasting up to 7 days. Herein, we demonstrate a significantly streamlined processing regimen, which indicates that much lower temperatures and processing durations can be used without alkaline lysis. By employing CHN elemental analysis, scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM), and dynamic image particle analysis (DIPA), the optimum conditions for L. clavatum SEC processing were determined to include 30 hours acidolysis at 70 °C without alkaline lysis. Extending these findings to proof-of-concept encapsulation studies, we further demonstrate that our SECs are able to achieve a loading of 0.170 ± 0.01 g BSA per 1 g SECs by vacuum-assisted loading. Taken together, our streamlined processing method and corresponding characterization of SECs provides important insights for the development of applications including drug delivery, cosmetics, personal care products, and foods. PMID:26818918

Eco-friendly streamlined process for sporopollenin exine capsule extraction

NASA Astrophysics Data System (ADS)

Mundargi, Raghavendra C.; Potroz, Michael G.; Park, Jae Hyeon; Seo, Jeongeun; Tan, Ee-Lin; Lee, Jae Ho; Cho, Nam-Joon

2016-01-01

Sporopollenin exine capsules (SECs) extracted from Lycopodium clavatum spores are an attractive biomaterial possessing a highly robust structure suitable for microencapsulation strategies. Despite several decades of research into SEC extraction methods, the protocols commonly used for L. clavatum still entail processing with both alkaline and acidolysis steps at temperatures up to 180 °C and lasting up to 7 days. Herein, we demonstrate a significantly streamlined processing regimen, which indicates that much lower temperatures and processing durations can be used without alkaline lysis. By employing CHN elemental analysis, scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM), and dynamic image particle analysis (DIPA), the optimum conditions for L. clavatum SEC processing were determined to include 30 hours acidolysis at 70 °C without alkaline lysis. Extending these findings to proof-of-concept encapsulation studies, we further demonstrate that our SECs are able to achieve a loading of 0.170 ± 0.01 g BSA per 1 g SECs by vacuum-assisted loading. Taken together, our streamlined processing method and corresponding characterization of SECs provides important insights for the development of applications including drug delivery, cosmetics, personal care products, and foods.

Stratified Flow Past a Hill: Dividing Streamline Concept Revisited

NASA Astrophysics Data System (ADS)

Leo, Laura S.; Thompson, Michael Y.; Di Sabatino, Silvana; Fernando, Harindra J. S.

2016-06-01

The Sheppard formula (Q J R Meteorol Soc 82:528-529, 1956) for the dividing streamline height H_s assumes a uniform velocity U_∞ and a constant buoyancy frequency N for the approach flow towards a mountain of height h, and takes the form H_s/h=( {1-F} ) , where F=U_{∞}/Nh. We extend this solution to a logarithmic approach-velocity profile with constant N. An analytical solution is obtained for H_s/h in terms of Lambert-W functions, which also suggests alternative scaling for H_s/h. A `modified' logarithmic velocity profile is proposed for stably stratified atmospheric boundary-layer flows. A field experiment designed to observe H_s is described, which utilized instrumentation from the spring field campaign of the Mountain Terrain Atmospheric Modeling and Observations (MATERHORN) Program. Multiple releases of smoke at F≈ 0.3-0.4 support the new formulation, notwithstanding the limited success of experiments due to logistical constraints. No dividing streamline is discerned for F≈ 10, since, if present, it is too close to the foothill. Flow separation and vortex shedding is observed in this case. The proposed modified logarithmic profile is in reasonable agreement with experimental observations.

Recognition of white matter bundles using local and global streamline-based registration and clustering.

PubMed

Garyfallidis, Eleftherios; Côté, Marc-Alexandre; Rheault, Francois; Sidhu, Jasmeen; Hau, Janice; Petit, Laurent; Fortin, David; Cunanne, Stephen; Descoteaux, Maxime

2018-04-15

Virtual dissection of diffusion MRI tractograms is cumbersome and needs extensive knowledge of white matter anatomy. This virtual dissection often requires several inclusion and exclusion regions-of-interest that make it a process that is very hard to reproduce across experts. Having automated tools that can extract white matter bundles for tract-based studies of large numbers of people is of great interest for neuroscience and neurosurgical planning. The purpose of our proposed method, named RecoBundles, is to segment white matter bundles and make virtual dissection easier to perform. This can help explore large tractograms from multiple persons directly in their native space. RecoBundles leverages latest state-of-the-art streamline-based registration and clustering to recognize and extract bundles using prior bundle models. RecoBundles uses bundle models as shape priors for detecting similar streamlines and bundles in tractograms. RecoBundles is 100% streamline-based, is efficient to work with millions of streamlines and, most importantly, is robust and adaptive to incomplete data and bundles with missing components. It is also robust to pathological brains with tumors and deformations. We evaluated our results using multiple bundles and showed that RecoBundles is in good agreement with the neuroanatomical experts and generally produced more dense bundles. Across all the different experiments reported in this paper, RecoBundles was able to identify the core parts of the bundles, independently from tractography type (deterministic or probabilistic) or size. Thus, RecoBundles can be a valuable method for exploring tractograms and facilitating tractometry studies. Copyright © 2017 Elsevier Inc. All rights reserved.

GIS for environmental stewardship and streamlining: an overview of state DOT practices

DOT National Transportation Integrated Search

2005-01-31

The Federal Highway Administration (FHWA) supports the adoption and development of Geographic Information System (GIS) technologies to promote environmental streamlining and stewardship (referred to as GIS4EST). While several States have already appl...

Methodology for the Design of Streamline-Traced External-Compression Supersonic Inlets

NASA Technical Reports Server (NTRS)

Slater, John W.

2014-01-01

A design methodology based on streamline-tracing is discussed for the design of external-compression, supersonic inlets for flight below Mach 2.0. The methodology establishes a supersonic compression surface and capture cross-section by tracing streamlines through an axisymmetric Busemann flowfield. The compression system of shock and Mach waves is altered through modifications to the leading edge and shoulder of the compression surface. An external terminal shock is established to create subsonic flow which is diffused in the subsonic diffuser. The design methodology was implemented into the SUPIN inlet design tool. SUPIN uses specified design factors to design the inlets and computes the inlet performance, which includes the flow rates, total pressure recovery, and wave drag. A design study was conducted using SUPIN and the Wind-US computational fluid dynamics code to design and analyze the properties of two streamline-traced, external-compression (STEX) supersonic inlets for Mach 1.6 freestream conditions. The STEX inlets were compared to axisymmetric pitot, two-dimensional, and axisymmetric spike inlets. The STEX inlets had slightly lower total pressure recovery and higher levels of total pressure distortion than the axisymmetric spike inlet. The cowl wave drag coefficients of the STEX inlets were 20% of those for the axisymmetric spike inlet. The STEX inlets had external sound pressures that were 37% of those of the axisymmetric spike inlet, which may result in lower adverse sonic boom characteristics. The flexibility of the shape of the capture cross-section may result in benefits for the integration of STEX inlets with aircraft.

Computational simulation of matrix micro-slip bands in SiC/Ti-15 composite

NASA Technical Reports Server (NTRS)

Mital, S. K.; Lee, H.-J.; Murthy, P. L. N.; Chamis, C. C.

1992-01-01

Computational simulation procedures are used to identify the key deformation mechanisms for (0)(sub 8) and (90)(sub 8) SiC/Ti-15 metal matrix composites. The computational simulation procedures employed consist of a three-dimensional finite-element analysis and a micromechanics based computer code METCAN. The interphase properties used in the analysis have been calibrated using the METCAN computer code with the (90)(sub 8) experimental stress-strain curve. Results of simulation show that although shear stresses are sufficiently high to cause the formation of some slip bands in the matrix concentrated mostly near the fibers, the nonlinearity in the composite stress-strain curve in the case of (90)(sub 8) composite is dominated by interfacial damage, such as microcracks and debonding rather than microplasticity. The stress-strain curve for (0)(sub 8) composite is largely controlled by the fibers and shows only slight nonlinearity at higher strain levels that could be the result of matrix microplasticity.

Surface Roughness of Composite Resins after Simulated Toothbrushing with Different Dentifrices.

PubMed

Monteiro, Bruna; Spohr, Ana Maria

2015-07-01

The aim of the study was to evaluate, in vitro, the surface roughness of two composite resins submitted to simulated toothbrushing with three different dentifrices. Totally, 36 samples of Z350XT and 36 samples of Empress Direct were built and randomly divided into three groups (n = 12) according to the dentifrice used (Oral-B Pro-Health Whitening [OBW], Colgate Sensitive Pro-Relief [CS], Colgate Total Clean Mint 12 [CT12]). The samples were submitted to 5,000, 10,000 or 20,000 cycles of simulated toothbrushing. After each simulated period, the surface roughness of the samples was measured using a roughness tester. According to three-way analysis of variance, dentifrice (P = 0.044) and brushing time (P = 0.000) were significant. The composite resin was not significant (P = 0.381) and the interaction among the factors was not significant (P > 0.05). The mean values of the surface roughness (µm) followed by the same letter represent no statistical difference by Tukey's post-hoc test (P <0.05): Dentifrice: CT12 = 0.269(a); CS Pro- Relief = 0.300(ab); OBW = 0.390(b). Brushing time: Baseline = 0,046ª; 5,000 cycles = 0.297(b); 10,000 cycles = 0.354(b); 20,000 cycles = 0.584(c). Z350 XT and Empress Direct presented similar surface roughness after all cycles of simulated toothbrushing. The higher the brushing time, the higher the surface roughness of composite resins. The dentifrice OBW caused a higher surface roughness in both composite resins.

Surface Roughness of Composite Resins after Simulated Toothbrushing with Different Dentifrices

PubMed Central

Monteiro, Bruna; Spohr, Ana Maria

2015-01-01

Background: The aim of the study was to evaluate, in vitro, the surface roughness of two composite resins submitted to simulated toothbrushing with three different dentifrices. Materials and Methods: Totally, 36 samples of Z350XT and 36 samples of Empress Direct were built and randomly divided into three groups (n = 12) according to the dentifrice used (Oral-B Pro-Health Whitening [OBW], Colgate Sensitive Pro-Relief [CS], Colgate Total Clean Mint 12 [CT12]). The samples were submitted to 5,000, 10,000 or 20,000 cycles of simulated toothbrushing. After each simulated period, the surface roughness of the samples was measured using a roughness tester. Results: According to three-way analysis of variance, dentifrice (P = 0.044) and brushing time (P = 0.000) were significant. The composite resin was not significant (P = 0.381) and the interaction among the factors was not significant (P > 0.05). The mean values of the surface roughness (µm) followed by the same letter represent no statistical difference by Tukey's post-hoc test (P <0.05): Dentifrice: CT12 = 0.269a; CS Pro- Relief = 0.300ab; OBW = 0.390b. Brushing time: Baseline = 0,046ª; 5,000 cycles = 0.297b; 10,000 cycles = 0.354b; 20,000 cycles = 0.584c. Conclusion: Z350 XT and Empress Direct presented similar surface roughness after all cycles of simulated toothbrushing. The higher the brushing time, the higher the surface roughness of composite resins. The dentifrice OBW caused a higher surface roughness in both composite resins. PMID:26229362

Numerical Simulation of Delamination Growth in Composite Materials

NASA Technical Reports Server (NTRS)

Camanho, P. P.; Davila, C. G.; Ambur, D. R.

2001-01-01

The use of decohesion elements for the simulation of delamination in composite materials is reviewed. The test methods available to measure the interfacial fracture toughness used in the formulation of decohesion elements are described initially. After a brief presentation of the virtual crack closure technique, the technique most widely used to simulate delamination growth, the formulation of interfacial decohesion elements is described. Problems related with decohesion element constitutive equations, mixed-mode crack growth, element numerical integration and solution procedures are discussed. Based on these investigations, it is concluded that the use of interfacial decohesion elements is a promising technique that avoids the need for a pre-existing crack and pre-defined crack paths, and that these elements can be used to simulate both delamination onset and growth.

The erosion of streamlined islands, longitudinal grooves and scour marks: Implications to the origin of the Martian outflow channels

NASA Technical Reports Server (NTRS)

Komar, P. D.

1984-01-01

The diversity of proposed origins for large Martian outflow channels results from the differing interpretations given to the landforms associated with the outflow channels. In an attempt to help limit the possible mechanisms of channel erosion, detailed studies of three of the channel features were done; the streamlined islands, longitudinal grooves and scour marks. This examination involved a comparison of the martian streamlined islands with various streamlined landforms on Earth including those found in the Channel Scabland in large rivers, glacial drumlins, and desert yardangs. The comparisons included statistical analyses of the landform lengths versus widths and positions of maximum width, and an examination of the degree of shape agreement with the geometric lemniscate which was in turn demonstrated to correspond closely with true airfoil shapes. The analyses showed that the shapes of the martian islands correspond closely to the streamlined islands in rivers and the Channel Scabland land. Drumlins show a much smaller correlation. Erosional rock islands formed by glaciers are very much different in shape.

Self streamlining wind tunnel: Further low speed testing and final design studies for the transonic facility

NASA Technical Reports Server (NTRS)

Wolf, S. W. D.

1978-01-01

Work was continued with the low speed self streamlining wind tunnel (SSWT) using the NACA 0012-64 airfoil in an effort to explain the discrepancies between the NASA Langley low turbulence pressure tunnel (LTPT) and SSWT results obtained with the airfoil stalled. Conventional wind tunnel corrections were applied to straight wall SSWT airfoil data, to illustrate the inadequacy of standard correction techniques in circumstances of high blockage. Also one SSWT test was re-run at different air speeds to investigate the effects of such changes (perhaps through changes in Reynold's number and freestream turbulence levels) on airfoil data and wall contours. Mechanical design analyses for the transonic self-streamlining wind tunnel (TSWT) were completed by the application of theoretical airfoil flow field data to the elastic beam and streamline analysis. The control system for the transonic facility, which will eventually allow on-line computer operation of the wind tunnel, was outlined.

Streamline Basal Application of Herbicide for Small-Stem Hardwood Control

Treesearch

James H. Miller

1990-01-01

Abstract. The effectiveness of low-volume b a s a lapplication of herbicide - "streamline" application - was evaluated on 25 hardwood species and loblolly pine. Test mixtures were step-wise rates of Garlon 4 mixed in diesel fuel with a penatrant added. Most comparisons tested 1O%, 20%, and 30% mixtures of Garlon 4, while tests with...

Multi-scale simulations of apatite-collagen composites: from molecules to materials

NASA Astrophysics Data System (ADS)

Zahn, Dirk

2017-03-01

We review scale-bridging simulation studies for the exploration of atomicto-meso scale processes that account for the unique structure and mechanic properties of apatite-protein composites. As the atomic structure and composition of such complex biocomposites only partially is known, the first part (i) of our modelling studies is dedicated to realistic crystal nucleation scenarios of inorganic-organic composites. Starting from the association of single ions, recent insights range from the mechanisms of motif formation, ripening reactions and the self-organization of nanocrystals, including their interplay with growth-controlling molecular moieties. On this basis, (ii) reliable building rules for unprejudiced scale-up models can be derived to model bulk materials. This is exemplified for (enamel-like) apatite-protein composites, encompassing up to 106 atom models to provide a realistic account of the 10 nm length scale, whilst model coarsening is used to reach μm length scales. On this basis, a series of deformation and fracture simulation studies were performed and helped to rationalize biocomposite hardness, plasticity, toughness, self-healing and fracture mechanisms. Complementing experimental work, these modelling studies provide particularly detailed insights into the relation of hierarchical composite structure and favorable mechanical properties.

Degradation of experimental composite materials and in vitro wear simulation

NASA Astrophysics Data System (ADS)

Givan, Daniel Allen

2001-12-01

The material, mechanical, and clinical aspects of surface degradation of resin composite dental restorative materials by in vitro wear simulation continues to be an area of active research. To investigate wear mechanisms, a series of experimental resin composites with variable and controlled filler particle shape and loading were studied by in vitro wear simulation. The current investigation utilized a simulation that isolated the wear environment, entrapped high and low modulus debris, and evaluated the process including machine and fluid flow dynamics. The degradation was significantly affected by filler particle shape and less by particle loading. The spherical particle composites demonstrated wear loss profiles suggesting an optimized filler loading may exist. This was also demonstrated by the trends in the mechanical properties. Very little difference in magnitude was noted for the wear of irregular particle composites as a function of particulate size; and as a group they were more wear resistant than spherical particle composites. This was the result of different mechanisms of wear that were correlated with the three-dimensional particle shape. The abrasive effects of the aggregate particles and the polymeric stabilization of the irregular shape versus the destabilization and "plucking" of the spherical particles resulted in an unprotected matrix that accounted for significantly greater wear of spherical composite. A model and analysis was developed to explain the events associated with the progressive material wear loss. The initial phase was explained by fatigue-assisted microcracking and loss of material segments in a zone of high stress immediately beneath a point of high stress contact. The early phase was characterized by the development of a small facet primarily by fatigue-assisted microcracking. Although the translation effects were minimal, some three-body and initial two-body wear events were also present. In the late phases, the abrasive effects

Tensile strength of simulated and welded butt joints in W-Cu composite sheet

NASA Technical Reports Server (NTRS)

Moore, Thomas J.; Watson, Gordon K.

1994-01-01

The weldability of W-Cu composite sheet was investigated using simulated and welded joints. The welded joints were produced in a vacuum hot press. Tensile test results showed that simulated joints can provide strength and failure mode data which can be used in joint design for actual weldments. Although all of the welded joints had flaws, a number of these joints were as strong as the W-Cu composite base material.

Guided waves in anisotropic and quasi-isotropic aerospace composites: three-dimensional simulation and experiment.

PubMed

Leckey, Cara A C; Rogge, Matthew D; Raymond Parker, F

2014-01-01

Three-dimensional (3D) elastic wave simulations can be used to investigate and optimize nondestructive evaluation (NDE) and structural health monitoring (SHM) ultrasonic damage detection techniques for aerospace materials. 3D anisotropic elastodynamic finite integration technique (EFIT) has been implemented for ultrasonic waves in carbon fiber reinforced polymer (CFRP) composite laminates. This paper describes 3D EFIT simulations of guided wave propagation in undamaged and damaged anisotropic and quasi-isotropic composite plates. Comparisons are made between simulations of guided waves in undamaged anisotropic composite plates and both experimental laser Doppler vibrometer (LDV) wavefield data and dispersion curves. Time domain and wavenumber domain comparisons are described. Wave interaction with complex geometry delamination damage is then simulated to investigate how simulation tools incorporating realistic damage geometries can aid in the understanding of wave interaction with CFRP damage. In order to move beyond simplistic assumptions of damage geometry, volumetric delamination data acquired via X-ray microfocus computed tomography is directly incorporated into the simulation. Simulated guided wave interaction with the complex geometry delamination is compared to experimental LDV time domain data and 3D wave interaction with the volumetric damage is discussed. Published by Elsevier B.V.

Virtual Genomes in Flux: An Interplay of Neutrality and Adaptability Explains Genome Expansion and Streamlining

PubMed Central

Cuypers, Thomas D.; Hogeweg, Paulien

2012-01-01

The picture that emerges from phylogenetic gene content reconstructions is that genomes evolve in a dynamic pattern of rapid expansion and gradual streamlining. Ancestral organisms have been estimated to possess remarkably rich gene complements, although gene loss is a driving force in subsequent lineage adaptation and diversification. Here, we study genome dynamics in a model of virtual cells evolving to maintain homeostasis. We observe a pattern of an initial rapid expansion of the genome and a prolonged phase of mutational load reduction. Generally, load reduction is achieved by the deletion of redundant genes, generating a streamlining pattern. Load reduction can also occur as a result of the generation of highly neutral genomic regions. These regions can expand and contract in a neutral fashion. Our study suggests that genome expansion and streamlining are generic patterns of evolving systems. We propose that the complex genotype to phenotype mapping in virtual cells as well as in their biological counterparts drives genome size dynamics, due to an emerging interplay between adaptation, neutrality, and evolvability. PMID:22234601

Damage properties simulations of self-healing composites.

PubMed

Chen, Cheng; Ji, Hongwei; Wang, Huaiwen

2013-10-01

Self-healing materials are inspired by biological systems in which damage triggers an autonomic healing response. The damage properties of a self-healing polymer composite were investigated by numerical simulation in this paper. Unit cell models with single-edge centered crack and single-edge off-centered crack were employed to investigate the damage initiation and crack evolution by the extended finite element method (XFEM) modeling. The effect of microcapsule's Young's modulus on composites was investigated. Result indicates the microcapsule's Young's modulus has little effect on the unit cell's carrying capacity. It was found that during the crack propagation process, its direction is attracted toward the microcapsules, which makes it helpful for the microcapsules to be ruptured by the propagating crack fronts resulting in release of the healing agent into the cracks by capillary action.

Simulation Based Low-Cost Composite Process Development at the US Air Force Research Laboratory

NASA Technical Reports Server (NTRS)

Rice, Brian P.; Lee, C. William; Curliss, David B.

2003-01-01

Low-cost composite research in the US Air Force Research Laboratory, Materials and Manufacturing Directorate, Organic Matrix Composites Branch has focused on the theme of affordable performance. Practically, this means that we use a very broad view when considering the affordability of composites. Factors such as material costs, labor costs, recurring and nonrecurring manufacturing costs are balanced against performance to arrive at the relative affordability vs. performance measure of merit. The research efforts discussed here are two projects focused on affordable processing of composites. The first topic is the use of a neural network scheme to model cure reaction kinetics, then utilize the kinetics coupled with simple heat transport models to predict, in real-time, future exotherms and control them. The neural network scheme is demonstrated to be very robust and a much more efficient method that mechanistic cure modeling approach. This enables very practical low-cost processing of thick composite parts. The second project is liquid composite molding (LCM) process simulation. LCM processing of large 3D integrated composite parts has been demonstrated to be a very cost effective way to produce large integrated aerospace components specific examples of LCM processes are resin transfer molding (RTM), vacuum assisted resin transfer molding (VARTM), and other similar approaches. LCM process simulation is a critical part of developing an LCM process approach. Flow simulation enables the development of the most robust approach to introducing resin into complex preforms. Furthermore, LCM simulation can be used in conjunction with flow front sensors to control the LCM process in real-time to account for preform or resin variability.

Probabilistic Simulation of Progressive Fracture in Bolted-Joint Composite Laminates

NASA Technical Reports Server (NTRS)

Minnetyan, L.; Singhal, S. N.; Chamis, C. C.

1996-01-01

This report describes computational methods to probabilistically simulate fracture in bolted composite structures. An innovative approach that is independent of stress intensity factors and fracture toughness was used to simulate progressive fracture. The effect of design variable uncertainties on structural damage was also quantified. A fast probability integrator assessed the scatter in the composite structure response before and after damage. Then the sensitivity of the response to design variables was computed. General-purpose methods, which are applicable to bolted joints in all types of structures and in all fracture processes-from damage initiation to unstable propagation and global structure collapse-were used. These methods were demonstrated for a bolted joint of a polymer matrix composite panel under edge loads. The effects of the fabrication process were included in the simulation of damage in the bolted panel. Results showed that the most effective way to reduce end displacement at fracture is to control both the load and the ply thickness. The cumulative probability for longitudinal stress in all plies was most sensitive to the load; in the 0 deg. plies it was very sensitive to ply thickness. The cumulative probability for transverse stress was most sensitive to the matrix coefficient of thermal expansion. In addition, fiber volume ratio and fiber transverse modulus both contributed significantly to the cumulative probability for the transverse stresses in all the plies.

On Periodic Water Waves with Coriolis Effects and Isobaric Streamlines

NASA Astrophysics Data System (ADS)

Matioc, Anca-Voichita; Matioc, Bogdan-Vasile

2012-10-01

In this paper we prove that solutions of the f-plane approximation for equatorial geophysical deep water waves, which have the property that the pressure is constant along the streamlines and do not possess stagnation points, are Gerstner-type waves. Furthermore, for waves traveling over a flat bed, we prove that there are only laminar flow solutions with these properties.

Equivalent Young's modulus of composite resin for simulation of stress during dental restoration.

PubMed

Park, Jung-Hoon; Choi, Nak-Sam

2017-02-01

For shrinkage stress simulation in dental restoration, the elastic properties of composite resins should be acquired beforehand. This study proposes a formula to measure the equivalent Young's modulus of a composite resin through a calculation scheme of the shrinkage stress in dental restoration. Two types of composite resins remarkably different in the polymerization shrinkage strain were used for experimental verification: the methacrylate-type (Clearfil AP-X) and the silorane-type (Filtek P90). The linear shrinkage strains of the composite resins were gained through the bonded disk method. A formula to calculate the equivalent Young's moduli of composite resin was derived on the basis of the restored ring substrate. Equivalent Young's moduli were measured for the two types of composite resins through the formula. Those values were applied as input to a finite element analysis (FEA) for validation of the calculated shrinkage stress. Both of the measured moduli through the formula were appropriate for stress simulation of dental restoration in that the shrinkage stresses calculated by the FEA were in good agreement within 3.5% with the experimental values. The concept of equivalent Young's modulus so measured could be applied for stress simulation of 2D and 3D dental restoration. Copyright © 2016 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Streamlining the Online Course Development Process by Using Project Management Tools

ERIC Educational Resources Information Center

Abdous, M'hammed; He, Wu

2008-01-01

Managing the design and production of online courses is challenging. Insufficient instructional design and inefficient management often lead to issues such as poor course quality and course delivery delays. In an effort to facilitate, streamline, and improve the overall design and production of online courses, this article discusses how we…

Optimal fabrication processes for unidirectional metal-matrix composites: A computational simulation

NASA Technical Reports Server (NTRS)

Saravanos, D. A.; Murthy, P. L. N.; Morel, M.

1990-01-01

A method is proposed for optimizing the fabrication process of unidirectional metal matrix composites. The temperature and pressure histories are optimized such that the residual microstresses of the composite at the end of the fabrication process are minimized and the material integrity throughout the process is ensured. The response of the composite during the fabrication is simulated based on a nonlinear micromechanics theory. The optimal fabrication problem is formulated and solved with non-linear programming. Application cases regarding the optimization of the fabrication cool-down phases of unidirectional ultra-high modulus graphite/copper and silicon carbide/titanium composites are presented.

Optimal fabrication processes for unidirectional metal-matrix composites - A computational simulation

NASA Technical Reports Server (NTRS)

Saravanos, D. A.; Murthy, P. L. N.; Morel, M.

1990-01-01

A method is proposed for optimizing the fabrication process of unidirectional metal matrix composites. The temperature and pressure histories are optimized such that the residual microstresses of the composite at the end of the fabrication process are minimized and the material integrity throughout the process is ensured. The response of the composite during the fabrication is simulated based on a nonlinear micromechanics theory. The optimal fabrication problem is formulated and solved with nonlinear programming. Application cases regarding the optimization of the fabrication cool-down phases of unidirectional ultra-high modulus graphite/copper and silicon carbide/titanium composites are presented.

Global two dimensional chemistry model and simulation of atmospheric chemical composition

NASA Astrophysics Data System (ADS)

Zhang, Renjian; Wang, Mingxing; Zeng, Qingcun

2000-03-01

A global two-dimensional zonally averaged chemistry model is developed to study the chemi-cal composition of atmosphere. The region of the model is from 90°S to 90°N and from the ground to the altitude of 20 km with a resolution of 5° x 1 km. The wind field is residual circulation calcu-lated from diabatic rate. 34 species and 104 chemical and photochemical reactions are considered in the model. The sources of CH4, CO and NOx, which are divided into seasonal sources and non-seasonal sources, are parameterized as a function of latitude and time. The chemical composi-tion of atmosphere was simulated with emission level of CH4, CO and NOx in 1990. The results are compared with observations and other model results, showing that the model is successful to simu-late the atmospheric chemical composition and distribution of CH4.

Exploratory study of in-plane streamline curvature effects on a turbulent boundary layer at a Mach number of 3

NASA Technical Reports Server (NTRS)

Bogdonoff, Seymour M.

1991-01-01

This report on a program to study in-plane streamline curvature effects in a turbulent boundary layer at a Mach number of 3. The original proposal, for a 3-year program to explore in-plane streamline curvature effects on a supersonic turbulent boundary layer using three-dimensional pressure fields generated by fins and wall geometry, ended after one year. The purpose of these tests was to compare these streamline curvature effects to the more classical two-dimensional curvature generated by wall shape and imposed pressure gradients, previously considered primarily in a plane normal to the floor. The studies were carried out in the Mach number of 3, 8 x 8 inch High Reynolds Number Supersonic Tunnel. The usual surface visualization and mean wall static pressures were supplemented by the use of many small high frequency wall static pressure gauges (Kulites) to get some indication of the amplification of boundary layer disturbances by the in-plane streamline curvature caused by the three-dimensional pressure fields imposed on the boundary layer.

Simulation of Thermographic Responses of Delaminations in Composites with Quadrupole Method

NASA Technical Reports Server (NTRS)

Winfree, William P.; Zalameda, Joseph N.; Howell, Patricia A.; Cramer, K. Elliott

2016-01-01

The application of the quadrupole method for simulating thermal responses of delaminations in carbon fiber reinforced epoxy composites materials is presented. The method solves for the flux at the interface containing the delamination. From the interface flux, the temperature at the surface is calculated. While the results presented are for single sided measurements, with ash heating, expansion of the technique to arbitrary temporal flux heating or through transmission measurements is simple. The quadrupole method is shown to have two distinct advantages relative to finite element or finite difference techniques. First, it is straight forward to incorporate arbitrary shaped delaminations into the simulation. Second, the quadrupole method enables calculation of the thermal response at only the times of interest. This, combined with a significant reduction in the number of degrees of freedom for the same simulation quality, results in a reduction of the computation time by at least an order of magnitude. Therefore, it is a more viable technique for model based inversion of thermographic data. Results for simulations of delaminations in composites are presented and compared to measurements and finite element method results.

Molecular dynamics simulations of AP/HMX composite with a modified force field.

PubMed

Zhu, Wei; Wang, Xijun; Xiao, Jijun; Zhu, Weihua; Sun, Huai; Xiao, Heming

2009-08-15

An all-atom force field for ammonium perchlorate (AP) is developed with the framework of pcff force field. The structural parameters of AP obtained with the modified force field are in good agreement with experimental values. Molecular dynamics (MD) simulations have been performed to investigate AP/HMX (1,3,5,7-tetranitro-1,3,5,7-tetrazocane) composite at different temperatures. The binding energies, thermal expansion coefficient, and the trigger bond lengths of HMX in the AP/HMX composite have been obtained. The binding energies of the system increase slightly with temperature increasing, peak at 245K, and then gradually decrease. The volume thermal expansion coefficient of the AP/HMX composite has been derived from the volume variation with temperature. As the temperature rises, the maximal lengths of the trigger bond N-NO(2) of HMX increase gradually. The simulated results indicate that the maximal length of trigger bond can be used as a criterion for judging the sensitivity of energetic composite.

Simulating the Impact Response of Composite Airframe Components

NASA Technical Reports Server (NTRS)

Jackson, Karen E.; Littell, Justin D.; Fasanella, Edwin L.

2014-01-01

In 2010, NASA Langley Research Center obtained residual hardware from the US Army's Survivable Affordable Repairable Airframe Program (SARAP). The hardware consisted of a composite fuselage section that was representative of the center section of a Black Hawk helicopter. The section was fabricated by Sikorsky Aircraft Corporation and designated the Test Validation Article (TVA). The TVA was subjected to a vertical drop test in 2008 to evaluate a tilting roof concept to limit the intrusion of overhead mass items, such as the rotor transmission, into the fuselage cabin. As a result of the 2008 test, damage to the hardware was limited primarily to the roof. Consequently, when the post-test article was obtained in 2010, the roof area was removed and the remaining structure was cut into six different types of test specimens including: (1) tension and compression coupons for material property characterization, (2) I-beam sections, (3) T-sections, (4) cruciform sections, (5) a large subfloor section, and (6) a forward framed fuselage section. In 2011, NASA and Sikorsky entered into a cooperative research agreement to study the impact responses of composite airframe structures and to evaluate the capabilities of the explicit transient dynamic finite element code, LS-DYNA®, to simulate these responses including damage initiation and progressive failure. Finite element models of the composite specimens were developed and impact simulations were performed. The properties of the composite material were represented using both a progressive in-plane damage model (Mat 54) and a continuum damage mechanics model (Mat 58) in LS-DYNA. This paper provides test-analysis comparisons of time history responses and the location and type of damage for representative I-beam, T-section, and cruciform section components.

Surface waves with high angular momentum: leakage from remote caustics, and tightly coiled streamlines

NASA Astrophysics Data System (ADS)

Berry, M. V.

2018-07-01

Outgoing cylindrical waves scattered by a disk, or emerging from a source inside it, are represented by Hankel functions of order m. For large m, these waves decay rapidly outside the disk and resemble radially evanescent surface waves travelling around it. But they eventually leak weakly away, in a manner described accurately by the asymptotics of the Hankel function. The transition occurs at radial distance ∣m∣ (in wavelength units), which constitutes a circular caustic from which the radiation leaking out, described by the streamlines, appears to issue tangentially. In the evanescent region, the streamlines form spirals, whose windings get exponentially closer nearer the disk. These insights are intended to help graduate students demystify mathematics associated with scattering theory.

Accurate Simulation of Acoustic Emission Sources in Composite Plates

NASA Technical Reports Server (NTRS)

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

1994-01-01

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

Molecular dynamics simulation of diffusion of gases in a carbon-nanotube-polymer composite

NASA Astrophysics Data System (ADS)

Lim, Seong Y.; Sahimi, Muhammad; Tsotsis, Theodore T.; Kim, Nayong

2007-07-01

Extensive molecular dynamics (MD) simulations were carried out to compute the solubilities and self-diffusivities of CO2 and CH4 in amorphous polyetherimide (PEI) and mixed-matrix PEI generated by inserting single-walled carbon nanotubes into the polymer. Atomistic models of PEI and its composites were generated using energy minimizations, MD simulations, and the polymer-consistent force field. Two types of polymer composite were generated by inserting (7,0) and (12,0) zigzag carbon nanotubes into the PEI structure. The morphologies of PEI and its composites were characterized by their densities, radial distribution functions, and the accessible free volumes, which were computed with probe molecules of different sizes. The distributions of the cavity volumes were computed using the Voronoi tessellation method. The computed self-diffusivities of the gases in the polymer composites are much larger than those in pure PEI. We find, however, that the increase is not due to diffusion of the gases through the nanotubes which have smooth energy surfaces and, therefore, provide fast transport paths. Instead, the MD simulations indicate a squeezing effect of the nanotubes on the polymer matrix that changes the composite polymers’ free-volume distributions and makes them more sharply peaked. The presence of nanotubes also creates several cavities with large volumes that give rise to larger diffusivities in the polymer composites. This effect is due to the repulsive interactions between the polymer and the nanotubes. The solubilities of the gases in the polymer composites are also larger than those in pure PEI, hence indicating larger gas permeabilities for mixed-matrix PEI than PEI itself.

Athabasca Vallis Streamlined 'Islands'

NASA Technical Reports Server (NTRS)

2002-01-01

MGS MOC Release No. MOC2-322, 12 December 2002

Tremendous floods carved these tear drop-shaped landforms in Athabasca Vallis in the Cerberus region, south of the Elysium volcanoes. The orientation of the streamlined forms indicate that the fluid flowed from the right/upper right toward the left/lower left (from the northeast to the southwest). Similar features occur in central and eastern Washington in the northwestern United States. The examples in Washington formed when massive amounts of water rushed across the landscape, scouring a 'channeled scabland' during the last Ice Age, roughly 12,000-13,000 years ago. The features on Mars are much older; while the absolute age cannot be determined, the small impact craters with rayed ejecta patterns on the flood surfaces indicate it must be much, much older than the flood landscape in Washington. This is a mosaic of six Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) images acquired in 1999 through 2002. Illumination is from the left. The mosaic covers an area 11.9 km (7.4 mi) by 13.0 km (8.1 mi). The full-size mosaic has a resolution of 4 meters (13 ft) per pixel.

Vortex Generators in a Streamline-Traced, External-Compression Supersonic Inlet

NASA Technical Reports Server (NTRS)

Baydar, Ezgihan; Lu, Frank K.; Slater, John W.; Trefny, Charles J.

2017-01-01

Vortex generators within a streamline-traced, external-compression supersonic inlet for Mach 1.66 were investigated to determine their ability to increase total pressure recovery and reduce total pressure distortion. The vortex generators studied were rectangular vanes arranged in counter-rotating and co-rotating arrays. The vane geometric factors of interest included height, length, spacing, angle-of-incidence, and positions upstream and downstream of the inlet terminal shock. The flow through the inlet was simulated numerically through the solution of the steady-state, Reynolds-averaged Navier-Stokes equations on multi-block, structured grids using the Wind-US flow solver. The vanes were simulated using a vortex generator model. The inlet performance was characterized by the inlet total pressure recovery and the radial and circumferential total pressure distortion indices at the engine face. Design of experiments and statistical analysis methods were applied to quantify the effect of the geometric factors of the vanes and search for optimal vane arrays. Co-rotating vane arrays with negative angles-of-incidence positioned on the supersonic diffuser were effective in sweeping low-momentum flow from the top toward the sides of the subsonic diffuser. This distributed the low-momentum flow more evenly about the circumference of the subsonic diffuser and reduced distortion. Co-rotating vane arrays with negative angles-of-incidence or counter-rotating vane arrays positioned downstream of the terminal shock were effective in mixing higher-momentum flow with lower-momentum flow to increase recovery and decrease distortion. A strategy of combining a co-rotating vane array on the supersonic diffuser with a counter-rotating vane array on the subsonic diffuser was effective in increasing recovery and reducing distortion.

Honest broker protocol streamlines research access to data while safeguarding patient privacy.

PubMed

Silvey, Scott A; Silvey, Scott Andrew; Schulte, Janet; Smaltz, Detlev H; Smaltz, Detlev Herb; Kamal, Jyoti

2008-11-06

At Ohio State University Medical Center, The Honest Broker Protocol provides a streamlined mechanism whereby investigators can obtain de-identified clinical data for non-FDA research without having to invest the significant time and effort necessary to craft a formalized protocol for IRB approval.

The role of streamline curvature in sand dune dynamics: evidence from field and wind tunnel measurements

NASA Astrophysics Data System (ADS)

Wiggs, Giles F. S.; Livingstone, Ian; Warren, Andrew

1996-09-01

Field measurements on an unvegetated, 10 m high barchan dune in Oman are compared with measurements over a 1:200 scale fixed model in a wind tunnel. Both the field and wind tunnel data demonstrate similar patterns of wind and shear velocity over the dune, confirming significant flow deceleration upwind of and at the toe of the dune, acceleration of flow up the windward slope, and deceleration between the crest and brink. This pattern, including the widely reported upwind reduction in shear velocity, reflects observations of previous studies. Such a reduction in shear velocity upwind of the dune should result in a reduction in sand transport and subsequent sand deposition. This is not observed in the field. Wind tunnel modelling using a near-surface pulse-wire probe suggests that the field method of shear velocity derivation is inadequate. The wind tunnel results exhibit no reduction in shear velocity upwind of or at the toe of the dune. Evidence provided by Reynolds stress profiles and turbulence intensities measured in the wind tunnel suggest that this maintenance of upwind shear stress may be a result of concave (unstable) streamline curvature. These additional surface stresses are not recorded by the techniques used in the field measurements. Using the occurrence of streamline curvature as a starting point, a new 2-D model of dune dynamics is deduced. This model relies on the establishment of an equilibrium between windward slope morphology, surface stresses induced by streamline curvature, and streamwise acceleration. Adopting the criteria that concave streamline curvature and streamwise acceleration both increase surface shear stress, whereas convex streamline curvature and deceleration have the opposite effect, the relationships between form and process are investigated in each of three morphologically distinct zones: the upwind interdune and concave toe region of the dune, the convex portion of the windward slope, and the crest-brink region. The

Simulation of guided-wave ultrasound propagation in composite laminates: Benchmark comparisons of numerical codes and experiment.

PubMed

Leckey, Cara A C; Wheeler, Kevin R; Hafiychuk, Vasyl N; Hafiychuk, Halyna; Timuçin, Doğan A

2018-03-01

Ultrasonic wave methods constitute the leading physical mechanism for nondestructive evaluation (NDE) and structural health monitoring (SHM) of solid composite materials, such as carbon fiber reinforced polymer (CFRP) laminates. Computational models of ultrasonic wave excitation, propagation, and scattering in CFRP composites can be extremely valuable in designing practicable NDE and SHM hardware, software, and methodologies that accomplish the desired accuracy, reliability, efficiency, and coverage. The development and application of ultrasonic simulation approaches for composite materials is an active area of research in the field of NDE. This paper presents comparisons of guided wave simulations for CFRP composites implemented using four different simulation codes: the commercial finite element modeling (FEM) packages ABAQUS, ANSYS, and COMSOL, and a custom code executing the Elastodynamic Finite Integration Technique (EFIT). Benchmark comparisons are made between the simulation tools and both experimental laser Doppler vibrometry data and theoretical dispersion curves. A pristine and a delamination type case (Teflon insert in the experimental specimen) is studied. A summary is given of the accuracy of simulation results and the respective computational performance of the four different simulation tools. Published by Elsevier B.V.

Variable-viscosity thermal hemodynamic slip flow conveying nanoparticles through a permeable-walled composite stenosed artery

NASA Astrophysics Data System (ADS)

Akbar, Noreen Sher; Tripathi, Dharmendra; Bég, O. Anwar

2017-07-01

This paper presents a mathematical model for simulating viscous, incompressible, steady-state blood flow containing copper nanoparticles and coupled heat transfer through a composite stenosed artery with permeable walls. Wall slip hydrodynamic and also thermal buoyancy effects are included. The artery is simulated as an isotropic elastic tube, following Joshi et al. (2009), and a variable viscosity formulation is employed for the flowing blood. The equations governing the transport phenomena are non-dimensionalized and the resulting boundary value problem is solved analytically in the steady state subject to physically appropriate boundary conditions. Numerical computations are conducted to quantify the effects of relevant hemodynamic, thermophysical and nanoscale parameters emerging in the model on velocity and temperature profiles, wall shear stress, impedance resistance and also streamline distributions. The model may be applicable to drug fate transport modeling with nanoparticle agents and also to the optimized design of nanoscale medical devices for diagnosing stenotic diseases in circulatory systems.

Stochastic-Strength-Based Damage Simulation of Ceramic Matrix Composite Laminates

NASA Technical Reports Server (NTRS)

Nemeth, Noel N.; Mital, Subodh K.; Murthy, Pappu L. N.; Bednarcyk, Brett A.; Pineda, Evan J.; Bhatt, Ramakrishna T.; Arnold, Steven M.

2016-01-01

The Finite Element Analysis-Micromechanics Analysis Code/Ceramics Analysis and Reliability Evaluation of Structures (FEAMAC/CARES) program was used to characterize and predict the progressive damage response of silicon-carbide-fiber-reinforced reaction-bonded silicon nitride matrix (SiC/RBSN) composite laminate tensile specimens. Studied were unidirectional laminates [0] (sub 8), [10] (sub 8), [45] (sub 8), and [90] (sub 8); cross-ply laminates [0 (sub 2) divided by 90 (sub 2),]s; angled-ply laminates [plus 45 (sub 2) divided by -45 (sub 2), ]s; doubled-edge-notched [0] (sub 8), laminates; and central-hole laminates. Results correlated well with the experimental data. This work was performed as a validation and benchmarking exercise of the FEAMAC/CARES program. FEAMAC/CARES simulates stochastic-based discrete-event progressive damage of ceramic matrix composite and polymer matrix composite material structures. It couples three software programs: (1) the Micromechanics Analysis Code with Generalized Method of Cells (MAC/GMC), (2) the Ceramics Analysis and Reliability Evaluation of Structures Life Prediction Program (CARES/Life), and (3) the Abaqus finite element analysis program. MAC/GMC contributes multiscale modeling capabilities and micromechanics relations to determine stresses and deformations at the microscale of the composite material repeating-unit-cell (RUC). CARES/Life contributes statistical multiaxial failure criteria that can be applied to the individual brittle-material constituents of the RUC, and Abaqus is used to model the overall composite structure. For each FEAMAC/CARES simulation trial, the stochastic nature of brittle material strength results in random, discrete damage events that incrementally progress until ultimate structural failure.

Characterization of Triaxial Braided Composite Material Properties for Impact Simulation

NASA Technical Reports Server (NTRS)

Roberts, Gary D.; Goldberg, Robert K.; Biniendak, Wieslaw K.; Arnold, William A.; Littell, Justin D.; Kohlman, Lee W.

2009-01-01

The reliability of impact simulations for aircraft components made with triaxial braided carbon fiber composites is currently limited by inadequate material property data and lack of validated material models for analysis. Improvements to standard quasi-static test methods are needed to account for the large unit cell size and localized damage within the unit cell. The deformation and damage of a triaxial braided composite material was examined using standard quasi-static in-plane tension, compression, and shear tests. Some modifications to standard test specimen geometries are suggested, and methods for measuring the local strain at the onset of failure within the braid unit cell are presented. Deformation and damage at higher strain rates is examined using ballistic impact tests on 61- by 61- by 3.2-mm (24- by 24- by 0.125-in.) composite panels. Digital image correlation techniques were used to examine full-field deformation and damage during both quasi-static and impact tests. An impact analysis method is presented that utilizes both local and global deformation and failure information from the quasi-static tests as input for impact simulations. Improvements that are needed in test and analysis methods for better predictive capability are examined.

49 CFR 1503.421 - Streamlined civil penalty procedures for certain security violations.

Code of Federal Regulations, 2010 CFR

2010-10-01

... PROCEDURAL RULES INVESTIGATIVE AND ENFORCEMENT PROCEDURES Assessment of Civil Penalties by TSA § 1503.421 Streamlined civil penalty procedures for certain security violations. (a) Notice of violation. TSA, at the... violations described in the section and as otherwise provided by the Administrator. TSA may serve a Notice of...

