A review of analogue modelling of geodynamic processes: Approaches, scaling, materials and quantification, with an application to subduction experiments

NASA Astrophysics Data System (ADS)

Schellart, Wouter P.; Strak, Vincent

2016-10-01

We present a review of the analogue modelling method, which has been used for 200 years, and continues to be used, to investigate geological phenomena and geodynamic processes. We particularly focus on the following four components: (1) the different fundamental modelling approaches that exist in analogue modelling; (2) the scaling theory and scaling of topography; (3) the different materials and rheologies that are used to simulate the complex behaviour of rocks; and (4) a range of recording techniques that are used for qualitative and quantitative analyses and interpretations of analogue models. Furthermore, we apply these four components to laboratory-based subduction models and describe some of the issues at hand with modelling such systems. Over the last 200 years, a wide variety of analogue materials have been used with different rheologies, including viscous materials (e.g. syrups, silicones, water), brittle materials (e.g. granular materials such as sand, microspheres and sugar), plastic materials (e.g. plasticine), visco-plastic materials (e.g. paraffin, waxes, petrolatum) and visco-elasto-plastic materials (e.g. hydrocarbon compounds and gelatins). These materials have been used in many different set-ups to study processes from the microscale, such as porphyroclast rotation, to the mantle scale, such as subduction and mantle convection. Despite the wide variety of modelling materials and great diversity in model set-ups and processes investigated, all laboratory experiments can be classified into one of three different categories based on three fundamental modelling approaches that have been used in analogue modelling: (1) The external approach, (2) the combined (external + internal) approach, and (3) the internal approach. In the external approach and combined approach, energy is added to the experimental system through the external application of a velocity, temperature gradient or a material influx (or a combination thereof), and so the system is open. In the external approach, all deformation in the system is driven by the externally imposed condition, while in the combined approach, part of the deformation is driven by buoyancy forces internal to the system. In the internal approach, all deformation is driven by buoyancy forces internal to the system and so the system is closed and no energy is added during an experimental run. In the combined approach, the externally imposed force or added energy is generally not quantified nor compared to the internal buoyancy force or potential energy of the system, and so it is not known if these experiments are properly scaled with respect to nature. The scaling theory requires that analogue models are geometrically, kinematically and dynamically similar to the natural prototype. Direct scaling of topography in laboratory models indicates that it is often significantly exaggerated. This can be ascribed to (1) The lack of isostatic compensation, which causes topography to be too high. (2) The lack of erosion, which causes topography to be too high. (3) The incorrect scaling of topography when density contrasts are scaled (rather than densities); In isostatically supported models, scaling of density contrasts requires an adjustment of the scaled topography by applying a topographic correction factor. (4) The incorrect scaling of externally imposed boundary conditions in isostatically supported experiments using the combined approach; When externally imposed forces are too high, this creates topography that is too high. Other processes that also affect surface topography in laboratory models but not in nature (or only in a negligible way) include surface tension (for models using fluids) and shear zone dilatation (for models using granular material), but these will generally only affect the model surface topography on relatively short horizontal length scales of the order of several mm across material boundaries and shear zones, respectively.

Material point method modeling in oil and gas reservoirs

DOEpatents

Vanderheyden, William Brian; Zhang, Duan

2016-06-28

A computer system and method of simulating the behavior of an oil and gas reservoir including changes in the margins of frangible solids. A system of equations including state equations such as momentum, and conservation laws such as mass conservation and volume fraction continuity, are defined and discretized for at least two phases in a modeled volume, one of which corresponds to frangible material. A material point model technique for numerically solving the system of discretized equations, to derive fluid flow at each of a plurality of mesh nodes in the modeled volume, and the velocity of at each of a plurality of particles representing the frangible material in the modeled volume. A time-splitting technique improves the computational efficiency of the simulation while maintaining accuracy on the deformation scale. The method can be applied to derive accurate upscaled model equations for larger volume scale simulations.

Modeling and validation of spectral BRDF on material surface of space target

NASA Astrophysics Data System (ADS)

Hou, Qingyu; Zhi, Xiyang; Zhang, Huili; Zhang, Wei

2014-11-01

The modeling and the validation methods of the spectral BRDF on the material surface of space target were presented. First, the microscopic characteristics of the space targets' material surface were analyzed based on fiber-optic spectrometer using to measure the direction reflectivity of the typical materials surface. To determine the material surface of space target is isotropic, atomic force microscopy was used to measure the material surface structure of space target and obtain Gaussian distribution model of microscopic surface element height. Then, the spectral BRDF model based on that the characteristics of the material surface were isotropic and the surface micro-facet with the Gaussian distribution which we obtained was constructed. The model characterizes smooth and rough surface well for describing the material surface of the space target appropriately. Finally, a spectral BRDF measurement platform in a laboratory was set up, which contains tungsten halogen lamp lighting system, fiber optic spectrometer detection system and measuring mechanical systems with controlling the entire experimental measurement and collecting measurement data by computers automatically. Yellow thermal control material and solar cell were measured with the spectral BRDF, which showed the relationship between the reflection angle and BRDF values at three wavelengths in 380nm, 550nm, 780nm, and the difference between theoretical model values and the measured data was evaluated by relative RMS error. Data analysis shows that the relative RMS error is less than 6%, which verified the correctness of the spectral BRDF model.

Development and Validation of a Slurry Model for Chemical Hydrogen Storage in Fuel Cell Applications

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

Brooks, Kriston P.; Pires, Richard P.; Simmons, Kevin L.

2014-07-25

The US Department of Energy's (DOE) Hydrogen Storage Engineering Center of Excellence (HSECoE) is developing models for hydrogen storage systems for fuel cell-based light duty vehicle applications for a variety of promising materials. These transient models simulate the performance of the storage system for comparison to the DOE’s Technical Targets and a set of four drive cycles. The purpose of this research is to describe the models developed for slurry-based chemical hydrogen storage materials. The storage systems of both a representative exothermic system based on ammonia borane and endothermic system based on alane were developed and modeled in Simulink®. Oncemore » complete the reactor and radiator components of the model were validated with experimental data. The model was then run using a highway cycle, an aggressive cycle, cold-start cycle and hot drive cycle. The system design was adjusted to meet these drive cycles. A sensitivity analysis was then performed to identify the range of material properties where these DOE targets and drive cycles could be met. Materials with a heat of reaction greater than 11 kJ/mol H2 generated and a slurry hydrogen capacity of greater than 11.4% will meet the on-board efficiency and gravimetric capacity targets, respectively.« less

A computer simulation of the turbocharged turbo compounded diesel engine system: A description of the thermodynamic and heat transfer models

NASA Technical Reports Server (NTRS)

Assanis, D. N.; Ekchian, J. E.; Frank, R. M.; Heywood, J. B.

1985-01-01

A computer simulation of the turbocharged turbocompounded direct-injection diesel engine system was developed in order to study the performance characteristics of the total system as major design parameters and materials are varied. Quasi-steady flow models of the compressor, turbines, manifolds, intercooler, and ducting are coupled with a multicylinder reciprocator diesel model, where each cylinder undergoes the same thermodynamic cycle. The master cylinder model describes the reciprocator intake, compression, combustion and exhaust processes in sufficient detail to define the mass and energy transfers in each subsystem of the total engine system. Appropriate thermal loading models relate the heat flow through critical system components to material properties and design details. From this information, the simulation predicts the performance gains, and assesses the system design trade-offs which would result from the introduction of selected heat transfer reduction materials in key system components, over a range of operating conditions.

Statistical distribution of mechanical properties for three graphite-epoxy material systems

NASA Technical Reports Server (NTRS)

Reese, C.; Sorem, J., Jr.

1981-01-01

Graphite-epoxy composites are playing an increasing role as viable alternative materials in structural applications necessitating thorough investigation into the predictability and reproducibility of their material strength properties. This investigation was concerned with tension, compression, and short beam shear coupon testing of large samples from three different material suppliers to determine their statistical strength behavior. Statistical results indicate that a two Parameter Weibull distribution model provides better overall characterization of material behavior for the graphite-epoxy systems tested than does the standard Normal distribution model that is employed for most design work. While either a Weibull or Normal distribution model provides adequate predictions for average strength values, the Weibull model provides better characterization in the lower tail region where the predictions are of maximum design interest. The two sets of the same material were found to have essentially the same material properties, and indicate that repeatability can be achieved.

Force Project Technology Presentation to the NRCC

DTIC Science & Technology

2014-02-04

Functional Bridge components Smart Odometer Adv Pretreatment Smart Bridge Multi-functional Gap Crossing Fuel Automated Tracking System Adv...comprehensive matrix of candidate composite material systems and textile reinforcement architectures via modeling/analyses and testing. Product(s...Validated Dynamic Modeling tool based on parametric study using material models to reliably predict the textile mechanics of the hose

In-space production of large space systems from extraterrestrial materials: A program implementation model

NASA Technical Reports Server (NTRS)

Vontiesenhausen, G. F.

1977-01-01

A program implementation model is presented which covers the in-space construction of certain large space systems from extraterrestrial materials. The model includes descriptions of major program elements and subelements and their operational requirements and technology readiness requirements. It provides a structure for future analysis and development.

Physics and Process Modeling (PPM) and Other Propulsion R and T. Volume 1; Materials Processing, Characterization, and Modeling; Lifting Models

NASA Technical Reports Server (NTRS)

1997-01-01

This CP contains the extended abstracts and presentation figures of 36 papers presented at the PPM and Other Propulsion R&T Conference. The focus of the research described in these presentations is on materials and structures technologies that are parts of the various projects within the NASA Aeronautics Propulsion Systems Research and Technology Base Program. These projects include Physics and Process Modeling; Smart, Green Engine; Fast, Quiet Engine; High Temperature Engine Materials Program; and Hybrid Hyperspeed Propulsion. Also presented were research results from the Rotorcraft Systems Program and work supported by the NASA Lewis Director's Discretionary Fund. Authors from NASA Lewis Research Center, industry, and universities conducted research in the following areas: material processing, material characterization, modeling, life, applied life models, design techniques, vibration control, mechanical components, and tribology. Key issues, research accomplishments, and future directions are summarized in this publication.

Advances In High Temperature (Viscoelastoplastic) Material Modeling for Thermal Structural Analysis

NASA Technical Reports Server (NTRS)

Arnold, Steven M.; Saleeb, Atef F.

2005-01-01

Typical High Temperature Applications High Temperature Applications Demand High Performance Materials: 1) Complex Thermomechanical Loading; 2) Complex Material response requires Time-Dependent/Hereditary Models: Viscoelastic/Viscoplastic; and 3) Comprehensive Characterization (Tensile, Creep, Relaxation) for a variety of material systems.

Toward a space materials systems program

NASA Technical Reports Server (NTRS)

Vontiesenhausen, G. F.

1981-01-01

A program implementation model is presented which covers the early stages of space material processing and manufacturing. The model includes descriptions of major program elements, development and experiment requirements in space materials processing and manufacturing, and an integration of the model into NASA's long range plans as well as its evolution from present Materials Processing in Space plans.

Effect of metal shielding on a wireless power transfer system

NASA Astrophysics Data System (ADS)

Li, Jiacheng; Huang, Xueliang; Chen, Chen; Tan, Linlin; Wang, Wei; Guo, Jinpeng

2017-05-01

In this paper, the effect of non-ferromagnetic metal shielding (NFMS) material on the resonator of wireless power transfer (WPT) is studied by modeling, simulation and experimental analysis. And, the effect of NFMS material on the power transfer efficiency (PTE) of WPT systems is investigated by circuit model. Meanwhile, the effect of ferromagnetic metal shielding material on the PTE of WPT systems is analyzed through simulation. A double layer metal shield structure is designed. Experimental results demonstrate that by applying the novel double layer metal shielding method, the system PTE increases significantly while the electromagnetic field of WPT systems declines dramatically.

Multiscale Materials Modeling in an Industrial Environment.

PubMed

Weiß, Horst; Deglmann, Peter; In 't Veld, Pieter J; Cetinkaya, Murat; Schreiner, Eduard

2016-06-07

In this review, we sketch the materials modeling process in industry. We show that predictive and fast modeling is a prerequisite for successful participation in research and development processes in the chemical industry. Stable and highly automated workflows suitable for handling complex systems are a must. In particular, we review approaches to build and parameterize soft matter systems. By satisfying these prerequisites, efficiency for the development of new materials can be significantly improved, as exemplified here for formulation polymer development. This is in fact in line with recent Materials Genome Initiative efforts sponsored by the US government. Valuable contributions to product development are possible today by combining existing modeling techniques in an intelligent fashion, provided modeling and experiment work hand in hand.

Quantum Impurity Models as Reference Systems for Strongly Correlated Materials: The Road from the Kondo Impurity Model to First Principles Electronic Structure Calculations with Dynamical Mean-Field Theory

NASA Astrophysics Data System (ADS)

Kotliar, Gabriel

2005-01-01

Dynamical mean field theory (DMFT) relates extended systems (bulk solids, surfaces and interfaces) to quantum impurity models (QIM) satisfying a self-consistency condition. This mapping provides an economic description of correlated electron materials. It is currently used in practical computations of physical properties of real materials. It has also great conceptual value, providing a simple picture of correlated electron phenomena on the lattice, using concepts derived from quantum impurity models such as the Kondo effect. DMFT can also be formulated as a first principles electronic structure method and is applicable to correlated materials.

Code System to Calculate Tornado-Induced Flow Material Transport.

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

ANDRAE, R. W.

1999-11-18

Version: 00 TORAC models tornado-induced flows, pressures, and material transport within structures. Its use is directed toward nuclear fuel cycle facilities and their primary release pathway, the ventilation system. However, it is applicable to other structures and can model other airflow pathways within a facility. In a nuclear facility, this network system could include process cells, canyons, laboratory offices, corridors, and offgas systems. TORAC predicts flow through a network system that also includes ventilation system components such as filters, dampers, ducts, and blowers. These ventilation system components are connected to the rooms and corridors of the facility to form amore » complete network for moving air through the structure and, perhaps, maintaining pressure levels in certain areas. The material transport capability in TORAC is very basic and includes convection, depletion, entrainment, and filtration of material.« less

Illicit drug detection using energy dispersive x-ray diffraction

NASA Astrophysics Data System (ADS)

Cook, E. J.; Griffiths, J. A.; Koutalonis, M.; Gent, C.; Pani, S.; Horrocks, J. A.; George, L.; Hardwick, S.; Speller, R.

2009-05-01

Illicit drugs are imported into countries in myriad ways, including via the postal system and courier services. An automated system is required to detect drugs in parcels for which X-ray diffraction is a suitable technique as it is non-destructive, material specific and uses X-rays of sufficiently high energy to penetrate parcels containing a range of attenuating materials. A database has been constructed containing the measured powder diffraction profiles of several thousand materials likely to be found in parcels. These include drugs, cutting agents, packaging and other innocuous materials. A software model has been developed using these data to predict the diffraction profiles which would be obtained by X-ray diffraction systems with a range of suggested detector (high purity germanium, CZT and scintillation), source and collimation options. The aim of the model was to identify the most promising system geometries, which was done with the aid of multivariate analysis (MVA). The most promising systems were constructed and tested. The diffraction profiles of a range of materials have been measured and used to both validate the model and to identify the presence of drugs in sample packages.

MHSS: a material handling system simulator

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

Pomernacki, L.; Hollstien, R.B.

1976-04-07

A Material Handling System Simulator (MHSS) program is described that provides specialized functional blocks for modeling and simulation of nuclear material handling systems. Models of nuclear fuel fabrication plants may be built using functional blocks that simulate material receiving, storage, transport, inventory, processing, and shipping operations as well as the control and reporting tasks of operators or on-line computers. Blocks are also provided that allow the user to observe and gather statistical information on the dynamic behavior of simulated plants over single or replicated runs. Although it is currently being developed for the nuclear materials handling application, MHSS can bemore » adapted to other industries in which material accountability is important. In this paper, emphasis is on the simulation methodology of the MHSS program with application to the nuclear material safeguards problem. (auth)« less

Wellbore Seal Repair Using Nanocomposite Materials

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

Stormont, John

2016-08-31

Nanocomposite wellbore repair materials have been developed, tested, and modeled through an integrated program of laboratory testing and numerical modeling. Numerous polymer-cement nanocomposites were synthesized as candidate wellbore repair materials using various combinations of base polymers and nanoparticles. Based on tests of bond strength to steel and cement, ductility, stability, flowability, and penetrability in opening of 50 microns and less, we identified Novolac epoxy reinforced with multi-walled carbon nanotubes and/or alumina nanoparticles to be a superior wellbore seal material compared to conventional microfine cements. A system was developed for testing damaged and repaired wellbore specimens comprised of a cement sheathmore » cast on a steel casing. The system allows independent application of confining pressures and casing pressures while gas flow is measured through the specimens along the wellbore axis. Repair with the nanocomposite epoxy base material was successful in dramatically reducing the flow through flaws of various sizes and types, and restoring the specimen comparable to an intact condition. In contrast, repair of damaged specimens with microfine cement was less effective, and the repair degraded with application of stress. Post-test observations confirm the complete penetration and sealing of flaws using the nanocomposite epoxy base material. A number of modeling efforts have supported the material development and testing efforts. We have modeled the steel-repair material interface behavior in detail during slant shear tests, which we used to characterize bond strength of candidate repair materials. A numerical model of the laboratory testing of damaged wellbore specimens was developed. This investigation found that microannulus permeability can satisfactorily be described by a joint model. Finally, a wellbore model has been developed that can be used to evaluate the response of the wellbore system (casing, cement, and microannulus), including the use of either cement or a nanocomposite in the microannulus to represent a repaired system. This wellbore model was successfully coupled with a field-scale model of CO 2 injection, to enable predictions of stress and strains in the wellbore subjected to subsurface changes (i.e. domal uplift) associated with fluid injection.« less

Teaching RFID Information Systems Security

ERIC Educational Resources Information Center

Thompson, Dale R.; Di, Jia; Daugherty, Michael K.

2014-01-01

The future cyber security workforce needs radio frequency identification (RFID) information systems security (INFOSEC) and threat modeling educational materials. A complete RFID security course with new learning materials and teaching strategies is presented here. A new RFID Reference Model is used in the course to organize discussion of RFID,…

A hydrodynamic model for granular material flows including segregation effects

NASA Astrophysics Data System (ADS)

Gilberg, Dominik; Klar, Axel; Steiner, Konrad

2017-06-01

The simulation of granular flows including segregation effects in large industrial processes using particle methods is accurate, but very time-consuming. To overcome the long computation times a macroscopic model is a natural choice. Therefore, we couple a mixture theory based segregation model to a hydrodynamic model of Navier-Stokes-type, describing the flow behavior of the granular material. The granular flow model is a hybrid model derived from kinetic theory and a soil mechanical approach to cover the regime of fast dilute flow, as well as slow dense flow, where the density of the granular material is close to the maximum packing density. Originally, the segregation model has been formulated by Thornton and Gray for idealized avalanches. It is modified and adapted to be in the preferred form for the coupling. In the final coupled model the segregation process depends on the local state of the granular system. On the other hand, the granular system changes as differently mixed regions of the granular material differ i.e. in the packing density. For the modeling process the focus lies on dry granular material flows of two particle types differing only in size but can be easily extended to arbitrary granular mixtures of different particle size and density. To solve the coupled system a finite volume approach is used. To test the model the rotational mixing of small and large particles in a tumbler is simulated.

An Evaluation Research Model for System-Wide Textbook Selection.

ERIC Educational Resources Information Center

Talmage, Harriet; Walberg, Herbert T.

One component of an evaluation research model for system-wide selection of curriculum materials is reported: implementation of an evaluation design for obtaining data that permits professional and lay persons to base curriculum materials decisions on a "best fit" principle. The design includes teacher characteristics, learning environment…

Optimization of Regenerators for AMRR Systems

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

Nellis, Gregory; Klein, Sanford; Brey, William

Active Magnetic Regenerative Refrigeration (AMRR) systems have no direct global warming potential or ozone depletion potential and hold the potential for providing refrigeration with efficiencies that are equal to or greater than the vapor compression systems used today. The work carried out in this project has developed and improved modeling tools that can be used to optimize and evaluate the magnetocaloric materials and geometric structure of the regenerator beds required for AMRR Systems. There has been an explosion in the development of magnetocaloric materials for AMRR systems over the past few decades. The most attractive materials, based on the magnitudemore » of the measured magnetocaloric effect, tend to also have large amounts of hysteresis. This project has provided for the first time a thermodynamically consistent method for evaluating these hysteretic materials in the context of an AMRR cycle. An additional, practical challenge that has been identified for AMRR systems is related to the participation of the regenerator wall in the cyclic process. The impact of housing heat capacity on both passive and active regenerative systems has been studied and clarified within this project. This report is divided into two parts corresponding to these two efforts. Part 1 describes the work related to modeling magnetic hysteresis while Part 2 discusses the modeling of the heat capacity of the housing. A key outcome of this project is the development of a publically available modeling tool that allows researchers to identify a truly optimal magnetocaloric refrigerant. Typically, the refrigeration potential of a magnetocaloric material is judged entirely based on the magnitude of the magnetocaloric effect and other properties of the material that are deemed unimportant. This project has shown that a material with a large magnetocaloric effect (as evidenced, for example, by a large adiabatic temperature change) may not be optimal when it is accompanied by a large hysteresis. The trade-off between these various material properties and the proper design of an AMRR system can only be evaluated correctly using the comprehensive, physics-based model developed by this project. The development of these modeling tools and optimization studies will provide the knowledge base that is required to achieve transformational discoveries. The widespread adoption of AMRR technology will change the character of energy demand in this country and provide manufacturing jobs as well as employment associated with retrofitting existing HVAC&R applications.« less

Probabilistic material degradation model for aerospace materials subjected to high temperature, mechanical and thermal fatigue, and creep

NASA Technical Reports Server (NTRS)

Boyce, L.

1992-01-01

A probabilistic general material strength degradation model has been developed for structural components of aerospace propulsion systems subjected to diverse random effects. The model has been implemented in two FORTRAN programs, PROMISS (Probabilistic Material Strength Simulator) and PROMISC (Probabilistic Material Strength Calibrator). PROMISS calculates the random lifetime strength of an aerospace propulsion component due to as many as eighteen diverse random effects. Results are presented in the form of probability density functions and cumulative distribution functions of lifetime strength. PROMISC calibrates the model by calculating the values of empirical material constants.

Statistical Models of Fracture Relevant to Nuclear-Grade Graphite: Review and Recommendations

NASA Technical Reports Server (NTRS)

Nemeth, Noel N.; Bratton, Robert L.

2011-01-01

The nuclear-grade (low-impurity) graphite needed for the fuel element and moderator material for next-generation (Gen IV) reactors displays large scatter in strength and a nonlinear stress-strain response from damage accumulation. This response can be characterized as quasi-brittle. In this expanded review, relevant statistical failure models for various brittle and quasi-brittle material systems are discussed with regard to strength distribution, size effect, multiaxial strength, and damage accumulation. This includes descriptions of the Weibull, Batdorf, and Burchell models as well as models that describe the strength response of composite materials, which involves distributed damage. Results from lattice simulations are included for a physics-based description of material breakdown. Consideration is given to the predicted transition between brittle and quasi-brittle damage behavior versus the density of damage (level of disorder) within the material system. The literature indicates that weakest-link-based failure modeling approaches appear to be reasonably robust in that they can be applied to materials that display distributed damage, provided that the level of disorder in the material is not too large. The Weibull distribution is argued to be the most appropriate statistical distribution to model the stochastic-strength response of graphite.

Analysis of material flow in a utillzation technology of low grade manganese ore and sulphur coal complementary

NASA Astrophysics Data System (ADS)

Wang, Bo-Zhi; Deng, Biao; Su, Shi-Jun; Ding, Sang-Lan; Sun, Wei-Yi

2018-03-01

Electrolytic manganese is conventionally produced through low-grade manganese ore leaching in SO2, with the combustion of high sulfur coal. Subsequently the coal ash and manganese slag, produced by the combustion of high sulfur coal and preparation of electrolytic manganese, can be used as raw ingredients for the preparation of sulphoaluminate cement. In order to realize the `coal-electricity-sulfur-manganese-building material' system of complementary resource utilization, the conditions of material inflow and outflow in each process were determined using material flow analysis. The material flow models in each unit and process can be obtained by analyzed of material flow for new technology, and the input-output model could be obtained. Through the model, it is possible to obtain the quantity of all the input and output material in the condition of limiting the quantity of a substance. Taking one ton electrolytic manganese as a basis, the quantity of other input material and cements can be determined with the input-output model. The whole system had thusly achieved a cleaner production level. Therefore, the input-output model can be used for guidance in practical production.

Development of a Three-Dimensional, Unstructured Material Response Design Tool

NASA Technical Reports Server (NTRS)

Schulz, Joseph C.; Stern, Eric C.; Muppidi, Suman; Palmer, Grant E.; Schroeder, Olivia

2017-01-01

A preliminary verification and validation of a new material response model is presented. This model, Icarus, is intended to serve as a design tool for the thermal protection systems of re-entry vehicles. Currently, the capability of the model is limited to simulating the pyrolysis of a material as a result of the radiative and convective surface heating imposed on the material from the surrounding high enthalpy gas. Since the major focus behind the development of Icarus has been model extensibility, the hope is that additional physics can be quickly added. This extensibility is critical since thermal protection systems are becoming increasing complex, e.g. woven carbon polymers. Additionally, as a three-dimensional, unstructured, finite-volume model, Icarus is capable of modeling complex geometries. In this paper, the mathematical and numerical formulation is presented followed by a discussion of the software architecture and some preliminary verification and validation studies.

Bite force measurement system using pressure-sensitive sheet and silicone impression material.

PubMed

Ando, Katsuya; Fuwa, Yuji; Kurosawa, Masahiro; Kondo, Takamasa; Goto, Shigemi

2009-03-01

This study was conducted to reduce the bias in measured values caused by the thickness of materials used in occlusal examinations. To this end, a silicone impression material for bite force measurement and an experimental model of a simplified stomatognathic system were employed in this study. By means of this experimental model, results showed that the effect of bias toward the posterior arch could be reduced in the anterior-posterior distribution of bite forces and in the occlusal contact areas due to the thickness of the materials used in occlusal examinations.

Designing Business System Model using System Modeling Approach to the Small and Medium Enterprises (SME) of Furniture in Indonesia

NASA Astrophysics Data System (ADS)

Sukendar, Irwan; Fatmawati, Wiwiek; Much Ibnu Subroto, Imam; Arigama, Rizki

2017-04-01

This paper studies the design of business system model with System Modeling Approach on small and medium enterprises (SMEs) of furniture. Methods used consists of five phases: phase of identification of business processes actual on SMEs of Furniture, phase of identification of deficiencies and improvement of business processes, phase of design algorithm and flowchart business processes, phase of analysis of the elements of the system, and phase of the design of data flow diagram (DFD), The results of the analysis of the elements of the system are: Products and quantities ordered product consumers and DP paid by consumers identified as elements of system inputs 1,2 and 3. The result of the calculation, payment slips and mail order (SO) are identified as elements of system output 1, 2 and 3. Acceptance of orders, stocks checking of raw materials at the warehouse, calculating raw material requirements, adequacy of raw materials, the price of the contract, and the due date, as well as the submission of the results of calculations to consumers were identified as elements of system components 1, 2, 3, and 4. Admin taking orders, Admin check stocks of raw materials at the warehouse, Admin making calculation, and Admin convey the results of calculations to consumers were identified as an element of interaction system 1, 2, 3, and 4. Consumers were identified as element of environmental systems. Moreover, the boundary between SMEs and consumers were identified as elements of the system boundary.

A hybrid modeling system designed to support decision making in the optimization of extrusion of inhomogeneous materials

NASA Astrophysics Data System (ADS)

Kryuchkov, D. I.; Zalazinsky, A. G.

2017-12-01

Mathematical models and a hybrid modeling system are developed for the implementation of the experimental-calculation method for the engineering analysis and optimization of the plastic deformation of inhomogeneous materials with the purpose of improving metal-forming processes and machines. The created software solution integrates Abaqus/CAE, a subroutine for mathematical data processing, with the use of Python libraries and the knowledge base. Practical application of the software solution is exemplified by modeling the process of extrusion of a bimetallic billet. The results of the engineering analysis and optimization of the extrusion process are shown, the material damage being monitored.

Energy Finite Element Analysis Developments for Vibration Analysis of Composite Aircraft Structures

NASA Technical Reports Server (NTRS)

Vlahopoulos, Nickolas; Schiller, Noah H.

2011-01-01

The Energy Finite Element Analysis (EFEA) has been utilized successfully for modeling complex structural-acoustic systems with isotropic structural material properties. In this paper, a formulation for modeling structures made out of composite materials is presented. An approach based on spectral finite element analysis is utilized first for developing the equivalent material properties for the composite material. These equivalent properties are employed in the EFEA governing differential equations for representing the composite materials and deriving the element level matrices. The power transmission characteristics at connections between members made out of non-isotropic composite material are considered for deriving suitable power transmission coefficients at junctions of interconnected members. These coefficients are utilized for computing the joint matrix that is needed to assemble the global system of EFEA equations. The global system of EFEA equations is solved numerically and the vibration levels within the entire system can be computed. The new EFEA formulation for modeling composite laminate structures is validated through comparison to test data collected from a representative composite aircraft fuselage that is made out of a composite outer shell and composite frames and stiffeners. NASA Langley constructed the composite cylinder and conducted the test measurements utilized in this work.

Multiscale Modeling, Simulation and Visualization and Their Potential for Future Aerospace Systems

NASA Technical Reports Server (NTRS)

Noor, Ahmed K. (Compiler)

2002-01-01

This document contains the proceedings of the Training Workshop on Multiscale Modeling, Simulation and Visualization and Their Potential for Future Aerospace Systems held at NASA Langley Research Center, Hampton, Virginia, March 5 - 6, 2002. The workshop was jointly sponsored by Old Dominion University's Center for Advanced Engineering Environments and NASA. Workshop attendees were from NASA, other government agencies, industry, and universities. The objectives of the workshop were to give overviews of the diverse activities in hierarchical approach to material modeling from continuum to atomistics; applications of multiscale modeling to advanced and improved material synthesis; defects, dislocations, and material deformation; fracture and friction; thin-film growth; characterization at nano and micro scales; and, verification and validation of numerical simulations, and to identify their potential for future aerospace systems.

An experimental comparison of several current viscoplastic constitutive models at elevated temperature

NASA Technical Reports Server (NTRS)

James, G. H.; Imbrie, P. K.; Hill, P. S.; Allen, D. H.; Haisler, W. E.

1988-01-01

Four current viscoplastic models are compared experimentally for Inconel 718 at 593 C. This material system responds with apparent negative strain rate sensitivity, undergoes cyclic work softening, and is susceptible to low cycle fatigue. A series of tests were performed to create a data base from which to evaluate material constants. A method to evaluate the constants is developed which draws on common assumptions for this type of material, recent advances by other researchers, and iterative techniques. A complex history test, not used in calculating the constants, is then used to compare the predictive capabilities of the models. The combination of exponentially based inelastic strain rate equations and dynamic recovery is shown to model this material system with the greatest success. The method of constant calculation developed was successfully applied to the complex material response encountered. Backstress measuring tests were found to be invaluable and to warrant further development.

Coal conversion systems design and process modeling. Volume 1: Application of MPPR and Aspen computer models

NASA Technical Reports Server (NTRS)

1981-01-01

The development of a coal gasification system design and mass and energy balance simulation program for the TVA and other similar facilities is described. The materials-process-product model (MPPM) and the advanced system for process engineering (ASPEN) computer program were selected from available steady state and dynamic models. The MPPM was selected to serve as the basis for development of system level design model structure because it provided the capability for process block material and energy balance and high-level systems sizing and costing. The ASPEN simulation serves as the basis for assessing detailed component models for the system design modeling program. The ASPEN components were analyzed to identify particular process blocks and data packages (physical properties) which could be extracted and used in the system design modeling program. While ASPEN physical properties calculation routines are capable of generating physical properties required for process simulation, not all required physical property data are available, and must be user-entered.

Stochastic Analysis and Design of Heterogeneous Microstructural Materials System

NASA Astrophysics Data System (ADS)

Xu, Hongyi

Advanced materials system refers to new materials that are comprised of multiple traditional constituents but complex microstructure morphologies, which lead to superior properties over the conventional materials. To accelerate the development of new advanced materials system, the objective of this dissertation is to develop a computational design framework and the associated techniques for design automation of microstructure materials systems, with an emphasis on addressing the uncertainties associated with the heterogeneity of microstructural materials. Five key research tasks are identified: design representation, design evaluation, design synthesis, material informatics and uncertainty quantification. Design representation of microstructure includes statistical characterization and stochastic reconstruction. This dissertation develops a new descriptor-based methodology, which characterizes 2D microstructures using descriptors of composition, dispersion and geometry. Statistics of 3D descriptors are predicted based on 2D information to enable 2D-to-3D reconstruction. An efficient sequential reconstruction algorithm is developed to reconstruct statistically equivalent random 3D digital microstructures. In design evaluation, a stochastic decomposition and reassembly strategy is developed to deal with the high computational costs and uncertainties induced by material heterogeneity. The properties of Representative Volume Elements (RVE) are predicted by stochastically reassembling SVE elements with stochastic properties into a coarse representation of the RVE. In design synthesis, a new descriptor-based design framework is developed, which integrates computational methods of microstructure characterization and reconstruction, sensitivity analysis, Design of Experiments (DOE), metamodeling and optimization the enable parametric optimization of the microstructure for achieving the desired material properties. Material informatics is studied to efficiently reduce the dimension of microstructure design space. This dissertation develops a machine learning-based methodology to identify the key microstructure descriptors that highly impact properties of interest. In uncertainty quantification, a comparative study on data-driven random process models is conducted to provide guidance for choosing the most accurate model in statistical uncertainty quantification. Two new goodness-of-fit metrics are developed to provide quantitative measurements of random process models' accuracy. The benefits of the proposed methods are demonstrated by the example of designing the microstructure of polymer nanocomposites. This dissertation provides material-generic, intelligent modeling/design methodologies and techniques to accelerate the process of analyzing and designing new microstructural materials system.

Calibration of an Unsteady Groundwater Flow Model for a Complex, Strongly Heterogeneous Aquifer

NASA Astrophysics Data System (ADS)

Curtis, Z. K.; Liao, H.; Li, S. G.; Phanikumar, M. S.; Lusch, D.

2016-12-01

Modeling of groundwater systems characterized by complex three-dimensional structure and heterogeneity remains a significant challenge. Most of today's groundwater models are developed based on relatively simple conceptual representations in favor of model calibratibility. As more complexities are modeled, e.g., by adding more layers and/or zones, or introducing transient processes, more parameters have to be estimated and issues related to ill-posed groundwater problems and non-unique calibration arise. Here, we explore the use of an alternative conceptual representation for groundwater modeling that is fully three-dimensional and can capture complex 3D heterogeneity (both systematic and "random") without over-parameterizing the aquifer system. In particular, we apply Transition Probability (TP) geostatistics on high resolution borehole data from a water well database to characterize the complex 3D geology. Different aquifer material classes, e.g., `AQ' (aquifer material), `MAQ' (marginal aquifer material'), `PCM' (partially confining material), and `CM' (confining material), are simulated, with the hydraulic properties of each material type as tuning parameters during calibration. The TP-based approach is applied to simulate unsteady groundwater flow in a large, complex, and strongly heterogeneous glacial aquifer system in Michigan across multiple spatial and temporal scales. The resulting model is calibrated to observed static water level data over a time span of 50 years. The results show that the TP-based conceptualization enables much more accurate and robust calibration/simulation than that based on conventional deterministic layer/zone based conceptual representations.

Unleashing elastic energy: dynamics of energy release in rubber bands and impulsive biological systems

NASA Astrophysics Data System (ADS)

Ilton, Mark; Cox, Suzanne; Egelmeers, Thijs; Patek, S. N.; Crosby, Alfred J.

Impulsive biological systems - which include mantis shrimp, trap-jaw ants, and venus fly traps - can reach high speeds by using elastic elements to store and rapidly release energy. The material behavior and shape changes critical to achieving rapid energy release in these systems are largely unknown due to limitations of materials testing instruments operating at high speed and large displacement. In this work, we perform fundamental, proof-of-concept measurements on the tensile retraction of elastomers. Using high speed imaging, the kinematics of retraction are measured for elastomers with varying mechanical properties and geometry. Based on the kinematics, the rate of energy dissipation in the material is determined as a function of strain and strain-rate, along with a scaling relation which describes the dependence of maximum velocity on material properties. Understanding this scaling relation along with the material failure limits of the elastomer allows the prediction of material properties required for optimal performance. We demonstrate this concept experimentally by optimizing for maximum velocity in our synthetic model system, and achieve retraction velocities that exceed those in biological impulsive systems. This model system provides a foundation for future work connecting continuum performance to molecular architecture in impulsive systems.

The thermoelectric properties of strongly correlated systems

NASA Astrophysics Data System (ADS)

Cai, Jianwei

Strongly correlated systems are among the most interesting and complicated systems in physics. Large Seebeck coefficients are found in some of these systems, which highlight the possibility for thermoelectric applications. In this thesis, we study the thermoelectric properties of these strongly correlated systems with various methods. We derived analytic formulas for the resistivity and Seebeck coefficient of the periodic Anderson model based on the dynamic mean field theory. These formulas were possible as the self energy of the single impurity Anderson model could be given by an analytic ansatz derived from experiments and numerical calculations instead of complicated numerical calculations. The results show good agreement with the experimental data of rare-earth compound in a restricted temperature range. These formulas help to understand the properties of periodic Anderson model. Based on the study of rare-earth compounds, we proposed a design for the thermoelectric meta-material. This manmade material is made of quantum dots linked by conducting linkers. The quantum dots act as the rare-earth atoms with heavier mass. We set up a model similar to the periodic Anderson model for this new material. The new model was studied with the perturbation theory for energy bands. The dynamic mean field theory with numerical renormalization group as the impurity solver was used to study the transport properties. With these studies, we confirmed the improved thermoelectric properties of the designed material.

Model-based control strategies for systems with constraints of the program type

NASA Astrophysics Data System (ADS)

Jarzębowska, Elżbieta

2006-08-01

The paper presents a model-based tracking control strategy for constrained mechanical systems. Constraints we consider can be material and non-material ones referred to as program constraints. The program constraint equations represent tasks put upon system motions and they can be differential equations of orders higher than one or two, and be non-integrable. The tracking control strategy relies upon two dynamic models: a reference model, which is a dynamic model of a system with arbitrary order differential constraints and a dynamic control model. The reference model serves as a motion planner, which generates inputs to the dynamic control model. It is based upon a generalized program motion equations (GPME) method. The method enables to combine material and program constraints and merge them both into the motion equations. Lagrange's equations with multipliers are the peculiar case of the GPME, since they can be applied to systems with constraints of first orders. Our tracking strategy referred to as a model reference program motion tracking control strategy enables tracking of any program motion predefined by the program constraints. It extends the "trajectory tracking" to the "program motion tracking". We also demonstrate that our tracking strategy can be extended to a hybrid program motion/force tracking.

The properties of an ion selective enzymatic asymmetric synthetic membrane.

NASA Technical Reports Server (NTRS)

Mitz, M. A.

1971-01-01

With the aid of a simple model membrane system, the properties of cellulose enzymes and of membrane selectivity and pump-like action are considered. The model is based on materials possibly present on a primitive earth, as well as on a membrane able to sort or concentrate these materials. An overview of the model membrane system is presented in terms of how it is constructed, what its properties are, and what to expect in performance characteristics. The model system is shown to be useful for studying the selective and in some cases accelerated transfer of nutrients and metabolites.

Predictive modeling of infrared detectors and material systems

NASA Astrophysics Data System (ADS)

Pinkie, Benjamin

Detectors sensitive to thermal and reflected infrared radiation are widely used for night-vision, communications, thermography, and object tracking among other military, industrial, and commercial applications. System requirements for the next generation of ultra-high-performance infrared detectors call for increased functionality such as large formats (> 4K HD) with wide field-of-view, multispectral sensitivity, and on-chip processing. Due to the low yield of infrared material processing, the development of these next-generation technologies has become prohibitively costly and time consuming. In this work, it will be shown that physics-based numerical models can be applied to predictively simulate infrared detector arrays of current technological interest. The models can be used to a priori estimate detector characteristics, intelligently design detector architectures, and assist in the analysis and interpretation of existing systems. This dissertation develops a multi-scale simulation model which evaluates the physics of infrared systems from the atomic (material properties and electronic structure) to systems level (modulation transfer function, dense array effects). The framework is used to determine the electronic structure of several infrared materials, optimize the design of a two-color back-to-back HgCdTe photodiode, investigate a predicted failure mechanism for next-generation arrays, and predict the systems-level measurables of a number of detector architectures.

Explicit Finite Element Modeling of Multilayer Composite Fabric for Gas Turbine Engine Containment Systems, Phase II. Part 3; Material Model Development and Simulation of Experiments

NASA Technical Reports Server (NTRS)

Simmons, J.; Erlich, D.; Shockey, D.

2009-01-01

A team consisting of Arizona State University, Honeywell Engines, Systems & Services, the National Aeronautics and Space Administration Glenn Research Center, and SRI International collaborated to develop computational models and verification testing for designing and evaluating turbine engine fan blade fabric containment structures. This research was conducted under the Federal Aviation Administration Airworthiness Assurance Center of Excellence and was sponsored by the Aircraft Catastrophic Failure Prevention Program. The research was directed toward improving the modeling of a turbine engine fabric containment structure for an engine blade-out containment demonstration test required for certification of aircraft engines. The research conducted in Phase II began a new level of capability to design and develop fan blade containment systems for turbine engines. Significant progress was made in three areas: (1) further development of the ballistic fabric model to increase confidence and robustness in the material models for the Kevlar(TradeName) and Zylon(TradeName) material models developed in Phase I, (2) the capability was improved for finite element modeling of multiple layers of fabric using multiple layers of shell elements, and (3) large-scale simulations were performed. This report concentrates on the material model development and simulations of the impact tests.

Dynamic Modeling of ALS Systems

NASA Technical Reports Server (NTRS)

Jones, Harry

2002-01-01

The purpose of dynamic modeling and simulation of Advanced Life Support (ALS) systems is to help design them. Static steady state systems analysis provides basic information and is necessary to guide dynamic modeling, but static analysis is not sufficient to design and compare systems. ALS systems must respond to external input variations and internal off-nominal behavior. Buffer sizing, resupply scheduling, failure response, and control system design are aspects of dynamic system design. We develop two dynamic mass flow models and use them in simulations to evaluate systems issues, optimize designs, and make system design trades. One model is of nitrogen leakage in the space station, the other is of a waste processor failure in a regenerative life support system. Most systems analyses are concerned with optimizing the cost/benefit of a system at its nominal steady-state operating point. ALS analysis must go beyond the static steady state to include dynamic system design. All life support systems exhibit behavior that varies over time. ALS systems must respond to equipment operating cycles, repair schedules, and occasional off-nominal behavior or malfunctions. Biological components, such as bioreactors, composters, and food plant growth chambers, usually have operating cycles or other complex time behavior. Buffer sizes, material stocks, and resupply rates determine dynamic system behavior and directly affect system mass and cost. Dynamic simulation is needed to avoid the extremes of costly over-design of buffers and material reserves or system failure due to insufficient buffers and lack of stored material.

Optimizing spectral CT parameters for material classification tasks

NASA Astrophysics Data System (ADS)

Rigie, D. S.; La Rivière, P. J.

2016-06-01

In this work, we propose a framework for optimizing spectral CT imaging parameters and hardware design with regard to material classification tasks. Compared with conventional CT, many more parameters must be considered when designing spectral CT systems and protocols. These choices will impact material classification performance in a non-obvious, task-dependent way with direct implications for radiation dose reduction. In light of this, we adapt Hotelling Observer formalisms typically applied to signal detection tasks to the spectral CT, material-classification problem. The result is a rapidly computable metric that makes it possible to sweep out many system configurations, generating parameter optimization curves (POC’s) that can be used to select optimal settings. The proposed model avoids restrictive assumptions about the basis-material decomposition (e.g. linearity) and incorporates signal uncertainty with a stochastic object model. This technique is demonstrated on dual-kVp and photon-counting systems for two different, clinically motivated material classification tasks (kidney stone classification and plaque removal). We show that the POC’s predicted with the proposed analytic model agree well with those derived from computationally intensive numerical simulation studies.

Optimizing Spectral CT Parameters for Material Classification Tasks

PubMed Central

Rigie, D. S.; La Rivière, P. J.

2017-01-01

In this work, we propose a framework for optimizing spectral CT imaging parameters and hardware design with regard to material classification tasks. Compared with conventional CT, many more parameters must be considered when designing spectral CT systems and protocols. These choices will impact material classification performance in a non-obvious, task-dependent way with direct implications for radiation dose reduction. In light of this, we adapt Hotelling Observer formalisms typically applied to signal detection tasks to the spectral CT, material-classification problem. The result is a rapidly computable metric that makes it possible to sweep out many system configurations, generating parameter optimization curves (POC’s) that can be used to select optimal settings. The proposed model avoids restrictive assumptions about the basis-material decomposition (e.g. linearity) and incorporates signal uncertainty with a stochastic object model. This technique is demonstrated on dual-kVp and photon-counting systems for two different, clinically motivated material classification tasks (kidney stone classification and plaque removal). We show that the POC’s predicted with the proposed analytic model agree well with those derived from computationally intensive numerical simulation studies. PMID:27227430

Tensile failure criteria for fiber composite materials

NASA Technical Reports Server (NTRS)

Rosen, B. W.; Zweben, C. H.

1972-01-01

The analysis provides insight into the failure mechanics of these materials and defines criteria which serve as tools for preliminary design material selection and for material reliability assessment. The model incorporates both dispersed and propagation type failures and includes the influence of material heterogeneity. The important effects of localized matrix damage and post-failure matrix shear stress transfer are included in the treatment. The model is used to evaluate the influence of key parameters on the failure of several commonly used fiber-matrix systems. Analyses of three possible failure modes were developed. These modes are the fiber break propagation mode, the cumulative group fracture mode, and the weakest link mode. Application of the new model to composite material systems has indicated several results which require attention in the development of reliable structural composites. Prominent among these are the size effect and the influence of fiber strength variability.