Evaluation of the phase properties of hydrating cement composite using simulated nanoindentation technique

NASA Astrophysics Data System (ADS)

Gautham, S.; Sindu, B. S.; Sasmal, Saptarshi

2017-10-01

Properties and distribution of the products formed during the hydration of cementitious composite at the microlevel are investigated using a nanoindentation technique. First, numerical nanoindentation using nonlinear contact mechanics is carried out on three different phase compositions of cement paste, viz. mono-phase Tri-calcium Silicate (C3S), Di-calcium Silicate (C2S) and Calcium-Silicate-Hydrate (CSH) individually), bi-phase (C3S-CSH, C2S-CSH) and multi-phase (more than 10 individual phases including water pores). To reflect the multi-phase characteristics of hydrating cement composite, a discretized multi-phase microstructural model of cement composite during the progression of hydration is developed. Further, a grid indentation technique for simulated nanoindentation is established, and employed to evaluate the mechanical characteristics of the hydrated multi-phase cement paste. The properties obtained from the numerical studies are compared with those obtained from experimental grid nanoindentation. The influence of composition and distribution of individual phase properties on the properties obtained from indentation are closely investigated. The study paves the way to establishing the procedure for simulated grid nanoindentation to evaluate the mechanical properties of heterogeneous composites, and facilitates the design of experimental nanoindentation.

The combined effect of food-simulating solutions, brushing and staining on color stability of composite resins

PubMed Central

Silva, Tânia Mara Da; Sales, Ana Luísa Leme Simões; Pucci, Cesar Rogerio; Borges, Alessandra Bühler; Torres, Carlos Rocha Gomes

2017-01-01

Abstract Objective: This study evaluated the effect of food-simulating media associated with brushing and coffee staining on color stability of different composite resins. Materials and methods: Eighty specimens were prepared for each composite: Grandio SO (Voco), Amaris (Voco), Filtek Z350XT (3M/ESPE), Filtek P90 (3M/ESPE). They were divided into four groups according to food-simulating media for 7 days: artificial saliva (control), heptane, citric acid and ethanol. The composite surface was submitted to 10,950 brushing cycles (200 g load) in an automatic toothbrushing machine. The specimens were darkened with coffee solution at 37 °C for 24 h. After each treatment, color measurements were assessed by spectrophotometry, using CIE L*a*b* system. The overall color change (ΔE) was determined for each specimen at baseline (C1) and after the treatments (food-simulating media immersion/C2, brushing/C3 and dye solution/C4). Data were analyzed by two-way repeated measures ANOVA and Tukey’s tests (p < .05). Results: The results of RM-ANOVA showed significant differences for composites (p = .001), time (p = .001) and chemical degradation (p = .002). The mean of ΔE for composites were: Z350XT (5.39)a, Amaris (3.89)b, Grandio (3.75)bc, P90 (3.36)c. According to food-simulating media: heptane (4.41)a, citric acid (4.24)a, ethanol (4.02)ab, artificial saliva (3.76)b. For the treatments: dye solution (4.53)a, brushing (4.26)a, after food-simulating media (3.52)b. Conclusions: The composite resin Filtek Z350XT showed significantly higher staining than all other composite resin tested. The immersion in heptane and citric acid produced the highest color alteration than other food-simulating media. The exposure of samples to brushing protocols and darkening in coffee solution resulted in significant color alteration of the composite resins. PMID:28642926

78 FR 21118 - Agency Information Collection Activities; Comment Request; Streamlined Clearance Process for...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-04-09

...; Comment Request; Streamlined Clearance Process for Discretionary Grants AGENCY: Department of Education... also helps the public understand the Department's information collection requirements and provide the... for Discretionary Grants OMB Control Number: 1894-0001 Type of Review: An extension of an existing...

Ultralow percolation threshold of single walled carbon nanotube-epoxy composites synthesized via an ionic liquid dispersant/initiator

NASA Astrophysics Data System (ADS)

Watters, Arianna L.; Palmese, Giuseppe R.

2014-09-01

Uniform dispersion of single walled carbon nanotubes (SWNTs) in an epoxy was achieved by a streamlined mechano-chemical processing method. SWNT-epoxy composites were synthesized using a room temperature ionic liquid (IL) with an imidazolium cation and dicyanamide anion. The novel approach of using ionic liquid that behaves as a dispersant for SWNTs and initiator for epoxy polymerization greatly simplifies nanocomposite synthesis. The material was processed using simple and scalable three roll milling. The SWNT dispersion of the resultant composite was evaluated by electron microscopy and electrical conductivity measurements in conjunction with percolation theory. Processing conditions were optimized to achieve the lowest possible percolation threshold, 4.29 × 10-5 volume fraction SWNTs. This percolation threshold is among the best reported in literature yet it was obtained using a streamlined method that greatly simplifies processing.

Simulation of Degraded Properties of 2D plain Woven C/SiC Composites under Preloading Oxidation Atmosphere

NASA Astrophysics Data System (ADS)

Chen, Xihui; Sun, Zhigang; Sun, Jianfen; Song, Yingdong

2017-12-01

In this paper, a numerical model which incorporates the oxidation damage model and the finite element model of 2D plain woven composites is presented for simulation of the oxidation behaviors of 2D plain woven C/SiC composite under preloading oxidation atmosphere. The equal proportional reduction method is firstly proposed to calculate the residual moduli and strength of unidirectional C/SiC composite. The multi-scale method is developed to simulate the residual elastic moduli and strength of 2D plain woven C/SiC composite. The multi-scale method is able to accurately predict the residual elastic modulus and strength of the composite. Besides, the simulated residual elastic moduli and strength of 2D plain woven C/SiC composites under preloading oxidation atmosphere show good agreements with experimental results. Furthermore, the preload, oxidation time, temperature and fiber volume fractions of the composite are investigated to show their influences upon the residual elastic modulus and strength of 2D plain woven C/SiC composites.

The Stress-strain Behavior of Polymer-Nanotube Composites from Molecular Dynamics Simulations

NASA Technical Reports Server (NTRS)

Frankland, S. J. V.; Harik, V. M.; Odegard, G. M.; Brenner, D. W.; Gates, T. S.; Bushnell, Dennis M. (Technical Monitor)

2002-01-01

Stress-strain curves of polymer-carbon nanotube composites are derived from molecular dynamics simulations of a single-walled carbon nanotube embedded in polyethylene. A comparison is made between the response to mechanical loading of a composite with a long, continuous nanotube (replicated via periodic boundary conditions) and the response of a composite with a short, discontinuous nanotube. Both composites are mechanically loaded in the direction of and transverse to the NT axis. The long-nanotube composite shows an increase in the stiffness relative to the polymer and behaves anisotropically under the different loading conditions. The short-nanotube composite shows no enhancement relative to the polymer, most probably because of its low aspect ratio. The stress-strain curves are compared with rule-of-mixtures predictions.

Guessing right for the next war: streamlining, pooling, and right-timing force design decisions for an environment of uncertainty

DTIC Science & Technology

2017-05-25

Guessing Right for the Next War: Streamlining, Pooling, and Right-Timing Force Design Decisions for an Environment of Uncertainty A...JUN 2016 – MAY 2017 4. TITLE AND SUBTITLE Guessing Right for the Next War: Streamlining, Pooling, and Right- Timing Force Design Decisions for an...committing to one force design solution to modern combat. The Army after World War II shied away from temporary organizational systems like these in

Impact and Penetration Simulations for Composite Wing-like Structures

NASA Technical Reports Server (NTRS)

Knight, Norman F.

1998-01-01

The goal of this research project was to develop methodologies for the analysis of wing-like structures subjected to impact loadings. Low-speed impact causing either no damage or only minimal damage and high-speed impact causing severe laminate damage and possible penetration of the structure were to be considered during this research effort. To address this goal, an assessment of current analytical tools for impact analysis was performed. Assessment of the analytical tools for impact and penetration simulations with regard to accuracy, modeling, and damage modeling was considered as well as robustness, efficient, and usage in a wing design environment. Following a qualitative assessment, selected quantitative evaluations will be performed using the leading simulation tools. Based on this assessment, future research thrusts for impact and penetration simulation of composite wing-like structures were identified.

Turbulence modeling in simulation of gas-turbine flow and heat transfer.

PubMed

Brereton, G; Shih, T I

2001-05-01

The popular k-epsilon type two-equation turbulence models, which are calibrated by experimental data from simple shear flows, are analyzed for their ability to predict flows involving shear and an extra strain--flow with shear and rotation and flow with shear and streamline curvature. The analysis is based on comparisons between model predictions and those from measurements and large-eddy simulations of homogenous flows involving shear and an extra strain, either from rotation or from streamline curvature. Parameters are identified, which show the conditions under which performance of k-epsilon type models can be expected to be poor.

Full-Scale Crash Test and Finite Element Simulation of a Composite Prototype Helicopter

NASA Technical Reports Server (NTRS)

Jackson, Karen E.; Fasanella, Edwin L.; Boitnott, Richard L.; Lyle, Karen H.

2003-01-01

A full-scale crash test of a prototype composite helicopter was performed at the Impact Dynamics Research Facility at NASA Langley Research Center in 1999 to obtain data for validation of a finite element crash simulation. The helicopter was the flight test article built by Sikorsky Aircraft during the Advanced Composite Airframe Program (ACAP). The composite helicopter was designed to meet the stringent Military Standard (MIL-STD-1290A) crashworthiness criteria and was outfitted with two crew and two troop seats and four anthropomorphic dummies. The test was performed at 38-ft/s vertical and 32.5-ft/s horizontal velocity onto a rigid surface. An existing modal-vibration model of the Sikorsky ACAP helicopter was converted into a model suitable for crash simulation. A two-stage modeling approach was implemented and an external user-defined subroutine was developed to represent the complex landing gear response. The crash simulation was executed with a nonlinear, explicit transient dynamic finite element code. Predictions of structural deformation and failure, the sequence of events, and the dynamic response of the airframe structure were generated and the numerical results were correlated with the experimental data to validate the simulation. The test results, the model development, and the test-analysis correlation are described.

Ancient Streamlined Islands of the Palos Outflow Channel

NASA Image and Video Library

2016-08-24

This image shows the northern terminus of an outflow channel located in the volcanic terrains of Amenthes Planum. The channel sources from the Palos impact crater to the south, where water flowed into the crater from Tinto Vallis and eventually formed a paleo lake. As rising lake levels breached through the crater's rim and inundated the plains to the north, the resulting high velocity, large discharge floods plucked out and eroded the volcanic plains scouring out the "Palos Outflow Channel" and the streamlined mesa-islands on its floor. These streamlined forms are the eroded remnants of plains material sculpted by catastrophic floods and are not sediment deposits emplaced by lower magnitude stream flows. Both the fluvial channel floor and the volcanic island surfaces are densely cratered by impacts suggesting that both the surfaces and the flood events are ancient. The morphology (shape) of the channel system and its islands have been preserved through the eons, but water has long been absent from this drainage system. Since then, winds have transported light-toned sediments across this terrain forming extensive dune fields within the channel system, on the floors of impact craters, and in other protected locations in the Palos Outflow Channel region. A closer look shows chevron, or fish-bone shaped, light-toned dunes located near the top of the image where numerous smaller channels have cut through the landscape. These dunes likely started out as Transverse Aeolian Ridges (TAR) that form perpendicular to the prevailing wind direction where the wind-blown sediment supply is scarce. This intriguing morphology likely reflects changes in the prevailing wind environment over time. http://photojournal.jpl.nasa.gov/catalog/PIA21023

Streamlined bioreactor-based production of human cartilage tissues.

PubMed

Tonnarelli, B; Santoro, R; Adelaide Asnaghi, M; Wendt, D

2016-05-27

Engineered tissue grafts have been manufactured using methods based predominantly on traditional labour-intensive manual benchtop techniques. These methods impart significant regulatory and economic challenges, hindering the successful translation of engineered tissue products to the clinic. Alternatively, bioreactor-based production systems have the potential to overcome such limitations. In this work, we present an innovative manufacturing approach to engineer cartilage tissue within a single bioreactor system, starting from freshly isolated human primary chondrocytes, through the generation of cartilaginous tissue grafts. The limited number of primary chondrocytes that can be isolated from a small clinically-sized cartilage biopsy could be seeded and extensively expanded directly within a 3D scaffold in our perfusion bioreactor (5.4 ± 0.9 doublings in 2 weeks), bypassing conventional 2D expansion in flasks. Chondrocytes expanded in 3D scaffolds better maintained a chondrogenic phenotype than chondrocytes expanded on plastic flasks (collagen type II mRNA, 18-fold; Sox-9, 11-fold). After this "3D expansion" phase, bioreactor culture conditions were changed to subsequently support chondrogenic differentiation for two weeks. Engineered tissues based on 3D-expanded chondrocytes were more cartilaginous than tissues generated from chondrocytes previously expanded in flasks. We then demonstrated that this streamlined bioreactor-based process could be adapted to effectively generate up-scaled cartilage grafts in a size with clinical relevance (50 mm diameter). Streamlined and robust tissue engineering processes, as the one described here, may be key for the future manufacturing of grafts for clinical applications, as they facilitate the establishment of compact and closed bioreactor-based production systems, with minimal automation requirements, lower operating costs, and increased compliance to regulatory guidelines.

[Surface roughness and gloss of novel flowable composites after polishing and simulated brushing wear].

PubMed

Wang, R L; Yuan, C Y; Pan, Y X; Tian, F C; Wang, Z H; Wang, X Y

2017-04-09

Objective: To investigate surface properties of novel flowable composites after polishing and simulated brushing wear, compared to their pasty counterpart. Methods: Composites employed in this study were: three flowable composites (A1: Clearfil Majesty ES Flow; B1: Beautifil Flow Plus F00; C1: Filtek Bulk Fill) and three paste composites (A2: Clearfil Majesty; B2: Beautifil; C2: Filtek Z350. Eleven disk-shaped specimens were made for each material. The specimens were cured, then subjected to sandpaper finishing for 20 s, one-step polishing for 30 s, finally subjected to simulated brushing for 10 000 cycles. Surface roughness and glossiness were measured before finishing, after finishing, after polishing, after 5 000 brushing cycles and after 10 000 brushing cycles, respectively. Data obtained were analyzed using two-way ANOVA method. Scanning electron microscope was employed to examine the microscopic appearance of each material. Results: Surface roughness (0.11~0.22 μm) and glossiness (74.25~86.48 GU) of each material were similar after one-step polishing. After brushing simulation, roughness increased significantly and glossiness decreased significantly for each material ( P< 0.05). Group A1 presented the best gloss ([50.68±1.58] GU) after final wear ( P< 0.05). Flowable composites of group A1 and B1 tested in the present setup showed better surface properties compared to their pasty counterpart (group A2 and B2). Conclusions: Within the limit of this study, flowable composites tested in the present research can obtain similar surface polish or even better than the paste composite counterpart.

Effective Report Preparation: Streamlining the Reporting Process. AIR 1999 Annual Forum Paper.

ERIC Educational Resources Information Center

Dalrymple, Margaret; Wang, Mindy; Frost, Jacquelyn

This paper describes the processes and techniques used to improve and streamline the standard student reports used at Purdue University (Indiana). Various models for analyzing reporting processes are described, especially the model used in the study, the Shewart or Deming Cycle, a method that aids in continuous analysis and improvement through a…

Composition of chitosan-hydroxyapatite-collagen composite scaffold evaluation after simulated body fluid immersion as reconstruction material

NASA Astrophysics Data System (ADS)

Verisqa, F.; Triaminingsih, S.; Corputty, J. E. M.

2017-08-01

Hydroxyapatite (HA) formation is one of the most important aspects of bone regeneration. Because domestically made chitosan-hydroxyapatite-collagen composite scaffolding from crab shell and bovine bone and tendon has potential as a maxillofacial reconstruction material, the material’s HA-forming ability requires evaluation. The aim of this research is to investigate chitosan-hydroxyapatite-collagen composite scaffold’s potential as a maxillofacial reconstruction material by observing the scaffold’s compositional changes. Scaffold specimens were immersed in 37°C simulated body fluid (SBF) for periods of 2, 4, 6, and 8 days. Scaffold composition was then evaluated by using energy dispersive spectroscopy (EDS). The calcium (Ca) and phosphorus (P) percentages of the scaffold were found to increase following SBF immersion. The high Ca/P ratio (3.82) on the scaffold indicated HA formation. Ion exchange played a significant role in the increased percentages of Ca and P, which led to new HA layer formation. The scaffold’s HA acted as a nucleation site of Ca and P from the SBF, with collagen and chitosan as the scaffold’s matrix. Chitosan-hydroxyapatite-collagen composite scaffold shows potential as a maxillofacial reconstruction material, since its composition favors HA formation.

Comparative transcriptome analysis reveals insights into the streamlined genomes of haplosclerid demosponges

PubMed Central

Guzman, Christine; Conaco, Cecilia

2016-01-01

Sponges (Porifera) are one of the most ancestral metazoan groups. They are characterized by a simple body plan lacking the true tissues and organ systems found in other animals. Members of this phylum display a remarkable diversity of form and function and yet little is known about the composition and complexity of their genomes. In this study, we sequenced the transcriptomes of two marine haplosclerid sponges belonging to Demospongiae, the largest and most diverse class within phylum Porifera, and compared their gene content with members of other sponge classes. We recovered 44,693 and 50,067 transcripts expressed in adult tissues of Haliclona amboinensis and Haliclona tubifera, respectively. These transcripts translate into 20,280 peptides in H. amboinensis and 18,000 peptides in H. tubifera. Genes associated with important signaling and metabolic pathways, regulatory networks, as well as genes that may be important in the organismal stress response, were identified in the transcriptomes. Futhermore, lineage-specific innovations were identified that may be correlated with observed sponge characters and ecological adaptations. The core gene complement expressed within the tissues of adult haplosclerid demosponges may represent a streamlined and flexible genetic toolkit that underlies the ecological success and resilience of sponges to environmental stress. PMID:26738846

Comparative transcriptome analysis reveals insights into the streamlined genomes of haplosclerid demosponges

NASA Astrophysics Data System (ADS)

Guzman, Christine; Conaco, Cecilia

2016-01-01

Sponges (Porifera) are one of the most ancestral metazoan groups. They are characterized by a simple body plan lacking the true tissues and organ systems found in other animals. Members of this phylum display a remarkable diversity of form and function and yet little is known about the composition and complexity of their genomes. In this study, we sequenced the transcriptomes of two marine haplosclerid sponges belonging to Demospongiae, the largest and most diverse class within phylum Porifera, and compared their gene content with members of other sponge classes. We recovered 44,693 and 50,067 transcripts expressed in adult tissues of Haliclona amboinensis and Haliclona tubifera, respectively. These transcripts translate into 20,280 peptides in H. amboinensis and 18,000 peptides in H. tubifera. Genes associated with important signaling and metabolic pathways, regulatory networks, as well as genes that may be important in the organismal stress response, were identified in the transcriptomes. Futhermore, lineage-specific innovations were identified that may be correlated with observed sponge characters and ecological adaptations. The core gene complement expressed within the tissues of adult haplosclerid demosponges may represent a streamlined and flexible genetic toolkit that underlies the ecological success and resilience of sponges to environmental stress.

Numerical tool for SMA material simulation: application to composite structure design

NASA Astrophysics Data System (ADS)

Chemisky, Yves; Duval, Arnaud; Piotrowski, Boris; Ben Zineb, Tarak; Tahiri, Vanessa; Patoor, Etienne

2009-10-01

Composite materials based on shape memory alloys (SMA) have received growing attention over these last few years. In this paper, two particular morphologies of composites are studied. The first one is an SMA/elastomer composite in which a snake-like wire NiTi SMA is embedded into an elastomer ribbon. The second one is a commercial Ni47Ti44Nb9 which presents elastic-plastic inclusions in an NiTi SMA matrix. In both cases, the design of such composites required the development of an SMA design tool, based on a macroscopic 3D constitutive law for NiTi alloys. Two different strategies are then applied to compute these composite behaviors. For the SMA/elastomer composite, the macroscopic behavior law is implemented in commercial FEM software, and for the Ni47Ti44Nb9 a scale transition approach based on the Mori-Tanaka scheme is developed. In both cases, simulations are compared to experimental data.

Effects of simulated lightning on composite and metallic joints

NASA Technical Reports Server (NTRS)

Howell, W. E.; Plumer, J. A.

1982-01-01

The effects of simulated lightning strikes and currents on aircraft bonded joints and access/inspection panels were investigated. Both metallic and composite specimens were tested. Tests on metal fuel feed through elbows in graphite/epoxy structures were evaluated. Sparking threshold and residual strength of single lap bonded joints and sparking threshold of access/inspection panels and metal fuel feed through elbows are reported.

77 FR 21908 - Approval and Promulgation of Air Quality Implementation Plans; Pennsylvania; Streamlining...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-04-12

... permit or a Title V permit, ``* * * to permit the evaluation of the air contamination aspects of the... Promulgation of Air Quality Implementation Plans; Pennsylvania; Streamlining Amendments to the Plan Approval... Air Act (CAA). DATES: Written comments must be received on or before May 14, 2012. ADDRESSES: Submit...

The status of analytical preparation for 2-dimensional testing at high transonic speeds in the University of Southampton transonic self-streamlining wind tunnel

NASA Technical Reports Server (NTRS)

Lewis, M. C.

1984-01-01

Validation data from the Transonic Self-Streamlining Wind Tunnel has proved the feasibility of streamlining two dimensional flexible walls at low speeds and up to transonic speeds, the upper limit being the speed where the flexible walls are just supercritical. At this condition, breakdown of the wall setting strategy is evident in that convergence is neither as rapid nor as stable as for lower speeds, and wall streamlining criteria are not always completely satisfied. The only major step necessary to permit the extension of two dimensional testing into higher transonic speeds is the provision of a rapid algorithm to solve for mixed flow in the imagery flow fields. The status of two dimensional high transonic testing in the Transonic Self-Streamlining Wind Tunnel is outlined and, in particular, the progress of adapting an algorithm, which solves the Transonic Small Perturbation Equation, for predicting the imagery flow fields is detailed.

Molecular Simulation Study of Gas Solubility and Diffusion in a Polymer-Boron Nitride Nanotube Composite.

PubMed

Wang, Congyue; Jagirdar, Preeti; Naserifar, Saber; Sahimi, Muhammad

2016-02-25

We study the possibility of using polymer composites made of a polymer and boron nitride nanotubes (BNNTs) as a new type of membranes for gas separation. The polymer used is amorphous poly(ether imide) (PEI), and zigzag BNNTs are used to generate the composites with the PEI. The solubilities and self-diffusivities of CO2 and CH4 in the PEI and its composites with the BNNTs are calculated by molecular dynamics (MD) simulations. The molecular models of the PEI and its composites with the BNNTs are generated using energy minimization and MD simulation, and the Universal Force Field is used to represent the interactions between all the atoms. The morhology of the composites are characterized and are compared with that of PEI. The accuracy of the computations is tested by calculating the gases' solubilities and self-diffsivities in the pure PEI and comparing them with the experimental data. Good agreement is obtained with the data. The computed diffusivities and solubilities in the polymer-BNNTs composites are much larger than those in the pure polymer, which are attributed to the changes that the BNNTs induce in the polymer composite's free-volume distribution. As the mechanical properties of the polymer-BNNTs composites are superior over those of the pure PEI, their use as a membrane for gas separation offers distinct advantages over the pure polymer. We also demonstrate that, calculating the diffusion coefficients with MD simulations in the NPT ensemble, as opposed to the common practice of utilizing the NVT ensemble, leads to much more accurate results.

Microcracking in Composite Laminates: Simulation of Crack-Induced Ultrasound Attenuation

NASA Technical Reports Server (NTRS)

Leckey, C. A. C.; Rogge, M. D.; Parker, F. R.

2012-01-01

Microcracking in composite laminates is a known precursor to the growth of inter-ply delaminations and larger scale damage. Microcracking can lead to the attenuation of ultrasonic waves due to the crack-induced scattering. 3D elastodynamic finite integration technique (EFIT) has been implemented to explore the scattering of ultrasonic waves due to microcracks in anisotropic composite laminates. X-ray microfocus computed tomography data was directly input into the EFIT simulation for these purposes. The validated anisotropic 3D EFIT code is shown to be a useful tool for exploring the complex multiple-scattering which arises from extensive microcracking.

The Zig-zag Instability of Streamlined Bodies

NASA Astrophysics Data System (ADS)

Guillet, Thibault; Coux, Martin; Quere, David; Clanet, Christophe

2017-11-01

When a floating bluff body, like a sphere, impacts water with a vertical velocity, its trajectory is straight and the depth of its dive increases with its initial velocity. Even though we observe the same phenomenon at low impact speed for axisymmetric streamlined bodies, the trajectory is found to deviate from the vertical when the velocity overcomes a critical value. This instability results from a competition between the destabilizing torque of the lift and the stabilizing torque of the Archimede's force. Balancing these torques yields a prediction on the critical velocity above which the instability appears. This theoretical value is found to depend on the position of the gravity center of the projectile and predicts with a full agreement the behaviour observed in our different experiments. Project funded by DGA.

Damage Simulation in Composite Materials: Why It Matters and What Is Happening Currently at NASA in This Area

NASA Technical Reports Server (NTRS)

McElroy, Mack; de Carvalho, Nelson; Estes, Ashley; Lin, Shih-yung

2017-01-01

Use of lightweight composite materials in space and aircraft structure designs is often challenging due to high costs associated with structural certification. Of primary concern in the use of composite structures is durability and damage tolerance. This concern is due to the inherent susceptibility of composite materials to both fabrication and service induced flaws. Due to a lack of general industry accepted analysis tools applicable to composites damage simulation, a certification procedure relies almost entirely on testing. It is this reliance on testing, especially compared to structures comprised of legacy metallic materials where damage simulation tools are available, that can drive costs for using composite materials in aerospace structures. The observation that use of composites can be expensive due to testing requirements is not new and as such, research on analysis tools for simulating damage in composite structures has been occurring for several decades. A convenient approach many researchers/model-developers in this area have taken is to select a specific problem relevant to aerospace structural certification and develop a model that is accurate within that scope. Some examples are open hole tension tests, compression after impact tests, low-velocity impact, damage tolerance of an embedded flaw, and fatigue crack growth to name a few. Based on the premise that running analyses is cheaper than running tests, one motivation that many researchers in this area have is that if generally applicable and reliable damage simulation tools were available the dependence on certification testing could be lessened thereby reducing overall design cost. It is generally accepted that simulation tools if applied in this manner would still need to be thoroughly validated and that composite testing will never be completely replaced by analysis. Research and development is currently occurring at NASA to create numerical damage simulation tools applicable to damage in

Improving patient access and streamlining processes through enterprise intelligence systems.

PubMed

Dunn, Ronald L

2014-01-01

This article demonstrates how enterprise intelligence systems can be used to improve operational efficiency in hospitals. Enterprise intelligence systems mine raw data from disparate systems and transform the data into actionable information, which when used appropriately, support streamlined processes, optimize resources, and positively affect staff efficiency and the quality of patient care. Case studies on the implementation of McKesson Performance Visibility and Capacity Planner enterprise intelligence solutions at the Southlake Regional Health Centre and Lions Gate and Richmond Hospitals are provided.

Simulation of Forming and Wrinkling of Textile Composite Reinforcements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hamila, N.; Wang, P.; Vidal-Salle, E.

Because of the very weak textile bending stiffness, wrinkles are frequent during composite reinforcement forming. The simulation of the shape of these wrinkles during the forming process permits to verify there is no wrinkle in the useful part of the preform. In this paper the role of tensions, in-plane shear and bending rigidities in wrinkling development are analyzed. In-plane shear plays a main role for onset of wrinkles in double-curved shape forming but wrinkling is a global phenomenon depending on all strains and stiffnesses and on boundary conditions. The bending stiffness mainly determines the shape of the wrinkles and amore » membrane approach it is not sufficient to simulate wrinkles.« less

Simulating the Impact Response of Full-Scale Composite Airframe Structures

NASA Technical Reports Server (NTRS)

Fasanella, Edwin L.; Jackson, Karen E.; Littell, Justin D.; Seal, Michael D.

2012-01-01

NASA Langley Research Center obtained a composite helicopter cabin structure in 2010 from the US Army's Survivable Affordable Repairable Airframe Program (SARAP) that was fabricated by Sikorsky Aircraft Corporation. The cabin had been subjected to a vertical drop test in 2008 to evaluate a tilting roof concept to limit the intrusion of overhead masses into the fuselage cabin. Damage to the cabin test article was limited primarily to the roof. Consequently, the roof area was removed and the remaining structure was cut into test specimens including a large subfloor section and a forward framed fuselage section. In 2011, NASA and Sikorsky entered into a cooperative research agreement to study the impact responses of composite airframe structures and to evaluate the capabilities of the explicit transient dynamic finite element code, LS-DYNA®, to simulate these responses including damage initiation and progressive failure. Most of the test articles were manufactured of graphite unidirectional tape composite with a thermoplastic resin system. However, the framed fuselage section was constructed primarily of a plain weave graphite fabric material with a thermoset resin system. Test data were collected from accelerometers and full-field photogrammetry. The focus of this paper will be to document impact testing and simulation results for the longitudinal impact of the subfloor section and the vertical drop test of the forward framed fuselage section.

Streamlined Genome Sequence Compression using Distributed Source Coding

PubMed Central

Wang, Shuang; Jiang, Xiaoqian; Chen, Feng; Cui, Lijuan; Cheng, Samuel

2014-01-01

We aim at developing a streamlined genome sequence compression algorithm to support alternative miniaturized sequencing devices, which have limited communication, storage, and computation power. Existing techniques that require heavy client (encoder side) cannot be applied. To tackle this challenge, we carefully examined distributed source coding theory and developed a customized reference-based genome compression protocol to meet the low-complexity need at the client side. Based on the variation between source and reference, our protocol will pick adaptively either syndrome coding or hash coding to compress subsequences of changing code length. Our experimental results showed promising performance of the proposed method when compared with the state-of-the-art algorithm (GRS). PMID:25520552

Wear simulation of resin composites and the relationship to clinical wear.

PubMed

Barkmeier, Wayne W; Latta, Mark A; Erickson, Robert L; Wilwerding, Terry M

2008-01-01

This study used a new generalized wear model to examine the relationship between wear simulation and the clinical wear of two resin composites. Ten specimens each of P50 and Z100, were subjected to 100,000, 400,000 and 800,000 cycles in a spring-loaded piston-type wear simulator. Wear was generated using flat, cylindrically-shaped stainless steel antagonists on the resin composites, which were placed in custom stainless steel fixtures. A slurry of polymethyl methacrylate beads was used as the abrasive media. Wear was determined using profilometry, and the parameters examined included volume loss (mm3), maximum depth (microm), mean maximum depth (microm) and mean depth (microm). Statistical analysis of the laboratory wear data using ANOVA and Tukey's post hoc test showed a significant difference (p<0.05) for wear between the two materials and the number of cycles. Mean maximum wear (microm) values (100K--P50--11.5 +/- 1.8; Z100--4.9 +/- 1.0; 400K--P50--17.2 +/- 2.7; Z100--6.0 +/- 1.7; 800K--P50--20.5 +/- 4.6; Z100--9.6 +/- 2.5) were used for comparisons with clinical data. Previous clinical studies of P50 and Z100 were used to examine the relationship between laboratory and clinical wear. Linear regression analysis was used to predict laboratory and clinical wear rates. The laboratory wear rate for P50 was 1.3 microm/100K cycles and the rate for Z100 was 0.7 microm/100K cycles. The clinical wear rates for P50 and Z100 were 8.3 microm/year and 4.0 microm/year, respectively. The ratio of wear rates of P50 to Z100 for wear simulation was 1.9 and the ratio of P50 to Z100 for clinical rates was 2.1. These ratios showed good agreement between the relative wear rates of laboratory and clinical wear. For the two composite materials examined, this new simulation model appears to be effective for evaluating the relative wear of resin composites.

EBSCO's Usage Consolidation Attempts to Streamline Gathering, Storage, and Reporting of Usage Statistics

ERIC Educational Resources Information Center

Remy, Charlie

2012-01-01

This paper provides an overview of EBSCO's new Usage Consolidation product designed to streamline the harvesting, storage, and analysis of usage statistics from electronic resources. Strengths and weaknesses of the product are discussed as well as an early beta partner's experience. In the current atmosphere of flat or declining budgets, libraries…

Two inviscid computational simulations of separated flow about airfoils

NASA Technical Reports Server (NTRS)

Barnwell, R. W.

1976-01-01

Two inviscid computational simulations of separated flow about airfoils are described. The basic computational method is the line relaxation finite-difference method. Viscous separation is approximated with inviscid free-streamline separation. The point of separation is specified, and the pressure in the separation region is calculated. In the first simulation, the empiricism of constant pressure in the separation region is employed. This empiricism is easier to implement with the present method than with singularity methods. In the second simulation, acoustic theory is used to determine the pressure in the separation region. The results of both simulations are compared with experiment.

48 CFR 13.005 - Federal Acquisition Streamlining Act of 1994 list of inapplicable laws.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 48 Federal Acquisition Regulations System 1 2010-10-01 2010-10-01 false Federal Acquisition Streamlining Act of 1994 list of inapplicable laws. 13.005 Section 13.005 Federal Acquisition Regulations System FEDERAL ACQUISITION REGULATION CONTRACTING METHODS AND CONTRACT TYPES SIMPLIFIED ACQUISITION...

48 CFR 13.005 - Federal Acquisition Streamlining Act of 1994 list of inapplicable laws.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 48 Federal Acquisition Regulations System 1 2012-10-01 2012-10-01 false Federal Acquisition Streamlining Act of 1994 list of inapplicable laws. 13.005 Section 13.005 Federal Acquisition Regulations System FEDERAL ACQUISITION REGULATION CONTRACTING METHODS AND CONTRACT TYPES SIMPLIFIED ACQUISITION...

48 CFR 13.005 - Federal Acquisition Streamlining Act of 1994 list of inapplicable laws.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 48 Federal Acquisition Regulations System 1 2013-10-01 2013-10-01 false Federal Acquisition Streamlining Act of 1994 list of inapplicable laws. 13.005 Section 13.005 Federal Acquisition Regulations System FEDERAL ACQUISITION REGULATION CONTRACTING METHODS AND CONTRACT TYPES SIMPLIFIED ACQUISITION...

48 CFR 13.005 - Federal Acquisition Streamlining Act of 1994 list of inapplicable laws.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 48 Federal Acquisition Regulations System 1 2011-10-01 2011-10-01 false Federal Acquisition Streamlining Act of 1994 list of inapplicable laws. 13.005 Section 13.005 Federal Acquisition Regulations System FEDERAL ACQUISITION REGULATION CONTRACTING METHODS AND CONTRACT TYPES SIMPLIFIED ACQUISITION...

Stochastic-Strength-Based Damage Simulation Tool for Ceramic Matrix and Polymer Matrix Composite Structures

NASA Technical Reports Server (NTRS)

Nemeth, Noel N.; Bednarcyk, Brett A.; Pineda, Evan J.; Walton, Owen J.; Arnold, Steven M.

2016-01-01

Stochastic-based, discrete-event progressive damage simulations of ceramic-matrix composite and polymer matrix composite material structures have been enabled through the development of a unique multiscale modeling tool. This effort involves coupling three independently developed software programs: (1) the Micromechanics Analysis Code with Generalized Method of Cells (MAC/GMC), (2) the Ceramics Analysis and Reliability Evaluation of Structures Life Prediction Program (CARES/ Life), and (3) the Abaqus finite element analysis (FEA) program. MAC/GMC contributes multiscale modeling capabilities and micromechanics relations to determine stresses and deformations at the microscale of the composite material repeating unit cell (RUC). CARES/Life contributes statistical multiaxial failure criteria that can be applied to the individual brittle-material constituents of the RUC. Abaqus is used at the global scale to model the overall composite structure. An Abaqus user-defined material (UMAT) interface, referred to here as "FEAMAC/CARES," was developed that enables MAC/GMC and CARES/Life to operate seamlessly with the Abaqus FEA code. For each FEAMAC/CARES simulation trial, the stochastic nature of brittle material strength results in random, discrete damage events, which incrementally progress and lead to ultimate structural failure. This report describes the FEAMAC/CARES methodology and discusses examples that illustrate the performance of the tool. A comprehensive example problem, simulating the progressive damage of laminated ceramic matrix composites under various off-axis loading conditions and including a double notched tensile specimen geometry, is described in a separate report.

Quantum mechanical streamlines. I - Square potential barrier

NASA Technical Reports Server (NTRS)

Hirschfelder, J. O.; Christoph, A. C.; Palke, W. E.

1974-01-01

Exact numerical calculations are made for scattering of quantum mechanical particles hitting a square two-dimensional potential barrier (an exact analog of the Goos-Haenchen optical experiments). Quantum mechanical streamlines are plotted and found to be smooth and continuous, to have continuous first derivatives even through the classical forbidden region, and to form quantized vortices around each of the nodal points. A comparison is made between the present numerical calculations and the stationary wave approximation, and good agreement is found between both the Goos-Haenchen shifts and the reflection coefficients. The time-independent Schroedinger equation for real wavefunctions is reduced to solving a nonlinear first-order partial differential equation, leading to a generalization of the Prager-Hirschfelder perturbation scheme. Implications of the hydrodynamical formulation of quantum mechanics are discussed, and cases are cited where quantum and classical mechanical motions are identical.

75 FR 29321 - Streamlined Procedure for Appeal Brief Review in Ex Parte Reexamination Proceedings

Federal Register 2010, 2011, 2012, 2013, 2014

2010-05-25

... DEPARTMENT OF COMMERCE Patent and Trademark Office [Docket No.: PTO-P-2010-0046] Streamlined... Trademark Office, Commerce. ACTION: Notice. SUMMARY: The United States Patent and Trademark Office (USPTO... Intellectual Property and Director of the United States Patent and Trademark Office. [FR Doc. 2010-12534 Filed...

A compositional reservoir simulator on distributed memory parallel computers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rame, M.; Delshad, M.

1995-12-31

This paper presents the application of distributed memory parallel computes to field scale reservoir simulations using a parallel version of UTCHEM, The University of Texas Chemical Flooding Simulator. The model is a general purpose highly vectorized chemical compositional simulator that can simulate a wide range of displacement processes at both field and laboratory scales. The original simulator was modified to run on both distributed memory parallel machines (Intel iPSC/960 and Delta, Connection Machine 5, Kendall Square 1 and 2, and CRAY T3D) and a cluster of workstations. A domain decomposition approach has been taken towards parallelization of the code. Amore » portion of the discrete reservoir model is assigned to each processor by a set-up routine that attempts a data layout as even as possible from the load-balance standpoint. Each of these subdomains is extended so that data can be shared between adjacent processors for stencil computation. The added routines that make parallel execution possible are written in a modular fashion that makes the porting to new parallel platforms straight forward. Results of the distributed memory computing performance of Parallel simulator are presented for field scale applications such as tracer flood and polymer flood. A comparison of the wall-clock times for same problems on a vector supercomputer is also presented.« less

77 FR 50691 - Request for Information (RFI): Guidance on Data Streamlining and Reducing Undue Reporting Burden...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-08-22

.... Attention: HIV Data Streamlining. FOR FURTHER INFORMATION CONTACT: Andrew D. Forsyth Ph.D. or Vera... of HIV/AIDS programs that vary in their specifications (e.g., numerators, denominators, time frames...

Simulating the Composite Propellant Manufacturing Process

NASA Technical Reports Server (NTRS)

Williamson, Suzanne; Love, Gregory

2000-01-01

There is a strategic interest in understanding how the propellant manufacturing process contributes to military capabilities outside the United States. The paper will discuss how system dynamics (SD) has been applied to rapidly assess the capabilities and vulnerabilities of a specific composite propellant production complex. These facilities produce a commonly used solid propellant with military applications. The authors will explain how an SD model can be configured to match a specific production facility followed by a series of scenarios designed to analyze operational vulnerabilities. By using the simulation model to rapidly analyze operational risks, the analyst gains a better understanding of production complexities. There are several benefits of developing SD models to simulate chemical production. SD is an effective tool for characterizing complex problems, especially the production process where the cascading effect of outages quickly taxes common understanding. By programming expert knowledge into an SD application, these tools are transformed into a knowledge management resource that facilitates rapid learning without requiring years of experience in production operations. It also permits the analyst to rapidly respond to crisis situations and other time-sensitive missions. Most importantly, the quantitative understanding gained from applying the SD model lends itself to strategic analysis and planning.

Computational simulation of composite structures with and without damage. M.S. Thesis Final Report

NASA Technical Reports Server (NTRS)

Wilt, Thomas F.

1994-01-01

A methodology is described which uses finite element analysis of various laminates to computationally simulate the effects of delamination damage initiation and growth on the structural behavior of laminated composite structures. The delamination area is expanded according to a set pattern. As the delamination area increases, how the structural response of the laminate changes with respect to buckling and strain energy release rate are investigated. Rules are presented for laminates of different configurations, materials and thickness. These results demonstrate that computational simulation methods can provide alternate methods to investigate the complex delamination damage mechanisms found in composite structures.

Modelling and simulation of the consolidation behavior during thermoplastic prepreg composites forming process

NASA Astrophysics Data System (ADS)

Xiong, H.; Hamila, N.; Boisse, P.

2017-10-01

Pre-impregnated thermoplastic composites have recently attached increasing interest in the automotive industry for their excellent mechanical properties and their rapid cycle manufacturing process, modelling and numerical simulations of forming processes for composites parts with complex geometry is necessary to predict and optimize manufacturing practices, especially for the consolidation effects. A viscoelastic relaxation model is proposed to characterize the consolidation behavior of thermoplastic prepregs based on compaction tests with a range of temperatures. The intimate contact model is employed to predict the evolution of the consolidation which permits the microstructure prediction of void presented through the prepreg. Within a hyperelastic framework, several simulation tests are launched by combining a new developed solid shell finite element and the consolidation models.

The Experiment and Numerical Simulation of Composite Countersunk-head Fasteners Pull-through Mechanical Behavior

NASA Astrophysics Data System (ADS)

Mu, Junwu; Guan, Zhidong; Bian, Tianya; Li, Zengshan; Wang, Kailun; Liu, Sui

2014-10-01

Fasteners made of the anisotropic carbon/carbon (C/C) composite material have been developed for joining C/C composite material components in the high-temperature environment. The fastener specimens are fabricated from the C/C composites which are made from laminated carbon cloths with Z-direction carbon fibers being punctured as perform. Densification process cycles such as the thermal gradient chemical vapor infiltration (CVI) technology were repeated to obtain high density C/C composites fastener. The fasteners were machined parallel to the carbon cloths (X-Y direction). A method was proposed to test pull-through mechanical behavior of the countersunk-head C/C composite material fasteners. The damage morphologies of the fasteners were observed through the charge coupled device (CCD) and the scanning electron microscope (SEM). The internal micro-structure were observed through the high-resolution Mirco-CT systems. Finally, an excellent simulation of the C/C composite countersunk-head fasteners were performed with the finite element method (FEM), in which the damage evolution model of the fastener was established based on continuum damage mechanics. The simulation is correspond well with the test result . The damage evolution process and the relation between the countersunk depth and the ultimate load was investigated.

Local Elastic Constants for Epoxy-Nanotube Composites from Molecular Dynamics Simulation

NASA Technical Reports Server (NTRS)

Frankland, S. J. V.; Gates, T. S.

2007-01-01

A method from molecular dynamics simulation is developed for determining local elastic constants of an epoxy/nanotube composite. The local values of C11, C33, K12, and K13 elastic constants are calculated for an epoxy/nanotube composite as a function of radial distance from the nanotube. While the results possess a significant amount of statistical uncertainty resulting from both the numerical analysis and the molecular fluctuations during the simulation, the following observations can be made. If the size of the region around the nanotube is increased from shells of 1 to 6 in thickness, then the scatter in the data reduces enough to observe trends. All the elastic constants determined are at a minimum 20 from the center of the nanotube. The C11, C33, and K12 follow similar trends as a function of radial distance from the nanotube. The K13 decreases greater distances from the nanotube and becomes negative which may be a symptom of the statistical averaging.

Computational simulation of acoustic fatigue for hot composite structures

NASA Technical Reports Server (NTRS)

Singhal, S. N.; Nagpal, V. K.; Murthy, P. L. N.; Chamis, C. C.

1991-01-01

This paper presents predictive methods/codes for computational simulation of acoustic fatigue resistance of hot composite structures subjected to acoustic excitation emanating from an adjacent vibrating component. Select codes developed over the past two decades at the NASA Lewis Research Center are used. The codes include computation of (1) acoustic noise generated from a vibrating component, (2) degradation in material properties of the composite laminate at use temperature, (3) dynamic response of acoustically excited hot multilayered composite structure, (4) degradation in the first-ply strength of the excited structure due to acoustic loading, and (5) acoustic fatigue resistance of the excited structure, including propulsion environment. Effects of the laminate lay-up and environment on the acoustic fatigue life are evaluated. The results show that, by keeping the angled plies on the outer surface of the laminate, a substantial increase in the acoustic fatigue life is obtained. The effect of environment (temperature and moisure) is to relieve the residual stresses leading to an increase in the acoustic fatigue life of the excited panel.

Computational simulation of acoustic fatigue for hot composite structures

NASA Technical Reports Server (NTRS)

Singhal, Surendra N.; Murthy, Pappu L. N.; Chamis, Christos C.; Nagpal, Vinod K.; Sutjahjo, Edhi

1991-01-01

Predictive methods/computer codes for the computational simulation of acoustic fatigue resistance of hot composite structures subjected to acoustic excitation emanating from an adjacent vibrating component are discussed. Select codes developed over the past two decades at the NASA Lewis Research Center are used. The codes include computation of acoustic noise generated from a vibrating component, degradation in material properties of a composite laminate at use temperature, dynamic response of acoustically excited hot multilayered composite structure, degradation in the first ply strength of the excited structure due to acoustic loading, and acoustic fatigue resistance of the excited structure, including the propulsion environment. Effects of the laminate lay-up and environment on the acoustic fatigue life are evaluated. The results show that, by keeping the angled plies on the outer surface of the laminate, a substantial increase in the acoustic fatigue life is obtained. The effect of environment (temperature and moisture) is to relieve the residual stresses leading to an increase in the acoustic fatigue life of the excited panel.