Meta-Analysis of the Minimalist Training Model

ERIC Educational Resources Information Center

Ginns, Paul; Hollender, Nina; Reimann, Peter

2006-01-01

This article reviews research on the Minimalist instructional design model, a learner-centred approach to the design of instructional materials such as computer program manuals or on-line help. Studies in this paradigm have typically compared minimalist materials against traditional "system-centred" materials. Additionally, some studies have…

The Risk-Informed Materials Management (RIMM) Tool System for Determining Safe-Levels of Contaminated Materials Managed on the Land

EPA Science Inventory

EPA’s Risk-Informed Materials Management (RIMM) tool system is a modeling approach that helps risk assessors evaluate the safety of managing raw, reused, or waste material streams via a variety of common scenarios (e.g., application to farms, use as a component in road cons...

From the experience of development of composite materials with desired properties

NASA Astrophysics Data System (ADS)

Garkina, I. A.; Danilov, A. M.

2017-04-01

Using the experience in the development of composite materials with desired properties is given the algorithm of construction materials synthesis on the basis of their representation in the form of a complex system. The possibility of creation of a composite and implementation of the technical task originally are defined at a stage of cognitive modeling. On the basis of development of the cognitive map hierarchical structures of criteria of quality are defined; according to them for each allocated large-scale level the corresponding block diagrams of system are specified. On the basis of the solution of problems of one-criteria optimization with use of the found optimum values formalization of a multi-criteria task and its decision is carried out (the optimum organization and properties of system are defined). The emphasis is on methodological aspects of mathematical modeling (construction of a generalized and partial models to optimize the properties and structure of materials, including those based on the concept of systemic homeostasis).

Development of an Unstructured, Three-Dimensional Material Response Design Tool

NASA Technical Reports Server (NTRS)

Schulz, Joseph; Stern, Eric; Palmer, Grant; Muppidi, Suman; Schroeder, Olivia

2017-01-01

A preliminary verification and validation of a new material response model is presented. This model, Icarus, is intended to serve as a design tool for the thermal protection systems of re-entry vehicles. Currently, the capability of the model is limited to simulating the pyrolysis of a material as a result of the radiative and convective surface heating imposed on the material from the surrounding high enthalpy gas. Since the major focus behind the development of Icarus has been model extensibility, the hope is that additional physics can be quickly added. The extensibility is critical since thermal protection systems are becoming increasing complex, e.g. woven carbon polymers. Additionally, as a three-dimensional, unstructured, finite-volume model, Icarus is capable of modeling complex geometries as well as multi-dimensional physics, which have been shown to be important in some scenarios and are not captured by one-dimensional models. In this paper, the mathematical and numerical formulation is presented followed by a discussion of the software architecture and some preliminary verification and validation studies.

Mechanical Properties of Air Plasma Sprayed Environmental Barrier Coating (EBC) Materials

NASA Technical Reports Server (NTRS)

Richards, Bradley; Zhu, Dongming; Ghosn, Louis; Wadley, Haydn

2015-01-01

Development work in Environmental Barrier Coatings (EBCs) for Ceramic Matrix Composites (CMCs) has focused considerably on the identification of materials systems and coating architectures to meet application needs. The evolution of these systems has occurred so quickly that modeling efforts and requisite data for modeling lag considerably behind development. Materials property data exists for many systems in the bulk form, but the effects of deposition on the critical properties of strength and fracture behavior are not well studied. We have plasma sprayed bulk samples of baseline EBC materials (silicon, ytterbium disilicate) and tested the mechanical properties of these materials to elicit differences in strength and toughness. We have also endeavored to assess the mixed-mode fracture resistance, Gc, of silicon in a baseline EBC applied to SiCSiC CMC via four point bend test. These results are compared to previously determined properties of the comparable bulk material.

STUDY OF THERMAL SENSITIVITY AND THERMAL EXPLOSION VIOLENCE OF ENERGETIC MATERIALS IN THE LLNL ODTX SYSTEM

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

HSU, P C; Hust, G; May, C

Some energetic materials may explode at fairly low temperatures and the violence from thermal explosion may cause a significant damage. Thus it is important to understand the response of energetic materials to thermal insults for safe handling and storage of energetic materials. The One Dimensional Time to Explosion (ODTX) system at the Lawrence Livermore National Laboratory can measure times to explosion, lowest explosion temperatures, and determine kinetic parameters of energetic materials. Samples of different configurations can be tested in the system. The ODTX testing can also generate useful data for determining thermal explosion violence of energetic materials. We also performedmore » detonation experiments of LX-10 in aluminum anvils to determine the detonation violence and validated the Zerilli Armstrong aluminum model. Results of the detonation experiments agreed well with the model prediction.« less

User-Defined Material Model for Progressive Failure Analysis

NASA Technical Reports Server (NTRS)

Knight, Norman F. Jr.; Reeder, James R. (Technical Monitor)

2006-01-01

An overview of different types of composite material system architectures and a brief review of progressive failure material modeling methods used for structural analysis including failure initiation and material degradation are presented. Different failure initiation criteria and material degradation models are described that define progressive failure formulations. These progressive failure formulations are implemented in a user-defined material model (or UMAT) for use with the ABAQUS/Standard1 nonlinear finite element analysis tool. The failure initiation criteria include the maximum stress criteria, maximum strain criteria, the Tsai-Wu failure polynomial, and the Hashin criteria. The material degradation model is based on the ply-discounting approach where the local material constitutive coefficients are degraded. Applications and extensions of the progressive failure analysis material model address two-dimensional plate and shell finite elements and three-dimensional solid finite elements. Implementation details and use of the UMAT subroutine are described in the present paper. Parametric studies for composite structures are discussed to illustrate the features of the progressive failure modeling methods that have been implemented.

Computer modelling of the optical behaviour of rare earth dopants in BaY2F8

NASA Astrophysics Data System (ADS)

Jackson, R. A.; Valerio, M. E. G.; Couto Dos Santos, M. A.; Amaral, J. B.

2005-01-01

BaY2F8, when doped with rare earth elements is a material of interest in the development of solid-state laser systems, especially for use in the infrared region. This paper presents the application of a new computational technique, which combines atomistic modelling and crystal field calculations in a study of rare earth doping of the material. Atomistic modelling is used to calculate the symmetry and detailed geometry of the dopant ion-host lattice system, and this information is then used to calculate the crystal field parameters, which are an important indicator in assessing the optical behaviour of the dopant-crystal system. Comparisons with the results of recent experimental work on this material are made.

Effects of implant system, impression technique, and impression material on accuracy of the working cast.

PubMed

Wegner, Kerstin; Weskott, Katharina; Zenginel, Martha; Rehmann, Peter; Wöstmann, Bernd

2013-01-01

This in vitro study aimed to identify the effects of the implant system, impression technique, and impression material on the transfer accuracy of implant impressions. The null hypothesis tested was that, in vitro and within the parameters of the experiment, the spatial relationship of a working cast to the placement of implants is not related to (1) the implant system, (2) the impression technique, or (3) the impression material. A steel maxilla was used as a reference model. Six implants of two different implant systems (Standard Plus, Straumann; Semados, Bego) were fixed in the reference model. The target variables were: three-dimensional (3D) shift in all directions, implant axis direction, and rotation. The target variables were assessed using a 3D coordinate measuring machine, and the respective deviations of the plaster models from the nominal values of the reference model were calculated. Two different impression techniques (reposition/pickup) and four impression materials (Aquasil Ultra, Flexitime, Impregum Penta, P2 Magnum 360) were investigated. In all, 80 implant impressions for each implant system were taken. Statistical analysis was performed using multivariate analysis of variance. The implant system significantly influenced the transfer accuracy for most spatial dimensions, including the overall 3D shift and implant axis direction. There was no significant difference between the two implant systems with regard to rotation. Multivariate analysis of variance showed a significant effect on transfer accuracy only for the implant system. Within the limits of the present study, it can be concluded that the transfer accuracy of the intraoral implant position on the working cast is far more dependent on the implant system than on the selection of a specific impression technique or material.

A Statistics-Based Material Property Analysis to Support TPS Characterization

NASA Technical Reports Server (NTRS)

Copeland, Sean R.; Cozmuta, Ioana; Alonso, Juan J.

2012-01-01

Accurate characterization of entry capsule heat shield material properties is a critical component in modeling and simulating Thermal Protection System (TPS) response in a prescribed aerothermal environment. The thermal decomposition of the TPS material during the pyrolysis and charring processes is poorly characterized and typically results in large uncertainties in material properties as inputs for ablation models. These material property uncertainties contribute to large design margins on flight systems and cloud re- construction efforts for data collected during flight and ground testing, making revision to existing models for entry systems more challenging. The analysis presented in this work quantifies how material property uncertainties propagate through an ablation model and guides an experimental test regimen aimed at reducing these uncertainties and characterizing the dependencies between properties in the virgin and charred states for a Phenolic Impregnated Carbon Ablator (PICA) based TPS. A sensitivity analysis identifies how the high-fidelity model behaves in the expected flight environment, while a Monte Carlo based uncertainty propagation strategy is used to quantify the expected spread in the in-depth temperature response of the TPS. An examination of how perturbations to the input probability density functions affect output temperature statistics is accomplished using a Kriging response surface of the high-fidelity model. Simulations are based on capsule configuration and aerothermal environments expected during the Mars Science Laboratory (MSL) entry sequence. We identify and rank primary sources of uncertainty from material properties in a flight-relevant environment, show the dependence on spatial orientation and in-depth location on those uncertainty contributors, and quantify how sensitive the expected results are.

Experimental analysis of bidirectional reflectance distribution function cross section conversion term in direction cosine space.

PubMed

Butler, Samuel D; Nauyoks, Stephen E; Marciniak, Michael A

2015-06-01

Of the many classes of bidirectional reflectance distribution function (BRDF) models, two popular classes of models are the microfacet model and the linear systems diffraction model. The microfacet model has the benefit of speed and simplicity, as it uses geometric optics approximations, while linear systems theory uses a diffraction approach to compute the BRDF, at the expense of greater computational complexity. In this Letter, nongrazing BRDF measurements of rough and polished surface-reflecting materials at multiple incident angles are scaled by the microfacet cross section conversion term, but in the linear systems direction cosine space, resulting in great alignment of BRDF data at various incident angles in this space. This results in a predictive BRDF model for surface-reflecting materials at nongrazing angles, while avoiding some of the computational complexities in the linear systems diffraction model.

Effect of primary and secondary parameters on analytical estimation of effective thermal conductivity of two phase materials using unit cell approach

NASA Astrophysics Data System (ADS)

S, Chidambara Raja; P, Karthikeyan; Kumaraswamidhas, L. A.; M, Ramu

2018-05-01

Most of the thermal design systems involve two phase materials and analysis of such systems requires detailed understanding of the thermal characteristics of the two phase material. This article aimed to develop geometry dependent unit cell approach model by considering the effects of all primary parameters (conductivity ratio and concentration) and secondary parameters (geometry, contact resistance, natural convection, Knudsen and radiation) for the estimation of effective thermal conductivity of two-phase materials. The analytical equations have been formulated based on isotherm approach for 2-D and 3-D spatially periodic medium. The developed models are validated with standard models and suited for all kind of operating conditions. The results have shown substantial improvement compared to the existing models and are in good agreement with the experimental data.

Modeling of the solution interaction properties of plastic materials used in pharmaceutical product container systems.

PubMed

Jenke, Dennis; Couch, Tom; Gillum, Amy; Sadain, Salma

2009-01-01

Material/water equilibrium binding constants (Eb) were determined for 14 organic solutes and 17 plastic raw materials that could be used in pharmaceutical product container systems. Correlations between the measured binding constants and the organic solute's octanol/water and hexane/water partition coefficients were obtained. In general, while the materials examined exhibited a wide range of binding characteristics, the tested materials by and large fell within two broad classes: (1) those that were octanol-like in their binding characteristics, and (2) those that were hexane-like. Materials of the same class (e.g., polypropylenes) generally had binding models that were very similar. Rank ordering of the materials in terms of their magnitude of drug binding (least binding to most binding) was as follows: polypropylene < polyethylene < polyamide < styrene-ethylene-butylene-styrene < copolyester ether elastomer approximately equal to amine-terminated poly fatty acid amide polymer. The utilization of the developed models to estimate drug loss via sorption by the container is discussed.

A mixed-unit input-output model for environmental life-cycle assessment and material flow analysis.

PubMed

Hawkins, Troy; Hendrickson, Chris; Higgins, Cortney; Matthews, H Scott; Suh, Sangwon

2007-02-01

Materials flow analysis models have traditionally been used to track the production, use, and consumption of materials. Economic input-output modeling has been used for environmental systems analysis, with a primary benefit being the capability to estimate direct and indirect economic and environmental impacts across the entire supply chain of production in an economy. We combine these two types of models to create a mixed-unit input-output model that is able to bettertrack economic transactions and material flows throughout the economy associated with changes in production. A 13 by 13 economic input-output direct requirements matrix developed by the U.S. Bureau of Economic Analysis is augmented with material flow data derived from those published by the U.S. Geological Survey in the formulation of illustrative mixed-unit input-output models for lead and cadmium. The resulting model provides the capabilities of both material flow and input-output models, with detailed material tracking through entire supply chains in response to any monetary or material demand. Examples of these models are provided along with a discussion of uncertainty and extensions to these models.

Using thermal balance model to determine optimal reactor volume and insulation material needed in a laboratory-scale composting reactor.

PubMed

Wang, Yongjiang; Pang, Li; Liu, Xinyu; Wang, Yuansheng; Zhou, Kexun; Luo, Fei

2016-04-01

A comprehensive model of thermal balance and degradation kinetics was developed to determine the optimal reactor volume and insulation material. Biological heat production and five channels of heat loss were considered in the thermal balance model for a representative reactor. Degradation kinetics was developed to make the model applicable to different types of substrates. Simulation of the model showed that the internal energy accumulation of compost was the significant heat loss channel, following by heat loss through reactor wall, and latent heat of water evaporation. Lower proportion of heat loss occurred through the reactor wall when the reactor volume was larger. Insulating materials with low densities and low conductive coefficients were more desirable for building small reactor systems. Model developed could be used to determine the optimal reactor volume and insulation material needed before the fabrication of a lab-scale composting system. Copyright © 2016 Elsevier Ltd. All rights reserved.

Models of an In-Situ Propellant Production Plant for Mars Exploration

NASA Technical Reports Server (NTRS)

Goodrich, Charlie; Kurien, James; Millar, Bill; Sweet, Adam; Waterman, Sue; Clancy, Daniel (Technical Monitor)

2001-01-01

An in-situ propellant production system (ISPP) is designed to make rocket fuel from chemicals in the Martian atmosphere in order to reduce the amount of materials that would need to be brought from Earth to support Mars missions. We have developed a description of a hypothetical ISPP system that we would like to make available to researchers who are interested in the problem of automatically diagnosing failures in complex NASA systems. This problem description will help researchers to investigate problems of interest to NASA. We would like to make the following material publicly available: (1) a 'common sense' model of an ISPP system; (2) low- and medium-fidelity simulations of the ISPP system written in Microsoft Excel and HCC; and (3) previously published data and diagrams concerning ISPP components. We do not believe there are any export considerations on these materials for the following reasons: (1) These models are not useful for guidance and real time control of vehicles, encrpytion, or any other software purpose categorized under the Export Control Classification Numbers; and (2) The models are very high level and would not by themselves enable real-time control of a real hardware system. The models are at the level of common sense. They capture, for example, that if a heater is turned on an increase in temperature should result(see the attached excerpt). We do not believe there is any commercial value to this material, given the low commercial demand for propellant plants on mars. We have spoken to acting Code IC Division Chief Dan Clancy, and he concurs with our desire to make these materials publicly available via a technical report.

Transferable tight-binding model for strained group IV and III-V materials and heterostructures

NASA Astrophysics Data System (ADS)

Tan, Yaohua; Povolotskyi, Michael; Kubis, Tillmann; Boykin, Timothy B.; Klimeck, Gerhard

2016-07-01

It is critical to capture the effect due to strain and material interface for device level transistor modeling. We introduce a transferable s p3d5s* tight-binding model with nearest-neighbor interactions for arbitrarily strained group IV and III-V materials. The tight-binding model is parametrized with respect to hybrid functional (HSE06) calculations for varieties of strained systems. The tight-binding calculations of ultrasmall superlattices formed by group IV and group III-V materials show good agreement with the corresponding HSE06 calculations. The application of the tight-binding model to superlattices demonstrates that the transferable tight-binding model with nearest-neighbor interactions can be obtained for group IV and III-V materials.

Modeling the Behaviour of an Advanced Material Based Smart Landing Gear System for Aerospace Vehicles

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

Varughese, Byji; Dayananda, G. N.; Rao, M. Subba

2008-07-29

The last two decades have seen a substantial rise in the use of advanced materials such as polymer composites for aerospace structural applications. In more recent years there has been a concerted effort to integrate materials, which mimic biological functions (referred to as smart materials) with polymeric composites. Prominent among smart materials are shape memory alloys, which possess both actuating and sensory functions that can be realized simultaneously. The proper characterization and modeling of advanced and smart materials holds the key to the design and development of efficient smart devices/systems. This paper focuses on the material characterization; modeling and validationmore » of the model in relation to the development of a Shape Memory Alloy (SMA) based smart landing gear (with high energy dissipation features) for a semi rigid radio controlled airship (RC-blimp). The Super Elastic (SE) SMA element is configured in such a way that it is forced into a tensile mode of high elastic deformation. The smart landing gear comprises of a landing beam, an arch and a super elastic Nickel-Titanium (Ni-Ti) SMA element. The landing gear is primarily made of polymer carbon composites, which possess high specific stiffness and high specific strength compared to conventional materials, and are therefore ideally suited for the design and development of an efficient skid landing gear system with good energy dissipation characteristics. The development of the smart landing gear in relation to a conventional metal landing gear design is also dealt with.« less

U.S. Patent Pending, Cyberspace Security System for Complex Systems, U.S. Patent Application No.: 14/134,949

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

Abercrombie, Robert K; Sheldon, Frederick T; Mili, Ali

A computer implemented method monetizes the security of a cyber-system in terms of losses each stakeholder may expect to lose if a security break down occurs. A non-transitory media stores instructions for generating a stake structure that includes costs that each stakeholder of a system would lose if the system failed to meet security requirements and generating a requirement structure that includes probabilities of failing requirements when computer components fails. The system generates a vulnerability model that includes probabilities of a component failing given threats materializing and generates a perpetrator model that includes probabilities of threats materializing. The system generatesmore » a dot product of the stakes structure, the requirement structure, the vulnerability model and the perpetrator model. The system can further be used to compare, contrast and evaluate alternative courses of actions best suited for the stakeholders and their requirements.« less

Inverse approaches with lithologic information for a regional groundwater system in southwest Kansas

USGS Publications Warehouse

Tsou, Ming‐shu; Perkins, S.P.; Zhan, X.; Whittemore, Donald O.; Zheng, Lingyun

2006-01-01

Two practical approaches incorporating lithologic information for groundwater modeling calibration are presented to estimate distributed, cell-based hydraulic conductivity. The first approach is to estimate optimal hydraulic conductivities for geological materials by incorporating thickness distribution of materials into inverse modeling. In the second approach, residuals for the groundwater model solution are minimized according to a globalized Newton method with the aid of a Geographic Information System (GIS) to calculate a cell-wise distribution of hydraulic conductivity. Both approaches honor geologic data and were effective in characterizing the heterogeneity of a regional groundwater modeling system in southwest Kansas. ?? 2005 Elsevier Ltd All rights reserved.

Computational Materials: Modeling and Simulation of Nanostructured Materials and Systems

NASA Technical Reports Server (NTRS)

Gates, Thomas S.; Hinkley, Jeffrey A.

2003-01-01

The paper provides details on the structure and implementation of the Computational Materials program at the NASA Langley Research Center. Examples are given that illustrate the suggested approaches to predicting the behavior and influencing the design of nanostructured materials such as high-performance polymers, composites, and nanotube-reinforced polymers. Primary simulation and measurement methods applicable to multi-scale modeling are outlined. Key challenges including verification and validation of models are highlighted and discussed within the context of NASA's broad mission objectives.

Parallel Program Systems for the Analysis of Wave Processes in Elastic-Plastic, Granular, Porous and Multi-Blocky Media

NASA Astrophysics Data System (ADS)

Sadovskaya, Oxana; Sadovskii, Vladimir

2017-04-01

Under modeling the wave propagation processes in geomaterials (granular and porous media, soils and rocks) it is necessary to take into account the structural inhomogeneity of these materials. Parallel program systems for numerical solution of 2D and 3D problems of the dynamics of deformable media with constitutive relationships of rather general form on the basis of universal mathematical model describing small strains of elastic, elastic-plastic, granular and porous materials are worked out. In the case of an elastic material, the model is reduced to the system of equations, hyperbolic by Friedrichs, written in terms of velocities and stresses in a symmetric form. In the case of an elastic-plastic material, the model is a special formulation of the Prandtl-Reuss theory in the form of variational inequality with one-sided constraints on the stress tensor. Generalization of the model to describe granularity and the collapse of pores is obtained by means of the rheological approach, taking into account different resistance of materials to tension and compression. Rotational motion of particles in the material microstructure is considered within the framework of a mathematical model of the Cosserat continuum. Computational domain may have a blocky structure, composed of an arbitrary number of layers, strips in a layer and blocks in a strip from different materials with self-consistent curvilinear interfaces. At the external boundaries of computational domain the main types of dissipative boundary conditions in terms of velocities, stresses or mixed boundary conditions can be given. Shock-capturing algorithm is proposed for implementation of the model on supercomputers with cluster architecture. It is based on the two-cyclic splitting method with respect to spatial variables and the special procedures of the stresses correction to take into account plasticity, granularity or porosity of a material. An explicit monotone ENO-scheme is applied for solving one-dimensional systems of equations at the stages of splitting method. The parallelizing of computations is carried out using the MPI library and the SPMD technology. The data exchange between processors occurs at step "predictor" of the finite-difference scheme. Program systems allow simulate the propagation of waves produced by external mechanical effects in a medium, aggregated of arbitrary number of heterogeneous blocks. Some computations of dynamic problems with and without taking into account the moment properties of a material were performed on clusters of ICM SB RAS (Krasnoyarsk) and JSCC RAS (Moscow). Parallel program systems 2Dyn_Granular, 3Dyn_Granular, 2Dyn_Cosserat, 3Dyn_Cosserat and 2Dyn_Blocks_MPI for numerical solution of 2D and 3D elastic-plastic problems of the dynamics of granular media and problems of the Cosserat elasticity theory, as well as for modeling of the dynamic processes in multi-blocky media with pliant viscoelastic, porous and fluid-saturated interlayers on cluster systems were registered by Rospatent.

Experimental Validation of a Thermoelastic Model for SMA Hybrid Composites

NASA Technical Reports Server (NTRS)

Turner, Travis L.

2001-01-01

This study presents results from experimental validation of a recently developed model for predicting the thermomechanical behavior of shape memory alloy hybrid composite (SMAHC) structures, composite structures with an embedded SMA constituent. The model captures the material nonlinearity of the material system with temperature and is capable of modeling constrained, restrained, or free recovery behavior from experimental measurement of fundamental engineering properties. A brief description of the model and analysis procedures is given, followed by an overview of a parallel effort to fabricate and characterize the material system of SMAHC specimens. Static and dynamic experimental configurations for the SMAHC specimens are described and experimental results for thermal post-buckling and random response are presented. Excellent agreement is achieved between the measured and predicted results, fully validating the theoretical model for constrained recovery behavior of SMAHC structures.

Robust Informatics Infrastructure Required For ICME: Combining Virtual and Experimental Data

NASA Technical Reports Server (NTRS)

Arnold, Steven M.; Holland, Frederic A. Jr.; Bednarcyk, Brett A.

2014-01-01

With the increased emphasis on reducing the cost and time to market of new materials, the need for robust automated materials information management system(s) enabling sophisticated data mining tools is increasing, as evidenced by the emphasis on Integrated Computational Materials Engineering (ICME) and the recent establishment of the Materials Genome Initiative (MGI). This need is also fueled by the demands for higher efficiency in material testing; consistency, quality and traceability of data; product design; engineering analysis; as well as control of access to proprietary or sensitive information. Further, the use of increasingly sophisticated nonlinear, anisotropic and or multi-scale models requires both the processing of large volumes of test data and complex materials data necessary to establish processing-microstructure-property-performance relationships. Fortunately, material information management systems have kept pace with the growing user demands and evolved to enable: (i) the capture of both point wise data and full spectra of raw data curves, (ii) data management functions such as access, version, and quality controls;(iii) a wide range of data import, export and analysis capabilities; (iv) data pedigree traceability mechanisms; (v) data searching, reporting and viewing tools; and (vi) access to the information via a wide range of interfaces. This paper discusses key principles for the development of a robust materials information management system to enable the connections at various length scales to be made between experimental data and corresponding multiscale modeling toolsets to enable ICME. In particular, NASA Glenn's efforts towards establishing such a database for capturing constitutive modeling behavior for both monolithic and composites materials

Establishment of a VISAR Measurement System for Material Model Validation in DSTO

DTIC Science & Technology

2013-02-01

advancements published in the works by L.M. Baker, E.R. Hollenbach and W.F. Hemsing [1-3] and results in the user-friendly interface and configuration of the...VISAR system [4] used in the current work . VISAR tests are among the mandatory instrumentation techniques when validating material models and...The present work reports on preliminary tests using the recently commissioned DSTO VISAR system, providing an assessment of the experimental set-up

External Device to Incrementally Skid the Habitat (E-DISH)

NASA Technical Reports Server (NTRS)

Brazell, J. W.; Introne, Steve; Bedell, Lisa; Credle, Ben; Holp, Graham; Ly, Siao; Tait, Terry

1994-01-01

A Mars habitat transport system was designed as part of the NASA Mars exploration program. The transport system, the External Device to Incrementally Skid the Habitat (E - DISH), will be used to transport Mars habitats from their landing sites to the colony base and will be detached after unloading. The system requirements for Mars were calculated and scaled for model purposes. Specific model materials are commonly found and recommendations for materials for the Mars design are included.

Critical thickness of transition from 2D to 3D growth and peculiarities of quantum dots formation in GexSi1-x/Sn/Si and Ge1-ySny/Si systems

NASA Astrophysics Data System (ADS)

Lozovoy, Kirill A.; Kokhanenko, Andrey P.; Voitsekhovskii, Alexander V.

2018-03-01

Nowadays using of tin as one of the deposited materials in GeSi/Sn/Si, GeSn/Si and GeSiSn/Si material systems is one of the most topical problems. These materials are very promising for various applications in nanoelectronics and optoelectronics due to possibility of band gap management and synthesis of direct band semiconductors within these systems. However, there is a lack of theoretical investigations devoted to the peculiarities of germanium on silicon growth in the presence of tin. In this paper a new theoretical approach for modeling growth processes of binary and ternary semiconductor compounds during the molecular beam epitaxy in these systems is presented. The established kinetic model based on the general nucleation theory takes into account the change in physical and mechanical parameters, diffusion coefficient and surface energies in the presence of tin. With the help of the developed model the experimentally observed significant decrease in the 2D-3D transition temperatures for GeSiSn/Si system compared to GeSi/Si system is theoretically explained for the first time in the literature. Besides that, the derived expressions allow one to explain the experimentally observed temperature dependencies of the critical thickness, as well as to predict the average size and surface density of quantum dots for different contents and temperatures in growth experiment, that confirms applicability of the model proposed. Moreover, the established model can be easily applied to other material systems in which the Stranski-Krastanow growth mode occurs.

A 3D Lattice Modelling Study of Drying Shrinkage Damage in Concrete Repair Systems

PubMed Central

Luković, Mladena; Šavija, Branko; Schlangen, Erik; Ye, Guang; van Breugel, Klaas

2016-01-01

Differential shrinkage between repair material and concrete substrate is considered to be the main cause of premature failure of repair systems. The magnitude of induced stresses depends on many factors, for example the degree of restraint, moisture gradients caused by curing and drying conditions, type of repair material, etc. Numerical simulations combined with experimental observations can be of great use when determining the influence of these parameters on the performance of repair systems. In this work, a lattice type model was used to simulate first the moisture transport inside a repair system and then the resulting damage as a function of time. 3D simulations were performed, and damage patterns were qualitatively verified with experimental results and cracking tendencies in different brittle and ductile materials. The influence of substrate surface preparation, bond strength between the two materials, and thickness of the repair material were investigated. Benefits of using a specially tailored fibre reinforced material, namely strain hardening cementitious composite (SHCC), for controlling the damage development due to drying shrinkage in concrete repairs was also examined. PMID:28773696

A 3D Lattice Modelling Study of Drying Shrinkage Damage in Concrete Repair Systems.

PubMed

Luković, Mladena; Šavija, Branko; Schlangen, Erik; Ye, Guang; van Breugel, Klaas

2016-07-14

Differential shrinkage between repair material and concrete substrate is considered to be the main cause of premature failure of repair systems. The magnitude of induced stresses depends on many factors, for example the degree of restraint, moisture gradients caused by curing and drying conditions, type of repair material, etc. Numerical simulations combined with experimental observations can be of great use when determining the influence of these parameters on the performance of repair systems. In this work, a lattice type model was used to simulate first the moisture transport inside a repair system and then the resulting damage as a function of time. 3D simulations were performed, and damage patterns were qualitatively verified with experimental results and cracking tendencies in different brittle and ductile materials. The influence of substrate surface preparation, bond strength between the two materials, and thickness of the repair material were investigated. Benefits of using a specially tailored fibre reinforced material, namely strain hardening cementitious composite (SHCC), for controlling the damage development due to drying shrinkage in concrete repairs was also examined.

Theory, Modeling, Software and Hardware Development for Analytical and Computational Materials Science

NASA Technical Reports Server (NTRS)

Young, Gerald W.; Clemons, Curtis B.

2004-01-01

The focus of this Cooperative Agreement between the Computational Materials Laboratory (CML) of the Processing Science and Technology Branch of the NASA Glenn Research Center (GRC) and the Department of Theoretical and Applied Mathematics at The University of Akron was in the areas of system development of the CML workstation environment, modeling of microgravity and earth-based material processing systems, and joint activities in laboratory projects. These efforts complement each other as the majority of the modeling work involves numerical computations to support laboratory investigations. Coordination and interaction between the modelers, system analysts, and laboratory personnel are essential toward providing the most effective simulations and communication of the simulation results. Toward these means, The University of Akron personnel involved in the agreement worked at the Applied Mathematics Research Laboratory (AMRL) in the Department of Theoretical and Applied Mathematics while maintaining a close relationship with the personnel of the Computational Materials Laboratory at GRC. Network communication between both sites has been established. A summary of the projects we undertook during the time period 9/1/03 - 6/30/04 is included.

Modeling the transport of chemical warfare agents and simulants in polymeric substrates for reactive decontamination

NASA Astrophysics Data System (ADS)

Pearl, Thomas; Mantooth, Brent; Varady, Mark; Willis, Matthew

2014-03-01

Chemical warfare agent simulants are often used for environmental testing in place of highly toxic agents. This work sets the foundation for modeling decontamination of absorbing polymeric materials with the focus on determining relationships between agents and simulants. The correlations of agents to simulants must consider the three way interactions in the chemical-material-decontaminant system where transport and reaction occur in polymer materials. To this end, diffusion modeling of the subsurface transport of simulants and live chemical warfare agents was conducted for various polymer systems (e.g., paint coatings) with and without reaction pathways with applied decontamination. The models utilized 1D and 2D finite difference diffusion and reaction models to simulate absorption and reaction in the polymers, and subsequent flux of the chemicals out of the polymers. Experimental data including vapor flux measurements and dynamic contact angle measurements were used to determine model input parameters. Through modeling, an understanding of the relationship of simulant to live chemical warfare agent was established, focusing on vapor emission of agents and simulants from materials.

Information of Complex Systems and Applications in Agent Based Modeling.

PubMed

Bao, Lei; Fritchman, Joseph C

2018-04-18

Information about a system's internal interactions is important to modeling the system's dynamics. This study examines the finer categories of the information definition and explores the features of a type of local information that describes the internal interactions of a system. Based on the results, a dual-space agent and information modeling framework (AIM) is developed by explicitly distinguishing an information space from the material space. The two spaces can evolve both independently and interactively. The dual-space framework can provide new analytic methods for agent based models (ABMs). Three examples are presented including money distribution, individual's economic evolution, and artificial stock market. The results are analyzed in the dual-space, which more clearly shows the interactions and evolutions within and between the information and material spaces. The outcomes demonstrate the wide-ranging applicability of using the dual-space AIMs to model and analyze a broad range of interactive and intelligent systems.

Effect of Material Ion Exchanges on the Mechanical Stiffness Properties and Shear Deformation of Hydrated Cement Material Chemistry Structure C-S-H Jennite -- A Computational Modeling Study

NASA Astrophysics Data System (ADS)

Adebiyi, Babatunde Mattew

Material properties and performance are governed by material molecular chemistry structures and molecular level interactions. Methods to understand relationships between the material properties and performance and their correlation to the molecular level chemistry and morphology, and thus find ways of manipulating and adjusting matters at the atomistic level in order to improve material performance, are required. A computational material modeling methodology is investigated and demonstrated for a key cement hydrated component material chemistry structure of Calcium-Silicate-Hydrate (C-S-H) Jennite in this work. The effect of material ion exchanges on the mechanical stiffness properties and shear deformation behavior of hydrated cement material chemistry structure of Calcium Silicate Hydrate (C-S-H) Jennite was studied. Calcium ions were replaced with Magnesium ions in Jennite structure of the C-S-H gel. Different level of substitution of the ions was used. The traditional Jennite structure was obtained from the American Mineralogist Crystal Structure Database and super cells of the structures were created using a Molecular Dynamics Analyzer and Visualizer Material Studio. Molecular dynamics parameters used in the modeling analysis were determined by carrying out initial dynamic studies. 64 unit cell of C-S-H Jennite was used in material modeling analysis studies based on convergence results obtained from the elastic modulus and total energies. NVT forcite dynamics using COMPASS force field based on 200 ps dynamics time was used to determine mechanical modulus of the traditional C-S-H gel and the Magnesium ion modified structures. NVT Discover dynamics using COMPASS forcefield was used in the material modeling studies to investigate the influence of ionic exchange on the shear deformation of the associated material chemistry structures. A prior established quasi-static deformation method to emulate shear deformation of C-S-H material chemistry structure that is based on a triclinic crystal structure was used, by deforming the triclinic crystal structure at 0.2 degree per time step for 75 steps of deformation. It was observed that there is a decrease in the total energies of the systems as the percentage of magnesium ion increases in the C-S-H Jennite molecular structure systems. Investigation of effect of ion exchange on the elastic modulus shows that the elastic stiffness modulus tends to decrease as the amount of Mg in the systems increases, using either COMPASS or universal force field. On the other hand, shear moduli obtained after deforming the structures computed from the stress-strain curve obtained from material modeling increases as the amount of Mg increases in the system. The present investigations also showed that ultimate shear stress obtained from predicted shear stress---strain also increases with amount of Mg in the chemistry structure. Present study clearly demonstrates that computational material modeling following molecular dynamics analysis methodology is an effective way to predict and understand the effective material chemistry and additive changes on the stiffness and deformation characteristics in cementitious materials, and the results suggest that this method can be extended to other materials.

INTEGRATED PROTECTIVE FABRIC SYSTEM (IPFS) PHASE III PROGRAM: AEROSOL PROTECTION REPORT

DTIC Science & Technology

2017-08-16

one layer control. It was observed that aerosol swatch measurements showed no correlation to aerosol system test performance for the materials and...the BRHA model employed. It was observed that aerosol swatch measurements showed no correlation to aerosol system test performance for the...Testing” (McVeety et al., 2015). This report includes a description of the materials and material controls, a description of the IPFS configurations

Cost analysis of hospital material management systems.

PubMed

Egbelu, P J; Harmonosky, C M; Ventura, J A; O'Brien, W E; Sommer, H J

1998-01-01

Integrated healthcare material management begins with manufactures of medical/surgical supplies, uses distributors and ends at the point of use at hospitals. Recent material management philosophies in the healthcare industry, such as just-in-time and stockless systems, are yet to be fully evaluated. In order to evaluate the cost effectiveness of each type of material management technique, a cost model for hospital materials management has been designed. Several case scenarios are analyzed and results are reported.

Cohesive fracture of elastically heterogeneous materials: An integrative modeling and experimental study

NASA Astrophysics Data System (ADS)

Wang, Neng; Xia, Shuman

2017-01-01

A combined modeling and experimental effort is made in this work to examine the cohesive fracture mechanisms of heterogeneous elastic solids. A two-phase laminated composite, which mimics the key microstructural features of many tough engineering and biological materials, is selected as a model material system. Theoretical and finite element analyses with cohesive zone modeling are performed to study the effective fracture resistance of the heterogeneous material associated with unstable crack propagation and arrest. A crack-tip-position controlled algorithm is implemented in the finite element analysis to overcome the inherent instability issues resulting from crack pinning and depinning at local heterogeneities. Systematic parametric studies are carried out to investigate the effects of various material and geometrical parameters, including the modulus mismatch ratio, phase volume fraction, cohesive zone size, and cohesive law shape. Concurrently, a novel stereolithography-based three-dimensional (3D) printing system is developed and used for fabricating heterogeneous test specimens with well-controlled structural and material properties. Fracture testing of the specimens is performed using the tapered double-cantilever beam (TDCB) test method. With optimal material and geometrical parameters, heterogeneous TDCB specimens are shown to exhibit enhanced effective fracture energy and effective fracture toughness than their homogeneous counterparts, which is in good agreement with the modeling predictions. The integrative computational and experimental study presented here provides a fundamental mechanistic understanding of the fracture mechanisms in brittle heterogeneous materials and sheds light on the rational design of tough materials through patterned heterogeneities.

General Multimechanism Reversible-Irreversible Time-Dependent Constitutive Deformation Model Being Developed

NASA Technical Reports Server (NTRS)

Saleeb, A. F.; Arnold, Steven M.

2001-01-01

Since most advanced material systems (for example metallic-, polymer-, and ceramic-based systems) being currently researched and evaluated are for high-temperature airframe and propulsion system applications, the required constitutive models must account for both reversible and irreversible time-dependent deformations. Furthermore, since an integral part of continuum-based computational methodologies (be they microscale- or macroscale-based) is an accurate and computationally efficient constitutive model to describe the deformation behavior of the materials of interest, extensive research efforts have been made over the years on the phenomenological representations of constitutive material behavior in the inelastic analysis of structures. From a more recent and comprehensive perspective, the NASA Glenn Research Center in conjunction with the University of Akron has emphasized concurrently addressing three important and related areas: that is, 1) Mathematical formulation; 2) Algorithmic developments for updating (integrating) the external (e.g., stress) and internal state variables; 3) Parameter estimation for characterizing the model. This concurrent perspective to constitutive modeling has enabled the overcoming of the two major obstacles to fully utilizing these sophisticated time-dependent (hereditary) constitutive models in practical engineering analysis. These obstacles are: 1) Lack of efficient and robust integration algorithms; 2) Difficulties associated with characterizing the large number of required material parameters, particularly when many of these parameters lack obvious or direct physical interpretations.

Universality and depinning models for plastic yield in amorphous materials

NASA Astrophysics Data System (ADS)

Budrikis, Zoe; Fernandez Castellano, David; Sandfeld, Stefan; Zaiser, Michael; Zapperi, Stefano

Plastic yield in amorphous materials occurs as a result of complex collective dynamics of local reorganizations, which gives rise to rich phenomena such as strain localization, intermittent dynamics and power-law distributed avalanches. While such systems have received considerable attention, both theoretical and experimental, controversy remains over the nature of the yielding transition. We present a new fully-tensorial coarsegrained model in 2D and 3D, and demonstrate that the exponents describing avalanche distributions are universal under a variety of loading conditions, system dimensionality and size, and boundary conditions. Our results show that while depinning-type models in general are apt to describe the system, mean field depinning models are not.

Predictive Models for Dynamic Brittle Fracture and Damage at High-velocity Impact in Multilayered Targets

DTIC Science & Technology

2016-11-01

layered glass/PC systems,Functionally Graded Materials (FGMs), polycrystalline AlON, and fiber-reinforced composite (FRC) materials. For the first time we...multi-layered glass/PC systems,Functionally Graded Materials (FGMs), polycrystalline AlON, and fiber-reinforced composite (FRC) materials. For the... Composite Lamina with Peridynamics, International Journal for Multiscale Computational Engineering, (12 2011): 0. doi: Florin Bobaru, Youn Doh Ha

Investigation of crew restraint system biomechanics. Report for May 79-Mar 81

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

Phillips, N.S.; Thomson, R.A.; Fiscus, I.B.

1982-05-01

Experimental data were collected and analyses were performed to study the influence of the dynamic mechanical properties of restraint system components on human response to impact and restraint system haulback. Tests were accomplished to isolate the characteristics of the restraint system and the human body. Three restraint webbing materials were studied at varied strain rates. A pyrotechnically powered inertia reel was tested, but could not be analytically modeled successfully. Analytical models of the human and restraint system were used to study the influence of restraint material properties changes on human response parameters. An analytical model of a rhesus monkey wasmore » also used to study the efficacy of animal tests and scaling techniques to evaluate restraint systems for human use applications.« less

An efficient descriptor model for designing materials for solar cells

NASA Astrophysics Data System (ADS)

Alharbi, Fahhad H.; Rashkeev, Sergey N.; El-Mellouhi, Fedwa; Lüthi, Hans P.; Tabet, Nouar; Kais, Sabre

2015-11-01

An efficient descriptor model for fast screening of potential materials for solar cell applications is presented. It works for both excitonic and non-excitonic solar cells materials, and in addition to the energy gap it includes the absorption spectrum (α(E)) of the material. The charge transport properties of the explored materials are modelled using the characteristic diffusion length (Ld) determined for the respective family of compounds. The presented model surpasses the widely used Scharber model developed for bulk heterojunction solar cells. Using published experimental data, we show that the presented model is more accurate in predicting the achievable efficiencies. To model both excitonic and non-excitonic systems, two different sets of parameters are used to account for the different modes of operation. The analysis of the presented descriptor model clearly shows the benefit of including α(E) and Ld in view of improved screening results.

Simulation-based Extraction of Key Material Parameters from Atomic Force Microscopy

NASA Astrophysics Data System (ADS)

Alsafi, Huseen; Peninngton, Gray

Models for the atomic force microscopy (AFM) tip and sample interaction contain numerous material parameters that are often poorly known. This is especially true when dealing with novel material systems or when imaging samples that are exposed to complicated interactions with the local environment. In this work we use Monte Carlo methods to extract sample material parameters from the experimental AFM analysis of a test sample. The parameterized theoretical model that we use is based on the Virtual Environment for Dynamic AFM (VEDA) [1]. The extracted material parameters are then compared with the accepted values for our test sample. Using this procedure, we suggest a method that can be used to successfully determine unknown material properties in novel and complicated material systems. We acknowledge Fisher Endowment Grant support from the Jess and Mildred Fisher College of Science and Mathematics,Towson University.

Development of a Meso-Scale Material Model for Ballistic Fabric and Its Use in Flexible-Armor Protection Systems

NASA Astrophysics Data System (ADS)

Grujicic, M.; Bell, W. C.; Arakere, G.; He, T.; Xie, X.; Cheeseman, B. A.

2010-02-01

A meso-scale ballistic material model for a prototypical plain-woven single-ply flexible armor is developed and implemented in a material user subroutine for the use in commercial explicit finite element programs. The main intent of the model is to attain computational efficiency when calculating the mechanical response of the multi-ply fabric-based flexible-armor material during its impact with various projectiles without significantly sacrificing the key physical aspects of the fabric microstructure, architecture, and behavior. To validate the new model, a comparative finite element method analysis is carried out in which: (a) the plain-woven single-ply fabric is modeled using conventional shell elements and weaving is done in an explicit manner by snaking the yarns through the fabric and (b) the fabric is treated as a planar continuum surface composed of conventional shell elements to which the new meso-scale unit-cell based material model is assigned. The results obtained show that the material model provides a reasonably good description for the fabric deformation and fracture behavior under different combinations of fixed and free boundary conditions. Finally, the model is used in an investigation of the ability of a multi-ply soft-body armor vest to protect the wearer from impact by a 9-mm round nose projectile. The effects of inter-ply friction, projectile/yarn friction, and the far-field boundary conditions are revealed and the results explained using simple wave mechanics principles, high-deformation rate material behavior, and the role of various energy-absorbing mechanisms in the fabric-based armor systems.

Computer modelling of BaY2F8: defect structure, rare earth doping and optical behaviour

NASA Astrophysics Data System (ADS)

Amaral, J. B.; Couto Dos Santos, M. A.; Valerio, M. E. G.; Jackson, R. A.

2005-10-01

BaY2F8, when doped with rare earth elements, is a material of interest in the development of solid-state laser systems, especially for use in the infrared region. This paper presents the application of a computational technique, which combines atomistic modelling and crystal field calculations, in a study of rare earth doping of the material. Atomistic modelling is used to calculate the intrinsic defect structure and the symmetry and detailed geometry of the dopant ion-host lattice system, and this information is then used to calculate the crystal field parameters, which are an important indicator in assessing the optical behaviour of the dopant-crystal system. Energy levels are then calculated for the Dy3+-substituted material, and comparisons with the results of recent experimental work are made.

Monitoring of biofilm-associated Legionella pneumophila on different substrata in model cooling tower system.

PubMed

Türetgen, Irfan; Cotuk, Aysin

2007-02-01

Cooling towers have the potential to develop infectious concentrations of Legionella pneumophila. Legionella counts increases where biofilm and warm water temperatures are present. In this study, biofilm associated L. pneumophila and heterotrophic bacteria were compared in terms of material dependence. Model cooling tower system was experimentally infected by L. pneumophila standard strain and monthly monitored. Different materials were tested for a period of 180 days. The lowest L. pneumophila and heterotrophic plate counts were measured on plastic polymers, whereas L. pneumophila and heterotrophic bacteria were accumulated rapidly on galvanized steel surfaces. It can be concluded that selection of plastic polymers, as a manufacturing material, are suitable for recirculating water systems.

Design of a Magnetostrictive-Hydraulic Actuator Considering Nonlinear System Dynamics and Fluid-Structure Coupling

NASA Astrophysics Data System (ADS)

Larson, John Philip

Smart material electro-hydraulic actuators (EHAs) utilize fluid rectification via one-way check valves to amplify the small, high-frequency vibrations of certain smart materials into large motions of a hydraulic cylinder. Although the concept has been demonstrated in previously, the operating frequency of smart material EHA systems has been limited to a small fraction of the available bandwidth of the driver materials. The focus of this work is to characterize and model the mechanical performance of a magnetostrictive EHA considering key system components: rectification valves, smart material driver, and fluid-system components, leading to an improved actuator design relative to prior work. The one-way valves were modeled using 3-D finite element analysis, and their behavior was characterized experimentally by static and dynamic experimental measurement. Taking into account the effect of the fluid and mechanical conditions applied to the valves within the pump, the dynamic response of the valve was quantified and applied to determine rectification bandwidth of different valve configurations. A novel miniature reed valve, designed for a frequency response above 10~kHz, was fabricated and tested within a magnetostrictive EHA. The nonlinear response of the magnetostrictive driver, including saturation and hysteresis effects, was modeled using the Jiles-Atherton approach to calculate the magnetization and the resulting magnetostriction based on the applied field calculated within the rod from Maxwell's equations. The dynamic pressure response of the fluid system components (pumping chamber, hydraulic cylinder, and connecting passages) was measured over a range of input frequencies. For the magnetostrictive EHA tested, the peak performance frequency was found to be limited by the fluid resonances within the system. A lumped-parameter modeling approach was applied to model the overall behavior of a magnetostrictive EHA, incorporating models for the reed valve response, nonlinear magnetostrictive behavior, and fluid behavior (including inertia and compliance). This model was validated by experimental study of a magnetostrictive EHA with a reduced volume manifold. The model was subsequently applied to design a compact magnetostrictive EHA for aircraft applications. Testing of the system shows that the output performance increases with frequency up to a peak unloaded flow rate of 100 cm3/s (6.4 cu in/s) at 1200 Hz, which is a 100% to 500% increase over previous state-of-the-art systems. A blocked differential pressure of 12.1 MPa (1750 psi) was measured, resulting in a power capacity of 310 W, more than 100 W higher than previously reported values. The design and modeling approach used to scale up the performance to create a compact aircraft EHA can also be applied to reduce the size and weight of smart material EHAs for lower power level applications.

Flexible Material Systems Testing

NASA Technical Reports Server (NTRS)

Lin, John K.; Shook, Lauren S.; Ware, Joanne S.; Welch, Joseph V.

2010-01-01

An experimental program has been undertaken to better characterize the stress-strain characteristics of flexible material systems to support a NASA ground test program for inflatable decelerator material technology. A goal of the current study is to investigate experimental methods for the characterization of coated woven material stiffness. This type of experimental mechanics data would eventually be used to define the material inputs of fluid-structure interaction simulation models. The test methodologies chosen for this stress-strain characterization are presented along with the experimental results.

IEEE Photovoltaic Specialists Conference, 20th, Las Vegas, NV, Sept. 26-30, 1988, Conference Record. Volumes 1 & 2

NASA Astrophysics Data System (ADS)

Various papers on photovoltaics are presented. The general topics considered include: amorphous materials and cells; amorphous silicon-based solar cells and modules; amorphous silicon-based materials and processes; amorphous materials characterization; amorphous silicon; high-efficiency single crystal solar cells; multijunction and heterojunction cells; high-efficiency III-V cells; modeling and characterization of high-efficiency cells; LIPS flight experience; space mission requirements and technology; advanced space solar cell technology; space environmental effects and modeling; space solar cell and array technology; terrestrial systems and array technology; terrestrial utility and stand-alone applications and testing; terrestrial concentrator and storage technology; terrestrial stand-alone systems applications; terrestrial systems test and evaluation; terrestrial flatplate and concentrator technology; use of polycrystalline materials; polycrystalline II-VI compound solar cells; analysis of and fabrication procedures for compound solar cells.

Time-varying BRDFs.

PubMed

Sun, Bo; Sunkavalli, Kalyan; Ramamoorthi, Ravi; Belhumeur, Peter N; Nayar, Shree K

2007-01-01

The properties of virtually all real-world materials change with time, causing their bidirectional reflectance distribution functions (BRDFs) to be time varying. However, none of the existing BRDF models and databases take time variation into consideration; they represent the appearance of a material at a single time instance. In this paper, we address the acquisition, analysis, modeling, and rendering of a wide range of time-varying BRDFs (TVBRDFs). We have developed an acquisition system that is capable of sampling a material's BRDF at multiple time instances, with each time sample acquired within 36 sec. We have used this acquisition system to measure the BRDFs of a wide range of time-varying phenomena, which include the drying of various types of paints (watercolor, spray, and oil), the drying of wet rough surfaces (cement, plaster, and fabrics), the accumulation of dusts (household and joint compound) on surfaces, and the melting of materials (chocolate). Analytic BRDF functions are fit to these measurements and the model parameters' variations with time are analyzed. Each category exhibits interesting and sometimes nonintuitive parameter trends. These parameter trends are then used to develop analytic TVBRDF models. The analytic TVBRDF models enable us to apply effects such as paint drying and dust accumulation to arbitrary surfaces and novel materials.

MO-F-CAMPUS-I-03: Tissue Equivalent Material Phantom to Test and Optimize Coherent Scatter Imaging for Tumor Classification

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

Albanese, K; Morris, R; Lakshmanan, M

Purpose: To accurately model different breast geometries using a tissue equivalent phantom, and to classify these tissues in a coherent x-ray scatter imaging system. Methods: A breast phantom has been designed to assess the capability of coded aperture coherent x-ray scatter imaging system to classify different types of breast tissue (adipose, fibroglandular, tumor). The tissue-equivalent phantom was modeled as a hollow plastic cylinder containing multiple cylindrical and spherical inserts that can be positioned, rearranged, or removed to model different breast geometries. Each enclosure can be filled with a tissue-equivalent material and excised human tumors. In this study, beef and lard,more » placed inside 2-mm diameter plastic Nalgene containers, were used as surrogates for fibroglandular and adipose tissue, respectively. The phantom was imaged at 125 kVp, 40 mA for 10 seconds each with a 1-mm pencil beam. The raw data were reconstructed using a model-based reconstruction algorithm and yielded the location and form factor, or momentum transfer (q) spectrum of the materials that were imaged. The measured material form factors were then compared to the ground truth measurements acquired by x-ray diffraction (XRD) imaging. Results: The tissue equivalent phantom was found to accurately model different types of breast tissue by qualitatively comparing our measured form factors to those of adipose and fibroglandular tissue from literature. Our imaging system has been able to define the location and composition of the various materials in the phantom. Conclusion: This work introduces a new tissue equivalent phantom for testing and optimization of our coherent scatter imaging system for material classification. In future studies, the phantom will enable the use of a variety of materials including excised human tissue specimens in evaluating and optimizing our imaging system using pencil- and fan-beam geometries. United States Department of Homeland Security Duke University Medical Center - Department of Radiology Carl E Ravin Advanced Imaging Laboratories Duke University Medical Physics Graduate Program.« less

Modeling and Simulation of Metallurgical Process Based on Hybrid Petri Net

NASA Astrophysics Data System (ADS)

Ren, Yujuan; Bao, Hong

2016-11-01

In order to achieve the goals of energy saving and emission reduction of iron and steel enterprises, an increasing number of modeling and simulation technologies are used to research and analyse metallurgical production process. In this paper, the basic principle of Hybrid Petri net is used to model and analyse the Metallurgical Process. Firstly, the definition of Hybrid Petri Net System of Metallurgical Process (MPHPNS) and its modeling theory are proposed. Secondly, the model of MPHPNS based on material flow is constructed. The dynamic flow of materials and the real-time change of each technological state in metallurgical process are simulated vividly by using this model. The simulation process can implement interaction between the continuous event dynamic system and the discrete event dynamic system at the same level, and play a positive role in the production decision.

Uncertain dynamic analysis for rigid-flexible mechanisms with random geometry and material properties

NASA Astrophysics Data System (ADS)

Wu, Jinglai; Luo, Zhen; Zhang, Nong; Zhang, Yunqing; Walker, Paul D.

2017-02-01

This paper proposes an uncertain modelling and computational method to analyze dynamic responses of rigid-flexible multibody systems (or mechanisms) with random geometry and material properties. Firstly, the deterministic model for the rigid-flexible multibody system is built with the absolute node coordinate formula (ANCF), in which the flexible parts are modeled by using ANCF elements, while the rigid parts are described by ANCF reference nodes (ANCF-RNs). Secondly, uncertainty for the geometry of rigid parts is expressed as uniform random variables, while the uncertainty for the material properties of flexible parts is modeled as a continuous random field, which is further discretized to Gaussian random variables using a series expansion method. Finally, a non-intrusive numerical method is developed to solve the dynamic equations of systems involving both types of random variables, which systematically integrates the deterministic generalized-α solver with Latin Hypercube sampling (LHS) and Polynomial Chaos (PC) expansion. The benchmark slider-crank mechanism is used as a numerical example to demonstrate the characteristics of the proposed method.

A blood circulation model for reference man

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

Leggett, R.W.; Eckerman, K.F.; Williams, L.R.

This paper describes a dynamic blood circulation model that predicts the movement and gradual dispersal of a bolus of material in the circulation after its intravascular injection into an adult human. The main purpose of the model is to improve the dosimetry of internally deposited radionuclides that decay in the circulation to a significant extent. The total blood volume is partitioned into the blood contents of 24 separate organs or tissues, right heart chambers, left heart chambers, pulmonary circulation, arterial outflow to the systemic tissues (aorta and large arteries), and venous return from the systemic tissues (large veins). As amore » compromise between physical reality and computational simplicity, the circulation of blood is viewed as a system of first-order transfers between blood pools, with the delay time depending on the mean transit time across the pool. The model allows consideration of incomplete, tissue-dependent extraction of material during passage through the circulation and return of material from tissues to plasma.« less

Tutor-Student System Dropout Prevention Model.

ERIC Educational Resources Information Center

George, John E.; Prugh, Linda S.

This paper reports on an intensive, highly-structured, one-to-one tutoring system used as a model program. The "Tutor-Student System in Beginning Reading," the basic instructional material for the model program, was developed to train tutors to say and do what the reading specialist normally says and does when teaching reading in a…

Material science lesson from the biological photosystem.

PubMed

Kim, Younghye; Lee, Jun Ho; Ha, Heonjin; Im, Sang Won; Nam, Ki Tae

2016-01-01

Inspired by photosynthesis, artificial systems for a sustainable energy supply are being designed. Each sequential energy conversion process from light to biomass in natural photosynthesis is a valuable model for an energy collection, transport and conversion system. Notwithstanding the numerous lessons of nature that provide inspiration for new developments, the features of natural photosynthesis need to be reengineered to meet man's demands. This review describes recent strategies toward adapting key lessons from natural photosynthesis to artificial systems. We focus on the underlying material science in photosynthesis that combines photosystems as pivotal functional materials and a range of materials into an integrated system. Finally, a perspective on the future development of photosynthesis mimetic energy systems is proposed.

Hierarchical multi-scale approach to validation and uncertainty quantification of hyper-spectral image modeling

NASA Astrophysics Data System (ADS)

Engel, Dave W.; Reichardt, Thomas A.; Kulp, Thomas J.; Graff, David L.; Thompson, Sandra E.

2016-05-01

Validating predictive models and quantifying uncertainties inherent in the modeling process is a critical component of the HARD Solids Venture program [1]. Our current research focuses on validating physics-based models predicting the optical properties of solid materials for arbitrary surface morphologies and characterizing the uncertainties in these models. We employ a systematic and hierarchical approach by designing physical experiments and comparing the experimental results with the outputs of computational predictive models. We illustrate this approach through an example comparing a micro-scale forward model to an idealized solid-material system and then propagating the results through a system model to the sensor level. Our efforts should enhance detection reliability of the hyper-spectral imaging technique and the confidence in model utilization and model outputs by users and stakeholders.

Drug Release Kinetics and Transport Mechanisms of Non-degradable and Degradable Polymeric Delivery Systems

PubMed Central

Fu, Yao; Kao, Weiyuan John

2010-01-01

Importance of the field The advancement in material design and engineering has led to the rapid development of novel materials with increasing complexity and functions. Both non-degradable and degradable polymers have found wide applications in the controlled delivery field. Studies on drug release kinetics provide important information into the function of material systems. To elucidate the detailed transport mechanism and the structure-function relationship of a material system, it is critical to bridge the gap between the macroscopic data and the transport behavior at the molecular level. Areas covered in this review The structure and function information of selected non-degradable and degradable polymers have been collected and summarized from literatures published after 1990s. The release kinetics of selected drug compounds from various material systems will be discussed in case studies. Recent progresses in the mathematical models based on different transport mechanisms will be highlighted. What the reader will gain This article aims to provide an overview of structure-function relationships of selected non-degradable and degradable polymers as drug delivery matrices. Take home message Understanding the structure-function relationship of the material system is key to the successful design of a delivery system for a particular application. Moreover, developing complex polymeric matrices requires more robust mathematical models to elucidate the solute transport mechanisms. PMID:20331353

Fracture on Curved Surfaces

NASA Astrophysics Data System (ADS)

Mitchell, Noah; Koning, Vinzenz; Vitelli, Vincenzo; Irvine, William T. M.

2014-03-01

When an elastic film conforms to a surface with Gaussian curvature, stresses arise in the film. As a result, cracks--typically studied in flat materials--interact with curvature when propagating through the system. Using silicone elastomer sheets that conform to the surface of a Gaussian bump, we find experimental evidence for the deflection of a crack propagating through the material. We interpret our experiments with reference to analytical modeling and simulations of a simplified model system.

Effect of Operating Parameters on a Dual-Stage High Velocity Oxygen Fuel Thermal Spray System

NASA Astrophysics Data System (ADS)

Khan, Mohammed N.; Shamim, Tariq

2014-08-01

High velocity oxygen fuel (HVOF) thermal spray systems are being used to apply coatings to prevent surface degradation. The coatings of temperature sensitive materials such as titanium and copper, which have very low melting points, cannot be applied using a single-stage HVOF system. Therefore, a dual-stage HVOF system has been introduced and modeled computationally. The dual-spray system provides an easy control of particle oxidation by introducing a mixing chamber. In addition to the materials being sprayed, the thermal spray coating quality depends to a large extent on flow behavior of reacting gases and the particle dynamics. The present study investigates the influence of various operating parameters on the performance of a dual-stage thermal spray gun. The objective is to develop a predictive understanding of various parameters. The gas flow field and the free jet are modeled by considering the conservation of mass, momentum, and energy with the turbulence and the equilibrium combustion sub models. The particle phase is decoupled from the gas phase due to very low particle volume fractions. The results demonstrate the advantage of a dual-stage system over a single-stage system especially for the deposition of temperature sensitive materials.

New software to model energy dispersive X-ray diffraction in polycrystalline materials

NASA Astrophysics Data System (ADS)

Ghammraoui, B.; Tabary, J.; Pouget, S.; Paulus, C.; Moulin, V.; Verger, L.; Duvauchelle, Ph.

2012-02-01

Detection of illicit materials, such as explosives or drugs, within mixed samples is a major issue, both for general security and as part of forensic analyses. In this paper, we describe a new code simulating energy dispersive X-ray diffraction patterns in polycrystalline materials. This program, SinFullscat, models diffraction of any object in any diffractometer system taking all physical phenomena, including amorphous background, into account. Many system parameters can be tuned: geometry, collimators (slit and cylindrical), sample properties, X-ray source and detector energy resolution. Good agreement between simulations and experimental data was obtained. Simulations using explosive materials indicated that parameters such as the diffraction angle or the energy resolution of the detector have a significant impact on the diffraction signature of the material inspected. This software will be a convenient tool to test many diffractometer configurations, providing information on the one that best restores the spectral diffraction signature of the materials of interest.

Ballistic Performance Model of Crater Formation in Monolithic, Porous Thermal Protection Systems

NASA Technical Reports Server (NTRS)

Miller, J. E.; Christiansen, E. L.; Deighton, K. D.

2014-01-01

Porous monolithic ablative systems insulate atmospheric reentry vehicles from reentry plasmas generated by atmospheric braking from orbital and exo-orbital velocities. Due to the necessity that these materials create a temperature gradient up to several thousand Kelvin over their thickness, it is important that these materials are near their pristine state prior to reentry. These materials may also be on exposed surfaces to space environment threats like orbital debris and meteoroids leaving a probability that these exposed surfaces will be below their prescribed values. Owing to the typical small size of impact craters in these materials, the local flow fields over these craters and the ablative process afford some margin in thermal protection designs for these locally reduced performance values. In this work, tests to develop ballistic performance models for thermal protection materials typical of those being used on Orion are discussed. A density profile as a function of depth of a typical monolithic ablator and substructure system is shown in Figure 1a.

A nonlinear dynamical system approach for the yielding behaviour of a viscoplastic material.

PubMed

Burghelea, Teodor; Moyers-Gonzalez, Miguel; Sainudiin, Raazesh

2017-03-08

A nonlinear dynamical system model that approximates a microscopic Gibbs field model for the yielding of a viscoplastic material subjected to varying external stresses recently reported in R. Sainudiin, M. Moyers-Gonzalez and T. Burghelea, Soft Matter, 2015, 11(27), 5531-5545 is presented. The predictions of the model are in fair agreement with microscopic simulations and are in very good agreement with the micro-structural semi-empirical model reported in A. M. V. Putz and T. I. Burghelea, Rheol. Acta, 2009, 48, 673-689. With only two internal parameters, the nonlinear dynamical system model captures several key features of the solid-fluid transition observed in experiments: the effect of the interactions between microscopic constituents on the yield point, the abruptness of solid-fluid transition and the emergence of a hysteresis of the micro-structural states upon increasing/decreasing external forces. The scaling behaviour of the magnitude of the hysteresis with the degree of the steadiness of the flow is consistent with previous experimental observations. Finally, the practical usefulness of the approach is demonstrated by fitting a rheological data set measured with an elasto-viscoplastic material.

Capturing the Energy Absorbing Mechanisms of Composite Structures under Crash Loading

NASA Astrophysics Data System (ADS)

Wade, Bonnie

As fiber reinforced composite material systems become increasingly utilized in primary aircraft and automotive structures, the need to understand their contribution to the crashworthiness of the structure is of great interest to meet safety certification requirements. The energy absorbing behavior of a composite structure, however, is not easily predicted due to the great complexity of the failure mechanisms that occur within the material. Challenges arise both in the experimental characterization and in the numerical modeling of the material/structure combination. At present, there is no standardized test method to characterize the energy absorbing capability of composite materials to aide crashworthy structural design. In addition, although many commercial finite element analysis codes exist and offer a means to simulate composite failure initiation and propagation, these models are still under development and refinement. As more metallic structures are replaced by composite structures, the need for both experimental guidelines to characterize the energy absorbing capability of a composite structure, as well as guidelines for using numerical tools to simulate composite materials in crash conditions has become a critical matter. This body of research addresses both the experimental characterization of the energy absorption mechanisms occurring in composite materials during crushing, as well as the numerical simulation of composite materials undergoing crushing. In the experimental investigation, the specific energy absorption (SEA) of a composite material system is measured using a variety of test element geometries, such as corrugated plates and tubes. Results from several crush experiments reveal that SEA is not a constant material property for laminated composites, and varies significantly with the geometry of the test specimen used. The variation of SEA measured for a single material system requires that crush test data must be generated for a range of different test geometries in order to define the range of its energy absorption capability. Further investigation from the crush tests has led to the development of a direct link between geometric features of the crush specimen and its resulting SEA. Through micrographic analysis, distinct failure modes are shown to be guided by the geometry of the specimen, and subsequently are shown to directly influence energy absorption. A new relationship between geometry, failure mode, and SEA has been developed. This relationship has allowed for the reduction of the element-level crush testing requirement to characterize the composite material energy absorption capability. In the numerical investigation, the LS-DYNA composite material model MAT54 is selected for its suitability to model composite materials beyond failure determination, as required by crush simulation, and its capability to remain within the scope of ultimately using this model for large-scale crash simulation. As a result of this research, this model has been thoroughly investigated in depth for its capacity to simulate composite materials in crush, and results from several simulations of the element-level crush experiments are presented. A modeling strategy has been developed to use MAT54 for crush simulation which involves using the experimental data collected from the coupon- and element-level crush tests to directly calibrate the crush damage parameter in MAT54 such that it may be used in higher-level simulations. In addition, the source code of the material model is modified to improve upon its capability. The modifications include improving the elastic definition such that the elastic response to multi-axial load cases can be accurately portrayed simultaneously in each element, which is a capability not present in other composite material models. Modifications made to the failure determination and post-failure model have newly emphasized the post-failure stress degradation scheme rather than the failure criterion which is traditionally considered the most important composite material model definition for crush simulation. The modification efforts have also validated the use of the MAT54 failure criterion and post-failure model for crash modeling when its capabilities and limitations are well understood, and for this reason guidelines for using MAT54 for composite crush simulation are presented. This research has effectively (a) developed and demonstrated a procedure that defines a set of experimental crush results that characterize the energy absorption capability of a composite material system, (b) used the experimental results in the development and refinement of a composite material model for crush simulation, (c) explored modifying the material model to improve its use in crush modeling, and (d) provided experimental and modeling guidelines for composite structures under crush at the element-level in the scope of the Building Block Approach.

Reference-material system for estimating health and environmental risks of selected material cycles and energy systems

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

Crowther, M.A.; Moskowitz, P.D.

1981-07-01

Sample analyses and detailed documentation are presented for a Reference Material System (RMS) to estimate health and environmental risks of different material cycles and energy systems. Data inputs described include: end-use material demands, efficiency coefficients, environmental emission coefficients, fuel demand coefficients, labor productivity estimates, and occupational health and safety coefficients. Application of this model permits analysts to estimate fuel use (e.g., Btu), occupational risk (e.g., fatalities), and environmental emissions (e.g., sulfur oxide) for specific material trajectories or complete energy systems. Model uncertainty is quantitatively defined by presenting a range of estimates for each data input. Systematic uncertainty not quantified relatesmore » to the boundaries chosen for analysis and reference system specification. Although the RMS can be used to analyze material system impacts for many different energy technologies, it was specifically used to examine the health and environmental risks of producing the following four types of photovoltaic devices: silicon n/p single-crystal cells produced by a Czochralski process; silicon metal/insulator/semiconductor (MIS) cells produced by a ribbon-growing process; cadmium sulfide/copper sulfide backwall cells produced by a spray deposition process; and gallium arsenide cells with 500X concentrator produced by a modified Czochralski process. Emission coefficients for particulates, sulfur dioxide and nitrogen dioxide; solid waste; total suspended solids in water; and, where applicable, air and solid waste residuals for arsenic, cadmium, gallium, and silicon are examined and presented. Where data are available the coefficients for particulates, sulfur oxides, and nitrogen oxides include both process and on-site fuel-burning emissions.« less

An Investigation of Reliability Models for Ceramic Matrix Composites and their Implementation into Finite Element Codes

NASA Technical Reports Server (NTRS)

Duffy, Stephen F.

1998-01-01

The development of modeling approaches for the failure analysis of ceramic-based material systems used in high temperature environments was the primary objective of this research effort. These materials have the potential to support many key engineering technologies related to the design of aeropropulsion systems. Monolithic ceramics exhibit a number of useful properties such as retention of strength at high temperatures, chemical inertness, and low density. However, the use of monolithic ceramics has been limited by their inherent brittleness and a large variation in strength. This behavior has motivated material scientists to reinforce the monolithic material with a ceramic fiber. The addition of a second ceramic phase with an optimized interface increases toughness and marginally increases strength. The primary purpose of the fiber is to arrest crack growth, not to increase strength. The material systems of interest in this research effort were laminated ceramic matrix composites, as well as two- and three- dimensional fabric reinforced ceramic composites. These emerging composite systems can compete with metals in many demanding applications. However, the ongoing metamorphosis of ceramic composite material systems, and the lack of standardized design data has in the past tended to minimize research efforts related to structural analysis. Many structural components fabricated from ceramic matrix composites (CMC) have been designed by "trial and error." The justification for this approach lies in the fact that during the initial developmental phases for a material system fabrication issues are paramount. Emphasis is placed on demonstrating feasibility rather than fully understanding the processes controlling mechanical behavior. This is understandable during periods of rapid improvements in material properties for any composite system. But to avoid the ad hoc approach, the analytical methods developed under this effort can be used to develop rational structural design protocols.

Potential Nucleosynthetic Sources of the Titanium Isotope Variations in Solar System Materials

NASA Astrophysics Data System (ADS)

Williams, N. H.; Fehr, M. A.; Akram, W. M.; Parkinson, I. J.; Schönbächler, M.

2012-09-01

The Ti isotope ratios of a comprehensive sample suite of solar system material were analyzed by MC-ICPMS. This data was then used to evaluate nucleosynthetic models for the source of isotopic correlations observed in Iron group elements and Zr.

Theoretical Investigations of Well-Defined Graphene Nanostructures: Catalysis, Spectroscopy, and Development of Novel Fragment-Based Models

NASA Astrophysics Data System (ADS)

Noffke, Benjamin W.

Carbon materials have the potential to replace some precious metals in renewable energy applications. These materials are particularly attractive because of the elemental abundance and relatively low nuclear mass of carbon, implying economically feasible and lightweight materials. Targeted design of carbon materials is hindered by the lack of fundamental understanding that is required to tailor their properties for the desired application. However, most available synthetic methods to create carbon materials involve harsh conditions that limit the control of the resulting structure. Without a well-defined structure, the system is too complex and fundamental studies cannot be definitive. This work seeks to gain fundamental understanding through the development and application of efficient computational models for these systems, in conjunction with experiments performed on soluble, well-defined graphene nanostructures prepared by our group using a bottom-up synthetic approach. Theory is used to determine mechanistic details for well-defined carbon systems in applications of catalysis and electrochemical transformations. The resulting computational models do well to explain previous observations of carbon materials and provide suggestions for future directions. However, as the system size of the nanostructures gets larger, the computational cost can become prohibitive. To reduce the computational scaling of quantum chemical calculations, a new fragmentation scheme has been developed that addresses the challenges of fragmenting conjugated molecules. By selecting fragments that retain important structural characteristics in graphene, a more efficient method is achieved. The new method paves the way for an automated, systematic fragmentation scheme of graphene molecules.

Modeling and additive manufacturing of bio-inspired composites with tunable fracture mechanical properties.

PubMed

Dimas, Leon S; Buehler, Markus J

2014-07-07

Flaws, imperfections and cracks are ubiquitous in material systems and are commonly the catalysts of catastrophic material failure. As stresses and strains tend to concentrate around cracks and imperfections, structures tend to fail far before large regions of material have ever been subjected to significant loading. Therefore, a major challenge in material design is to engineer systems that perform on par with pristine structures despite the presence of imperfections. In this work we integrate knowledge of biological systems with computational modeling and state of the art additive manufacturing to synthesize advanced composites with tunable fracture mechanical properties. Supported by extensive mesoscale computer simulations, we demonstrate the design and manufacturing of composites that exhibit deformation mechanisms characteristic of pristine systems, featuring flaw-tolerant properties. We analyze the results by directly comparing strain fields for the synthesized composites, obtained through digital image correlation (DIC), and the computationally tested composites. Moreover, we plot Ashby diagrams for the range of simulated and experimental composites. Our findings show good agreement between simulation and experiment, confirming that the proposed mechanisms have a significant potential for vastly improving the fracture response of composite materials. We elucidate the role of stiffness ratio variations of composite constituents as an important feature in determining the composite properties. Moreover, our work validates the predictive ability of our models, presenting them as useful tools for guiding further material design. This work enables the tailored design and manufacturing of composites assembled from inferior building blocks, that obtain optimal combinations of stiffness and toughness.

Vision 2040: A Roadmap for Integrated, Multiscale Modeling and Simulation of Materials and Systems

NASA Technical Reports Server (NTRS)

Liu, Xuan; Furrer, David; Kosters, Jared; Holmes, Jack

2018-01-01

Over the last few decades, advances in high-performance computing, new materials characterization methods, and, more recently, an emphasis on integrated computational materials engineering (ICME) and additive manufacturing have been a catalyst for multiscale modeling and simulation-based design of materials and structures in the aerospace industry. While these advances have driven significant progress in the development of aerospace components and systems, that progress has been limited by persistent technology and infrastructure challenges that must be overcome to realize the full potential of integrated materials and systems design and simulation modeling throughout the supply chain. As a result, NASA's Transformational Tools and Technology (TTT) Project sponsored a study (performed by a diverse team led by Pratt & Whitney) to define the potential 25-year future state required for integrated multiscale modeling of materials and systems (e.g., load-bearing structures) to accelerate the pace and reduce the expense of innovation in future aerospace and aeronautical systems. This report describes the findings of this 2040 Vision study (e.g., the 2040 vision state; the required interdependent core technical work areas, Key Element (KE); identified gaps and actions to close those gaps; and major recommendations) which constitutes a community consensus document as it is a result of over 450 professionals input obtain via: 1) four society workshops (AIAA, NAFEMS, and two TMS), 2) community-wide survey, and 3) the establishment of 9 expert panels (one per KE) consisting on average of 10 non-team members from academia, government and industry to review, update content, and prioritize gaps and actions. The study envisions the development of a cyber-physical-social ecosystem comprised of experimentally verified and validated computational models, tools, and techniques, along with the associated digital tapestry, that impacts the entire supply chain to enable cost-effective, rapid, and revolutionary design of fit-for-purpose materials, components, and systems. Although the vision focused on aeronautics and space applications, it is believed that other engineering communities (e.g., automotive, biomedical, etc.) can benefit as well from the proposed framework with only minor modifications. Finally, it is TTT's hope and desire that this vision provides the strategic guidance to both public and private research and development decision makers to make the proposed 2040 vision state a reality and thereby provide a significant advancement in the United States global competitiveness.

Modeling and Analysis of the Reverse Water Gas Shift Process for In-Situ Propellant Production

NASA Technical Reports Server (NTRS)

Whitlow, Jonathan E.

2000-01-01

This report focuses on the development of mathematical models and simulation tools developed for the Reverse Water Gas Shift (RWGS) process. This process is a candidate technology for oxygen production on Mars under the In-Situ Propellant Production (ISPP) project. An analysis of the RWGS process was performed using a material balance for the system. The material balance is very complex due to the downstream separations and subsequent recycle inherent with the process. A numerical simulation was developed for the RWGS process to provide a tool for analysis and optimization of experimental hardware, which will be constructed later this year at Kennedy Space Center (KSC). Attempts to solve the material balance for the system, which can be defined by 27 nonlinear equations, initially failed. A convergence scheme was developed which led to successful solution of the material balance, however the simplified equations used for the gas separation membrane were found insufficient. Additional more rigorous models were successfully developed and solved for the membrane separation. Sample results from these models are included in this report, with recommendations for experimental work needed for model validation.

Zeolite formation from coal fly ash and heavy metal ion removal characteristics of thus-obtained Zeolite X in multi-metal systems.

PubMed

Jha, Vinay Kumar; Nagae, Masahiro; Matsuda, Motohide; Miyake, Michihiro

2009-06-01

Zeolitic materials have been prepared from coal fly ash as well as from a SiO(2)-Al(2)O(3) system upon NaOH fusion treatment, followed by subsequent hydrothermal processing at various NaOH concentrations and reaction times. During the preparation process, the starting material initially decomposed to an amorphous form, and the nucleation process of the zeolite began. The carbon content of the starting material influenced the formation of the zeolite by providing an active surface for nucleation. Zeolite A (Na-A) was transformed into zeolite X (Na-X) with increasing NaOH concentration and reaction time. The adsorption isotherms of the obtained Na-X based on the characteristics required to remove heavy ions such as Ni(2+), Cu(2+), Cd(2+) and Pb(2+) were examined in multi-metal systems. Thus obtained experimental data suggests that the Langmuir and Freundlich models are more accurate compared to the Dubinin-Kaganer-Radushkevich (DKR) model. However, the sorption energy obtained from the DKR model was helpful in elucidating the mechanism of the sorption process. Further, in going from a single- to multi-metal system, the degree of fitting for the Freundlich model compared with the Langmuir model was favored due to its basic assumption of a heterogeneity factor. The Extended-Langmuir model may be used in multi-metal systems, but gives a lower value for equilibrium sorption compared with the Langmuir model.

Centralized versus decentralized decision-making for recycled material flows.

PubMed

Hong, I-Hsuan; Ammons, Jane C; Realff, Matthew J

2008-02-15

A reverse logistics system is a network of transportation logistics and processing functions that collect, consolidate, refurbish, and demanufacture end-of-life products. This paper examines centralized and decentralized models of decision-making for material flows and associated transaction prices in reverse logistics networks. We compare the application of a centralized model for planning reverse production systems, where a single planner is acquainted with all of the system information and has the authority to determine decision variables for the entire system, to a decentralized approach. In the decentralized approach, the entities coordinate between tiers of the system using a parametrized flow function and compete within tiers based on reaching a price equilibrium. We numerically demonstrate the increase in the total net profit of the centralized system relative to the decentralized one. This implies that one may overestimate the system material flows and profit if the system planner utilizes a centralized viewto predict behaviors of independent entities in the system and that decentralized contract mechanisms will require careful design to avoid losses in the efficiency and scope of these systems.

Microfabrication of hierarchical structures for engineered mechanical materials

NASA Astrophysics Data System (ADS)

Vera Canudas, Marc

Materials found in nature present, in some cases, unique properties from their constituents that are of great interest in engineered materials for applications ranging from structural materials for the construction of bridges, canals and buildings to the fabrication of new lightweight composites for airplane and automotive bodies, to protective thin film coatings, amongst other fields. Research in the growing field of biomimetic materials indicates that the micro-architectures present in natural materials are critical to their macroscopic mechanical properties. A better understanding of the effect that structure and hierarchy across scales have on the material properties will enable engineered materials with enhanced properties. At the moment, very few theoretical models predict mechanical properties of simple materials based on their microstructures. Moreover these models are based on observations from complex biological systems. One way to overcome this challenge is through the use of microfabrication techniques to design and fabricate simple materials, more appropriate for the study of hierarchical organizations and microstructured materials. Arrays of structures with controlled geometry and dimension can be designed and fabricated at different length scales, ranging from a few hundred nanometers to centimeters, in order to mimic similar systems found in nature. In this thesis, materials have been fabricated in order to gain fundamental insight into the complex hierarchical materials found in nature and to engineer novel materials with enhanced mechanical properties. The materials fabricated here were mechanically characterized and compared to simple mechanics models to describe their behavior with the goal of applying the knowledge acquired to the design and synthesis of future engineered materials with novel properties.

Accelerated optical polymer aging studies for LED luminaire applications

NASA Astrophysics Data System (ADS)

Estupiñán, Edgar; Wendling, Peter; Kostrun, Marijan; Garner, Richard

2013-09-01

There is a need in the lighting industry to design and implement accelerated aging methods that accurately simulate the aging process of LED luminaire components. In response to this need, we have built a flexible and reliable system to study the aging characteristics of optical polymer materials, and we have employed it to study a commercially available LED luminaire diffuser made of PMMA. The experimental system consists of a "Blue LED Emitter" and a working surface. Both the temperatures of the samples and the optical powers of the LEDs are appropriately characterized in the system. Several accelerated aging experiments are carried out at different temperatures and optical powers over a 90 hour period and the measured transmission values are used as inputs to a degradation model derived using plausibility arguments. This model seems capable of predicting the behavior of the material as a function of time, temperature and optical power. The model satisfactorily predicts the measured transmission values of diffusers aged in luminaires at two different times and thus can be used to make application recommendations for this material. Specifically, at 35000 hours (the manufacturer's stated life of the luminaire) and at the typical operational temperature of the diffuser, the model predicts a transmission loss of only a few percent over the original transmission of the material at 450 nm, which renders this material suitable for this application.

Modeling the Relationship Between Porosity and Permeability During Oxidation of Ablative Materials

NASA Technical Reports Server (NTRS)

Thornton, John M.; Panerai, Francesco; Ferguson, Joseph C.; Borner, Arnaud; Mansour, Nagi N.

2017-01-01

The ablative materials used in thermal protection systems (TPS) undergo oxidation during atmospheric entry which leads to an in-depth change in both permeability and porosity. These properties have a significant affect on heat transfer in a TPS during entry. X-ray micro-tomography has provided 3D images capturing the micro-structure of TPS materials. In this study, we use micro-tomography based simulations to create high-fidelity models relating permeability to porosity during oxidation of FiberForm, the carbon fiber preform of the Phenolic Impregnated Carbon Ablator (PICA) often used as a TPS material. The goal of this study is to inform full-scale models and reduce uncertainty in TPS modeling.

An Integrated Crustal Dynamics Simulator

NASA Astrophysics Data System (ADS)

Xing, H. L.; Mora, P.

2007-12-01

Numerical modelling offers an outstanding opportunity to gain an understanding of the crustal dynamics and complex crustal system behaviour. This presentation provides our long-term and ongoing effort on finite element based computational model and software development to simulate the interacting fault system for earthquake forecasting. A R-minimum strategy based finite-element computational model and software tool, PANDAS, for modelling 3-dimensional nonlinear frictional contact behaviour between multiple deformable bodies with the arbitrarily-shaped contact element strategy has been developed by the authors, which builds up a virtual laboratory to simulate interacting fault systems including crustal boundary conditions and various nonlinearities (e.g. from frictional contact, materials, geometry and thermal coupling). It has been successfully applied to large scale computing of the complex nonlinear phenomena in the non-continuum media involving the nonlinear frictional instability, multiple material properties and complex geometries on supercomputers, such as the South Australia (SA) interacting fault system, South California fault model and Sumatra subduction model. It has been also extended and to simulate the hot fractured rock (HFR) geothermal reservoir system in collaboration of Geodynamics Ltd which is constructing the first geothermal reservoir system in Australia and to model the tsunami generation induced by earthquakes. Both are supported by Australian Research Council.

Mathematical model of bone drilling for virtual surgery system

NASA Astrophysics Data System (ADS)

Alaytsev, Innokentiy K.; Danilova, Tatyana V.; Manturov, Alexey O.; Mareev, Gleb O.; Mareev, Oleg V.

2018-04-01

The bone drilling is an essential part of surgeries in ENT and Dentistry. A proper training of drilling machine handling skills is impossible without proper modelling of the drilling process. Utilization of high precision methods like FEM is limited due to the requirement of 1000 Hz update rate for haptic feedback. The study presents a mathematical model of the drilling process that accounts the properties of materials, the geometry and the rotation rate of a burr to compute the removed material volume. The simplicity of the model allows for integrating it in the high-frequency haptic thread. The precision of the model is enough for a virtual surgery system targeted on the training of the basic surgery skills.

Administrative Decision Making and Resource Allocation.

ERIC Educational Resources Information Center

Sardy, Susan; Sardy, Hyman

This paper considers selected aspects of the systems analysis of administrative decisionmaking regarding resource allocations in an educational system. A model of the instructional materials purchase system is presented. The major components of this model are: environment, input, decision process, conversion structure, conversion process, output,…

The utilization of nonterrestrial materials. [resources for solar power satellite construction

NASA Technical Reports Server (NTRS)

1981-01-01

The development of research and technology programs on the user of nonterrestrial materials for space applications was considered with emphasis on the space power satellite system as a model of large space systems for which the use of nonterrestrial materials may be economically viable. Sample topics discussed include the mining of raw materials and the conversion of raw materials into useful products. These topics were considered against a background of the comparative costs of using terrestrial materials. Exploratory activities involved in the preparation of a nonterrestrial materials utilization program, and the human factors involved were also addressed. Several recommendations from the workshop are now incorporated in NASA activities.

Heat transfer and phase transitions of water in multi-layer cryolithozone-surface systems

NASA Astrophysics Data System (ADS)

Khabibullin, I. L.; Nigametyanova, G. A.; Nazmutdinov, F. F.

2018-01-01

A mathematical model for calculating the distribution of temperature and the dynamics of the phase transfor-mations of water in multilayer systems on permafrost-zone surface is proposed. The model allows one to perform calculations in the annual cycle, taking into account the distribution of temperature on the surface in warm and cold seasons. A system involving four layers, a snow or land cover, a top layer of soil, a layer of thermal-insulation materi-al, and a mineral soil, is analyzed. The calculations by the model allow one to choose the optimal thickness and com-position of the layers which would ensure the stability of structures built on the permafrost-zone surface.

Nanoscale alloys and core-shell materials: Model predictions of the nanostructure and mechanical properties

NASA Astrophysics Data System (ADS)

Zhurkin, E. E.; van Hoof, T.; Hou, M.

2007-06-01

Atomic scale modeling methods are used to investigate the relationship between the properties of clusters of nanometer size and the materials that can be synthesized by assembling them. The examples of very different bimetallic systems are used. The first one is the Ni3Al ordered alloy and the second is the AgCo core-shell system. While the Ni3Al cluster assembled materials modeling is already reported in our previous work, here we focus on the prediction of new materials synthesized by low energy deposition and accumulation of AgCo clusters. It is found that the core-shell structure is preserved by deposition with energies typical of low energy cluster beam deposition, although deposition may induce substantial cluster deformation. In contrast with Ni3Al deposited cluster assemblies, no grain boundary between clusters survives deposition and the silver shells merge into a noncrystalline system with a layered structure, in which the fcc Co grains are embedded. To our knowledge, such a material has not yet been synthesized experimentally. Mechanical properties are discussed by confronting the behaviors of Ni3Al and AgCo under the effect of a uniaxial load. To this end, a molecular dynamics scheme is established in view of circumventing rate effects inherent to short term modeling and thereby allowing to examine large plastic deformation mechanisms. Although the mechanisms are different, large plastic deformations are found to improve the elastic properties of both the Ni3Al and AgCo systems by stabilizing their nanostructure. Beyond this improvement, when the load is further increased, the Ni3Al system displays reduced ductility while the AgCo system is superplastic. The superplasticity is explained by the fact that the layered structure of the Ag system is not modified by the deformation. Some coalescence of the Co grains is identified as a geometrical effect and is suggested to be a limiting factor to superplasticity.

Laboratory Modelling of Volcano Plumbing Systems: a review

NASA Astrophysics Data System (ADS)

Galland, Olivier; Holohan, Eoghan P.; van Wyk de Vries, Benjamin; Burchardt, Steffi

2015-04-01

Earth scientists have, since the XIX century, tried to replicate or model geological processes in controlled laboratory experiments. In particular, laboratory modelling has been used study the development of volcanic plumbing systems, which sets the stage for volcanic eruptions. Volcanic plumbing systems involve complex processes that act at length scales of microns to thousands of kilometres and at time scales from milliseconds to billions of years, and laboratory models appear very suitable to address them. This contribution reviews laboratory models dedicated to study the dynamics of volcano plumbing systems (Galland et al., Accepted). The foundation of laboratory models is the choice of relevant model materials, both for rock and magma. We outline a broad range of suitable model materials used in the literature. These materials exhibit very diverse rheological behaviours, so their careful choice is a crucial first step for the proper experiment design. The second step is model scaling, which successively calls upon: (1) the principle of dimensional analysis, and (2) the principle of similarity. The dimensional analysis aims to identify the dimensionless physical parameters that govern the underlying processes. The principle of similarity states that "a laboratory model is equivalent to his geological analogue if the dimensionless parameters identified in the dimensional analysis are identical, even if the values of the governing dimensional parameters differ greatly" (Barenblatt, 2003). The application of these two steps ensures a solid understanding and geological relevance of the laboratory models. In addition, this procedure shows that laboratory models are not designed to exactly mimic a given geological system, but to understand underlying generic processes, either individually or in combination, and to identify or demonstrate physical laws that govern these processes. From this perspective, we review the numerous applications of laboratory models to understand the distinct key features of volcanic plumbing systems: dykes, cone sheets, sills, laccoliths, caldera-related structures, ground deformation, magma/fault interactions, and explosive vents. Barenblatt, G.I., 2003. Scaling. Cambridge University Press, Cambridge. Galland, O., Holohan, E.P., van Wyk de Vries, B., Burchardt, S., Accepted. Laboratory modelling of volcanic plumbing systems: A review, in: Breitkreuz, C., Rocchi, S. (Eds.), Laccoliths, sills and dykes: Physical geology of shallow level magmatic systems. Springer.

Computational Electromagnetic Modeling of SansEC(Trade Mark) Sensors

NASA Technical Reports Server (NTRS)

Smith, Laura J.; Dudley, Kenneth L.; Szatkowski, George N.

2011-01-01

This paper describes the preliminary effort to apply computational design tools to aid in the development of an electromagnetic SansEC resonant sensor composite materials damage detection system. The computational methods and models employed on this research problem will evolve in complexity over time and will lead to the development of new computational methods and experimental sensor systems that demonstrate the capability to detect, diagnose, and monitor the damage of composite materials and structures on aerospace vehicles.

A two-fluid model for avalanche and debris flows.

PubMed

Pitman, E Bruce; Le, Long

2005-07-15

Geophysical mass flows--debris flows, avalanches, landslides--can contain O(10(6)-10(10)) m(3) or more of material, often a mixture of soil and rocks with a significant quantity of interstitial fluid. These flows can be tens of meters in depth and hundreds of meters in length. The range of scales and the rheology of this mixture presents significant modelling and computational challenges. This paper describes a depth-averaged 'thin layer' model of geophysical mass flows containing a mixture of solid material and fluid. The model is derived from a 'two-phase' or 'two-fluid' system of equations commonly used in engineering research. Phenomenological modelling and depth averaging combine to yield a tractable set of equations, a hyperbolic system that describes the motion of the two constituent phases. If the fluid inertia is small, a reduced model system that is easier to solve may be derived.

A discrete model to study reaction-diffusion-mechanics systems.

PubMed

Weise, Louis D; Nash, Martyn P; Panfilov, Alexander V

2011-01-01

This article introduces a discrete reaction-diffusion-mechanics (dRDM) model to study the effects of deformation on reaction-diffusion (RD) processes. The dRDM framework employs a FitzHugh-Nagumo type RD model coupled to a mass-lattice model, that undergoes finite deformations. The dRDM model describes a material whose elastic properties are described by a generalized Hooke's law for finite deformations (Seth material). Numerically, the dRDM approach combines a finite difference approach for the RD equations with a Verlet integration scheme for the equations of the mass-lattice system. Using this framework results were reproduced on self-organized pacemaking activity that have been previously found with a continuous RD mechanics model. Mechanisms that determine the period of pacemakers and its dependency on the medium size are identified. Finally it is shown how the drift direction of pacemakers in RDM systems is related to the spatial distribution of deformation and curvature effects.

A Discrete Model to Study Reaction-Diffusion-Mechanics Systems

PubMed Central

Weise, Louis D.; Nash, Martyn P.; Panfilov, Alexander V.