Streamlining cardiovascular clinical trials to improve efficiency and generalisability.

PubMed

Zannad, Faiez; Pfeffer, Marc A; Bhatt, Deepak L; Bonds, Denise E; Borer, Jeffrey S; Calvo-Rojas, Gonzalo; Fiore, Louis; Lund, Lars H; Madigan, David; Maggioni, Aldo Pietro; Meyers, Catherine M; Rosenberg, Yves; Simon, Tabassome; Stough, Wendy Gattis; Zalewski, Andrew; Zariffa, Nevine; Temple, Robert

2017-08-01

Controlled trials provide the most valid determination of the efficacy and safety of an intervention, but large cardiovascular clinical trials have become extremely costly and complex, making it difficult to study many important clinical questions. A critical question, and the main objective of this review, is how trials might be simplified while maintaining randomisation to preserve scientific integrity and unbiased efficacy assessments. Experience with alternative approaches is accumulating, specifically with registry-based randomised controlled trials that make use of data already collected. This approach addresses bias concerns while still capitalising on the benefits and efficiencies of a registry. Several completed or ongoing trials illustrate the feasibility of using registry-based controlled trials to answer important questions relevant to daily clinical practice. Randomised trials within healthcare organisation databases may also represent streamlined solutions for some types of investigations, although data quality (endpoint assessment) is likely to be a greater concern in those settings. These approaches are not without challenges, and issues pertaining to informed consent, blinding, data quality and regulatory standards remain to be fully explored. Collaboration among stakeholders is necessary to achieve standards for data management and analysis, to validate large data sources for use in randomised trials, and to re-evaluate ethical standards to encourage research while also ensuring that patients are protected. The rapidly evolving efforts to streamline cardiovascular clinical trials have the potential to lead to major advances in promoting better care and outcomes for patients with cardiovascular disease. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2017. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

78 FR 57058 - Federal Housing Administration (FHA) Approval of Lending Institutions and Mortgagees: Streamlined...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-09-17

... federal banking agencies and reduce the cost of participating in FHA programs by releasing small... retained earnings, a statement of cash flows, an analysis of the lender's or mortgagee's net worth adjusted...: Streamlined Reporting Requirements for Small Supervised Lenders and Mortgagees AGENCY: Office of the Assistant...

76 FR 54792 - Comment Request for Information Collection for the Workforce Investment Act Streamlined...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-09-02

... organizations. Form(s): ETA-9131, ETA-9132, ETA 9133, WISRD Record Layout, WISPR Data Preparation and Reporting... Collection for the Workforce Investment Act Streamlined Performance Reporting (WISPR) Data Collection System... requested data can be provided in the desired format, reporting burden (time and financial resources) is...

West Virginia Peer Exchange : Streamlining Highway Safety Improvement Program Project Delivery - An RSPCB Peer Exchange

DOT National Transportation Integrated Search

2014-09-01

The West Virginia Division of Highways (WV DOH) hosted a Peer Exchange to share information and experiences for streamlining Highway Safety Improvement Program (HSIP) project delivery. The event was held September 23 to 24, 2014 in Charleston, West V...

Viscoelastic stability of resin-composites aged in food-simulating solvents.

PubMed

Marghalani, Hanadi Y; Watts, David C

2013-09-01

To study time-dependent viscoelastic deformation (creep and recovery) of resin-composites, after conditioning in food-simulating solvents, under a compressive stress at 37°C. Five dimethacrylate-based composites: (Spectrum TPH, Premise Body, Tetric Ceram HB, Filtek P60, X-tra fil), and two Ormocers (Experimental Ormocer V 28407, Admira) were studied. Three groups of cylindrical specimens (4mm×6mm) were prepared and then conditioned in 3 solvents: methyl ethyl ketone (MEK), ethanol, and water for 1 month at 37°C. The compressive creep-strain under 35MPa in 37°C water was recorded continuously for 2h and then the unloaded recovery-strain was monitored for another 2h. The data were analyzed by one-way ANOVA and Bonferroni's test. The materials all exhibited classic creep and recovery curves, with most parameters being significantly different (p<0.0001) for each solvent condition. All materials showed lower creep-strain in water than in ethanol or MEK solvents. Maximum creep-strain and permanent-set gave negative linear-regression (r(2)>0.98) with logarithm of the solvent solubility-parameter. The % mean (SD) creep-strain ranged from a minimum of 0.82 (0.01) for the Exp. Ormocer in water to the maximum of 4.19 (0.30) for Admira in MEK. Similar trends were found for permanent-set. The dimethacrylate-based composites behaved as an intermediate group, apart from X-tra fil that had similar stability to the Exp. Ormocer. The viscoelastic stability (low creep and permanent-set) of the Exp. Ormocer, compared to many dimethacrylate-based composites, in food-simulating solvents may be due to its diluent-free formulation. This was closely matched by a highly-filled dimethacrylate material (X-tra fil). Copyright © 2013 Academy of Dental Materials. All rights reserved.

Use of Vortex Generators to Reduce Distortion for Mach 1.6 Streamline-Traced Supersonic Inlets

NASA Technical Reports Server (NTRS)

Baydar, Ezgihan; Lu, Frank; Slater, John W.; Trefny, Chuck

2016-01-01

Reduce the total pressure distortion at the engine-fan face due to low-momentum flow caused by the interaction of an external terminal shock at the turbulent boundary layer along a streamline-traced external-compression (STEX) inlet for Mach 1.6.

78 FR 23178 - Federal Housing Administration (FHA) Approval of Lending Institutions and Mortgagees: Streamlined...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-04-18

... in line with that of the federal banking agencies and, as discussed above, reduce the cost of... earnings, a statement of cash flows, an analysis of the mortgagee's net worth adjusted to reflect only...: Streamlined Reporting Requirements for Small Supervised Lenders and Mortgagees AGENCY: Office of the Assistant...

24 CFR 903.12 - What are the streamlined Annual Plan requirements for small PHAs?

Code of Federal Regulations, 2010 CFR

2010-04-01

... Plan requirements for small PHAs? 903.12 Section 903.12 Housing and Urban Development Regulations... HOUSING, DEPARTMENT OF HOUSING AND URBAN DEVELOPMENT PUBLIC HOUSING AGENCY PLANS PHA Plans § 903.12 What are the streamlined Annual Plan requirements for small PHAs? (a) General. PHAs with less than 250...

Evaluation of intensity of artefacts in CBCT by radio-opacity of composite simulation models of implants in vitro

PubMed Central

Kuusisto, N; Vallittu, P K; Lassila, L V J

2015-01-01

Objectives: The aim was to compare the intensity of artefacts in CBCT images caused by different percentages of radio-opacifying material in composite simulation models of implants. Titanium and zirconia models of implants were used as a reference for the evaluation of the intensity of artefacts. Methods: Seven different percentages of radio-opacifying BaAlSiO2 fillers were added to composite resin to fabricate seven step wedges and simulation models of implants. Titanium and zirconia simulation models of implants were also fabricated. Aluminium step wedge was used as a reference for the measurement of grey values in intraoral radiographs. Step wedges were exposed with a Planmeca Intra X-ray machine (Planmeca Oy, Helsinki, Finland). All composite, titanium and zirconia simulation models of implants were exposed with a SCANORA® 3D dental X-ray machine (Soredex, Tuusula, Finland). Images and grey values were analysed with ImageJ software (National Institutes of Health, Bethesda, MD). To demonstrate possible artefacts between all the simulation models of implants, the images were also visually compared with each other using ImageJ software. Results: Artefacts were clearly present in CBCT images caused by titanium and zirconia and when the composite material consisted at least 20% BaAlSiO2. The intensity of artefacts increased when the radio-opacity of the composite material increased. Conclusions: Materials containing less radio-opacity produce less pronounced artefacts. The cut-off point for artefacts is at 20% radio-opaque filling material in composite material. PMID:25283364

SUPG Finite Element Simulations of Compressible Flows for Aerothermodynamic Applications

NASA Technical Reports Server (NTRS)

Kirk, Benjamin S.

2007-01-01

This viewgraph presentation reviews the Streamline-Upwind Petrov-Galerkin (SUPG) Finite Element Simulation. It covers the background, governing equations, weak formulation, shock capturing, inviscid flux discretization, time discretization, linearization, and implicit solution strategies. It also reviews some applications such as Type IV Shock Interaction, Forward-Facing Cavity and AEDC Sharp Double Cone.

Simulation of Low Velocity Impact Induced Inter- and Intra-Laminar Damage of Composite Beams Based on XFEM

NASA Astrophysics Data System (ADS)

Sun, Wei; Guan, Zhidong; Li, Zengshan

2017-12-01

In this paper, the Inter-Fiber Fracture (IFF) criterion of Puck failure theory based on the eXtended Finite Element Method (XFEM) was implemented in ABAQUS code to predict the intra-laminar crack initiation of unidirectional (UD) composite laminate. The transverse crack path in the matrix can be simulated accurately by the presented method. After the crack initiation, the propagation of the crack is simulated by Cohesive Zoom Model (CZM), in which the displacement discontinuities and stress concentration caused by matrix crack is introduced into the finite element (FE) model. Combined with the usage of the enriched element interface, which can be used to simulate the inter-laminar delamination crack, the Low Velocity Impact (LVI) induced damage of UD composite laminate beam with a typical stacking of composite laminates [05/903]S is studied. A complete crack initiation and propagation process was simulated and the numerical results obtained by the XFEM are consistent with the experimental results.

Simulating Progressive Damage of Notched Composite Laminates with Various Lamination Schemes

NASA Astrophysics Data System (ADS)

Mandal, B.; Chakrabarti, A.

2017-05-01

A three dimensional finite element based progressive damage model has been developed for the failure analysis of notched composite laminates. The material constitutive relations and the progressive damage algorithms are implemented into finite element code ABAQUS using user-defined subroutine UMAT. The existing failure criteria for the composite laminates are modified by including the failure criteria for fiber/matrix shear damage and delamination effects. The proposed numerical model is quite efficient and simple compared to other progressive damage models available in the literature. The efficiency of the present constitutive model and the computational scheme is verified by comparing the simulated results with the results available in the literature. A parametric study has been carried out to investigate the effect of change in lamination scheme on the failure behaviour of notched composite laminates.

Modeling and Simulation of Voids in Composite Tape Winding Process Based on Domain Superposition Technique

NASA Astrophysics Data System (ADS)

Deng, Bo; Shi, Yaoyao

2017-11-01

The tape winding technology is an effective way to fabricate rotationally composite materials. Nevertheless, some inevitable defects will seriously influence the performance of winding products. One of the crucial ways to identify the quality of fiber-reinforced composite material products is examining its void content. Significant improvement in products' mechanical properties can be achieved by minimizing the void defect. Two methods were applied in this study, finite element analysis and experimental testing, respectively, to investigate the mechanism of how void forming in composite tape winding processing. Based on the theories of interlayer intimate contact and Domain Superposition Technique (DST), a three-dimensional model of prepreg tape void with SolidWorks has been modeled in this paper. Whereafter, ABAQUS simulation software was used to simulate the void content change with pressure and temperature. Finally, a series of experiments were performed to determine the accuracy of the model-based predictions. The results showed that the model is effective for predicting the void content in the composite tape winding process.

Localized and generalized simulated wear of resin composites.

PubMed

Barkmeier, W W; Takamizawa, T; Erickson, R L; Tsujimoto, A; Latta, M; Miyazaki, M

2015-01-01

A laboratory study was conducted to examine the wear of resin composite materials using both a localized and generalized wear simulation model. Twenty specimens each of seven resin composites (Esthet•X HD [HD], Filtek Supreme Ultra [SU], Herculite Ultra [HU], SonicFill [SF], Tetric EvoCeram Bulk Fill [TB], Venus Diamond [VD], and Z100 Restorative [Z]) were subjected to a wear challenge of 400,000 cycles for both localized and generalized wear in a Leinfelder-Suzuki wear simulator (Alabama machine). The materials were placed in custom cylinder-shaped stainless steel fixtures. A stainless steel ball bearing (r=2.387 mm) was used as the antagonist for localized wear, and a stainless steel, cylindrical antagonist with a flat tip was used for generalized wear. A water slurry of polymethylmethacrylate (PMMA) beads was used as the abrasive media. A noncontact profilometer (Proscan 2100) with Proscan software was used to digitize the surface contours of the pretest and posttest specimens. AnSur 3D software was used for wear assessment. For localized testing, maximum facet depth (μm) and volume loss (mm(3)) were used to compare the materials. The mean depth of the facet surface (μm) and volume loss (mm(3)) were used for comparison of the generalized wear specimens. A one-way analysis of variance (ANOVA) and Tukey post hoc test were used for data analysis of volume loss for both localized and generalized wear, maximum facet depth for localized wear, and mean depth of the facet for generalized wear. The results for localized wear simulation were as follows [mean (standard deviation)]: maximum facet depth (μm)--Z, 59.5 (14.7); HU, 99.3 (16.3); SU, 102.8 (13.8); HD, 110.2 (13.3); VD, 114.0 (10.3); TB, 125.5 (12.1); SF, 195.9 (16.9); volume loss (mm(3))--Z, 0.013 (0.002); SU, 0.026 (0.006); HU, 0.043 (0.008); VD, 0.057 (0.009); HD, 0.058 (0.014); TB, 0.061 (0.010); SF, 0.135 (0.024). Generalized wear simulation results were as follows: mean depth of facet (μm)--Z, 9.3 (3

Basal streamline sprays for hardwood resprout control: herbicides, concentrations, and streaks per stem

Treesearch

James H. Miller

1997-01-01

Basal streamline sprays were tested to control sweetgum, water oak, and southern red oak that ranged from 0.5 to 2 inches groundline diameter. Primary test herbicides and mixtures were triclopyr (Garlon 4) at 20 and 40 percent mixed with 10 percent d-limonene (Cide-Kick) and the remainder diesel; and imazapyr (Chopper) at 5 and 10 percent mixed in only diesel. Primary...

Design and simulation on the morphing composite propeller (Conference Presentation)

NASA Astrophysics Data System (ADS)

Chen, Fanlong; Li, Qinyu; Liu, Liwu; Lan, Xin; Liu, Yanju; Leng, Jinsong

2017-04-01

As one of the most crucial part of the unmanned underwater vehicle (UUV), the composite propeller plays an important role on the UUV's performance. As the composite propeller behaves excellent properties in hydroelastic facet and acoustic suppression, it attracts increasing attentions all over the globe. This paper goes a step further based on this idea, and comes up with a novel concept of "morphing composite propeller" (MCP) to improve the performance of the conventional composite propeller (CCP) to anticipate the improved propeller can perform better to propel the UUV. Based on the new concept, a novel MCP is designed. Each blade of the propeller is assembled with an active rotatable flap (ARF) to change the blade's local camber with flap rotation. Then the transmission mechanism (TM) has been designed and housed in the propeller blade to push the ARF. With the ARF rotating, the UUV can be propelled by different thrusts under certain rotation velocities of the propeller. Based on the design, the Fluent is exploited to analyze the fluid dynamics around the propeller. Finally, based on the design and hydrodynamic analysis, the structural response for the novel morphing composite propeller is calculated. The propeller blade is simplified and layered with composite materials. And the structure response of an MCP is obtained with various rotation angle under the hydrodynamic pressure. This simulation can instruct the design and fabrication techniques of the MCP.

Simulating Future GPS Clock Scenarios with Two Composite Clock Algorithms

NASA Technical Reports Server (NTRS)

Suess, Matthias; Matsakis, Demetrios; Greenhall, Charles A.

2010-01-01

Using the GPS Toolkit, the GPS constellation is simulated using 31 satellites (SV) and a ground network of 17 monitor stations (MS). At every 15-minutes measurement epoch, the monitor stations measure the time signals of all satellites above a parameterized elevation angle. Once a day, the satellite clock estimates the station and satellite clocks. The first composite clock (B) is based on the Brown algorithm, and is now used by GPS. The second one (G) is based on the Greenhall algorithm. The composite clock of G and B performance are investigated using three ground-clock models. Model C simulates the current GPS configuration, in which all stations are equipped with cesium clocks, except for masers at USNO and Alternate Master Clock (AMC) sites. Model M is an improved situation in which every station is equipped with active hydrogen masers. Finally, Models F and O are future scenarios in which the USNO and AMC stations are equipped with fountain clocks instead of masers. Model F is a rubidium fountain, while Model O is more precise but futuristic Optical Fountain. Each model is evaluated using three performance metrics. The timing-related user range error having all satellites available is the first performance index (PI1). The second performance index (PI2) relates to the stability of the broadcast GPS system time itself. The third performance index (PI3) evaluates the stability of the time scales computed by the two composite clocks. A distinction is made between the "Signal-in-Space" accuracy and that available through a GNSS receiver.

An Enriched Shell Element for Delamination Simulation in Composite Laminates

NASA Technical Reports Server (NTRS)

McElroy, Mark

2015-01-01

A formulation is presented for an enriched shell finite element capable of delamination simulation in composite laminates. The element uses an adaptive splitting approach for damage characterization that allows for straightforward low-fidelity model creation and a numerically efficient solution. The Floating Node Method is used in conjunction with the Virtual Crack Closure Technique to predict delamination growth and represent it discretely at an arbitrary ply interface. The enriched element is verified for Mode I delamination simulation using numerical benchmark data. After determining important mesh configuration guidelines for the vicinity of the delamination front in the model, a good correlation was found between the enriched shell element model results and the benchmark data set.

Development of a Neural Network Simulator for Studying the Constitutive Behavior of Structural Composite Materials

DOE PAGES

Na, Hyuntae; Lee, Seung-Yub; Üstündag, Ersan; ...

2013-01-01

This paper introduces a recent development and application of a noncommercial artificial neural network (ANN) simulator with graphical user interface (GUI) to assist in rapid data modeling and analysis in the engineering diffraction field. The real-time network training/simulation monitoring tool has been customized for the study of constitutive behavior of engineering materials, and it has improved data mining and forecasting capabilities of neural networks. This software has been used to train and simulate the finite element modeling (FEM) data for a fiber composite system, both forward and inverse. The forward neural network simulation precisely reduplicates FEM results several orders ofmore » magnitude faster than the slow original FEM. The inverse simulation is more challenging; yet, material parameters can be meaningfully determined with the aid of parameter sensitivity information. The simulator GUI also reveals that output node size for materials parameter and input normalization method for strain data are critical train conditions in inverse network. The successful use of ANN modeling and simulator GUI has been validated through engineering neutron diffraction experimental data by determining constitutive laws of the real fiber composite materials via a mathematically rigorous and physically meaningful parameter search process, once the networks are successfully trained from the FEM database.« less

Expected Benefits of Streamlining Undergraduate Medical Education by Early Commitment to Specific Medical Specialties

ERIC Educational Resources Information Center

Benbassat, Jochanan; Baumal, Reuben

2012-01-01

Undergraduate medical education is too long; it does not meet the needs for physicians' workforce; and its content is inconsistent with the job characteristics of some of its graduates. In this paper we attempt to respond to these problems by streamlining medical education along the following three reforms. First, high school graduates would be…

Streamlining plant sample preparation: the use of high-throughput robotics to process echinacea samples for biomarker profiling by MALDI-TOF mass spectrometry.

PubMed

Greene, Leasa A; Isaac, Issa; Gray, Dean E; Schwartz, Sarah A

2007-09-01

Several species in the genus Echinacea are beneficial herbs popularly used for many ailments. The most popular Echinacea species for cultivation, wild collection, and herbal products include E. purpurea (L.) Moench, E. pallida (Nutt.) Nutt., and E. angustifolia (DC). Product adulteration is a key concern for the natural products industry, where botanical misidentification and introduction of other botanical and nonbotanical contaminants exist throughout the formulation and production process. Therefore, rapid and cost-effective methods that can be used to monitor these materials for complex product purity and consistency are of benefit to consumers and producers. The objective of this continuing research was to develop automated, high-throughput processing methods that, teamed with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) analysis, differentiate Echinacea species by their mass profiles. Small molecules, peptide, and proteins from aerial parts (leaf/stem/flowers), seeds, and roots from E. purpurea and E. angustifolia; seeds and roots from E. pallida; and off-the-shelf Echinacea supplements were extracted and analyzed by MS using methods developed on the ProPrep liquid handling system (Genomic Solutions). Analysis of these samples highlighted key MS signal patterns from both small molecules and proteins that characterized the individual Echinacea materials analyzed. Based on analysis of pure Echinacea samples, off-the-shelf products containing Echinacea could then be evaluated in a streamlined process. Corresponding analysis of dietary supplements was used to monitor for product composition, including Echinacea species and plant materials used. These results highlight the potential for streamlined, automated approaches for agricultural species differentiation and botanical product evaluation.

A Selection of Composites Simulation Practices at NASA Langley Research Center

NASA Technical Reports Server (NTRS)

Ratcliffe, James G.

2007-01-01

One of the major areas of study at NASA Langley Research Center is the development of technologies that support the use of advanced composite materials in aerospace applications. Amongst the supporting technologies are analysis tools used to simulate the behavior of these materials. This presentation will discuss a number of examples of analysis tools and simulation practices conducted at NASA Langley. The presentation will include examples of damage tolerance analyses for both interlaminar and intralaminar failure modes. Tools for modeling interlaminar failure modes include fracture mechanics and cohesive methods, whilst tools for modeling intralaminar failure involve the development of various progressive failure analyses. Other examples of analyses developed at NASA Langley include a thermo-mechanical model of an orthotropic material and the simulation of delamination growth in z-pin reinforced laminates.

BLIMPK/Streamline Surface Catalytic Heating Predictions on the Space Shuttle Orbiter

NASA Technical Reports Server (NTRS)

Marichalar, Jeremiah J.; Rochelle, William C.; Kirk, Benjamin S.; Campbell, Charles H.

2006-01-01

This paper describes the results of an analysis of localized catalytic heating effects to the U.S. Space Shuttle Orbiter Thermal Protection System (TPS). The analysis applies to the High-temperature Reusable Surface Insulation (HRSI) on the lower fuselage and wing acreage, as well as the critical Reinforced Carbon-Carbon on the nose cap, chin panel and the wing leading edge. The object of the analysis was to use a modified two-layer approach to predict the catalytic heating effects on the Orbiter windward HRSI tile acreage, nose cap, and wing leading edge assuming localized highly catalytic or fully catalytic surfaces. The method incorporated the Boundary Layer Integral Matrix Procedure Kinetic (BLIMPK) code with streamline inputs from viscous Navier-Stokes solutions to produce heating rates for localized fully catalytic and highly catalytic surfaces as well as for nominal partially catalytic surfaces (either Reinforced Carbon-Carbon or Reaction Cured Glass) with temperature-dependent recombination coefficients. The highly catalytic heating results showed very good correlation with Orbiter Experiments STS-2, -3, and -5 centerline and STS-5 wing flight data for the HRSI tiles. Recommended catalytic heating factors were generated for use in future Shuttle missions in the event of quick-time analysis of damaged or repaired TPS areas during atmospheric reentry. The catalytic factors are presented along the streamlines as well as a function of stagnation enthalpy so they can be used for arbitrary trajectories.

Experimental testing and numerical simulation on natural composite for aerospace applications

NASA Astrophysics Data System (ADS)

Kumar, G. Raj; Vijayanandh, R.; Kumar, M. Senthil; Kumar, S. Sathish

2018-05-01

Nowadays polymers are commonly used in various applications, which make it difficult to avoid its usage even though it causes environmental problems. Natural fibers are best alternate to overcome the polymer based environmental issues. Natural fibers play an important role in developing high performing fully newline biodegradable green composites which will be a key material to solve environmental problems in future. In this paper deals the properties analysis of banana fiber is combined with epoxy resin in order to create a natural composite, which has special characteristics for aerospace applications. The objective of this paper is to investigate the characteristics of failure modes and strength of natural composite using experimental and numerical methods. The test specimen of natural composite has been fabricated as per ASTM standard, which undergoes tensile and compression tests using Tinius Olsen UTM in order to determine mechanical and physical properties. The reference model has been designed by CATIA, and then numerical simulation has been carried out by Ansys Workbench 16.2 for the given boundary conditions.

Computational simulation of the creep-rupture process in filamentary composite materials

NASA Technical Reports Server (NTRS)

Slattery, Kerry T.; Hackett, Robert M.

1991-01-01

A computational simulation of the internal damage accumulation which causes the creep-rupture phenomenon in filamentary composite materials is developed. The creep-rupture process involves complex interactions between several damage mechanisms. A statistically-based computational simulation using a time-differencing approach is employed to model these progressive interactions. The finite element method is used to calculate the internal stresses. The fibers are modeled as a series of bar elements which are connected transversely by matrix elements. Flaws are distributed randomly throughout the elements in the model. Load is applied, and the properties of the individual elements are updated at the end of each time step as a function of the stress history. The simulation is continued until failure occurs. Several cases, with different initial flaw dispersions, are run to establish a statistical distribution of the time-to-failure. The calculations are performed on a supercomputer. The simulation results compare favorably with the results of creep-rupture experiments conducted at the Lawrence Livermore National Laboratory.

Finite Element Simulation of Compression Molding of Woven Fabric Carbon Fiber/Epoxy Composites: Part I Material Model Development

DOE PAGES

Li, Yang; Zhao, Qiangsheng; Mirdamadi, Mansour; ...

2016-01-06

Woven fabric carbon fiber/epoxy composites made through compression molding are one of the promising choices of material for the vehicle light-weighting strategy. Previous studies have shown that the processing conditions can have substantial influence on the performance of this type of the material. Therefore the optimization of the compression molding process is of great importance to the manufacturing practice. An efficient way to achieve the optimized design of this process would be through conducting finite element (FE) simulations of compression molding for woven fabric carbon fiber/epoxy composites. However, performing such simulation remains a challenging task for FE as multiple typesmore » of physics are involved during the compression molding process, including the epoxy resin curing and the complex mechanical behavior of woven fabric structure. In the present study, the FE simulation of the compression molding process of resin based woven fabric composites at continuum level is conducted, which is enabled by the implementation of an integrated material modeling methodology in LS-Dyna. Specifically, the chemo-thermo-mechanical problem of compression molding is solved through the coupling of three material models, i.e., one thermal model for temperature history in the resin, one mechanical model to update the curing-dependent properties of the resin and another mechanical model to simulate the behavior of the woven fabric composites. Preliminary simulations of the carbon fiber/epoxy woven fabric composites in LS-Dyna are presented as a demonstration, while validations and models with real part geometry are planned in the future work.« less

Compositional differences in simulated root exudates elicit a limited functional and compositional response in soil microbial communities.

PubMed

Strickland, Michael S; McCulley, Rebecca L; Nelson, Jim A; Bradford, Mark A

2015-01-01

Inputs of low molecular weight carbon (LMW-C) to soil - primarily via root exudates- are expected to be a major driver of microbial activity and source of stable soil organic carbon. It is expected that variation in the type and composition of LMW-C entering soil will influence microbial community composition and function. If this is the case then short-term changes in LMW-C inputs may alter processes regulated by these communities. To determine if change in the composition of LMW-C inputs influences microbial community function and composition, we conducted a 90 day microcosm experiment whereby soils sourced from three different land covers (meadows, deciduous forests, and white pine stands) were amended, at low concentrations, with one of eight simulated root exudate treatments. Treatments included no addition of LMW-C, and the full factorial combination of glucose, glycine, and oxalic acid. After 90 days, we conducted a functional response assay and determined microbial composition via phospholipid fatty acid analysis. Whereas we noted a statistically significant effect of exudate treatments, this only accounted for ∼3% of the variation observed in function. In comparison, land cover and site explained ∼46 and ∼41% of the variation, respectively. This suggests that exudate composition has little influence on function compared to site/land cover specific factors. Supporting the finding that exudate effects were minor, we found that an absence of LMW-C elicited the greatest difference in function compared to those treatments receiving any LMW-C. Additionally, exudate treatments did not alter microbial community composition and observable differences were instead due to land cover. These results confirm the strong effects of land cover/site legacies on soil microbial communities. In contrast, short-term changes in exudate composition, at meaningful concentrations, may have little impact on microbial function and composition.

Reduced-Order Models Based on POD-Tpwl for Compositional Subsurface Flow Simulation

NASA Astrophysics Data System (ADS)

Durlofsky, L. J.; He, J.; Jin, L. Z.

2014-12-01

A reduced-order modeling procedure applicable for compositional subsurface flow simulation will be described and applied. The technique combines trajectory piecewise linearization (TPWL) and proper orthogonal decomposition (POD) to provide highly efficient surrogate models. The method is based on a molar formulation (which uses pressure and overall component mole fractions as the primary variables) and is applicable for two-phase, multicomponent systems. The POD-TPWL procedure expresses new solutions in terms of linearizations around solution states generated and saved during previously simulated 'training' runs. High-dimensional states are projected into a low-dimensional subspace using POD. Thus, at each time step, only a low-dimensional linear system needs to be solved. Results will be presented for heterogeneous three-dimensional simulation models involving CO2 injection. Both enhanced oil recovery and carbon storage applications (with horizontal CO2 injectors) will be considered. Reasonably close agreement between full-order reference solutions and compositional POD-TPWL simulations will be demonstrated for 'test' runs in which the well controls differ from those used for training. Construction of the POD-TPWL model requires preprocessing overhead computations equivalent to about 3-4 full-order runs. Runtime speedups using POD-TPWL are, however, very significant - typically O(100-1000). The use of POD-TPWL for well control optimization will also be illustrated. For this application, some amount of retraining during the course of the optimization is required, which leads to smaller, but still significant, speedup factors.

Aerogel to simulate delamination and porosity defects in carbon-fiber reinforced polymer composites

NASA Astrophysics Data System (ADS)

Juarez, Peter; Leckey, Cara A. C.

2018-04-01

Representative defect standards are essential for the validation and calibration of new and existing inspection techniques. However, commonly used methods of simulating delaminations in carbon-fiber reinforced polymer (CFRP) composites do not accurately represent the behavior of the real-world defects for several widely-used NDE techniques. For instance, it is common practice to create a delamination standard by inserting Polytetrafluoroethylene (PTFE) in between ply layers. However, PTFE can transmit more ultrasonic energy than actual delaminations, leading to an unrealistic representation of the defect inspection. PTFE can also deform/wrinkle during the curing process and has a thermal effusivity two orders of magnitude higher than air (almost equal to that of a CFRP). It is therefore not effective in simulating a delamination for thermography. Currently there is also no standard practice for producing or representing a known porosity in composites. This paper presents a novel method of creating delamination and porosity standards using aerogel. Insertion of thin sheets of solid aerogel between ply layers during layup is shown to produce air-gap-like delaminations creating realistic ultrasonic and thermographic inspection responses. Furthermore, it is shown that depositing controlled amounts of aerogel powder can represent porosity. Micrograph data verifies the structural integrity of the aerogel through the composite curing process. This paper presents data from multiple NDE methods, including X-ray computed tomography, immersion ultrasound, and flash thermography to the effectiveness of aerogel as a delamination and porosity simulant.

Multi-faceted informatics system for digitising and streamlining the reablement care model.

PubMed

Bond, Raymond R; Mulvenna, Maurice D; Finlay, Dewar D; Martin, Suzanne

2015-08-01

Reablement is new paradigm to increase independence in the home amongst the ageing population. And it remains a challenge to design an optimal electronic system to streamline and integrate reablement into current healthcare infrastructure. Furthermore, given reablement requires collaboration with a range of organisations (including national healthcare institutions and community/voluntary service providers), such a system needs to be co-created with all stakeholders involved. Thus, the purpose of this study is, (1) to bring together stakeholder groups to elicit a comprehensive set of requirements for a digital reablement system, (2) to utilise emerging technologies to implement a system and a data model based on the requirements gathered and (3) to involve user groups in a usability assessment of the system. In this study we employed a mixed qualitative approach that included a series of stakeholder-involved activities. Collectively, 73 subjects were recruited to participate in an ideation event, a quasi-hackathon and a usability study. The study unveiled stakeholder-led requirements, which resulted in a novel cloud-based system that was created using emerging web technologies. The system is driven by a unique data model and includes interactive features that are necessary for streamlining the reablement care model. In summary, this system allows community based interventions (or services) to be prescribed to occupants whilst also monitoring the occupant's progress of independent living. Copyright © 2015 Elsevier Inc. All rights reserved.

Numerical Simulations of As-Extruded Mg Matrix Composites Interpenetrated by Metal Reinforcement

NASA Astrophysics Data System (ADS)

Y Wang, H.; Wang, S. R.; Yang, X. F.; Li, P.

2017-12-01

The interpenetrating magnesium composites reinforced by three-dimensional braided stainless steel wire reinforcement were fabricated and investigated. The extrusion processes of the composites in different conditions were carried out and simulated by finite element method using the DEFORM-3D software. The results show that the matrix and reinforcement of the composites form a good interfacial bonding and the grains were refined by extrusion and the influence of reinforcement, which are in accordance with the enhanced strength and degraded plasticity. The combined quality between the matrix and reinforcement can be strengthened in extrusion chamber where occurred large strain and suffered intense stress, and the effective stress of the material increases continuously with the increase in extrusion ratio and the decrease in extrusion speed until it reaches a stable value.

24 CFR 903.11 - Are certain PHAs eligible to submit a streamlined Annual Plan?

Code of Federal Regulations, 2010 CFR

2010-04-01

... streamlined Annual Plan must include the information required by § 903.7(a), (b), (c), (d), (g), (h), (k), (m), (n), (o), (p) and (r). The information required by § 903.7(m) must be included only to the extent... § 903.7(a), (b), (c), (d), (e), (f), (k), (l), (o), (p) and (r). [65 FR 49484, Aug. 14, 2000, as amended...

Simulating the Response of a Composite Honeycomb Energy Absorber. Part 2; Full-Scale Impact Testing

NASA Technical Reports Server (NTRS)

Fasanella, Edwin L.; Annett, Martin S.; Jackson, Karen E.; Polanco, Michael A.

2012-01-01

NASA has sponsored research to evaluate an externally deployable composite honeycomb designed to attenuate loads in the event of a helicopter crash. The concept, designated the Deployable Energy Absorber (DEA), is an expandable Kevlar(Registered TradeMark) honeycomb. The DEA has a flexible hinge that allows the honeycomb to be stowed collapsed until needed during an emergency. Evaluation of the DEA began with material characterization of the Kevlar(Registered TradeMark)-129 fabric/epoxy, and ended with a full-scale crash test of a retrofitted MD-500 helicopter. During each evaluation phase, finite element models of the test articles were developed and simulations were performed using the dynamic finite element code, LS-DYNA(Registered TradeMark). The paper will focus on simulations of two full-scale impact tests involving the DEA, a mass-simulator and a full-scale crash of an instrumented MD-500 helicopter. Isotropic (MAT24) and composite (MAT58) material models, which were assigned to DEA shell elements, were compared. Based on simulations results, the MAT58 model showed better agreement with test.

Feasibility of generating quantitative composition images in dual energy mammography: a simulation study

NASA Astrophysics Data System (ADS)

Lee, Donghoon; Kim, Ye-seul; Choi, Sunghoon; Lee, Haenghwa; Choi, Seungyeon; Kim, Hee-Joung

2016-03-01

Breast cancer is one of the most common malignancies in women. For years, mammography has been used as the gold standard for localizing breast cancer, despite its limitation in determining cancer composition. Therefore, the purpose of this simulation study is to confirm the feasibility of obtaining tumor composition using dual energy digital mammography. To generate X-ray sources for dual energy mammography, 26 kVp and 39 kVp voltages were generated for low and high energy beams, respectively. Additionally, the energy subtraction and inverse mapping functions were applied to provide compositional images. The resultant images showed that the breast composition obtained by the inverse mapping function with cubic fitting achieved the highest accuracy and least noise. Furthermore, breast density analysis with cubic fitting showed less than 10% error compare to true values. In conclusion, this study demonstrated the feasibility of creating individual compositional images and capability of analyzing breast density effectively.

Streamlined islands and the English Channel megaflood hypothesis

NASA Astrophysics Data System (ADS)

Collier, J. S.; Oggioni, F.; Gupta, S.; García-Moreno, D.; Trentesaux, A.; De Batist, M.

2015-12-01

Recognising ice-age catastrophic megafloods is important because they had significant impact on large-scale drainage evolution and patterns of water and sediment movement to the oceans, and likely induced very rapid, short-term effects on climate. It has been previously proposed that a drainage system on the floor of the English Channel was initiated by catastrophic flooding in the Pleistocene but this suggestion has remained controversial. Here we examine this hypothesis through an analysis of key landform features. We use a new compilation of multi- and single-beam bathymetry together with sub-bottom profiler data to establish the internal structure, planform geometry and hence origin of a set of 36 mid-channel islands. Whilst there is evidence of modern-day surficial sediment processes, the majority of the islands can be clearly demonstrated to be formed of bedrock, and are hence erosional remnants rather than depositional features. The islands display classic lemniscate or tear-drop outlines, with elongated tips pointing downstream, typical of streamlined islands formed during high-magnitude water flow. The length-to-width ratio for the entire island population is 3.4 ± 1.3 and the degree-of-elongation or k-value is 3.7 ± 1.4. These values are comparable to streamlined islands in other proven Pleistocene catastrophic flood terrains and are distinctly different to values found in modern-day rivers. The island geometries show a correlation with bedrock type: with those carved from Upper Cretaceous chalk having larger length-to-width ratios (3.2 ± 1.3) than those carved into more mixed Paleogene terrigenous sandstones, siltstones and mudstones (3.0 ± 1.5). We attribute these differences to the former rock unit having a lower skin friction which allowed longer island growth to achieve minimum drag. The Paleogene islands, although less numerous than the Chalk islands, also assume more perfect lemniscate shapes. These lithologies therefore reached island

Strength Analysis and Process Simulation of Subway Contact Rail Support Bracket of Composite Materials

NASA Astrophysics Data System (ADS)

Fedulov, Boris N.; Safonov, Alexander A.; Sergeichev, Ivan V.; Ushakov, Andrey E.; Klenin, Yuri G.; Makarenko, Irina V.

2016-10-01

An application of composites for construction of subway brackets is a very effective approach to extend their lifetime. However, this approach involves the necessity to prevent process-induced distortions of the bracket due to thermal deformation and chemical shrinkage. At present study, a process simulation has been carried out to support the design of the production tooling. The simulation was based on the application of viscoelastic model for the resin. Simulation results were verified by comparison with results of manufacturing experiments. To optimize the bracket structure the strength analysis was carried out as well.

An Overview of the Distributed Space Exploration Simulation (DSES) Project

NASA Technical Reports Server (NTRS)

Crues, Edwin Z.; Chung, Victoria I.; Blum, Michael G.; Bowman, James D.

2007-01-01

This paper describes the Distributed Space Exploration Simulation (DSES) Project, a research and development collaboration between NASA centers which investigates technologies, and processes related to integrated, distributed simulation of complex space systems in support of NASA's Exploration Initiative. In particular, it describes the three major components of DSES: network infrastructure, software infrastructure and simulation development. With regard to network infrastructure, DSES is developing a Distributed Simulation Network for use by all NASA centers. With regard to software, DSES is developing software models, tools and procedures that streamline distributed simulation development and provide an interoperable infrastructure for agency-wide integrated simulation. Finally, with regard to simulation development, DSES is developing an integrated end-to-end simulation capability to support NASA development of new exploration spacecraft and missions. This paper presents the current status and plans for these three areas, including examples of specific simulations.

Report: Follow-Up Report: EPA Proposes to Streamline the Review, Management and Disposal of Hazardous Waste Pharmaceuticals

EPA Pesticide Factsheets

Report #15-P-0260, August 19, 2015. EPA states that it intends to issue a proposed rule, Management Standards for Hazardous Waste, which will attempt to streamline the approach to managing and disposing of hazardous and nonhazardous pharmaceutical waste.

3D finite element simulation of non-crimp fabric composites ultrasonic testing

NASA Astrophysics Data System (ADS)

Liu, Z.; Saffari, N.; Fromme, P.

2012-05-01

Composite materials offer many advantages for aerospace applications, e.g., good strength to weight ratio. Different types of composites, such as non-crimp fabrics (NCF), are currently being investigated as they offer reduced manufacturing costs and improved damage tolerance as compared to traditional pre-impregnated composite materials. NCF composites are made from stitched fiber bundles (tows), which typically have a width and thickness of less than a millimeter. This results in strongly inhomogeneous and anisotropic material properties. Different types of manufacturing imperfections, such as porosity, resin pockets, tow crimp and misalignment can lead to reduced material strength and thus to defects following excessive loads or impact, e.g., fracture and delaminations. The ultrasonic non-destructive testing of NCF composites is difficult, as the tow size is comparable to the wavelength, leading to multiple scattering in this inherently three-dimensional structure. For typical material properties and geometry of an NCF composite, a full three-dimensional Finite Element (FE) model has been developed in ABAQUS. The propagation of longitudinal ultrasonic waves has been simulated and the effect of multiple scattering at the fiber tows investigated. The influence of porosity in the epoxy matrix as a typical manufacturing defect on the ultrasonic wave propagation and attenuation has been studied.

Dynamic analysis of bulk-fill composites: Effect of food-simulating liquids.

PubMed

Eweis, Ahmed Hesham; Yap, Adrian U-Jin; Yahya, Noor Azlin

2017-10-01

This study investigated the effect of food simulating liquids on visco-elastic properties of bulk-fill restoratives using dynamic mechanical analysis. One conventional composite (Filtek Z350 [FZ]), two bulk-fill composites (Filtek Bulk-fill [FB] and Tetric N Ceram [TN]) and a bulk-fill giomer (Beautifil-Bulk Restorative [BB]) were evaluated. Specimens (12 × 2 × 2mm) were fabricated using customized stainless steel molds. The specimens were light-cured, removed from their molds, finished, measured and randomly divided into six groups. The groups (n = 10) were conditioned in the following mediums for 7 days at 37°C: air (control), artificial saliva (SAGF), distilled water, 0.02N citric acid, heptane, 50% ethanol-water solution. Specimens were assessed using dynamic mechanical testing in flexural three-point bending mode and their respective mediums at 37°C and a frequency range of 0.1-10Hz. The distance between the supports were fixed at 10mm and an axial load of 5N was employed. Data for elastic modulus, viscous modulus and loss tangent were subjected to ANOVA/Tukey's tests at significance level p < 0.05. Significant differences in visco-elastic properties were observed between materials and mediums. Apart from bulk-fill giomer, elastic modulus was the highest after conditioning in heptane. No apparent trends were noted for viscous modulus. Generally, loss tangent was the highest after conditioning in ethanol. The effect of food-simulating liquids on the visco-elastic properties of bulk-fill composites was material and medium dependent. Copyright © 2017 Elsevier Ltd. All rights reserved.

Experimental evaluation and simulation of volumetric shrinkage and warpage on polymeric composite reinforced with short natural fibers

NASA Astrophysics Data System (ADS)

Santos, Jonnathan D.; Fajardo, Jorge I.; Cuji, Alvaro R.; García, Jaime A.; Garzón, Luis E.; López, Luis M.

2015-09-01

A polymeric natural fiber-reinforced composite is developed by extrusion and injection molding process. The shrinkage and warpage of high-density polyethylene reinforced with short natural fibers of Guadua angustifolia Kunth are analyzed by experimental measurements and computer simulations. Autodesk Moldflow® and Solid Works® are employed to simulate both volumetric shrinkage and warpage of injected parts at different configurations: 0 wt.%, 20 wt.%, 30 wt.% and 40 wt.% reinforcing on shrinkage and warpage behavior of polymer composite. Become evident the restrictive effect of reinforcing on the volumetric shrinkage and warpage of injected parts. The results indicate that volumetric shrinkage of natural composite is reduced up to 58% with fiber increasing, whereas the warpage shows a reduction form 79% to 86% with major fiber content. These results suggest that it is a highly beneficial use of natural fibers to improve the assembly properties of polymeric natural fiber-reinforced composites.

Simulation and Experimental Study on Surface Formation Mechanism in Machining of SiCp/Al Composites

NASA Astrophysics Data System (ADS)

Du, Jinguang; Zhang, Haizhen; He, Wenbin; Ma, Jun; Ming, Wuyi; Cao, Yang

2018-03-01

To intuitively reveal the surface formation mechanism in machining of SiCp/Al composites, in this paper the removal mode of reinforced particle and aluminum matrix, and their influence on surface formation mechanism were analyzed by single diamond grit cutting simulation and single diamond grit scratch experiment. Simulation and experiment results show that when the depth of cut is small, the scratched surface of the workpiece is relatively smooth; however, there are also irregular pits on the machined surface. When increasing the depth of cut, there are many obvious laminar structures on the scratched surface, and the surface appearance becomes coarser. When the cutting speed is small, the squeezing action of abrasive grit on SiC particles plays a dominant role in the extrusion of SiC particles. When increasing the cutting speed, SiC particles also occur broken or fractured; but the machined surface becomes smooth. When machining SiCp/Al composites, the SiC may happen in such removal ways, such as fracture, debonding, broken, sheared, pulled into and pulled out, etc. By means of reasonably developing micro cutting finite element simulation model of SiCp/Al composites could be used to analyze the surface formation process and particle removal way in different machining conditions.

A Numerical Method for Simulating the Microscopic Damage Evolution in Composites Under Uniaxial Transverse Tension

NASA Astrophysics Data System (ADS)

Zhi, Jie; Zhao, Libin; Zhang, Jianyu; Liu, Zhanli

2016-06-01

In this paper, a new numerical method that combines a surface-based cohesive model and extended finite element method (XFEM) without predefining the crack paths is presented to simulate the microscopic damage evolution in composites under uniaxial transverse tension. The proposed method is verified to accurately capture the crack kinking into the matrix after fiber/matrix debonding. A statistical representative volume element (SRVE) under periodic boundary conditions is used to approximate the microstructure of the composites. The interface parameters of the cohesive models are investigated, in which the initial interface stiffness has a great effect on the predictions of the fiber/matrix debonding. The detailed debonding states of SRVE with strong and weak interfaces are compared based on the surface-based and element-based cohesive models. The mechanism of damage in composites under transverse tension is described as the appearance of the interface cracks and their induced matrix micro-cracking, both of which coalesce into transversal macro-cracks. Good agreement is found between the predictions of the model and the in situ experimental observations, demonstrating the efficiency of the presented model for simulating the microscopic damage evolution in composites.