2011-01-01

This article introduces a discrete reaction-diffusion-mechanics (dRDM) model to study the effects of deformation on reaction-diffusion (RD) processes. The dRDM framework employs a FitzHugh-Nagumo type RD model coupled to a mass-lattice model, that undergoes finite deformations. The dRDM model describes a material whose elastic properties are described by a generalized Hooke's law for finite deformations (Seth material). Numerically, the dRDM approach combines a finite difference approach for the RD equations with a Verlet integration scheme for the equations of the mass-lattice system. Using this framework results were reproduced on self-organized pacemaking activity that have been previously found with a continuous RD mechanics model. Mechanisms that determine the period of pacemakers and its dependency on the medium size are identified. Finally it is shown how the drift direction of pacemakers in RDM systems is related to the spatial distribution of deformation and curvature effects. PMID:21804911

Improvements to constitutive material model for fabrics

NASA Astrophysics Data System (ADS)

Morea, Mihai I.

2011-12-01

The high strength to weight ratio of woven fabric offers a cost effective solution to be used in a containment system for aircraft propulsion engines. Currently, Kevlar is the only Federal Aviation Administration (FAA) approved fabric for usage in systems intended to mitigate fan blade-out events. This research builds on an earlier constitutive model of Kevlar 49 fabric developed at Arizona State University (ASU) with the addition of new and improved modeling details. Latest stress strain experiments provided new and valuable data used to modify the material model post peak behavior. These changes reveal an overall improvement of the Finite Element (FE) model's ability to predict experimental results. First, the steel projectile is modeled using Johnson-Cook material model and provides a more realistic behavior in the FE ballistic models. This is particularly noticeable when comparing FE models with laboratory tests where large deformations in projectiles are observed. Second, follow-up analysis of the results obtained through the new picture frame tests conducted at ASU provides new values for the shear moduli and corresponding strains. The new approach for analysis of data from picture frame tests combines digital image analysis and a two-level factorial optimization formulation. Finally, an additional improvement in the material model for Kevlar involves checking the convergence at variation of mesh density of fabrics. The study performed and described herein shows the converging trend, therefore validating the FE model.

Review of Soil Models and Their Implementation in Multibody System Algorithms

DTIC Science & Technology

2012-02-01

models for use with ABAQUS . The constitutive models of the user defined materials can be programmed in the user subroutine UMAT. Many user defined...mechanical characteristics of mildly or moderately expansive unsaturated soils. As originally proposed by Alonso, utilizing a critical state framework...review of some of these programs is presented. ABAQUS ABAQUS is a popular FE analysis program that contains a wide variety of material models and

Gravity and Granular Materials

NASA Technical Reports Server (NTRS)

Behringer, R. P.; Hovell, Daniel; Kondic, Lou; Tennakoon, Sarath; Veje, Christian

1999-01-01

We describe experiments that probe a number of different types of granular flow where either gravity is effectively eliminated or it is modulated in time. These experiments include the shaking of granular materials both vertically and horizontally, and the shearing of a 2D granular material. For the shaken system, we identify interesting dynamical phenomena and relate them to standard simple friction models. An interesting application of this set of experiments is to the mixing of dissimilar materials. For the sheared system we identify a new kind of dynamical phase transition.

Engineered Barrier System: Physical and Chemical Environment

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

P. Dixon

2004-04-26

The conceptual and predictive models documented in this Engineered Barrier System: Physical and Chemical Environment Model report describe the evolution of the physical and chemical conditions within the waste emplacement drifts of the repository. The modeling approaches and model output data will be used in the total system performance assessment (TSPA-LA) to assess the performance of the engineered barrier system and the waste form. These models evaluate the range of potential water compositions within the emplacement drifts, resulting from the interaction of introduced materials and minerals in dust with water seeping into the drifts and with aqueous solutions forming bymore » deliquescence of dust (as influenced by atmospheric conditions), and from thermal-hydrological-chemical (THC) processes in the drift. These models also consider the uncertainty and variability in water chemistry inside the drift and the compositions of introduced materials within the drift. This report develops and documents a set of process- and abstraction-level models that constitute the engineered barrier system: physical and chemical environment model. Where possible, these models use information directly from other process model reports as input, which promotes integration among process models used for total system performance assessment. Specific tasks and activities of modeling the physical and chemical environment are included in the technical work plan ''Technical Work Plan for: In-Drift Geochemistry Modeling'' (BSC 2004 [DIRS 166519]). As described in the technical work plan, the development of this report is coordinated with the development of other engineered barrier system analysis model reports.« less

Hierarchical Multi-Scale Approach To Validation and Uncertainty Quantification of Hyper-Spectral Image Modeling

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

Engel, David W.; Reichardt, Thomas A.; Kulp, Thomas J.

Validating predictive models and quantifying uncertainties inherent in the modeling process is a critical component of the HARD Solids Venture program [1]. Our current research focuses on validating physics-based models predicting the optical properties of solid materials for arbitrary surface morphologies and characterizing the uncertainties in these models. We employ a systematic and hierarchical approach by designing physical experiments and comparing the experimental results with the outputs of computational predictive models. We illustrate this approach through an example comparing a micro-scale forward model to an idealized solid-material system and then propagating the results through a system model to the sensormore » level. Our efforts should enhance detection reliability of the hyper-spectral imaging technique and the confidence in model utilization and model outputs by users and stakeholders.« less

The localized quantum vacuum field

NASA Astrophysics Data System (ADS)

Dragoman, D.

2008-03-01

A model for the localized quantum vacuum is proposed in which the zero-point energy (ZPE) of the quantum electromagnetic field originates in energy- and momentum-conserving transitions of material systems from their ground state to an unstable state with negative energy. These transitions are accompanied by emissions and re-absorptions of real photons, which generate a localized quantum vacuum in the neighborhood of material systems. The model could help resolve the cosmological paradox associated with the ZPE of electromagnetic fields, while reclaiming quantum effects associated with quantum vacuum such as the Casimir effect and the Lamb shift. It also offers a new insight into the Zitterbewegung of material particles.

Dynamic Triple-Mode Sorption and Outgassing in Materials.

PubMed

Sharma, Hom N; Harley, Stephen J; Sun, Yunwei; Glascoe, Elizabeth A

2017-06-07

Moisture uptake and outgassing can be detrimental to a system by altering the chemical and mechanical properties of materials within the system over time. In this work, we conducted isotherm experiments to investigate dynamic moisture sorption and desorption in markedly different materials, i.e., a polymeric material, Sylgard-184 and a ceramic aluminosilicate material, Zircar RS-1200, at different temperatures (30 °C-70 °C) by varying the water activity (0.0-0.90). Sylgard-184 showed a linear sorption and outgassing behavior with no-hysteresis over the entire temperature and water activity range considered here. Whereas, the sorption and outgassing of Zircar RS-1200 was highly non-linear with significant hysteresis, especially at higher water activities, at all temperatures considered here. The type of hysteresis suggested the presence of mesopores in Zircar RS-1200, whereas the lack of hysteresis in Sylgard-184 indicates that it has a nonporous structure. A diffusion model coupled with a dynamic, triple-mode sorption (Langmuir, Henry, and pooling modes) model employed in this study matched our experimental data very well and provides mechanistic insight into the processes. Our triple-mode sorption model was adaptive enough to (1) model these distinctly different materials and (2) predict sorption and outgassing under conditions that are distinctly different from the parameterization experiments.

Dynamic Triple-Mode Sorption and Outgassing in Materials

DOE PAGES

Sharma, Hom N.; Harley, Stephen J.; Sun, Yunwei; ...

2017-06-07

Moisture uptake and outgassing can be detrimental to a system by altering the chemical and mechanical properties of materials within the system over time. In this work, we conducted isotherm experiments to investigate dynamic moisture sorption and desorption in markedly different materials, i.e., a polymeric material, Sylgard-184 and a ceramic aluminosilicate material, Zircar RS-1200, at different temperatures (30 °C–70 °C) by varying the water activity (0.0–0.90). Sylgard-184 showed a linear sorption and outgassing behavior with no-hysteresis over the entire temperature and water activity range considered here. Whereas, the sorption and outgassing of Zircar RS-1200 was highly non-linear with significant hysteresis,more » especially at higher water activities, at all temperatures considered here. The type of hysteresis suggested the presence of mesopores in Zircar RS-1200, whereas the lack of hysteresis in Sylgard-184 indicates that it has a nonporous structure. A diffusion model coupled with a dynamic, triple-mode sorption (Langmuir, Henry, and pooling modes) model employed in this study matched our experimental data very well and provides mechanistic insight into the processes. Our triple-mode sorption model was adaptive enough to (1) model these distinctly different materials and (2) predict sorption and outgassing under conditions that are distinctly different from the parameterization experiments.« less

Dynamic Triple-Mode Sorption and Outgassing in Materials

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

Sharma, Hom N.; Harley, Stephen J.; Sun, Yunwei

Moisture uptake and outgassing can be detrimental to a system by altering the chemical and mechanical properties of materials within the system over time. In this work, we conducted isotherm experiments to investigate dynamic moisture sorption and desorption in markedly different materials, i.e., a polymeric material, Sylgard-184 and a ceramic aluminosilicate material, Zircar RS-1200, at different temperatures (30 °C–70 °C) by varying the water activity (0.0–0.90). Sylgard-184 showed a linear sorption and outgassing behavior with no-hysteresis over the entire temperature and water activity range considered here. Whereas, the sorption and outgassing of Zircar RS-1200 was highly non-linear with significant hysteresis,more » especially at higher water activities, at all temperatures considered here. The type of hysteresis suggested the presence of mesopores in Zircar RS-1200, whereas the lack of hysteresis in Sylgard-184 indicates that it has a nonporous structure. A diffusion model coupled with a dynamic, triple-mode sorption (Langmuir, Henry, and pooling modes) model employed in this study matched our experimental data very well and provides mechanistic insight into the processes. Our triple-mode sorption model was adaptive enough to (1) model these distinctly different materials and (2) predict sorption and outgassing under conditions that are distinctly different from the parameterization experiments.« less

Conceptual model analysis of interaction at a concrete-Boom Clay interface

NASA Astrophysics Data System (ADS)

Liu, Sanheng; Jacques, Diederik; Govaerts, Joan; Wang, Lian

In many concepts for deep disposal of high-level radioactive waste, cementitious materials are used in the engineered barriers. For example, in Belgium the engineered barrier system is based on a considerable amount of cementitious materials as buffer and backfill in the so-called supercontainer embedded in the hosting geological formation. A potential hosting formation is Boom Clay. Insight in the interaction between the high-pH pore water of the cementitious materials and neutral-pH Boom Clay pore water is required. Two problems are quite common for modeling of such a system. The first one is the computational cost due to the long timescale model assessments envisaged for the deep disposal system. Also a very fine grid (in sub-millimeter), especially at interfaces has to be used in order to accurately predict the evolution of the system. The second one is whether to use equilibrium or kinetic reaction models. The objectives of this paper are twofold. First, we develop an efficient coupled reactive transport code for this diffusion-dominated system by making full use of multi-processors/cores computers. Second, we investigate how sensitive the system is to chemical reaction models especially when pore clogging due to mineral precipitation is considered within the cementitious system. To do this, we selected two portlandite dissolution models, i.e., equilibrium (fastest) and diffusion-controlled model with precipitation of a calcite layer around portlandite particles (diffusion-controlled dissolution). The results show that with shrinking core model portlandite dissolution and calcite precipitation are much slower than with the equilibrium model. Also diffusion-controlled dissolution smooths out dissolution fronts compared to the equilibrium model. However, only a slight difference with respect to the clogging time can be found even though we use a very small diffusion coefficient (10-20 m2/s) in the precipitated calcite layer.

Novel Modelling Tool for Energetics

NASA Astrophysics Data System (ADS)

Dossi, Licia

Polymer science combines an understanding of chemistry and material properties to design, develop, model and manufacture new materials with special properties for new applications. The Binders by Design UK programme, funded through the Weapons Science and Technology Centre (WSTC) by the Defence Science and Technology Laboratory (Dstl), develop new polymeric materials for energetic applications that can survive over the increased operating temperature ranges of future weapon platforms and satisfy international and national regulations. A multidisciplinary team of UK chemists, physicists, modellers and end users (Cranfield University, Sheffield-Hallam University, QinetiQ, Fluid Gravity Engineering, BAE Systems UK Land and Roxel UK) research together on the synthesis, characterisation and modelling of novel macromolecules with very promising thermal properties. Group Interaction Modelling supported by molecular mechanics calculations is used for a rapid assessment and selection of candidate molecules. New model and simulation protocols suitable for investigating the glass transition behaviour of HTPB oligomers are developed. The continuum level models and a constitutive model for a binder/energetic system are developing, for application in safety assessments (e.g. low-velocity impact tests).

Synthesis, Characterization, and Modeling of Nanotube Materials with Variable Stiffness Tethers

NASA Technical Reports Server (NTRS)

Frankland, S. J. V.; Herzog, M. N.; Odegard, G. M.; Gates, T. S.; Fay, C. C.

2004-01-01

Synthesis, mechanical testing, and modeling have been performed for carbon nanotube based materials. Tests using nanoindentation indicated a six-fold enhancement in the storage modulus when comparing the base material (no nanotubes) to the composite that contained 5.3 wt% of nanotubes. To understand how crosslinking the nanotubes may further alter the stiffness, a model of the system was constructed using nanotubes crosslinked with a variable stiffness tether (VST). The model predicted that for a composite with 5 wt% nanotubes at random orientations, crosslinked with the VST, the bulk Young's modulus was reduced by 30% compared to the noncrosslinked equivalent.

Complex Permittivity of Planar Building Materials Measured With an Ultra-Wideband Free-Field Antenna Measurement System.

PubMed

Davis, Ben; Grosvenor, Chriss; Johnk, Robert; Novotny, David; Baker-Jarvis, James; Janezic, Michael

2007-01-01

Building materials are often incorporated into complex, multilayer macrostructures that are simply not amenable to measurements using coax or waveguide sample holders. In response to this, we developed an ultra-wideband (UWB) free-field measurement system. This measurement system uses a ground-plane-based system and two TEM half-horn antennas to transmit and receive the RF signal. The material samples are placed between the antennas, and reflection and transmission measurements made. Digital signal processing techniques are then applied to minimize environmental and systematic effects. The processed data are compared to a plane-wave model to extract the material properties with optimization software based on genetic algorithms.

A Model for Infusing Energy Concepts into Vocational Education Programs. Advanced Solar Systems.

ERIC Educational Resources Information Center

Delta Vocational Technical School, Marked Tree, AR.

This instructional unit consists of materials designed to help students understand terms associated with solar energy; identify components of advanced solar systems; and identify applications of solar energy in business, industry, agriculture, and photovoltaics. Included in the unit are the following materials: suggested activities, instructional…

Air Force Laboratory’s 2005 Technology Milestones

DTIC Science & Technology

2006-01-01

Computational materials science methods can benefit the design and property prediction of complex real-world materials. With these models , scientists and...Warfighter Page Air High - Frequency Acoustic System...800) 203-6451 High - Frequency Acoustic System Payoff Scientists created the High - Frequency Acoustic Suppression Technology (HiFAST) airflow control

Nonlinearity and Strain-Rate Dependence in the Deformation Response of Polymer Matrix Composites Modeled

NASA Technical Reports Server (NTRS)

Goldberg, Robert K.

2000-01-01

There has been no accurate procedure for modeling the high-speed impact of composite materials, but such an analytical capability will be required in designing reliable lightweight engine-containment systems. The majority of the models in use assume a linear elastic material response that does not vary with strain rate. However, for containment systems, polymer matrix composites incorporating ductile polymers are likely to be used. For such a material, the deformation response is likely to be nonlinear and to vary with strain rate. An analytical model has been developed at the NASA Glenn Research Center at Lewis Field that incorporates both of these features. A set of constitutive equations that was originally developed to analyze the viscoplastic deformation of metals (Ramaswamy-Stouffer equations) was modified to simulate the nonlinear, rate-dependent deformation of polymers. Specifically, the effects of hydrostatic stresses on the inelastic response, which can be significant in polymers, were accounted for by a modification of the definition of the effective stress. The constitutive equations were then incorporated into a composite micromechanics model based on the mechanics of materials theory. This theory predicts the deformation response of a composite material from the properties and behavior of the individual constituents. In this manner, the nonlinear, rate-dependent deformation response of a polymer matrix composite can be predicted.

The estimation of material and patch parameters in a PDE-based circular plate model

NASA Technical Reports Server (NTRS)

Banks, H. T.; Smith, Ralph C.; Brown, D. E.; Metcalf, Vern L.; Silcox, R. J.

1995-01-01

The estimation of material and patch parameters for a system involving a circular plate, to which piezoceramic patches are bonded, is considered. A partial differential equation (PDE) model for the thin circular plate is used with the passive and active contributions form the patches included in the internal and external bending moments. This model contains piecewise constant parameters describing the density, flexural rigidity, Poisson ratio, and Kelvin-Voigt damping for the system as well as patch constants and a coefficient for viscous air damping. Examples demonstrating the estimation of these parameters with experimental acceleration data and a variety of inputs to the experimental plate are presented. By using a physically-derived PDE model to describe the system, parameter sets consistent across experiments are obtained, even when phenomena such as damping due to electric circuits affect the system dynamics.

Development of Advanced Coatings for Laser Modifications Through Process and Materials Simulation

NASA Astrophysics Data System (ADS)

Martukanitz, R. P.; Babu, S. S.

2004-06-01

A simulation-based system is currently being constructed to aid in the development of advanced coating systems for laser cladding and surface alloying. The system employs loosely coupled material and process models that allow rapid determination of material compatibility over a wide range of processing conditions. The primary emphasis is on the development and identification of composite coatings for improved wear and corrosion resistance. The material model utilizes computational thermodynamics and kinetic analysis to establish phase stability and extent of diffusional reactions that may result from the thermal response of the material during virtual processing. The process model is used to develop accurate thermal histories associated with the laser surface modification process and provides critical input for the non-isothermal materials simulations. These techniques were utilized to design a laser surface modification experiment that utilized the addition of stainless steel alloy 431 and TiC produced using argon and argon and nitrogen shielding. The deposits representing alloy 431 and TiC powder produced in argon resulted in microstructures retaining some TiC particles and an increase in hardness when compared to deposits produced using only the 431 powder. Laser deposits representing alloy 431 and TiC powder produced with a mixture of argon and nitrogen shielding gas resulted in microstructures retaining some TiC particles, as well as fine precipitates of Ti(CN) formed during cooling and a further increase in hardness of the deposit.

Engineering and fabrication cost considerations for cryogenic wind tunnel models

NASA Technical Reports Server (NTRS)

Boykin, R. M., Jr.; Davenport, J. B., Jr.

1983-01-01

Design and fabrication cost drivers for cryogenic transonic wind tunnel models are defined. The major cost factors for wind tunnel models are model complexity, tolerances, surface finishes, materials, material validation, and model inspection. The cryogenic temperatures require the use of materials with relatively high fracture toughness but at the same time high strength. Some of these materials are very difficult to machine, requiring extensive machine hours which can add significantly to the manufacturing costs. Some additional engineering costs are incurred to certify the materials through mechanical tests and nondestructive evaluation techniques, which are not normally required with conventional models. When instrumentation such as accelerometers and electronically scanned pressure modules is required, temperature control of these devices needs to be incorporated into the design, which requires added effort. Additional thermal analyses and subsystem tests may be necessary, which also adds to the design costs. The largest driver to the design costs is potentially the additional static and dynamic analyses required to insure structural integrity of the model and support system.

Applicability of a 1D Analytical Model for Pulse Thermography of Laterally Heterogeneous Semitransparent Materials

NASA Astrophysics Data System (ADS)

Bernegger, R.; Altenburg, S. J.; Röllig, M.; Maierhofer, C.

2018-03-01

Pulse thermography (PT) has proven to be a valuable non-destructive testing method to identify and quantify defects in fiber-reinforced polymers. To perform a quantitative defect characterization, the heat diffusion within the material as well as the material parameters must be known. The heterogeneous material structure of glass fiber-reinforced polymers (GFRP) as well as the semitransparency of the material for optical excitation sources of PT is still challenging. For homogeneous semitransparent materials, 1D analytical models describing the temperature distribution are available. Here, we present an analytical approach to model PT for laterally inhomogeneous semitransparent materials. We show the validity of the model by considering different configurations of the optical heating source, the IR camera, and the differently coated GFRP sample. The model considers the lateral inhomogeneity of the semitransparency by an additional absorption coefficient. It includes additional effects such as thermal losses at the samples surfaces, multilayer systems with thermal contact resistance, and a finite duration of the heating pulse. By using a sufficient complexity of the analytical model, similar values of the material parameters were found for all six investigated configurations by numerical fitting.

The influence of the free space environment on the superlight-weight thermal protection system: conception, methods, and risk analysis

NASA Astrophysics Data System (ADS)

Yatsenko, Vitaliy; Falchenko, Iurii; Fedorchuk, Viktor; Petrushynets, Lidiia

2016-07-01

This report focuses on the results of the EU project "Superlight-weight thermal protection system for space application (LIGHT-TPS)". The bottom line is an analysis of influence of the free space environment on the superlight-weight thermal protection system (TPS). This report focuses on new methods that based on the following models: synergetic, physical, and computational. This report concentrates on four approaches. The first concerns the synergetic approach. The synergetic approach to the solution of problems of self-controlled synthesis of structures and creation of self-organizing technologies is considered in connection with the super-problem of creation of materials with new functional properties. Synergetics methods and mathematical design are considered according to actual problems of material science. The second approach describes how the optimization methods can be used to determine material microstructures with optimized or targeted properties. This technique enables one to find unexpected microstructures with exotic behavior (e.g., negative thermal expansion coefficients). The third approach concerns the dynamic probabilistic risk analysis of TPS l elements with complex characterizations for damages using a physical model of TPS system and a predictable level of ionizing radiation and space weather. Focusing is given mainly on the TPS model, mathematical models for dynamic probabilistic risk assessment and software for the modeling and prediction of the influence of the free space environment. The probabilistic risk assessment method for TPS is presented considering some deterministic and stochastic factors. The last approach concerns results of experimental research of the temperature distribution on the surface of the honeycomb sandwich panel size 150 x 150 x 20 mm at the diffusion welding in vacuum are considered. An equipment, which provides alignment of temperature fields in a product for the formation of equal strength of welded joints is considered. Many tasks in computational materials science can be posed as optimization problems. This technique enables one to find unexpected microstructures with exotic behavior (e.g., negative thermal expansion coefficients). The last approach is concerned with the generation of realizations of materials with specified but limited microstructural information: an intriguing inverse problem of both fundamental and practical importance. Computational models based upon the theories of molecular dynamics or quantum mechanics would enable the prediction and modification of fundamental materials properties. This problem is solved using deterministic and stochastic optimization techniques. The main optimization approaches in the frame of the EU project "Superlight-weight thermal protection system for space application" are discussed. Optimization approach to the alloys for obtaining materials with required properties using modeling techniques and experimental data will be also considered. This report is supported by the EU project "Superlight-weight thermal protection system for space application (LIGHT-TPS)"

Modeling the microstructure of surface by applying BRDF function

NASA Astrophysics Data System (ADS)

Plachta, Kamil

2017-06-01

The paper presents the modeling of surface microstructure using a bidirectional reflectance distribution function. This function contains full information about the reflectance properties of the flat surfaces - it is possible to determine the share of the specular, directional and diffuse components in the reflected luminous stream. The software is based on the authorial algorithm that uses selected elements of this function models, which allows to determine the share of each component. Basing on obtained data, the surface microstructure of each material can be modeled, which allows to determine the properties of this materials. The concentrator directs the reflected solar radiation onto the photovoltaic surface, increasing, at the same time, the value of the incident luminous stream. The paper presents an analysis of selected materials that can be used to construct the solar concentrator system. The use of concentrator increases the power output of the photovoltaic system by up to 17% as compared to the standard solution.

Sensitivity of WallDYN material migration modeling to uncertainties in mixed-material surface binding energies

DOE PAGES

Nichols, J. H.; Jaworski, M. A.; Schmid, K.

2017-03-09

The WallDYN package has recently been applied to a number of tokamaks to self-consistently model the evolution of mixed-material plasma facing surfaces. A key component of the WallDYN model is the concentration-dependent surface sputtering rate, calculated using SDTRIM.SP. This modeled sputtering rate is strongly influenced by the surface binding energies (SBEs) of the constituent materials, which are well known for pure elements but often are poorly constrained for mixed-materials. This work examines the sensitivity of WallDYN surface evolution calculations to different models for mixed-material SBEs, focusing on the carbon/lithium/oxygen/deuterium system present in NSTX. A realistic plasma background is reconstructed frommore » a high density, H-mode NSTX discharge, featuring an attached outer strike point with local density and temperature of 4 × 10 20 m -3 and 4 eV, respectively. It is found that various mixed-material SBE models lead to significant qualitative and quantitative changes in the surface evolution profile at the outer divertor, with the highest leverage parameter being the C-Li binding model. Uncertainties of order 50%, appearing on time scales relevant to tokamak experiments, highlight the importance of choosing an appropriate mixed-material sputtering representation when modeling the surface evolution of plasma facing components. Lastly, these results are generalized to other fusion-relevant materials with different ranges of SBEs.« less

Sensitivity of WallDYN material migration modeling to uncertainties in mixed-material surface binding energies

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

Nichols, J. H.; Jaworski, M. A.; Schmid, K.

The WallDYN package has recently been applied to a number of tokamaks to self-consistently model the evolution of mixed-material plasma facing surfaces. A key component of the WallDYN model is the concentration-dependent surface sputtering rate, calculated using SDTRIM.SP. This modeled sputtering rate is strongly influenced by the surface binding energies (SBEs) of the constituent materials, which are well known for pure elements but often are poorly constrained for mixed-materials. This work examines the sensitivity of WallDYN surface evolution calculations to different models for mixed-material SBEs, focusing on the carbon/lithium/oxygen/deuterium system present in NSTX. A realistic plasma background is reconstructed frommore » a high density, H-mode NSTX discharge, featuring an attached outer strike point with local density and temperature of 4 × 10 20 m -3 and 4 eV, respectively. It is found that various mixed-material SBE models lead to significant qualitative and quantitative changes in the surface evolution profile at the outer divertor, with the highest leverage parameter being the C-Li binding model. Uncertainties of order 50%, appearing on time scales relevant to tokamak experiments, highlight the importance of choosing an appropriate mixed-material sputtering representation when modeling the surface evolution of plasma facing components. Lastly, these results are generalized to other fusion-relevant materials with different ranges of SBEs.« less

Impact compaction of a granular material

DOE PAGES

Fenton, Gregg; Asay, Blaine; Dalton, Devon

2015-05-19

The dynamic behavior of granular materials has importance to a variety of engineering applications. Structural seismic coupling, planetary science, and earth penetration mechanics, are just a few of the application areas. Although the mechanical behavior of granular materials of various types have been studied extensively for several decades, the dynamic behavior of such materials remains poorly understood. High-quality experimental data are needed to improve our general understanding of granular material compaction physics. This study will describe how an instrumented plunger impact system can be used to measure pressure-density relationships for model materials at high and controlled strain rates and subsequentlymore » used for computational modeling.« less

A Model for Teaching the American Economic System to Non-Business Majors.

ERIC Educational Resources Information Center

Hoskins, Thomas R.; Merriam, Lauren E., Jr.

This model provides community college economics instructors with a flexible plan for developing instructional programs and materials to improve the level of economic understanding among non-business majors. More specifically, the model provides instructors with some exposure to the systems approach to instructional design and to appropriate…

The effect of material choice on biofilm formation in a model warm water distribution system.

PubMed

Waines, Paul L; Moate, Roy; Moody, A John; Allen, Mike; Bradley, Graham

2011-11-01

Water distribution systems (WDS) are composed of a variety of materials and may harbour potential pathogens within surface-attached microbial biofilms. Biofilm formation on four plumbing materials, viz. copper, stainless steel 316 (SS316), ethylene propylene diene monomer (EPDM) and cross-linked polyethylene (PEX), was investigated using scanning electron microscope (SEM)/confocal microscopy, ATP-/culture-based analysis, and molecular analysis. Material 'inserts' were incorporated into a mains water fed, model WDS. All materials supported biofilm growth to various degrees. After 84 days, copper and SS316 showed no significant overall differences in terms of the level of biofilm formation observed, whilst PEX supported a significantly higher level of biofilm. EPDM exhibited gross contamination by a complex, multispecies biofilm, at a level significantly higher than was observed on the other materials, regardless of the analytical method used. PCR-DGGE analysis showed clear differences in the composition of the biofilm community on all materials after 84 days. The primary conclusion of this study has been to identify EPDM as a potentially unsuitable material for use as a major component in WDS.

A system structure for predictive relations in penetration mechanics

NASA Astrophysics Data System (ADS)

Korjack, Thomas A.

1992-02-01

The availability of a software system yielding quick numerical models to predict ballistic behavior is a requisite for any research laboratory engaged in material behavior. What is especially true about accessibility of rapid prototyping for terminal impaction is the enhancement of a system structure which will direct the specific material and impact situation towards a specific predictive model. This is of particular importance when the ranges of validity are at stake and the pertinent constraints associated with the impact are unknown. Hence, a compilation of semiempirical predictive penetration relations for various physical phenomena has been organized into a data structure for the purpose of developing a knowledge-based decision aided expert system to predict the terminal ballistic behavior of projectiles and targets. The ranges of validity and constraints of operation of each model were examined and cast into a decision tree structure to include target type, target material, projectile types, projectile materials, attack configuration, and performance or damage measures. This decision system implements many penetration relations, identifies formulas that match user-given conditions, and displays the predictive relation coincident with the match in addition to a numerical solution. The physical regimes under consideration encompass the hydrodynamic, transitional, and solid; the targets are either semi-infinite or plate, and the projectiles include kinetic and chemical energy. A preliminary databases has been constructed to allow further development of inductive and deductive reasoning techniques applied to ballistic situations involving terminal mechanics.

Numerical modeling of heat and mass transport processes in an evaporative thermal protection system

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

Bobrov, I.N.; Kuryachii, A.P.

1992-08-01

We propose a mathematical model of heat and mass transport processes in a moist, porous material subject to capillary action. The material is in contact with a heated surface, and the processes take place while the liquid is evaporating in a cavity with a drainage hole. A sample calculation based on the model is presented. 45 refs., 4 figs.

Studying Zeolite Catalysts with a 2D Model System

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

Boscoboinik, Anibal

2016-12-07

Anibal Boscoboinik, a materials scientist at Brookhaven’s Center for Functional Nanomaterials, discusses the surface-science tools and 2D model system he uses to study catalysis in nanoporous zeolites, which catalyze reactions in many industrial processes.

Advanced Techniques for Ultrasonic Imaging in the Presence of Material and Geometrical Complexity

NASA Astrophysics Data System (ADS)

Brath, Alexander Joseph

The complexity of modern engineering systems is increasing in several ways: advances in materials science are leading to the design of materials which are optimized for material strength, conductivity, temperature resistance etc., leading to complex material microstructure; the combination of additive manufacturing and shape optimization algorithms are leading to components with incredibly intricate geometrical complexity; and engineering systems are being designed to operate at larger scales in ever harsher environments. As a result, at the same time that there is an increasing need for reliable and accurate defect detection and monitoring capabilities, many of the currently available non-destructive evaluation techniques are rendered ineffective by this increasing material and geometrical complexity. This thesis addresses the challenges posed by inspection and monitoring problems in complex engineering systems with a three-part approach. In order to address material complexities, a model of wavefront propagation in anisotropic materials is developed, along with efficient numerical techniques to solve for the wavefront propagation in inhomogeneous, anisotropic material. Since material and geometrical complexities significantly affect the ability of ultrasonic energy to penetrate into the specimen, measurement configurations are tailored to specific applications which utilize arrays of either piezoelectric (PZT) or electromagnetic acoustic transducers (EMAT). These measurement configurations include novel array architectures as well as the exploration of ice as an acoustic coupling medium. Imaging algorithms which were previously developed for isotropic materials with simple geometry are adapted to utilize the more powerful wavefront propagation model and novel measurement configurations.

Inner solar system material discovered in the Oort cloud

PubMed Central

Meech, Karen J.; Yang, Bin; Kleyna, Jan; Hainaut, Olivier R.; Berdyugina, Svetlana; Keane, Jacqueline V.; Micheli, Marco; Morbidelli, Alessandro; Wainscoat, Richard J.

2016-01-01

We have observed C/2014 S3 (PANSTARRS), a recently discovered object on a cometary orbit coming from the Oort cloud that is physically similar to an inner main belt rocky S-type asteroid. Recent dynamical models successfully reproduce the key characteristics of our current solar system; some of these models require significant migration of the giant planets, whereas others do not. These models provide different predictions on the presence of rocky material expelled from the inner solar system in the Oort cloud. C/2014 S3 could be the key to verifying these predictions of the migration-based dynamical models. Furthermore, this object displays a very faint, weak level of comet-like activity, five to six orders of magnitude less than that of typical ice-rich comets on similar Orbits coming from the Oort cloud. For the nearly tailless appearance, we are calling C/2014 S3 a Manx object. Various arguments convince us that this activity is produced by sublimation of volatile ice, that is, normal cometary activity. The activity implies that C/2014 S3 has retained a tiny fraction of the water that is expected to be present at its formation distance in the inner solar system. We may be looking at fresh inner solar system Earth-forming material that was ejected from the inner solar system and preserved for billions of years in the Oort cloud. PMID:27386512

Inner solar system material discovered in the Oort cloud.

PubMed

Meech, Karen J; Yang, Bin; Kleyna, Jan; Hainaut, Olivier R; Berdyugina, Svetlana; Keane, Jacqueline V; Micheli, Marco; Morbidelli, Alessandro; Wainscoat, Richard J

2016-04-01

We have observed C/2014 S3 (PANSTARRS), a recently discovered object on a cometary orbit coming from the Oort cloud that is physically similar to an inner main belt rocky S-type asteroid. Recent dynamical models successfully reproduce the key characteristics of our current solar system; some of these models require significant migration of the giant planets, whereas others do not. These models provide different predictions on the presence of rocky material expelled from the inner solar system in the Oort cloud. C/2014 S3 could be the key to verifying these predictions of the migration-based dynamical models. Furthermore, this object displays a very faint, weak level of comet-like activity, five to six orders of magnitude less than that of typical ice-rich comets on similar Orbits coming from the Oort cloud. For the nearly tailless appearance, we are calling C/2014 S3 a Manx object. Various arguments convince us that this activity is produced by sublimation of volatile ice, that is, normal cometary activity. The activity implies that C/2014 S3 has retained a tiny fraction of the water that is expected to be present at its formation distance in the inner solar system. We may be looking at fresh inner solar system Earth-forming material that was ejected from the inner solar system and preserved for billions of years in the Oort cloud.

Behaviour of fibre reinforced polymer confined reinforced concrete columns under fire condition

NASA Astrophysics Data System (ADS)

Chowdhury, Ershad Ullah

In recent years, fibre reinforced polymer (FRP) materials have demonstrated enormous potential as materials for repairing and retrofitting concrete bridges that have deteriorated from factors such as electro-chemical corrosion and increased load requirements. However, concerns associated with fire remain an obstacle to applications of FRP materials in buildings and parking garages due to FRP's sensitivity to high temperatures as compared with other structural materials and to limited knowledge on their thermal and mechanical behaviour in fire. This thesis presents results from an ongoing study on the fire performance of FRP materials, fire insulation materials and systems, and FRP wrapped reinforced concrete columns. The overall goal of the study is to understand the fire behaviour of FRP materials and FRP strengthened concrete columns and ultimately, provide rational fire safety design recommendations and guidelines for FRP strengthened concrete columns. A combined experimental and numerical investigation was conducted to achieve the goals of this research study. The experimental work consisted of both small-scale FRP material testing at elevated temperatures and full-scale fire tests on FRP strengthened columns. A numerical model was developed to simulate the behaviour of unwrapped reinforced concrete and FRP strengthened reinforced concrete square or rectangular columns in fire. After validating the numerical model against test data available in literature, it was determined that the numerical model can be used to analyze the behaviour of concrete axial compressive members in fire. Results from this study also demonstrated that although FRP materials experience considerable loss of their mechanical and bond properties at temperatures somewhat below the glass transition temperature of the resin matrix, externally-bonded FRP can be used in strengthening concrete structural members in buildings, if appropriate supplemental fire protection system is provided over the FRP strengthening system.

Design, Fabrication, Characterization and Modeling of Integrated Functional Materials

DTIC Science & Technology

2015-12-01

interactions on the magnetization dynamics and hence the EB in these nanostructures. A comprehensive understanding of these effects is essential to...activities is expected to lead to new devices/systems/composite materials useful for the USAMRMC. 15. SUBJECT TERMS Functional materials, integrated...dimensions (nano, micro, meso, macro) leading to integrated functional materials. We have initiated this Integrated Functional Materials Project at the

Macro-magnetic Modeling of the ARL Microelectromechanical System (MEMS) Flux Concentrator

DTIC Science & Technology

2011-09-01

are drawn as solid pieces and assigned the material properties of permalloy (nickel-iron [ NiFe ]) with a permeability of 5,000 as that is a value...energy densities, and saturation. The modeling process consists of drawing the objects of interest, assigning properties (coercivity, permeability...that is readily achieved in thin films of the material. The material properties assigned to this background are those of a vacuum, with a relative

Ballistic Performance of Porous-Ceramic, Thermal Protection Systems

NASA Astrophysics Data System (ADS)

Miller, Joshua; Bohl, William; Christiansen, Eric; Davis, B. Alan; Foreman, Cory

2011-06-01

Porous-ceramic, thermal protection systems are used heavily in current reentry vehicles like the Orbiter, and they are currently being proposed for the next generation of US manned spacecraft, Orion. These systems insulate reentry critical components of a spacecraft against the intense thermal environments of atmospheric reentry. Additionally, these materials are also highly exposed to space environment hazards like solid particle impacts. This paper discusses impact testing up to 9.65 km/s on one of these systems. The materials considered are 8 lb/ft3 alumina-fiber-enhanced-thermal-barrier (AETB8) tiles coated with a toughened-unipiece-fibrous-insulation/reaction-cured-glass layer (TUFI/RCG). A semi-empirical, first principals impact model that describes projectile dispersion is described that provides excellent agreement with observations over a broad range of impact velocities, obliquities and projectile materials. A model extension to look at the implications of greater than 10 GPa equation of state measurements is also discussed. Predicted penetration probabilities for a vehicle visiting the International Space Station is 60% lower for orbital debris and 95% lower for meteoroids with this model compared to an energy scaled approach.

Materials testing of the IUS techroll seal material

NASA Technical Reports Server (NTRS)

Nichols, R. L.; Hall, W. B.

1984-01-01

As a part of the investigation of the control system failure Inertial Upper Stage on IUS-1 flight to position a Tracking and Data Relay Satellite (TDRS) in geosynchronous orbit, the materials utilized in the techroll seal are evaluated for possible failure models. Studies undertaken included effect of temperature on the strength of the system, effect of fatigue on the strength of the system, thermogravimetric analysis, thermomechanical analysis, differential scanning calorimeter analysis, dynamic mechanical analysis, and peel test. The most likely failure mode is excessive temperature in the seal. In addition, the seal material is susceptible to fatigue damage which could be a contributing factor.

Using Indigenous Materials for Construction

DTIC Science & Technology

2015-07-01

Theoretical models were devised for prediction of the structural attributes of indigenous ferrocement sheets and sandwich composite panels comprising the...indigenous ferrocement skins and aerated concrete core. Structural designs were developed for these indigenous sandwich composite panels in typical...indigenous materials and building systems developed in the project were evaluated. Numerical modeling capabilities were developed for structural

Analysis of an operator-differential model for magnetostrictive energy harvesting

NASA Astrophysics Data System (ADS)

Davino, D.; Krejčí, P.; Pimenov, A.; Rachinskii, D.; Visone, C.

2016-10-01

We present a model of, and analysis of an optimization problem for, a magnetostrictive harvesting device which converts mechanical energy of the repetitive process such as vibrations of the smart material to electrical energy that is then supplied to an electric load. The model combines a lumped differential equation for a simple electronic circuit with an operator model for the complex constitutive law of the magnetostrictive material. The operator based on the formalism of the phenomenological Preisach model describes nonlinear saturation effects and hysteresis losses typical of magnetostrictive materials in a thermodynamically consistent fashion. We prove well-posedness of the full operator-differential system and establish global asymptotic stability of the periodic regime under periodic mechanical forcing that represents mechanical vibrations due to varying environmental conditions. Then we show the existence of an optimal solution for the problem of maximization of the output power with respect to a set of controllable parameters (for the periodically forced system). Analytical results are illustrated with numerical examples of an optimal solution.

Module encapsulation technology

NASA Technical Reports Server (NTRS)

Willis, P.

1986-01-01

The identification and development techniques for low-cost module encapsulation materials were reviewed. Test results were displayed for a variety of materials. The improved prospects for modeling encapsulation systems for life prediction were reported.

An embedded fibre optic sensor for impact damage detection in composite materials

NASA Astrophysics Data System (ADS)

Glossop, Neil David William

1989-09-01

A structurally embedded fiber optic damage detection sensor for composite materials is described. The system is designed specifically for the detection of barely visible damage resulting from low velocity impacts in Kevlar-epoxy laminates. By monitoring the light transmission properties of optical fiber embedded in the composite, it was shown that the integrity of the material can be accurately determined. The effect of several parameters on the sensitivity of the system was investigated, including the effect of the optical fiber orientation and depth of embedding within the composite. A novel surface was also developed for the optical fibers to ensure they will fracture at the requisite damage level. The influence of the optical fiber sensors on the tensile and compressive material properties and on the impact resistance of the laminate was also studied. Extensive experimental results from impact tests are reported and a numerical model of the impact event is presented which is able to predict and model the damage mechanism and sensor system. A new and powerful method of nondestructive evaluation for translucent composite materials based on image enhanced backlighting is also described.

Human life support during interplanetary travel and domicile. II - Generic Modular Flow Schematic modeling

NASA Technical Reports Server (NTRS)

Farral, Joseph F.; Seshan, P. K.; Rohatgi, Naresh K.

1991-01-01

This paper describes the Generic Modular Flow Schematic (GMFS) architecture capable of encompassing all functional elements of a physical/chemical life support system (LSS). The GMFS can be implemented to synthesize, model, analyze, and quantitatively compare many configurations of LSSs, from a simple, completely open-loop to a very complex closed-loop. The GMFS model is coded in ASPEN, a state-of-the-art chemical process simulation program, to accurately compute the material, heat, and power flow quantities for every stream in each of the subsystem functional elements (SFEs) in the chosen configuration of a life support system. The GMFS approach integrates the various SFEs and subsystems in a hierarchical and modular fashion facilitating rapid substitutions and reconfiguration of a life support system. The comprehensive ASPEN material and energy balance output is transferred to a systems and technology assessment spreadsheet for rigorous system analysis and trade studies.

Thermal imaging measurement of lateral diffusivity and non-invasive material defect detection

DOEpatents

Sun, Jiangang; Deemer, Chris

2003-01-01

A system and method for determining lateral thermal diffusivity of a material sample using a heat pulse; a sample oriented within an orthogonal coordinate system; an infrared camera; and a computer that has a digital frame grabber, and data acquisition and processing software. The mathematical model used within the data processing software is capable of determining the lateral thermal diffusivity of a sample of finite boundaries. The system and method may also be used as a nondestructive method for detecting and locating cracks within the material sample.

Carbon recycling in materially closed ecological life support systems

NASA Technical Reports Server (NTRS)

Obenhuber, D. C.; Folsome, C. E.

1988-01-01

Results of studies are presented of materially closed energetically open microbial ecosystems or 'closed ecosystems'. These are natural marine ecosystems that have been sealed in glass containers to prevent material exchange with the environment but allow energy to pass freely through them. They represent model life support systems for the future human habitation of space. The results are discussed analytically and indicate that these ecosystems, when subjected to a constant energy flux, seem to be reliable and self-sufficient systems for recycling of biologically produced carbon compounds.

Recognizing Materials using Perceptually Inspired Features

PubMed Central

Sharan, Lavanya; Liu, Ce; Rosenholtz, Ruth; Adelson, Edward H.

2013-01-01

Our world consists not only of objects and scenes but also of materials of various kinds. Being able to recognize the materials that surround us (e.g., plastic, glass, concrete) is important for humans as well as for computer vision systems. Unfortunately, materials have received little attention in the visual recognition literature, and very few computer vision systems have been designed specifically to recognize materials. In this paper, we present a system for recognizing material categories from single images. We propose a set of low and mid-level image features that are based on studies of human material recognition, and we combine these features using an SVM classifier. Our system outperforms a state-of-the-art system [Varma and Zisserman, 2009] on a challenging database of real-world material categories [Sharan et al., 2009]. When the performance of our system is compared directly to that of human observers, humans outperform our system quite easily. However, when we account for the local nature of our image features and the surface properties they measure (e.g., color, texture, local shape), our system rivals human performance. We suggest that future progress in material recognition will come from: (1) a deeper understanding of the role of non-local surface properties (e.g., extended highlights, object identity); and (2) efforts to model such non-local surface properties in images. PMID:23914070

Studying Zeolite Catalysts with a 2D Model System

ScienceCinema

Boscoboinik, Anibal

2018-06-13

Anibal Boscoboinik, a materials scientist at Brookhaven’s Center for Functional Nanomaterials, discusses the surface-science tools and 2D model system he uses to study catalysis in nanoporous zeolites, which catalyze reactions in many industrial processes.

Bending, force recovery, and D-cones in origami inspired model geometries

NASA Astrophysics Data System (ADS)

Eldar, Theresa; Rozairo, Damith; Croll, Andrew B.

The need for materials with advanced functionality has driven a considerable amount of modern materials science. One idea that has gained significant traction is combining of the ideas Origami and Kirigami with existing materials to build in advanced functionality. In most origami damage is induced in order to trap areas of high curvature in desirable locations in a material. However, the long term and dynamic consequences of local failure are largely unknown. In order to gauge the complex interplay of material properties, relaxation and failure in a set of model thin films, a series of bending and force recovery experiments were carried out. We focus on three materials; polydimethylsiloxane (PDMS), polycarbonate (PC), and polystyrene (PS) chosen for their varying responses to stress. We first measured the load bearing capacity of a single bend in each material, examining the force recovery of bends at various curvatures. Next we examined a doubly folded system in which a single developable cone was created in a similar manner. While the D-cone clearly has massive local consequences for each system, it plays an insignificant role in the system's overall behavior. Finally, we considered higher order combinations of d-cones, ridges and bends. AFOSR under the Young Investigator Program (FA9550-15-1-0168).

Experimental and Analytical Characterization of the Macromechanical Response for Triaxial Braided Composite Materials

NASA Technical Reports Server (NTRS)

Littell, Justin D.

2013-01-01

Increasingly, carbon composite structures are being used in aerospace applications. Their highstrength, high-stiffness, and low-weight properties make them good candidates for replacing many aerospace structures currently made of aluminum or steel. Recently, many of the aircraft engine manufacturers have developed new commercial jet engines that will use composite fan cases. Instead of using traditional composite layup techniques, these new fan cases will use a triaxially braided pattern, which improves case performance. The impact characteristics of composite materials for jet engine fan case applications have been an important research topic because Federal regulations require that an engine case be able to contain a blade and blade fragments during an engine blade-out event. Once the impact characteristics of these triaxial braided materials become known, computer models can be developed to simulate a jet engine blade-out event, thus reducing cost and time in the development of these composite jet engine cases. The two main problems that have arisen in this area of research are that the properties for these materials have not been fully determined and computationally efficient computer models, which incorporate much of the microscale deformation and failure mechanisms, are not available. The research reported herein addresses some of the deficiencies present in previous research regarding these triaxial braided composite materials. The current research develops new techniques to accurately quantify the material properties of the triaxial braided composite materials. New test methods are developed for the polymer resin composite constituent and representative composite coupons. These methods expand previous research by using novel specimen designs along with using a noncontact measuring system that is also capable of identifying and quantifying many of the microscale failure mechanisms present in the materials. Finally, using the data gathered, a new hybrid micromacromechanical computer model is created to simulate the behavior of these composite material systems under static and ballistic impact loading using the test data acquired. The model also quantifies the way in which the fiber/matrix interface affects material response under static and impact loading. The results show that the test methods are capable of accurately quantifying the polymer resin under a variety of strain rates and temperature for three loading conditions. The resin strength and stiffness data show a clear rate and temperature dependence. The data also show the hydrostatic stress effects and hysteresis, all of which can be used by researchers developing composite constitutive models for the resins. The results for the composite data reveal noticeable differences in strength, failure strain, and stiffness in the different material systems presented. The investigations into the microscale failure mechanisms provide information about the nature of the different material system behaviors. Finally, the developed computer model predicts composite static strength and stiffness to within 10 percent of the gathered test data and also agrees with composite impact data, where available.

A novel material detection algorithm based on 2D GMM-based power density function and image detail addition scheme in dual energy X-ray images.

PubMed

Pourghassem, Hossein

2012-01-01

Material detection is a vital need in dual energy X-ray luggage inspection systems at security of airport and strategic places. In this paper, a novel material detection algorithm based on statistical trainable models using 2-Dimensional power density function (PDF) of three material categories in dual energy X-ray images is proposed. In this algorithm, the PDF of each material category as a statistical model is estimated from transmission measurement values of low and high energy X-ray images by Gaussian Mixture Models (GMM). Material label of each pixel of object is determined based on dependency probability of its transmission measurement values in the low and high energy to PDF of three material categories (metallic, organic and mixed materials). The performance of material detection algorithm is improved by a maximum voting scheme in a neighborhood of image as a post-processing stage. Using two background removing and denoising stages, high and low energy X-ray images are enhanced as a pre-processing procedure. For improving the discrimination capability of the proposed material detection algorithm, the details of the low and high energy X-ray images are added to constructed color image which includes three colors (orange, blue and green) for representing the organic, metallic and mixed materials. The proposed algorithm is evaluated on real images that had been captured from a commercial dual energy X-ray luggage inspection system. The obtained results show that the proposed algorithm is effective and operative in detection of the metallic, organic and mixed materials with acceptable accuracy.

Evaluation of Model-Based Training for Vertical Guidance Logic

NASA Technical Reports Server (NTRS)

Feary, Michael; Palmer, Everett; Sherry, Lance; Polson, Peter; Alkin, Marty; McCrobie, Dan; Kelley, Jerry; Rosekind, Mark (Technical Monitor)

1997-01-01

This paper will summarize the results of a study which introduces a structured, model based approach to learning how the automated vertical guidance system works on a modern commercial air transport. The study proposes a framework to provide accurate and complete information in an attempt to eliminate confusion about 'what the system is doing'. This study will examine a structured methodology for organizing the ideas on which the system was designed, communicating this information through the training material, and displaying it in the airplane. Previous research on model-based, computer aided instructional technology has shown reductions in the amount of time to a specified level of competence. The lessons learned from the development of these technologies are well suited for use with the design methodology which was used to develop the vertical guidance logic for a large commercial air transport. The design methodology presents the model from which to derive the training material, and the content of information to be displayed to the operator. The study consists of a 2 X 2 factorial experiment which will compare a new method of training vertical guidance logic and a new type of display. The format of the material used to derive both the training and the display will be provided by the Operational Procedure Methodology. The training condition will compare current training material to the new structured format. The display condition will involve a change of the content of the information displayed into pieces that agree with the concepts with which the system was designed.

A Prototype System for a Computer-Based Statewide Film Library Network: A Model for Operation. Statewide Film Library Network: System-1 Specifications - Files.

ERIC Educational Resources Information Center

Sullivan, Todd

Using an IBM System/360 Model 50 computer, the New York Statewide Film Library Network schedules film use, reports on materials handling and statistics, and provides for interlibrary loan of films. Communications between the film libraries and the computer are maintained by Teletype model 33 ASR Teletypewriter terminals operating on TWX…

A numerical model for thermal energy storage systems utilising encapsulated phase change materials

NASA Astrophysics Data System (ADS)

Jacob, Rhys; Saman, Wasim; Bruno, Frank

2016-05-01

In an effort to reduce the cost of thermal energy storage for concentrated solar power plants, a thermocline storage concept was investigated. Two systems were investigated being a sensible-only and an encapsulated phase change system. Both systems have the potential to reduce the storage tank volume and/or reduce the cost of the filler material, thereby reducing the cost of the system when compared to current two-tank molten salt systems. The objective of the current paper is to create a numerical model capable of designing and simulating the aforementioned thermocline storage concepts in the open source programming language known as Python. The results of the current study are compared to previous numerical results and are found to be in good agreement.

A Spatially Continuous Model of Carbohydrate Digestion and Transport Processes in the Colon

PubMed Central

Moorthy, Arun S.; Brooks, Stephen P. J.; Kalmokoff, Martin; Eberl, Hermann J.

2015-01-01

A spatially continuous mathematical model of transport processes, anaerobic digestion and microbial complexity as would be expected in the human colon is presented. The model is a system of first-order partial differential equations with context determined number of dependent variables, and stiff, non-linear source terms. Numerical simulation of the model is used to elucidate information about the colon-microbiota complex. It is found that the composition of materials on outflow of the model does not well-describe the composition of material in other model locations, and inferences using outflow data varies according to model reactor representation. Additionally, increased microbial complexity allows the total microbial community to withstand major system perturbations in diet and community structure. However, distribution of strains and functional groups within the microbial community can be modified depending on perturbation length and microbial kinetic parameters. Preliminary model extensions and potential investigative opportunities using the computational model are discussed. PMID:26680208

Biomimetic routes to nanoscale-toughened oxide ceramics

NASA Astrophysics Data System (ADS)

Deschaume, Olivier

In this work, a novel anion exchange technique has been developed and optimised in order to prepare extra-pure, hydroxide-free solutions of aluminium polyoxocations (A113 and A130) as well as for the preparation of nanosized, highly monodisperse aluminium hydroxide particles in the particle size range 20-200nm. In order for the evolution and composition of the resulting systems to be monitored, an array of characterisation techniques including 27A1 NMR, dynamic light scattering, po-tentiometry, conductometry and UV-Vis spectroscopy, have been implemented and complemented with successful data treatment strategies. The quantitative data obtained indicates that the static anion exchange method is a soft, environmentally friendly, low-cost, energy-saving and convenient procedure for the preparation of Al- containing model systems. The A1 species obtained can be used for high-precision model studies on A1 speciation, and serve as nanosize precursors to a variety of Al-containing materials. The use of these pure A1 precursors has a clear advantage in materials synthesis arising from an improved understanding and better control of A1 speciation. In a second development of the project, the model systems have been used in a nanotectonic approach to biomimetic materials synthesis, with possible applications to the optimisation of Al-containing materials such as ceramics or composite films. Bearing this aim in mind, the interactions of the prepared aluminium species with the model protein BSA and a bioelastomer, elastin, were monitored and the resulting composite materials characterised. The methodology developed for the synthesis and characterisation of pure A1 species and A1 species/biomolecule systems is a robust base for further studies spanning research fields such as Chemistry, Biology or Environmental sciences, and possess a large potential for application to industrial products and processes.

La Base de Donnees ERIC: Evaluation de Son Utilisation et Discussion des Choix du Systeme (The ERIC Database: An Evaluation of Its Use and a Discussion of the System Model).

ERIC Educational Resources Information Center

Malrieu, Denise

1983-01-01

This overview of the ERIC system begins with a brief history of the system; a description of the types and numbers of materials contained in the database; sources of types of information for educators that are not processed by ERIC; and the various publications and reference materials produced by and for the system. The analysis of ERIC usage in…

The generation of amplified spontaneous emission in high-power CPA laser systems.

PubMed

Keppler, Sebastian; Sävert, Alexander; Körner, Jörg; Hornung, Marco; Liebetrau, Hartmut; Hein, Joachim; Kaluza, Malte Christoph

2016-03-01

An analytical model is presented describing the temporal intensity contrast determined by amplified spontaneous emission in high-intensity laser systems which are based on the principle of chirped pulse amplification. The model describes both the generation and the amplification of the amplified spontaneous emission for each type of laser amplifier. This model is applied to different solid state laser materials which can support the amplification of pulse durations ≤350 fs . The results are compared to intensity and fluence thresholds, e.g. determined by damage thresholds of a certain target material to be used in high-intensity applications. This allows determining if additional means for contrast improvement, e.g. plasma mirrors, are required for a certain type of laser system and application. Using this model, the requirements for an optimized high-contrast front-end design are derived regarding the necessary contrast improvement and the amplified "clean" output energy for a desired focussed peak intensity. Finally, the model is compared to measurements at three different high-intensity laser systems based on Ti:Sapphire and Yb:glass. These measurements show an excellent agreement with the model.

Theory, modeling, and simulation of structural and functional materials: Micromechanics, microstructures, and properties

NASA Astrophysics Data System (ADS)

Jin, Yongmei

In recent years, theoretical modeling and computational simulation of microstructure evolution and materials property has been attracting much attention. While significant advances have been made, two major challenges remain. One is the integration of multiple physical phenomena for simulation of complex materials behavior, the other is the bridging over multiple length and time scales in materials modeling and simulation. The research presented in this Thesis is focused mainly on tackling the first major challenge. In this Thesis, a unified Phase Field Microelasticity (PFM) approach is developed. This approach is an advanced version of the phase field method that takes into account the exact elasticity of arbitrarily anisotropic, elastically and structurally inhomogeneous systems. The proposed theory and models are applicable to infinite solids, elastic half-space, and finite bodies with arbitrary-shaped free surfaces, which may undergo various concomitant physical processes. The Phase Field Microelasticity approach is employed to formulate the theories and models of martensitic transformation, dislocation dynamics, and crack evolution in single crystal and polycrystalline solids. It is also used to study strain relaxation in heteroepitaxial thin films through misfit dislocation and surface roughening. Magnetic domain evolution in nanocrystalline thin films is also investigated. Numerous simulation studies are performed. Comparison with analytical predictions and experimental observations are presented. Agreement verities the theory and models as realistic simulation tools for computational materials science and engineering. The same Phase Field Microelasticity formalism of individual models of different physical phenomena makes it easy to integrate multiple physical processes into one unified simulation model, where multiple phenomena are treated as various relaxation modes that together act as one common cooperative phenomenon. The model does not impose a priori constraints on possible microstructure evolution paths. This gives the model predicting power, where material system itself "chooses" the optimal path for multiple processes. The advances made in this Thesis present a significant step forward to overcome the first challenge, mesoscale multi-physics modeling and simulation of materials. At the end of this Thesis, the way to tackle the second challenge, bridging over multiple length and time scales in materials modeling and simulation, is discussed based on connection between the mesoscale Phase Field Microelasticity modeling and microscopic atomistic calculation as well as macroscopic continuum theory.

Simulation of spallation life of metals in relation to operating stresses in the nanosecond loading time range

NASA Astrophysics Data System (ADS)

Makarov, P. V.; Bakeev, R. A.

2015-10-01

Spall fracture of materials is still the only means for investigation of the material life and mechanisms of its fracture in the micro-, nano-, and picosecond time ranges of tensile loading. The phenomenological model based on the concepts of multiscale fracture of materials as nonlinear dynamic systems is shown to satisfactorily describe their life in the given range. The model is employed for the calculation of spallation life.

Ford/BASF/UM Activities in Support of the Hydrogen Storage Engineering Center of Excellence

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

Veenstra, Mike; Purewal, Justin; Xu, Chunchuan

Widespread adoption of hydrogen as a vehicular fuel depends critically on the development of low-cost, on-board hydrogen storage technologies capable of achieving high energy densities and fast kinetics for hydrogen uptake and release. As present-day technologies -- which rely on physical storage methods such as compressed hydrogen -- are incapable of attaining established Department of Energy (DOE) targets, development of materials-based approaches for storing hydrogen have garnered increasing attention. Material-based storage technologies have potential to store hydrogen beyond twice the density of liquid hydrogen. To hasten development of these ‘hydride’ materials, the DOE previously established three centers of excellence formore » materials storage R&D associated with the key classes of materials: metal hydrides, chemical hydrogen, and adsorbents. While these centers made progress in identifying new storage materials, the challenges associated with the engineering of the system around a candidate storage material are in need of further advancement. In 2009 the DOE established the Hydrogen Storage Engineering Center of Excellence with the objective of developing innovative engineering concepts for materials-based hydrogen storage systems. As a partner in the Hydrogen Storage Engineering Center of Excellence, the Ford-UM-BASF team conducted a multi-faceted research program that addresses key engineering challenges associated with the development of materials-based hydrogen storage systems. First, we developed a novel framework that allowed for a material-based hydrogen storage system to be modeled and operated within a virtual fuel cell vehicle. This effort resulted in the ability to assess dynamic operating parameters and interactions between the storage system and fuel cell power plant, including the evaluation of performance throughout various drive cycles. Second, we engaged in cost modeling of various incarnations of the storage systems. This analysis revealed cost gaps and opportunities that identified a storage system that was lower cost than a 700 bar compressed system. Finally, we led the HSECoE efforts devoted to characterizing and enhancing metal organic framework (MOF) storage materials. This report serves as a final documentation of the Ford-UM-BASF project contributions to the HSECoE during the 6-year timeframe of the Center. The activities of the HSECoE have impacted the broader goals of the DOE-EERE and USDRIVE, leading to improved understanding in the engineering of materials-based hydrogen storage systems. This knowledge is a prerequisite to the development of a commercially-viable hydrogen storage system.« less

Special Issue on Uncertainty Quantification in Multiscale System Design and Simulation

DOE PAGES

Wang, Yan; Swiler, Laura

2017-09-07

The importance of uncertainty has been recognized in various modeling, simulation, and analysis applications, where inherent assumptions and simplifications affect the accuracy of model predictions for physical phenomena. As model predictions are now heavily relied upon for simulation-based system design, which includes new materials, vehicles, mechanical and civil structures, and even new drugs, wrong model predictions could potentially cause catastrophic consequences. Therefore, uncertainty and associated risks due to model errors should be quantified to support robust systems engineering.

Special Issue on Uncertainty Quantification in Multiscale System Design and Simulation

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

Wang, Yan; Swiler, Laura

The importance of uncertainty has been recognized in various modeling, simulation, and analysis applications, where inherent assumptions and simplifications affect the accuracy of model predictions for physical phenomena. As model predictions are now heavily relied upon for simulation-based system design, which includes new materials, vehicles, mechanical and civil structures, and even new drugs, wrong model predictions could potentially cause catastrophic consequences. Therefore, uncertainty and associated risks due to model errors should be quantified to support robust systems engineering.

Establishment of Low Energy Building materials and Equipment Database Based on Property Information

NASA Astrophysics Data System (ADS)

Kim, Yumin; Shin, Hyery; eon Lee, Seung

2018-03-01

The purpose of this study is to provide reliable service of materials information portal through the establishment of public big data by collecting and integrating scattered low energy building materials and equipment data. There were few cases of low energy building materials database in Korea have provided material properties as factors influencing material pricing. The framework of the database was defined referred with Korea On-line E-procurement system. More than 45,000 data were gathered by the specification of entities and with the gathered data, price prediction models for chillers were suggested. To improve the usability of the prediction model, detailed properties should be analysed for each item.

Nowcast model for hazardous material spill prevention and response, San Francisco Bay, California

USGS Publications Warehouse

Cheng, Ralph T.; Wilmot, Wayne L.; Galt, Jerry A.

1997-01-01

The National Oceanic and Atmospheric Administration (NOAA) installed the Physical Oceanographic Real-time System (PORTS) in San Francisco Bay, California, to provide real-time observations of tides, tidal currents, and meteorological conditions to, among other purposes, guide hazardous material spill prevention and response. Integrated with nowcast modeling techniques and dissemination of real-time data and the nowcasting results through the Internet on the World Wide Web, emerging technologies used in PORTS for real-time data collection forms a nowcast modeling system. Users can download tides and tidal current distribution in San Francisco Bay for their specific applications and/or for further analysis.

Flight-vehicle materials, structures, and dynamics - Assessment and future directions. Vol. 5 - Structural dynamics and aeroelasticity

NASA Technical Reports Server (NTRS)

Noor, Ahmed K. (Editor); Venneri, Samuel L. (Editor)

1993-01-01

Various papers on flight vehicle materials, structures, and dynamics are presented. Individual topics addressed include: general modeling methods, component modeling techniques, time-domain computational techniques, dynamics of articulated structures, structural dynamics in rotating systems, structural dynamics in rotorcraft, damping in structures, structural acoustics, structural design for control, structural modeling for control, control strategies for structures, system identification, overall assessment of needs and benefits in structural dynamics and controlled structures. Also discussed are: experimental aeroelasticity in wind tunnels, aeroservoelasticity, nonlinear aeroelasticity, aeroelasticity problems in turbomachines, rotary-wing aeroelasticity with application to VTOL vehicles, computational aeroelasticity, structural dynamic testing and instrumentation.

A review of micro-contact physics for microelectromechanical systems (MEMS) metal contact switches

NASA Astrophysics Data System (ADS)

Toler, Benjamin F.; Coutu, Ronald A., Jr.; McBride, John W.

2013-10-01

Innovations in relevant micro-contact areas are highlighted, these include, design, contact resistance modeling, contact materials, performance and reliability. For each area the basic theory and relevant innovations are explored. A brief comparison of actuation methods is provided to show why electrostatic actuation is most commonly used by radio frequency microelectromechanical systems designers. An examination of the important characteristics of the contact interface such as modeling and material choice is discussed. Micro-contact resistance models based on plastic, elastic-plastic and elastic deformations are reviewed. Much of the modeling for metal contact micro-switches centers around contact area and surface roughness. Surface roughness and its effect on contact area is stressed when considering micro-contact resistance modeling. Finite element models and various approaches for describing surface roughness are compared. Different contact materials to include gold, gold alloys, carbon nanotubes, composite gold-carbon nanotubes, ruthenium, ruthenium oxide, as well as tungsten have been shown to enhance contact performance and reliability with distinct trade offs for each. Finally, a review of physical and electrical failure modes witnessed by researchers are detailed and examined.

Modeling Long-term Creep Performance for Welded Nickel-base Superalloy Structures for Power Generation Systems

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

Shen, Chen; Gupta, Vipul; Huang, Shenyan

The goal of this project is to model long-term creep performance for nickel-base superalloy weldments in high temperature power generation systems. The project uses physics-based modeling methodologies and algorithms for predicting alloy properties in heterogeneous material structures. The modeling methodology will be demonstrated on a gas turbine combustor liner weldment of Haynes 282 precipitate-strengthened nickel-base superalloy. The major developments are: (1) microstructure-property relationships under creep conditions and microstructure characterization (2) modeling inhomogeneous microstructure in superalloy weld (3) modeling mesoscale plastic deformation in superalloy weld and (4) a constitutive creep model that accounts for weld and base metal microstructure and theirmore » long term evolution. The developed modeling technology is aimed to provide a more efficient and accurate assessment of a material’s long-term performance compared with current testing and extrapolation methods. This modeling technology will also accelerate development and qualification of new materials in advanced power generation systems. This document is a final technical report for the project, covering efforts conducted from October 2014 to December 2016.« less

Study of materials performance model for aircraft interiors

NASA Technical Reports Server (NTRS)

Leary, K.; Skratt, J.

1980-01-01

A demonstration version of an aircraft interior materials computer data library was developed and contains information on selected materials applicable to aircraft seats and wall panels, including materials for the following: panel face sheets, bond plies, honeycomb, foam, decorative film systems, seat cushions, adhesives, cushion reinforcements, fire blocking layers, slipcovers, decorative fabrics and thermoplastic parts. The information obtained for each material pertains to the material's performance in a fire scenario, selected material properties and several measures of processability.

On the influence of pseudoelastic material behaviour in planar shape-memory tubular continuum structures

NASA Astrophysics Data System (ADS)

Greiner-Petter, Christoph; Sattel, Thomas

2017-12-01

For planar tubular continuum structures based on precurved shape memory alloy tubes a beam model with respect to the pseudoelastic material behaviour of NiTi is derived. Thereunto a constitutive material law respecting tension-compression asymmetry as well as hysteresis is used. The beam model is then employed to calculate equilibrium curvatures of concentric tube assemblies without clearance between the tubes. In a second step, the influence of clearance is approximated to account for non-concentric tube assemblies. These elastokinematic results are integrated into a purely kinematic model to describe the cannula path under the presence of material hysteresis and clearance. Finally a photogrammetric measurement system is used to track the path of an exemplary two-tube continuum structure to examine the accuracy of the proposed model. It is shown that material hysteresis leads to a hysteresis phenomena in the path of the tubular continuum structure.

Two-dimensional topological photonic systems

NASA Astrophysics Data System (ADS)

Sun, Xiao-Chen; He, Cheng; Liu, Xiao-Ping; Lu, Ming-Hui; Zhu, Shi-Ning; Chen, Yan-Feng

2017-09-01

The topological phase of matter, originally proposed and first demonstrated in fermionic electronic systems, has drawn considerable research attention in the past decades due to its robust transport of edge states and its potential with respect to future quantum information, communication, and computation. Recently, searching for such a unique material phase in bosonic systems has become a hot research topic worldwide. So far, many bosonic topological models and methods for realizing them have been discovered in photonic systems, acoustic systems, mechanical systems, etc. These discoveries have certainly yielded vast opportunities in designing material phases and related properties in the topological domain. In this review, we first focus on some of the representative photonic topological models and employ the underlying Dirac model to analyze the edge states and geometric phase. On the basis of these models, three common types of two-dimensional topological photonic systems are discussed: 1) photonic quantum Hall effect with broken time-reversal symmetry; 2) photonic topological insulator and the associated pseudo-time-reversal symmetry-protected mechanism; 3) time/space periodically modulated photonic Floquet topological insulator. Finally, we provide a summary and extension of this emerging field, including a brief introduction to the Weyl point in three-dimensional systems.

Thermal Effects Modeling Developed for Smart Structures

NASA Technical Reports Server (NTRS)

Lee, Ho-Jun

1998-01-01

Applying smart materials in aeropropulsion systems may improve the performance of aircraft engines through a variety of vibration, noise, and shape-control applications. To facilitate the experimental characterization of these smart structures, researchers have been focusing on developing analytical models to account for the coupled mechanical, electrical, and thermal response of these materials. One focus of current research efforts has been directed toward incorporating a comprehensive thermal analysis modeling capability. Typically, temperature affects the behavior of smart materials by three distinct mechanisms: Induction of thermal strains because of coefficient of thermal expansion mismatch 1. Pyroelectric effects on the piezoelectric elements; 2. Temperature-dependent changes in material properties; and 3. Previous analytical models only investigated the first two thermal effects mechanisms. However, since the material properties of piezoelectric materials generally vary greatly with temperature (see the graph), incorporating temperature-dependent material properties will significantly affect the structural deflections, sensory voltages, and stresses. Thus, the current analytical model captures thermal effects arising from all three mechanisms through thermopiezoelectric constitutive equations. These constitutive equations were incorporated into a layerwise laminate theory with the inherent capability to model both the active and sensory response of smart structures in thermal environments. Corresponding finite element equations were formulated and implemented for both the beam and plate elements to provide a comprehensive thermal effects modeling capability.

Noise Modeling From Conductive Shields Using Kirchhoff Equations.

PubMed

Sandin, Henrik J; Volegov, Petr L; Espy, Michelle A; Matlashov, Andrei N; Savukov, Igor M; Schultz, Larry J

2010-10-09

Progress in the development of high-sensitivity magnetic-field measurements has stimulated interest in understanding the magnetic noise of conductive materials, especially of magnetic shields based on high-permeability materials and/or high-conductivity materials. For example, SQUIDs and atomic magnetometers have been used in many experiments with mu-metal shields, and additionally SQUID systems frequently have radio frequency shielding based on thin conductive materials. Typical existing approaches to modeling noise only work with simple shield and sensor geometries while common experimental setups today consist of multiple sensor systems with complex shield geometries. With complex sensor arrays used in, for example, MEG and Ultra Low Field MRI studies, knowledge of the noise correlation between sensors is as important as knowledge of the noise itself. This is crucial for incorporating efficient noise cancelation schemes for the system. We developed an approach that allows us to calculate the Johnson noise for arbitrary shaped shields and multiple sensor systems. The approach is efficient enough to be able to run on a single PC system and return results on a minute scale. With a multiple sensor system our approach calculates not only the noise for each sensor but also the noise correlation matrix between sensors. Here we will show how the algorithm can be implemented.

A prototype knowledge-based decision support system for industrial waste management. Part 1: The decision support system

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

Boyle, C.A.; Baetz, B.W.

1998-12-31

Although there are a number of expert systems available which are designed to assist in resolving environmental problems, there is still a need for a system which would assist managers in determining waste management options for all types of wastes from one or more industrial plants, giving priority to sustainable use of resources, reuse and recycling. A prototype model was developed to determine the potentials for reuse and recycling of waste materials, to select the treatments needed to recycle waste materials or for treatment before disposal, and to determine potentials for co-treatment of wastes. A knowledge-based decision support system wasmore » then designed using this model. This paper describes the prototype model, the developed knowledge-based decision support system, the input and storage of data within the system and the inference engine developed for the system to determine the treatment options for the wastes. Options for sorting and selecting treatment trains are described, along with a discussion of the limitations of the approach and future developments needed for the system.« less

Modeling Framework for Fracture in Multiscale Cement-Based Material Structures

PubMed Central

Qian, Zhiwei; Schlangen, Erik; Ye, Guang; van Breugel, Klaas

2017-01-01

Multiscale modeling for cement-based materials, such as concrete, is a relatively young subject, but there are already a number of different approaches to study different aspects of these classical materials. In this paper, the parameter-passing multiscale modeling scheme is established and applied to address the multiscale modeling problem for the integrated system of cement paste, mortar, and concrete. The block-by-block technique is employed to solve the length scale overlap challenge between the mortar level (0.1–10 mm) and the concrete level (1–40 mm). The microstructures of cement paste are simulated by the HYMOSTRUC3D model, and the material structures of mortar and concrete are simulated by the Anm material model. Afterwards the 3D lattice fracture model is used to evaluate their mechanical performance by simulating a uniaxial tensile test. The simulated output properties at a lower scale are passed to the next higher scale to serve as input local properties. A three-level multiscale lattice fracture analysis is demonstrated, including cement paste at the micrometer scale, mortar at the millimeter scale, and concrete at centimeter scale. PMID:28772948

Multi-regime transport model for leaching behavior of heterogeneous porous materials.

PubMed

Sanchez, F; Massry, I W; Eighmy, T; Kosson, D S

2003-01-01

Utilization of secondary materials in civil engineering applications (e.g. as substitutes for natural aggregates or binder constituents) requires assessment of the physical and environment properties of the product. Environmental assessment often necessitates evaluation of the potential for constituent release through leaching. Currently most leaching models used to estimate long-term field performance assume that the species of concern is uniformly dispersed in a homogeneous porous material. However, waste materials are often comprised of distinct components such as coarse or fine aggregates in a cement concrete or waste encapsulated in a stabilized matrix. The specific objectives of the research presented here were to (1) develop a one-dimensional, multi-regime transport model (i.e. MRT model) to describe the release of species from heterogeneous porous materials and, (2) evaluate simple limit cases using the model for species when release is not dependent on pH. Two different idealized model systems were considered: (1) a porous material contaminated with the species of interest and containing inert aggregates and, (2) a porous material containing the contaminant of interest only in the aggregates. The effect of three factors on constituent release were examined: (1) volume fraction of material occupied by the aggregates compared to a homogeneous porous material, (2) aggregate size and, (3) differences in mass transfer rates between the binder and the aggregates. Simulation results confirmed that assuming homogeneous materials to evaluate the release of contaminants from porous waste materials may result in erroneous long-term field performance assessment.

A Computer Code for Dynamic Stress Analysis of Media-Structure Problems with Nonlinearities (SAMSON). Volume III. User’s Manual.

DTIC Science & Technology

NONLINEAR SYSTEMS, LINEAR SYSTEMS, SUBROUTINES , SOIL MECHANICS, INTERFACES, DYNAMICS, LOADS(FORCES), FORCE(MECHANICS), DAMPING, ACCELERATION, ELASTIC...PROPERTIES, PLASTIC PROPERTIES, CRACKS , REINFORCING MATERIALS , COMPOSITE MATERIALS , FAILURE(MECHANICS), MECHANICAL PROPERTIES, INSTRUCTION MANUALS, DIGITAL COMPUTERS...STRESSES, *COMPUTER PROGRAMS), (*STRUCTURES, STRESSES), (*DATA PROCESSING, STRUCTURAL PROPERTIES), SOILS , STRAIN(MECHANICS), MATHEMATICAL MODELS

Observations of Isotope Fractionation in Prestellar Cores: Interstellar Origin of Meteoritic Hot Spot?

NASA Technical Reports Server (NTRS)

Milam, S. N.; Charnley, S. B.

2011-01-01

Isotopically fractionated material is found in many solar system objects, including meteorites and comets. It is thought, in some cases, to trace interstellar material that was incorporated into the solar system without undergoing significant processing. Here, we show the results of models and observations of the nitrogen and carbon fractionation in proto-stellar cores.

Performance of Sequoyah Containment Anchorage System

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

Fanous, F.; Greimann, L.; Wassef, W.

1993-01-01

Deformation of a steel containment anchorage system during a severe accident may result in a leakage path at the containment boundaries. Current design criteria are based on either ductile or brittle failure modes of headed bolts that do not account for factors such as cracking of the containment basemat or deformation of the anchor bolt that may affect the behavior of the containment anchorage system. The purpose of this study was to investigate the performance of a typical ice condenser containment`s anchorage system. This was accomplished by analyzing the Sequoyah Containment Anchorage System. Based on a strength of materials approachmore » and assuming that the anchor bolts are resisting the uplift caused by the internal pressure, one can estimate that the failure of the anchor bolts would occur at a containment pressure of 79 psig. To verify these results and to calibrate the strength of materials equation, the Sequoyah containment anchorage system was analyzed with the ABAQUS program using a three-dimensional, finite-element model. The model included portions of the steel containment building, shield building, anchor bolt assembly, reinforced concrete mat and soil foundation material.« less

Effective Materials Property Information Management for the 21st Century

NASA Technical Reports Server (NTRS)

Ren, Weiju; Cebon, David; Arnold, Steve

2009-01-01

This paper discusses key principles for the development of materials property information management software systems. There are growing needs for automated materials information management in various organizations. In part these are fueled by the demands for higher efficiency in material testing, product design and engineering analysis. But equally important, organizations are being driven by the need for consistency, quality and traceability of data, as well as control of access to sensitive information such as proprietary data. Further, the use of increasingly sophisticated nonlinear, anisotropic and multi-scale engineering analyses requires both processing of large volumes of test data for development of constitutive models and complex materials data input for Computer-Aided Engineering (CAE) software. And finally, the globalization of economy often generates great needs for sharing a single "gold source" of materials information between members of global engineering teams in extended supply chains. Fortunately, material property management systems have kept pace with the growing user demands and evolved to versatile data management systems that can be customized to specific user needs. The more sophisticated of these provide facilities for: (i) data management functions such as access, version, and quality controls; (ii) a wide range of data import, export and analysis capabilities; (iii) data "pedigree" traceability mechanisms; (iv) data searching, reporting and viewing tools; and (v) access to the information via a wide range of interfaces. In this paper the important requirements for advanced material data management systems, future challenges and opportunities such as automated error checking, data quality characterization, identification of gaps in datasets, as well as functionalities and business models to fuel database growth and maintenance are discussed.

Simulation analysis of an integrated model for dynamic cellular manufacturing system

NASA Astrophysics Data System (ADS)

Hao, Chunfeng; Luan, Shichao; Kong, Jili

2017-05-01

Application of dynamic cellular manufacturing system (DCMS) is a well-known strategy to improve manufacturing efficiency in the production environment with high variety and low volume of production. Often, neither the trade-off of inter and intra-cell material movements nor the trade-off of hiring and firing of operators are examined in details. This paper presents simulation results of an integrated mixed-integer model including sensitivity analysis for several numerical examples. The comprehensive model includes cell formation, inter and intracellular materials handling, inventory and backorder holding, operator assignment (including resource adjustment) and flexible production routing. The model considers multi-production planning with flexible resources (machines and operators) where each period has different demands. The results verify the validity and sensitivity of the proposed model using a genetic algorithm.

Synergistic Integration of Experimental and Simulation Approaches for the de Novo Design of Silk-Based Materials.

PubMed

Huang, Wenwen; Ebrahimi, Davoud; Dinjaski, Nina; Tarakanova, Anna; Buehler, Markus J; Wong, Joyce Y; Kaplan, David L

2017-04-18

Tailored biomaterials with tunable functional properties are crucial for a variety of task-specific applications ranging from healthcare to sustainable, novel bio-nanodevices. To generate polymeric materials with predictive functional outcomes, exploiting designs from nature while morphing them toward non-natural systems offers an important strategy. Silks are Nature's building blocks and are produced by arthropods for a variety of uses that are essential for their survival. Due to the genetic control of encoded protein sequence, mechanical properties, biocompatibility, and biodegradability, silk proteins have been selected as prototype models to emulate for the tunable designs of biomaterial systems. The bottom up strategy of material design opens important opportunities to create predictive functional outcomes, following the exquisite polymeric templates inspired by silks. Recombinant DNA technology provides a systematic approach to recapitulate, vary, and evaluate the core structure peptide motifs in silks and then biosynthesize silk-based polymers by design. Post-biosynthesis processing allows for another dimension of material design by controlled or assisted assembly. Multiscale modeling, from the theoretical prospective, provides strategies to explore interactions at different length scales, leading to selective material properties. Synergy among experimental and modeling approaches can provide new and more rapid insights into the most appropriate structure-function relationships to pursue while also furthering our understanding in terms of the range of silk-based systems that can be generated. This approach utilizes nature as a blueprint for initial polymer designs with useful functions (e.g., silk fibers) but also employs modeling-guided experiments to expand the initial polymer designs into new domains of functional materials that do not exist in nature. The overall path to these new functional outcomes is greatly accelerated via the integration of modeling with experiment. In this Account, we summarize recent advances in understanding and functionalization of silk-based protein systems, with a focus on the integration of simulation and experiment for biopolymer design. Spider silk was selected as an exemplary protein to address the fundamental challenges in polymer designs, including specific insights into the role of molecular weight, hydrophobic/hydrophilic partitioning, and shear stress for silk fiber formation. To expand current silk designs toward biointerfaces and stimuli responsive materials, peptide modules from other natural proteins were added to silk designs to introduce new functions, exploiting the modular nature of silk proteins and fibrous proteins in general. The integrated approaches explored suggest that protein folding, silk volume fraction, and protein amino acid sequence changes (e.g., mutations) are critical factors for functional biomaterial designs. In summary, the integrated modeling-experimental approach described in this Account suggests a more rationally directed and more rapid method for the design of polymeric materials. It is expected that this combined use of experimental and computational approaches has a broad applicability not only for silk-based systems, but also for other polymer and composite materials.

[Development of medical supplies management system].

PubMed

Zhong, Jianping; Shen, Beijun; Zhu, Huili

2012-11-01

This paper adopts advanced information technology to manage medical supplies, in order to improve the medical supplies management level and reduce material cost. It develops a Medical Supplies Management System with B/S and C/S mixed structure, optimizing material management process, building large equipment performance evaluation model, providing interface solution with HIS, and realizing real-time information briefing of high value material's consumption. The medical materials are managed during its full life-cycle. The material consumption of the clinical departments is monitored real-timely. Through the closed-loop management with pre-event budget, mid-event control and after-event analysis, it realizes the final purpose of management yielding benefit.

Stress Transfer and Structural Failure of Bilayered Material Systems

NASA Astrophysics Data System (ADS)

Prieto-Munoz, Pablo Arthur

Bilayered material systems are common in naturally formed or artificially engineered structures. Understanding how loads transfer within these structural systems is necessary to predict failure and develop effective designs. Existing methods for evaluating the stress transfer in bilayered materials are limited to overly simplified models or require experimental calibration. As a result, these methods have failed to accurately account for such structural failures as the creep induced roofing panel collapse of Boston's I-90 connector tunnel, which was supported by adhesive anchors. The one-dimensional stress analyses currently used for adhesive anchor design cannot account for viscoelastic creep failure, and consequently results in dangerously under-designed structural systems. In this dissertation, a method for determining the two-dimensional stress and displacement fields for a generalized bilayered material system is developed, and proposes a closed-form analytical solution. A general linear-elastic solution is first proposed by decoupling the elastic governing equations from one another through the so-called plane assumption. Based on this general solution, an axisymmetric problem and a plane strain problem are formulated. These are applied to common bilayered material systems such as: (1) concrete adhesive anchors, (2) material coatings, (3) asphalt pavements, and (4) layered sedimentary rocks. The stress and displacement fields determined by this analytical analysis are validated through the use of finite element models. Through the correspondence principle, the linear-elastic solution is extended to consider time-dependent viscoelastic material properties, thus facilitating the analysis of adhesive anchors and asphalt pavements while incorporating their viscoelastic material behavior. Furthermore, the elastic stress analysis can explain the fracturing phenomenon of material coatings, pavements, and layered rocks, successfully predicting their fracture saturation ratio---which is the ratio of fracture spacing to the thickness of the weak layer where an increase in load will not cause any new fractures to form. Moreover, these specific material systems are looked at in the context of existing and novel experimental results, further demonstrating the advantage of the stress transfer analysis proposed. This research provides a closed-form stress solution for various structural systems that is applied to different failure analyses. The versatility of this method is in the flexibility and the ease upon which the stress and displacement field results can be applied to existing stress- or displacement-based structural failure criteria. As presented, this analysis can be directly used to: (1) design adhesive anchoring systems for long-term creep loading, (2) evaluate the fracture mechanics behind bilayered material coatings and pavement overlay systems, and (3) determine the fracture spacing to layer thickness ratio of layered sedimentary rocks. As is shown in the four material systems presented, this general solution has far reaching applications in facilitating design and analysis of typical bilayered structural systems.

Wormhole Formation in RSRM Nozzle Joint Backfill

NASA Technical Reports Server (NTRS)

Stevens, J.

2000-01-01

The RSRM nozzle uses a barrier of RTV rubber upstream of the nozzle O-ring seals. Post flight inspection of the RSRM nozzle continues to reveal occurrence of "wormholes" into the RTV backfill. The term "wormholes", sometimes called "gas paths", indicates a gas flow path not caused by pre-existing voids, but by a little-understood internal failure mode of the material during motor operation. Fundamental understanding of the mechanics of the RSRM nozzle joints during motor operation, nonlinear viscoelastic characterization of the RTV backfill material, identification of the conditions that predispose the RTV to form wormholes, and screening of candidate replacement materials is being pursued by a joint effort between Thiokol Propulsion, NASA, and the Army Propulsion & Structures Directorate at Redstone Arsenal. The performance of the RTV backfill in the joint is controlled by the joint environment. Joint movement, which applies a tension and shear load on the material, coupled with the introduction of high pressure gas in combination create an environment that exceeds the capability of the material to withstand the wormhole effect. Little data exists to evaluate why the material fails under the modeled joint conditions, so an effort to characterize and evaluate the material under these conditions was undertaken. Viscoelastic property data from characterization testing will anchor structural analysis models. Data over a range of temperatures, environmental pressures, and strain rates was used to develop a nonlinear viscoelastic model to predict material performance, develop criteria for replacement materials, and quantify material properties influencing wormhole growth. Three joint simulation analogs were developed to analyze and validate joint thermal barrier (backfill) material performance. Two exploratory tests focus on detection of wormhole failure under specific motor operating conditions. A "validation" test system provides data to "validate" computer models and predictions. Finally, two candidate replacement materials are being screened and "validated" using the developed test systems.

Optimization-Based Inverse Identification of the Parameters of a Concrete Cap Material Model

NASA Astrophysics Data System (ADS)

Král, Petr; Hokeš, Filip; Hušek, Martin; Kala, Jiří; Hradil, Petr

2017-10-01

Issues concerning the advanced numerical analysis of concrete building structures in sophisticated computing systems currently require the involvement of nonlinear mechanics tools. The efforts to design safer, more durable and mainly more economically efficient concrete structures are supported via the use of advanced nonlinear concrete material models and the geometrically nonlinear approach. The application of nonlinear mechanics tools undoubtedly presents another step towards the approximation of the real behaviour of concrete building structures within the framework of computer numerical simulations. However, the success rate of this application depends on having a perfect understanding of the behaviour of the concrete material models used and having a perfect understanding of the used material model parameters meaning. The effective application of nonlinear concrete material models within computer simulations often becomes very problematic because these material models very often contain parameters (material constants) whose values are difficult to obtain. However, getting of the correct values of material parameters is very important to ensure proper function of a concrete material model used. Today, one possibility, which permits successful solution of the mentioned problem, is the use of optimization algorithms for the purpose of the optimization-based inverse material parameter identification. Parameter identification goes hand in hand with experimental investigation while it trying to find parameter values of the used material model so that the resulting data obtained from the computer simulation will best approximate the experimental data. This paper is focused on the optimization-based inverse identification of the parameters of a concrete cap material model which is known under the name the Continuous Surface Cap Model. Within this paper, material parameters of the model are identified on the basis of interaction between nonlinear computer simulations, gradient based and nature inspired optimization algorithms and experimental data, the latter of which take the form of a load-extension curve obtained from the evaluation of uniaxial tensile test results. The aim of this research was to obtain material model parameters corresponding to the quasi-static tensile loading which may be further used for the research involving dynamic and high-speed tensile loading. Based on the obtained results it can be concluded that the set goal has been reached.

Continuum of Medical Education in Obstetrics and Gynecology.

ERIC Educational Resources Information Center

Dohner, Charles W.; Hunter, Charles A., Jr.

1980-01-01

Over the past eight years the obstetric and gynecology specialty has applied a system model of instructional planning to the continuum of medical education. The systems model of needs identification, preassessment, instructional objectives, instructional materials, learning experiences; and evaluation techniques directly related to objectives was…

Development of FIAT-Based Parametric Thermal Protection System Mass Estimating Relationships for NASA's Multi-Mission Earth Entry Concept

NASA Astrophysics Data System (ADS)

Sepka, S. A.; Samareh, J. A.

2014-06-01

Mass estimating relationships have been formulated to determine a vehicle's Thermal Protection System material and required thickness for safe Earth entry. We focus on developing MERs, the resulting equations, model limitations, and model accuracy.

EMERGENCY COLLECTION SYSTEM FOR SPILLED HAZARDOUS MATERIALS

EPA Science Inventory

A prepackaged pumping and storage system for the collection and temporary containment of hazardous land spills was designed and two models developed. Each model includes a pump, hoses, furled self-deploying 26,500 l (7000 gal) capacity plastic bag array all mounted on a pallet fo...

Damage assessment of composite plate structures with material and measurement uncertainty

NASA Astrophysics Data System (ADS)

Chandrashekhar, M.; Ganguli, Ranjan

2016-06-01

Composite materials are very useful in structural engineering particularly in weight sensitive applications. Two different test models of the same structure made from composite materials can display very different dynamic behavior due to large uncertainties associated with composite material properties. Also, composite structures can suffer from pre-existing imperfections like delaminations, voids or cracks during fabrication. In this paper, we show that modeling and material uncertainties in composite structures can cause considerable problem in damage assessment. A recently developed C0 shear deformable locking free refined composite plate element is employed in the numerical simulations to alleviate modeling uncertainty. A qualitative estimate of the impact of modeling uncertainty on the damage detection problem is made. A robust Fuzzy Logic System (FLS) with sliding window defuzzifier is used for delamination damage detection in composite plate type structures. The FLS is designed using variations in modal frequencies due to randomness in material properties. Probabilistic analysis is performed using Monte Carlo Simulation (MCS) on a composite plate finite element model. It is demonstrated that the FLS shows excellent robustness in delamination detection at very high levels of randomness in input data.

Design and simulation of integration system between automated material handling system and manufacturing layout in the automotive assembly line

NASA Astrophysics Data System (ADS)

Seha, S.; Zamberi, J.; Fairu, A. J.

2017-10-01

Material handling system (MHS) is an important part for the productivity plant and has recognized as an integral part of today’s manufacturing system. Currently, MHS has growth tremendously with its technology and equipment type. Based on the case study observation, the issue involving material handling system contribute to the reduction of production efficiency. This paper aims to propose a new design of integration between material handling and manufacturing layout by investigating the influences of layout and material handling system. A method approach tool using Delmia Quest software is introduced and the simulation result is used to assess the influences of the integration between material handling system and manufacturing layout in the performance of automotive assembly line. The result show, the production of assembly line output increases more than 31% from the current system. The source throughput rate average value went up to 252 units per working hour in model 3 and show the effectiveness of the pick-to-light system as efficient storage equipment. Thus, overall result shows, the application of AGV and the pick-to-light system gave a large significant effect in the automotive assembly line. Moreover, the change of layout also shows a large significant improvement to the performance.