Patient and physician attitudes regarding risk and benefit in streamlined development programmes for antibacterial drugs: a qualitative analysis.

PubMed

Holland, Thomas L; Mikita, Stephen; Bloom, Diane; Roberts, Jamie; McCall, Jonathan; Collyar, Deborah; Santiago, Jonas; Tiernan, Rosemary; Toerner, Joseph

2016-11-10

To explore patient, caregiver and physician perceptions and attitudes regarding the balance of benefit and risk in using antibacterial drugs developed through streamlined development processes. Semistructured focus groups and in-depth interviews were conducted to elicit perceptions and attitudes about the use of antibacterial drugs to treat multidrug-resistant infections. Participants were given background information about antibiotic resistance, streamlined drug development programmes and FDA drug approval processes. Audio recordings of focus groups/interviews were reviewed and quotes excerpted and categorised to identify key themes. Two primary stakeholder groups were engaged: one comprising caregivers, healthy persons and patients who had recovered from or were at risk of resistant infection (N=67; 11 focus groups); and one comprising physicians who treat resistant infections (N=23). Responses from focus groups/interviews indicated widespread awareness among patients/caregivers and physicians of the seriousness of the problem of antibacterial resistance. Both groups were willing to accept a degree of uncertainty regarding the balance of risk and benefit in a new therapy where a serious unmet need exists, but also expressed a desire for rigorous monitoring and rapid, transparent reporting of safety/effectiveness data. Both groups wanted to ensure that >1 physician had input on whether to treat patients with antibiotics developed through a streamlined process. Some patients/caregivers unfamiliar with exigencies of critical care suggested a relatively large multidisciplinary team, while physicians believed individual expert consultations would be preferable. Both groups agreed that careful oversight and stewardship of antibacterial drugs are needed to ensure patient safety, preserve efficacy and prevent abuse. Groups comprising patients/caregivers and physicians were aware of serious issues posed by resistant infections and the lack of effective antibacterial drug

Simulation of Impact Phenomena on the Composite Structures Containing Ceramic Plates and High Entropy Alloys

NASA Astrophysics Data System (ADS)

Geantă, V.; Cherecheș, T.; Lixandru, P.; Voiculescu, I.; Ștefănoiu, R.; Dragnea, D.; Zecheru, T.; Matache, L.

2017-06-01

Due to excellent mechanical properties, high entropy alloys from the system AlxCrFeCoNi can be used successfully to create composite structures containing both metallic and ceramic plates, which resists at dynamic load during high speeds impact (like projectiles, explosion). The paper presents four different composite structures made from a combination of metallic materials and ceramics plates: duralumin-ceramics, duralumin-ceramics-HEA, HEA-ceramics-HEA, HEA-ceramics-duralumin. Numerical simulation of impact behavior of the composite structures was performed by virtual methods, taking into account the mechanical properties of both materials. The best results were obtained using composite structures HEA-ceramics-HEA, HEA-ceramics-duralumin.

The Cassini Solstice Mission: Streamlining Operations by Sequencing with PIEs

NASA Technical Reports Server (NTRS)

Vandermey, Nancy; Alonge, Eleanor K.; Magee, Kari; Heventhal, William

2014-01-01

The Cassini Solstice Mission (CSM) is the second extended mission phase of the highly successful Cassini/Huygens mission to Saturn. Conducted at a much-reduced funding level, operations for the CSM have been streamlined and simplified significantly. Integration of the science timeline, which involves allocating observation time in a balanced manner to each of the five different science disciplines (with representatives from the twelve different science instruments), has long been a labor-intensive endeavor. Lessons learned from the prime mission (2004-2008) and first extended mission (Equinox mission, 2008-2010) were utilized to design a new process involving PIEs (Pre-Integrated Events) to ensure the highest priority observations for each discipline could be accomplished despite reduced work force and overall simplification of processes. Discipline-level PIE lists were managed by the Science Planning team and graphically mapped to aid timeline deconfliction meetings prior to assigning discrete segments of time to the various disciplines. Periapse segments are generally discipline-focused, with the exception of a handful of PIEs. In addition to all PIEs being documented in a spreadsheet, allocated out-of-discipline PIEs were entered into the Cassini Information Management System (CIMS) well in advance of timeline integration. The disciplines were then free to work the rest of the timeline internally, without the need for frequent interaction, debate, and negotiation with representatives from other disciplines. As a result, the number of integration meetings has been cut back extensively, freeing up workforce. The sequence implementation process was streamlined as well, combining two previous processes (and teams) into one. The new Sequence Implementation Process (SIP) schedules 22 weeks to build each 10-week-long sequence, and only 3 sequence processes overlap. This differs significantly from prime mission during which 5-week-long sequences were built in 24 weeks

Influence of Thermal Cycling on Flexural Properties and Simulated Wear of Computer-aided Design/Computer-aided Manufacturing Resin Composites.

PubMed

Tsujimoto, A; Barkmeier, W W; Takamizawa, T; Latta, M A; Miyazaki, M

The purpose of this study was to evaluate the influence of thermal cycling on the flexural properties and simulated wear of computer-aided design/computer-aided manufacturing (CAD/CAM) resin composites. The six CAD/CAM resin composites used in this study were 1) Lava Ultimate CAD/CAM Restorative (LU); 2) Paradigm MZ100 (PM); 3) CERASMART (CS); 4) Shofu Block HC (SB); 5) KATANA AVENCIA Block (KA); and 6) VITA ENAMIC (VE). Specimens were divided randomly into two groups, one of which was stored in distilled water for 24 hours, and the other of which was subjected to 10,000 thermal cycles. For each material, 15 specimens from each group were used to determine the flexural strength and modulus according to ISO 6872, and 20 specimens from each group were used to examine wear using a localized wear simulation model. The test materials were subjected to a wear challenge of 400,000 cycles in a Leinfelder-Suzuki device (Alabama machine). The materials were placed in custom-cylinder stainless steel fixtures, and simulated localized wear was generated using a stainless steel ball bearing (r=2.387 mm) antagonist in a water slurry of polymethyl methacrylate beads. Simulated wear was determined using a noncontact profilometer (Proscan 2100) with Proscan and AnSur 3D software. The two-way analysis of variance of flexural properties and simulated wear of CAD/CAM resin composites revealed that material type and thermal cycling had a significant influence (p<0.05), but there was no significant interaction (p>0.05) between the two factors. The flexural properties and maximum depth of wear facets of CAD/CAM resin composite were different (p<0.05) depending on the material, and their values were influenced (p>0.05) by thermal cycling, except in the case of VE. The volume losses in wear facets on LU, PM, and SB after 10,000 thermal cycles were significantly higher (p<0.05) than those after 24 hours of water storage, unlike CS, KA, and VE. The results of this study indicate that the

Regimes of Flow over Complex Structures of Endothelial Glycocalyx: A Molecular Dynamics Simulation Study.

PubMed

Jiang, Xi Zhuo; Feng, Muye; Ventikos, Yiannis; Luo, Kai H

2018-04-10

Flow patterns on surfaces grafted with complex structures play a pivotal role in many engineering and biomedical applications. In this research, large-scale molecular dynamics (MD) simulations are conducted to study the flow over complex surface structures of an endothelial glycocalyx layer. A detailed structure of glycocalyx has been adopted and the flow/glycocalyx system comprises about 5,800,000 atoms. Four cases involving varying external forces and modified glycocalyx configurations are constructed to reveal intricate fluid behaviour. Flow profiles including temporal evolutions and spatial distributions of velocity are illustrated. Moreover, streamline length and vorticity distributions under the four scenarios are compared and discussed to elucidate the effects of external forces and glycocalyx configurations on flow patterns. Results show that sugar chain configurations affect streamline length distributions but their impact on vorticity distributions is statistically insignificant, whilst the influence of the external forces on both streamline length and vorticity distributions are trivial. Finally, a regime diagram for flow over complex surface structures is proposed to categorise flow patterns.

An Enriched Shell Finite Element for Progressive Damage Simulation in Composite Laminates

NASA Technical Reports Server (NTRS)

McElroy, Mark W.

2016-01-01

A formulation is presented for an enriched shell nite element capable of progressive damage simulation in composite laminates. The element uses a discrete adaptive splitting approach for damage representation that allows for a straightforward model creation procedure based on an initially low delity mesh. The enriched element is veri ed for Mode I, Mode II, and mixed Mode I/II delamination simulation using numerical benchmark data. Experimental validation is performed using test data from a delamination-migration experiment. Good correlation was found between the enriched shell element model results and the numerical and experimental data sets. The work presented in this paper is meant to serve as a rst milestone in the enriched element's development with an ultimate goal of simulating three-dimensional progressive damage processes in multidirectional laminates.

Managing heat phenomena in epoxy composites production via graphenic derivatives: synthesis, properties and industrial production simulation of graphene and graphene oxide containing composites

NASA Astrophysics Data System (ADS)

Mazzocchetti, Laura; Benelli, Tiziana; D'Angelo, Emanuele; Ligi, Simone; Minak, Giangiacomo; Poodts, Ezequiel; Tarterini, Fabrizio; Palermo, Vincenzo; Giorgini, Loris

2017-03-01

A commercial two-components epoxy resin formulation was successfully modified by adding graphene and related materials (GRMs) and the effect of these nanofillers was assessed on their thermomechanical properties as well as on the simulation of their industrial application for the production of thick composites objects with interesting results. GMRs were added in different concentrations in order to improve thermo-mechanical properties of the nano-composite thermoset. Different dispersion methods were taken into account in order to produce stable long-lasting dispersion of the GRMs, that can withstand a commercial shelf life. Addition of the GRMs improves the glass transition temperature of the nanocomposite up to 20 °C with respect to the plain commercial formulation, and both stress and elongation at break increase up to almost 4 times the original values. Moreover, the industrial curing of some of the more promising modified resins was computer-simulated when the two-components resins are used to produce a carbon-fibre reinforced thick composite beam. Simulation results show that some of the applied GRMs helps reducing or even completely preventing the overheat phenomena that are well renown to induce significant thermal stresses negatively affecting the final object performances. These interesting effects would contribute reducing the time required for a single industrial production cycle, since no time for overheat dispersion is required, thus helping increasing the production rate.

Quadratic genetic modifications: a streamlined route to cosmological simulations with controlled merger history

NASA Astrophysics Data System (ADS)

Rey, Martin P.; Pontzen, Andrew

2018-02-01

Recent work has studied the interplay between a galaxy's history and its observable properties using `genetically modified' cosmological zoom simulations. The approach systematically generates alternative histories for a halo, while keeping its cosmological environment fixed. Applications to date altered linear properties of the initial conditions, such as the mean overdensity of specified regions; we extend the formulation to include quadratic features, such as local variance, that determines the overall importance of smooth accretion relative to mergers in a galaxy's history. We introduce an efficient algorithm for this new class of modification and demonstrate its ability to control the variance of a region in a one-dimensional toy model. Outcomes of this work are twofold: (i) a clarification of the formulation of genetic modifications and (ii) a proof of concept for quadratic modifications leading the way to a forthcoming implementation in cosmological simulations.

Implementing an Enterprise Information System to Reengineer and Streamline Administrative Processes in a Distance Learning Unit

ERIC Educational Resources Information Center

Abdous, M'hammed; He, Wu

2009-01-01

During the past three years, we have developed and implemented an enterprise information system (EIS) to reengineer and facilitate the administrative process for preparing and teaching distance learning courses in a midsized-to-large university (with 23,000 students). The outcome of the implementation has been a streamlined and efficient process…

Composite materials molding simulation for purpose of automotive industry

NASA Astrophysics Data System (ADS)

Grabowski, Ł.; Baier, A.; Majzner, M.; Sobek, M.

2016-08-01

Composite materials loom large increasingly important role in the overall industry. Composite material have a special role in the ever-evolving automotive industry. Every year the composite materials are used in a growing number of elements included in the cars construction. Development requires the search for ever new applications of composite materials in areas where previously were used only metal materials. Requirements for modern solutions, such as reducing the weight of vehicles, the required strength and vibration damping characteristics go hand in hand with the properties of modern composite materials. The designers faced the challenge of the use of modern composite materials in the construction of bodies of power steering systems in vehicles. The initial choice of method for producing composite bodies was the method of molding injection of composite material. Molding injection of polymeric materials is a widely known and used for many years, but the molding injection of composite materials is a relatively new issue, innovative, it is not very common and is characterized by different conditions, parameters and properties in relation to the classical method. Therefore, for the purpose of selecting the appropriate composite material for injection for the body of power steering system computer analysis using Siemens NX 10.0 environment, including Moldex 3d and EasyFill Advanced tool to simulate the injection of materials from the group of possible solutions were carried out. Analyses were carried out on a model of a modernized wheel case of power steering system. During analysis, input parameters, such as temperature, pressure injectors, temperature charts have been analysed. An important part of the analysis was to analyse the propagation of material inside the mold during injection, so that allowed to determine the shape formability and the existence of possible imperfections of shapes and locations air traps. A very important parameter received from

Composite Cure Process Modeling and Simulations using COMPRO(Registered Trademark) and Validation of Residual Strains using Fiber Optics Sensors

NASA Technical Reports Server (NTRS)

Sreekantamurthy, Thammaiah; Hudson, Tyler B.; Hou, Tan-Hung; Grimsley, Brian W.

2016-01-01

Composite cure process induced residual strains and warping deformations in composite components present significant challenges in the manufacturing of advanced composite structure. As a part of the Manufacturing Process and Simulation initiative of the NASA Advanced Composite Project (ACP), research is being conducted on the composite cure process by developing an understanding of the fundamental mechanisms by which the process induced factors influence the residual responses. In this regard, analytical studies have been conducted on the cure process modeling of composite structural parts with varied physical, thermal, and resin flow process characteristics. The cure process simulation results were analyzed to interpret the cure response predictions based on the underlying physics incorporated into the modeling tool. In the cure-kinetic analysis, the model predictions on the degree of cure, resin viscosity and modulus were interpreted with reference to the temperature distribution in the composite panel part and tool setup during autoclave or hot-press curing cycles. In the fiber-bed compaction simulation, the pore pressure and resin flow velocity in the porous media models, and the compaction strain responses under applied pressure were studied to interpret the fiber volume fraction distribution predictions. In the structural simulation, the effect of temperature on the resin and ply modulus, and thermal coefficient changes during curing on predicted mechanical strains and chemical cure shrinkage strains were studied to understand the residual strains and stress response predictions. In addition to computational analysis, experimental studies were conducted to measure strains during the curing of laminated panels by means of optical fiber Bragg grating sensors (FBGs) embedded in the resin impregnated panels. The residual strain measurements from laboratory tests were then compared with the analytical model predictions. The paper describes the cure process

Simulation of ultrasonic NCF composites testing using 3D finite element model

NASA Astrophysics Data System (ADS)

Liu, Z.; Saffari, N.; Fromme, P.

2012-04-01

Composite materials offer many advantages for aerospace applications, e.g., good strength to weight ratio. Different types of composites, such as non-crimp fabrics (NCF), are currently being investigated as they offer reduced manufacturing costs and improved damage tolerance as compared to traditional pre-impregnated composite materials. NCF composites are made from stitched fiber bundles (tows), which typically have a width and thickness in the order of millimeter. This results in strongly inhomogeneous and anisotropic material properties. Different types of manufacturing imperfections, such as porosity, resin pockets, tow crimp and misalignment can lead to reduced material strength and thus to defects following excessive loads or impact, e.g. fracture and delaminations. The ultrasonic non-destructive testing of NCF composites is difficult, as the tow size is comparable to the wavelength, leading to multiple scattering in this inherently three-dimensional structure. For typical material properties and geometry of an NCF composite, a full three-dimensional Finite Element (FE) model has been developed in ABAQUS. The propagation of longitudinal ultrasonic waves has been simulated and the effect of multiple scattering at the fiber tows investigated. The effect of porosity as a typical manufacturing imperfection has been considered. The potential for the detection and quantification of such defects is discussed based on the observed influence on the ultrasonic wave propagation and attenuation.

Finite Element Simulation of Low Velocity Impact Damage on an Aeronautical Carbon Composite Structure

NASA Astrophysics Data System (ADS)

Lemanle Sanga, Roger Pierre; Garnier, Christian; Pantalé, Olivier

2016-12-01

Low velocity barely visible impact damage (BVID) in laminated carbon composite structures has a major importance for aeronautical industries. This contribution leads with the development of finite element models to simulate the initiation and the propagation of internal damage inside a carbon composite structure due by a low velocity impact. Composite plates made from liquid resin infusion process (LRI) have been subjected to low energy impacts (around 25 J) using a drop weight machine. In the experimental procedure, the internal damage is evaluated using an infrared thermographic camera while the indentation depth of the face is measured by optical measurement technique. In a first time we developed a robust model using homogenised shells based on degenerated tri-dimensional brick elements and in a second time we decided to modelize the whole stacking sequence of homogeneous layers and cohesive interlaminar interfaces in order to compare and validate the obtained results. Both layer and interface damage initiation and propagation models based on the Hashin and the Benzeggagh-Kenane criteria have been used for the numerical simulations. Comparison of numerical results and experiments has shown the accuracy of the proposed models.

Simulation of Complex Cracking in Plain Weave C/SiC Composite under Biaxial Loading

NASA Technical Reports Server (NTRS)

Cheng, Ron-Bin; Hsu, Su-Yuen

2012-01-01

Finite element analysis is performed on a mesh, based on computed geometry of a plain weave C/SiC composite with assumed internal stacking, to reveal the pattern of internal damage due to biaxial normal cyclic loading. The simulation encompasses intertow matrix cracking, matrix cracking inside the tows, and separation at the tow-intertow matrix and tow-tow interfaces. All these dissipative behaviors are represented by traction-separation cohesive laws. Not aimed at quantitatively predicting the overall stress-strain relation, the simulation, however, does not take the actual process of fiber debonding into account. The fiber tows are represented by a simple rule-of-mixture model where the reinforcing phase is a hypothetical one-dimensional material. Numerical results indicate that for the plain weave C/SiC composite, 1) matrix-crack initiation sites are primarily determined by large intertow matrix voids and interlayer tow-tow contacts, 2) the pattern of internal damage strongly depends on the loading path and initial stress, 3) compressive loading inflicts virtually no damage evolution. KEY WORDS: ceramic matrix composite, plain weave, cohesive model, brittle failure, smeared crack model, progressive damage, meso-mechanical analysis, finite element.

Repair Strength in Simulated Restorations of Methacrylate- or Silorane-Based Composite Resins.

PubMed

Consani, Rafael Leonardo Xediek; Marinho, Tatiane; Bacchi, Atais; Caldas, Ricardo Armini; Feitosa, Victor Pinheiro; Pfeifer, Carmem Silvia

2016-01-01

The study verified the bond strength in simulated dental restorations of silorane- or methacrylate-based composites repaired with methacrylate-based composite. Methacrylate- (P60) or silorane-based (P90) composites were used associated with adhesive (Adper Single Bond 2). Twenty-four hemi-hourglass-shaped samples were repaired with each composite (n=12). Samples were divided according to groups: G1= P60 + Adper Single Bond 2+ P60; G2= P60 + Adper Single Bond 2 + P60 + thermocycling; G3= P90 + Adper Single Bond 2 + P60; and G4= P90 + Adper Single Bond 2 + P60 + thermocycling. G1 and G3 were submitted to tensile test 24 h after repair procedure, and G2 and G4 after submitted to 5,000 thermocycles at 5 and 55 ?#61616;C for 30 s in each bath. Tensile bond strength test was accomplished in an universal testing machine at crosshead speed of 0.5 mm/min. Data (MPa) were analyzed by two-way ANOVA and Tukey's test (5%). Sample failure pattern (adhesive, cohesive in resin or mixed) was evaluated by stereomicroscope at 30?#61655; and images were obtained in SEM. Bond strength values of methacrylate-based composite samples repaired with methacrylate-based composite (G1 and G2) were greater than for silorane-based samples (G3 and G4). Thermocycling decreased the bond strength values for both composites. All groups showed predominance of adhesive failures and no cohesive failure in composite resin was observed. In conclusion, higher bond strength values were observed in methacrylate-based resin samples and greater percentage of adhesive failures in silorane-based resin samples, both composites repaired with methacrylate-based resin.

A Prediction of the Damping Properties of Hindered Phenol AO-60/polyacrylate Rubber (AO-60/ACM) Composites through Molecular Dynamics Simulation

NASA Astrophysics Data System (ADS)

Yang, Da-Wei; Zhao, Xiu-Ying; Zhang, Geng; Li, Qiang-Guo; Wu, Si-Zhu

2016-05-01

Molecule dynamics (MD) simulation, a molecular-level method, was applied to predict the damping properties of AO-60/polyacrylate rubber (AO-60/ACM) composites before experimental measures were performed. MD simulation results revealed that two types of hydrogen bond, namely, type A (AO-60) -OH•••O=C- (ACM), type B (AO-60) - OH•••O=C- (AO-60) were formed. Then, the AO-60/ACM composites were fabricated and tested to verify the accuracy of the MD simulation through dynamic mechanical thermal analysis (DMTA). DMTA results showed that the introduction of AO-60 could remarkably improve the damping properties of the composites, including the increase of glass transition temperature (Tg) alongside with the loss factor (tan δ), also indicating the AO-60/ACM(98/100) had the best damping performance amongst the composites which verified by the experimental.

Streamlined Islands in Ares Valles

NASA Technical Reports Server (NTRS)

2002-01-01

(Released 10 June 2002) The Science Although liquid water is not stable on the surface of Mars today, there is substantial geologic evidence that large quantities of water once flowed across the surface in the distant past. Streamlined islands, shown here, are one piece of evidence for this ancient water. The tremendous force of moving water, possibly from a catastrophic flood, carved these teardrop-shaped islands within a much larger channel called Ares Valles. The orientation of the islands can be used as an indicator of the direction the water flowed. The islands have a blunt end that is usually associated with an obstacle, commonly an impact crater. The crater is resistant to erosion and creates a geologic barrier around which the water must flow. As the water flows past the obstacle, its erosive power is directed outward, leaving the area in the lee of the obstacle relatively uneroded. However, some scientists have also argued that the area in the lee of the obstacle might be a depositional zone, where material is dropped out of the water as it briefly slows. The ridges observed on the high-standing terrain in the leeward parts of the islands may be benches carved into the rock that mark the height of the water at various times during the flood, or they might be indicative of layering in the leeward rock. As the water makes its way downstream, the interference of the water flow by the obstacle is reduced, and the water that was diverted around the obstacle rejoins itself at the narrow end of the island. Therefore, the direction of the water flow is parallel to the orientation of the island, and the narrow end of the island points downstream. In addition to the streamlined islands, the channel floor exhibits fluting that is also suggestive of flowing water. The flutes (also known as longitudinal grooves) are also parallel to the direction of flow, indicating that the water flow was turbulent and probably quite fast, which is consistent with the hypothesized

Modeling approaches for the simulation of ultrasonic inspections of anisotropic composite structures in the CIVA software platform

NASA Astrophysics Data System (ADS)

Jezzine, Karim; Imperiale, Alexandre; Demaldent, Edouard; Le Bourdais, Florian; Calmon, Pierre; Dominguez, Nicolas

2018-04-01

Models for the simulation of ultrasonic inspections of flat and curved plate-like composite structures, as well as stiffeners, are available in the CIVA-COMPOSITE module released in 2016. A first modelling approach using a ray-based model is able to predict the ultrasonic propagation in an anisotropic effective medium obtained after having homogenized the composite laminate. Fast 3D computations can be performed on configurations featuring delaminations, flat bottom holes or inclusions for example. In addition, computations on ply waviness using this model will be available in CIVA 2017. Another approach is proposed in the CIVA-COMPOSITE module. It is based on the coupling of CIVA ray-based model and a finite difference scheme in time domain (FDTD) developed by AIRBUS. The ray model handles the ultrasonic propagation between the transducer and the FDTD computation zone that surrounds the composite part. In this way, the computational efficiency is preserved and the ultrasound scattering by the composite structure can be predicted. Alternatively, a high order finite element approach is currently developed at CEA but not yet integrated in CIVA. The advantages of this approach will be discussed and first simulation results on Carbon Fiber Reinforced Polymers (CFRP) will be shown. Finally, the application of these modelling tools to the construction of metamodels is discussed.

Ion plasma deposition of oxide films with graded-stoichiometry composition: Experiment and simulation

NASA Astrophysics Data System (ADS)

Volpyas, V. A.; Tumarkin, A. V.; Mikhailov, A. K.; Kozyrev, A. B.; Platonov, R. A.

2016-07-01

A method of ion plasma deposition is proposed for obtaining thin multicomponent films with continuously graded composition in depth of the film. The desired composition-depth profile is obtained by varying the working gas pressure during deposition in the presence of an additional adsorbing screen in the drift space between a sputtered target and substrate. Efficiency of the proposed method is confirmed by Monte Carlo simulation of the deposition of thin films of Ba x Sr1- x TiO3 (BSTO) solid solution. It is demonstrated that, during sputtering of a Ba0.3Sr0.7TiO3 target, the parameter of composition stoichiometry in the growing BSTO film varies in the interval of x = 0.3-0.65 when the gas pressure is changed within 2-60 Pa.

Spectral singularity in composite systems and simulation of a resonant lasing cavity

NASA Astrophysics Data System (ADS)

Zhang, X. Z.; Li, G. R.; Song, Z.

2017-10-01

We investigate herein the existence of spectral singularities (SSs) in composite systems that consist of two separate scattering centers A and B embedded in one-dimensional free space, with at least one scattering center being non-Hermitian. We show that such composite systems have an SS at kc if the reflection amplitudes rA≤ft(kc\\right) and rB≤ft(kc\\right) of the two scattering centers satisfy the condition rR A≤ft(kc\\right) rLB≤ft(kc\\right) ei2kc≤ft(xB-xA\\right) =1 . We also extend the condition to the system with multi-scattering centers. As an application, we construct a simple system to simulate a resonant lasing cavity.

Intelligence and Electronic Warfare (IEW) Streamlining Project. Volume 1. Sustainment Analysis Report. Revision

DTIC Science & Technology

1992-10-30

I Sustainment Analysis Report Accesion For NTIS CRA&I DTIC 1 AP- U. an-;o u,ced [] jj ~~~Y INSPECTED 5 Js~~~o By.......... ............ Dit Ib ’tiot...ELECTRONIC WARFARE (1EW) STREAMUNING PROJECT Vohune I Sustainment Analysis Report Revised October 30, 1992 93-29047 The views, opinions, and findings...Streamlining Project, C OPM-91-2964 Volume I, Sustainment Analysis Report PR 02TO2K 6. AUTHORIS) David P. Nicholas, Robert E. Klebo. Wolodymyr J. Mokey

Visualizing Time-Varying Phenomena In Numerical Simulations Of Unsteady Flows

NASA Technical Reports Server (NTRS)

Lane, David A.

1996-01-01

Streamlines, contour lines, vector plots, and volume slices (cutting planes) are commonly used for flow visualization. These techniques are sometimes referred to as instantaneous flow visualization techniques because calculations are based on an instant of the flowfield in time. Although instantaneous flow visualization techniques are effective for depicting phenomena in steady flows,they sometimes do not adequately depict time-varying phenomena in unsteady flows. Streaklines and timelines are effective visualization techniques for depicting vortex shedding, vortex breakdown, and shock waves in unsteady flows. These techniques are examples of time-dependent flow visualization techniques, which are based on many instants of the flowfields in time. This paper describes the algorithms for computing streaklines and timelines. Using numerically simulated unsteady flows, streaklines and timelines are compared with streamlines, contour lines, and vector plots. It is shown that streaklines and timelines reveal vortex shedding and vortex breakdown more clearly than instantaneous flow visualization techniques.

Simulation of an Impact Test of the All-Composite Lear Fan Aircraft

NASA Technical Reports Server (NTRS)

Stockwell, Alan E.; Jones, Lisa E. (Technical Monitor)

2002-01-01

An MSC.Dytran model of an all-composite Lear Fan aircraft fuselage was developed to simulate an impact test conducted at the NASA Langley Research Center Impact Dynamics Research Facility (IDRF). The test was the second of two Lear Fan impact tests. The purpose of the second test was to evaluate the performance of retrofitted composite energy-absorbing floor beams. A computerized photogrammetric survey was performed to provide airframe geometric coordinates, and over 5000 points were processed and imported into MSC.Patran via an IGES file. MSC.Patran was then used to develop the curves and surfaces and to mesh the finite element model. A model of the energy-absorbing floor beams was developed separately and then integrated into the Lear Fan model. Structural responses of components such as the wings were compared with experimental data or previously published analytical data wherever possible. Comparisons with experimental results were used to guide structural model modifications to improve the simulation performance. This process was based largely on qualitative (video and still camera images and post-test inspections) rather than quantitative results due to the relatively few accelerometers attached to the structure.

Orthorhombic Titanium Matrix Composite Subjected to Simulated Engine Mission Cycles

NASA Technical Reports Server (NTRS)

Gabb, Timothy P.

1997-01-01

Titanium matrix composites (TMC's) are commonly made up of a titanium alloy matrix reinforced by silicon carbide fibers that are oriented parallel to the loading axis. These composites can provide high strength at lower densities than monolithic titanium alloys and superalloys in selected gas turbine engine applications. The use of TMC rings with unidirectional SiC fibers as reinforcing rings within compressor rotors could significantly reduce the weight of these components. In service, these TMC reinforcing rings would be subjected to complex service mission loading cycles, including fatigue and dwell excursions. Orthorhombic titanium aluminide alloys are of particular interest for such TMC applications because their tensile and creep strengths are high in comparison to those of other titanium alloys. The objective of this investigation was to assess, in simulated mission tests at the NASA Lewis Research Center, the durability of a SiC (SCS-6)/Ti-22Al-23Nb (at.%) TMC for compressor ring applications, in cooperation with the Allison Engine Company.

Brownfields Assessing Contractor Capabilities for Streamlined Site Investigation: Additional Information Regarding All Appropriate Inquiries and Hiring an Environmental Professional

EPA Pesticide Factsheets

This document assists Brownfields grantees and other decision makers as they assess the capabilities of contractors and consultants to determine their qualifications to provide streamlined and innovative strategies for the assessment and and cleanup.

Ecosystem composition changes over the past millennium: model simulations and comparison with paleoecological observations

NASA Astrophysics Data System (ADS)

Liu, Y.; Rollinson, C.; Dietze, M.; McLachlan, J. S.; Poulter, B.; Quaife, T. L.; Raiho, A.; Ricciuto, D. M.; Schaefer, K. M.; Steinkamp, J.; Moore, D. J.

2015-12-01

Over multi-decadal to multi-centennial timescales, ecosystem function and carbon storage is largely influenced by vegetation composition. The predictability of ecosystem responses to climate change thus depends on the understanding of long-term community dynamics. Our study aims to quantify the influence of the most relevant ecological factors that control plant distribution and abundance, in contemporary terrestrial biosphere models and in paleo-records, and constrain the model processes and parameters with paleoecological data. We simulated vegetation changes at 6 sites in the northeastern United States over the past 1160 years using 7 terrestrial biosphere models and variations (CLM4.5-CN, ED2, ED2-LU, JULES-TRIFFID, LINKAGES, LPJ-GUESS, LPJ-wsl) driven by common paleoclimatic drivers. We examined plant growth, recruitment, and mortality (including other carbon turnover) of the plant functional types (PFTs) in the models, attributed the responses to three major factors (climate, competition, and disturbance), and estimated the relative effect of each factor. We assessed the model responses against plant-community theories (bioclimatic limits, niche difference, temporal variation and storage effect, and disturbance). We found that vegetation composition were sensitive to realized niche differences (e.g. differential growth response) among PFTs. Because many models assume unlimited dispersal and sometimes recruitment, the "storage effect" constantly affects community composition. Fire was important in determining the ecosystem composition, yet the vegetation to fire feedback was weak in the models. We also found that vegetation-composition changes in the simulations were driven to a much greater degree by growth as opposed to by turnover/mortality, when compared with those in paleoecological records. Our work suggest that 1) for forecasting slow changes in vegetation composition, we can use paleo-data to better quantify the realized niches of PFTs and associated

Concurrent Probabilistic Simulation of High Temperature Composite Structural Response

NASA Technical Reports Server (NTRS)

Abdi, Frank

1996-01-01

A computational structural/material analysis and design tool which would meet industry's future demand for expedience and reduced cost is presented. This unique software 'GENOA' is dedicated to parallel and high speed analysis to perform probabilistic evaluation of high temperature composite response of aerospace systems. The development is based on detailed integration and modification of diverse fields of specialized analysis techniques and mathematical models to combine their latest innovative capabilities into a commercially viable software package. The technique is specifically designed to exploit the availability of processors to perform computationally intense probabilistic analysis assessing uncertainties in structural reliability analysis and composite micromechanics. The primary objectives which were achieved in performing the development were: (1) Utilization of the power of parallel processing and static/dynamic load balancing optimization to make the complex simulation of structure, material and processing of high temperature composite affordable; (2) Computational integration and synchronization of probabilistic mathematics, structural/material mechanics and parallel computing; (3) Implementation of an innovative multi-level domain decomposition technique to identify the inherent parallelism, and increasing convergence rates through high- and low-level processor assignment; (4) Creating the framework for Portable Paralleled architecture for the machine independent Multi Instruction Multi Data, (MIMD), Single Instruction Multi Data (SIMD), hybrid and distributed workstation type of computers; and (5) Market evaluation. The results of Phase-2 effort provides a good basis for continuation and warrants Phase-3 government, and industry partnership.

Verification of the isotopic composition of precipitation simulated by a regional isotope circulation model over Japan.

PubMed

Tanoue, Masahiro; Ichiyanagi, Kimpei; Yoshimura, Kei

2016-01-01

The isotopic composition (δ(18)O and δ(2)H) of precipitation simulated by a regional isotope circulation model with a horizontal resolution of 10, 30 and 50 km was compared with observations at 56 sites over Japan in 2013. All simulations produced reasonable spatio-temporal variations in δ(18)O in precipitation over Japan, except in January. In January, simulated δ(18)O values in precipitation were higher than observed values on the Pacific side of Japan, especially during an explosively developing extratropical cyclone event. This caused a parameterisation of precipitation formulation about the large fraction of precipitated water to liquid detrained water in the lower troposphere. As a result, most water vapour that transported from the Sea of Japan precipitated on the Sea of Japan side. The isotopic composition of precipitation was a useful verification tool for the parameterisation of precipitation formulation as well as large-scale moisture transport processes in the regional isotope circulation model.

Simulation for Carbon Nanotube Dispersion and Microstructure Formation in CNTs/AZ91D Composite Fabricated by Ultrasonic Processing

NASA Astrophysics Data System (ADS)

Yang, Yuansheng; Zhao, Fuze; Feng, Xiaohui

2017-10-01

The dispersion of carbon nanotubes (CNTs) in AZ91D melt by ultrasonic processing and microstructure formation of CNTs/AZ91D composite were studied using numerical and physical simulations. The sound field and acoustic streaming were predicted using finite element method. Meanwhile, optimal immersion depth of the ultrasonic probe and suitable ultrasonic power were obtained. Single-bubble model was used to predict ultrasonic cavitation in AZ91D melt. The relationship between sound pressure amplitude and ultrasonic cavitation was established. Physical simulations of acoustic streaming and ultrasonic cavitation agreed well with the numerical simulations. It was confirmed that the dispersion of carbon nanotubes was remarkably improved by ultrasonic processing. Microstructure formation of CNTs/AZ91D composite was numerically simulated using cellular automation method. In addition, grain refinement was achieved and the growth of dendrites was changed due to the uniform dispersion of CNTs.

Numerical design of streamlined tunnel walls for a two-dimensional transonic test

NASA Technical Reports Server (NTRS)

Newman, P. A.; Anderson, E. C.

1978-01-01

An analytical procedure is discussed for designing wall shapes for streamlined, nonporous, two-dimensional, transonic wind tunnels. It is based upon currently available 2-D inviscid transonic and boundary layer analysis computer programs. Predicted wall shapes are compared with experimental data obtained from the NASA Langley 6 by 19 inch Transonic Tunnel where the slotted walls were replaced by flexible nonporous walls. Comparisons are presented for the empty tunnel operating at a Mach number of 0.9 and for a supercritical test of an NACA 0012 airfoil at zero lift. Satisfactory agreement is obtained between the analytically and experimentally determined wall shapes.

Analysis Model and Numerical Simulation of Thermoelectric Response of CFRP Composites

NASA Astrophysics Data System (ADS)

Lin, Yueguo

2018-05-01

An electric current generates Joule heating, and under steady state conditions, a sample exhibits a balance between the strength dissipated by the Joule effect and the heat exchange with the environment by radiation and convection. In the present paper, theoretical model, numerical FEM and experimental methods have been used to analyze the radiation and free convection properties in CFRP composite samples heated by an electric current. The materials employed in these samples have applications in many aeronautic devices. This study addresses two types of composite materials, UD [0]8 and QI [45/90/-45/0]S, which were prepared for thermoelectric experiments. A DC electric current (ranging from 1A to 8A) was injected through the specimen ends to find the coupling effect between the electric current and temperature. An FE model and simplified thermoelectric analysis model are presented in detail to represent the thermoelectric data. These are compared with the experimental results. All of the test equipments used to obtain the experimental data and the numerical simulations are characterized, and we find that the numerical simulations correspond well with the experiments. The temperature of the surface of the specimen is almost proportional to the electric current. The simplified analysis model was used to calculate the balance time of the temperature, which is consistent throughout all of the experimental investigations.

Probabilistic composite micromechanics

NASA Technical Reports Server (NTRS)

Stock, T. A.; Bellini, P. X.; Murthy, P. L. N.; Chamis, C. C.

1988-01-01

Probabilistic composite micromechanics methods are developed that simulate expected uncertainties in unidirectional fiber composite properties. These methods are in the form of computational procedures using Monte Carlo simulation. A graphite/epoxy unidirectional composite (ply) is studied to demonstrate fiber composite material properties at the micro level. Regression results are presented to show the relative correlation between predicted and response variables in the study.

Transcriptional Control in Marine Copiotrophic and Oligotrophic Bacteria with Streamlined Genomes.

PubMed

Cottrell, Matthew T; Kirchman, David L

2016-10-01

Bacteria often respond to environmental stimuli using transcriptional control, but this may not be the case for marine bacteria such as "Candidatus Pelagibacter ubique," a cultivated representative of the SAR11 clade, the most abundant organism in the ocean. This bacterium has a small, streamlined genome and an unusually low number of transcriptional regulators, suggesting that transcriptional control is low in Pelagibacter and limits its response to environmental conditions. Transcriptome sequencing during batch culture growth revealed that only 0.1% of protein-encoding genes appear to be under transcriptional control in Pelagibacter and in another oligotroph (SAR92) whereas >10% of genes were under transcriptional control in the copiotrophs Polaribacter sp. strain MED152 and Ruegeria pomeroyi When growth levels changed, transcript levels remained steady in Pelagibacter and SAR92 but shifted in MED152 and R. pomeroyi Transcript abundances per cell, determined using an internal RNA sequencing standard, were low (<1 transcript per cell) for all but a few of the most highly transcribed genes in all four taxa, and there was no correlation between transcript abundances per cell and shifts in the levels of transcription. These results suggest that low transcriptional control contributes to the success of Pelagibacter and possibly other oligotrophic microbes that dominate microbial communities in the oceans. Diverse heterotrophic bacteria drive biogeochemical cycling in the ocean. The most abundant types of marine bacteria are oligotrophs with small, streamlined genomes. The metabolic controls that regulate the response of oligotrophic bacteria to environmental conditions remain unclear. Our results reveal that transcriptional control is lower in marine oligotrophic bacteria than in marine copiotrophic bacteria. Although responses of bacteria to environmental conditions are commonly regulated at the level of transcription, metabolism in the most abundant bacteria in the

78 FR 49680 - Streamlining Requirements Governing the Use of Funding for Supportive Housing for the Elderly and...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-08-15

...-AI67 Streamlining Requirements Governing the Use of Funding for Supportive Housing for the Elderly and... mixed finance developments in the Section 202 Supportive Housing for the Elderly (Section 202) and the.... Accordingly, HUD amends 24 CFR part 891 as follows: PART 891--SUPPORTIVE HOUSING FOR THE ELDERLY AND PERSONS...

Streamlining Payload Integration

NASA Technical Reports Server (NTRS)

Lufkin, Susan N.

2010-01-01

Payload integration onto space transport vehicles and the International Space Station (ISS) is a complex process. Yet, cargo transport is the sole reason for any space mission, be it for ferrying humans, science, or hardware. As the largest such effort in history, the ISS offers a wide variety of payload experience. However, for any payload to reach the Space Station under the current process, Payload Developers face a list of daunting tasks that go well beyond just designing the payload to the constraints of the transport vehicle and its stowage topology. Payload customers are required to prove their payload s functionality, structural integrity, and safe integration - including under less than nominal situations. They must also plan for or provide training, procedures, hardware labeling, ground support, and communications. In addition, they must deal with negotiating shared consumables, integrating software, obtaining video, and coordinating the return of data and hardware. All the while, they must meet export laws, launch schedules, budget limits, and the consensus of more than 12 panel and board reviews. Despite the cost and infrastructure overhead, payload proposals have increased. Just in the span from FY08 to FY09, the NASA Payload Space Station Support Office budget rose from $78M to $96M in attempt to manage the growing manifest, but the potential number of payloads still exceeds available Payload Integration Management manpower. The growth has also increased management difficulties due to the fact that payloads are more frequently added to a flight schedule late in the flow. The current standard ISS template for payload integration from concept to payload turn-over is 36 months, or 18 months if the payload already has a preliminary design. Customers are increasingly requiring a turn-around of 3 to 6-months to meet market needs. The following paper suggests options for streamlining the current payload integration process in order to meet customer schedule

Orchestrating TRANSP Simulations for Interpretative and Predictive Tokamak Modeling with OMFIT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grierson, B. A.; Yuan, X.; Gorelenkova, M.

TRANSP simulations are being used in the OMFIT work- flow manager to enable a machine independent means of experimental analysis, postdictive validation, and predictive time dependent simulations on the DIII-D, NSTX, JET and C-MOD tokamaks. The procedures for preparing the input data from plasma profile diagnostics and equilibrium reconstruction, as well as processing of the time-dependent heating and current drive sources and assumptions about the neutral recycling, vary across machines, but are streamlined by using a common workflow manager. Settings for TRANSP simulation fidelity are incorporated into the OMFIT framework, contrasting between-shot analysis, power balance, and fast-particle simulations. A previouslymore » established series of data consistency metrics are computed such as comparison of experimental vs. calculated neutron rate, equilibrium stored energy vs. total stored energy from profile and fast-ion pressure, and experimental vs. computed surface loop voltage. Discrepancies between data consistency metrics can indicate errors in input quantities such as electron density profile or Zeff, or indicate anomalous fast-particle transport. Measures to assess the sensitivity of the verification metrics to input quantities are provided by OMFIT, including scans of the input profiles and standardized post-processing visualizations. For predictive simulations, TRANSP uses GLF23 or TGLF to predict core plasma profiles, with user defined boundary conditions in the outer region of the plasma. ITPA validation metrics are provided in post-processing to assess the transport model validity. By using OMFIT to orchestrate the steps for experimental data preparation, selection of operating mode, submission, post-processing and visualization, we have streamlined and standardized the usage of TRANSP.« less

Orchestrating TRANSP Simulations for Interpretative and Predictive Tokamak Modeling with OMFIT

DOE PAGES

Grierson, B. A.; Yuan, X.; Gorelenkova, M.; ...

2018-02-21

TRANSP simulations are being used in the OMFIT work- flow manager to enable a machine independent means of experimental analysis, postdictive validation, and predictive time dependent simulations on the DIII-D, NSTX, JET and C-MOD tokamaks. The procedures for preparing the input data from plasma profile diagnostics and equilibrium reconstruction, as well as processing of the time-dependent heating and current drive sources and assumptions about the neutral recycling, vary across machines, but are streamlined by using a common workflow manager. Settings for TRANSP simulation fidelity are incorporated into the OMFIT framework, contrasting between-shot analysis, power balance, and fast-particle simulations. A previouslymore » established series of data consistency metrics are computed such as comparison of experimental vs. calculated neutron rate, equilibrium stored energy vs. total stored energy from profile and fast-ion pressure, and experimental vs. computed surface loop voltage. Discrepancies between data consistency metrics can indicate errors in input quantities such as electron density profile or Zeff, or indicate anomalous fast-particle transport. Measures to assess the sensitivity of the verification metrics to input quantities are provided by OMFIT, including scans of the input profiles and standardized post-processing visualizations. For predictive simulations, TRANSP uses GLF23 or TGLF to predict core plasma profiles, with user defined boundary conditions in the outer region of the plasma. ITPA validation metrics are provided in post-processing to assess the transport model validity. By using OMFIT to orchestrate the steps for experimental data preparation, selection of operating mode, submission, post-processing and visualization, we have streamlined and standardized the usage of TRANSP.« less

Simulation of Fatigue Behavior of High Temperature Metal Matrix Composites

NASA Technical Reports Server (NTRS)

Tong, Mike T.; Singhal, Suren N.; Chamis, Christos C.; Murthy, Pappu L. N.