Molecular- and Domain-level Microstructure-dependent Material Model for Nano-segregated Polyurea

DTIC Science & Technology

2013-04-15

material subroutine VUMAT of ABAQUS /Explicit (Dassault Systems, 2010), a commercial finite element code. This subroutine is called by the ABAQUS solver...rate of change of the local internal thermal energy is equal to the corresponding rate of dissipative work. Critical assessment of this model identified...The model also takes into account the plastic expansion or contraction of voids and therefore the stresses are appropriately modified to account for

Method for Predicting and Optimizing System Parameters for Electrospinning System

NASA Technical Reports Server (NTRS)

Wincheski, Russell A. (Inventor)

2011-01-01

An electrospinning system using a spinneret and a counter electrode is first operated for a fixed amount of time at known system and operational parameters to generate a fiber mat having a measured fiber mat width associated therewith. Next, acceleration of the fiberizable material at the spinneret is modeled to determine values of mass, drag, and surface tension associated with the fiberizable material at the spinneret output. The model is then applied in an inversion process to generate predicted values of an electric charge at the spinneret output and an electric field between the spinneret and electrode required to fabricate a selected fiber mat design. The electric charge and electric field are indicative of design values for system and operational parameters needed to fabricate the selected fiber mat design.

Azole energetic materials: Initial mechanisms for the energy release from electronical excited nitropyrazoles

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

Yuan, Bing; Yu, Zijun; Bernstein, Elliot R., E-mail: erb@lamar.Colostate.edu

2014-01-21

Decomposition of energetic material 3,4-dinitropyrazole (DNP) and two model molecules 4-nitropyrazole and 1-nitropyrazole is investigated both theoretically and experimentally. The initial decomposition mechanisms for these three nitropyrazoles are explored with complete active space self-consistent field (CASSCF) level. The NO molecule is observed as an initial decomposition product from all three materials subsequent to UV excitation. Observed NO products are rotationally cold (<50 K) for all three systems. The vibrational temperature of the NO product from DNP is (3850 ± 50) K, 1350 K hotter than that of the two model species. Potential energy surface calculations at the CASSCF(12,8)/6-31+G(d) level illustratemore » that conical intersections plays an essential role in the decomposition mechanism. Electronically excited S{sub 2} nitropyraozles can nonradiatively relax to lower electronic states through (S{sub 2}/S{sub 1}){sub CI} and (S{sub 1}/S{sub 0}){sub CI} conical intersection and undergo a nitro-nitrite isomerization to generate NO product either in the S{sub 1} state or S{sub 0} state. In model systems, NO is generated in the S{sub 1} state, while in the energetic material DNP, NO is produced on the ground state surface, as the S{sub 1} decomposition pathway is energetically unavailable. The theoretically predicted mechanism is consistent with the experimental results, as DNP decomposes in a lower electronic state than do the model systems and thus the vibrational energy in the NO product from DNP should be hotter than from the model systems. The observed rotational energy distributions for NO are consistent with the final structures of the respective transition states for each molecule.« less

Model Mismatch Paradigm for Probe based Nanoscale Imaging

NASA Astrophysics Data System (ADS)

Agarwal, Pranav

Scanning Probe Microscopes (SPMs) are widely used for investigation of material properties and manipulation of matter at the nanoscale. These instruments are considered critical enablers of nanotechnology by providing the only technique for direct observation of dynamics at the nanoscale and affecting it with sub Angstrom resolution. Current SPMs are limited by low throughput and lack of quantitative measurements of material properties. Various applications like the high density data storage, sub-20 nm lithography, fault detection and functional probing of semiconductor circuits, direct observation of dynamical processes involved in biological samples viz. motor proteins and transport phenomena in various materials demand high throughput operation. Researchers involved in material characterization at nanoscale are interested in getting quantitative measurements of stiffness and dissipative properties of various materials in a least invasive manner. In this thesis, system theoretic concepts are used to address these limitations. The central tenet of the thesis is to model, the known information about the system and then focus on perturbations of these known dynamics or model, to sense the effects due to changes in the environment such as changes in material properties or surface topography. Thus a model mismatch paradigm for probe based nanoscale imaging is developed. The topic is developed by presenting physics based modeling of a particular mode of operation of SPMs called the dynamic mode operation. This mode is modeled as a forced Lure system where a linear time invariant system is in feedback with an unknown static memoryless nonlinearity. Tools from averaging theory are used to tame this complex nonlinear system by approximating it as a linear system with time varying parameters. Material properties are thus transformed from being parameters of unknown nonlinear functions to being unknown coefficients of a linear plant. The first contribution of this thesis deals with real time detection and reduction of spurious areas in the image which are also known as probe-loss areas. These areas become severely detrimental during high speed operations. The detection strategy is based on thresholding of a distance measure, which captures the difference between sensor models in absence and presence of probe-loss. A switching gain control strategy based on the output of a Kalman Filter is used to reduce probe-loss areas in real time. The efficacy of this technique is demonstrated through experimental results showing increased image fidelity at scan rates that are 10 times faster than conventional scan rates. The second contribution of this thesis deals with developing multi-frequency input excitation strategy and deriving a bias compensated adaptive parameter estimation strategy to determine the instantaneous equivalent cantilever model. This is used to address the challenge of quantitative imaging at high bandwidth operation by relating the estimated plant coefficients to conservative and dissipative components of tip-sample interaction. The efficacy of the technique is demonstrated for quantitative material characterization of a polymer sample, resulting in material information not previously obtainable during dynamic mode operation. This information is obtained at speeds which are two orders faster than existing techniques. Quantitative verification strategies for the accuracy of estimated parameters are presented. The third contribution of this thesis deals with developing real time tractable models and characterization methodology for an electrostatically actuated MEMS cantilever with an integrated solid state thermal sensor. Appropriate modeling assumptions are made to delineate various nonlinear forces on the cantilever viz. electrostatic force, tip-sample interaction force and capacitive coupling. Experimental strategy is presented to measure the thermal sensing transfer function from DC-100kHz. A quantitative match between experimental and simulated data is obtained for the large range nonlinearities and small signal dynamics.

Constitutive modeling and control of 1D smart composite structures

NASA Astrophysics Data System (ADS)

Briggs, Jonathan P.; Ostrowski, James P.; Ponte-Castaneda, Pedro

1998-07-01

Homogenization techniques for determining effective properties of composite materials may provide advantages for control of stiffness and strain in systems using hysteretic smart actuators embedded in a soft matrix. In this paper, a homogenized model of a 1D composite structure comprised of shape memory alloys and a rubber-like matrix is presented. With proportional and proportional/integral feedback, using current as the input state and global strain as an error state, implementation scenarios include the use of tractions on the boundaries and a nonlinear constitutive law for the matrix. The result is a simple model which captures the nonlinear behavior of the smart composite material system and is amenable to experiments with various control paradigms. The success of this approach in the context of the 1D model suggests that the homogenization method may prove useful in investigating control of more general smart structures. Applications of such materials could include active rehabilitation aids, e.g. wrist braces, as well as swimming/undulating robots, or adaptive molds for manufacturing processes.

Life-cycle assessment of the municipal solid waste management system in Hangzhou, China (EASEWASTE).

PubMed

Zhao, Yan; Wang, Hong-Tao; Lu, Wen-Jing; Damgaard, Anders; Christensen, Thomas H

2009-06-01

With the purpose of assessing the environmental impacts and benefits of the current municipal solid waste management system and two modified systems, EASEWASTE, a life-cycle-based model, was used to evaluate the waste system of Hangzhou city in China. An integrated model was established, including waste generation, collection, transportation, treatment, disposal and accompanying external processes. The results showed that CH(4) released from landfilling was the primary pollutant contributing to global warming, and HCl and NH(3) from incineration contributed most to acidification. Material recycling and incineration with energy recovery were important because of the induced savings in material production based on virgin materials and in energy production based on coal combustion. A modified system in which waste is transported to the nearest incinerators would be relatively better than the current system, mainly due to the decrease of pollution from landfilled waste and the increase in energy production from waste avoiding energy production by traditional power plants. A ban on free plastic bags for shopping was shown to reduce most environmental impacts due to saved oil resources and other materials used in producing the plastic bags. Sensitivity analysis confirmed the robustness of the results. LCA methodology and a model like EASEWASTE are very suitable for evaluating the overall environmental consequences, and can be used for decision support and strategic planning in developing countries such as China where pollution control has become increasingly important with the rapid increase of waste generation as well as the increasing public awareness of environmental protection.

Americium, Cesium, and Plutonium Colloid-Facilitated Transport in a Groundwater/Bentonite/Fracture Fill Material System: Column Experiments and Model Results

NASA Astrophysics Data System (ADS)

Dittrich, T. M.; Boukhalfa, H.; Reimus, P. W.

2014-12-01

The objective of this study was to investigate and quantify the effects of desorption kinetics and colloid transport on radionuclides with different sorption affinities. We focused on quantifying transport mechanisms important for upscaling in time and distance. This will help determine the long-term fate and transport of radionuclides to aid in risk assessments. We selected a fractured/weathered granodiorite at the Grimsel Test Site (GTS) in Switzerland as a model crystalline rock repository system because the system has been thoroughly studied and field experiments involving radionuclides have already been conducted. Working on this system provides a unique opportunity to compare lab experiments with field-scale observations. Weathered fracture fill material (FFM) and bentonite used as backfill at the GTS were characterized (e.g., BET, SEM/EDS, QXRD), and batch and breakthrough column experiments were conducted. Solutions were prepared in synthetic groundwaters that matched the natural water chemistry. FFM samples were crushed, rinsed, sieved (150-355 μm), and equilibrated with synthetic groundwater. Bentonite was crushed, sodium-saturated, equilibrated with synthetic groundwater, and settled to yield a stable suspension. Suspensions were equilibrated with Am, Cs, or Pu. All experiments were conducted with Teflon®materials to limit sorption to system components. After radionuclide/colloid injections reached stability, radionuclide-free solutions were injected to observe the desorption and release behavior. Aliquots of effluent were measured for pH, colloid concentration, and total and dissolved radionuclides. Unanalyzed effluent from the first column was then injected through a second column of fresh material. The process was repeated for a third column and the results of all three breakthrough curves were modeled with a multi-site/multi-rate MATLAB code to elucidate the sorption rate coefficients and binding site densities of the bentonite colloids and fracture fill material. Nearly 50% of the sorbed Am was exchanged from the colloids to the fracture filling material in each of the three columns; whereas, less Cs and Pu was desorbed with each pass through a new column. Using a two-site kinetic model allowed for interrogation of desorption rates and dominant transport parameters.

Fundamental mass transfer modeling of emission of volatile organic compounds from building materials

NASA Astrophysics Data System (ADS)

Bodalal, Awad Saad

In this study, a mass transfer theory based model is presented for characterizing the VOC emissions from building materials. A 3-D diffusion model is developed to describe the emissions of volatile organic compounds (VOCs) from individual sources. Then the formulation is extended to include the emissions from composite sources (system comprising an assemblage of individual sources). The key parameters for the model (The diffusion coefficient of the VOC in the source material D, and the equilibrium partition coefficient k e) were determined independently (model parameters are determined without the use of chamber emission data). This procedure eliminated to a large extent the need for emission testing using environmental chambers, which is costly, time consuming, and may be subject to confounding sink effects. An experimental method is developed and implemented to measure directly the internal diffusion (D) and partition coefficients ( ke). The use of the method is illustrated for three types of VOC's: (i) Aliphatic Hydrocarbons, (ii) Aromatic Hydrocarbons and ( iii) Aldehydes, through typical dry building materials (carpet, plywood, particleboard, vinyl floor tile, gypsum board, sub-floor tile and OSB). Then correlations for predicting D and ke based solely on commonly available properties such as molecular weight and vapour pressure were proposed for each product and type of VOC. These correlations can be used to estimate the D and ke when direct measurement data are not available, and thus facilitate the prediction of VOC emissions from the building materials using mass transfer theory. The VOC emissions from a sub-floor material (made of the recycled automobile tires), and a particleboard are measured and predicted. Finally, a mathematical model to predict the diffusion coefficient through complex sources (floor adhesive) as a function of time was developed. Then this model (for diffusion coefficient in complex sources) was used to predict the emission rate from material system (namely, substrate//glue//vinyl tile).

Metallic Rotor Sizing and Performance Model for Flywheel Systems

NASA Technical Reports Server (NTRS)

Moore, Camille J.; Kraft, Thomas G.

2012-01-01

The NASA Glenn Research Center (GRC) is developing flywheel system requirements and designs for terrestrial and spacecraft applications. Several generations of flywheels have been designed and tested at GRC using in-house expertise in motors, magnetic bearings, controls, materials and power electronics. The maturation of a flywheel system from the concept phase to the preliminary design phase is accompanied by maturation of the Integrated Systems Performance model, where estimating relationships are replaced by physics based analytical techniques. The modeling can incorporate results from engineering model testing and emerging detail from the design process.

Dynamic Shock Response of an S2 Glass/SC15 Epoxy Woven Fabric Composite Material System

NASA Astrophysics Data System (ADS)

Key, Christopher; Alexander, Scott; Harstad, Eric; Schumacher, Shane

2017-06-01

The use of S2 glass/SC15 epoxy woven fabric composite materials for blast and ballistic protection has been an area of on-going research over the past decade. In order to accurately model this material system within potential applications under extreme loading conditions, a well characterized and well understood anisotropic equation of state (EOS) is needed. This work details both an experimental program and associated analytical modelling efforts which aim to provide better physical understanding of the anisotropic EOS behavior of this material. Experimental testing focused on planar shock impact tests loading the composite to peak pressures of 15 GPa in both the through-thickness and on-fiber orientation. Test results highlighted the anisotropic response of the material and provided a basis by which the associated numeric micromechanical investigation was compared. Results of the combined experimental and numerical modelling investigation provided insights into not only the constituent material influence on the composite response but also the importance of the geometrical configuration of the plain weave microstructure and the stochastic significance of the microstructural configuration. Sandia National Laboratories is a multi-mission laboratory operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin company, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

The application of artificial intelligence in the optimal design of mechanical systems

NASA Astrophysics Data System (ADS)

Poteralski, A.; Szczepanik, M.

2016-11-01

The paper is devoted to new computational techniques in mechanical optimization where one tries to study, model, analyze and optimize very complex phenomena, for which more precise scientific tools of the past were incapable of giving low cost and complete solution. Soft computing methods differ from conventional (hard) computing in that, unlike hard computing, they are tolerant of imprecision, uncertainty, partial truth and approximation. The paper deals with an application of the bio-inspired methods, like the evolutionary algorithms (EA), the artificial immune systems (AIS) and the particle swarm optimizers (PSO) to optimization problems. Structures considered in this work are analyzed by the finite element method (FEM), the boundary element method (BEM) and by the method of fundamental solutions (MFS). The bio-inspired methods are applied to optimize shape, topology and material properties of 2D, 3D and coupled 2D/3D structures, to optimize the termomechanical structures, to optimize parameters of composites structures modeled by the FEM, to optimize the elastic vibrating systems to identify the material constants for piezoelectric materials modeled by the BEM and to identify parameters in acoustics problem modeled by the MFS.

R and T report: Goddard Space Flight Center

NASA Technical Reports Server (NTRS)

Soffen, Gerald A. (Editor)

1993-01-01

The 1993 Research and Technology Report for Goddard Space Flight Center is presented. Research covered areas such as (1) flight projects; (2) space sciences including cosmology, high energy, stars and galaxies, and the solar system; (3) earth sciences including process modeling, hydrology/cryology, atmospheres, biosphere, and solid earth; (4) networks, planning, and information systems including support for mission operations, data distribution, advanced software and systems engineering, and planning/scheduling; and (5) engineering and materials including spacecraft systems, material and testing, optics and photonics and robotics.

Test model designs for advanced refractory ceramic materials

NASA Technical Reports Server (NTRS)

Tran, Huy Kim

1993-01-01

The next generation of space vehicles will be subjected to severe aerothermal loads and will require an improved thermal protection system (TPS) and other advanced vehicle components. In order to ensure the satisfactory performance system (TPS) and other advanced vehicle materials and components, testing is to be performed in environments similar to space flight. The design and fabrication of the test models should be fairly simple but still accomplish test objectives. In the Advanced Refractory Ceramic Materials test series, the models and model holders will need to withstand the required heat fluxes of 340 to 817 W/sq cm or surface temperatures in the range of 2700 K to 3000 K. The model holders should provide one dimensional (1-D) heat transfer to the samples and the appropriate flow field without compromising the primary test objectives. The optical properties such as the effective emissivity, catalytic efficiency coefficients, thermal properties, and mass loss measurements are also taken into consideration in the design process. Therefore, it is the intent of this paper to demonstrate the design schemes for different models and model holders that would accommodate these test requirements and ensure the safe operation in a typical arc jet facility.

Fluid extraction across pumping and permeable walls in the viscous limit

NASA Astrophysics Data System (ADS)

Herschlag, G.; Liu, J.-G.; Layton, A. T.

2016-04-01

In biological transport mechanisms such as insect respiration and renal filtration, fluid travels along a leaky channel allowing material exchange with systems exterior to the channel. The channels in these systems may undergo peristaltic pumping which is thought to enhance the material exchange. To date, little analytic work has been done to study the effect of pumping on material extraction across the channel walls. In this paper, we examine a fluid extraction model in which fluid flowing through a leaky channel is exchanged with fluid in a reservoir. The channel walls are allowed to contract and expand uniformly, simulating a pumping mechanism. In order to efficiently determine solutions of the model, we derive a formal power series solution for the Stokes equations in a finite channel with uniformly contracting/expanding permeable walls. This flow has been well studied in the case in which the normal velocity at the channel walls is proportional to the wall velocity. In contrast we do not assume flow that is proportional to the wall velocity, but flow that is driven by hydrostatic pressure, and we use Darcy's law to close our system for normal wall velocity. We incorporate our flow solution into a model that tracks the material pressure exterior to the channel. We use this model to examine flux across the channel-reservoir barrier and demonstrate that pumping can either enhance or impede fluid extraction across channel walls. We find that associated with each set of physical flow and pumping parameters, there are optimal reservoir conditions that maximize the amount of material flowing from the channel into the reservoir.

Model simulation and experiments of flow and mass transport through a nano-material gas filter

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

Yang, Xiaofan; Zheng, Zhongquan C.; Winecki, Slawomir

2013-11-01

A computational model for evaluating the performance of nano-material packed-bed filters was developed. The porous effects of the momentum and mass transport within the filter bed were simulated. For the momentum transport, an extended Ergun-type model was employed and the energy loss (pressure drop) along the packed-bed was simulated and compared with measurement. For the mass transport, a bulk dsorption model was developed to study the adsorption process (breakthrough behavior). Various types of porous materials and gas flows were tested in the filter system where the mathematical models used in the porous substrate were implemented and validated by comparing withmore » experimental data and analytical solutions under similar conditions. Good agreements were obtained between experiments and model predictions.« less

A Generalized Orthotropic Elasto-Plastic Material Model for Impact Analysis

NASA Astrophysics Data System (ADS)

Hoffarth, Canio

Composite materials are now beginning to provide uses hitherto reserved for metals in structural systems such as airframes and engine containment systems, wraps for repair and rehabilitation, and ballistic/blast mitigation systems. These structural systems are often subjected to impact loads and there is a pressing need for accurate prediction of deformation, damage and failure. There are numerous material models that have been developed to analyze the dynamic impact response of polymer matrix composites. However, there are key features that are missing in those models that prevent them from providing accurate predictive capabilities. In this dissertation, a general purpose orthotropic elasto-plastic computational constitutive material model has been developed to predict the response of composites subjected to high velocity impacts. The constitutive model is divided into three components - deformation model, damage model and failure model, with failure to be added at a later date. The deformation model generalizes the Tsai-Wu failure criteria and extends it using a strain-hardening-based orthotropic yield function with a non-associative flow rule. A strain equivalent formulation is utilized in the damage model that permits plastic and damage calculations to be uncoupled and capture the nonlinear unloading and local softening of the stress-strain response. A diagonal damage tensor is defined to account for the directionally dependent variation of damage. However, in composites it has been found that loading in one direction can lead to damage in multiple coordinate directions. To account for this phenomena, the terms in the damage matrix are semi-coupled such that the damage in a particular coordinate direction is a function of the stresses and plastic strains in all of the coordinate directions. The overall framework is driven by experimental tabulated temperature and rate-dependent stress-strain data as well as data that characterizes the damage matrix and failure. The developed theory has been implemented in a commercial explicit finite element analysis code, LS-DYNARTM, as MAT213. Several verification and validation tests using a commonly available carbon-fiber composite, Toyobo's T800/F3900, have been carried and the results show that the theory and implementation are efficient, robust and accurate.

Prospects for Ductility and Toughness Enhancement of Nial by Ductile Phase Reinforcement

NASA Technical Reports Server (NTRS)

Noebe, R. D.; Ritzert, F. J.; Misra, A.; Gibala, R.

1991-01-01

The use of NiAl as a structural material has been hindered by the fact that this ordered intermetallic does not exhibit significant tensile ductility or toughness at room temperature. A critical review of the operative flow and fracture mechanisms in monolithic NiAl has thus established the need for ductile phase toughening in this order system. Progress in ductile phase reinforced intermetallic systems in general and specifically NiAl-based materials has been reviewed. In addition, further clarification of the primary mechanisms involved in the flow and fracture of ductile phase reinforced alloys has evolved from ongoing investigations of several model NiAl-based materials. The mechanical behavior of these model directionally-solidified alloys (Ni-30Al and Ni-30Fe-20Al) are discussed. Finally, the prospects for developing a ductile phase toughened NiAl-based alloy and the shortcomings presently inherent in these systems are analyzed.

Ability of New Obturation Materials to Improve the Seal of the Root Canal System – A Review

PubMed Central

Zhang, Wei; Olsen, Mark; De-Deus, Gustavo; Eid, Ashraf A.; Chen, Ji-hua; Pashley, David H.; Tay, Franklin R.

2014-01-01

Objectives New obturation biomaterials have been introduced over the past decade to improve the seal of the root canal system. However, it is not clear whether they have really produced a three-dimensional impervious seal that is important for reducing diseases associated with root canal treatment. Methods A review of the literature was performed to identify models that have been employed for evaluating the seal of the root canal system. Results and Significance In-vitro and in-vivo models are not totally adept at quantifying the seal of root canals obturated with classic materials. Thus, one has to resort to clinical outcomes to examine whether there are real benefits associated with the use of recently-introduced materials for obturating root canals. However, there is no facile answer because endodontic treatment outcomes are influenced by a host of other predictors that are more likely to take precedence over the influence of obturation materials. From the perspective of clinical performance, classic root filling materials have stood the test of time. Because many of the recently-introduced materials are so new, there is not enough evidence yet to support their ability to improve clinical performance. This emphasizes the need to translate anecdotal information into clinically relevant research data on new biomaterials. PMID:24321349

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

Morgan, Michael J.

The Hydrogen Fracture Toughness Tester (HFTT) is a mechanical testing machine designed for conducting fracture mechanics tests on materials in high-pressure hydrogen gas. The tester is needed for evaluating the effects of hydrogen on the cracking properties of tritium reservoir materials. It consists of an Instron Model 8862 Electromechanical Test Frame; an Autoclave Engineering Pressure Vessel, an Electric Potential Drop Crack Length Measurement System, associated computer control and data acquisition systems, and a high-pressure hydrogen gas manifold and handling system.

The Elastic Behaviour of Sintered Metallic Fibre Networks: A Finite Element Study by Beam Theory

PubMed Central

Bosbach, Wolfram A.

2015-01-01

Background The finite element method has complimented research in the field of network mechanics in the past years in numerous studies about various materials. Numerical predictions and the planning efficiency of experimental procedures are two of the motivational aspects for these numerical studies. The widespread availability of high performance computing facilities has been the enabler for the simulation of sufficiently large systems. Objectives and Motivation In the present study, finite element models were built for sintered, metallic fibre networks and validated by previously published experimental stiffness measurements. The validated models were the basis for predictions about so far unknown properties. Materials and Methods The finite element models were built by transferring previously published skeletons of fibre networks into finite element models. Beam theory was applied as simplification method. Results and Conclusions The obtained material stiffness isn’t a constant but rather a function of variables such as sample size and boundary conditions. Beam theory offers an efficient finite element method for the simulated fibre networks. The experimental results can be approximated by the simulated systems. Two worthwhile aspects for future work will be the influence of size and shape and the mechanical interaction with matrix materials. PMID:26569603

Virtual experiments, physical validation: dental morphology at the intersection of experiment and theory

PubMed Central

Anderson, P. S. L.; Rayfield, E. J.

2012-01-01

Computational models such as finite-element analysis offer biologists a means of exploring the structural mechanics of biological systems that cannot be directly observed. Validated against experimental data, a model can be manipulated to perform virtual experiments, testing variables that are hard to control in physical experiments. The relationship between tooth form and the ability to break down prey is key to understanding the evolution of dentition. Recent experimental work has quantified how tooth shape promotes fracture in biological materials. We present a validated finite-element model derived from physical compression experiments. The model shows close agreement with strain patterns observed in photoelastic test materials and reaction forces measured during these experiments. We use the model to measure strain energy within the test material when different tooth shapes are used. Results show that notched blades deform materials for less strain energy cost than straight blades, giving insights into the energetic relationship between tooth form and prey materials. We identify a hypothetical ‘optimal’ blade angle that minimizes strain energy costs and test alternative prey materials via virtual experiments. Using experimental data and computational models offers an integrative approach to understand the mechanics of tooth morphology. PMID:22399789

An integrated material metabolism model for stocks of urban road system in Beijing, China.

PubMed

Guo, Zhen; Hu, Dan; Zhang, Fuhua; Huang, Guolong; Xiao, Qiang

2014-02-01

Rapid urbanization has greatly altered the urban metabolism of material and energy. As a significant part of the infrastructure, urban roads are being rapidly developed worldwide. Quantitative analysis of metabolic processes on urban road systems, especially the scale, composition and spatial distribution of their stocks, could help to assess the resource appropriation and potential environmental impacts, as well as improve urban metabolism models. In this paper, an integrated model, which covered all types of roads, intersection structures and ancillary facilities, was built for calculating the material stocks of urban road systems. Based on a bottom-up method, the total stocks were disassembled into a number of stock parts rather than obtained by input-output data, which provided an approach promoting data availability and inner structure understanding. The combination with GIS enabled the model to tackle the complex structures of road networks and avoid double counting. In the case study of Beijing, the following results are shown: 1) The total stocks for the entire road system reached 159 million tons, of which nearly 80% was stored in roads, and 20% in ancillary facilities. 2) Macadam was the largest stock (111 million tons), while stone mastic asphalt, polyurethane plastics, and atactic polypropylene accounted for smaller components of the overall system. 3) The stock per unit area of pedestrian overcrossing was higher than that of the other stock units in the entire system, and its steel stocks reached 0.49 t/m(2), which was 10 times as high as that in interchanges. 4) The high stock areas were mainly distributed in ring-shaped and radial expressways, as well as in major interchanges. 5) Expressways and arterials were excessively emphasized, while minor roads were relatively ignored. However, the variation of cross-sectional thickness in branches and neighborhood roads will have a significant impact on the scale of material stocks in the entire road system. © 2013.

Material Characterization and Geometric Segmentation of a Composite Structure Using Microfocus X-Ray Computed Tomography Image-Based Finite Element Modeling

NASA Technical Reports Server (NTRS)

Abdul-Aziz, Ali; Roth, D. J.; Cotton, R.; Studor, George F.; Christiansen, Eric; Young, P. C.

2011-01-01

This study utilizes microfocus x-ray computed tomography (CT) slice sets to model and characterize the damage locations and sizes in thermal protection system materials that underwent impact testing. ScanIP/FE software is used to visualize and process the slice sets, followed by mesh generation on the segmented volumetric rendering. Then, the local stress fields around several of the damaged regions are calculated for realistic mission profiles that subject the sample to extreme temperature and other severe environmental conditions. The resulting stress fields are used to quantify damage severity and make an assessment as to whether damage that did not penetrate to the base material can still result in catastrophic failure of the structure. It is expected that this study will demonstrate that finite element modeling based on an accurate three-dimensional rendered model from a series of CT slices is an essential tool to quantify the internal macroscopic defects and damage of a complex system made out of thermal protection material. Results obtained showing details of segmented images; three-dimensional volume-rendered models, finite element meshes generated, and the resulting thermomechanical stress state due to impact loading for the material are presented and discussed. Further, this study is conducted to exhibit certain high-caliber capabilities that the nondestructive evaluation (NDE) group at NASA Glenn Research Center can offer to assist in assessing the structural durability of such highly specialized materials so improvements in their performance and capacities to handle harsh operating conditions can be made.

An analytical and experimental investigation of flutter suppression via piezoelectric actuation

NASA Technical Reports Server (NTRS)

Heeg, Jennifer

1992-01-01

The objective of this research was to analytically and experimentally study the capabilities of adaptive material plate actuators for suppressing flutter. Piezoelectrics are materials which are characterized by their ability to produce voltage when subjected to a mechanical strain. The converse piezoelectric effect can be utilized to actuate a structure by applying a voltage. For this investigation, a two degree of freedom wind-tunnel model was designed, analyzed, and tested. The model consisted of a rigid wing and a flexible mount system which permitted translational and rotational degrees of freedom. Actuators, made of piezoelectric material were affixed to leaf springs on the mount system. Command signals, applied to the piezoelectric actuators, exerted control over the closed-loop damping and stiffness properties. A mathematical aeroservoelastic model was constructed using finite element and stiffness properties. A mathematical aeroservoelastic model was constructed using finite element methods, laminated plate theory, and aeroelastic analysis tools. A flutter suppression control law was designed, implemented on a digital control computer, and tested to conditions 20 percent above the passive flutter speed of the model. The experimental results represent the first time that adaptive materials have been used to actively suppress flutter. It demonstrates that small, carefully-placed actuating plates can be used effectively to control aeroelastic response.

Power Management and Distribution (PMAD) Model Development: Final Report

NASA Technical Reports Server (NTRS)

Metcalf, Kenneth J.

2011-01-01

Power management and distribution (PMAD) models were developed in the early 1990's to model candidate architectures for various Space Exploration Initiative (SEI) missions. They were used to generate "ballpark" component mass estimates to support conceptual PMAD system design studies. The initial set of models was provided to NASA Lewis Research Center (since renamed Glenn Research Center) in 1992. They were developed to estimate the characteristics of power conditioning components predicted to be available in the 2005 timeframe. Early 90's component and device designs and material technologies were projected forward to the 2005 timeframe, and algorithms reflecting those design and material improvements were incorporated into the models to generate mass, volume, and efficiency estimates for circa 2005 components. The models are about ten years old now and NASA GRC requested a review of them to determine if they should be updated to bring them into agreement with current performance projections or to incorporate unforeseen design or technology advances. This report documents the results of this review and the updated power conditioning models and new transmission line models generated to estimate post 2005 PMAD system masses and sizes. This effort continues the expansion and enhancement of a library of PMAD models developed to allow system designers to assess future power system architectures and distribution techniques quickly and consistently.

Terrestrial and marine perspectives on modeling organic matter degradation pathways.

PubMed

Burd, Adrian B; Frey, Serita; Cabre, Anna; Ito, Takamitsu; Levine, Naomi M; Lønborg, Christian; Long, Matthew; Mauritz, Marguerite; Thomas, R Quinn; Stephens, Brandon M; Vanwalleghem, Tom; Zeng, Ning

2016-01-01

Organic matter (OM) plays a major role in both terrestrial and oceanic biogeochemical cycles. The amount of carbon stored in these systems is far greater than that of carbon dioxide (CO2 ) in the atmosphere, and annual fluxes of CO2 from these pools to the atmosphere exceed those from fossil fuel combustion. Understanding the processes that determine the fate of detrital material is important for predicting the effects that climate change will have on feedbacks to the global carbon cycle. However, Earth System Models (ESMs) typically utilize very simple formulations of processes affecting the mineralization and storage of detrital OM. Recent changes in our view of the nature of this material and the factors controlling its transformation have yet to find their way into models. In this review, we highlight the current understanding of the role and cycling of detrital OM in terrestrial and marine systems and examine how this pool of material is represented in ESMs. We include a discussion of the different mineralization pathways available as organic matter moves from soils, through inland waters to coastal systems and ultimately into open ocean environments. We argue that there is strong commonality between aspects of OM transformation in both terrestrial and marine systems and that our respective scientific communities would benefit from closer collaboration. © 2015 John Wiley & Sons Ltd.

Structure and Optical Bandgap Relationship of π-Conjugated Systems

PubMed Central

Botelho, André Leitão; Shin, Yongwoo; Liu, Jiakai; Lin, Xi

2014-01-01

In bulk heterojunction photovoltaic systems both the open-circuit voltage as well as the short-circuit current, and hence the power conversion efficiency, are dependent on the optical bandgap of the electron-donor material. While first-principles methods are computationally intensive, simpler model Hamiltonian approaches typically suffer from one or more flaws: inability to optimize the geometries for their own input; absence of general, transferable parameters; and poor performance for non-planar systems. We introduce a set of new and revised parameters for the adapted Su-Schrieffer-Heeger (aSSH) Hamiltonian, which is capable of optimizing geometries, along with rules for applying them to any -conjugated system containing C, N, O, or S, including non-planar systems. The predicted optical bandgaps show excellent agreement to UV-vis spectroscopy data points from literature, with a coefficient of determination , a mean error of −0.05 eV, and a mean absolute deviation of 0.16 eV. We use the model to gain insights from PEDOT, fused thiophene polymers, poly-isothianaphthene, copolymers, and pentacene as sources of design rules in the search for low bandgap materials. Using the model as an in-silico design tool, a copolymer of benzodithiophenes along with a small-molecule derivative of pentacene are proposed as optimal donor materials for organic photovoltaics. PMID:24497944

An unstructured mathematical model for growth of Pleurotus ostreatus on lignocellulosic material in solid-state fermentation systems

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

Sarikaya, A.; Ladisch, M.R.

1997-01-01

Inedible plant material, generated in a Controlled Ecological Life Support System (CELSS), should be recycled preferably by bioregenerative methods that utilize enzymes or micro-organisms. This material consists of hemicellulose, cellulose, and lignin with the lignin fraction representing a recalcitrant component that is not readily treated by enzymatic methods. Consequently, the white-rot fungus, Pleurotus ostreatus, is attractive since it effectively degrades lignin and produces edible mushrooms. This work describes an unstructured model for the growth of P. ostreatus in a solid-state fermentation system using lignocellulosic plant materials from Brassica napus (rapeseed) as a substrate at three different particle sizes. A logisticmore » function model based on area was found to fit the surface growth of the mycelium on the solid substrate with respect to time, whereas a model based on diameter, alone, did not fit the data as well. The difference between the two measures of growth was also evident for mycelial growth in a bioreactor designed to facilitate a slow flowrate of air through the 1.5 cm thick mat of lignocellulosic biomass particles. The result is consistent with the concept of competition of the mycelium for the substrate that surrounds it, rather than just substrate that is immediately available to single cells. This approach provides a quantitative measure of P. ostreatus growth on lignocellulosic biomass in a solid-state fermentation system. The experimental data show that the best growth is obtained for the largest particles (1 cm) of the lignocellulosic substrate. 13 refs., 6 figs., 2 tabs.« less

Transport and degradation of metalaxyl and isoproturon in biopurification columns inoculated with pesticide-primed material.

PubMed

De Wilde, Tineke; Spanoghe, Pieter; Sniegowksi, Kristel; Ryckeboer, Jaak; Jaeken, Peter; Springael, Dirk

2010-01-01

Laboratory column displacement experiments were performed to examine whether addition of pesticide-primed material to the matrix of an on-farm biopurification system (BPS), intended to remove pesticides from agricultural waste water, positively affects the degradation of mobile pesticides in the system. Percolated column microcosms with varying types and amounts of metalaxyl and/or isoproturon-primed material or non-primed material were irrigated with water artificially contaminated with isoproturon and/or metalaxyl. Transport of isoproturon was well described using the convection dispersion equation and no dissipation was observed, even in columns inoculated with isoproturon-primed material. On the other hand, delayed dissipation of metalaxyl, i.e., after an initial lag phase, was encountered in all columns receiving metalaxyl. In all systems, dissipation could be described using the Monod model indicating that a metalaxyl degrading population grew in the systems. There was a clear correlation between the lag phase and the amount of metalaxyl-primed material added to the system, i.e., increasing amounts of added material resulted into shorter lag phases and hence more rapid initiation of growth-associated metalaxyl degradation in the system. Our observations suggest that indeed pesticide-primed material can reduce the start-up phase of degradation of mobile pesticides in a BPS and as such can increase its efficiency. However, the primed material should be chosen carefully and preferentially beforehand tested for its capacity to degrade the pesticide.

Transient aero-thermal mapping of passive Thermal Protection system for nose-cap of Reusable Hypersonic Vehicle

NASA Astrophysics Data System (ADS)

Mahulikar, Shripad P.; Khurana, Shashank; Dungarwal, Ritesh; Shevakari, Sushil G.; Subramanian, Jayakumar; Gujarathi, Amit V.

2008-12-01

The temperature field history of passive Thermal Protection System (TPS) material at the nose-cap (forward stagnation region) of a Reusable Hypersonic Vehicle (RHV) is generated. The 3-D unsteady heat transfer model couples conduction in the solid with external convection and radiation that are modeled as time-varying boundary conditions on the surface. Results are presented for the following two cases: (1) nose-cap comprised of ablative TPS material only (SIRCA/PICA), and (2) nose-cap comprised of a combination of ablative TPS material with moderate thermal conductivity and insulative TPS material. Comparison of the temperature fields of SIRCA and PICA [Case (1)] indicates lowering of the peak stagnation region temperatures for PICA, due to its higher thermal conductivity. Also, the use of PICA and insulative TPS [Case (2)] for the nose-cap has higher potential for weight reduction than the use of ablative TPS alone.

An integrated production-inventory model for food products adopting a general raw material procurement policy

NASA Astrophysics Data System (ADS)

Fauza, G.; Prasetyo, H.; Amanto, B. S.

2018-05-01

Studies on an integrated production-inventory model for deteriorating items have been done extensively. Most of the studies define deterioration as physical depletion of some inventories over time. This definition may not represent the deterioration characteristics of food products. The quality of food production decreases over time while the quantity remains the same. Further, in the existing models, the raw material is replenished several times (or at least once) within one production cycle. In food industries, however, a food company, for several reasons (e.g., the seasonal raw materials, discounted price, etc.) sometimes will get more benefit if it orders raw materials in a large quantity. Considering this fact, this research, therefore, is aimed at developing a more representative inventory model by (i) considering the quality losses in food and (ii) adopting a general raw material procurement policy. A mathematical model is established to represent the proposed policy in which the total profit of the system is the objective function. To evaluate the performance of the model, a numerical test was conducted. The numerical test indicates that the developed model has better performance, i.e., the total profit is 2.3% higher compared to the existing model.

A two-stage optimization model for emergency material reserve layout planning under uncertainty in response to environmental accidents.

PubMed

Liu, Jie; Guo, Liang; Jiang, Jiping; Jiang, Dexun; Liu, Rentao; Wang, Peng

2016-06-05

In the emergency management relevant to pollution accidents, efficiency emergency rescues can be deeply influenced by a reasonable assignment of the available emergency materials to the related risk sources. In this study, a two-stage optimization framework is developed for emergency material reserve layout planning under uncertainty to identify material warehouse locations and emergency material reserve schemes in pre-accident phase coping with potential environmental accidents. This framework is based on an integration of Hierarchical clustering analysis - improved center of gravity (HCA-ICG) model and material warehouse location - emergency material allocation (MWL-EMA) model. First, decision alternatives are generated using HCA-ICG to identify newly-built emergency material warehouses for risk sources which cannot be satisfied by existing ones with a time-effective manner. Second, emergency material reserve planning is obtained using MWL-EMA to make emergency materials be prepared in advance with a cost-effective manner. The optimization framework is then applied to emergency management system planning in Jiangsu province, China. The results demonstrate that the developed framework not only could facilitate material warehouse selection but also effectively provide emergency material for emergency operations in a quick response. Copyright © 2016. Published by Elsevier B.V.

Quantitative non-destructive testing

NASA Technical Reports Server (NTRS)

Welch, C. S.

1985-01-01

The work undertaken during this period included two primary efforts. The first is a continuation of theoretical development from the previous year of models and data analyses for NDE using the Optical Thermal Infra-Red Measurement System (OPTITHIRMS) system, which involves heat injection with a laser and observation of the resulting thermal pattern with an infrared imaging system. The second is an investigation into the use of the thermoelastic effect as an effective tool for NDE. As in the past, the effort is aimed towards NDE techniques applicable to composite materials in structural applications. The theoretical development described produced several models of temperature patterns over several geometries and material types. Agreement between model data and temperature observations was obtained. A model study with one of these models investigated some fundamental difficulties with the proposed method (the primitive equation method) for obtaining diffusivity values in plates of thickness and supplied guidelines for avoiding these difficulties. A wide range of computing speeds was found among the various models, with a one-dimensional model based on Laplace's integral solution being both very fast and very accurate.

System analysis with improved thermo-mechanical fuel rod models for modeling current and advanced LWR materials in accident scenarios

NASA Astrophysics Data System (ADS)

Porter, Ian Edward

A nuclear reactor systems code has the ability to model the system response in an accident scenario based on known initial conditions at the onset of the transient. However, there has been a tendency for these codes to lack the detailed thermo-mechanical fuel rod response models needed for accurate prediction of fuel rod failure. This proposed work will couple today's most widely used steady-state (FRAPCON) and transient (FRAPTRAN) fuel rod models with a systems code TRACE for best-estimate modeling of system response in accident scenarios such as a loss of coolant accident (LOCA). In doing so, code modifications will be made to model gamma heating in LWRs during steady-state and accident conditions and to improve fuel rod thermal/mechanical analysis by allowing axial nodalization of burnup-dependent phenomena such as swelling, cladding creep and oxidation. With the ability to model both burnup-dependent parameters and transient fuel rod response, a fuel dispersal study will be conducted using a hypothetical accident scenario under both PWR and BWR conditions to determine the amount of fuel dispersed under varying conditions. Due to the fuel fragmentation size and internal rod pressure both being dependent on burnup, this analysis will be conducted at beginning, middle and end of cycle to examine the effects that cycle time can play on fuel rod failure and dispersal. Current fuel rod and system codes used by the Nuclear Regulatory Commission (NRC) are compilations of legacy codes with only commonly used light water reactor materials, Uranium Dioxide (UO2), Mixed Oxide (U/PuO 2) and zirconium alloys. However, the events at Fukushima Daiichi and Three Mile Island accident have shown the need for exploration into advanced materials possessing improved accident tolerance. This work looks to further modify the NRC codes to include silicon carbide (SiC), an advanced cladding material proposed by current DOE funded research on accident tolerant fuels (ATF). Several additional fuels will also be analyzed, including uranium nitride (UN), uranium carbide (UC) and uranium silicide (U3Si2). Focusing on the system response in an accident scenario, an emphasis is placed on the fracture mechanics of the ceramic cladding by design the fuel rods to eliminate pellet cladding mechanical interaction (PCMI). The time to failure and how much of the fuel in the reactor fails with an advanced fuel design will be analyzed and compared to the current UO2/Zircaloy design using a full scale reactor model.

Impact Compaction of a Granular Material

NASA Astrophysics Data System (ADS)

Fenton, Gregg; Asay, Blaine; Todd, Steve; Grady, Dennis

2017-06-01

The dynamic behavior of granular materials has importance to a variety of engineering applications. Although, the mechanical behavior of granular materials have been studied extensively for several decades, the dynamic behavior of these materials remains poorly understood. High-quality experimental data are needed to improve our general understanding of granular material compaction physics. This paper describes how an instrumented plunger impact system can be used to measure the compaction process for granular materials at high and controlled strain rates and subsequently used for computational modelling. The experimental technique relies on a gas-gun driven plunger system to generate a compaction wave through a volume of granular material. This volume of material has been redundantly instrumented along the bed length to track the progression of the compaction wave, and the piston displacement is measured with Photon Doppler Velocimetry (PDV). Using the gathered experimental data along with the initial material tap density, a granular material equation of state can be determined.

Damage, Self-Healing, and Hysteresis in Spider Silks

PubMed Central

De Tommasi, D.; Puglisi, G.; Saccomandi, G.

2010-01-01

Abstract In this article, we propose a microstructure-based continuum model to describe the material behavior of spider silks. We suppose that the material is composed of a soft fraction with entropic elasticity and a hard, damageable fraction. The hard fraction models the presence of stiffer, crystal-rich, oriented regions and accounts for the effect of softening induced by the breaking of hydrogen bonds. To describe the observed presence of crystals with different size, composition, and orientation, this hard fraction is modeled as a distribution of materials with variable properties. The soft fraction describes the remaining regions of amorphous material and is here modeled as a wormlike chain. During stretching, we consider the effect of bond-breaking as a transition from the hard- to the soft-material phase. As we demonstrate, a crucial effect of bond-breaking that accompanies the softening of the material is an increase in contour length associated with chains unraveling. The model describes also the self-healing properties of the material by assuming partial bond reconnection upon unloading. Despite its simplicity, the proposed mechanical system reproduces the main experimental effects observed in cyclic loading of spider silks. Moreover, our approach is amenable to two- or three-dimensional extensions and may prove to be a useful tool in the field of microstructure optimization for bioinspired materials. PMID:20441758

Adaptive and active materials: selected papers from the ASME 2012 Conference on Smart Materials, Adaptive Structures and Intelligent Systems (SMASIS 12) (Stone Mountain, GA, USA, 19-21 September 2012)

NASA Astrophysics Data System (ADS)

Seelecke, Stefan; Erturk, Alper; Ounaies, Zoubeida; Naguib, Hani; Huber, John; Turner, Travis; Anderson, Iain; Philen, Michael; Baba Sundaresan, Vishnu

2013-09-01

The fifth annual meeting of the ASME/AIAA Smart Materials, Adaptive Structures and Intelligent Systems Conference (SMASIS) was held in beautiful Stone Mountain near Atlanta, GA. It is the conference's objective to provide an up-to-date overview of research trends in the entire field of smart materials systems. This was reflected in keynote speeches by Professor Eduard Arzt (Institute of New Materials and Saarland University, Saarbrücken, Germany) on 'Micro-patterned artificial 'Gecko' surfaces: a path to switchable adhesive function', by Professor Ray H Baughman (The Alan G MacDiarmid NanoTech Institute, University of Texas at Dallas) on 'The diverse and growing family of carbon nanotube and related artificial muscles', and by Professor Richard James (University of Minnesota) on 'The direct conversion of heat to electricity using multiferroic materials with phase transformations'. SMASIS 2012 was divided into eight symposia which span basic research, applied technological design and development, and industrial and governmental integrated system and application demonstrations. • SYMP 1. Development and characterization of multifunctional materials. • SYMP 2. Mechanics and behavior of active materials. • SYMP 3. Modeling, simulation and control of adaptive systems. • SYMP 4. Integrated system design and implementation. • SYMP 5. Structural health monitoring/NDE. • SYMP 6. Bio-inspired materials and systems. • SYMP 7. Energy harvesting. • SYMP 8. Structural and materials logic. This year we were particularly excited to introduce a new symposium on energy harvesting, which has quickly matured from a special track in previous years to an independent symposium for the first time. The subject cuts across fields by studying different materials, ranging from piezoelectrics to electroactive polymers, as well as by emphasizing different energy sources from wind to waves and ambient vibrations. Modeling, experimental studies, and technology applications all belong to the symposium topics. In addition, the conference also featured a special symposium dedicated to DARPA's structural and materials/logic program. The program seeks to enable structural systems to adapt to varying loads and simultaneously exhibit both high stiffness and high damping. Authors of selected papers in the materials areas (symposia 1, 2, and 6) as well as energy harvesting (symposium 7) were invited to write a full journal article on their presentation topic for publication in this special issue of Smart Materials and Structures . This collection of papers demonstrates the exceptional quality and originality of the conference presentations. We are very appreciative of their efforts to produce this collection of highly relevant articles on smart materials.

Comparison of Numerical Analyses with a Static Load Test of a Continuous Flight Auger Pile

NASA Astrophysics Data System (ADS)

Hoľko, Michal; Stacho, Jakub

2014-12-01

The article deals with numerical analyses of a Continuous Flight Auger (CFA) pile. The analyses include a comparison of calculated and measured load-settlement curves as well as a comparison of the load distribution over a pile's length. The numerical analyses were executed using two types of software, i.e., Ansys and Plaxis, which are based on FEM calculations. Both types of software are different from each other in the way they create numerical models, model the interface between the pile and soil, and use constitutive material models. The analyses have been prepared in the form of a parametric study, where the method of modelling the interface and the material models of the soil are compared and analysed. Our analyses show that both types of software permit the modelling of pile foundations. The Plaxis software uses advanced material models as well as the modelling of the impact of groundwater or overconsolidation. The load-settlement curve calculated using Plaxis is equal to the results of a static load test with a more than 95 % degree of accuracy. In comparison, the load-settlement curve calculated using Ansys allows for the obtaining of only an approximate estimate, but the software allows for the common modelling of large structure systems together with a foundation system.

Integrated material state awareness system with self-learning symbiotic diagnostic algorithms and models

NASA Astrophysics Data System (ADS)

Banerjee, Sourav; Liu, Lie; Liu, S. T.; Yuan, Fuh-Gwo; Beard, Shawn

2011-04-01

Materials State Awareness (MSA) goes beyond traditional NDE and SHM in its challenge to characterize the current state of material damage before the onset of macro-damage such as cracks. A highly reliable, minimally invasive system for MSA of Aerospace Structures, Naval structures as well as next generation space systems is critically needed. Development of such a system will require a reliable SHM system that can detect the onset of damage well before the flaw grows to a critical size. Therefore, it is important to develop an integrated SHM system that not only detects macroscale damages in the structures but also provides an early indication of flaw precursors and microdamages. The early warning for flaw precursors and their evolution provided by an SHM system can then be used to define remedial strategies before the structural damage leads to failure, and significantly improve the safety and reliability of the structures. Thus, in this article a preliminary concept of developing the Hybrid Distributed Sensor Network Integrated with Self-learning Symbiotic Diagnostic Algorithms and Models to accurately and reliably detect the precursors to damages that occur to the structure are discussed. Experiments conducted in a laboratory environment shows potential of the proposed technique.

Construction of mathematical model for measuring material concentration by colorimetric method

NASA Astrophysics Data System (ADS)

Liu, Bing; Gao, Lingceng; Yu, Kairong; Tan, Xianghua

2018-06-01

This paper use the method of multiple linear regression to discuss the data of C problem of mathematical modeling in 2017. First, we have established a regression model for the concentration of 5 substances. But only the regression model of the substance concentration of urea in milk can pass through the significance test. The regression model established by the second sets of data can pass the significance test. But this model exists serious multicollinearity. We have improved the model by principal component analysis. The improved model is used to control the system so that it is possible to measure the concentration of material by direct colorimetric method.

Design and implementation of a system for laser assisted milling of advanced materials

NASA Astrophysics Data System (ADS)

Wu, Xuefeng; Feng, Gaocheng; Liu, Xianli

2016-09-01

Laser assisted machining is an effective method to machine advanced materials with the added benefits of longer tool life and increased material removal rates. While extensive studies have investigated the machining properties for laser assisted milling(LAML), few attempts have been made to extend LAML to machining parts with complex geometric features. A methodology for continuous path machining for LAML is developed by integration of a rotary and movable table into an ordinary milling machine with a laser beam system. The machining strategy and processing path are investigated to determine alignment of the machining path with the laser spot. In order to keep the material removal temperatures above the softening temperature of silicon nitride, the transformation is coordinated and the temperature interpolated, establishing a transient thermal model. The temperatures of the laser center and cutting zone are also carefully controlled to achieve optimal machining results and avoid thermal damage. These experiments indicate that the system results in no surface damage as well as good surface roughness, validating the application of this machining strategy and thermal model in the development of a new LAML system for continuous path processing of silicon nitride. The proposed approach can be easily applied in LAML system to achieve continuous processing and improve efficiency in laser assisted machining.

Molecular plasmonics: The role of rovibrational molecular states in exciton-plasmon materials under strong-coupling conditions

NASA Astrophysics Data System (ADS)

Sukharev, Maxim; Charron, Eric

2017-03-01

We extend the model of exciton-plasmon materials to include a rovibrational structure of molecules using wave-packet propagations on electronic potential energy surfaces. Our model replaces conventional two-level emitters with more complex molecules, allowing us to examine the influence of alignment and vibrational dynamics on strong coupling with surface plasmon-polaritons. We apply the model to a hybrid system comprising a thin layer of molecules placed on top of a periodic array of slits. Rigorous simulations are performed for two types of molecular systems described by vibrational bound-bound and bound-continuum electronic transitions. Calculations reveal new features in transmission, reflection, and absorption spectra, including the observation of significantly higher values of the Rabi splitting and vibrational patterns clearly seen in the corresponding spectra. We also examine the influence of anisotropic initial conditions on optical properties of hybrid materials, demonstrating that the optical response of the system is significantly affected by an initial prealignment of the molecules. Our work demonstrates that prealigned molecules could serve as an efficient probe for the subdiffraction characterization of the near-field near metal interfaces.

Design study of advanced model support systems for the National Transonic Facility (NTF)

NASA Technical Reports Server (NTRS)

1987-01-01

It has long been recognized that the sting (or support system) is a very critical part of the model system. The designer is frequently faced with the tradeoff of minimizing sting size, thereby compromising facility and model safety, against a larger sting and the subsequent problems of sting interference effects. In the NASA Langley Research Center National Transonic Facility (NTF), this problem is accentuated by the severe environment of high pressure/low temperature, designed into the facility to provide the desired high Reynolds number. Compromises in the configuration geometry and/or limiting the test envelope are therefore contrary to the purposes and goals of the NTF and are unacceptable. The results of an investigation aimed at improvements of 25% in both strength and Young's modulus of elasticity as compared to high strength cryogenically acceptable steels currently being used are presented. Various materials or combinations of materials were studied along with different design approaches. Design concepts were developed which included conventional material stings, advanced composites, and hybrid configurations. Candidate configurations are recommended.

Incorporating physically-based microstructures in materials modeling: Bridging phase field and crystal plasticity frameworks

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

Lim, Hojun; Abdeljawad, Fadi; Owen, Steven J.

Here, the mechanical properties of materials systems are highly influenced by various features at the microstructural level. The ability to capture these heterogeneities and incorporate them into continuum-scale frameworks of the deformation behavior is considered a key step in the development of complex non-local models of failure. In this study, we present a modeling framework that incorporates physically-based realizations of polycrystalline aggregates from a phase field (PF) model into a crystal plasticity finite element (CP-FE) framework. Simulated annealing via the PF model yields ensembles of materials microstructures with various grain sizes and shapes. With the aid of a novel FEmore » meshing technique, FE discretizations of these microstructures are generated, where several key features, such as conformity to interfaces, and triple junction angles, are preserved. The discretizations are then used in the CP-FE framework to simulate the mechanical response of polycrystalline α-iron. It is shown that the conformal discretization across interfaces reduces artificial stress localization commonly observed in non-conformal FE discretizations. The work presented herein is a first step towards incorporating physically-based microstructures in lieu of the overly simplified representations that are commonly used. In broader terms, the proposed framework provides future avenues to explore bridging models of materials processes, e.g. additive manufacturing and microstructure evolution of multi-phase multi-component systems, into continuum-scale frameworks of the mechanical properties.« less

Incorporating physically-based microstructures in materials modeling: Bridging phase field and crystal plasticity frameworks

DOE PAGES

Lim, Hojun; Abdeljawad, Fadi; Owen, Steven J.; ...

2016-04-25

Here, the mechanical properties of materials systems are highly influenced by various features at the microstructural level. The ability to capture these heterogeneities and incorporate them into continuum-scale frameworks of the deformation behavior is considered a key step in the development of complex non-local models of failure. In this study, we present a modeling framework that incorporates physically-based realizations of polycrystalline aggregates from a phase field (PF) model into a crystal plasticity finite element (CP-FE) framework. Simulated annealing via the PF model yields ensembles of materials microstructures with various grain sizes and shapes. With the aid of a novel FEmore » meshing technique, FE discretizations of these microstructures are generated, where several key features, such as conformity to interfaces, and triple junction angles, are preserved. The discretizations are then used in the CP-FE framework to simulate the mechanical response of polycrystalline α-iron. It is shown that the conformal discretization across interfaces reduces artificial stress localization commonly observed in non-conformal FE discretizations. The work presented herein is a first step towards incorporating physically-based microstructures in lieu of the overly simplified representations that are commonly used. In broader terms, the proposed framework provides future avenues to explore bridging models of materials processes, e.g. additive manufacturing and microstructure evolution of multi-phase multi-component systems, into continuum-scale frameworks of the mechanical properties.« less

Characterization of Viscoelastic Materials Using Group Shear Wave Speeds.

PubMed

Rouze, Ned C; Deng, Yufeng; Trutna, Courtney A; Palmeri, Mark L; Nightingale, Kathryn R

2018-05-01

Recent investigations of viscoelastic properties of materials have been performed by observing shear wave propagation following localized, impulsive excitations, and Fourier decomposing the shear wave signal to parameterize the frequency-dependent phase velocity using a material model. This paper describes a new method to characterize viscoelastic materials using group shear wave speeds , , and determined from the shear wave displacement, velocity, and acceleration signals, respectively. Materials are modeled using a two-parameter linear attenuation model with phase velocity and dispersion slope at a reference frequency of 200 Hz. Analytically calculated lookup tables are used to determine the two material parameters from pairs of measured group shear wave speeds. Green's function calculations are used to validate the analytic model. Results are reported for measurements in viscoelastic and approximately elastic phantoms and demonstrate good agreement with phase velocities measured using Fourier analysis of the measured shear wave signals. The calculated lookup tables are relatively insensitive to the excitation configuration. While many commercial shear wave elasticity imaging systems report group shear wave speeds as the measures of material stiffness, this paper demonstrates that differences , , and of group speeds are first-order measures of the viscous properties of materials.

Damage-mitigating control of aerospace systems for high performance and extended life

NASA Technical Reports Server (NTRS)

Ray, Asok; Wu, Min-Kuang; Carpino, Marc; Lorenzo, Carl F.; Merrill, Walter C.

1992-01-01

The concept of damage-mitigating control is to minimize fatigue (as well as creep and corrosion) damage of critical components of mechanical structures while simultaneously maximizing the system dynamic performance. Given a dynamic model of the plant and the specifications for performance and stability robustness, the task is to synthesize a control law that would meet the system requirements and, at the same time, satisfy the constraints that are imposed by the material and structural properties of the critical components. The authors present the concept of damage-mitigating control systems design with the following objectives: (1) to achieve high performance with a prolonged life span; and (2) to systematically update the controller as the new technology of advanced materials evolves. The major challenge is to extract the information from the material properties and then utilize this information in a mathematical form so that it can be directly applied to robust control synthesis for mechanical systems. The basic concept of damage-mitigating control is illustrated using a relatively simplified model of a space shuttle main engine.

Development and Application of New Solid-State Models for Low-Energy Vibrations, Lattice Defects, Entropies of Mixing, and Magnetic Properties

NASA Astrophysics Data System (ADS)

Schliesser, Jacob M.

Low-temperature heat capacity data contain information on the physical properties of materials, and new models continue to be developed to aid in the analysis and interpretation of heat capacity data into physically meaningful properties. This work presents the development of two such models and their application to real material systems. Equations describing low-energy vibrational modes with a gap in the density of states (DOS) have been derived and tested on several material systems with known gaps in the DOS, and the origins of such gaps in the DOS are presented. Lattice vacancies have been shown to produce a two-level system that can be modeled with a sum of low-energy Schottky anomalies that produce an overall linear dependence on temperature in the low-temperature heat capacity data. These two models for gaps in the vibrational DOS and the relationship between a linear heat capacity and lattice vacancies and many well-known models have been applied to several systems of materials to test their validity and applicability as well as provide greater information on the systems themselves. A series of bulk and nanoscale Mn-Fe and Co-Fe spinel solid solutions were analyzed using the entropies derived from heat capacity data, and excess entropies of mixing were determined. These entropies show that changes in valence, cation distribution, bonding, and the microstructure between the mixing ions is non-ideal, especially in the nanoparticles. The heat capacity data of ten Al doped TiO2 anatase nanoparticle samples have also been analyzed to show that the Al3+ dopant ions form small regions of short-range order, similar to a glass, within the TiO2 particles, while the overall structure of TiO2 remains unchanged. This has been supported by X-ray diffraction (XRD) and electron energy-loss spectroscopy and provides new insights to the synthesis and characterization of doped materials. The final investigation examines nanocrystalline CuO using heat capacities, magnetization, XRD, and electron microscopy and compares the findings to the known properties of bulk CuO. All of these measurements show transitions between antiferromagnetic and paramagnetic states in the temperature range of about 150--350 K that are greater in number and higher in temperature than the transitions in bulk CuO. These changes are shown to cause an increase in the temperature range of multiferroicity in CuO nanoparticles. Keywords: thermodynamics, heat capacity, lattice vacancies, materials, nanoparticles, mixing, characterization.

The Material Point Method and Simulation of Wave Propagation in Heterogeneous Media

NASA Astrophysics Data System (ADS)

Bardenhagen, S. G.; Greening, D. R.; Roessig, K. M.

2004-07-01

The mechanical response of polycrystalline materials, particularly under shock loading, is of significant interest in a variety of munitions and industrial applications. Homogeneous continuum models have been developed to describe material response, including Equation of State, strength, and reactive burn models. These models provide good estimates of bulk material response. However, there is little connection to underlying physics and, consequently, they cannot be applied far from their calibrated regime with confidence. Both explosives and metals have important structure at the (energetic or single crystal) grain scale. The anisotropic properties of the individual grains and the presence of interfaces result in the localization of energy during deformation. In explosives energy localization can lead to initiation under weak shock loading, and in metals to material ejecta under strong shock loading. To develop accurate, quantitative and predictive models it is imperative to develop a sound physical understanding of the grain-scale material response. Numerical simulations are performed to gain insight into grain-scale material response. The Generalized Interpolation Material Point Method family of numerical algorithms, selected for their robust treatment of large deformation problems and convenient framework for implementing material interface models, are reviewed. A three-dimensional simulation of wave propagation through a granular material indicates the scale and complexity of a representative grain-scale computation. Verification and validation calculations on model bimaterial systems indicate the minimum numerical algorithm complexity required for accurate simulation of wave propagation across material interfaces and demonstrate the importance of interfacial decohesion. Preliminary results are presented which predict energy localization at the grain boundary in a metallic bicrystal.

Rock Cutting Depth Model Based on Kinetic Energy of Abrasive Waterjet

NASA Astrophysics Data System (ADS)

Oh, Tae-Min; Cho, Gye-Chun

2016-03-01

Abrasive waterjets are widely used in the fields of civil and mechanical engineering for cutting a great variety of hard materials including rocks, metals, and other materials. Cutting depth is an important index to estimate operating time and cost, but it is very difficult to predict because there are a number of influential variables (e.g., energy, geometry, material, and nozzle system parameters). In this study, the cutting depth is correlated to the maximum kinetic energy expressed in terms of energy (i.e., water pressure, water flow rate, abrasive feed rate, and traverse speed), geometry (i.e., standoff distance), material (i.e., α and β), and nozzle system parameters (i.e., nozzle size, shape, and jet diffusion level). The maximum kinetic energy cutting depth model is verified with experimental test data that are obtained using one type of hard granite specimen for various parameters. The results show a unique curve for a specific rock type in a power function between cutting depth and maximum kinetic energy. The cutting depth model developed here can be very useful for estimating the process time when cutting rock using an abrasive waterjet.

Aeroelastic flutter enhancement by exploiting the combined use of shape memory alloys and nonlinear piezoelectric circuits

NASA Astrophysics Data System (ADS)

Sousa, Vagner Candido de; Silva, Tarcísio Marinelli Pereira; De Marqui Junior, Carlos

2017-10-01

In this paper, the combined effects of semi-passive control using shunted piezoelectric material and passive pseudoelastic hysteresis of shape memory springs on the aerolastic behavior of a typical section is investigated. An aeroelastic model that accounts for the presence of both smart materials employed as mechanical energy dissipation devices is presented. The Brinson model is used to simulate the shape memory material. New expressions for the modeling of the synchronized switch damping on inductor technique (developed for enhanced piezoelectric damping) are presented, resulting in better agreement with experimental data. The individual effects of each nonlinear mechanism on the aeroelastic behavior of the typical section are first verified. Later, the combined effects of semi-passive piezoelectric control and passive shape memory alloy springs on the post-critical behavior of the system are discussed in details. The range of post-flutter airflow speeds with stable limit cycle oscillations is significantly increased due to the combined effects of both sources of energy dissipation, providing an effective and autonomous way to modify the behavior of aeroelastic systems using smart materials.

An analytical and experimental study to investigate flutter suppression via piezoelectric actuation. M.S. Thesis - George Washington Univ., 1991

NASA Technical Reports Server (NTRS)

Heeg, Jennifer

1991-01-01

The objective was to analytically and experimentally study the capabilities of adaptive material plate actuators for suppressing flutter. The validity of analytical modeling techniques for piezoelectric materials was also investigated. Piezoelectrics are materials which are characterized by their ability to produce voltage when subjected to a mechanical strain. The converse piezoelectric effect can be utilized to actuate a structure by applying a voltage. For this investigation, a two degree of freedom wind tunnel model was designed, analyzed, and tested. The model consisted of a rigid airfoil and a flexible mount system which permitted a translational and a rotational degree of freedom. It was designed such that flutter was encounted within the testing envelope of the wind tunnel. Actuators, made of piezoelectric material were affixed to leaf springs of the mount system. Each degree of freedom was controlled by a separate leaf spring. Command signals, applied to the piezoelectric actuators, exerted control over the damping and stiffness properties. A mathematical aeroservoelastic model was constructed using finite element methods, laminated plate theory, and aeroelastic analysis tools. Plant characteristics were determined from this model and verified by open loop experimental tests. A flutter suppression control law was designed and implemented on a digital control computer. Closed loop flutter testing was conducted. The experimental results represent the first time that adaptive materials have been used to actively suppress flutter. It demonstrates that small, carefully placed actuating plates can be used effectively to control aeroelastic response.

2012 Community Earth System Model (CESM) Tutorial - Proposal to DOE

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

Holland, Marika; Bailey, David A

2013-03-18

The Community Earth System Model (CESM) is a fully-coupled, global climate model that provides state-of-the-art computer simulations of the Earth's past, present, and future climate states. This document provides the agenda and list of participants for the conference. Web materials for all lectures and practical sessions available from: http://www.cesm.ucar.edu/events/tutorials/073012/ .

Single High Fidelity Geometric Data Sets for LCM - Model Requirements

DTIC Science & Technology

2006-11-01

are extensive single 3D CAD data models incorporating hull structure, propulsion, steering, piping , electrical, HVAC and other systems, which make...single 3D CAD data models incorporating hull structure, propulsion, steering, piping , electrical, HVAC and other systems. During this same period...be sufficiently flexible to accommodate the diverse requirements of various types of structural analyses. Section Properties & Material Data

Experimental and Analytical Seismic Studies of a Four-Span Bridge System with Innovative Materials

NASA Astrophysics Data System (ADS)

Cruz Noguez, Carlos Alonso

As part of a multi-university project utilizing the NSF Network for Earthquake Engineering Simulation (NEES), a quarter-scale model of a four-span bridge incorporating plastic hinges with different advanced materials was tested to failure on the three shake table system at the University of Nevada, Reno (UNR). The bridge was the second test model in a series of three 4-span bridges, with the first model being a conventional reinforced-concrete (RC) structure. The purpose of incorporating advanced materials was to improve the seismic performance of the bridge with respect to two damage indicators: (1) column damage and (2) permanent deformations. The goals of the study presented in this document were to (1) evaluate the seismic performance of a 4-span bridge system incorporating SMA/ECC and built-in rubber pad plastic hinges as well as post-tensioned piers, (2) quantify the relative merit of these advanced materials and details compared to each other and to conventional reinforced concrete plastic hinges, (3) determine the influence of abutment-superstructure interaction on the response, (4) examine the ability of available elaborate analytical modeling techniques to model the performance of advanced materials and details, and (5) conduct an extensive parametric study of different variations of the bridge model to study several important issues in bridge earthquake engineering. The bridge model included six columns, each pair of which utilized a different advanced detail at bottom plastic hinges: shape memory alloys (SMA), special engineered cementitious composites (ECC), elastomeric pads embedded into columns, and post-tensioning tendons. The design of the columns, location of the bents, and selection of the loading protocol were based on pre-test analyses conducted using computer program OpenSees. The bridge model was subjected to two-horizontal components of simulated earthquake records of the 1994 Northridge earthquake. Over 340 channels of data were collected. The test results showed the effectiveness of the advanced materials in reducing damage and permanent displacements. The damage was minimal in plastic hinges with SMA/ECC and those with built-in elastomeric pads. Conventional RC plastic hinges were severely damaged due to spalling of concrete and rupture of the longitudinal and transverse reinforcement. Extensive post-test analytical studies were conducted and it was determined that a computational model of the bridge that included bridge-abutment interaction using OpenSees was able to provide satisfactory estimations of key structural parameters such as superstructure displacements and base shears. The analytical model was also used to conduct parametric studies on single-column and bridge-system response under near-fault ground motions. The effects of vertical excitations and transverse shear-keys at the bridge abutments on the superstructure displacement and column drifts were also explored.

Model and system learners, optimal process constructors and kinetic theory-based goal-oriented design: A new paradigm in materials and processes informatics

NASA Astrophysics Data System (ADS)

Abisset-Chavanne, Emmanuelle; Duval, Jean Louis; Cueto, Elias; Chinesta, Francisco

2018-05-01

Traditionally, Simulation-Based Engineering Sciences (SBES) has relied on the use of static data inputs (model parameters, initial or boundary conditions, … obtained from adequate experiments) to perform simulations. A new paradigm in the field of Applied Sciences and Engineering has emerged in the last decade. Dynamic Data-Driven Application Systems [9, 10, 11, 12, 22] allow the linkage of simulation tools with measurement devices for real-time control of simulations and applications, entailing the ability to dynamically incorporate additional data into an executing application, and in reverse, the ability of an application to dynamically steer the measurement process. It is in that context that traditional "digital-twins" are giving raise to a new generation of goal-oriented data-driven application systems, also known as "hybrid-twins", embracing models based on physics and models exclusively based on data adequately collected and assimilated for filling the gap between usual model predictions and measurements. Within this framework new methodologies based on model learners, machine learning and kinetic goal-oriented design are defining a new paradigm in materials, processes and systems engineering.

Modeling the Capillary Pressure for the Migration of the Liquid Phase in Granular Solid-Liquid-Vapor Systems: Application to the Control of the Composition Profile in W-Cu FGM Materials

NASA Astrophysics Data System (ADS)

Missiaen, Jean-Michel; Raharijaona, Jean-Joël; Delannay, Francis

2016-11-01

A model is developed to compute the capillary pressure for the migration of the liquid phase out or into a uniform solid-liquid-vapor system. The capillary pressure is defined as the reduction of the overall interface energy per volume increment of the transferred fluid phase. The model takes into account the particle size of the solid particle aggregate, the packing configuration (coordination number, porosity), the volume fractions of the different phases, and the values of the interface energies in the system. The model is used for analyzing the stability of the composition profile during processing of W-Cu functionally graded materials combining a composition gradient with a particle size gradient. The migration pressure is computed with the model in two stages: (1) just after the melting of copper, i.e., when sintering and shape accommodation of the W particle aggregate can still be neglected and (2) at high temperature, when the system is close to full density with equilibrium particle shape. The model predicts well the different stages of liquid-phase migration observed experimentally.

Simulation of hydrologic influences on wetland ecosystem succession. Master's thesis

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

Pompilio, R.A.

1994-09-01

This research focuses on the development of a simulation model to determine the affects of hydrological influences on a wetland ecosystem. The model allows perturbations to the inputs of various wetland data which in turn, influences the successional development of the ecosystem. This research consisted of converting a grassland ecosystem model to one which simulates wetland conditions. The critical factor in determining the success of wetland creation is the hydrology of the system. There are four of the areas of the original model which are affected by the hydrology. The model measures the health or success of the ecosystem throughmore » the measurement of the systems gross plant production, the respiration and the net primary production of biomass. Altering the auxiliary variables of water level and the rate of flow through the system explicitly details the affects hydrologic influences on those production rates. Ten case tests depicting exogenous perturbations of the hydrology were run to identify these affects. Although the tests dealt with the fluctuation of water through the system, any one of the auxiliary variables in the model could be changed to reflect site specific data. Productivity, Hazardous material management, Hazardous material pharmacy.« less

[Modeling and experimental study on frequency-domain electricity properties of biological materials].

PubMed

Tian, Hua; Luo, Shiqiang; Zhang, Rui; Yang, Gang; Huang, Hua

2009-12-01

Frequency-domain electricity properties of four objects, including bullfrog skin, bullfrog muscle, triply distilled water and 0.9% NaCl, were tested in the range of 100Hz-10MHz using home-made electrode and measuring system. The experimental results showed that the resistance of 0.9% NaCl decreased dramatically, that the amplitude frequency characteristics of bullfrog's muscle and skin were similar, but that of triply distilled water did not change significantly. The frequency dependence of 0.9% NaCl showed that the electrode had great influence on the measuring system, so a new equivalent circuit model based on the electrode system was needed. These findings suggest that the new five-parameter equivalent circuit model, which embodies considerations on the interaction between electrodes and tissues, is a reasonable equivalent circuit for studying the electrical characteristics of biological materials.

Estimating the Fully Burdened Cost of Fuel Using an Input-Output Model - A Micro-Level Analysis

DTIC Science & Technology

2011-09-01

The multilocation distribution model used by Lu and Rencheng to evaluate an international supply chain (From: Lu & Rencheng, 2007...IO model to evaluate an international supply chain specifically for a multilocation production system. Figure 2 illustrates such a system. vendor...vendor vendor Target markets Production plants Material vendor Figure 2. The multilocation distribution model used by Lu and Rencheng to

Industrial Automation Mechanic Model Curriculum Project. Final Report.

ERIC Educational Resources Information Center

Toledo Public Schools, OH.

This document describes a demonstration program that developed secondary level competency-based instructional materials for industrial automation mechanics. Program activities included task list compilation, instructional materials research, learning activity packet (LAP) development, construction of lab elements, system implementation,…

MaMR: High-performance MapReduce programming model for material cloud applications

NASA Astrophysics Data System (ADS)

Jing, Weipeng; Tong, Danyu; Wang, Yangang; Wang, Jingyuan; Liu, Yaqiu; Zhao, Peng

2017-02-01

With the increasing data size in materials science, existing programming models no longer satisfy the application requirements. MapReduce is a programming model that enables the easy development of scalable parallel applications to process big data on cloud computing systems. However, this model does not directly support the processing of multiple related data, and the processing performance does not reflect the advantages of cloud computing. To enhance the capability of workflow applications in material data processing, we defined a programming model for material cloud applications that supports multiple different Map and Reduce functions running concurrently based on hybrid share-memory BSP called MaMR. An optimized data sharing strategy to supply the shared data to the different Map and Reduce stages was also designed. We added a new merge phase to MapReduce that can efficiently merge data from the map and reduce modules. Experiments showed that the model and framework present effective performance improvements compared to previous work.

Modeling Climate Dynamically

ERIC Educational Resources Information Center

Walsh, Jim; McGehee, Richard

2013-01-01

A dynamical systems approach to energy balance models of climate is presented, focusing on low order, or conceptual, models. Included are global average and latitude-dependent, surface temperature models. The development and analysis of the differential equations and corresponding bifurcation diagrams provides a host of appropriate material for…

Economic analysis of linking operating room scheduling and hospital material management information systems for just-in-time inventory control.

PubMed

Epstein, R H; Dexter, F

2000-08-01

Operating room (OR) scheduling information systems can decrease perioperative labor costs. Material management information systems can decrease perioperative inventory costs. We used computer simulation to investigate whether using the OR schedule to trigger purchasing of perioperative supplies is likely to further decrease perioperative inventory costs, as compared with using sophisticated, stand-alone material management inventory control. Although we designed the simulations to favor financially linking the information systems, we found that this strategy would be expected to decrease inventory costs substantively only for items of high price ($1000 each) and volume (>1000 used each year). Because expensive items typically have different models and sizes, each of which is used by a hospital less often than this, for almost all items there will be no benefit to making daily adjustments to the order volume based on booked cases. We conclude that, in a hospital with a sophisticated material management information system, OR managers will probably achieve greater cost reductions from focusing on negotiating less expensive purchase prices for items than on trying to link the OR information system with the hospital's material management information system to achieve just-in-time inventory control. In a hospital with a sophisticated material management information system, operating room managers will probably achieve greater cost reductions from focusing on negotiating less expensive purchase prices for items than on trying to link the operating room information system with the hospital's material management information system to achieve just-in-time inventory control.

SaLEM (v1.0) - the Soil and Landscape Evolution Model (SaLEM) for simulation of regolith depth in periglacial environments

NASA Astrophysics Data System (ADS)

Bock, Michael; Conrad, Olaf; Günther, Andreas; Gehrt, Ernst; Baritz, Rainer; Böhner, Jürgen

2018-04-01

We propose the implementation of the Soil and Landscape Evolution Model (SaLEM) for the spatiotemporal investigation of soil parent material evolution following a lithologically differentiated approach. Relevant parts of the established Geomorphic/Orogenic Landscape Evolution Model (GOLEM) have been adapted for an operational Geographical Information System (GIS) tool within the open-source software framework System for Automated Geoscientific Analyses (SAGA), thus taking advantage of SAGA's capabilities for geomorphometric analyses. The model is driven by palaeoclimatic data (temperature, precipitation) representative of periglacial areas in northern Germany over the last 50 000 years. The initial conditions have been determined for a test site by a digital terrain model and a geological model. Weathering, erosion and transport functions are calibrated using extrinsic (climatic) and intrinsic (lithologic) parameter data. First results indicate that our differentiated SaLEM approach shows some evidence for the spatiotemporal prediction of important soil parental material properties (particularly its depth). Future research will focus on the validation of the results against field data, and the influence of discrete events (mass movements, floods) on soil parent material formation has to be evaluated.

Non-destructive sampling of a comet

NASA Astrophysics Data System (ADS)

Jessberger, H. L.; Kotthaus, M.

1991-04-01

Various conditions which must be met for the development of a nondestructive sampling and acquisition system are outlined and the development of a new robotic sampling system suited for use on a cometary surface is briefly discussed. The Rosetta mission of ESA will take samples of a comet nucleus and return both core and volatile samples to earth. Various considerations which must be taken into account for such a project are examined including the identification of design parameters for sample quality; the identification of the most probable site conditions; the development of a sample acquisition system with respect to these conditions; the production of model materials and model conditions; and the investigation of the relevant material properties. An adequate sampling system should also be designed and built, including various tools, and the system should be tested under simulated cometary conditions.

Accelerated discovery of metallic glasses through iteration of machine learning and high-throughput experiments

PubMed Central

Wolverton, Christopher; Hattrick-Simpers, Jason; Mehta, Apurva

2018-01-01

With more than a hundred elements in the periodic table, a large number of potential new materials exist to address the technological and societal challenges we face today; however, without some guidance, searching through this vast combinatorial space is frustratingly slow and expensive, especially for materials strongly influenced by processing. We train a machine learning (ML) model on previously reported observations, parameters from physiochemical theories, and make it synthesis method–dependent to guide high-throughput (HiTp) experiments to find a new system of metallic glasses in the Co-V-Zr ternary. Experimental observations are in good agreement with the predictions of the model, but there are quantitative discrepancies in the precise compositions predicted. We use these discrepancies to retrain the ML model. The refined model has significantly improved accuracy not only for the Co-V-Zr system but also across all other available validation data. We then use the refined model to guide the discovery of metallic glasses in two additional previously unreported ternaries. Although our approach of iterative use of ML and HiTp experiments has guided us to rapid discovery of three new glass-forming systems, it has also provided us with a quantitatively accurate, synthesis method–sensitive predictor for metallic glasses that improves performance with use and thus promises to greatly accelerate discovery of many new metallic glasses. We believe that this discovery paradigm is applicable to a wider range of materials and should prove equally powerful for other materials and properties that are synthesis path–dependent and that current physiochemical theories find challenging to predict. PMID:29662953

Accelerated discovery of metallic glasses through iteration of machine learning and high-throughput experiments

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

Ren, Fang; Ward, Logan; Williams, Travis

With more than a hundred elements in the periodic table, a large number of potential new materials exist to address the technological and societal challenges we face today; however, without some guidance, searching through this vast combinatorial space is frustratingly slow and expensive, especially for materials strongly influenced by processing. We train a machine learning (ML) model on previously reported observations, parameters from physiochemical theories, and make it synthesis method–dependent to guide high-throughput (HiTp) experiments to find a new system of metallic glasses in the Co-V-Zr ternary. Experimental observations are in good agreement with the predictions of the model, butmore » there are quantitative discrepancies in the precise compositions predicted. We use these discrepancies to retrain the ML model. The refined model has significantly improved accuracy not only for the Co-V-Zr system but also across all other available validation data. We then use the refined model to guide the discovery of metallic glasses in two additional previously unreported ternaries. Although our approach of iterative use of ML and HiTp experiments has guided us to rapid discovery of three new glass-forming systems, it has also provided us with a quantitatively accurate, synthesis method–sensitive predictor for metallic glasses that improves performance with use and thus promises to greatly accelerate discovery of many new metallic glasses. We believe that this discovery paradigm is applicable to a wider range of materials and should prove equally powerful for other materials and properties that are synthesis path–dependent and that current physiochemical theories find challenging to predict.« less

Accelerated discovery of metallic glasses through iteration of machine learning and high-throughput experiments

DOE PAGES

Ren, Fang; Ward, Logan; Williams, Travis; ...

2018-04-01

With more than a hundred elements in the periodic table, a large number of potential new materials exist to address the technological and societal challenges we face today; however, without some guidance, searching through this vast combinatorial space is frustratingly slow and expensive, especially for materials strongly influenced by processing. We train a machine learning (ML) model on previously reported observations, parameters from physiochemical theories, and make it synthesis method–dependent to guide high-throughput (HiTp) experiments to find a new system of metallic glasses in the Co-V-Zr ternary. Experimental observations are in good agreement with the predictions of the model, butmore » there are quantitative discrepancies in the precise compositions predicted. We use these discrepancies to retrain the ML model. The refined model has significantly improved accuracy not only for the Co-V-Zr system but also across all other available validation data. We then use the refined model to guide the discovery of metallic glasses in two additional previously unreported ternaries. Although our approach of iterative use of ML and HiTp experiments has guided us to rapid discovery of three new glass-forming systems, it has also provided us with a quantitatively accurate, synthesis method–sensitive predictor for metallic glasses that improves performance with use and thus promises to greatly accelerate discovery of many new metallic glasses. We believe that this discovery paradigm is applicable to a wider range of materials and should prove equally powerful for other materials and properties that are synthesis path–dependent and that current physiochemical theories find challenging to predict.« less

Phase change energy storage for solar dynamic power systems

NASA Technical Reports Server (NTRS)

Chiaramonte, F. P.; Taylor, J. D.

1992-01-01

This paper presents the results of a transient computer simulation that was developed to study phase change energy storage techniques for Space Station Freedom (SSF) solar dynamic (SD) power systems. Such SD systems may be used in future growth SSF configurations. Two solar dynamic options are considered in this paper: Brayton and Rankine. Model elements consist of a single node receiver and concentrator, and takes into account overall heat engine efficiency and power distribution characteristics. The simulation not only computes the energy stored in the receiver phase change material (PCM), but also the amount of the PCM required for various combinations of load demands and power system mission constraints. For a solar dynamic power system in low earth orbit, the amount of stored PCM energy is calculated by balancing the solar energy input and the energy consumed by the loads corrected by an overall system efficiency. The model assumes an average 75 kW SD power system load profile which is connected to user loads via dedicated power distribution channels. The model then calculates the stored energy in the receiver and subsequently estimates the quantity of PCM necessary to meet peaking and contingency requirements. The model can also be used to conduct trade studies on the performance of SD power systems using different storage materials.

Phase change energy storage for solar dynamic power systems

NASA Astrophysics Data System (ADS)

Chiaramonte, F. P.; Taylor, J. D.

This paper presents the results of a transient computer simulation that was developed to study phase change energy storage techniques for Space Station Freedom (SSF) solar dynamic (SD) power systems. Such SD systems may be used in future growth SSF configurations. Two solar dynamic options are considered in this paper: Brayton and Rankine. Model elements consist of a single node receiver and concentrator, and takes into account overall heat engine efficiency and power distribution characteristics. The simulation not only computes the energy stored in the receiver phase change material (PCM), but also the amount of the PCM required for various combinations of load demands and power system mission constraints. For a solar dynamic power system in low earth orbit, the amount of stored PCM energy is calculated by balancing the solar energy input and the energy consumed by the loads corrected by an overall system efficiency. The model assumes an average 75 kW SD power system load profile which is connected to user loads via dedicated power distribution channels. The model then calculates the stored energy in the receiver and subsequently estimates the quantity of PCM necessary to meet peaking and contingency requirements. The model can also be used to conduct trade studies on the performance of SD power systems using different storage materials.

Mechanisms of deterioration of nutrients. [freeze drying methods for space flight food

NASA Technical Reports Server (NTRS)

Karel, M.; Flink, J. M.

1974-01-01

Methods are reported by which freeze dried foods of improved quality will be produced. The applicability of theories of flavor retention has been demonstrated for a number of food polymers, both proteins and polysacchardies. Studies on the formation of structures during freeze drying have been continued for emulsified systems. Deterioration of organoleptic quality of freeze dried foods due to high temperature heating has been evaluated and improved procedures developed. The influence of water activity and high temperature on retention of model flavor materials and browning deterioration has been evaluated for model systems and food materials.

Structural damping studies at cryogenic temperatures

NASA Technical Reports Server (NTRS)

Young, Clarence P., Jr.; Buehrle, Ralph D.

1994-01-01

Results of an engineering study to measure changes in structural damping properties of two cryogenic wind tunnel model systems and two metallic test specimens at cryogenic temperatures are presented. Data are presented which indicate overall, a trend toward reduced structural damping at cryogenic temperatures (-250 degrees F) when compared with room temperature damping properties. The study was focused on structures and materials used for model systems tested in the National Transonic Facility (NTF). The study suggests that the significant reductions in damping at extremely cold temperatures are most likely associated with changes in mechanical joint compliance damping rather than changes in material (solid) damping.

Manufacturing process and material selection in concurrent collaborative design of MEMS devices

NASA Astrophysics Data System (ADS)

Zha, Xuan F.; Du, H.

2003-09-01

In this paper we present knowledge of an intensive approach and system for selecting suitable manufacturing processes and materials for microelectromechanical systems (MEMS) devices in concurrent collaborative design environment. In the paper, fundamental issues on MEMS manufacturing process and material selection such as concurrent design framework, manufacturing process and material hierarchies, and selection strategy are first addressed. Then, a fuzzy decision support scheme for a multi-criteria decision-making problem is proposed for estimating, ranking and selecting possible manufacturing processes, materials and their combinations. A Web-based prototype advisory system for the MEMS manufacturing process and material selection, WebMEMS-MASS, is developed based on the client-knowledge server architecture and framework to help the designer find good processes and materials for MEMS devices. The system, as one of the important parts of an advanced simulation and modeling tool for MEMS design, is a concept level process and material selection tool, which can be used as a standalone application or a Java applet via the Web. The running sessions of the system are inter-linked with webpages of tutorials and reference pages to explain the facets, fabrication processes and material choices, and calculations and reasoning in selection are performed using process capability and material property data from a remote Web-based database and interactive knowledge base that can be maintained and updated via the Internet. The use of the developed system including operation scenario, use support, and integration with an MEMS collaborative design system is presented. Finally, an illustration example is provided.

A sorption model for alkalis in cement-based materials - Correlations with solubility and electrokinetic properties

NASA Astrophysics Data System (ADS)

Henocq, Pierre

2017-06-01

In cement-based materials, radionuclide uptake is mainly controlled by calcium silicate hydrates (C-S-H). This work presents an approach for defining a unique set of parameters of a surface complexation model describing the sorption behavior of alkali ions on the C-S-H surface. Alkali sorption processes are modeled using the CD-MUSIC function integrated in the Phreeqc V.3.0.6 geochemical code. Parameterization of the model was performed based on (1) retention, (2) zeta potential, and (3) solubility experimental data from the literature. This paper shows an application of this model to sodium ions. It was shown that retention, i.e. surface interactions, and solubility are closely related, and a consistent sorption model for radionuclides in cement-based materials requires a coupled surface interaction/chemical equilibrium model. In case of C-S-H with low calcium-to-silicon ratios, sorption of sodium ions on the C-S-H surface strongly influences the chemical equilibrium of the C-S-H + NaCl system by significantly increasing the aqueous calcium concentration. The close relationship between sorption and chemical equilibrium was successfully illustrated by modeling the effect of the solid-to-liquid ratio on the calcium content in solution in the case of C-S-H + NaCl systems.

MECHANICAL PROPERTY CHARACTERIZATIONS AND PERFORMANCE MODELING OF SOFC SEALS

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

Koeppel, Brian J.; Vetrano, John S.; Nguyen, Ba Nghiep

2008-03-26

This study provides modeling tools for the design of reliable seals for SOFC stacks. The work consists of 1) experimental testing to determine fundamental properties of SOFC sealing materials, and 2) numerical modeling of stacks and sealing systems. The material tests capture relevant temperature-dependent physical and mechanical data needed by the analytical models such as thermal expansion, strength, fracture toughness, and relaxation behavior for glass-ceramic seals and other materials. Testing has been performed on both homogenous specimens and multiple material assemblies to investigate the effect of interfacial reactions. A viscoelastic continuum damage model for a glass-ceramic seal was developed tomore » capture the nonlinear behavior of this material at high temperatures. This model was implemented in the MSC MARC finite element code and was used for a detailed analysis of a planar SOFC stack under thermal cycling conditions. Realistic thermal loads for the stack were obtained using PNNL’s in-house multiphysics solver. The accumulated seal damage and component stresses were evaluated for multiple thermal loading cycles, and regions of high seal damage susceptible to cracking were identified. Selected test results, numerical model development, and analysis results will be presented.« less

Water Plan 2030: A Dynamic Education Model for Teaching Water Management Issues

NASA Astrophysics Data System (ADS)

Rupprecht, C.; Washburne, J.; Lansey, K.; Williams, A.

2006-12-01

Dynamic educational tools to assist teachers and students in recognizing the impacts of water management decisions in a realistic context are not readily available. Water policy issues are often complex and difficult for students trying to make meaningful connections between system components. To fill this need, we have developed a systems modeling-based educational decision support system (DSS) with supplementary materials. This model, called Water Plan 2030, represents a general semi-arid watershed; it allows users to examine water management alternatives by changing input values for various water uses and basin conditions and immediately receive graphical outputs to compare decisions. The main goal of our DSS model is to foster students' abilities to make knowledgeable decisions with regard to water resources issues. There are two reasons we have developed this model for traditional classroom settings. First, the DSS model provides teachers with a mechanism for educating students about inter-related hydrologic concepts, complex systems and facilitates discussion of water resources issues. Second, Water Plan 2030 encourages student discovery of cause/effect relationships in a dynamic, hands-on environment and develops the ability to realize the implications of water management alternatives. The DSS model has been utilized in an undergraduate, non-major science class for 5 course hours, each of the past 4 semesters. Accompanying the PC-based model are supplementary materials to improve the effectiveness of implementation by emphasizing important concepts and guiding learners through the model components. These materials include in-class tutorials, introductory questions, role-playing activities and homework extensions that have been revised after each user session, based on student and instructor feedback. Most recently, we have developed individual lessons that teach specific model functions and concepts. These modules provide teachers the flexibility to adapt the model to meet numerous teaching goals. Evaluation results indicate that students improved their understanding of fundamental concepts and system interactions and showed the most improvement in questions related to water use by sector and sustainability issues. Model modifications have also improved student feedback of the model effectiveness and user- friendliness. Positive results from this project have created the demand for a web-based version, which will be online in late 2006.

Brillouin Spectroscopy at the GeoForschungsZentrum-Potsdam: Applications in Geosciences and Materials Science

NASA Astrophysics Data System (ADS)

Marquardt, H.; Speziale, S.; Reichmann, H. J.; Schmidt, C.; Schilling, F.