1996-01-01

A generalized relatively new approach is described for the computational simulation of fatigue behavior of high temperature metal matrix composites (HT-MMCs). This theory is embedded in a specialty-purpose computer code. The effectiveness of the computer code to predict the fatigue behavior of HT-MMCs is demonstrated by applying it to a silicon-fiber/titanium-matrix HT-MMC. Comparative results are shown for mechanical fatigue, thermal fatigue, thermomechanical (in-phase and out-of-phase) fatigue, as well as the effects of oxidizing environments on fatigue life. These results show that the new approach reproduces available experimental data remarkably well.

Stochastic-Strength-Based Damage Simulation Tool for Ceramic Matrix Composite

NASA Technical Reports Server (NTRS)

Nemeth, Noel; Bednarcyk, Brett; Pineda, Evan; Arnold, Steven; Mital, Subodh; Murthy, Pappu

2015-01-01

Reported here is a coupling of two NASA developed codes: CARES (Ceramics Analysis and Reliability Evaluation of Structures) with the MAC/GMC (Micromechanics Analysis Code/ Generalized Method of Cells) composite material analysis code. The resulting code is called FEAMAC/CARES and is constructed as an Abaqus finite element analysis UMAT (user defined material). Here we describe the FEAMAC/CARES code and an example problem (taken from the open literature) of a laminated CMC in off-axis loading is shown. FEAMAC/CARES performs stochastic-strength-based damage simulation response of a CMC under multiaxial loading using elastic stiffness reduction of the failed elements.

Carbon isotope composition of ambient CO2 and recycling: a matrix simulation model

USGS Publications Warehouse

da Silveira Lobo Sternberg, Leonel; DeAngelis, Donald L.

2002-01-01

The relationship between isotopic composition and concentration of ambient CO2 in a canopy and its associated convective boundary layer was modeled. The model divides the canopy and convective boundary layer into several layers. Photosynthesis, respiration, and exchange between each layer can be simulated by matrix equations. This simulation can be used to calculate recycling; defined here as the amount of respired CO2 re-fixed by photosynthesis relative to the total amount of respired CO2. At steady state the matrix equations can be solved for the canopy and convective boundary layer CO2 concentration and isotopic profile, which can be used to calculate a theoretical recycling index according to a previously developed equation. There is complete agreement between simulated and theoretical recycling indices for different exchange scenarios. Recycling indices from a simulation of gas exchange between a heterogeneous vegetation canopy and the troposphere also agreed with a more generalized form of the theoretical recycling equation developed here.

A size-composition resolved aerosol model for simulating the dynamics of externally mixed particles: SCRAM (v 1.0)

NASA Astrophysics Data System (ADS)

Zhu, S.; Sartelet, K. N.; Seigneur, C.

2015-06-01

The Size-Composition Resolved Aerosol Model (SCRAM) for simulating the dynamics of externally mixed atmospheric particles is presented. This new model classifies aerosols by both composition and size, based on a comprehensive combination of all chemical species and their mass-fraction sections. All three main processes involved in aerosol dynamics (coagulation, condensation/evaporation and nucleation) are included. The model is first validated by comparison with a reference solution and with results of simulations using internally mixed particles. The degree of mixing of particles is investigated in a box model simulation using data representative of air pollution in Greater Paris. The relative influence on the mixing state of the different aerosol processes (condensation/evaporation, coagulation) and of the algorithm used to model condensation/evaporation (bulk equilibrium, dynamic) is studied.

Numerical simulation of two-dimensional heat transfer in composite bodies with application to de-icing of aircraft components. Ph.D. Thesis. Final Report

NASA Technical Reports Server (NTRS)

Chao, D. F. K.

1983-01-01

Transient, numerical simulations of the de-icing of composite aircraft components by electrothermal heating were performed for a two dimensional rectangular geometry. The implicit Crank-Nicolson formulation was used to insure stability of the finite-difference heat conduction equations and the phase change in the ice layer was simulated using the Enthalpy method. The Gauss-Seidel point iterative method was used to solve the system of difference equations. Numerical solutions illustrating de-icer performance for various composite aircraft structures and environmental conditions are presented. Comparisons are made with previous studies. The simulation can also be used to solve a variety of other heat conduction problems involving composite bodies.

Numerical Simulation of Thermal Response and Ablation Behavior of a Hybrid Carbon/Carbon Composite

NASA Astrophysics Data System (ADS)

Zhang, Bai; Li, Xudong

2017-09-01

The thermal response and ablation behavior of a hybrid carbon/carbon (C/C) composite are studied herein by using a numerical model. This model is based on the energy- and mass-conservation principles as well as on the calculation of the thermophysical properties of materials. The thermal response and ablation behavior are simulated from the perspective of the matrix and fiber components of a hybrid C/C composite. The thermophysical properties during ablation are calculated, and a moving boundary is implemented to consider the recession of the ablation surface. The temperature distribution, thermophysical properties, char layer thickness, linear ablation rate, mass flow rate of the pyrolysis gases, and mass loss of the hybrid C/C composite are quantitatively predicted. This numerical study describing the thermal response and ablation behavior provides a fundamental understanding of the ablative mechanism of a hybrid C/C composite, serving as a reference and basis for further designs and optimizations of thermoprotective materials.

Numerical Simulation of Thermal Response and Ablation Behavior of a Hybrid Carbon/Carbon Composite

NASA Astrophysics Data System (ADS)

Zhang, Bai; Li, Xudong

2018-06-01

The thermal response and ablation behavior of a hybrid carbon/carbon (C/C) composite are studied herein by using a numerical model. This model is based on the energy- and mass-conservation principles as well as on the calculation of the thermophysical properties of materials. The thermal response and ablation behavior are simulated from the perspective of the matrix and fiber components of a hybrid C/C composite. The thermophysical properties during ablation are calculated, and a moving boundary is implemented to consider the recession of the ablation surface. The temperature distribution, thermophysical properties, char layer thickness, linear ablation rate, mass flow rate of the pyrolysis gases, and mass loss of the hybrid C/C composite are quantitatively predicted. This numerical study describing the thermal response and ablation behavior provides a fundamental understanding of the ablative mechanism of a hybrid C/C composite, serving as a reference and basis for further designs and optimizations of thermoprotective materials.

Micromechanics analysis of space simulated thermal deformations and stresses in continuous fiber reinforced composites

NASA Technical Reports Server (NTRS)

Bowles, David E.

1990-01-01

Space simulated thermally induced deformations and stresses in continuous fiber reinforced composites were investigated with a micromechanics analysis. The investigation focused on two primary areas. First, available explicit expressions for predicting the effective coefficients of thermal expansion (CTEs) for a composite were compared with each other, and with a finite element (FE) analysis, developed specifically for this study. Analytical comparisons were made for a wide range of fiber/matrix systems, and predicted values were compared with experimental data. The second area of investigation focused on the determination of thermally induced stress fields in the individual constituents. Stresses predicted from the FE analysis were compared to those predicted from a closed-form solution to the composite cylinder (CC) model, for two carbon fiber/epoxy composites. A global-local formulation, combining laminated plate theory and FE analysis, was used to determine the stresses in multidirectional laminates. Thermally induced damage initiation predictions were also made.

Multidisciplinary Simulation of Graphite-Composite and Cermet Fuel Elements for NTP Point of Departure Designs

NASA Technical Reports Server (NTRS)

Stewart, Mark E.; Schnitzler, Bruce G.

2015-01-01

This paper compares the expected performance of two Nuclear Thermal Propulsion fuel types. High fidelity, fluid/thermal/structural + neutronic simulations help predict the performance of graphite-composite and cermet fuel types from point of departure engine designs from the Nuclear Thermal Propulsion project. Materials and nuclear reactivity issues are reviewed for each fuel type. Thermal/structural simulations predict thermal stresses in the fuel and thermal expansion mis-match stresses in the coatings. Fluid/thermal/structural/neutronic simulations provide predictions for full fuel elements. Although NTP engines will utilize many existing chemical engine components and technologies, nuclear fuel elements are a less developed engine component and introduce design uncertainty. Consequently, these fuel element simulations provide important insights into NTP engine performance.

Multi-Objective Aerodynamic Optimization of the Streamlined Shape of High-Speed Trains Based on the Kriging Model.

PubMed

Xu, Gang; Liang, Xifeng; Yao, Shuanbao; Chen, Dawei; Li, Zhiwei

2017-01-01

Minimizing the aerodynamic drag and the lift of the train coach remains a key issue for high-speed trains. With the development of computing technology and computational fluid dynamics (CFD) in the engineering field, CFD has been successfully applied to the design process of high-speed trains. However, developing a new streamlined shape for high-speed trains with excellent aerodynamic performance requires huge computational costs. Furthermore, relationships between multiple design variables and the aerodynamic loads are seldom obtained. In the present study, the Kriging surrogate model is used to perform a multi-objective optimization of the streamlined shape of high-speed trains, where the drag and the lift of the train coach are the optimization objectives. To improve the prediction accuracy of the Kriging model, the cross-validation method is used to construct the optimal Kriging model. The optimization results show that the two objectives are efficiently optimized, indicating that the optimization strategy used in the present study can greatly improve the optimization efficiency and meet the engineering requirements.

Microdiversification in genome-streamlined ubiquitous freshwater Actinobacteria.

PubMed

Neuenschwander, Stefan M; Ghai, Rohit; Pernthaler, Jakob; Salcher, Michaela M

2018-01-01

Actinobacteria of the acI lineage are the most abundant microbes in freshwater systems, but there are so far no pure living cultures of these organisms, possibly because of metabolic dependencies on other microbes. This, in turn, has hampered an in-depth assessment of the genomic basis for their success in the environment. Here we present genomes from 16 axenic cultures of acI Actinobacteria. The isolates were not only of minute cell size, but also among the most streamlined free-living microbes, with extremely small genome sizes (1.2-1.4 Mbp) and low genomic GC content. Genome reduction in these bacteria might have led to auxotrophy for various vitamins, amino acids and reduced sulphur sources, thus creating dependencies to co-occurring organisms (the 'Black Queen' hypothesis). Genome analyses, moreover, revealed a surprising degree of inter- and intraspecific diversity in metabolic pathways, especially of carbohydrate transport and metabolism, and mainly encoded in genomic islands. The striking genotype microdiversification of acI Actinobacteria might explain their global success in highly dynamic freshwater environments with complex seasonal patterns of allochthonous and autochthonous carbon sources. We propose a new order within Actinobacteria ('Candidatus Nanopelagicales') with two new genera ('Candidatus Nanopelagicus' and 'Candidatus Planktophila') and nine new species.

State Models to Incentivize and Streamline Small Hydropower Development

DOE Office of Scientific and Technical Information (OSTI.GOV)

Curtis, Taylor; Levine, Aaron; Johnson, Kurt

In 2016, the hydropower fleet in the United States produced more than 6 percent (approximately 265,829 gigawatt-hours [GWh]) of the total net electricity generation. The median-size hydroelectric facility in the United States is 1.6 MW and 75 percent of total facilities have a nameplate capacity of 10 MW or less. Moreover, the U.S. Department of Energy's Hydropower Vision study identified approximately 79 GW hydroelectric potential beyond what is already developed. Much of the potential identified is at low-impact new stream-reaches, existing conduits, and non-powered dams with a median project size of 10 MW or less. To optimize the potential andmore » value of small hydropower development, state governments are crafting policies that provide financial assistance and expedite state and federal review processes for small hydroelectric projects. This report analyzes state-led initiatives and programs that incentivize and streamline small hydroelectric development.« less

INTEGRATION OF COST MODELS AND PROCESS SIMULATION TOOLS FOR OPTIMUM COMPOSITE MANUFACTURING PROCESS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pack, Seongchan; Wilson, Daniel; Aitharaju, Venkat

Manufacturing cost of resin transfer molded composite parts is significantly influenced by the cycle time, which is strongly related to the time for both filling and curing of the resin in the mold. The time for filling can be optimized by various injection strategies, and by suitably reducing the length of the resin flow distance during the injection. The curing time can be reduced by the usage of faster curing resins, but it requires a high pressure injection equipment, which is capital intensive. Predictive manufacturing simulation tools that are being developed recently for composite materials are able to provide variousmore » scenarios of processing conditions virtually well in advance of manufacturing the parts. In the present study, we integrate the cost models with process simulation tools to study the influence of various parameters such as injection strategies, injection pressure, compression control to minimize high pressure injection, resin curing rate, and demold time on the manufacturing cost as affected by the annual part volume. A representative automotive component was selected for the study and the results are presented in this paper« less

The QBO Impact on Stratospheric Composition as Revealed by the MERRA-2 GMI Simulation and NASA Satellite Observations

NASA Astrophysics Data System (ADS)

Oman, L.; Strahan, S. E.

2017-12-01

The Quasi-Biennial Oscillation (QBO) is the dominant mode of variability in the tropical stratosphere on interannual time scales. It has been shown to impact both stratospheric dynamics and important trace gas constituent distributions. The QBO timing with respect to the seasonal cycle in each hemisphere is significant in determining its impact on up to decadal scale variability. The composition response to the QBO is examined using the new MERRA-2 GMI "Replay" simulation, an atmospheric composition community resource, run at the native MERRA-2 approximately ½° horizontal resolution on the cubed sphere. MERRA-2 GMI is driven by the online use of key MERRA-2 meteorological quantities (i.e. U, V, T, and P) with all other variables calculated in response to those and boundary condition forcings from 1980-2016. The simulation combined with NASA's UARS and Aura satellite measurements have allowed us to quantify the impact of the QBO on stratospheric composition in more detail than was ever possible before. Revealing preferential pathways and transport timings necessary in understanding the QBO impact on composition throughout the stratosphere.

Streamlining Software Aspects of Certification: Report on the SSAC Survey

NASA Technical Reports Server (NTRS)

Hayhurst, Kelly J.; Dorsey, Cheryl A.; Knight, John C.; Leveson, Nancy G.; McCormick, G. Frank

1999-01-01

The aviation system now depends on information technology more than ever before to ensure safety and efficiency. To address concerns about the efficacy of software aspects of the certification process, the Federal Aviation Administration (FAA) began the Streamlining Software Aspects of Certification (SSAC) program. The SSAC technical team was commissioned to gather data, analyze results, and propose recommendations to maximize efficiency and minimize cost and delay, without compromising safety. The technical team conducted two public workshops to identify and prioritize software approval issues, and conducted a survey to validate the most urgent of those issues. The SSAC survey, containing over two hundred questions about the FAA's software approval process, reached over four hundred industry software developers, aircraft manufacturers, and FAA designated engineering representatives. Three hundred people responded. This report presents the SSAC program rationale, survey process, preliminary findings, and recommendations.

Component Framework for Loosely Coupled High Performance Integrated Plasma Simulations

NASA Astrophysics Data System (ADS)

Elwasif, W. R.; Bernholdt, D. E.; Shet, A. G.; Batchelor, D. B.; Foley, S.

2010-11-01

We present the design and implementation of a component-based simulation framework for the execution of coupled time-dependent plasma modeling codes. The Integrated Plasma Simulator (IPS) provides a flexible lightweight component model that streamlines the integration of stand alone codes into coupled simulations. Standalone codes are adapted to the IPS component interface specification using a thin wrapping layer implemented in the Python programming language. The framework provides services for inter-component method invocation, configuration, task, and data management, asynchronous event management, simulation monitoring, and checkpoint/restart capabilities. Services are invoked, as needed, by the computational components to coordinate the execution of different aspects of coupled simulations on Massive parallel Processing (MPP) machines. A common plasma state layer serves as the foundation for inter-component, file-based data exchange. The IPS design principles, implementation details, and execution model will be presented, along with an overview of several use cases.

Penetration of tungsten-alloy rods into composite ceramic targets: Experiments and 2-D simulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rosenberg, Z.; Dekel, E.; Hohler, V.

1998-07-10

A series of terminal ballistics experiments, with scaled tungsten-alloy penetrators, was performed on composite targets consisting of ceramic tiles glued to thick steel backing plates. Tiles of silicon-carbide, aluminum nitride, titanium-dibroide and boron-carbide were 20-80 mm thick, and impact velocity was 1.7 km/s. 2-D numerical simulations, using the PISCES code, were performed in order to simulate these shots. It is shown that a simplified version of the Johnson-Holmquist failure model can account for the penetration depths of the rods but is not enough to capture the effect of lateral release waves on these penetrations.

Simulation and Failure Analysis of Car Bumper Made of Pineapple Leaf Fiber Reinforced Composite

NASA Astrophysics Data System (ADS)

Arbintarso, E. S.; Muslim, M.; Rusianto, T.

2018-02-01

The bumper car made of the Pineapple Leaf Fiber Reinforced Composite (PLFRC) is possible to be produced with the advantage of easy to get, and cheap. Pineapple leaf fiber has chosen as a natural fiber, which the maximum of the strength of 368 MPa. The objective of this study was to determine the maximum capability of front car bumpers using Pineapple Leaf Fiber Reinforced Composite materials through the process of simulating stress analysis with Solidworks 2014 software. The aim also to know the distribution of loads that occur on the front car bumper and predict the critical point position on the design of the bumper. The result will use to develop the alternative lightweight, cheap and environmentally friendly materials in general and the development of the use of pineapple fiber for automotive purposes in particular. Simulations and failure analysis have been conducted and showed an increased impact speed in line with increased displacement, strain, and stress that occur on the surface of the bumper. The bumper can withstand collisions at a speed of less than 70 kph.

Brownfields Assessing Contractor Capabilities for Streamlined Site Investigations -- Additional Information Regarding All Appropriate Inquiries and Hiring an Environmental Professional (November 2006)

EPA Pesticide Factsheets

Guidance for Brownfields grantees and other decision makers to assess the capabilities of contractors and consultants to determine their qualifications to provide streamlined and innovative strategies for the assessment and cleanup of brownfields.

Theoretical Calculations on Sediment Transport on Titan, and the Possible Production of Streamlined Forms

NASA Technical Reports Server (NTRS)

Burr, D. M.; Emery, J. P.; Lorenz, R. D.

2005-01-01

The Cassini Imaging Science System (ISS) has been returning images of Titan, along with other Saturnian satellites. Images taken through the 938 nm methane window see down to Titan's surface. One of the purposes of the Cassini mission is to investigate possible fluid cycling on Titan. Lemniscate features shown recently and radar evidence of surface flow prompted us to consider theoretically the creation by methane fluid flow of streamlined forms on Titan. This follows work by other groups in theoretical consideration of fluid motion on Titan's surface.

Streamlining and Large Ancestral Genomes in Archaea Inferred with a Phylogenetic Birth-and-Death Model

PubMed Central

Miklós, István

2009-01-01

Homologous genes originate from a common ancestor through vertical inheritance, duplication, or horizontal gene transfer. Entire homolog families spawned by a single ancestral gene can be identified across multiple genomes based on protein sequence similarity. The sequences, however, do not always reveal conclusively the history of large families. To study the evolution of complete gene repertoires, we propose here a mathematical framework that does not rely on resolved gene family histories. We show that so-called phylogenetic profiles, formed by family sizes across multiple genomes, are sufficient to infer principal evolutionary trends. The main novelty in our approach is an efficient algorithm to compute the likelihood of a phylogenetic profile in a model of birth-and-death processes acting on a phylogeny. We examine known gene families in 28 archaeal genomes using a probabilistic model that involves lineage- and family-specific components of gene acquisition, duplication, and loss. The model enables us to consider all possible histories when inferring statistics about archaeal evolution. According to our reconstruction, most lineages are characterized by a net loss of gene families. Major increases in gene repertoire have occurred only a few times. Our reconstruction underlines the importance of persistent streamlining processes in shaping genome composition in Archaea. It also suggests that early archaeal genomes were as complex as typical modern ones, and even show signs, in the case of the methanogenic ancestor, of an extremely large gene repertoire. PMID:19570746

Chemistry Simulations Using MERRA-2 Reanalysis with the GMI CTM and Replay in Support of the Atmospheric Composition Community

NASA Technical Reports Server (NTRS)

Oman, Luke D.; Strahan, Susan E.

2016-01-01

Simulations using reanalyzed meteorological conditions have been long used to understand causes of atmospheric composition change over the recent past. Using the new Modern-Era Retrospective analysis for Research and Applications, version 2 (MERRA-2) meteorology, chemistry simulations are being conducted to create products covering 1980-2016 for the atmospheric composition community. These simulations use the Global Modeling Initiative (GMI) chemical mechanism in two different models: the GMI Chemical Transport Model (CTM) and the GEOS-5 model developed Replay mode. Replay mode means an integration of the GEOS-5 general circulation model that is incrementally adjusted each time step toward the MERRA-2 analysis. The GMI CTM is a 1 x 1.25 simulation and the MERRA-2 GMI Replay simulation uses the native MERRA-2 approximately horizontal resolution on the cubed sphere. The Replay simulations is driven by the online use of key MERRA-2 meteorological variables (i.e. U, V, T, and surface pressure) with all other variables calculated in response to those variables. A specialized set of transport diagnostics is included in both runs to better understand trace gas transport and changes over the recent past.

Chemistry Simulations using the MERRA-2 Reanalysis with the GMI CTM and Replay in Support of the Atmospheric Composition Community

NASA Technical Reports Server (NTRS)

Oman, Luke D.; Strahan, Susan E.

2017-01-01

Simulations using reanalysis meteorological fields have long been used to understand the causes of atmospheric composition change in the recent past. Using the new MERRA-2 reanalysis, we are conducting chemistry simulations to create products covering 1980-2016 for the atmospheric composition community. These simulations use the Global Modeling Initiative (GMI) chemical mechanism in two different models: the GMI Chemical Transport Model (CTM) and the GEOS-5 model in Replay mode. Replay mode means an integration of the GEOS-5 general circulation model that is incrementally adjusted each time step toward the MERRA-2 reanalysis. The GMI CTM is a 1 deg x 1.25 deg simulation and the MERRA-2 GMI Replay simulation uses the native MERRA-2 grid of approximately 1/2 deg horizontal resolution on the cubed sphere. A specialized set of transport diagnostics is included in both runs to better understand trace gas transport and its variability in the recent past.

Experimental and simulation study of flexural behaviour of woven Glass/Epoxy laminated composite plate

NASA Astrophysics Data System (ADS)

Sahoo, Sushree S.; Singh, Vijay K.; Panda, Subrata K.

2015-02-01

Flexural behaviour of cross ply laminated woven Glass/Epoxy composite plate has been investigated in this article. Flexural responses are examined by a three point bend test and tensile test carried out on INSTRON 5967 and Universal Testing Machine INSTRON 1195 respectively. The finite element model is developed in ANSYS parametric design language code and discretised using an eight nodded structural shell element. Convergence behaviour of the simulation result has been performed and validated by comparing the results with experimental values. The effects of various parameters such as side-to-thickness ratio, modular ratio on flexural behaviour of woven Glass/Epoxy laminated composite plate are discussed in details.

Ballistic Simulation Method for Lithium Ion Batteries (BASIMLIB) Using Thick Shell Composites (TSC) in LS-DYNA

DTIC Science & Technology

2016-08-04

BAllistic SImulation Method for Lithium Ion Batteries (BASIMLIB) using Thick Shell Composites (TSC) in LS-DYNA Venkatesh Babu, Dr. Matt Castanier, Dr...Objective • Objective and focus of this work is to develop a – Robust simulation methodology to model lithium - ion based batteries in its module and full...unlimited  Lithium Ion Phosphate (LiFePO4) battery cell, module and pack was modeled in LS-DYNA using both Thin Shell Layer (TSL) and Thick Shell

Numerical simulation of elasto-plastic deformation of composites: evolution of stress microfields and implications for homogenization models

NASA Astrophysics Data System (ADS)

González, C.; Segurado, J.; LLorca, J.

2004-07-01

The deformation of a composite made up of a random and homogeneous dispersion of elastic spheres in an elasto-plastic matrix was simulated by the finite element analysis of three-dimensional multiparticle cubic cells with periodic boundary conditions. "Exact" results (to a few percent) in tension and shear were determined by averaging 12 stress-strain curves obtained from cells containing 30 spheres, and they were compared with the predictions of secant homogenization models. In addition, the numerical simulations supplied detailed information of the stress microfields, which was used to ascertain the accuracy and the limitations of the homogenization models to include the nonlinear deformation of the matrix. It was found that secant approximations based on the volume-averaged second-order moment of the matrix stress tensor, combined with a highly accurate linear homogenization model, provided excellent predictions of the composite response when the matrix strain hardening rate was high. This was not the case, however, in composites which exhibited marked plastic strain localization in the matrix. The analysis of the evolution of the matrix stresses revealed that better predictions of the composite behavior can be obtained with new homogenization models which capture the essential differences in the stress carried by the elastic and plastic regions in the matrix at the onset of plastic deformation.

Numerical simulation on semi-solid die-casting of magnesium matrix composite based on orthogonal experiment

NASA Astrophysics Data System (ADS)

Liu, Huihui; He, Xiongwei; Guo, Peng

2017-04-01

Three factors (pouring temperature, injection speed and mold temperature) were selected to do three levels L9 (33)orthogonal experiment, then simulate processing of semi-solid die-casting of magnesium matrix composite by Flow-3D software. The stress distribution, temperature field and defect distribution of filling process were analyzed to find the optimized processing parameter with the help of orthogonal experiment. The results showed that semi-solid has some advantages of well-proportioned stress and temperature field, less defect concentrated in the surface. The results of simulation were the same as the experimental results.

Numerically stable finite difference simulation for ultrasonic NDE in anisotropic composites

NASA Astrophysics Data System (ADS)

Leckey, Cara A. C.; Quintanilla, Francisco Hernando; Cole, Christina M.

2018-04-01

Simulation tools can enable optimized inspection of advanced materials and complex geometry structures. Recent work at NASA Langley is focused on the development of custom simulation tools for modeling ultrasonic wave behavior in composite materials. Prior work focused on the use of a standard staggered grid finite difference type of mathematical approach, by implementing a three-dimensional (3D) anisotropic Elastodynamic Finite Integration Technique (EFIT) code. However, observations showed that the anisotropic EFIT method displays numerically unstable behavior at the locations of stress-free boundaries for some cases of anisotropic materials. This paper gives examples of the numerical instabilities observed for EFIT and discusses the source of instability. As an alternative to EFIT, the 3D Lebedev Finite Difference (LFD) method has been implemented. The paper briefly describes the LFD approach and shows examples of stable behavior in the presence of stress-free boundaries for a monoclinic anisotropy case. The LFD results are also compared to experimental results and dispersion curves.

Modeling and simulation of the debonding process of composite solid propellants

NASA Astrophysics Data System (ADS)

Feng, Tao; Xu, Jin-sheng; Han, Long; Chen, Xiong

2017-07-01

In order to study the damage evolution law of composite solid propellants, the molecular dynamics particle filled algorithm was used to establish the mesoscopic structure model of HTPB(Hydroxyl-terminated polybutadiene) propellants. The cohesive element method was employed for the adhesion interface between AP(Ammonium perchlorate) particle and HTPB matrix and the bilinear cohesive zone model was used to describe the mechanical response of the interface elements. The inversion analysis method based on Hooke-Jeeves optimization algorithm was employed to identify the parameters of cohesive zone model(CZM) of the particle/binder interface. Then, the optimized parameters were applied to the commercial finite element software ABAQUS to simulate the damage evolution process for AP particle and HTPB matrix, including the initiation, development, gathering and macroscopic crack. Finally, the stress-strain simulation curve was compared with the experiment curves. The result shows that the bilinear cohesive zone model can accurately describe the debonding and fracture process between the AP particles and HTPB matrix under the uniaxial tension loading.

Computational fluid dynamics modeling of laminar, transitional, and turbulent flows with sensitivity to streamline curvature and rotational effects

NASA Astrophysics Data System (ADS)

Chitta, Varun

Modeling of complex flows involving the combined effects of flow transition and streamline curvature using two advanced turbulence models, one in the Reynolds-averaged Navier-Stokes (RANS) category and the other in the hybrid RANS-Large eddy simulation (LES) category is considered in this research effort. In the first part of the research, a new scalar eddy-viscosity model (EVM) is proposed, designed to exhibit physically correct responses to flow transition, streamline curvature, and system rotation effects. The four equation model developed herein is a curvature-sensitized version of a commercially available three-equation transition-sensitive model. The physical effects of rotation and curvature (RC) enter the model through the added transport equation, analogous to a transverse turbulent velocity scale. The eddy-viscosity has been redefined such that the proposed model is constrained to reduce to the original transition-sensitive model definition in nonrotating flows or in regions with negligible RC effects. In the second part of the research, the developed four-equation model is combined with a LES technique using a new hybrid modeling framework, dynamic hybrid RANS-LES. The new framework is highly generalized, allowing coupling of any desired LES model with any given RANS model and addresses several deficiencies inherent in most current hybrid models. In the present research effort, the DHRL model comprises of the proposed four-equation model for RANS component and the MILES scheme for LES component. Both the models were implemented into a commercial computational fluid dynamics (CFD) solver and tested on a number of engineering and generic flow problems. Results from both the RANS and hybrid models show successful resolution of the combined effects of transition and curvature with reasonable engineering accuracy, and for only a small increase in computational cost. In addition, results from the hybrid model indicate significant levels of turbulent

Alignment of carbon iron into polydimethylsiloxane to create conductive composite with low percolation threshold and high piezoresistivity: experiment and simulation

NASA Astrophysics Data System (ADS)

Dong, Shuai; Wang, Xiaojie

2017-04-01

In this study, various amounts of carbonyl iron particles (CIPs) were cured into polydimethylsiloxane (PDMS) matrix under a magnetic field up to 1.0 T to create anisotropy of conductive composite materials. The electrical resistivity for the longitudinal direction was measured as a function of filler volume fraction to understand the electrical percolation behavior. The electrical percolation threshold (EPT) of CIPs-PDMS composite cured under a magnetic field can be as low as 0.1 vol%, which is much less than most of those studies in particulate composites. Meanwhile, the effects of compressive strain on the electrical properties of CIPs-PDMS composites were also investigated. The strain sensitivity depends on filler volume fraction and decreases with the increasing of compressive strain. It has been found that the composites containing a small amount of CI particles curing under a magnetic field exhibit a high strain sensitivity of over 150. Based on the morphological observation of the composite structures, a two-dimensional stick percolation model for the CIPs-PDMS composites has been established. The Monte Carlo simulation is performed to obtain the percolation probability. The simulation results in prediction of the values of EPTs are close to that of experimental measurements. It demonstrates that the low percolation behavior of CIPs-PDMS composites is due to the average length of particle chains forming by external magnetic field.

Studying Turbulence Using Numerical Simulation Databases. Part 6; Proceedings of the 1996 Summer Program

NASA Technical Reports Server (NTRS)

1996-01-01

Topics considered include: New approach to turbulence modeling; Second moment closure analysis of the backstep flow database; Prediction of the backflow and recovery regions in the backward facing step at various Reynolds numbers; Turbulent flame propagation in partially premixed flames; Ensemble averaged dynamic modeling. Also included a study of the turbulence structures of wall-bounded shear flows; Simulation and modeling of the elliptic streamline flow.

A novel drug management system in the Febuxostat versus Allopurinol Streamlined Trial: A description of a pharmacy system designed to supply medications directly to patients within a prospective multicenter randomised clinical trial.

PubMed

Rogers, Amy; Flynn, Robert Wv; McDonnell, Patrick; Mackenzie, Isla S; MacDonald, Thomas M

2016-12-01

Trials of investigational medicinal products are required to adhere to strict guidelines with regard to the handling and supply of medication. Information technology offers opportunities to approach clinical trial methodology in new ways. This report summarises a novel pharmacy system designed to supply trial medications directly to patients by post in the Febuxostat versus Allopurinol Streamlined Trial. A bespoke web-based software package was designed to facilitate the direct supply of trial medications to Febuxostat versus Allopurinol Streamlined Trial participants from a pharmacy based in the Medicines Monitoring Unit, University of Dundee. To date, 65,467 packs of medication have been dispensed using the system to 3978 patients. Up to 238 packs per day have been dispensed. The Medicines Monitoring Unit Febuxostat versus Allopurinol Streamlined Trial drug management system is an effective method of administering the complex drug supply requirements of a large-scale clinical trial with advantages over existing arrangements. A low rate of loss to follow-up in the Febuxostat versus Allopurinol Streamlined Trial may be attributable to the drug management system. © The Author(s) 2016.

Environmental and Mechanical Stability of Environmental Barrier Coated SA Tyrannohex SiC Composites Under Simulated Turbine Engine Environments

NASA Technical Reports Server (NTRS)

Zhu, Dongming; Halbig, Michael Charles; Sing, Mrityunjay

2014-01-01

The environmental stability and thermal gradient cyclic durability performance of SA Tyrannohex composites were investigated for turbine engine component applications. The work has been focused on investigating the combustion rig recession, cyclic thermal stress resistance and thermomechanical low cycle fatigue of uncoated and environmental barrier coated Tyrannohex SiC SA composites in simulated turbine engine combustion water vapor, thermal gradients, and mechanical loading conditions. Flexural strength degradations have been evaluated, and the upper limits of operating temperature conditions for the SA composite material systems are discussed based on the experimental results.

Wear resistance of packable resin composites after simulated toothbrushing test.

PubMed

Wang, Linda; Garcia, Fernanda Cristina Pimentel; Amarante de Araújo, Paulo; Franco, Eduardo Batista; Mondelli, Rafael Francisco Lia

2004-01-01

The purpose of this study was to determine the wear resistance of five different packable composites versus two different composite controls using a laboratory toothbrushing simulation test. Twelve samples measuring 5 mm in diameter and 3 mm thick were prepared from the following resin composites: Packable resin composites SureFil (Dentsply Ind. Com. Ltda, Petrópolis, Rio de Janeiro, Brazil), Alert (Jeneric Pentron Incorporated, Wallingford, CT, USA), Filtek P60 (3M ESPE Dental Products, St. Paul, MN, USA), Prodigy Condensable (sds Kerr, Orange CA, USA), Solitaire (Heraeus Kulzer GmbH, Wehrheim, Germany), and control resin composites Z100 Restorative (3M ESPE) and Silux Plus (3M ESPE). Finishing and polishing were conducted with Sof-Lex disks (3M ESPE), and baseline weight (grams) and surface roughness (measured with Hommel Tester T 1000, Hommelwerke, GmbH, Alte Tuttinger Strebe 20. D-7730 VS-Schwenningen, Germany) were recorded. Specimens were aged for 2 weeks until they reached a weight that remained constant for 5 consecutive days, and then were subjected to 100,000 cycles of brushing (representative of 4.2 yr) using a toothbrushing testing machine. Toothbrush heads with soft bristle tips (Colgate Classic, Colgate-Palmolive Co., Osasco, São Paulo, Brazil) with dentifrice suspension (Colgate MFP, Colgate-Palmolive Co.) in deionized water were used under a 200 g load. Changes in weight and surface roughness were determined after toothbrushing cycles. Significant differences of weight loss and surface roughness were found (paired t-test, p < .05). Weight loss percentage (mean [SD]) ranged from 0.38 to 1.69% (analysis of variance and Tukey's least significant difference, p < .05); the weight loss of the materials ranked from least to most as follows: SureFil (0.38 [0.56]), Alert (0.52 [0.18]), Z100 (1.16 [0.27]), Filtek P60 (1.31 [0.17]), Solitaire (1.51 [0.45]), Prodigy Condensable (1.55 [0.471), and Silux Plus (1.69 [0.66]). Regarding surface roughness, Prodigy

Impact of eliminating fracture intersection nodes in multiphase compositional flow simulation

NASA Astrophysics Data System (ADS)

Walton, Kenneth M.; Unger, Andre J. A.; Ioannidis, Marios A.; Parker, Beth L.

2017-04-01

Algebraic elimination of nodes at discrete fracture intersections via the star-delta technique has proven to be a valuable tool for making multiphase numerical simulations more tractable and efficient. This study examines the assumptions of the star-delta technique and exposes its effects in a 3-D, multiphase context for advective and dispersive/diffusive fluxes. Key issues of relative permeability-saturation-capillary pressure (kr-S-Pc) and capillary barriers at fracture-fracture intersections are discussed. This study uses a multiphase compositional, finite difference numerical model in discrete fracture network (DFN) and discrete fracture-matrix (DFM) modes. It verifies that the numerical model replicates analytical solutions and performs adequately in convergence exercises (conservative and decaying tracer, one and two-phase flow, DFM and DFN domains). The study culminates in simulations of a two-phase laboratory experiment in which a fluid invades a simple fracture intersection. The experiment and simulations evoke different invading fluid flow paths by varying fracture apertures as oil invades water-filled fractures and as water invades air-filled fractures. Results indicate that the node elimination technique as implemented in numerical model correctly reproduces the long-term flow path of the invading fluid, but that short-term temporal effects of the capillary traps and barriers arising from the intersection node are lost.

Streamlined research funding using short proposals and accelerated peer review: an observational study.

PubMed

Barnett, Adrian G; Herbert, Danielle L; Campbell, Megan; Daly, Naomi; Roberts, Jason A; Mudge, Alison; Graves, Nicholas

2015-02-07

Despite the widely recognised importance of sustainable health care systems, health services research remains generally underfunded in Australia. The Australian Centre for Health Services Innovation (AusHSI) is funding health services research in the state of Queensland. AusHSI has developed a streamlined protocol for applying and awarding funding using a short proposal and accelerated peer review. An observational study of proposals for four health services research funding rounds from May 2012 to November 2013. A short proposal of less than 1,200 words was submitted using a secure web-based portal. The primary outcome measures are: time spent preparing proposals; a simplified scoring of grant proposals (reject, revise or accept for interview) by a scientific review committee; and progressing from submission to funding outcomes within eight weeks. Proposals outside of health services research were deemed ineligible. There were 228 eligible proposals across 4 funding rounds: from 29% to 79% were shortlisted and 9% to 32% were accepted for interview. Success rates increased from 6% (in 2012) to 16% (in 2013) of eligible proposals. Applicants were notified of the outcomes within two weeks from the interview; which was a maximum of eight weeks after the submission deadline. Applicants spent 7 days on average preparing their proposal. Applicants with a ranking of reject or revise received written feedback and suggested improvements for their proposals, and resubmissions composed one third of the 2013 rounds. The AusHSI funding scheme is a streamlined application process that has simplified the process of allocating health services research funding for both applicants and peer reviewers. The AusHSI process has minimised the time from submission to notification of funding outcomes.

A streamlined artificial variable free version of simplex method.

PubMed

Inayatullah, Syed; Touheed, Nasir; Imtiaz, Muhammad

2015-01-01

This paper proposes a streamlined form of simplex method which provides some great benefits over traditional simplex method. For instance, it does not need any kind of artificial variables or artificial constraints; it could start with any feasible or infeasible basis of an LP. This method follows the same pivoting sequence as of simplex phase 1 without showing any explicit description of artificial variables which also makes it space efficient. Later in this paper, a dual version of the new method has also been presented which provides a way to easily implement the phase 1 of traditional dual simplex method. For a problem having an initial basis which is both primal and dual infeasible, our methods provide full freedom to the user, that whether to start with primal artificial free version or dual artificial free version without making any reformulation to the LP structure. Last but not the least, it provides a teaching aid for the teachers who want to teach feasibility achievement as a separate topic before teaching optimality achievement.

A Streamlined Artificial Variable Free Version of Simplex Method

PubMed Central

Inayatullah, Syed; Touheed, Nasir; Imtiaz, Muhammad

2015-01-01

This paper proposes a streamlined form of simplex method which provides some great benefits over traditional simplex method. For instance, it does not need any kind of artificial variables or artificial constraints; it could start with any feasible or infeasible basis of an LP. This method follows the same pivoting sequence as of simplex phase 1 without showing any explicit description of artificial variables which also makes it space efficient. Later in this paper, a dual version of the new method has also been presented which provides a way to easily implement the phase 1 of traditional dual simplex method. For a problem having an initial basis which is both primal and dual infeasible, our methods provide full freedom to the user, that whether to start with primal artificial free version or dual artificial free version without making any reformulation to the LP structure. Last but not the least, it provides a teaching aid for the teachers who want to teach feasibility achievement as a separate topic before teaching optimality achievement. PMID:25767883

Streamlining Building Efficiency Evaluation with DOE's Asset Score Preview

DOE Office of Scientific and Technical Information (OSTI.GOV)

Goel, Supriya; Wang, Nora; Gonzalez, Juan

2016-08-26

Building Energy Asset Score (Asset Score), developed by the Pacific Northwest National Laboratory (PNNL) for the U.S. Department of Energy (DOE), is a tool to help building owners and managers assess the efficiency of a building's energy-related systems and encourage investment in cost-effective improvements. The Asset Score uses an EnergyPlus model to provide a quick assessment of building energy performance with minimum user inputs of building characteristics and identifies upgrade opportunities. Even with a reduced set of user inputs, data collection remains a challenge for wide-spread adoption, especially when evaluating a large number of buildings. To address this, Asset Scoremore » Preview was developed to allow users to enter as few as seven building characteristics to quickly assess their buildings before a more in-depth analysis. A streamlined assessment from Preview to full Asset Score provides an easy entry point and also enables users who manage a large number of buildings to screen and prioritize buildings that can benefit most from a more detailed evaluation and possible energy efficiency upgrades without intensive data collection.« less

Ground-based simulation of the Earth's upper atmosphere oxygen impact on polymer composites with nanosized fillers

NASA Astrophysics Data System (ADS)

Novikov, Lev; Chernik, Vladimir; Voronina, Ekaterina; Chechenin, Nikolay; Samokhina, Maria S.; Bondarenko, Gennady G.; Gaidar, Anna I.; Vorobyeva, Ekaterina A.; Petrov, Dmitrii V.; Chirskaya, Natalia P.

The improvement of durability of polymer composites to the space environment impact is a very important task because these materials are considered currently as very promising type of materials for aerospace engineering. By embedding various nanosized fillers into a polymer matrix it is possible to obtain composites with required mechanical, thermal, electrical and optic properties. However, while developing such materials for operation in low Earth orbits (LEO), it is necessary to study thoroughly their durability to the impact of atomic oxygen (AO) of the Earth’s upper atmosphere, because AO is the main factor that causes erosion and damage of spacecraft surface materials in LEO. Ground-based simulation of AO impact on polymer composites was performed on a magnetoplasmadynamic accelerator developed at Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University. Polymer composite samples which were prepared as films of 30-50 mum thickness with different amount (3-20 wt%) of various inorganic and organic nanofillers including nanoparticles of metal oxides and carbides as well as polyethoxysiloxanes and carbon nanotubes (CNTs), were exposed to hyperthermal AO flow, and mass losses of samples were estimated. Changes in the structure of composite surface and in material optical properties were studied. The experiments demonstrated that embedding nanosized fillers into a polymer matrix can significantly reduced mass losses, and the good dispersion of fillers improves AO durability in comparison with initial polymers [1]. The computer simulation within the developed 2D Monte-Carlo model demonstrated a good agreement with the experimental data [2]. Special attention was given to the study of AO impact on aligned multiwalled CNTs and CNT-based composites [3]. Some results of computer simulation of hyperthermal oxygen atom interaction with CNT and graphene as well as with polymers are presented to discuss elementary processes which occur in nanostructures

Validation of numerical simulations for nano-aluminum composite solid propellants

NASA Astrophysics Data System (ADS)

Yan, Allen H.

2011-12-01

Nano-aluminum is of interest as an energetic additive in composite solid propellant formulations for its demonstrated ability to increase combustion efficiency and burning rate. However, due to the current cost of nano-aluminum and the associated safety risks associated with propellant testing, it may not always be practical to spend the time and effort to mix, cast, and thoroughly evaluate the burning rate of a new formulation. To provide an alternative method of determining this parameter, numerical methods have been developed to predict the performance of nano-aluminum composite propellants, but these codes still require thorough validation before application. For this purpose, six propellant compositions were formulated, fully characterized, and burn rates were measured at several pressures between 34.0 and 129.3 atmospheres at room temperature, 20°C, and at an elevated temperature of 71.1°C in order to test the code's ability to predict pressure dependent burn rate and temperature sensitivity. To ensure the most accurate model possible, special emphasis was placed on characterizing the size distribution of the constituent nano-aluminum and ammonium perchlorate powders through optical diffraction or optical imaging techniques. Experimental burn rate is compared to the propellant combustion model and shows excellent agreement within 5% for a range of formulations and pressures, however under other conditions the model deviates by as much as 21%. An analysis of the results suggests that the current framework of the numerical model is unable to accurately simulate all the combustion physics of high aluminum content propellants, and suggestions for improvements are identified.

Optical ensemble analysis of intraocular lens performance through a simulated clinical trial with ZEMAX.

PubMed

Zhao, Huawei

2009-01-01

A ZEMAX model was constructed to simulate a clinical trial of intraocular lenses (IOLs) based on a clinically oriented Monte Carlo ensemble analysis using postoperative ocular parameters. The purpose of this model is to test the feasibility of streamlining and optimizing both the design process and the clinical testing of IOLs. This optical ensemble analysis (OEA) is also validated. Simulated pseudophakic eyes were generated by using the tolerancing and programming features of ZEMAX optical design software. OEA methodology was verified by demonstrating that the results of clinical performance simulations were consistent with previously published clinical performance data using the same types of IOLs. From these results we conclude that the OEA method can objectively simulate the potential clinical trial performance of IOLs.

Smart management of sample dilution using an artificial neural network to achieve streamlined processes and saving resources: the automated nephelometric testing of serum free light chain as case study.

PubMed

Ialongo, Cristiano; Pieri, Massimo; Bernardini, Sergio

2017-02-01

Saving resources is a paramount issue for the modern laboratory, and new trainable as well as smart technologies can be used to allow the automated instrumentation to manage samples more efficiently in order to achieve streamlined processes. In this regard the serum free light chain (sFLC) testing represents an interesting challenge, as it usually causes using a number of assays before achieving an acceptable result within the analytical range. An artificial neural network based on the multi-layer perceptron (MLP-ANN) was used to infer the starting dilution status of sFLC samples based on the information available through the laboratory information system (LIS). After the learning phase, the MLP-ANN simulation was applied to the nephelometric testing routinely performed in our laboratory on a BN ProSpec® System analyzer (Siemens Helathcare) using the N Latex FLC kit. The MLP-ANN reduced the serum kappa free light chain (κ-FLC) and serum lambda free light chain (λ-FLC) wasted tests by 69.4% and 70.8% with respect to the naïve stepwise dilution scheme used by the automated analyzer, and by 64.9% and 66.9% compared to a "rational" dilution scheme based on a 4-step dilution. Although it was restricted to follow-up samples, the MLP-ANN showed good predictive performance, which alongside the possibility to implement it in any automated system, made it a suitable solution for achieving streamlined laboratory processes and saving resources.

Resin Flow Behavior Simulation of Grooved Foam Sandwich Composites with the Vacuum Assisted Resin Infusion (VARI) Molding Process

PubMed Central

Zhao, Chenhui; Zhang, Guangcheng; Wu, Yibo

2012-01-01

The resin flow behavior in the vacuum assisted resin infusion molding process (VARI) of foam sandwich composites was studied by both visualization flow experiments and computer simulation. Both experimental and simulation results show that: the distribution medium (DM) leads to a shorter molding filling time in grooved foam sandwich composites via the VARI process, and the mold filling time is linearly reduced with the increase of the ratio of DM/Preform. Patterns of the resin sources have a significant influence on the resin filling time. The filling time of center source is shorter than that of edge pattern. Point pattern results in longer filling time than of linear source. Short edge/center patterns need a longer time to fill the mould compared with Long edge/center sources.

Mineralization behavior and interface properties of BG-PVA/bone composite implants in simulated body fluid.

PubMed

Ma, Yanxuan; Zheng, Yudong; Huang, Xiaoshan; Xi, Tingfei; Lin, Xiaodan; Han, Dongfei; Song, Wenhui

2010-04-01

Due to the non-bioactivity and poor conjunction performance of present cartilage prostheses, the main work here is to develop the bioactive glass-polyvinyl alcohol hydrogel articular cartilage/bone (BG-PVA/bone) composite implants. The essential criterion for a biomaterial to bond with living bone is well-matched mechanical properties as well as biocompatibility and bioactivity. In vitro studies on the formation of a surface layer of carbonate hydroxyl apatite (HCA) and the corresponding variation of the properties of biomaterials are imperative for their clinical application. In this paper, the mineralization behavior and variation of the interface properties of BG-PVA/bone composites were studied in vitro by using simulated body fluid (SBF). The mineralization and HCA layer formed on the interface between the BG-PVA hydrogel and bone in SBF could provide the composites with bioactivity and firmer combination. The compression property, shear strength and interface morphology of BG-PVA/bone composite implants varying with the immersion time in SBF were characterized. Also, the influence laws of the immersion time, content of BG in the composites and aperture of bones to the mineralization behavior and interface properties were investigated. The good mineralization behavior and enhanced conjunction performance of BG-PVA/bone composites demonstrated that this kind of composite implant might be more appropriate cartilage replacements.

Damage progression in Composite Structures

NASA Technical Reports Server (NTRS)

Minnetyan, Levon

1996-01-01

A computational simulation tool is used to evaluate the various stages of damage progression in composite materials during Iosipescu sheat testing. Unidirectional composite specimens with either the major or minor material axis in the load direction are considered. Damage progression characteristics are described for each specimen using two types of boundary conditions. A procedure is outlined regarding the use of computational simulation in composites testing. Iosipescu shear testing using the V-notched beam specimen is a convenient method to measure both shear strength and shear stiffness simultaneously. The evaluation of composite test response can be made more productive and informative via computational simulation of progressive damage and fracture. Computational simulation performs a complete evaluation of laminated composite fracture via assessment of ply and subply level damage/fracture processes.

Numerical simulation on the seismic absorption effect of the cushion in rigid-pile composite foundation

NASA Astrophysics Data System (ADS)

Han, Xiaolei; Li, Yaokun; Ji, Jing; Ying, Junhao; Li, Weichen; Dai, Baicheng

2016-06-01

In order to quantitatively study the seismic absorption effect of the cushion on a superstructure, a numerical simulation and parametric study are carried out on the overall FEA model of a rigid-pile composite foundation in ABAQUS. A simulation of a shaking table test on a rigid mass block is first completed with ABAQUS and EERA, and the effectiveness of the Drucker-Prager constitutive model and the finite-infinite element coupling method is proved. Dynamic time-history analysis of the overall model under frequent and rare earthquakes is carried out using seismic waves from the El Centro, Kobe, and Bonds earthquakes. The different responses of rigid-pile composite foundations and pile-raft foundations are discussed. Furthermore, the influence of thickness and modulus of cushion, and ground acceleration on the seismic absorption effect of the cushion are analyzed. The results show that: 1) the seismic absorption effect of a cushion is good under rare earthquakes, with an absorption ratio of about 0.85; and 2) the seismic absorption effect is strongly affected by cushion thickness and ground acceleration.

Simulation of Cold Flow in a Truncated Ideal Nozzle with Film Cooling

NASA Technical Reports Server (NTRS)

Braman, Kalen; Ruf, Joseph

2015-01-01

Flow transients during rocket start-up and shut-down can lead to significant side loads on rocket nozzles. The capability to estimate these side loads computationally can streamline the nozzle design process. Towards this goal, the flow in a truncated ideal contour (TIC) nozzle has been simulated for a range of nozzle pressure ratios (NPRs) aimed to match a series of cold flow experiments performed at the NASA MSFC Nozzle Test Facility. These simulations were performed with varying turbulence model choices and with four different versions of the TIC nozzle model geometry, each of which was created with a different simplification to the test article geometry.

SimBRS: A University/Industry Consortium Focused on Simulation Based Solutions for Ground Vehicles

DTIC Science & Technology

2009-07-29

plan is to use the SimBRS contract mechanism to streamline a process that applies research funds into a managed program, that is cognizant to the... designs . Therefore, the challenge for the SimBRS team is to establish an approach based on the capacity of measured data and simulations to support ...by systematically relating appropriate results from measurements and applied research in engineering and science. In turn, basic research and

Simulating Initial and Progressive Failure of Open-Hole Composite Laminates under Tension

NASA Astrophysics Data System (ADS)

Guo, Zhangxin; Zhu, Hao; Li, Yongcun; Han, Xiaoping; Wang, Zhihua

2016-12-01

A finite element (FE) model is developed for the progressive failure analysis of fiber reinforced polymer laminates. The failure criterion for fiber and matrix failure is implemented in the FE code Abaqus using user-defined material subroutine UMAT. The gradual degradation of the material properties is controlled by the individual fracture energies of fiber and matrix. The failure and damage in composite laminates containing a central hole subjected to uniaxial tension are simulated. The numerical results show that the damage model can be used to accurately predicte the progressive failure behaviour both qualitatively and quantitatively.

Computational composite mechanics for aerospace propulsion structures

NASA Technical Reports Server (NTRS)

Chamis, C. C.

1986-01-01

Specialty methods are presented for the computational simulation of specific composite behavior. These methods encompass all aspects of composite mechanics, impact, progressive fracture and component specific simulation. Some of these methods are structured to computationally simulate, in parallel, the composite behavior and history from the initial fabrication through several missions and even to fracture. Select methods and typical results obtained from such simulations are described in detail in order to demonstrate the effectiveness of computationally simulating (1) complex composite structural behavior in general and (2) specific aerospace propulsion structural components in particular.

Computational composite mechanics for aerospace propulsion structures

NASA Technical Reports Server (NTRS)

Chamis, Christos C.

1987-01-01

Specialty methods are presented for the computational simulation of specific composite behavior. These methods encompass all aspects of composite mechanics, impact, progressive fracture and component specific simulation. Some of these methods are structured to computationally simulate, in parallel, the composite behavior and history from the initial frabrication through several missions and even to fracture. Select methods and typical results obtained from such simulations are described in detail in order to demonstrate the effectiveness of computationally simulating: (1) complex composite structural behavior in general, and (2) specific aerospace propulsion structural components in particular.

Composite mechanics for engine structures

NASA Technical Reports Server (NTRS)

Chamis, Christos C.

1987-01-01

Recent research activities and accomplishments at Lewis Research Center on composite mechanics for engine structures are summarized. The activities focused mainly on developing procedures for the computational simulation of composite intrinsic and structural behavior. The computational simulation encompasses all aspects of composite mechanics, advanced three-dimensional finite-element methods, damage tolerance, composite structural and dynamic response, and structural tailoring and optimization.

Composite mechanics for engine structures

NASA Technical Reports Server (NTRS)

Chamis, Christos C.

1989-01-01

Recent research activities and accomplishments at Lewis Research Center on composite mechanics for engine structures are summarized. The activities focused mainly on developing procedures for the computational simulation of composite intrinsic and structural behavior. The computational simulation encompasses all aspects of composite mechanics, advanced three-dimensional finite-element methods, damage tolerance, composite structural and dynamic response, and structural tailoring and optimization.

The Impact of Simulated Nature on Patient Outcomes: A Study of Photographic Sky Compositions.

PubMed

Pati, Debajyoti; Freier, Patricia; O'Boyle, Michael; Amor, Cherif; Valipoor, Shabboo

2016-01-01

To examine whether incorporation of simulated nature, in the form of ceiling mounted photographic sky compositions, influences patient outcomes. Previous studies have shown that most forms of nature exposure have a positive influence on patients. However, earlier studies have mostly focused on wall-hung nature representations. The emergence of simulated nature products has raised the question regarding the effects of the new product on patient outcomes. A between-subject experimental design was adopted, where outcomes from five inpatient rooms with sky composition ceiling fixture were compared to corresponding outcomes in five identical rooms without the intervention. Data were collected from a total of 181 subjects on 11 outcomes. Independent sample tests were performed to identify differences in mean outcomes. Significant positive outcomes were observed in environmental satisfaction and diastolic blood pressure (BP). Environmental satisfaction in the experimental group was 12.4% higher than the control group. Direction of association for diastolic BP, nausea/indigestion medication, acute stress, anxiety, pain, and environmental satisfaction were consistent with a priori hypothesis. A post hoc exploratory assessment involving patients who did not self-request additional pain and sleep medication demonstrated confirmatory directions for all outcomes except Systolic BP, and statistically significant outcomes for Acute Stress and Anxiety-Acute Stress and Anxiety levels of the experimental group subjects was 53.4% and 34.79% lower, respectively, than that of the control group subjects. Salutogenic benefits of photographic sky compositions render them better than traditional ceiling tiles and offer an alternative to other nature interventions. © The Author(s) 2015.

Transonic streamline of symmetric wing under the influence unilateral oscillations characterized by the spectrum of two frequencies

NASA Astrophysics Data System (ADS)

Zamuraev, V. P.; Kalinina, A. P.

2017-10-01

Forced high-frequency vibrations of the airfoil surface part with the amplitude almost equal to the sound velocity can change significantly the lift force of the symmetric profile streamlined at zero angle of attack. The oscillation consists of two harmonics. The ratio of harmonics frequencies values is equal to 2. The present work shows that the aerodynamic properties depend significantly on the specific energy contribution of each frequency.

Simulating the Response of a Composite Honeycomb Energy Absorber. Part 1; Dynamic Crushing of Components and Multi-Terrain Impacts

NASA Technical Reports Server (NTRS)

Jackson, Karen E.; Fasanella, Edwin L.; Polanco, Michael A.

2012-01-01

This paper describes the experimental and analytical evaluation of an externally deployable composite honeycomb structure that is designed to attenuate impact energy during helicopter crashes. The concept, designated the Deployable Energy Absorber (DEA), utilizes an expandable Kevlar (Registered Trademark) honeycomb to dissipate kinetic energy through crushing. The DEA incorporates a unique flexible hinge design that allows the honeycomb to be packaged and stowed until needed for deployment. Experimental evaluation of the DEA included dynamic crush tests of multi-cell components and vertical drop tests of a composite fuselage section, retrofitted with DEA blocks, onto multi-terrain. Finite element models of the test articles were developed and simulations were performed using the transient dynamic code, LSDYNA (Registered Trademark). In each simulation, the DEA was represented using shell elements assigned two different material properties: Mat 24, an isotropic piecewise linear plasticity model, and Mat 58, a continuum damage mechanics model used to represent laminated composite fabrics. DEA model development and test-analysis comparisons are presented.

Simulation Based Optimization of Complex Monolithic Composite Structures Using Cellular Core Technology

NASA Astrophysics Data System (ADS)

Hickmott, Curtis W.

Cellular core tooling is a new technology which has the capability to manufacture complex integrated monolithic composite structures. This novel tooling method utilizes thermoplastic cellular cores as inner tooling. The semi-rigid nature of the cellular cores makes them convenient for lay-up, and under autoclave temperature and pressure they soften and expand providing uniform compaction on all surfaces including internal features such as ribs and spar tubes. This process has the capability of developing fully optimized aerospace structures by reducing or eliminating assembly using fasteners or bonded joints. The technology is studied in the context of evaluating its capabilities, advantages, and limitations in developing high quality structures. The complex nature of these parts has led to development of a model using the Finite Element Analysis (FEA) software Abaqus and the plug-in COMPRO Common Component Architecture (CCA) provided by Convergent Manufacturing Technologies. This model utilizes a "virtual autoclave" technique to simulate temperature profiles, resin flow paths, and ultimately deformation from residual stress. A model has been developed simulating the temperature profile during curing of composite parts made with the cellular core technology. While modeling of composites has been performed in the past, this project will look to take this existing knowledge and apply it to this new manufacturing method capable of building more complex parts and develop a model designed specifically for building large, complex components with a high degree of accuracy. The model development has been carried out in conjunction with experimental validation. A double box beam structure was chosen for analysis to determine the effects of the technology on internal ribs and joints. Double box beams were manufactured and sectioned into T-joints for characterization. Mechanical behavior of T-joints was performed using the T-joint pull-off test and compared to traditional

Design, Simulation and Experimental Evaluation of Tri-Phasic Piezoelectric Composite Transducers

NASA Astrophysics Data System (ADS)

Tamez, Juan Pedro

Piezoelectric ceramics exhibit excellent piezoelectric and dielectric properties that is the basis of practically all transducers and piezoelectric devices, but their inherent properties, such as brittleness, non-ductility and poor shapeability may limit their applications in areas such as vibration sensing, impact detection, structural health monitoring and other reinforced structures and energy harvesting. To compensate for such limitations, the 1-3 piezoelectric composites transducers have become the material of choice for many high performance ultrasound transducers since it was invented in the late 1970's [ref. Newnham/Cross]. Extensive studies on 1-3 composites have been performed since then to improve the performance of a transducer by modifying their electromechanical coupling, bandwidth, quality factor, and flexibility and by reducing or eliminating the cross talk, i.e., induced noise between the active piezoelectric elements, especially in high power and low frequency applications. These fundamental issues, their possible solutions and their wide impact underline the motivation of the current work in this dissertation report. The motivation for this dissertation was to study and provide a foundation to designing multiphasic piezoelectric transducers that could be useful for multitude of applications. The goal was to improve the 1-3 diphasic composite transducer by eliminating the cross talk between the active piezoelectric elements while maintaining and improving the figures of merit of the design. To achieve the ultimate goal, the steps outlined below were followed: i. Understanding the theoretical and mathematical modeling for tri-phasic piezoelectric composite. ii. Implement Finite Element Analysis (FEA) and simulations of tri-phasic piezoelectric composites where the different active piezoelectric material PZT-5H and PMN-30%PT is surrounded by a vacuum phase that is enclosed by a hexagonal polymer walls. iii. Propose a redesign of the tri

Terradynamically streamlined shapes in animals and robots enhance traversability through densely cluttered terrain.

PubMed

Li, Chen; Pullin, Andrew O; Haldane, Duncan W; Lam, Han K; Fearing, Ronald S; Full, Robert J

2015-06-22

Many animals, modern aircraft, and underwater vehicles use fusiform, streamlined body shapes that reduce fluid dynamic drag to achieve fast and effective locomotion in air and water. Similarly, numerous small terrestrial animals move through cluttered terrain where three-dimensional, multi-component obstacles like grass, shrubs, vines, and leaf litter also resist motion, but it is unknown whether their body shape plays a major role in traversal. Few ground vehicles or terrestrial robots have used body shape to more effectively traverse environments such as cluttered terrain. Here, we challenged forest-floor-dwelling discoid cockroaches (Blaberus discoidalis) possessing a thin, rounded body to traverse tall, narrowly spaced, vertical, grass-like compliant beams. Animals displayed high traversal performance (79 ± 12% probability and 3.4 ± 0.7 s time). Although we observed diverse obstacle traversal strategies, cockroaches primarily (48 ± 9% probability) used a novel roll maneuver, a form of natural parkour, allowing them to rapidly traverse obstacle gaps narrower than half their body width (2.0 ± 0.5 s traversal time). Reduction of body roundness by addition of artificial shells nearly inhibited roll maneuvers and decreased traversal performance. Inspired by this discovery, we added a thin, rounded exoskeletal shell to a legged robot with a nearly cuboidal body, common to many existing terrestrial robots. Without adding sensory feedback or changing the open-loop control, the rounded shell enabled the robot to traverse beam obstacles with gaps narrower than shell width via body roll. Such terradynamically 'streamlined' shapes can reduce terrain resistance and enhance traversability by assisting effective body reorientation via distributed mechanical feedback. Our findings highlight the need to consider body shape to improve robot mobility in real-world terrain often filled with clutter, and to develop better locomotor-ground contact models to understand

A Method for Determining the Rate of Heat Transfer from a Wing or Streamline Body

NASA Technical Reports Server (NTRS)

Frick, Charles W; Mccullough, George B

1945-01-01

A method for calculating the rate of heat transfer from the surface of an airfoil or streamline body is presented. A comparison with the results of an experimental investigation indicates that the accuracy of the method is good. This method may be used to calculate the heat supply necessary for heat de-icing or in ascertaining the heat loss from the fuselage of an aircraft operating at great altitude. To illustrate the method, the total rate of heat transfer from an airfoil is calculated and compared with the experimental results.

Streamline similarity method for flow distributions and shock losses at the impeller inlet of the centrifugal pump

NASA Astrophysics Data System (ADS)

Zhang, Zh.

2018-02-01

An analytical method is presented, which enables the non-uniform velocity and pressure distributions at the impeller inlet of a pump to be accurately computed. The analyses are based on the potential flow theory and the geometrical similarity of the streamline distribution along the leading edge of the impeller blades. The method is thus called streamline similarity method (SSM). The obtained geometrical form of the flow distribution is then simply described by the geometrical variable G( s) and the first structural constant G I . As clearly demonstrated and also validated by experiments, both the flow velocity and the pressure distributions at the impeller inlet are usually highly non-uniform. This knowledge is indispensible for impeller blade designs to fulfill the shockless inlet flow condition. By introducing the second structural constant G II , the paper also presents the simple and accurate computation of the shock loss, which occurs at the impeller inlet. The introduction of two structural constants contributes immensely to the enhancement of the computational accuracies. As further indicated, all computations presented in this paper can also be well applied to the non-uniform exit flow out of an impeller of the Francis turbine for accurately computing the related mean values.

Streamlined Approach for Environmental Restoration Plan for Corrective Action Unit 489: WWII UXO Sites, Tonopah Test Range, Nevada; May 2005

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bechtel Nevada; U.S. Department of Energy, National Nuclear Security Administration Nevada Site Office

2005-05-01

This Streamlined Approach for Environmental Restoration Plan provides the details for the closure of Corrective Action Unit (CAU) 489: WWII UXO Sites, Tonopah Test Range. CAU 489 is located at the Tonopah Test Range and is currently listed in Appendix III of the Federal Facility Agreement and Consent Order of 1996.

Simulation of laminate composites degradation using mesoscopic non-local damage model and non-local layered shell element

NASA Astrophysics Data System (ADS)

Germain, Norbert; Besson, Jacques; Feyel, Frédéric

2007-07-01

Simulating damage and failure of laminate composites structures often fails when using the standard finite element procedure. The difficulties arise from an uncontrolled mesh dependence caused by damage localization and an increase in computational costs. One of the solutions to the first problem, widely used to predict the failure of metallic materials, consists of using non-local damage constitutive equations. The second difficulty can then be solved using specific finite element formulations, such as shell element, which decrease the number of degrees of freedom. The main contribution of this paper consists of extending these techniques to layered materials such as polymer matrix composites. An extension of the non-local implicit gradient formulation, accounting for anisotropy and stratification, and an original layered shell element, based on a new partition of the unity, are proposed. Finally the efficiency of the resulting numerical scheme is studied by comparing simulation with experimental results.

Mechanism-Based FE Simulation of Tool Wear in Diamond Drilling of SiCp/Al Composites.

PubMed

Xiang, Junfeng; Pang, Siqin; Xie, Lijing; Gao, Feinong; Hu, Xin; Yi, Jie; Hu, Fang

2018-02-07

The aim of this work is to analyze the micro mechanisms underlying the wear of macroscale tools during diamond machining of SiC p /Al6063 composites and to develop the mechanism-based diamond wear model in relation to the dominant wear behaviors. During drilling, high volume fraction SiC p /Al6063 composites containing Cu, the dominant wear mechanisms of diamond tool involve thermodynamically activated physicochemical wear due to diamond-graphite transformation catalyzed by Cu in air atmosphere and mechanically driven abrasive wear due to high-frequency scrape of hard SiC reinforcement on tool surface. An analytical diamond wear model, coupling Usui abrasive wear model and Arrhenius extended graphitization wear model was proposed and implemented through a user-defined subroutine for tool wear estimates. Tool wear estimate in diamond drilling of SiC p /Al6063 composites was achieved by incorporating the combined abrasive-chemical tool wear subroutine into the coupled thermomechanical FE model of 3D drilling. The developed drilling FE model for reproducing diamond tool wear was validated for feasibility and reliability by comparing numerically simulated tool wear morphology and experimentally observed results after drilling a hole using brazed polycrystalline diamond (PCD) and chemical vapor deposition (CVD) diamond coated tools. A fairly good agreement of experimental and simulated results in cutting forces, chip and tool wear morphologies demonstrates that the developed 3D drilling FE model, combined with a subroutine for diamond tool wear estimate can provide a more accurate analysis not only in cutting forces and chip shape but also in tool wear behavior during drilling SiC p /Al6063 composites. Once validated and calibrated, the developed diamond tool wear model in conjunction with other machining FE models can be easily extended to the investigation of tool wear evolution with various diamond tool geometries and other machining processes in cutting different

Mechanism-Based FE Simulation of Tool Wear in Diamond Drilling of SiCp/Al Composites

PubMed Central

Xiang, Junfeng; Pang, Siqin; Xie, Lijing; Gao, Feinong; Hu, Xin; Yi, Jie; Hu, Fang

2018-01-01

The aim of this work is to analyze the micro mechanisms underlying the wear of macroscale tools during diamond machining of SiCp/Al6063 composites and to develop the mechanism-based diamond wear model in relation to the dominant wear behaviors. During drilling, high volume fraction SiCp/Al6063 composites containing Cu, the dominant wear mechanisms of diamond tool involve thermodynamically activated physicochemical wear due to diamond-graphite transformation catalyzed by Cu in air atmosphere and mechanically driven abrasive wear due to high-frequency scrape of hard SiC reinforcement on tool surface. An analytical diamond wear model, coupling Usui abrasive wear model and Arrhenius extended graphitization wear model was proposed and implemented through a user-defined subroutine for tool wear estimates. Tool wear estimate in diamond drilling of SiCp/Al6063 composites was achieved by incorporating the combined abrasive-chemical tool wear subroutine into the coupled thermomechanical FE model of 3D drilling. The developed drilling FE model for reproducing diamond tool wear was validated for feasibility and reliability by comparing numerically simulated tool wear morphology and experimentally observed results after drilling a hole using brazed polycrystalline diamond (PCD) and chemical vapor deposition (CVD) diamond coated tools. A fairly good agreement of experimental and simulated results in cutting forces, chip and tool wear morphologies demonstrates that the developed 3D drilling FE model, combined with a subroutine for diamond tool wear estimate can provide a more accurate analysis not only in cutting forces and chip shape but also in tool wear behavior during drilling SiCp/Al6063 composites. Once validated and calibrated, the developed diamond tool wear model in conjunction with other machining FE models can be easily extended to the investigation of tool wear evolution with various diamond tool geometries and other machining processes in cutting different workpiece

Off-Design Performance of a Streamline-Traced, External-Compression Supersonic Inlet

NASA Technical Reports Server (NTRS)

Slater, John W.

2017-01-01

A computational study was performed to explore the aerodynamic performance of a streamline-traced, external-compression inlet designed for Mach 1.664 at off-design conditions of freestream Mach number, angle-of-attack, and angle-of-sideslip. Serious degradation of the inlet performance occurred for negative angles-of-attack and angles-of-sideslip greater than 3 degrees. At low subsonic speeds, the swept leading edges of the inlet created a pair of vortices that propagated to the engine face. Increasing the bluntness of the cowl lip showed no real improvement in the inlet performance at the low speeds, but did improve the inlet performance at the design conditions. Reducing the inlet flow rate improved the inlet performance, but at the likely expense of reduced thrust of the propulsion system. Deforming the cowl lip for low-speed operation of the inlet increased the inlet capture area and improved the inlet performance.

Can streamlined multi-criteria decision analysis be used to implement shared decision making for colorectal cancer screening?

PubMed Central

Dolan, James G.; Boohaker, Emily; Allison, Jeroan; Imperiale, Thomas F.

2013-01-01

Background Current US colorectal cancer screening guidelines that call for shared decision making regarding the choice among several recommended screening options are difficult to implement. Multi-criteria decision analysis (MCDA) is an established methodology well suited for supporting shared decision making. Our study goal was to determine if a streamlined form of MCDA using rank order based judgments can accurately assess patients’ colorectal cancer screening priorities. Methods We converted priorities for four decision criteria and three sub-criteria regarding colorectal cancer screening obtained from 484 average risk patients using the Analytic Hierarchy Process (AHP) in a prior study into rank order-based priorities using rank order centroids. We compared the two sets of priorities using Spearman rank correlation and non-parametric Bland-Altman limits of agreement analysis. We assessed the differential impact of using the rank order-based versus the AHP-based priorities on the results of a full MCDA comparing three currently recommended colorectal cancer screening strategies. Generalizability of the results was assessed using Monte Carlo simulation. Results Correlations between the two sets of priorities for the seven criteria ranged from 0.55 to 0.92. The proportions of absolute differences between rank order-based and AHP-based priorities that were more than ± 0.15 ranged from 1% to 16%. Differences in the full MCDA results were minimal and the relative rankings of the three screening options were identical more than 88% of the time. The Monte Carlo simulation results were similar. Conclusion Rank order-based MCDA could be a simple, practical way to guide individual decisions and assess population decision priorities regarding colorectal cancer screening strategies. Additional research is warranted to further explore the use of these methods for promoting shared decision making. PMID:24300851

A Damage Model for the Simulation of Delamination in Advanced Composites under Variable-Mode Loading

NASA Technical Reports Server (NTRS)

Turon, A.; Camanho, P. P.; Costa, J.; Davila, C. G.

2006-01-01

A thermodynamically consistent damage model is proposed for the simulation of progressive delamination in composite materials under variable-mode ratio. The model is formulated in the context of Damage Mechanics. A novel constitutive equation is developed to model the initiation and propagation of delamination. A delamination initiation criterion is proposed to assure that the formulation can account for changes in the loading mode in a thermodynamically consistent way. The formulation accounts for crack closure effects to avoid interfacial penetration of two adjacent layers after complete decohesion. The model is implemented in a finite element formulation, and the numerical predictions are compared with experimental results obtained in both composite test specimens and structural components.

FEAMAC/CARES Stochastic-Strength-Based Damage Simulation Tool for Ceramic Matrix Composites

NASA Technical Reports Server (NTRS)

Nemeth, Noel; Bednarcyk, Brett; Pineda, Evan; Arnold, Steven; Mital, Subodh; Murthy, Pappu; Bhatt, Ramakrishna

2016-01-01

Reported here is a coupling of two NASA developed codes: CARES (Ceramics Analysis and Reliability Evaluation of Structures) with the MAC/GMC (Micromechanics Analysis Code/ Generalized Method of Cells) composite material analysis code. The resulting code is called FEAMAC/CARES and is constructed as an Abaqus finite element analysis UMAT (user defined material). Here we describe the FEAMAC/CARES code and an example problem (taken from the open literature) of a laminated CMC in off-axis loading is shown. FEAMAC/CARES performs stochastic-strength-based damage simulation response of a CMC under multiaxial loading using elastic stiffness reduction of the failed elements.

Laboratory evaluation of airborne particulate control treatments for simulated aircraft crash recovery operations involving carbon fiber composite materials.

PubMed

Ferreri, Matthew; Slagley, Jeremy; Felker, Daniel

2015-01-01

This study compared four treatment protocols to reduce airborne composite fiber particulates during simulated aircraft crash recovery operations. Four different treatments were applied to determine effectiveness in reducing airborne composite fiber particulates as compared to a "no treatment" protocol. Both "gold standard" gravimetric methods and real-time instruments were used to describe mass per volume concentration, particle size distribution, and surface area. The treatment protocols were applying water, wetted water, wax, or aqueous film-forming foam (AFFF) to both burnt and intact tickets of aircraft composite skin panels. The tickets were then cut using a small high-speed rotary tool to simulate crash recovery operations. Aerosol test chamber. None. Airborne particulate control treatments. Measures included concentration units of milligrams per cubic meter of air, particle size distribution as described by both count median diameter and mass median diameter and geometric standard deviation of particles in micrometers, and surface area concentration in units of square micrometers per cubic centimeter. Finally, a Monte Carlo simulation was run on the particle size distribution results. Comparison was made via one-way analysis of variance. A significant difference (p < 0.0001) in idealized particle size distribution was found between the water and wetted water treatments as compared to the other treatments for burnt tickets. Emergency crash recovery operations should include a treatment of the debris with water or wetted water. The resulting increase in particle size will make respiratory protection more effective in protecting the response crews.

Laboratory evaluation of airborne particulate control treatments for simulated aircraft crash recovery operations involving carbon fiber composite materials.

PubMed

Ferreri, Matthew; Slagley, Jeremy; Felker, Daniel

2015-01-01

This study compared four treatment protocols to reduce airborne composite fiber particulates during simulated aircraft crash recovery operations. Four different treatments were applied to determine effectiveness in reducing airborne composite fiber particulates as compared to a "no treatment" protocol. Both "gold standard" gravimetric methods and real-time instruments were used to describe mass per volume concentration, particle size distribution, and surface area. The treatment protocols were applying water, wetted water, wax, or aqueous film-forming foam (AFFF) to both burnt and intact tickets of aircraft composite skin panels. The tickets were then cut using a small high-speed rotary tool to simulate crash recovery operations. Aerosol test chamber. None. Airborne particulate control treatments. Measures included concentration units of milligrams per cubic meter of air, particle size distribution as described by both count median diameter and mass median diameter and geometric standard deviation of particles in micrometers, and surface area concentration in units of square micrometers per cubic centimeter. Finally, a Monte Carlo simulation was run on the particle size distribution results. Comparison was made via one-way analysis of variance. A significant difference (p<0.0001) in idealized particle size distribution was found between the water and wetted water treatments as compared to the other treatments for burnt tickets. Emergency crash recovery operations should include a treatment of the debris with water or wetted water. The resulting increase in particle size will make respiratory protection more effective in protecting the response crews.

Effects of Simulated Functional Loading Conditions on Dentin, Composite, and Laminate Structures

PubMed Central

Walker, Mary P.; Teitelbaum, Heather K.; Eick, J. David; Williams, Karen B.

2008-01-01

Use of composite restorations continues to increase, tempered by more potential problems when placed in posterior dentition. Thus, it is essential to understand how these materials function under stress-bearing clinical conditions. Since mastication is difficult to replicate in the laboratory, cyclic loading is frequently used within in vitro evaluations but often employs traditional fatigue testing, which typically does not simulate occlusal loading because higher stresses and loading frequencies are used, so failure mechanisms may be different. The present investigation utilized relevant parameters (specimen size; loading frequency) to assess the effects of cyclic loading on flexural mechanical properties and fracture morphology of (coronal) dentin, composite, and dentin-adhesive-composite “laminate” structures. Incremental monitoring of flexural modulus on individual beams over 60,000 loading cycles revealed a gradual increase across materials; post-hoc comparisons indicated statistical significance only for 1 versus 60k cycles. Paired specimens were tested (one exposed to 60k loading cycles, one to static loading only), and comparisons of flexural modulus and strength showed statistically significantly higher values for cyclically-loaded specimens across materials, with no observable differences in fracture morphology. Localized reorganization of dentin collagen and polymer chains could have increased flexural modulus and strength during cyclic loading, which may have implications toward the life and failure mechanisms of clinical restorations and underlying tooth structure. PMID:18823019

Approaches to simulate impact damages on aeronautical composite structures

NASA Astrophysics Data System (ADS)

Sanga, R. P. Lemanle; Garnier, C.; Pantalé, O.

2018-02-01

Impact damage is one of the most critical aggressions for composite structures in aeronautical applications. Consequences of a high/low velocity and high/low energy impacts are very important to investigate. It is usually admitted that the most critical configuration is the Barely Visible Impact Damage (BVID), with impact energy of about 25 J, where some internal damages, invisible on the impacted surface of the specimen, drastically reduce the residual properties of the impacted material. In this work we highlight by the finite element simulation, the damage initiation and propagation process and the size of the defaults created by low velocity impact. Two approaches were developed: the first one is the layup technic and the second one is based on the cohesive element technic. Both technics show the plies damages by the Hashin's criteria. Moreover the second one gives the delamination damages with regards to the Benzeggah-Kenane criteria. The validation of these models is done by confrontation with some experimental results.

Comparison of ALE and SPH Simulations of Vertical Drop Tests of a Composite Fuselage Section into Water

NASA Technical Reports Server (NTRS)

Jackson, Karen E.; Fuchs, Yvonne T.

2008-01-01

Simulation of multi-terrain impact has been identified as an important research area for improved prediction of rotorcraft crashworthiness within the NASA Subsonic Rotary Wing Aeronautics Program on Rotorcraft Crashworthiness. As part of this effort, two vertical drop tests were conducted of a 5-ft-diameter composite fuselage section into water. For the first test, the fuselage section was impacted in a baseline configuration without energy absorbers. For the second test, the fuselage section was retrofitted with a composite honeycomb energy absorber. Both tests were conducted at a nominal velocity of 25-ft/s. A detailed finite element model was developed to represent each test article and water impact was simulated using both Arbitrary Lagrangian Eulerian (ALE) and Smooth Particle Hydrodynamics (SPH) approaches in LS-DYNA, a nonlinear, explicit transient dynamic finite element code. Analytical predictions were correlated with experimental data for both test configurations. In addition, studies were performed to evaluate the influence of mesh density on test-analysis correlation.

Simulation of mechanical behavior and optimization of simulated injection molding process for PLA based antibacterial composite and nanocomposite bone screws using central composite design.

PubMed

Heidari, Behzad Shiroud; Oliaei, Erfan; Shayesteh, Hadi; Davachi, Seyed Mohammad; Hejazi, Iman; Seyfi, Javad; Bahrami, Mozhgan; Rashedi, Hamid

2017-01-01

In this study, injection molding of three poly lactic acid (PLA) based bone screws was simulated and optimized through minimizing the shrinkage and warpage of the bone screws. The optimization was carried out by investigating the process factors such as coolant temperature, mold temperature, melt temperature, packing time, injection time, and packing pressure. A response surface methodology (RSM), based on the central composite design (CCD), was used to determine the effects of the process factors on the PLA based bone screws. Upon applying the method of maximizing the desirability function, optimization of the factors gave the lowest warpage and shrinkage for nanocomposite PLA bone screw (PLA9). Moreover, PLA9 has the greatest desirability among the selected materials for bone screw injection molding. Meanwhile, a finite element analysis (FE analysis) was also performed to determine the force values and concentration points which cause yielding of the screws under certain conditions. The Von-Mises stress distribution showed that PLA9 screw is more resistant against the highest loads as compared to the other ones. Finally, according to the results of injection molding simulations, the design of experiments (DOE) and structural analysis, PLA9 screw is recommended as the best candidate for the production of biomedical materials among all the three types of screws. Copyright © 2016 Elsevier Ltd. All rights reserved.

Streamlining Collaboration for the Gravitational-wave Astronomy Community

NASA Astrophysics Data System (ADS)

Koranda, S.

2016-12-01

In the morning hours of September 14, 2015 the LaserInterferometer Gravitational-wave Observatory (LIGO) directlydetected gravitational waves from inspiraling and coalescingblack holes, confirming a major prediction of AlbertEinstein's general theory of relativity and beginning the eraof gravitational-wave astronomy. With the LIGO detectors in the United States, the Virgo andGEO detectors in Europe, and the KAGRA detector in Japan thegravitational-wave astrononmy community is opening a newwindow on our Universe. Realizing the full science potentialof LIGO and the other interferometers requires globalcollaboration not only within the gravitational-wave astronomycommunity but also with the astronomers and astrophysicists acrossmultipe disciplines working to realize and leverage the powerof multi-messenger astronomy. Enabling thousands of researchers from around the world andacross multiple projects to efficiently collaborate, share,and analyze data and provide streamlined access to services,computing, and tools requires new and scalable approaches toidentity and access management (IAM). We will discuss LIGO'sIAM journey that began in 2007 and how today LIGO leveragesinternal identity federations like InCommon and eduGAIN toprovide scalable and managed access for the gravitational-waveastronomy community. We will discuss the steps both largeand small research organizations and projects take as theirIAM infrastructure matures from ad-hoc silos of independent services to fully integrated and federated services thatstreamline collaboration so that scientists can focus onresearch and not managing passwords.

Color Stability of Composites After Short-term Oral Simulation: An in vitro Study

PubMed Central

Özdaş, Didem Öner; Kazak, Mağrur; Çilingir, Aylin; Subaşı, Meryem Gülce; Tiryaki, Murat; Günal, Şölen

2016-01-01

Background: Although most of the studies investigated color stability of different restorative materials, evaluation of color stability of composites after immersion in multiple beverages in the same day by an in vitro oral simulation study is unclear. Objective: To assess color change of different restorative materials at the end of days 1, 14, and 30 of immersion in multiple liquid types to mimic the oral environment in vitro. Method: Ten disc-shaped specimens were made from each of four different resin composites (Filtek Z250, Voco x-tra base, Beautifil Flow Plus, Beautifil II). Baseline color value of each sample was measured using a spectrophotometer. Each composite was respectively immersed in coffee, an orange/pomegranate juice mixture, black tea, and a mouth rinse on the same day to mimic daily liquid consumption of individuals. Color measurements were taken after 1, 14, and 30 days by spectrophotometer and color change values were calculated. Statistical analyses were executed by one-way ANOVA/Tukey HSD and repeated-measures ANOVA. Results: All materials showed significant color change after 1, 14, and 30 days (P < 0.01) of immersion in liquids, with the lowest color alteration observed at the 1st day and the highest observed after the 30th day. Among the materials tested, at each time point (1, 14, and 30 days), the lowest color alteration was detected in Filtek Z250 and the highest color alteration was detected in Beautifil II. Conclusion: Color alteration of composite resins is affected by composite type and storage time. With the exception of 1 day of storage, color changes of all materials were substantial and clinically unacceptable. PMID:27733871

Numerical simulation and experimental validation of Lamb wave propagation behavior in composite plates

NASA Astrophysics Data System (ADS)

Kim, Sungwon; Uprety, Bibhisha; Mathews, V. John; Adams, Daniel O.

2015-03-01

Structural Health Monitoring (SHM) based on Acoustic Emission (AE) is dependent on both the sensors to detect an impact event as well as an algorithm to determine the impact location. The propagation of Lamb waves produced by an impact event in thin composite structures is affected by several unique aspects including material anisotropy, ply orientations, and geometric discontinuities within the structure. The development of accurate numerical models of Lamb wave propagation has important benefits towards the development of AE-based SHM systems for impact location estimation. Currently, many impact location algorithms utilize the time of arrival or velocities of Lamb waves. Therefore the numerical prediction of characteristic wave velocities is of great interest. Additionally, the propagation of the initial symmetric (S0) and asymmetric (A0) wave modes is important, as these wave modes are used for time of arrival estimation. In this investigation, finite element analyses were performed to investigate aspects of Lamb wave propagation in composite plates with active signal excitation. A comparative evaluation of two three-dimensional modeling approaches was performed, with emphasis placed on the propagation and velocity of both the S0 and A0 wave modes. Results from numerical simulations are compared to experimental results obtained from active AE testing. Of particular interest is the directional dependence of Lamb waves in quasi-isotropic carbon/epoxy composite plates. Numerical and experimental results suggest that although a quasi-isotropic composite plate may have the same effective elastic modulus in all in-plane directions, the Lamb wave velocity may have some directional dependence. Further numerical analyses were performed to investigate Lamb wave propagation associated with circular cutouts in composite plates.

Computational Simulation of Damage Progression of Composite Thin Shells Subjected to Mechanical Loads

NASA Technical Reports Server (NTRS)

Gotsis, P. K.; Chamis, C. C.; Minnetyan, L.

1996-01-01

Defect-free and defected composite thin shells with ply orientation (90/0/+/-75) made of graphite/epoxy are simulated for damage progression and fracture due to internal pressure and axial loading. The thin shells have a cylindrical geometry with one end fixed and the other free. The applied load consists of an internal pressure in conjunction with an axial load at the free end, the cure temperature was 177 C (350 F) and the operational temperature was 21 C (70 F). The residual stresses due to the processing are taken into account. Shells with defect and without defects were examined by using CODSTRAN an integrated computer code that couples composite mechanics, finite element and account for all possible failure modes inherent in composites. CODSTRAN traces damage initiation, growth, accumulation, damage propagation and the final fracture of the structure. The results show that damage initiation started with matrix failure while damage/fracture progression occurred due to additional matrix failure and fiber fracture. The burst pressure of the (90/0/+/- 75) defected shell was 0.092% of that of the free defect. Finally the results of the damage progression of the (90/0/+/- 75), defective composite shell was compared with the (90/0/+/- theta, where theta = 45 and 60, layup configurations. It was shown that the examined laminate (90/0/+/- 75) has the least damage tolerant of the two compared defective shells with the (90/0/+/- theta), theta = 45 and 60 laminates.

78 FR 25137 - Radio Experimentation and Market Trials-Streamlining Rules

Federal Register 2010, 2011, 2012, 2013, 2014

2013-04-29

...This document revises and streamlines the Commission rules to modernize the Experimental Radio Service (ERS). The rules adopted in the Report and Order updates the ERS to a more flexible framework to keep pace with the speed of modern technological change while continuing to provide an environment where creativity can thrive. To accomplish this transition, the Commission created three new types of ERS licenses--the program license, the medical testing license, and the compliance testing license--to benefit the development of new technologies, expedite their introduction to the marketplace, and unleash the full power of innovators to keep the United States at the forefront of the communications industry. The Commission's actions also modify the market trial rules to eliminate confusion and more clearly articulate its policies with respect to marketing products prior to equipment certification. The Commission believes that these actions will remove regulatory barriers to experimentation, thereby permitting institutions to move from concept to experimentation to finished product more rapidly and to more quickly implement creative problem- solving methodologies.

The Single Habitat Module Concept a Streamlined Way to Explore

NASA Technical Reports Server (NTRS)

Chambliss, Joe

2012-01-01

Many concepts have been proposed for exploring space. In early 2010 presidential direction called for reconsidering the approach to address changes in exploration destinations, use of new technologies and development of new capabilities to support exploration of space. Considering the proposed new technologies and capabilities that NASA was directed to pursue, the Single Habitathabitat module (SHMSHM) concept for a more streamlined approach to the infrastructure and conduct of exploration missions was developed. The SHM concept combines many of the new promising technologies with a central concept of mission architectures that uses a single habitat module for all phases of an exploration mission. Integrating mission elements near Earth and fully fueling them prior to departure of the vicinity of Earth provides the capability of using the single habitat both in transit to an exploration destination and while exploring the destination. The concept employs the capability to return the habitat and interplanetary propulsion system to Earth vicinity so that those elements can be reused on subsequent exploration missions. This paper describes the SHM concept, and the advantages it provides to accomplish exploration objectives.

The Single Crew Module Concept a Streamlined Way to Explore

NASA Technical Reports Server (NTRS)

Chambliss, Joe

2012-01-01

Many concepts have been proposed for exploring space. In early 2010 presidential direction called for reconsidering the approach to address changes in exploration destinations, use of new technologies and development of new capabilities to support exploration of space. Considering the proposed new technology and capabilities that NASA was directed to pursue, the single crew module (SCM) concept for a more streamlined approach to the infrastructure and conduct of exploration missions was developed. The SCM concept combines many of the new promising technologies with a central concept of mission architectures that uses a single habitat module for all phases of an exploration mission. Integrating mission elements near Earth and fully fueling them prior to departure of the vicinity of Earth provides the capability of using the single habitat both in transit to an exploration destination and while exploring the destination. The concept employs the capability to return the habitat and interplanetary propulsion system to Earth vicinity so that those elements can be reused on subsequent exploration missions. This paper describes the SCM concept, and the advantages it provides to accomplish exploration objectives.

A probabilistic approach to composite micromechanics

NASA Technical Reports Server (NTRS)

Stock, T. A.; Bellini, P. X.; Murthy, P. L. N.; Chamis, C. C.

1988-01-01

Probabilistic composite micromechanics methods are developed that simulate expected uncertainties in unidirectional fiber composite properties. These methods are in the form of computational procedures using Monte Carlo simulation. A graphite/epoxy unidirectional composite (ply) is studied to demonstrate fiber composite material properties at the micro level. Regression results are presented to show the relative correlation between predicted and response variables in the study.

Probabilistic Composite Design

NASA Technical Reports Server (NTRS)

Chamis, Christos C.

1997-01-01

Probabilistic composite design is described in terms of a computational simulation. This simulation tracks probabilistically the composite design evolution from constituent materials, fabrication process, through composite mechanics and structural components. Comparisons with experimental data are provided to illustrate selection of probabilistic design allowables, test methods/specimen guidelines, and identification of in situ versus pristine strength, For example, results show that: in situ fiber tensile strength is 90% of its pristine strength; flat-wise long-tapered specimens are most suitable for setting ply tensile strength allowables: a composite radome can be designed with a reliability of 0.999999; and laminate fatigue exhibits wide-spread scatter at 90% cyclic-stress to static-strength ratios.

Three-dimensional smoothed particle hydrodynamics simulation for injection molding flow of short fiber-reinforced polymer composites

NASA Astrophysics Data System (ADS)

He, Liping; Lu, Gang; Chen, Dachuan; Li, Wenjun; Lu, Chunsheng

2017-07-01

This paper investigates the three-dimensional (3D) injection molding flow of short fiber-reinforced polymer composites using a smoothed particle hydrodynamics (SPH) simulation method. The polymer melt was modeled as a power law fluid and the fibers were considered as rigid cylindrical bodies. The filling details and fiber orientation in the injection-molding process were studied. The results indicated that the SPH method could effectively predict the order of filling, fiber accumulation, and heterogeneous distribution of fibers. The SPH simulation also showed that fibers were mainly aligned to the flow direction in the skin layer and inclined to the flow direction in the core layer. Additionally, the fiber-orientation state in the simulation was quantitatively analyzed and found to be consistent with the results calculated by conventional tensor methods.

Impact analysis of composite aircraft structures

NASA Technical Reports Server (NTRS)

Pifko, Allan B.; Kushner, Alan S.

1993-01-01

The impact analysis of composite aircraft structures is discussed. Topics discussed include: background remarks on aircraft crashworthiness; comments on modeling strategies for crashworthiness simulation; initial study of simulation of progressive failure of an aircraft component constructed of composite material; and research direction in composite characterization for impact analysis.

Volume I. Percussion Sextet. (original Composition). Volume II. The Simulation of Acoustical Space by Means of Physical Modeling.

NASA Astrophysics Data System (ADS)

Manzara, Leonard Charles

1990-01-01

The dissertation is in two parts:. 1. Percussion Sextet. The Percussion Sextet is a one movement musical composition with a length of approximately fifteen minutes. It is for six instrumentalists, each on a number of percussion instruments. The overriding formal problem was to construct a coherent and compelling structure which fuses a diversity of musical materials and textures into a dramatic whole. Particularly important is the synthesis of opposing tendencies contained in stochastic and deterministic processes: global textures versus motivic detail, and randomness versus total control. Several compositional techniques are employed in the composition. These methods of composition will be aided, in part, by the use of artificial intelligence techniques programmed on a computer. Finally, the percussion ensemble is the ideal medium to realize the above processes since it encompasses a wide range of both pitched and unpitched timbres, and since a great variety of textures and densities can be created with a certain economy of means. 2. The simulation of acoustical space by means of physical modeling. This is a written report describing the research and development of a computer program which simulates the characteristics of acoustical space in two dimensions. With the computer program the user can simulate most conventional acoustical spaces, as well as those physically impossible to realize in the real world. The program simulates acoustical space by means of geometric modeling. This involves defining wall equations, phantom source points and wall diffusions, and then processing input files containing digital signals through the program, producing output files ready for digital to analog conversion. The user of the program is able to define wall locations and wall reflectivity and roughness characteristics, all of which can be changed over time. Sound source locations are also definable within the acoustical space and these locations can be changed independently at

Probabilistic Fiber Composite Micromechanics

NASA Technical Reports Server (NTRS)

Stock, Thomas A.

1996-01-01

Probabilistic composite micromechanics methods are developed that simulate expected uncertainties in unidirectional fiber composite properties. These methods are in the form of computational procedures using Monte Carlo simulation. The variables in which uncertainties are accounted for include constituent and void volume ratios, constituent elastic properties and strengths, and fiber misalignment. A graphite/epoxy unidirectional composite (ply) is studied to demonstrate fiber composite material property variations induced by random changes expected at the material micro level. Regression results are presented to show the relative correlation between predictor and response variables in the study. These computational procedures make possible a formal description of anticipated random processes at the intra-ply level, and the related effects of these on composite properties.

Molecular Simulation of Ionic Polyimides and Composites with Ionic Liquids as Gas-Separation Membranes.

PubMed

Abedini, Asghar; Crabtree, Ellis; Bara, Jason E; Turner, C Heath

2017-10-24

Polyimides are at the forefront of advanced membrane materials for CO 2 capture and gas-purification processes. Recently, ionic polyimides (i-PIs) have been reported as a new class of condensation polymers that combine structural components of both ionic liquids (ILs) and polyimides through covalent linkages. In this study, we report CO 2 and CH 4 adsorption and structural analyses of an i-PI and an i-PI + IL composite containing [C 4 mim][Tf 2 N]. The combination of molecular dynamics (MD) and grand canonical Monte Carlo (GCMC) simulations is used to compute the gas solubility and the adsorption performance with respect to the density, fractional free volume (FFV), and surface area of the materials. Our results highlight the polymer relaxation process and its correlation to the gas solubility. In particular, the surface area can provide meaningful guidance with respect to the gas solubility, and it tends to be a more sensitive indicator of the adsorption behavior versus only considering the system density and FFV. For instance, as the polymer continues to relax, the density, FFV, and pore-size distribution remain constant while the surface area can continue to increase, enabling more adsorption. Structural analyses are also conducted to identify the nature of the gas adsorption once the ionic liquid is added to the polymer. The presence of the IL significantly displaces the CO 2 molecules from the ligand nitrogen sites in the neat i-PI to the imidazolium rings in the i-PI + IL composite. However, the CH 4 molecules move from the imidazolium ring sites in the neat i-PI to the ligand nitrogen atoms in the i-PI + IL composite. These molecular details can provide critical information for the experimental design of highly selective i-PI materials as well as provide additional guidance for the interpretation of the simulated adsorption systems.

A streamlined sustainability assessment tool for improved decision making in the urban water industry.

PubMed

Schulz, Matthias; Short, Michael D; Peters, Gregory M

2012-01-01

Water supply is a key consideration in sustainable urban planning. Ideally, detailed quantitative sustainability assessments are undertaken during the planning stage to inform the decision-making process. In reality, however, the significant time and cost associated with undertaking such detailed environmental and economic assessments is often cited as a barrier to wider implementation of these key decision support tools, particularly for decisions made at the local or regional government level. In an attempt to overcome this barrier of complexity, 4 water service providers in Melbourne, Australia, funded the development of a publicly available streamlined Environmental Sustainability Assessment Tool, which is aimed at a wide range of decision makers to assist them in broadening the type and number of water servicing options that can be considered for greenfield or backlog developments. The Environmental Sustainability Assessment Tool consists of a simple user interface and draws on life cycle inventory data to allow for rapid estimation of the environmental and economic performance of different water servicing scenarios. Scenario options can then be further prioritized by means of an interactive multicriteria analysis. The intent of this article is to identify the key issues to be considered in a streamlined sustainability assessment tool for the urban water industry, and to demonstrate the feasibility of generating accurate life cycle assessments and life cycle costings, using such a tool. We use a real-life case study example consisting of 3 separate scenarios for a planned urban development to show that this kind of tool can emulate life cycle assessments and life cycle costings outcomes obtained through more detailed studies. This simplified approach is aimed at supporting "sustainability thinking" early in the decision-making process, thereby encouraging more sustainable water and sewerage infrastructure solutions. Copyright © 2011 SETAC.

Comparative Evaluation of Flow Quantification across the Atrioventricular Valve in Patients with Functional Univentricular Heart after Fontan's Surgery and Healthy Controls: Measurement by 4D Flow Magnetic Resonance Imaging and Streamline Visualization.

PubMed

She, Hoi Lam; Roest, Arno A W; Calkoen, Emmeline E; van den Boogaard, Pieter J; van der Geest, Rob J; Hazekamp, Mark G; de Roos, Albert; Westenberg, Jos J M

2017-01-01

To evaluate the inflow pattern and flow quantification in patients with functional univentricular heart after Fontan's operation using 4D flow magnetic resonance imaging (MRI) with streamline visualization when compared with the conventional 2D flow approach. Seven patients with functional univentricular heart after Fontan's operation and twenty-three healthy controls underwent 4D flow MRI. In two orthogonal two-chamber planes, streamline visualization was applied, and inflow angles with peak inflow velocity (PIV) were measured. Transatrioventricular flow quantification was assessed using conventional 2D multiplanar reformation (MPR) and 4D MPR tracking the annulus and perpendicular to the streamline inflow at PIV, and they were validated with net forward aortic flow. Inflow angles at PIV in the patient group demonstrated wide variation of angles and directions when compared with the control group (P < .01). The use of 4D flow MRI with streamlines visualization in quantification of the transatrioventricular flow had smaller limits of agreement (2.2 ± 4.1 mL; 95% limit of agreement -5.9-10.3 mL) when compared with the static plane assessment from 2DFlow MRI (-2.2 ± 18.5 mL; 95% limit of agreement agreement -38.5-34.1 mL). Stronger correlation was present in the 4D flow between the aortic and trans-atrioventricular flow (R 2 correlation in 4D flow: 0.893; in 2D flow: 0.786). Streamline visualization in 4D flow MRI confirmed variable atrioventricular inflow directions in patients with functional univentricular heart with previous Fontan's procedure. 4D flow aided generation of measurement planes according to the blood flood dynamics and has proven to be more accurate than the fixed plane 2D flow measurements when calculating flow quantifications. © 2016 Wiley Periodicals, Inc.

Impact Testing and Simulation of a Crashworthy Composite Fuselage Section with Energy-Absorbing Seats and Dummies

NASA Technical Reports Server (NTRS)

Fasanella, Edwin L.; Jackson, Karen E.

2002-01-01

A 25-ft/s vertical drop test of a composite fuselage section was conducted with two energy-absorbing seats occupied by anthropomorphic dummies to evaluate the crashworthy features of the fuselage section and to determine its interaction with the seats and dummies. The 5-ft. diameter fuselage section consists of a stiff structural floor and an energy-absorbing subfloor constructed of Rohacel foam blocks. The experimental data from this test were analyzed and correlated with predictions from a crash simulation developed using the nonlinear, explicit transient dynamic computer code, MSC.Dytran. The anthropomorphic dummies were simulated using the Articulated Total Body (ATB) code, which is integrated into MSC.Dytran.

Impact Testing and Simulation of a Crashworthy Composite Fuselage Section with Energy-Absorbing Seats and Dummies

NASA Technical Reports Server (NTRS)

Fasanella, Edwin L.; Jackson, Karen E.

2002-01-01

A 25-ft/s vertical drop test of a composite fuselage section was conducted with two energy-absorbing seats occupied by anthropomorphic dummies to evaluate the crashworthy features of the fuselage section and to determine its interaction with the seats and dummies. The 5-ft diameter fuselage section consists of a stiff structural floor and an energy-absorbing subfloor constructed of Rohacel foam blocks. The experimental data from this test were analyzed and correlated with predictions from a crash simulation developed using the nonlinear, explicit transient dynamic computer code, MSC.Dytran. The anthropomorphic dummies were simulated using the Articulated Total Body (ATB) code, which is integrated into MSC.Dytran.

Compostability and biodegradation study of PLA-wheat straw and PLA-soy straw based green composites in simulated composting bioreactor.

PubMed

Pradhan, Ranjan; Misra, Manjusri; Erickson, Larry; Mohanty, Amar

2010-11-01

A laboratory scale simulated composting facility (as per ASTM D 5338) was designed and utilized to determine and evaluate the extent of degradation of polylactic acid (PLA), untreated wheat and soy straw and injection moulded composites of PLA-wheat straw (70:30) and PLA-soy straw (70:30). The outcomes of the study revealed the suitability of the test protocol, validity of the test system and defined the compostability of the composites of PLA with unmodified natural substrate. The study would help to design composites using modified soy straw and wheat straw as reinforcement/filler to satisfy ASTM D 6400 specifications. Copyright 2010 Elsevier Ltd. All rights reserved.

Streamlining Metadata and Data Management for Evolving Digital Libraries

NASA Astrophysics Data System (ADS)

Clark, D.; Miller, S. P.; Peckman, U.; Smith, J.; Aerni, S.; Helly, J.; Sutton, D.; Chase, A.

2003-12-01

What began two years ago as an effort to stabilize the Scripps Institution of Oceanography (SIO) data archives from more than 700 cruises going back 50 years, has now become the operational fully-searchable "SIOExplorer" digital library, complete with thousands of historic photographs, images, maps, full text documents, binary data files, and 3D visualization experiences, totaling nearly 2 terabytes of digital content. Coping with data diversity and complexity has proven to be more challenging than dealing with large volumes of digital data. SIOExplorer has been built with scalability in mind, so that the addition of new data types and entire new collections may be accomplished with ease. It is a federated system, currently interoperating with three independent data-publishing authorities, each responsible for their own quality control, metadata specifications, and content selection. The IT architecture implemented at the San Diego Supercomputer Center (SDSC) streamlines the integration of additional projects in other disciplines with a suite of metadata management and collection building tools for "arbitrary digital objects." Metadata are automatically harvested from data files into domain-specific metadata blocks, and mapped into various specification standards as needed. Metadata can be browsed and objects can be viewed onscreen or downloaded for further analysis, with automatic proprietary-hold request management.

On Complexities of Impact Simulation of Fiber Reinforced Polymer Composites: A Simplified Modeling Framework

PubMed Central

Alemi-Ardakani, M.; Milani, A. S.; Yannacopoulos, S.

2014-01-01

Impact modeling of fiber reinforced polymer composites is a complex and challenging task, in particular for practitioners with less experience in advanced coding and user-defined subroutines. Different numerical algorithms have been developed over the past decades for impact modeling of composites, yet a considerable gap often exists between predicted and experimental observations. In this paper, after a review of reported sources of complexities in impact modeling of fiber reinforced polymer composites, two simplified approaches are presented for fast simulation of out-of-plane impact response of these materials considering four main effects: (a) strain rate dependency of the mechanical properties, (b) difference between tensile and flexural bending responses, (c) delamination, and (d) the geometry of fixture (clamping conditions). In the first approach, it is shown that by applying correction factors to the quasistatic material properties, which are often readily available from material datasheets, the role of these four sources in modeling impact response of a given composite may be accounted for. As a result a rough estimation of the dynamic force response of the composite can be attained. To show the application of the approach, a twill woven polypropylene/glass reinforced thermoplastic composite laminate has been tested under 200 J impact energy and was modeled in Abaqus/Explicit via the built-in Hashin damage criteria. X-ray microtomography was used to investigate the presence of delamination inside the impacted sample. Finally, as a second and much simpler modeling approach it is shown that applying only a single correction factor over all material properties at once can still yield a reasonable prediction. Both advantages and limitations of the simplified modeling framework are addressed in the performed case study. PMID:25431787

Computer simulation of refining process of a high consistency disc refiner based on CFD

NASA Astrophysics Data System (ADS)

Wang, Ping; Yang, Jianwei; Wang, Jiahui

2017-08-01

In order to reduce refining energy consumption, the ANSYS CFX was used to simulate the refining process of a high consistency disc refiner. In the first it was assumed to be uniform Newton fluid of turbulent state in disc refiner with the k-ɛ flow model; then meshed grids and set the boundary conditions in 3-D model of the disc refiner; and then was simulated and analyzed; finally, the viscosity of the pulp were measured. The results show that the CFD method can be used to analyze the pressure and torque on the disc plate, so as to calculate the refining power, and streamlines and velocity vectors can also be observed. CFD simulation can optimize parameters of the bar and groove, which is of great significance to reduce the experimental cost and cycle.

Numerical simulating and experimental study on the woven carbon fiber-reinforced composite laminates under low-velocity impact

NASA Astrophysics Data System (ADS)

Liu, Hanyang; Tang, Zhanwen; Pan, Lingying; Zhao, Weidong; Sun, Baogang; Jiang, Wenge

2016-05-01

Impact damage has been identified as a critical form of the defects that constantly threatened the reliability of composite structures, such as those used in the aerospace structures and systems. Low energy impacts can introduce barely visible damage and cause the degradation of structural stiffness, furthermore, the flaws caused by low-velocity impact are so dangerous that they can give rise to the further extended delaminations. In order to improve the reliability and load carrying capacity of composite laminates under low-velocity impact, in this paper, the numerical simulatings and experimental studies on the woven fiber-reinforced composite laminates under low-velocity impact with impact energy 16.7J were discussed. The low velocity impact experiment was carried out through drop-weight system as the reason of inertia effect. A numerical progressive damage model was provided, in which the damages of fiber, matrix and interlamina were considered by VUMT subroutine in ABAQUS, to determine the damage modes. The Hashin failure criteria were improved to cover the failure modes of fiber failure in the directions of warp/weft and delaminations. The results of Finite Element Analysis (FEA) were compared with the experimental results of nondestructive examination including the results of ultrasonic C-scan, cross-section stereomicroscope and contact force - time history curves. It is found that the response of laminates under low-velocity impact could be divided into stages with different damage. Before the max-deformation of the laminates occurring, the matrix cracking, fiber breakage and delaminations were simulated during the impactor dropping. During the releasing and rebounding period, matrix cracking and delaminations areas kept increasing in the laminates because of the stress releasing of laminates. Finally, the simulating results showed the good agreements with the results of experiment.

Assessment of zero-equation SGS models for simulating indoor environment

NASA Astrophysics Data System (ADS)

Taghinia, Javad; Rahman, Md Mizanur; Tse, Tim K. T.

2016-12-01

The understanding of air-flow in enclosed spaces plays a key role to designing ventilation systems and indoor environment. The computational fluid dynamics aspects dictate that the large eddy simulation (LES) offers a subtle means to analyze complex flows with recirculation and streamline curvature effects, providing more robust and accurate details than those of Reynolds-averaged Navier-Stokes simulations. This work assesses the performance of two zero-equation sub-grid scale models: the Rahman-Agarwal-Siikonen-Taghinia (RAST) model with a single grid-filter and the dynamic Smagorinsky model with grid-filter and test-filter scales. This in turn allows a cross-comparison of the effect of two different LES methods in simulating indoor air-flows with forced and mixed (natural + forced) convection. A better performance against experiments is indicated with the RAST model in wall-bounded non-equilibrium indoor air-flows; this is due to its sensitivity toward both the shear and vorticity parameters.

Simulation and fabrication of 0-3 composite PZT films for ultrahigh frequency (100-300 MHz) ultrasonic transducers

NASA Astrophysics Data System (ADS)

Chen, Xiaoyang; Fei, Chunlong; Chen, Zeyu; Chen, Ruimin; Yu, Ping; Chen, Zhongping; Shung, K. Kirk; Zhou, Qifa

2016-03-01

This paper presents simulation, fabrication, and characterization of single-element ultrahigh frequency (100-300-MHz) needle ultrasonic transducers based on 0-3 composite Pb(Zr0.52Ti0.48)O3 (PZT) films prepared by using composite ceramic sol-gel film and sol-infiltration technique. The center frequency of the developed transducer at 300-MHz was the highest frequency of PbTiO3 ceramic-based ultrasonic transducers ever reported. Furthermore, a brief description of the composite model was followed by the development of a new expression for predicting the longitudinal velocity, the clamped dielectric constant, and the complex electromechanical coupling coefficient kt of these films, which is very important in ultrasonic transducer design. Moreover, these parameters are difficult to obtain by measuring the frequency dependence of impedance and phase angle because of the weak signal of the previous 0-3 composite films transducer (>100 MHz). The modeling results show that the Cubes model with a geometric factor n = 0.05 fits well with the measured data. This model will be helpful for developing the 0-3 composite systems for ultrahigh frequency ultrasonic transducer design.

Two-dimensional global hybrid simulation of pressure evolution and waves in the magnetosheath

NASA Astrophysics Data System (ADS)

Lin, Y.; Denton, R. E.; Lee, L. C.; Chao, J. K.

2001-06-01

A two-dimensional hybrid simulation is carried out for the global structure of the magnetosheath. Quasi-perpendicular magnetosonic/fast mode waves with large-amplitude in-phase oscillations of the magnetic field and the ion density are seen near the bow shock transition. Alfvén/ion-cyclotron waves are observed along the streamlines in the magnetosheath, and the wave power peaks in the middle magnetosheath. Antiphase oscillations in the magnetic field and density are present away from the shock transition. Transport ratio analysis suggests that these oscillations result from mirror mode waves. Since fluid simulations are currently best able to model the global magnetosphere and the pressure in the magnetosphere is inherently anisotropic (parallel pressure p∥≠perpendicular pressure p⊥), it is of some interest to see if a fluid model can be used to predict the anisotropic pressure evolution of a plasma. Here the predictions of double adiabatic theory, the bounded anisotropy model, and the double polytropic model are tested using the two-dimensional hybrid simulation of the magnetosheath. Inputs to the models from the hybrid simulation are the initial post bow shock pressures and the time-dependent density and magnetic field strength along streamlines of the plasma. The success of the models is evaluated on the basis of how well they predict the subsequent evolution of p∥ and p⊥. The bounded anisotropy model, which encorporates a bound on p⊥/p∥ due to the effect of ion cyclotron pitch angle scattering, does a very good job of predicting the evolution of p⊥ this is evidence that local transfer of energy due to waves is occurring. Further evidence is the positive identification of ion-cyclotron waves in the simulation. The lack of such a good prediction for the evolution of p∥ appears to be due to the model's lack of time dependence for the wave-particle interaction and its neglect of the parallel heat flux. Estimates indicate that these effects will

Ultrasonic characterization of damage in a simulated CF-18 composite structure

NASA Astrophysics Data System (ADS)

McRae, K. I.; Finlayson, R. D.; Sturrock, W. R.; Liesch, D. S.

1993-02-01

A simulated CF-18 aircraft door component was constructed and subjected to treatment during manufacturing with the object of inducing damage in the composite material in a known and well-defined manner. The simulated component was then sent to participants in a nondestructive evaluation study. Results are reported for tests conducted with a scanning apparatus and data acquisition system which consisted of three components: ultrasonic transducer and scanner comprising a two-axis scanning frame to which a modified commercial transducer was attached; an acquisition system for ultrasonic data known as Signal Processing Ultrasonic Device (SPUD); and a data analysis and display system (DETECT/NDE) specifically designed to manipulate large three dimensional ultrasonic data sets. A series of five large-area scans was performed, each scan about 52 cm square. A total of eight regions of interest were identified for a more detailed analysis of the delamination damage, seven detailed scans covering a 13-cm square and one covering a 20.8-cm square. It was often possible to identify the probable source of the damage as that resulting from impact or caused by overloading of fasteners. Flaws of all significant dimensions were located and fully characterized using the ultrasonic procedure.

Lightning Strike Ablation Damage Influence Factors Analysis of Carbon Fiber/Epoxy Composite Based on Coupled Electrical-Thermal Simulation

NASA Astrophysics Data System (ADS)

Yin, J. J.; Chang, F.; Li, S. L.; Yao, X. L.; Sun, J. R.; Xiao, Y.

2017-10-01

According to the mathematical analysis model constructed on the basis of energy-balance relationship in lightning strike, and accompany with the simplified calculation strategy of composite resin pyrolysis degree dependent electrical conductivity, an effective three dimensional thermal-electrical coupling analysis finite element model of composite laminate suffered from lightning current was established based on ABAQUS, to elucidate the effects of lighting current waveform parameters and thermal/electrical properties of composite laminate on the extent of ablation damage. Simulated predictions agree well with the composite lightning strike directed effect experimental data, illustrating the potential accuracy of the constructed model. The analytical results revealed that extent of composite lightning strike ablation damage can be characterized by action integral validly, there exist remarkable power function relationships between action integral and visual damage area, projected damage area, maximum damage depth and damage volume of ablation damage, and enhancing the electrical conductivity and specific heat of composite, ablation damage will be descended obviously, power function relationships also exist between electrical conductivity, specific heat and ablation damage, however, the impact of thermal conductivity on the extent of ablation damage is not notable. The conclusions obtained provide some guidance for composite anti-lightning strike structure-function integration design.

Evaluation of chitosan-hydroxyapatite-collagen composite strength as scaffold material by immersion in simulated body fluid

NASA Astrophysics Data System (ADS)

Sari, N. K.; Indrani, D. J.; Johan, C.; Corputty, J. E. M.

2017-08-01

The reconstruction of bone tissue defects is a major challenge facing oral and maxillofacial surgeons. The essential elements needed for tissue engineering are cells, scaffolds (matrix), and stimulant molecules (growth factors). The mechanical properties of chitosan-hydroxyapatite-collagen scaffolds produced by BATAN, Jakarta, have not yet been studied. This study therefore analyzed the mechanical properties of chitosan-hydroxyapatite-collagen composite scaffolds prepared by BATAN, Jakarta, before and after immersion in simulated body fluid (SBF) for eight days. The compressive and tensile strengths of the chitosan-hydroxyapatite-collagen composite scaffolds were analyzed after immersion in SBF at 37°C for eight days. Each scaffold was removed and dried at room temperature on days 0, 2, 4, 6, and 8. The data obtained were processed and analyzed. Variations in the compressive strength and tensile strength were attributed to several aspects, such the specimen size, which was not uniform, the scaffold composition, scaffold pore size, which was also not uniform, and the degradation of the polymer. The chitosan-hydroxyapatite-collagen composite scaffold does not exhibit differences in the tensile strength and compressive strength before and after immersion in SBF.

Computer Simulation of Spatial Arrangement and Connectivity of Particles in Three-Dimensional Microstructure: Application to Model Electrical Conductivity of Polymer Matrix Composite

NASA Technical Reports Server (NTRS)

Louis, P.; Gokhale, A. M.

1996-01-01

Computer simulation is a powerful tool for analyzing the geometry of three-dimensional microstructure. A computer simulation model is developed to represent the three-dimensional microstructure of a two-phase particulate composite where particles may be in contact with one another but do not overlap significantly. The model is used to quantify the "connectedness" of the particulate phase of a polymer matrix composite containing hollow carbon particles in a dielectric polymer resin matrix. The simulations are utilized to estimate the morphological percolation volume fraction for electrical conduction, and the effective volume fraction of the particles that actually take part in the electrical conduction. The calculated values of the effective volume fraction are used as an input for a self-consistent physical model for electrical conductivity. The predicted values of electrical conductivity are in very good agreement with the corresponding experimental data on a series of specimens having different particulate volume fraction.

Development of High Fidelity, Fuel-Like Thermal Simulators for Non-Nuclear Testing

NASA Technical Reports Server (NTRS)

Bragg-Sitton, S. M.; Farmer, J.; Dixon, D.; Kapernick, R.; Dickens, R.; Adams, M.

2007-01-01

Non-nuclear testing can be a valuable tool in development of a space nuclear power or propulsion system. In a non-nuclear test bed, electric heaters are used to simulate the heat from nuclear fuel. Work at the NASA Marshall Space Flight Center seeks to develop high fidelity thermal simulators that not only match the static power profile that would be observed in an operating, fueled nuclear reactor, but to also match the dynamic fuel pin performance during feasible transients. Comparison between the fuel pins and thermal simulators is made at the fuel clad surface, which corresponds to the sheath surface in the thermal simulator. Static and dynamic fuel pin performance was determined using SINDA-FLUINT analysis, and the performance of conceptual thermal simulator designs was compared to the expected nuclear performance. Through a series of iterative analysis, a conceptual high fidelity design will be developed, followed by engineering design, fabrication, and testing to validate the overall design process. Although the resulting thermal simulator will be designed for a specific reactor concept, establishing this rigorous design process will assist in streamlining the thermal simulator development for other reactor concepts.

PSA: A program to streamline orbit determination for launch support operations

NASA Technical Reports Server (NTRS)

Legerton, V. N.; Mottinger, N. A.

1988-01-01

An interactive, menu driven computer program was written to streamline the orbit determination process during the critical launch support phase of a mission. Residing on a virtual memory minicomputer, this program retains the quantities in-core needed to obtain a least squares estimate of the spacecraft trajectory with interactive displays to assist in rapid radio metric data evaluation. Menu-driven displays allow real time filter and data strategy development. Graphical and tabular displays can be sent to a laser printer for analysis without exiting the program. Products generated by this program feed back to the main orbit determination program in order to further refine the estimate of the trajectory. The final estimate provides a spacecraft ephemeris which is transmitted to the mission control center and used for antenna pointing and frequency predict generation by the Deep Space Network. The development and implementation process of this program differs from that used for most other navigation software by allowing the users to check important operating features during development and have changes made as needed.

Structure, corrosion behavior and mechanical property of a novel poly(vinyl alcohol) composite in simulated body fluid.

PubMed

Li, Juan; Suo, Jinping; Zou, Peng; Jia, Lintao; Wang, Shifang

2010-01-01

The data for long-term drug-delivery systems are scarce compared to the short-term systems because the required research efforts are more time-consuming. In this study, we report a novel cross-linked composite based on poly(vinyl alcohol) (PVA) containing cupric ions for long-term delivery, which is helpful for contraception and trace element balance in the human body. The composition, corrosion products, crystal structure, chemical structure and mechanical stability of the composite, after being immersed in simulated body fluid (SBF) for one year, were studied by X-ray fluorescence spectroscopy (XRF), X-ray diffraction (XRD), differential scanning calorimetry (DSC), Fourier-transform infrared spectroscopy (FT-IR) and mechanical testing. The results show that no other new elements, such as P, Cl and Ca, appear on the surface of the composite and no Cu(2)O was formed after immersion in SBF for one year. The effectiveness of copper can be greatly improved and the side-effects caused by these compounds might also be eliminated. Furthermore, this novel composite exhibits long-term mechanical stability in SBF. The present in vitro long-term data suggest that this novel copper-containing composite may serve as a substitute for conventional materials of copper-containing intrauterine devices (Cu-IUDs) and as a carrier for controlled-release material in a variety of other applications.

Simulations and observations of plasma depletion, ion composition, and airglow emissions in two auroral ionospheric depletion experiments

NASA Technical Reports Server (NTRS)

Yau, A. W.; Whalen, B. A.; Harris, F. R.; Gattinger, R. L.; Pongratz, M. B.

1985-01-01

Observations of plasma depletion, ion composition modification, and airglow emissions in the Waterhole experiments are presented. The detailed ion chemistry and airglow emission processes related to the ionospheric hole formation in the experiment are examined, and observations are compared with computer simulation results. The latter indicate that the overall depletion rates in different parts of the depletion region are governed by different parameters.

Managing complexity in simulations of land surface and near-surface processes

DOE PAGES

Coon, Ethan T.; Moulton, J. David; Painter, Scott L.

2016-01-12

Increasing computing power and the growing role of simulation in Earth systems science have led to an increase in the number and complexity of processes in modern simulators. We present a multiphysics framework that specifies interfaces for coupled processes and automates weak and strong coupling strategies to manage this complexity. Process management is enabled by viewing the system of equations as a tree, where individual equations are associated with leaf nodes and coupling strategies with internal nodes. A dynamically generated dependency graph connects a variable to its dependencies, streamlining and automating model evaluation, easing model development, and ensuring models aremore » modular and flexible. Additionally, the dependency graph is used to ensure that data requirements are consistent between all processes in a given simulation. Here we discuss the design and implementation of these concepts within the Arcos framework, and demonstrate their use for verification testing and hypothesis evaluation in numerical experiments.« less

Streamlining and Standardizing Due Diligence to Ensure Quality of PV Power Plants

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kurtz, Sarah

Those investing in PV power plants would like to have confidence that the plants will provide the anticipated return on investment. While due diligence is capably performed by independent engineers today, as PV systems mature, there will be benefit in standardization and streamlining of this process. The IECRE has defined technical information that is needed as a basis for each transaction step such as approving a design to begin construction, documenting readiness to operate, quantifying performance after a year of operation, and assessing the health of the plant in preparation for sale of the plant. The technical requirements have beenmore » defined by IEC Technical Committee 82 and have been designed to be both effective and efficient in completing the assessments. This workshop will describe these new tools that are now available to the community and will include a panel/audience discussion about how and when they can be most effectively used.« less

Fluid-Structure Interaction in Composite Structures

DTIC Science & Technology

2014-03-01

polymer composite structures. Some previous experimental observations were confirmed using the results from the computer simulations , which also...computer simulations , which also enhanced understanding the effect of FSI on dynamic responses of composite structures. vi THIS PAGE INTENTIONALLY...forces) are applied. A great amount of research has been made using the FEM to study and simulate the cases when the structures are surrounded by

Trends in simulated chemical composition of global and regional population-weighted fine particulate matter over the recent 25 years

NASA Astrophysics Data System (ADS)

Li, C.; Martin, R.; van Donkelaar, A.; Boys, B.; Hammer, M. S.; Xu, J.; Marais, E. A.; Reff, A.; Strum, M.; Ridley, D. A.; Crippa, M.; Zhang, Q.

2017-12-01

We interpret in situ and satellite observations with a chemical transport model (GEOS-Chem) to understand global trends in population-weighted mean chemical composition of fine particulate matter (PM2.5) over 1989-2013. Simulated PM2.5 composition concentrations at 2˚ × 2.5˚ resolution are downscaled to 0.1˚ × 0.1˚ with satellite-based estimates of PM2.5 to better represent population exposure. Trends in simulated and observed population-weighted mean PM2.5 composition over 1989-2013 exhibit a high degree of consistency for (in situ vs. downscaled simulation) PM2.5 (-2.4 vs. -2.4 % yr-1), secondary inorganic aerosols (-4.3 vs. -4.1% yr-1), organic aerosols (OA, -3.6 vs. -3.0 % yr-1) and black carbon (-4.3 vs. -3.9 % yr-1) over North America, as well as sulfate (-4.7 vs. -5.8 % yr-1) over Europe. The downscaled simulation also has overlapping 95% confidence intervals with satellite-derived trends in population-weighted mean PM2.5 for 20 of the 21 Global Burden of Disease Study (GBD) regions over 1998-2013. Over 1989-2013, most (79%) of the simulated increase in global population-weighted mean PM2.5 of 0.28 μg m-3yr-1 is explained by significantly (p < 0.05) increasing OA (0.10 μg m-3yr-1), nitrate (0.05 μg m-3yr-1), sulfate (0.04 μg m-3yr-1) and ammonium (0.03 μg m-3yr-1). These species predominantly drive trends in population-weighted mean PM2.5 over populous regions of South Asia (0.94 μg m-3yr-1), East Asia (0.66 μg m-3yr-1), Western Europe (-0.47 μg m-3yr-1) and North America (-0.32 μg m-3yr-1), primarily due to changes in anthropogenic emissions. Mineral dust from deserts and OA over open burning regions usually cause weak, insignificant trends in population-weighted mean PM2.5, despite strong inter-annual variation. Global trends in area-weighted mean PM2.5 differ significantly from population-weighted trends in both the magnitude and sign, indicating the importance of population weighting for relevance to human exposure studies. This study

Damage accumulation in titanium matrix composites under generic hypersonic vehicle flight simulation and sustained loads

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johnson, W.S.; Mirdamadi, M.; Bakuckas, J.G. Jr.

1996-12-31

Titanium matrix composites (TMC), such as Ti-15V-3Cr-3Al-3Sn (Ti-15-3) reinforced with continuous silicon-carbide fibers (SCS-6), are being evaluated for use in hypersonic vehicles and advanced gas turbine engines where high strength-to-weight and high stiffness-to-weight ratios at elevated temperatures are critical. Such applications expose the composite to mechanical fatigue loading as well as thermally induced cycles. The damage accumulation behavior of a [0/90]2s laminate made of Ti-15V-3Cr-3Al-3Sn (Ti-15-3) reinforced with continuous silicon-carbide fibers (SCS-6) subjected to a simulated generic hypersonic flight profile, portions of the flight profile, and sustained loads was evaluated experimentally. Portions of the flight profile were used separately tomore » isolate combinations of load and time at temperature that influenced the fatigue behavior of the composite. Sustained load tests were also conducted and the results were compared with the fatigue results under the flight profile and its portions. The test results indicated that the fatigue strength of this materials system is considerably reduced by a combination of load and time at temperature.« less

Experimental and Simulation Investigation of Tri-Sector Cylindrical Dielectric Resonator Antenna in composite forms for Wireless Applications

NASA Astrophysics Data System (ADS)

Ranjan, Pinku; Gangwar, Ravi Kumar

2016-11-01

In this article, a tri-sector cylindrical dielectric resonator antenna (t-CDRA) has been introduced by splitting CDRA into three uniform sectors and all three uniform sectors are packed together in a compact way on a metallic ground plane. A coaxial probe feed is used to excite the proposed composite t-CDRA at the center position. Multi-segmentation approach has been applied for further improvement in bandwidth of proposed t-CDRA. The proposed composite t-CDRA has been designed using HFSS simulation software and analyzed using theoretical analysis. The prototype of t-CDRA, three elements t-CDRA and three elements dual segment t-CDRA has been fabricated for measurement. The input characteristics, near field, far field distribution of the proposed t-CDRAs have been studied through HFSS simulation software and their results are compared with corresponding experimental results. Proposed segmented t-CDRA has wide impedance bandwidth (|S11|≤-10 dB) of 85 % with monopole-like radiation pattern. The peak gain of segmented t-CDRA has 5.1 dBi with 98.5 % radiation efficiency. The proposed segmented t-CDRA may find suitable applications in 5.0 GHz WLAN and WiMAX band.

Understanding Differences in the Response to Composition Change as Simulated by CCMVal Models

NASA Technical Reports Server (NTRS)

Douglass, Anne R.; Strahan, Susan E.; Oman, Luke D.

2012-01-01

Chemistry climate models (CCMs) have a common conceptual basis. Differences in implementation lead to differences in the stratospheric ozone response to changes in composition and climate. Although evaluation by CCMVal-2 identified strengths and weaknesses of participant models, the evaluation results were not used to discriminate among projections for future ozone evolution, at least in part because the overall diagnostic evaluation did not cleanly relate to the differences in CCM response. Here we use a subset of CCMVal diagnostics and additional analysis to understand the differences in response. In the upper stratosphere, differences in simulated temperature and total odd nitrogen prior to increases in chlorine loading explain the large differences in CCM sensitivity. In the lower atmosphere, there are two principle contributions to differences in CCM sensitivity to chlorine and climate change. First, differences in the lower stratospheric ClO affect simulated sensitivity to chlorine. CCMs with best transport performance match NDACC column HCl measurements at a broad range of latitudes. Other CCMs disagree with observations due to differences in total inorganic chlorine, partitioning between HCl and ClONO2, or both. Differences in ClONO2 are directly related to differences in simulated ClO. Second, although all CCMs predict increased tropical upwelling, the rate of increase varies and contributes to differences in tropical ozone and the 60N-60S column average.

Aerobiological Stabilities of Different Species of Gram-Negative Bacteria, Including Well-Known Biothreat Simulants, in Single-Cell Particles and Cell Clusters of Different Compositions

PubMed Central

Skogan, Gunnar

2017-01-01

ABSTRACT The ability to perform controlled experiments with bioaerosols is a fundamental enabler of many bioaerosol research disciplines. A practical alternative to using hazardous biothreat agents, e.g., for detection equipment development and testing, involves using appropriate model organisms (simulants). Several species of Gram-negative bacteria have been used or proposed as biothreat simulants. However, the appropriateness of different bacterial genera, species, and strains as simulants is still debated. Here, we report aerobiological stability characteristics of four species of Gram-negative bacteria (Pantoea agglomerans, Serratia marcescens, Escherichia coli, and Xanthomonas arboricola) in single-cell particles and cell clusters produced using four spray liquids (H2O, phosphate-buffered saline[PBS], spent culture medium[SCM], and a SCM-PBS mixture). E. coli showed higher stability in cell clusters from all spray liquids than the other species, but it showed similar or lower stability in single-cell particles. The overall stability was higher in cell clusters than in single-cell particles. The highest overall stability was observed for bioaerosols produced using SCM-containing spray liquids. A key finding was the observation that stability differences caused by particle size or compositional changes frequently followed species-specific patterns. The results highlight how even moderate changes to one experimental parameter, e.g., bacterial species, spray liquid, or particle size, can strongly affect the aerobiological stability of Gram-negative bacteria. Taken together, the results highlight the importance of careful and informed selection of Gram-negative bacterial biothreat simulants and also the accompanying particle size and composition. The outcome of this work contributes to improved selection of simulants, spray liquids, and particle size for use in bioaerosol research. IMPORTANCE The outcome of this work contributes to improved selection of simulants

Telescoping Mechanics: A New Paradigm for Composite Behavior Simulation

NASA Technical Reports Server (NTRS)

Chamis, C. C.; Murthy, P. L. N.; Gotsis, P. K.; Mital. S. K.

2004-01-01

This report reviews the application of telescoping mechanics to composites using recursive laminate theory. The elemental scale is the fiber-matrix slice, the behavior of which propagates to laminate. The results from using applications for typical, hybrid, and smart composites and composite-enhanced reinforced concrete structures illustrate the versatility and generality of telescoping scale mechanics. Comparisons with approximate, single-cell, and two- and three-dimensional finite-element methods demonstrate the accuracy and computational effectiveness of telescoping scale mechanics for predicting complex composite behavior.

Effect of an imaging-based streamlined electronic healthcare process on quality and costs.

PubMed

Bui, Alex A T; Taira, Ricky K; Goldman, Dana; Dionisio, John David N; Aberle, Denise R; El-Saden, Suzie; Sayre, James; Rice, Thomas; Kangarloo, Hooshang

2004-01-01

A streamlined process of care supported by technology and imaging may be effective in managing the overall healthcare process and costs. This study examined the effect of an imaging-based electronic process of care on costs and rates of hospitalization, emergency room (ER) visits, specialist diagnostic referrals, and patient satisfaction. A healthcare process was implemented for an employer group, highlighting improved patient access to primary care plus routine use of imaging and teleconsultation with diagnostic specialists. An electronic infrastructure supported patient access to physicians and communication among healthcare providers. The employer group, a self-insured company, manages a healthcare plan for its employees and their dependents: 4,072 employees were enrolled in the test group, and 7,639 in the control group. Outcome measures for expenses and frequency of hospitalizations, ER visits, traditional specialist referrals, primary care visits, and imaging utilization rates were measured using claims data over 1 year. Homogeneity tests of proportions were performed with a chi-square statistic, mean differences were tested by two-sample t-tests. Patient satisfaction with access to healthcare was gauged using results from an independent firm. Overall per member/per month costs post-implementation were lower in the enrolled population (126 dollars vs 160 dollars), even though occurrence of chronic/expensive diseases was higher in the enrolled group (18.8% vs 12.2%). Lower per member/per month costs were seen for inpatient (33.29 dollars vs 35.59 dollars); specialist referrals (21.36 dollars vs 26.84 dollars); and ER visits (3.68 dollars vs 5.22 dollars). Moreover, the utilization rate for hospital admissions, ER visits, and traditional specialist referrals were significantly lower in the enrolled group, although primary care and imaging utilization were higher. Comparison to similar employer groups showed that the company's costs were lower than national

Simplified hydrodynamic analysis on the general shape of the hill charts of Francis turbines using shroud-streamline modeling

NASA Astrophysics Data System (ADS)

Iliev, I.; Trivedi, C.; Dahlhaug, O. G.

2018-06-01

The paper presents a simplified one-dimensional calculation of the efficiency hill-chart for Francis turbines, based on the velocity triangles at the inlet and outlet of the runner’s blade. Calculation is done for one streamline, namely the shroud streamline in the meridional section, where an efficiency model is established and iteratively approximated in order to satisfy the Euler equation for turbomachines at a wide operating range around the best efficiency point (BEP). Using the presented method, hill charts are calculated for one splitter-bladed Francis turbine runner and one Reversible Pump-Turbine (RPT) runner operated in the turbine mode. Both turbines have similar and relatively low specific speeds of nsQ = 23.3 and nsQ = 27, equal inlet and outlet diameters and are designed to fit in the same turbine rig for laboratory measurements (i.e. spiral casing and draft tube are the same). Calculated hill charts are compared against performance data obtained experimentally from model tests according to IEC standards for both turbines. Good agreement between theoretical and experimental results is observed when comparing the shapes of the efficiency contours in the hill-charts. The simplified analysis identifies the design parameters that defines the general shape and inclination of the turbine’s hill charts and, with some additional improvements in the loss models used, it can be used for quick assessment of the performance at off-design conditions during the design process of hydraulic turbines.

Effect of particle size and percentages of Boron carbide on the thermal neutron radiation shielding properties of HDPE/B4C composite: Experimental and simulation studies

NASA Astrophysics Data System (ADS)

Soltani, Zahra; Beigzadeh, Amirmohammad; Ziaie, Farhood; Asadi, Eskandar

2016-10-01

In this paper the effects of particle size and weight percentage of the reinforcement phase on the absorption ability of thermal neutron by HDPE/B4C composites were investigated by means of Monte-Carlo simulation method using MCNP code and experimental studies. The composite samples were prepared using the HDPE filled with different weight percentages of Boron carbide powder in the form of micro and nano particles. Micro and nano composite were prepared under the similar mixing and moulding processes. The samples were subjected to thermal neutron radiation. Neutron shielding efficiency in terms of the neutron transmission fractions of the composite samples were investigated and compared with simulation results. According to the simulation results, the particle size of the radiation shielding material has an important role on the shielding efficiency. By decreasing the particle size of shielding material in each weight percentages of the reinforcement phase, better radiation shielding properties were obtained. It seems that, decreasing the particle size and homogeneous distribution of nano forms of B4C particles, cause to increase the collision probability between the incident thermal neutron and the shielding material which consequently improve the radiation shielding properties. So, this result, propose the feasibility of nano composite as shielding material to have a high performance shielding characteristic, low weight and low thick shielding along with economical benefit.

Probabilistic Simulation for Combined Cycle Fatigue in Composites

NASA Technical Reports Server (NTRS)

Chamis, Christos C.

2010-01-01

A methodology to compute probabilistic fatigue life of polymer matrix laminated composites has been developed and demonstrated. Matrix degradation effects caused by long term environmental exposure and mechanical/thermal cyclic loads are accounted for in the simulation process. A unified time-temperature-stress dependent multifactor interaction relationship developed at NASA Glenn Research Center has been used to model the degradation/aging of material properties due to cyclic loads. The fast probability integration method is used to compute probabilistic distribution of response. Sensitivities of fatigue life reliability to uncertainties in the primitive random variables (e.g., constituent properties, fiber volume ratio, void volume ratio, ply thickness, etc.) computed and their significance in the reliability-based design for maximum life is discussed. The effect of variation in the thermal cyclic loads on the fatigue reliability for a (0/+/- 45/90)s graphite/epoxy laminate with a ply thickness of 0.127 mm, with respect to impending failure modes has been studied. The results show that, at low mechanical cyclic loads and low thermal cyclic amplitudes, fatigue life for 0.999 reliability is most sensitive to matrix compressive strength, matrix modulus, thermal expansion coefficient, and ply thickness. Whereas at high mechanical cyclic loads and high thermal cyclic amplitudes, fatigue life at 0.999 reliability is more sensitive to the shear strength of matrix, longitudinal fiber modulus, matrix modulus, and ply thickness.

Simulation of the microwave heating of a thin multilayered composite material: A parameter analysis

NASA Astrophysics Data System (ADS)

Tertrais, Hermine; Barasinski, Anaïs; Chinesta, Francisco

2018-05-01

Microwave (MW) technology relies on volumetric heating. Thermal energy is transferred to the material that can absorb it at specific frequencies. The complex physics involved in this process is far from being understood and that is why a simulation tool has been developed in order to solve the electromagnetic and thermal equations in such a complex material as a multilayered composite part. The code is based on the in-plane-out-of-plane separated representation within the Proper Generalized Decomposition framework. To improve the knowledge on the process, a parameter study in carried out in this paper.

Control of Heat Fluxes on the Surface of the Body Streamlined by Supersonic Flow with the Help of MHD Method

DTIC Science & Technology

2008-10-01

Supersonic Flow with the Help of MHD Method 5a. CONTRACT NUMBER ISTC Registration No: 3475 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6...MONITOR’S ACRONYM(S) 11. SPONSOR/MONITOR’S REPORT NUMBER(S) ISTC 05-7004 12. DISTRIBUTION/AVAILABILITY STATEMENT Approved for public release...Center ( ISTC ), Moscow. ISTC Project No. 3475р Control of heat fluxes on the surface of the body streamlined by supersonic flow with the help of MHD

Progressive Fracture of Fiber Composite Builtup Structures

NASA Technical Reports Server (NTRS)

Gotsis, Pascal K.; Chamis, Christos C.; Minnetyan, Levon

1996-01-01

The damage progression and fracture of builtup composite structures was evaluated by using computational simulation to examine the behavior and response of a stiffened composite (0 +/- 45/90)(sub s6) laminate panel subjected to a bending load. The damage initiation, growth, accumulation, progression, and propagation to structural collapse were simulated. An integrated computer code (CODSTRAN) was augmented for the simulation of the progressive damage and fracture of builtup composite structures under mechanical loading. Results showed that damage initiation and progression have a significant effect on the structural response. Also investigated was the influence of different types of bending load on the damage initiation, propagation, and final fracture of the builtup composite panel.

Simulation of dilute polymeric fluids in a three-dimensional contraction using a multiscale FENE model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Griebel, M., E-mail: griebel@ins.uni-bonn.de, E-mail: ruettgers@ins.uni-bonn.de; Rüttgers, A., E-mail: griebel@ins.uni-bonn.de, E-mail: ruettgers@ins.uni-bonn.de

The multiscale FENE model is applied to a 3D square-square contraction flow problem. For this purpose, the stochastic Brownian configuration field method (BCF) has been coupled with our fully parallelized three-dimensional Navier-Stokes solver NaSt3DGPF. The robustness of the BCF method enables the numerical simulation of high Deborah number flows for which most macroscopic methods suffer from stability issues. The results of our simulations are compared with that of experimental measurements from literature and show a very good agreement. In particular, flow phenomena such as a strong vortex enhancement, streamline divergence and a flow inversion for highly elastic flows are reproduced.more » Due to their computational complexity, our simulations require massively parallel computations. Using a domain decomposition approach with MPI, the implementation achieves excellent scale-up results for up to 128 processors.« less

GPU-based simulations of fracture in idealized brick and mortar composites

NASA Astrophysics Data System (ADS)

William Pro, J.; Kwei Lim, Rone; Petzold, Linda R.; Utz, Marcel; Begley, Matthew R.

2015-07-01

Stiff ceramic platelets (or bricks) that are aligned and bonded to a second ductile phase with low volume fraction (mortar) are a promising pathway to produce stiff, high-toughness composites. For certain ranges of constituent properties, including those of some synthetic analogs to nacre, one can demonstrate that the deformation is dominated by relative brick motions. This paper describes simulations of fracture that explicitly track the motions of individual rigid bricks in an idealized microstructure; cohesive tractions acting between the bricks introduce elastic, plastic and rupture behaviors. Results are presented for the stresses and damage near macroscopic cracks with different brick orientations relative to the loading orientation. The anisotropic macroscopic initiation toughness is computed for small-scale yielding conditions and is shown to be independent of specimen geometry and loading configuration. The results are shown to be in agreement with previously published experiments on synthetic nacre.

Atomistic simulation of the thermal conductivity in amorphous SiO2 matrix/Ge nanocrystal composites

NASA Astrophysics Data System (ADS)

Kuryliuk, Vasyl V.; Korotchenkov, Oleg A.

2017-04-01

We use nonequilibrium molecular dynamics computer simulations with the Tersoff potential aiming to provide a comprehensive picture of the thermal conductivity of amorphous SiO2 (a-SiO2) matrix with embedded Ge nanocrystals (nc-Ge). The modelling predicts the a-SiO2 matrix thermal conductivity in a temperature range of 50 < T < 500 K yielding a fair agreement with experiment at around room temperature. It is worth noticing that the predicted room-temperature thermal conductivity in a-SiO2 is in very good agreement with the experimental result, which is in marked contrast with the thermal conductivity calculated employing the widely used van Beest-Kramer-van Santen (BKS) potential. We show that the thermal conductivity of composite nc-Ge/a-SiO2 systems decreases steadily with increasing the volume fraction of Ge inclusions, indicative of enhanced interface scattering of phonons imposed by embedded Ge nanocrystals. We also observe that increasing the volume fractions above a certain threshold value results in a progressively increased thermal conductivity of the nanocomposite, which can be explained by increasing volume fraction of a better thermally conducting Ge. Finally, non-equilibrium molecular dynamics simulations with the Tersoff potential are promising for computing the thermal conductivity of nanocomposites based on amorphous SiO2 and can be readily scaled to more complex composite structures with embedded nanoparticles, which thus help design nanocomposites with desired thermal properties.

Innovative Composite Structure Design for Blast Protection

DTIC Science & Technology

2007-01-01

2007-01-0483 Innovative Composite Structure Design for Blast Protection Dongying Jiang, Yuanyuan Liu MKP Structural Design Associates, Inc...protect vehicle and occupants against various explosives. The multi-level and multi-scenario blast simulation and design system integrates three major...numerical simulation of a BTR composite under a blast event. The developed blast simulation and design system will enable the prediction, design, and

Challenges of NDE Simulation Tool Challenges of NDE Simulation Tool

NASA Technical Reports Server (NTRS)

Leckey, Cara A. C.; Juarez, Peter D.; Seebo, Jeffrey P.; Frank, Ashley L.

2015-01-01

Realistic nondestructive evaluation (NDE) simulation tools enable inspection optimization and predictions of inspectability for new aerospace materials and designs. NDE simulation tools may someday aid in the design and certification of advanced aerospace components; potentially shortening the time from material development to implementation by industry and government. Furthermore, modeling and simulation are expected to play a significant future role in validating the capabilities and limitations of guided wave based structural health monitoring (SHM) systems. The current state-of-the-art in ultrasonic NDE/SHM simulation cannot rapidly simulate damage detection techniques for large scale, complex geometry composite components/vehicles with realistic damage types. This paper discusses some of the challenges of model development and validation for composites, such as the level of realism and scale of simulation needed for NASA' applications. Ongoing model development work is described along with examples of model validation studies. The paper will also discuss examples of the use of simulation tools at NASA to develop new damage characterization methods, and associated challenges of validating those methods.

A coarse grained molecular dynamics simulation study on the structural properties of carbon nanotube-dendrimer composites.

PubMed

Kavyani, Sajjad; Dadvar, Mitra; Modarress, Hamid; Amjad-Iranagh, Sepideh

2018-04-25

By employing coarse grained (CG) molecular dynamics (MD) simulation, the effect of the size and hydrophilic/hydrophobic properties of the interior/exterior structures of the dendrimers in carbon nanotube (CNT)-dendrimer composites has been studied, to find a stable composite with high solubility in water and the capability to be used in drug delivery applications. For this purpose, composites consisting of core-shell dendrimer complexes including: [PPI{core}-PAMAM{shell}], [PAMAM{core}-polyethyleneglycol (PEG){shell}] and [PAMAM{core}-fattyacid (FTA){shell}] were constructed. A new CG model for the fatty acid (FTA) molecules as functionalized to the dendrimer was developed, which, unlike the previous models, could generate the structural conformations of the FTA properly. The obtained results indicated that the dendrimer complexes with short FTA chains can form stable composites with the CNT. Also, it was found that the pristine PAMAM and PPI-PAMAM with small PPI, and PAMAM-PEG dendrimers with short PEG chains, can distribute their chains into the water medium and interact with the CNT efficiently, to form a stable water-soluble CNT-dendrimer composite. The results demonstrated that the structural difference between the interior and exterior of a core-shell dendrimer complex can prevent the core and the interior layers of the dendrimer complex from interacting with the CNT. An overall analysis of the results manifested that the CNT-PAMAM:4-PEG:4 is the most stable composite, due to strong binding of the dendrimer with the CNT while also having high solubility in water, and its core retains its structure properly and unchanged, suitable for encapsulating drugs in the targeted delivery applications.

Depth of composite polymerization within simulated root canals using light-transmitting posts.

PubMed

Lui, J L

1994-01-01

In this study, the depth of cure of composite resins cured within simulated root canals by means of light-transmitting plastic posts was compared to that achieved by the conventional light-curing method. Six sizes of posts with diameters of 1.05 mm, 1.20 mm, 1.35 mm, 1.50 mm, 1.65 mm, and 1.80 mm were investigated. In general, the larger the post diameter, the greater was the depth of cure. There were significant differences in the depth of cure between the control and all sizes of posts investigated. There were also significant differences between the various post diameters except for the 1.35 mm and 1.50 mm diameter posts. It was possible to achieve a depth of cure exceeding 11 mm using these light-transmitting posts.

Damage Simulation in Non-Crimp Fabric Composite Plates Subjected to Impact Loads

NASA Technical Reports Server (NTRS)

Satyanarayana, Arunkumar; Bogert, Philip B.; Aitharaju, Venkat; Aashat, Satvir; Kia, Hamid

2014-01-01

Progressive failure analysis (PFA) of non-crimp fabric (NCF) composite laminates subjected to low velocity impact loads was performed using the COmplete STress Reduction (COSTR) damage model implemented through VUMAT and UMAT41 user subroutines in the frame works of the commercial finite element programs ABAQUS/Explicit and LS-DYNA, respectively. To validate the model, low velocity experiments were conducted and detailed correlations between the predictions and measurements for both intra-laminar and inter-laminar failures were made. The developed material and damage model predicts the peak impact load and duration very close with the experimental results. Also, the simulation results of delamination damage between the ply interfaces, in-plane matrix damages and fiber damages were all in good agreement with the measurements from the non-destructive evaluation data.

New approach in direct-simulation of gas mixtures

NASA Technical Reports Server (NTRS)

Chung, Chan-Hong; De Witt, Kenneth J.; Jeng, Duen-Ren

1991-01-01

Results are reported for an investigation of a new direct-simulation Monte Carlo method by which energy transfer and chemical reactions are calculated. The new method, which reduces to the variable cross-section hard sphere model as a special case, allows different viscosity-temperature exponents for each species in a gas mixture when combined with a modified Larsen-Borgnakke phenomenological model. This removes the most serious limitation of the usefulness of the model for engineering simulations. The necessary kinetic theory for the application of the new method to mixtures of monatomic or polyatomic gases is presented, including gas mixtures involving chemical reactions. Calculations are made for the relaxation of a diatomic gas mixture, a plane shock wave in a gas mixture, and a chemically reacting gas flow along the stagnation streamline in front of a hypersonic vehicle. Calculated results show that the introduction of different molecular interactions for each species in a gas mixture produces significant differences in comparison with a common molecular interaction for all species in the mixture. This effect should not be neglected for accurate DSMC simulations in an engineering context.

Origins and Destinations: Tracking Planet Composition through Planet Formation Simulations

NASA Astrophysics Data System (ADS)

Chance, Quadry; Ballard, Sarah

2018-01-01

There are now several thousand confirmed exoplanets, a number which far exceeds our resources to study them all in detail. In particular, planets around M dwarfs provide the best opportunity for in-depth study of their atmospheres by telescopes in the near future. The question of which M dwarf planets most merit follow-up resources is a pressing one, given that NASA’s TESS mission will soon find hundreds of such planets orbiting stars bright enough for both ground and spaced-based follow-up.Our work aims to predict the approximate composition of planets around these stars through n-body simulations of the last stage of planet formation. With a variety of initial disk conditions, we investigate how the relative abundances of both refractory and volatile compounds in the primordial planetesimals are mapped to the final planet outcomes. These predictions can serve to provide a basis for making an educated guess about (a) which planets to observe with precious resources like JWST and (b) how to identify them based on dynamical clues.

Progressive Fracture of Composite Structures

NASA Technical Reports Server (NTRS)

Minnetyan, Levon

2001-01-01

This report includes the results of a research in which the COmposite Durability STRuctural ANalysis (CODSTRAN) computational simulation capabilities were augmented and applied to various structures for demonstration of the new features and verification. The first chapter of this report provides an introduction to the computational simulation or virtual laboratory approach for the assessment of damage and fracture progression characteristics in composite structures. The second chapter outlines the details of the overall methodology used, including the failure criteria and the incremental/iterative loading procedure with the definitions of damage, fracture, and equilibrium states. The subsequent chapters each contain an augmented feature of the code and/or demonstration examples. All but one of the presented examples contains laminated composite structures with various fiber/matrix constituents. For each structure simulated, damage initiation and progression mechanisms are identified and the structural damage tolerance is quantified at various degradation stages. Many chapters contain the simulation of defective and defect free structures to evaluate the effects of existing defects on structural durability.

Filaments in curved streamlines: rapid formation of Staphylococcus aureus biofilm streamers

NASA Astrophysics Data System (ADS)

Kim, Minyoung Kevin; Drescher, Knut; Pak, On Shun; Bassler, Bonnie L.; Stone, Howard A.

2014-06-01

Biofilms are surface-associated conglomerates of bacteria that are highly resistant to antibiotics. These bacterial communities can cause chronic infections in humans by colonizing, for example, medical implants, heart valves, or lungs. Staphylococcus aureus, a notorious human pathogen, causes some of the most common biofilm-related infections. Despite the clinical importance of S. aureus biofilms, it remains mostly unknown how physical effects, in particular flow, and surface structure influence biofilm dynamics. Here we use model microfluidic systems to investigate how environmental factors, such as surface geometry, surface chemistry, and fluid flow affect biofilm development of S. aureus. We discovered that S. aureus rapidly forms flow-induced, filamentous biofilm streamers, and furthermore if surfaces are coated with human blood plasma, streamers appear within minutes and clog the channels more rapidly than if the channels are uncoated. To understand how biofilm streamer filaments reorient in flows with curved streamlines to bridge the distances between corners, we developed a mathematical model based on resistive force theory of slender filaments. Understanding physical aspects of biofilm formation of S. aureus may lead to new approaches for interrupting biofilm formation of this pathogen.

Numerical simulation of fiber interaction in short-fiber injection-molded composite using different cavity geometries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thi, Thanh Binh Nguyen, E-mail: nttbinh@kit.ac.jp; Yokoyama, Atsushi, E-mail: yokoyama@kit.ac.jp; Hamanaka, Senji

The theoretical fiber-interaction model for calculating the fiber orientation in the injection molded short fiber/thermoplastic composite parts was proposed. The proposed model included the fiber dynamics simulation in order to obtain an equation of the global interaction coefficient and accurate estimate of the fiber interacts at all orientation states. The steps to derive the equation for this coefficient in short fiber suspension as a function of the fiber aspect ratio, volume fraction and general shear rate are delineated. Simultaneously, the high-resolution 3D X-ray computed tomography system XVA-160α was used to observe fiber distribution of short-glass-fiber-reinforced polyamide specimens using different cavitymore » geometries. The fiber orientation tensor components are then calculated. Experimental orientation measurements of short-glass-fiber-reinforced polyamide is used to check the ability of present theory for predicting orientation. The experiments and predictions show a quantitative agreement and confirm the basic understanding of fiber orientation in injection-molded composites.« less

Numerical simulation of fiber interaction in short-fiber injection-molded composite using different cavity geometries

NASA Astrophysics Data System (ADS)

Thi, Thanh Binh Nguyen; Yokoyama, Atsushi; Hamanaka, Senji; Yamashita, Katsuhisa; Nonomura, Chisato

2016-03-01

The theoretical fiber-interaction model for calculating the fiber orientation in the injection molded short fiber/thermoplastic composite parts was proposed. The proposed model included the fiber dynamics simulation in order to obtain an equation of the global interaction coefficient and accurate estimate of the fiber interacts at all orientation states. The steps to derive the equation for this coefficient in short fiber suspension as a function of the fiber aspect ratio, volume fraction and general shear rate are delineated. Simultaneously, the high-resolution 3D X-ray computed tomography system XVA-160α was used to observe fiber distribution of short-glass-fiber-reinforced polyamide specimens using different cavity geometries. The fiber orientation tensor components are then calculated. Experimental orientation measurements of short-glass-fiber-reinforced polyamide is used to check the ability of present theory for predicting orientation. The experiments and predictions show a quantitative agreement and confirm the basic understanding of fiber orientation in injection-molded composites.

Fatty acid composition of plasma lipids and erythrocyte membranes during simulated extravehicular activity

NASA Astrophysics Data System (ADS)

Skedina, M. A.; Katuntsev, V. P.; Buravkova, L. B.; Naidina, V. P.

Ten subjects (from 27 to 41 years) have been participated in 32 experiments. They were decompressed from ground level to 40-35 kPa in altitude chamber when breathed 100% oxygen by mask and performed repeated cycles of exercises (3.0 Kcal/min). The intervals between decompressions were 3-5 days. Plasma lipid and erythrocyte membrane fatty acid composition was evaluated in the fasting venous blood before and immediately after hypobaric exposure. There were 7 cases decompression sickness (DCS). Venous gas bubbles (GB) were detected in 27 cases (84.4%). Any significant changes in the fatty acid composition of erythrocyte membranes and plasma didn't practically induce after the first decompression. However, by the beginning of the second decompression the total lipid level in erythrocyte membranes decreased from 54.6 mg% to 40.4 mg% in group with DCS symptoms and from 51.2 mg% to 35.2 mg% (p < 0.05) without DCS symptoms. In group with DCS symptoms a tendency to increased level of saturated fatty acids in erythrocyte membranes (16:0, 18:0), the level of the polyunsaturated linoleic fatty acid (18:2) and arachidonic acid (20:4) tended to be decreased by the beginning of the second decompression. Insignificant changes in blood plasma fatty acid composition was observed in both groups. The obtained biochemical data that indicated the simulated extravehicular activity (EVA) condition is accompanied by the certain changes in the blood lipid metabolism, structural and functional state of erythrocyte membranes, which are reversible. The most pronounced changes are found in subjects with DCS symptoms.

Fatty acid composition of plasma lipids and erythrocyte membranes during simulated extravehicular activity.

PubMed

Skedina, M A; Katuntsev, V P; Buravkova, L B; Naidina, V P

1998-01-01

Ten subjects (from 27 to 41 years) have been participated in 32 experiments. They were decompressed from ground level to 40-35 kPa in altitude chamber when breathed 100% oxygen by mask and performed repeated cycles of exercises (3.0 Kcal/min). The intervals between decompressions were 3-5 days. Plasma lipid and erythrocyte membrane fatty acid composition was evaluated in the fasting venous blood before and immediately after hypobaric exposure. There were 7 cases decompression sickness (DCS). Venous gas bubbles (GB) were detected in 27 cases (84.4%). Any significant changes in the fatty acid composition of erythrocyte membranes and plasma didn't practically induce after the first decompression. However, by the beginning of the second decompression the total lipid level in erythrocyte membranes decreased from 54.6 mg% to 40.4 mg% in group with DCS symptoms and from 51.2 mg% to 35.2 mg% (p<0.05) without DCS symptoms. In group with DCS symptoms a tendency to increased level of saturated fatty acids in erythrocyte membranes (16:0, 18:0), the level of the polyunsaturated linoleic fatty acid (18:2) and arachidonic acid (20:4) tended to be decreased by the beginning of the second decompression. Insignificant changes in blood plasma fatty acid composition was observed in both groups. The obtained biochemical data that indicated the simulated extravehicular activity (EVA) condition is accompanied by the certain changes in the blood lipid metabolism, structural and functional state of erythrocyte membranes, which are reversible. The most pronounced changes are found in subjects with DCS symptoms.

Progressive Fracture of Fiber Composite Build-Up Structures

NASA Technical Reports Server (NTRS)

Gotsis, Pascal K.; Chamis, C. C.; Minnetyan, Levon

1997-01-01

Damage progression and fracture of built-up composite structures is evaluated by using computational simulation. The objective is to examine the behavior and response of a stiffened composite (0/ +/- 45/90)(sub s6) laminate panel by simulating the damage initiation, growth, accumulation, progression and propagation to structural collapse. An integrated computer code, CODSTRAN, was augmented for the simulation of the progressive damage and fracture of built-up composite structures under mechanical loading. Results show that damage initiation and progression have significant effect on the structural response. Influence of the type of loading is investigated on the damage initiation, propagation and final fracture of the build-up composite panel.

Progressive Fracture of Fiber Composite Build-Up Structures

NASA Technical Reports Server (NTRS)

Minnetyan, Levon; Gotsis, Pascal K.; Chamis, C. C.

1997-01-01

Damage progression and fracture of built-up composite structures is evaluated by using computational simulation. The objective is to examine the behavior and response of a stiffened composite (0 +/-45/90)(sub s6) laminate panel by simulating the damage initiation, growth, accumulation, progression and propagation to structural collapse. An integrated computer code CODSTRAN was augmented for the simulation of the progressive damage and fracture of built-up composite structures under mechanical loading. Results show that damage initiation and progression to have significant effect on the structural response. Influence of the type of loading is investigated on the damage initiation, propagation and final fracture of the build-up composite panel.

Compositional symbol grounding for motor patterns.

PubMed

Greco, Alberto; Caneva, Claudio

2010-01-01

We developed a new experimental and simulative paradigm to study the establishing of compositional grounded representations for motor patterns. Participants learned to associate non-sense arm motor patterns, performed in three different hand postures, with non-sense words. There were two group conditions: in the first (compositional), each pattern was associated with a two-word (verb-adverb) sentence; in the second (holistic), each same pattern was associated with a unique word. Two experiments were performed. In the first, motor pattern recognition and naming were tested in the two conditions. Results showed that verbal compositionality had no role in recognition and that the main source of confusability in this task came from discriminating hand postures. As the naming task resulted too difficult, some changes in the learning procedure were implemented in the second experiment. In this experiment, the compositional group achieved better results in naming motor patterns especially for patterns where hand postures discrimination was relevant. In order to ascertain the differential effect, upon this result, of memory load and of systematic grounding, neural network simulations were also made. After a basic simulation that worked as a good model of subjects performance, in following simulations the number of stimuli (motor patterns and words) was increased and the systematic association between words and patterns was disrupted, while keeping the same number of words and syntax. Results showed that in both conditions the advantage for the compositional condition significantly increased. These simulations showed that the advantage for this condition may be more related to the systematicity rather than to the mere informational gain. All results are discussed in connection to the possible support of the hypothesis of a compositional motor representation and toward a more precise explanation of the factors that make compositional representations working.

Analytical Work in Support of the Design and Operation of Two Dimensional Self Streamlining Test Sections

NASA Technical Reports Server (NTRS)

Judd, M.; Wolf, S. W. D.; Goodyer, M. J.

1976-01-01

A method has been developed for accurately computing the imaginary flow fields outside a flexible walled test section, applicable to lifting and non-lifting models. The tolerances in the setting of the flexible walls introduce only small levels of aerodynamic interference at the model. While it is not possible to apply corrections for the interference effects, they may be reduced by improving the setting accuracy of the portions of wall immediately above and below the model. Interference effects of the truncation of the length of the streamlined portion of a test section are brought to an acceptably small level by the use of a suitably long test section with the model placed centrally.

Retrospection-Simulation-Revision: Approach to the Analysis of the Composition and Characteristics of Medical Waste at a Disaster Relief Site

PubMed Central

Zhang, Li; Wu, Lihua; Tian, Feng; Wang, Zheng

2016-01-01

A large amount of medical waste is produced during disaster relief, posing a potential hazard to the habitat and the environment. A comprehensive understanding of the composition and characteristics of medical waste that requires management is one of the most basic steps in the development of a plan for medical waste management. Unfortunately, limited reliable information is available in the open literature on the characteristics of the medical waste that is generated at disaster relief sites. This paper discusses the analysis of the composition and characteristics of medical waste at a disaster relief site using the retrospection-simulation-revision method. For this study, we obtained 35 medical relief records of the Wenchuan Earthquake, Sichuan, May 2008 from a field cabin hospital. We first present a retrospective analysis of the relief medical records, and then, we simulate the medical waste generated in the affected areas. We ultimately determine the composition and characteristics of medical waste in the affected areas using untreated medical waste to revise the composition of the simulated medical waste. The results from 35 cases showed that the medical waste generated from disaster relief consists of the following: plastic (43.2%), biomass (26.3%), synthetic fiber (15.3%), rubber (6.6%), liquid (6.6%), inorganic salts (0.3%) and metals (1.7%). The bulk density of medical relief waste is 249 kg/m3, and the moisture content is 44.75%. The data should be provided to assist the collection, segregation, storage, transportation, disposal and contamination control of medical waste in affected areas. In this paper, we wish to introduce this research method of restoring the medical waste generated in disaster relief to readers and researchers. In addition, we hope more disaster relief agencies will become aware of the significance of medical case recording and storing. This may be very important for the environmental evaluation of medical waste in disaster areas, as

Retrospection-Simulation-Revision: Approach to the Analysis of the Composition and Characteristics of Medical Waste at a Disaster Relief Site.

PubMed

Zhang, Li; Wu, Lihua; Tian, Feng; Wang, Zheng

2016-01-01

A large amount of medical waste is produced during disaster relief, posing a potential hazard to the habitat and the environment. A comprehensive understanding of the composition and characteristics of medical waste that requires management is one of the most basic steps in the development of a plan for medical waste management. Unfortunately, limited reliable information is available in the open literature on the characteristics of the medical waste that is generated at disaster relief sites. This paper discusses the analysis of the composition and characteristics of medical waste at a disaster relief site using the retrospection-simulation-revision method. For this study, we obtained 35 medical relief records of the Wenchuan Earthquake, Sichuan, May 2008 from a field cabin hospital. We first present a retrospective analysis of the relief medical records, and then, we simulate the medical waste generated in the affected areas. We ultimately determine the composition and characteristics of medical waste in the affected areas using untreated medical waste to revise the composition of the simulated medical waste. The results from 35 cases showed that the medical waste generated from disaster relief consists of the following: plastic (43.2%), biomass (26.3%), synthetic fiber (15.3%), rubber (6.6%), liquid (6.6%), inorganic salts (0.3%) and metals (1.7%). The bulk density of medical relief waste is 249 kg/m3, and the moisture content is 44.75%. The data should be provided to assist the collection, segregation, storage, transportation, disposal and contamination control of medical waste in affected areas. In this paper, we wish to introduce this research method of restoring the medical waste generated in disaster relief to readers and researchers. In addition, we hope more disaster relief agencies will become aware of the significance of medical case recording and storing. This may be very important for the environmental evaluation of medical waste in disaster areas, as

Streamlining Appointment, Promotion, and Tenure Procedures to Promote Early-Career Faculty Success.

PubMed

Smith, Shannon B; Hollerbach, Ann; Donato, Annemarie Sipkes; Edlund, Barbara J; Atz, Teresa; Kelechi, Teresa J

2016-01-01

A critical component of the progression of a successful academic career is being promoted in rank. Early-career faculty are required to have an understanding of appointment, promotion, and tenure (APT) guidelines, but many factors often impede this understanding, thwarting a smooth and planned promotion pathway for professional advancement. This article outlines the steps taken by an APT committee to improve the promotion process from instructor to assistant professor. Six sigma's DMAIC improvement model was selected as the guiding operational framework to remove variation in the promotion process. After faculty handbook revisions were made, several checklists developed, and a process review rubric was implemented; recently promoted faculty were surveyed on satisfaction with the process. Faculty opinions captured in the survey suggest increased transparency in the process and perceived support offered by the APT committee. Positive outcomes include a strengthened faculty support framework, streamlined promotion processes, and improved faculty satisfaction. Changes to the APT processes resulted in an unambiguous and standardized pathway for successful promotion. Copyright © 2016 Elsevier Inc. All rights reserved.

Development of FRP composite structural biomaterials: ultimate strength of the fiber/matrix interfacial bond in in vivo simulated environments.

PubMed

Latour, R A; Black, J

1992-05-01

Fiber reinforced polymer (FRP) composites are being developed as alternatives to metals for structural orthopedic implant applications. FRP composite fracture behavior and environmental interactions are distinctly different from those which occur in metals. These differences must be accounted for in the design and evaluation of implant performance. Fiber/matrix interfacial bond strength in a FRP composite is known to strongly influence fracture behavior. The interfacial bond strength of four candidate fiber/matrix combinations (carbon fiber/polycarbonate, carbon fiber/polysulfone, polyaramid fiber/polycarbonate, polyaramid fiber/polysulfone) were investigated at 37 degrees C in dry and in vivo simulated (saline, exudate) environments. Ultimate bond strength was measured by a single fiber-microdroplet pull-out test. Dry bond strengths were significantly decreased following exposure to either saline or exudate with bond strength loss being approximately equal in both the saline and exudate. Bond strength loss is attributed to the diffusion of water and/or salt ions into the sample and their interaction with interfacial bonding. Because bond degradation is dependent upon diffusion, diffusional equilibrium must be obtained in composite test samples before the full effect of the test environment upon composite mechanical behavior can be determined.

Water Impact Test and Simulation of a Composite Energy Absorbing Fuselage Section

NASA Technical Reports Server (NTRS)

Fasanella, Edwin L.; Jackson, Karen E.; Sparks, Chad; Sareen, Ashish

2003-01-01

In March 2002, a 25-ft/s vertical drop test of a composite fuselage section was conducted onto water. The purpose of the test was to obtain experimental data characterizing the structural response of the fuselage section during water impact for comparison with two previous drop tests that were performed onto a rigid surface and soft soil. For the drop test, the fuselage section was configured with ten 100-lb. lead masses, five per side, that were attached to seat rails mounted to the floor. The fuselage section was raised to a height of 10-ft. and dropped vertically into a 15-ft. diameter pool filled to a depth of 3.5-ft. with water. Approximately 70 channels of data were collected during the drop test at a 10-kHz sampling rate. The test data were used to validate crash simulations of the water impact that were developed using the nonlinear, explicit transient dynamic codes, MSC.Dytran and LS-DYNA. The fuselage structure was modeled using shell and solid elements with a Lagrangian mesh, and the water was modeled with both Eulerian and Lagrangian techniques. The fluid-structure interactions were executed using the fast general coupling in MSC.Dytran and the Arbitrary Lagrange-Euler (ALE) coupling in LS-DYNA. Additionally, the smooth particle hydrodynamics (SPH) meshless Lagrangian technique was used in LS-DYNA to represent the fluid. The simulation results were correlated with the test data to validate the modeling approach. Additional simulation studies were performed to determine how changes in mesh density, mesh uniformity, fluid viscosity, and failure strain influence the test-analysis correlation.

Aerosol microphysics simulations of the Mt.~Pinatubo eruption with the UM-UKCA composition-climate model

NASA Astrophysics Data System (ADS)

Dhomse, S. S.; Emmerson, K. M.; Mann, G. W.; Bellouin, N.; Carslaw, K. S.; Chipperfield, M. P.; Hommel, R.; Abraham, N. L.; Telford, P.; Braesicke, P.; Dalvi, M.; Johnson, C. E.; O'Connor, F.; Morgenstern, O.; Pyle, J. A.; Deshler, T.; Zawodny, J. M.; Thomason, L. W.

2014-10-01

We use a stratosphere-troposphere composition-climate model with interactive sulfur chemistry and aerosol microphysics, to investigate the effect of the 1991 Mount Pinatubo eruption on stratospheric aerosol properties. Satellite measurements indicate that shortly after the eruption, between 14 and 23 Tg of SO2 (7 to 11.5 Tg of sulfur) was present in the tropical stratosphere. Best estimates of the peak global stratospheric aerosol burden are in the range 19 to 26 Tg, or 3.7 to 6.7 Tg of sulfur assuming a composition of between 59 and 77 % H2SO4. In light of this large uncertainty range, we performed two main simulations with 10 and 20 Tg of SO2 injected into the tropical lower stratosphere. Simulated stratospheric aerosol properties through the 1991 to 1995 period are compared against a range of available satellite and in situ measurements. Stratospheric aerosol optical depth (sAOD) and effective radius from both simulations show good qualitative agreement with the observations, with the timing of peak sAOD and decay timescale matching well with the observations in the tropics and mid-latitudes. However, injecting 20 Tg gives a factor of 2 too high stratospheric aerosol mass burden compared to the satellite data, with consequent strong high biases in simulated sAOD and surface area density, with the 10 Tg injection in much better agreement. Our model cannot explain the large fraction of the injected sulfur that the satellite-derived SO2 and aerosol burdens indicate was removed within the first few months after the eruption. We suggest that either there is an additional alternative loss pathway for the SO2 not included in our model (e.g. via accommodation into ash or ice in the volcanic cloud) or that a larger proportion of the injected sulfur was removed via cross-tropopause transport than in our simulations. We also critically evaluate the simulated evolution of the particle size distribution, comparing in detail to balloon-borne optical particle counter (OPC

Streamlining Software Aspects of Certification: Technical Team Report on the First Industry Workshop

NASA Technical Reports Server (NTRS)

Hayhurst, Kelly J.; Holloway, C. Michael; Knight, John C.; Leveson, Nancy G.; Yang, Jeffrey C.; Dorsey, Cheryl A.; McCormick, G. Frank

1998-01-01

To address concerns about time and expense associated with software aspects of certification, the Federal Aviation Administration (FAA) began the Streamlining Software Aspects of Certification (SSAC) program. As part of this program, a Technical Team was established to determine whether the cost and time associated with certifying aircraft can be reduced while maintaining or improving safety, with the intent of impacting the FAA's Flight 2000 program. The Technical Team conducted a workshop to gain a better understanding of the major concerns in industry about software cost and schedule. Over 120 people attended the workshop, including representatives from the FAA,commercial transport and general aviation aircraft manufacturers and suppliers, and procurers and developers of non-airborne systems; and, more than 200 issues about software aspects of certification were recorded. This paper provides an overview of the SSAC program, motivation for the workshop, details of the workshop activities and outcomes, and recommendations for follow-on work.

Hydrophobic Characteristics of Composite Insulators in Simulated Inland Arid Desert Environment

NASA Astrophysics Data System (ADS)

Khan, Yasin; Al-Arainy, Abdulrehman Ali; Malik, Nazar Hussain; Qureshi, Muhammad Iqbal

2010-06-01

Presently along with traditional insulators i.e. glass and porcelain, etc., the polymeric insulators are also used world widely. These polymeric insulators are very sensitive to various environmental parameters e.g. UV radiations, heat, etc. The UV radiation level in the central region of Saudi Arabia is high as compared to the recommended IEC-61109 standard for the accelerated aging of the composite insulators. In this study, thermoplastic elastomer (TPE) and Ethylene Propylene Diene Monomer (EPDM) insulators were subjected to accelerated aging stress as per IEC standard as well as modified IEC standard simulating the inland arid desert's atmospheric conditions. The hydrophobic characteristics were studied by measuring the contact angle along the insulator surface before and after the accelerated aging of the samples. It was found that TPE loses its hydrophobic properties more as compared to EPDM insulator. This loss was proportional to the intensity of UV irradiation. The rate of recovery is also low for both the tested materials as compared to Silicone Rubber insulators.

P-8A Poseidon strategy for modeling & simulation verification validation & accreditation (VV&A)

NASA Astrophysics Data System (ADS)

Kropp, Derek L.

2009-05-01

One of the first challenges in addressing the need for Modeling & Simulation (M&S) Verification, Validation, & Accreditation (VV&A) is to develop an approach for applying structured and formalized VV&A processes. The P-8A Poseidon Multi-Mission Maritime Aircraft (MMA) Program Modeling and Simulation Accreditation Strategy documents the P-8A program's approach to VV&A. The P-8A strategy tailors a risk-based approach and leverages existing bodies of knowledge, such as the Defense Modeling and Simulation Office Recommended Practice Guide (DMSO RPG), to make the process practical and efficient. As the program progresses, the M&S team must continue to look for ways to streamline the process, add supplemental steps to enhance the process, and identify and overcome procedural, organizational, and cultural challenges. This paper includes some of the basics of the overall strategy, examples of specific approaches that have worked well, and examples of challenges that the M&S team has faced.

Simulation on friction taper plug welding of AA6063-20Gr metal matrix composite

NASA Astrophysics Data System (ADS)

Hynes, N. Rajesh Jesudoss; Nithin, Abeyram M.

2016-05-01

Friction taper plug welding a variant of friction welding is useful in welding of similar and dissimilar materials. It could be used for joining of composites to metals in sophisticated aerospace applications. In the present work numerical simulation of friction taper plug welding process is carried out using finite element based software. Graphite reinforced AA6063 is modelled using the software ANSYS 15.0 and temperature distribution is predicted. Effect of friction time on temperature distribution is numerically investigated. When the friction time is increased to 30 seconds, the tapered part of plug gets detached and fills the hole in the AA6063 plate perfectly.

Simulation of Natural Convection Heat Transfer in an Inclined Square Cavity With Perfectly Conducting Side Walls Using Finite Difference Approach

NASA Astrophysics Data System (ADS)

Azwadi, C. S. Nor; Fairus, M. Y. Mohd

2010-06-01

This study is about numerical simulation of natural heat transfer inside an inclined square cavity with perfectly conducting boundary conditions for the side walls. The Navier Stokes equations were solved using finite difference approach with uniform mesh procedure. Three different inclination angels were applied and the results are presented in terms of streamlines and isotherms plots. Based on the fluid flow pattern and the isothermal lines behaviour, the convection heat transfer has shown domination over the conduction as the tilt angle increases. The simulation of natural convection inside an air filled-tilted cavity is the first time to be done to the best of our knowledge.

Composite load spectra for select space propulsion structural components

NASA Technical Reports Server (NTRS)

Newell, J. F.; Kurth, R. E.; Ho, H.

1991-01-01

The objective of this program is to develop generic load models with multiple levels of progressive sophistication to simulate the composite (combined) load spectra that are induced in space propulsion system components, representative of Space Shuttle Main Engines (SSME), such as transfer ducts, turbine blades, and liquid oxygen posts and system ducting. The first approach will consist of using state of the art probabilistic methods to describe the individual loading conditions and combinations of these loading conditions to synthesize the composite load spectra simulation. The second approach will consist of developing coupled models for composite load spectra simulation which combine the deterministic models for composite load dynamic, acoustic, high pressure, and high rotational speed, etc., load simulation using statistically varying coefficients. These coefficients will then be determined using advanced probabilistic simulation methods with and without strategically selected experimental data.

Experiment and simulation study on unidirectional carbon fiber composite component under dynamic 3 point bending loading

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhou, Guowei; Sun, Qingping; Zeng, Danielle

In current work, unidirectional (UD) carbon fiber composite hatsection component with two different layups are studied under dynamic 3 point bending loading. The experiments are performed at various impact velocities, and the effects of impactor velocity and layup on acceleration histories are compared. A macro model is established with LS-Dyna for more detailed study. The simulation results show that the delamination plays an important role during dynamic 3 point bending test. Based on the analysis with high speed camera, the sidewall of hatsection shows significant buckling rather than failure. Without considering the delamination, current material model cannot capture the postmore » failure phenomenon correctly. The sidewall delamination is modeled by assumption of larger failure strain together with slim parameters, and the simulation results of different impact velocities and layups match the experimental results reasonable well.« less

Numerical simulation and experimental validation of the large deformation bending and folding behavior of magneto-active elastomer composites

NASA Astrophysics Data System (ADS)

Sheridan, Robert; Roche, Juan; Lofland, Samuel E.; vonLockette, Paris R.

2014-09-01

This work seeks to provide a framework for the numerical simulation of magneto-active elastomer (MAE) composite structures for use in origami engineering applications. The emerging field of origami engineering employs folding techniques, an array of crease patterns traditionally on a single flat sheet of paper, to produce structures and devices that perform useful engineering operations. Effective means of numerical simulation offer an efficient way to optimize the crease patterns while coupling to the performance and behavior of the active material. The MAE materials used herein are comprised of nominally 30% v/v, 325 mesh barium hexafarrite particles embedded in Dow HS II silicone elastomer compound. These particulate composites are cured in a magnetic field to produce magneto-elastic solids with anisotropic magnetization, e.g. they have a preferred magnetic axis parallel to the curing axis. The deformed shape and/or blocked force characteristics of these MAEs are examined in three geometries: a monolithic cantilever as well as two- and four-segment composite accordion structures. In the accordion structures, patches of MAE material are bonded to a Gelest OE41 unfilled silicone elastomer substrate. Two methods of simulation, one using the Maxwell stress tensor applied as a traction boundary condition and another employing a minimum energy kinematic (MEK) model, are investigated. Both methods capture actuation due to magnetic torque mechanisms that dominate MAE behavior. Comparison with experimental data show good agreement with only a single adjustable parameter, either an effective constant magnetization of the MAE material in the finite element models (at small and moderate deformations) or an effective modulus in the minimum energy model. The four-segment finite element model was prone to numerical locking at large deformation. The effective magnetization and modulus values required are a fraction of the actual experimentally measured values which suggests a

SmaggIce 2D Version 1.8: Software Toolkit Developed for Aerodynamic Simulation Over Iced Airfoils

NASA Technical Reports Server (NTRS)

Choo, Yung K.; Vickerman, Mary B.

2005-01-01

SmaggIce 2D version 1.8 is a software toolkit developed at the NASA Glenn Research Center that consists of tools for modeling the geometry of and generating the grids for clean and iced airfoils. Plans call for the completed SmaggIce 2D version 2.0 to streamline the entire aerodynamic simulation process--the characterization and modeling of ice shapes, grid generation, and flow simulation--and to be closely coupled with the public-domain application flow solver, WIND. Grid generated using version 1.8, however, can be used by other flow solvers. SmaggIce 2D will help researchers and engineers study the effects of ice accretion on airfoil performance, which is difficult to do with existing software tools because of complex ice shapes. Using SmaggIce 2D, when fully developed, to simulate flow over an iced airfoil will help to reduce the cost of performing flight and wind-tunnel tests for certifying aircraft in natural and simulated icing conditions.

Damage Progression in Bolted Composites

NASA Technical Reports Server (NTRS)

Minnetyan, Levon; Chamis, Christos C.; Gotsis, Pascal K.

1998-01-01

Structural durability, damage tolerance, and progressive fracture characteristics of bolted graphite/epoxy composite laminates are evaluated via computational simulation. Constituent material properties and stress and strain limits are scaled up to the structure level to evaluate the overall damage and fracture propagation for bolted composites. Single and double bolted composite specimens with various widths and bolt spacings are evaluated. The effect of bolt spacing is investigated with regard to the structural durability of a bolted joint. Damage initiation, growth, accumulation, and propagation to fracture are included in the simulations. Results show the damage progression sequence and structural fracture resistance during different degradation stages. A procedure is outlined for the use of computational simulation data in the assessment of damage tolerance, determination of sensitive parameters affecting fracture, and interpretation of experimental results with insight for design decisions.

Damage Progression in Bolted Composites

NASA Technical Reports Server (NTRS)

Minnetyan, Levon; Chamis, Christos; Gotsis, Pascal K.

1998-01-01

Structural durability,damage tolerance,and progressive fracture characteristics of bolted graphite/epoxy composite laminates are evaluated via computational simulation. Constituent material properties and stress and strain limits are scaled up to the structure level to evaluate the overall damage and fracture propagation for bolted composites. Single and double bolted composite specimens with various widths and bolt spacings are evaluated. The effect of bolt spacing is investigated with regard to the structural durability of a bolted joint. Damage initiation, growth, accumulation, and propagation to fracture are included in the simulations. Results show the damage progression sequence and structural fracture resistance during different degradation stages. A procedure is outlined for the use of computational simulation data in the assessment of damage tolerance, determination of sensitive parameters affecting fracture, and interpretation of experimental results with insight for design decisions.

Structural Durability of Damaged Metallic Panel Repaired with Composite Patches

NASA Technical Reports Server (NTRS)

Minnetyan, Levon; Chamis, Christos C.

1997-01-01

Structural durability/damage tolerance characteristics of an aluminum tension specimen possessing a short crack and repaired by applying a fiber composite surface patch is investigated via computational simulation. The composite patch is made of graphite/epoxy plies with various layups. An integrated computer code that accounts for all possible failure modes is utilized for the simulation of combined fiber-composite/aluminum structural degradation under loading. Damage initiation, growth, accumulation, and propagation to structural fracture are included in the simulation. Results show the structural degradation stages due to tensile loading and illustrate the use of computational simulation for the investigation of a composite patch repaired cracked metallic panel.

An N-body Integrator for Planetary Rings