2007-12-01

Knowledge of the elastic properties of earth materials at relevant pressures and temperatures is prerequisite to adequately interpret seismic data and improve our understanding of the composition and mineralogy of the earth's interior. The study of pressure and temperature dependence of acoustic velocity in geo-fluids gives us information about their density with implications for the thermodynamic modelling of diagenetic and metamorphic processes. Furthermore elasticity of synthetic materials is of major interest for several industrial applications. We have recently completed the construction of a new Brillouin System at the GeoForschungsZentrum Potsdam. The new system has been designed to study elasticity of various geological as well as industrial materials at different pressure and temperature conditions. Our Brillouin system consists of a Nd:YVO4 solid state laser operating at a wavelength of 532 nm as light source and a Sandercock-type tandem multipass Fabry-Perot interferometer equipped with a photomultiplier tube for signal detection. Measurements can be performed in 60 or 90 degree symmetric forward scattering or in backscattering geometry. The large positioning system also allows for high temperature measurements in an externally heated diamond anvil cell. We present first results of elasticity measurements both on Earth's materials, such as silicates garnets and oxides, as well as hydroxides and commercially used garnet aluminates, and silicate and borate glasses as proxies for melts. Brillouin scattering has been measured to constrain the density of water-NaCl solutions, for the precise thermodynamic modelling of fluids in metamorphic systems.

DEMONSTRATION OF LEACHXS/ORCHESTRA CAPABILITIES BY SIMULATING CONSTITUENT RELEASE FROM A CEMENTITIOUS WASTE FORM IN A REINFORCED CONCRETE VAULT

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

Langton, C.; Meeussen, J.; Sloot, H.

2010-03-31

The objective of the work described in this report is to demonstrate the capabilities of the current version of LeachXS{trademark}/ORCHESTRA for simulating chemical behavior and constituent release processes in a range of applications that are relevant to the CBP. This report illustrates the use of LeachXS{trademark}/ORCHESTRA for the following applications: (1) Comparing model and experimental results for leaching tests for a range of cementitious materials including cement mortars, grout, stabilized waste, and concrete. The leaching test data includes liquid-solid partitioning as a function of pH and release rates based on laboratory column, monolith, and field testing. (2) Modeling chemical speciationmore » of constituents in cementitious materials, including liquid-solid partitioning and release rates. (3) Evaluating uncertainty in model predictions based on uncertainty in underlying composition, thermodynamic, and transport characteristics. (4) Generating predominance diagrams to evaluate predicted chemical changes as a result of material aging using the example of exposure to atmospheric conditions. (5) Modeling coupled geochemical speciation and diffusion in a three layer system consisting of a layer of Saltstone, a concrete barrier, and a layer of soil in contact with air. The simulations show developing concentration fronts over a time period of 1000 years. (6) Modeling sulfate attack and cracking due to ettringite formation. A detailed example for this case is provided in a separate article by the authors (Sarkar et al. 2010). Finally, based on the computed results, the sensitive input parameters for this type of modeling are identified and discussed. The chemical speciation behavior of substances is calculated for a batch system and also in combination with transport and within a three layer system. This includes release from a barrier to the surrounding soil as a function of time. As input for the simulations, the physical and chemical properties of the materials are used. The test cases used in this demonstration are taken from Reference Cases for Use in the Cementitious Barriers Partnership (Langton et al. 2009). Before it is possible to model the release of substances from stabilized waste or radioactive grout through a cement barrier into the engineered soil barrier or natural soil, the relevant characteristics of such materials must be known. Additional chemical characteristics are needed for mechanistic modeling to be undertaken, not just the physical properties relevant for modeling of transport. The minimum required properties for modeling are given in Section 5.0, 'Modeling the chemical speciation of a material'.« less

Kelvin-Voigt model of wave propagation in fragmented geomaterials with impact damping

NASA Astrophysics Data System (ADS)

Khudyakov, Maxim; Pasternak, Elena; Dyskin, Arcady

2017-04-01

When a wave propagates through real materials, energy dissipation occurs. The effect of loss of energy in homogeneous materials can be accounted for by using simple viscous models. However, a reliable model representing the effect in fragmented geomaterials has not been established yet. The main reason for that is a mechanism how vibrations are transmitted between the elements (fragments) in these materials. It is hypothesised that the fragments strike against each other, in the process of oscillation, and the impacts lead to the energy loss. We assume that the energy loss is well represented by the restitution coefficient. The principal element of this concept is the interaction of two adjacent blocks. We model it by a simple linear oscillator (a mass on an elastic spring) with an additional condition: each time the system travels through the neutral point, where the displacement is equal to zero, the velocity reduces by multiplying itself by the restitution coefficient, which characterises an impact of the fragments. This additional condition renders the system non-linear. We show that the behaviour of such a model averaged over times much larger than the system period can approximately be represented by a conventional linear oscillator with linear damping characterised by a damping coefficient expressible through the restitution coefficient. Based on this the wave propagation at times considerably greater than the resonance period of oscillations of the neighbouring blocks can be modelled using the Kelvin-Voigt model. The wave velocities and the dispersion relations are obtained.

Mobile Pit verification system design based on passive special nuclear material verification in weapons storage facilities

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

Paul, J. N.; Chin, M. R.; Sjoden, G. E.

2013-07-01

A mobile 'drive by' passive radiation detection system to be applied in special nuclear materials (SNM) storage facilities for validation and compliance purposes has been designed through the use of computational modeling and new radiation detection methods. This project was the result of work over a 1 year period to create optimal design specifications to include creation of 3D models using both Monte Carlo and deterministic codes to characterize the gamma and neutron leakage out each surface of SNM-bearing canisters. Results were compared and agreement was demonstrated between both models. Container leakages were then used to determine the expected reactionmore » rates using transport theory in the detectors when placed at varying distances from the can. A 'typical' background signature was incorporated to determine the minimum signatures versus the probability of detection to evaluate moving source protocols with collimation. This established the criteria for verification of source presence and time gating at a given vehicle speed. New methods for the passive detection of SNM were employed and shown to give reliable identification of age and material for highly enriched uranium (HEU) and weapons grade plutonium (WGPu). The finalized 'Mobile Pit Verification System' (MPVS) design demonstrated that a 'drive-by' detection system, collimated and operating at nominally 2 mph, is capable of rapidly verifying each and every weapon pit stored in regularly spaced, shelved storage containers, using completely passive gamma and neutron signatures for HEU and WGPu. This system is ready for real evaluation to demonstrate passive total material accountability in storage facilities. (authors)« less

Investigation of α-MnO 2 Tunneled Structures as Model Cation Hosts for Energy Storage

DOE PAGES

Housel, Lisa M.; Wang, Lei; Abraham, Alyson; ...

2018-02-19

Future advances in energy storage systems rely on identification of appropriate target materials and deliberate synthesis of the target materials with control of their physiochemical properties in order to disentangling the contributions of distinct properties to the functional electrochemistry. Furthermore, this goal demands systematic inquiry using model materials that provide the opportunity for significant synthetic versatility and control. Ideally, a material family that enables direct manipulation of characteristics including composition, defects and crystallite size while remaining within the defined structural framework would be necessary. Accomplishing this through direct synthetic methods is desirable to minimize the complicating effects of secondary processing.

Investigation of α-MnO 2 Tunneled Structures as Model Cation Hosts for Energy Storage

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

Housel, Lisa M.; Wang, Lei; Abraham, Alyson

Future advances in energy storage systems rely on identification of appropriate target materials and deliberate synthesis of the target materials with control of their physiochemical properties in order to disentangling the contributions of distinct properties to the functional electrochemistry. Furthermore, this goal demands systematic inquiry using model materials that provide the opportunity for significant synthetic versatility and control. Ideally, a material family that enables direct manipulation of characteristics including composition, defects and crystallite size while remaining within the defined structural framework would be necessary. Accomplishing this through direct synthetic methods is desirable to minimize the complicating effects of secondary processing.

Ablative thermal management structural material on the hypersonic vehicles

NASA Astrophysics Data System (ADS)

Shortland, H.; Tsai, C.

A hypersonic vehicle is designed to fly at high Mach number in the earth's atmosphere that will result in higher aerodynamic heating loads on specific areas of the vehicle. A thermal protection system is required for these areas that may exceed the operating temperature limit of structural materials. This paper delineates the application of ablative material as the passive type of thermal protection system for the nose or wing leading edges. A simplified quasi-steady-state one-dimensional computer model was developed to evaluate the performance and thermal design of a leading edge. The detailed description of the governing mathematical equations and results are presented. This model provides a quantitative information to support the design estimate, performance optimization, and assess preliminary feasibility of using ablation as a design approach.

Microfissuring of Inconel 718

NASA Technical Reports Server (NTRS)

Nunes, A. C., Jr.

1983-01-01

A tentative mathematical computer model of the microfissuring process during electron beam welding of Inconel 718 has been constructed. Predictions of the model are compatible with microfissuring tests on eight 0.25-in. thick test plates. The model takes into account weld power and speed, weld loss (efficiency), parameters and material characteristics. Besides the usual material characteristics (thermal and strength properties), a temperature and grain size dependent critical fracture strain is required by the model. The model is based upon fundamental physical theory (i.e., it is not a mere data interpolation system), and can be extended to other metals by suitable parameter changes.

Color Choice is Everything - Impacts Color makes to the Lighting Environment

NASA Technical Reports Server (NTRS)

Clark, Toni A.

2012-01-01

When contracts are let out to design multiple systems in a vehicle, it is a challenge to maintain integration between system leads. Designers on niche systems, like lighting and control panel design, often get caught up in the challenge of designing the light source or visual interface and fail to include time in their schedule to work with system architects on how their lighting system will be integrated. Additionally, behavioral scientists, industrial designers, and materials engineers get caught up with the materials and look of the system, but often fail to consider how the selection of their materials could affect the certification or performance of electronic devices like lighting systems. Additionally, computer modeling of the system architecture often assumes a perfect environment without the clutter of actual human use (dirt, stowage, crowding). As a result, lighting systems, and backlit displays run the risk of being overdesigned or under designed. Engineers making the assumption that because they have no input or there is no requirement on work surface reflectance, make the assumption that they can t count on good material choices and thus may install more lighting than is necessary. While having more lights may seem better, for a vehicle that is trying to conserve power, more lights may not be a good option. On the other hand, designers who made the opposite assumption and designed a lighting system that only produced just enough light, often wind up with a system that did conserve power, but didn t produce enough light. These situations are exasperated when the system starts to be used and the models are not perfect anymore. The lack of coordination and iterative design not only can impact lighting levels within an environment, but also can affect color perception. This is because, if materials do not represent a gradation of white or black, the material unevenly absorbs and reflects light at different wavelengths of the visual spectrum. The lighting designer may have built a light that meets light spectra requirements, but the eventual light reaching the human user may not be the spectra of light architects intended, if materials near the light source change the spectrum just by how much color is absorbed or reflected. With the recent findings concerning Circadian rhythm, where the spectra of light is extremely important for addressing crew sleep and wake cycles, system architects should pay considerable attention on the impact material choices have in changing the light spectrum in an environment. This presentation will show examples of how material choices impact the resulting illuminance, color spectrum, and power usage of an illuminated space. Its goal is to encourage system designers and planners to use more care in development of requirements and the verification of systems intended for the human visual interface.

New developments in tribomechanical modeling of automotive sheet steel forming

NASA Astrophysics Data System (ADS)

Khandeparkar, Tushar; Chezan, Toni; van Beeck, Jeroen

2018-05-01

Forming of automotive sheet metal body panels is a complex process influenced by both the material properties and contact conditions in the forming tooling. Material properties are described by the material constitutive behavior and the material flow into the forming die can be described by the tribological system. This paper investigates the prediction accuracy of the forming process using the Tata Steel state of the art description of the material constitutive behavior in combination with different friction models. A cross-die experiment is used to investigate the accuracy of local deformation modes typically seen in automotive sheet metal forming operations. Results of advanced friction models as well as the classical Coulomb friction description are compared to the experimentally measured strain distribution and material draw-in. Two hot-dip galvanized coated steel forming grades were used for the investigations. The results show that the accuracy of the simulation is not guaranteed by the advanced friction models for the entire investigated blank holder force range, both globally and locally. A measurable difference between the calculated and measured local strains is seen for both studied models even in the case where the global indicator, i.e. the draw-in, is well predicted.

Cyclic voltammetry modeling of proton transport effects on redox charge storage in conductive materials: application to a TiO2 mesoporous film.

PubMed

Kim, Y S; Balland, V; Limoges, B; Costentin, C

2017-07-21

Cyclic voltammetry is a particularly useful tool for characterizing charge accumulation in conductive materials. A simple model is presented to evaluate proton transport effects on charge storage in conductive materials associated with a redox process coupled with proton insertion in the bulk material from an aqueous buffered solution, a situation frequently encountered in metal oxide materials. The interplay between proton transport inside and outside the materials is described using a formulation of the problem through introduction of dimensionless variables that allows defining the minimum number of parameters governing the cyclic voltammetry response with consideration of a simple description of the system geometry. This approach is illustrated by analysis of proton insertion in a mesoporous TiO 2 film.

Friction and wear of sintered fiber-metal abradable seal materials

NASA Technical Reports Server (NTRS)

Bill, R. C.; Shiembob, L. T.

1977-01-01

Three abradable gas path seal material systems based on a sintered NiCrAlY fibermetal structure were evaluated under a range of wear conditions representative of those likely to be encountered in various knife-edge seal (labyrinth or shrouded turbine) applications. Conditions leading to undesirable wear of the rotating knife were identified and a model was proposed based on thermal effects arising under different rub conditions. It was found, and predicted by the model, that low incursion (plunge) rates tended to promote smearing of the low density sintered material with consequent wear to the knife-edge. Tradeoffs benefits between baseline 19 percent dense material, a similar material of increased density, and a self lubricating coating applied to the 19 percent material were identified based on relative rub tolerance and erosion resistance.

Neural system modeling and simulation using Hybrid Functional Petri Net.

PubMed

Tang, Yin; Wang, Fei

2012-02-01

The Petri net formalism has been proved to be powerful in biological modeling. It not only boasts of a most intuitive graphical presentation but also combines the methods of classical systems biology with the discrete modeling technique. Hybrid Functional Petri Net (HFPN) was proposed specially for biological system modeling. An array of well-constructed biological models using HFPN yielded very interesting results. In this paper, we propose a method to represent neural system behavior, where biochemistry and electrical chemistry are both included using the Petri net formalism. We built a model for the adrenergic system using HFPN and employed quantitative analysis. Our simulation results match the biological data well, showing that the model is very effective. Predictions made on our model further manifest the modeling power of HFPN and improve the understanding of the adrenergic system. The file of our model and more results with their analysis are available in our supplementary material.

Effects of Phase Transformations and Dynamic Material Strength on Hydrodynamic Instability Evolution in Metals

NASA Astrophysics Data System (ADS)

Opie, Saul

Hydrodynamic phenomena such as the Rayleigh-Taylor (RT) and Richtmyer-Meshkov (RM) instabilities can be described by exponential/linear growth of surface perturbations at a bimaterial interface when subjected to constant/impulsive acceleration. A challenge in designing systems to mitigate or exploit these effects is the lack of accurate material models at large dynamic strain rates and pressures. In particular, little stress-strain constitutive information at large strain rates and pressures is available for transient material phases formed at high pressures, and the continuum effect the phase transformation process has on the instability evolution. In this work, a phase-aware isotropic strength model is developed and partially validated with a novel RM-based instability experiment in addition to existing data from the literature. With the validated material model additional simulations are performed to provide insight into to the role that robust material constitutive behavior (e.g., pressure, temperature, rate dependence) has on RM instability and how RM instability experiments can be used to characterize and validated expected material behavior. For phase aware materials, particularly iron in this work, the simulations predict a strong dependence on the Atwood number that single phase materials do not have. At Atwood numbers close to unity, and pressures in the high pressure stability region, the high pressure phase dominates the RM evolution. However, at Atwood numbers close to negative one, the RM evolution is only weakly affected by the high-pressure phase even for shocks well above the phase transformation threshold. In addition to RM evolution this work looks at the closely related shock front perturbation evolution. Existing analytical models for isentropic processes in gases and liquids are modified for metal equation of states and plastic behavior for the first time. It is found that the presence of a volume collapsing phase transformation with increased pressure causes shock front perturbations to decay sooner, while plastic strength has the opposite effect which is significantly different from the effect viscosity has. These results suggest additional experimental setups to validate material models, or relevant material parameters that can be optimized for system design objectives, e.g., minimize feed through perturbations in inertial confinement fusion capsules.

EDITORIAL: Adaptive and Active Materials: Selected Papers from the ASME 2008 Conference on Smart Materials, Adaptive Structures and Intelligent Systems (SMASIS 08) (Maryland, USA, 28-30 October 2008) Adaptive and Active Materials: Selected Papers from the ASME 2008 Conference on Smart Materials, Adaptive Structures and Intelligent Systems (SMASIS 08) (Maryland, USA, 28-30 October 2008)

NASA Astrophysics Data System (ADS)

Lynch, Christopher

2009-10-01

The rapid development of the field of Smart Materials, Adaptive Structures, and Materials Systems led the Aerospace Division ASMS TC to launch the new annual SMASIS conference in 2008. The conference focuses on the multi-disciplinary challenges of developing new multifunctional materials and implementing them in advanced systems. The research spans length scales from nano-structured materials to civil, air, and space structures. The first conference consisted of six symposia, each focusing on a different research area. This special issue of Smart Materials and Structures summarizes some of the top research presented at the 2008 SMASIS conference in the materials-focused symposia. These symposia focused on the behavior and mechanics of active materials, on multifunctional materials, and on bio-inspired materials. The behavior and mechanics of active materials is an approach that combines observed material behavior with mechanism-based models that not only give insight into the observed behavior, but guide the development of new materials. This approach has been applied to shape memory metals and polymers, ferroelectrics, ferromagnetics, and recently to multiferroic materials, and has led to considerable improvements in our understanding of multi-field phenomena. Multifunctional materials are the next generation of active materials. These materials include structural, sensing, and actuation components integrated into a material system. A natural extension of multifunctional materials is a new class of bio-inspired materials. Bio-inspired materials range from detailed bio-mimicry of sensing and self healing materials to nano and microstructures that take advantage of features observed in biological systems. The Editors would like to express their sincere thanks to all of the authors for their contributions to this special issue on 'Adaptive and Active Materials' for Smart Materials and Structures. We convey our gratitude to all of the reviewers for their time and dedication. We thank IOP Publishing for their support and encouragement of this special issue and the staff for their special attention and timely response.

Diffusion in energy materials: Governing dynamics from atomistic modelling

NASA Astrophysics Data System (ADS)

Parfitt, D.; Kordatos, A.; Filippatos, P. P.; Chroneos, A.

2017-09-01

Understanding diffusion in energy materials is critical to optimising the performance of solid oxide fuel cells (SOFCs) and batteries both of which are of great technological interest as they offer high efficiency for cleaner energy conversion and storage. In the present review, we highlight the insights offered by atomistic modelling of the ionic diffusion mechanisms in SOFCs and batteries and how the growing predictive capability of high-throughput modelling, together with our new ability to control compositions and microstructures, will produce advanced materials that are designed rather than chosen for a given application. The first part of the review focuses on the oxygen diffusion mechanisms in cathode and electrolyte materials for SOFCs and in particular, doped ceria and perovskite-related phases with anisotropic structures. The second part focuses on disordered oxides and two-dimensional materials as these are very promising systems for battery applications.

Modeling of Abrasion and Crushing of Unbound Granular Materials During Compaction

NASA Astrophysics Data System (ADS)

Ocampo, Manuel S.; Caicedo, Bernardo

2009-06-01

Unbound compacted granular materials are commonly used in engineering structures as layers in road pavements, railroad beds, highway embankments, and foundations. These structures are generally subjected to dynamic loading by construction operations, traffic and wheel loads. These repeated or cyclic loads cause abrasion and crushing of the granular materials. Abrasion changes a particle's shape, and crushing divides the particle into a mixture of many small particles of varying sizes. Particle breakage is important because the mechanical and hydraulic properties of these materials depend upon their grain size distribution. Therefore, it is important to evaluate the evolution of the grain size distribution of these materials. In this paper an analytical model for unbound granular materials is proposed in order to evaluate particle crushing of gravels and soils subjected to cyclic loads. The model is based on a Markov chain which describes the development of grading changes in the material as a function of stress levels. In the model proposed, each particle size is a state in the system, and the evolution of the material is the movement of particles from one state to another in n steps. Each step is a load cycle, and movement between states is possible with a transition probability. The crushing of particles depends on the mechanical properties of each grain and the packing density of the granular material. The transition probability was calculated using both the survival probability defined by Weibull and the compressible packing model developed by De Larrard. Material mechanical properties are considered using the Weibull probability theory. The size and shape of the grains, as well as the method of processing the packing density are considered using De Larrard's model. Results of the proposed analytical model show a good agreement with the experimental tests carried out using the gyratory compaction test.

Reducing Vehicle Weight and Improving U.S. Energy Efficiency Using Integrated Computational Materials Engineering

NASA Astrophysics Data System (ADS)

Joost, William J.

2012-09-01

Transportation accounts for approximately 28% of U.S. energy consumption with the majority of transportation energy derived from petroleum sources. Many technologies such as vehicle electrification, advanced combustion, and advanced fuels can reduce transportation energy consumption by improving the efficiency of cars and trucks. Lightweight materials are another important technology that can improve passenger vehicle fuel efficiency by 6-8% for each 10% reduction in weight while also making electric and alternative vehicles more competitive. Despite the opportunities for improved efficiency, widespread deployment of lightweight materials for automotive structures is hampered by technology gaps most often associated with performance, manufacturability, and cost. In this report, the impact of reduced vehicle weight on energy efficiency is discussed with a particular emphasis on quantitative relationships determined by several researchers. The most promising lightweight materials systems are described along with a brief review of the most significant technical barriers to their implementation. For each material system, the development of accurate material models is critical to support simulation-intensive processing and structural design for vehicles; improved models also contribute to an integrated computational materials engineering (ICME) approach for addressing technical barriers and accelerating deployment. The value of computational techniques is described by considering recent ICME and computational materials science success stories with an emphasis on applying problem-specific methods.

High-Temperature Structures, Adhesives, and Advanced Thermal Protection Materials for Next-Generation Aeroshell Design

NASA Technical Reports Server (NTRS)

Collins, Timothy J.; Congdon, William M.; Smeltzer, Stanley S.; Whitley, Karen S.

2005-01-01

The next generation of planetary exploration vehicles will rely heavily on robust aero-assist technologies, especially those that include aerocapture. This paper provides an overview of an ongoing development program, led by NASA Langley Research Center (LaRC) and aimed at introducing high-temperature structures, adhesives, and advanced thermal protection system (TPS) materials into the aeroshell design process. The purpose of this work is to demonstrate TPS materials that can withstand the higher heating rates of NASA's next generation planetary missions, and to validate high-temperature structures and adhesives that can reduce required TPS thickness and total aeroshell mass, thus allowing for larger science payloads. The effort described consists of parallel work in several advanced aeroshell technology areas. The areas of work include high-temperature adhesives, high-temperature composite materials, advanced ablator (TPS) materials, sub-scale demonstration test articles, and aeroshell modeling and analysis. The status of screening test results for a broad selection of available higher-temperature adhesives is presented. It appears that at least one (and perhaps a few) adhesives have working temperatures ranging from 315-400 C (600-750 F), and are suitable for TPS-to-structure bondline temperatures that are significantly above the traditional allowable of 250 C (482 F). The status of mechanical testing of advanced high-temperature composite materials is also summarized. To date, these tests indicate the potential for good material performance at temperatures of at least 600 F. Application of these materials and adhesives to aeroshell systems that incorporate advanced TPS materials may reduce aeroshell TPS mass by 15% - 30%. A brief outline is given of work scheduled for completion in 2006 that will include fabrication and testing of large panels and subscale aeroshell test articles at the Solar-Tower Test Facility located at Kirtland AFB and operated by Sandia National Laboratories. These tests are designed to validate aeroshell manufacturability using advanced material systems, and to demonstrate the maintenance of bondline integrity at realistically high temperatures and heating rates. Finally, a status is given of ongoing aeroshell modeling and analysis efforts which will be used to correlate with experimental testing, and to provide a reliable means of extrapolating to performance under actual flight conditions. The modeling and analysis effort includes a parallel series of experimental tests to determine TSP thermal expansion and other mechanical properties which are required for input to the analysis models.

Nanostructure characteristics of ferroics and bio-ferroics in relation to the design consideration of nano-sensing elements

NASA Astrophysics Data System (ADS)

Pal, Madhuparna

The shift of the epicenter in the field of science and technology to the nano-world has become evident over the past couple of decades with the emergence of areas likes nanoscience, nanotechnology, nano-biotechnology, etc. Though the size of the devices has decreased, the capability of devices has increased rendering it as 'multifunctional/smart' devices. However the design of smart devices using a single phase material has reached to its limit, hence to make further progress "smart materials" are required. Sensors/actuators are mostly fabricated with popular ferroic materials (ferroelectric/ ferromagnetic/ ferroelastic) or multiferroics (having more than one ferroic property). Multifunctionality can be the outcome of heterogeneous systems with cross-coupled properties, intrinsic as well as extrinsic, and hence modeling of smart materials with high figure of merit is also needed. Most ideas in smart sensing and actuation have been borrowed from the biological systems thus a step further is indeed to combine the engineering with the fundamental biological activities. Not only can we use multiferroic materials in artificial transplants, but we should also investigate ferroic activities in the biological samples. These fundamental issues, their possible solutions and their wide impact underlie the motivation of the current work in this thesis report. To achieve the ultimate goal, the steps outlined were followed: i. understanding the properties of sensing elements of inorganic and biomaterials at nanoscale level, ii. investigation of the multiferroicity, iii. modeling engineered material with better sensing capabilities iv. Finally exploiting the new concepts for device and biomedical applications. The findings of this thesis reports multiferroic behavior in a selected class of single crystals, thin films and bulk materials. Human nails and hair samples have been investigated for ferroelectricity and a comprehensive study concludes the presence of bio-ferroelectricity. Bio-ceramic for potential bone replacement has been characterized for its electrical properties and evidence has been given for its suitability. Initiation of modeling of material with high figure of merit for pyroelectric applications has been done which provides a platform to tailor its boundary conditions, interplay of interfaces to obtain meta-property. A broader impact of this thesis was to come forth with ideas to medical diagnostics and health monitoring combining and enhancing the understanding of multiferroics at macro to nano level, modeling of efficient heterogeneous material system, science of bio-materials and applications of bio-ceramics.

Hot-carrier trap-limited transport in switching chalcogenides

NASA Astrophysics Data System (ADS)

Piccinini, Enrico; Cappelli, Andrea; Buscemi, Fabrizio; Brunetti, Rossella; Ielmini, Daniele; Rudan, Massimo; Jacoboni, Carlo

2012-10-01

Chalcogenide materials have received great attention in the last decade owing to their application in new memory systems. Recently, phase-change memories have, in fact, reached the early stages of production. In spite of the industrial exploitation of such materials, the physical processes governing the switching mechanism are still debated. In this paper, we work out a complete and consistent model for transport in amorphous chalcogenide materials based on trap-limited conduction accompanied by carrier heating. A previous model is here extended to include position-dependent carrier concentration and field, consistently linked by the Poisson equation. The results of the new model reproduce the experimental electrical characteristics and their dependences on the device length and temperature. Furthermore, the model provides a sound physical interpretation of the switching phenomenon and is able to give an estimate of the threshold condition in terms of the material parameters, a piece of information of great technological interest.

Forward ultrasonic model validation using wavefield imaging methods

NASA Astrophysics Data System (ADS)

Blackshire, James L.

2018-04-01

The validation of forward ultrasonic wave propagation models in a complex titanium polycrystalline material system is accomplished using wavefield imaging methods. An innovative measurement approach is described that permits the visualization and quantitative evaluation of bulk elastic wave propagation and scattering behaviors in the titanium material for a typical focused immersion ultrasound measurement process. Results are provided for the determination and direct comparison of the ultrasonic beam's focal properties, mode-converted shear wave position and angle, and scattering and reflection from millimeter-sized microtexture regions (MTRs) within the titanium material. The approach and results are important with respect to understanding the root-cause backscatter signal responses generated in aerospace engine materials, where model-assisted methods are being used to understand the probabilistic nature of the backscatter signal content. Wavefield imaging methods are shown to be an effective means for corroborating and validating important forward model predictions in a direct manner using time- and spatially-resolved displacement field amplitude measurements.

Exemplar for simulation challenges: Large-deformation micromechanics of Sylgard 184/glass microballoon syntactic foams.

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

Brown, Judith Alice; Long, Kevin Nicholas

2018-05-01

Sylgard® 184/Glass Microballoon (GMB) potting material is currently used in many NW systems. Analysts need a macroscale constitutive model that can predict material behavior under complex loading and damage evolution. To address this need, ongoing modeling and experimental efforts have focused on study of damage evolution in these materials. Micromechanical finite element simulations that resolve individual GMB and matrix components promote discovery and better understanding of the material behavior. With these simulations, we can study the role of the GMB volume fraction, time-dependent damage, behavior under confined vs. unconfined compression, and the effects of partial damage. These simulations are challengingmore » and push the boundaries of capability even with the high performance computing tools available at Sandia. We summarize the major challenges and the current state of this modeling effort, as an exemplar of micromechanical modeling needs that can motivate advances in future computing efforts.« less

A new model for humic materials and their interactions with hydrophobic organic chemicals in soil-water or sediment-water systems

USGS Publications Warehouse

Wershaw, R. L.

1986-01-01

A generalized model of humic materials in soils and sediments, which is consistent with their observed properties, is presented. This model provides a means of understanding the interaction of hydrophobic pollutants with humic materials. In this model, it is proposed that the humic materials in soils and sediments consist of a number of different oligomers and simple compounds which result from the partial degradation of plant remains. These degradation products are stabilized by incorporation into humic aggregates bound together by weak bonding mechanisms, such as hydrogen bonding, pi bonding, and hydrophobic interactions. The resulting structures are similar to micelles or membranes, in which the interiors of the structures are hydrophobic and the exteriors are hydrophilic. Hydrophobic compounds will partition into the hydrophobic interiors of the humic micelles or "membrane-like" structures. ?? 1986.

Structural modeling for multicell composite rotor blades

NASA Technical Reports Server (NTRS)

Rehfield, Lawrence W.; Atilgan, Ali R.

1987-01-01

Composite material systems are currently good candidates for aerospace structures, primarily for the design flexibility they offer, i.e., it is possible to tailor the material and manufacturing approach to the application. A working definition of elastic or structural tailoring is the use of structural concept, fiber orientation, ply stacking sequence, and a blend of materials to achieve specific performance goals. In the design process, choices of materials and dimensions are made which produce specific response characteristics, and which permit the selected goals to be achieved. Common choices for tailoring goals are preventing instabilities or vibration resonances or enhancing damage tolerance. An essential, enabling factor in the design of tailored composite structures is structural modeling that accurately, but simply, characterizes response. The objective of this paper is to present a new multicell beam model for composite rotor blades and to validate predictions based on the new model by comparison with a finite element simulation in three benchmark static load cases.

In Depth Analysis of AVCOAT TPS Response to a Reentry Flow

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

Titov, E. V.; Kumar, Rakesh; Levin, D. A.

2011-05-20

Modeling of the high altitude portion of reentry vehicle trajectories with DSMC or statistical BGK solvers requires accurate evaluation of the boundary conditions at the ablating TPS surface. Presented in this article is a model which takes into account the complex ablation physics including the production of pyrolysis gases, and chemistry at the TPS surface. Since the ablation process is time dependent the modeling of the material response to the high energy reentry flow starts with the solution of the rarefied flow over the vehicle and then loosely couples with the material response. The objective of the present work ismore » to carry out conjugate thermal analysis by weakly coupling a flow solver to a material thermal response model. The latter model solves the one dimensional heat conduction equation accounting for the pyrolysis process that takes place in the reaction zone of an ablative thermal protection system (TPS) material. An estimate of the temperature range within which the pyrolysis reaction (decomposition and volatilization) takes place is obtained from Ref. [1]. The pyrolysis reaction results in the formation of char and the release of gases through the porous charred material. These gases remove additional amount of heat as they pass through the material, thus cooling the material (the process known as transpiration cooling). In the present work, we incorporate the transpiration cooling model in the material thermal response code in addition to the pyrolysis model. The flow in the boundary layer and in the vicinity of the TPS material is in the transitional flow regime. Therefore, we use a previously validated statistical BGK method to model the flow physics in the vicinity of the micro-cracks, since the BGK method allows simulations of flow at pressures higher than can be computed using DSMC.« less

Solar heating and cooling technical data and systems analysis

NASA Technical Reports Server (NTRS)

Christensen, D. L.

1976-01-01

The accomplishments of a project to study solar heating and air conditioning are outlined. Presentation materials (data packages, slides, charts, and visual aids) were developed. Bibliographies and source materials on materials and coatings, solar water heaters, systems analysis computer models, solar collectors and solar projects were developed. Detailed MIRADS computer formats for primary data parameters were developed and updated. The following data were included: climatic, architectural, topography, heating and cooling equipment, thermal loads, and economics. Data sources in each of these areas were identified as well as solar radiation data stations and instruments.

Development of Thermal Protection Materials for Future Mars Entry, Descent and Landing Systems

NASA Technical Reports Server (NTRS)

Cassell, Alan M.; Beck, Robin A. S.; Arnold, James O.; Hwang, Helen; Wright, Michael J.; Szalai, Christine E.; Blosser, Max; Poteet, Carl C.

2010-01-01

Entry Systems will play a crucial role as NASA develops the technologies required for Human Mars Exploration. The Exploration Technology Development Program Office established the Entry, Descent and Landing (EDL) Technology Development Project to develop Thermal Protection System (TPS) materials for insertion into future Mars Entry Systems. An assessment of current entry system technologies identified significant opportunity to improve the current state of the art in thermal protection materials in order to enable landing of heavy mass (40 mT) payloads. To accomplish this goal, the EDL Project has outlined a framework to define, develop and model the thermal protection system material concepts required to allow for the human exploration of Mars via aerocapture followed by entry. Two primary classes of ablative materials are being developed: rigid and flexible. The rigid ablatives will be applied to the acreage of a 10x30 m rigid mid L/D Aeroshell to endure the dual pulse heating (peak approx.500 W/sq cm). Likewise, flexible ablative materials are being developed for 20-30 m diameter deployable aerodynamic decelerator entry systems that could endure dual pulse heating (peak aprrox.120 W/sq cm). A technology Roadmap is presented that will be used for facilitating the maturation of both the rigid and flexible ablative materials through application of decision metrics (requirements, key performance parameters, TRL definitions, and evaluation criteria) used to assess and advance the various candidate TPS material technologies.

Modeling Xenon Purification Systems in a Laser Inertial Fusion Engine

NASA Astrophysics Data System (ADS)

Hopkins, Ann; Gentile, Charles

2011-10-01

A Laser Inertial Fusion Engine (LIFE) is a proposed method to employ fusion energy to produce electricity for consumers. However, before it can be built and used as such, each aspect of a LIFE power plant must first be meticulously planned. We are in the process of developing and perfecting models for an exhaust processing and fuel recovery system. Such a system is especially essential because it must be able to recapture and purify expensive materials involved in the reaction so they may be reused. One such material is xenon, which is to be used as an intervention gas in the target chamber. Using Aspen HYSYS, we have modeled several subsystems for exhaust processing, including a subsystem for xenon recovery and purification. After removing hydrogen isotopes using lithium bubblers, we propose to use cryogenic distillation to purify the xenon from remaining contaminants. Aspen HYSYS allows us to analyze predicted flow rates, temperatures, pressures, and compositions within almost all areas of the xenon purification system. Through use of Aspen models, we hope to establish that we can use xenon in LIFE efficiently and in a practical manner.

Technology Investments in the NASA Entry Systems Modeling Project

NASA Technical Reports Server (NTRS)

Barnhardt, Michael; Wright, Michael; Hughes, Monica

2017-01-01

The Entry Systems Modeling (ESM) technology development project, initiated in 2012 under NASAs Game Changing Development (GCD) Program, is engaged in maturation of fundamental research developing aerosciences, materials, and integrated systems products for entry, descent, and landing(EDL)technologies [1]. To date, the ESM project has published over 200 papers in these areas, comprising the bulk of NASAs research program for EDL modeling. This presentation will provide an overview of the projects successes and challenges, and an assessment of future investments in EDL modeling and simulation relevant to NASAs mission

Designing Radiation Resistance in Materials for Fusion Energy

NASA Astrophysics Data System (ADS)

Zinkle, S. J.; Snead, L. L.

2014-07-01

Proposed fusion and advanced (Generation IV) fission energy systems require high-performance materials capable of satisfactory operation up to neutron damage levels approaching 200 atomic displacements per atom with large amounts of transmutant hydrogen and helium isotopes. After a brief overview of fusion reactor concepts and radiation effects phenomena in structural and functional (nonstructural) materials, three fundamental options for designing radiation resistance are outlined: Utilize matrix phases with inherent radiation tolerance, select materials in which vacancies are immobile at the design operating temperatures, or engineer materials with high sink densities for point defect recombination. Environmental and safety considerations impose several additional restrictions on potential materials systems, but reduced-activation ferritic/martensitic steels (including thermomechanically treated and oxide dispersion-strengthened options) and silicon carbide ceramic composites emerge as robust structural materials options. Materials modeling (including computational thermodynamics) and advanced manufacturing methods are poised to exert a major impact in the next ten years.

Knowledge Integration to Make Decisions About Complex Systems: Sustainability of Energy Production from Agriculture

ScienceCinema

Danuso, Francesco

2017-12-22

A major bottleneck for improving the governance of complex systems, rely on our ability to integrate different forms of knowledge into a decision support system (DSS). Preliminary aspects are the classification of different types of knowledge (a priori or general, a posteriori or specific, with uncertainty, numerical, textual, algorithmic, complete/incomplete, etc.), the definition of ontologies for knowledge management and the availability of proper tools like continuous simulation models, event driven models, statistical approaches, computational methods (neural networks, evolutionary optimization, rule based systems etc.) and procedure for textual documentation. Following these views at University of Udine, a computer language (SEMoLa, Simple, Easy Modelling Language) for knowledge integration has been developed.  SEMoLa can handle models, data, metadata and textual knowledge; it implements and extends the system dynamics ontology (Forrester, 1968; Jørgensen, 1994) in which systems are modelled by the concepts of material, group, state, rate, parameter, internal and external events and driving variables. As an example, a SEMoLa model to improve management and sustainability (economical, energetic, environmental) of the agricultural farms is presented. The model (X-Farm) simulates a farm in which cereal and forage yield, oil seeds, milk, calves and wastes can be sold or reused. X-Farm is composed by integrated modules describing fields (crop and soil), feeds and materials storage, machinery management, manpower  management, animal husbandry, economic and energetic balances, seed oil extraction, manure and wastes management, biogas production from animal wastes and biomasses.

Modeling and simulation of the solar concentrator in photovoltaic systems through the application of a new BRDF function model

NASA Astrophysics Data System (ADS)

Plachta, Kamil

2016-04-01

The paper presents a new algorithm that uses a combination of two models of BRDF functions: Torrance-Sparrow model and HTSG model. The knowledge of technical parameters of a surface is especially useful in the construction of the solar concentrator. The concentrator directs the reflected solar radiation on the surface of photovoltaic panels, increasing the amount of incident radiance. The software applying algorithm allows to calculate surface parameters of the solar concentrator. Performed simulation showing the share of diffuse component and directional component in reflected stream for surfaces made from particular materials. The impact of share of each component in reflected stream on the efficiency of the solar concentrator and photovoltaic surface has also been described. Subsequently, simulation change the value of voltage, current and power output of monocrystalline photovoltaic panels installed in a solar concentrator system has been made for selected surface of materials solar concentrator.

Reliability Analysis of the Space Station Freedom Electrical Power System

DTIC Science & Technology

1989-08-01

Cleveland, Ohio, who assisted in obtaining related research materials and provided feedback on our efforts to produce a dynamic analysis tool useful to...System software that we used to do our analysis of the electrical power system. Thanks are due to Dr. Vira Chankong, my thesis advisor, for his...a frequency duration analysis . Using a transition rate matrix with a model of the photovoltaic and solar dynamic systems, they have one model that

Materials integrity in microsystems: a framework for a petascale predictive-science-based multiscale modeling and simulation system

NASA Astrophysics Data System (ADS)

To, Albert C.; Liu, Wing Kam; Olson, Gregory B.; Belytschko, Ted; Chen, Wei; Shephard, Mark S.; Chung, Yip-Wah; Ghanem, Roger; Voorhees, Peter W.; Seidman, David N.; Wolverton, Chris; Chen, J. S.; Moran, Brian; Freeman, Arthur J.; Tian, Rong; Luo, Xiaojuan; Lautenschlager, Eric; Challoner, A. Dorian

2008-09-01

Microsystems have become an integral part of our lives and can be found in homeland security, medical science, aerospace applications and beyond. Many critical microsystem applications are in harsh environments, in which long-term reliability needs to be guaranteed and repair is not feasible. For example, gyroscope microsystems on satellites need to function for over 20 years under severe radiation, thermal cycling, and shock loading. Hence a predictive-science-based, verified and validated computational models and algorithms to predict the performance and materials integrity of microsystems in these situations is needed. Confidence in these predictions is improved by quantifying uncertainties and approximation errors. With no full system testing and limited sub-system testings, petascale computing is certainly necessary to span both time and space scales and to reduce the uncertainty in the prediction of long-term reliability. This paper presents the necessary steps to develop predictive-science-based multiscale modeling and simulation system. The development of this system will be focused on the prediction of the long-term performance of a gyroscope microsystem. The environmental effects to be considered include radiation, thermo-mechanical cycling and shock. Since there will be many material performance issues, attention is restricted to creep resulting from thermal aging and radiation-enhanced mass diffusion, material instability due to radiation and thermo-mechanical cycling and damage and fracture due to shock. To meet these challenges, we aim to develop an integrated multiscale software analysis system that spans the length scales from the atomistic scale to the scale of the device. The proposed software system will include molecular mechanics, phase field evolution, micromechanics and continuum mechanics software, and the state-of-the-art model identification strategies where atomistic properties are calibrated by quantum calculations. We aim to predict the long-term (in excess of 20 years) integrity of the resonator, electrode base, multilayer metallic bonding pads, and vacuum seals in a prescribed mission. Although multiscale simulations are efficient in the sense that they focus the most computationally intensive models and methods on only the portions of the space time domain needed, the execution of the multiscale simulations associated with evaluating materials and device integrity for aerospace microsystems will require the application of petascale computing. A component-based software strategy will be used in the development of our massively parallel multiscale simulation system. This approach will allow us to take full advantage of existing single scale modeling components. An extensive, pervasive thrust in the software system development is verification, validation, and uncertainty quantification (UQ). Each component and the integrated software system need to be carefully verified. An UQ methodology that determines the quality of predictive information available from experimental measurements and packages the information in a form suitable for UQ at various scales needs to be developed. Experiments to validate the model at the nanoscale, microscale, and macroscale are proposed. The development of a petascale predictive-science-based multiscale modeling and simulation system will advance the field of predictive multiscale science so that it can be used to reliably analyze problems of unprecedented complexity, where limited testing resources can be adequately replaced by petascale computational power, advanced verification, validation, and UQ methodologies.

Organic Solid Matter as a Coloring Agent in Outer Solar System Bodies

NASA Technical Reports Server (NTRS)

Cruikshank, D. P.; DalleOre, C. M.; Roush, T. L.; Khare, B. N.; Fonda, Mark (Technical Monitor)

2002-01-01

Small bodies in the outer Solar System OSS, exhibit a range of color, or slope of the reflectance in the photovisual spectral region, ranging from neutral to very red, sometimes with and sometimes without distinct absorption bands. These objects range in geometric albedo from 0.03 to 1.0, with the higher albedo objects typically showing clear evidence of water ice. Water ice has also been found in a few objects with albedo 0. 1 or less. We explore here the identification of the material or materials that color these icy and non-icy surfaces through scattering models that incorporate minerals, meteoritic material, and organic solids (tholins) produced ID the laboratory by energy deposition in ices and gases. These models must match not only the color in the photovisual region, but the spectral reflectance properties throughout the near-infrared. Among some classes of objects, such as Kuiper Belt objects, the coloring agent may be a single material that is present in greater or lesser abundance, thus accounting for the range in color from neutral to very red. This may also apply to the Centaur objects, the Jovian Trojans, and the outer-main belt asteroids, each taken as a separate class. If so, each class may be colored to varying degrees by a different material, or they all might be colored by a common material that is widespread throughout the OSS, from 3 to 50 AU, and beyond. In this paper, we model the reflectances of "Kuiper Belt objects, Centaurs, Trojans, outer ARAB asteroids, and planetary satellites. Our models show that the reddest surfaces cannot be colored by minerals or meteoritic materials, but can be matched throughout the photovisual and near-infrared by organic solids, specifically certain tholins.

The Structure and Properties of Silica Glass Nanostructures using Novel Computational Systems

NASA Astrophysics Data System (ADS)

Doblack, Benjamin N.

The structure and properties of silica glass nanostructures are examined using computational methods in this work. Standard synthesis methods of silica and its associated material properties are first discussed in brief. A review of prior experiments on this amorphous material is also presented. Background and methodology for the simulation of mechanical tests on amorphous bulk silica and nanostructures are later presented. A new computational system for the accurate and fast simulation of silica glass is also presented, using an appropriate interatomic potential for this material within the open-source molecular dynamics computer program LAMMPS. This alternative computational method uses modern graphics processors, Nvidia CUDA technology and specialized scientific codes to overcome processing speed barriers common to traditional computing methods. In conjunction with a virtual reality system used to model select materials, this enhancement allows the addition of accelerated molecular dynamics simulation capability. The motivation is to provide a novel research environment which simultaneously allows visualization, simulation, modeling and analysis. The research goal of this project is to investigate the structure and size dependent mechanical properties of silica glass nanohelical structures under tensile MD conditions using the innovative computational system. Specifically, silica nanoribbons and nanosprings are evaluated which revealed unique size dependent elastic moduli when compared to the bulk material. For the nanoribbons, the tensile behavior differed widely between the models simulated, with distinct characteristic extended elastic regions. In the case of the nanosprings simulated, more clear trends are observed. In particular, larger nanospring wire cross-sectional radii (r) lead to larger Young's moduli, while larger helical diameters (2R) resulted in smaller Young's moduli. Structural transformations and theoretical models are also analyzed to identify possible factors which might affect the mechanical response of silica nanostructures under tension. The work presented outlines an innovative simulation methodology, and discusses how results can be validated against prior experimental and simulation findings. The ultimate goal is to develop new computational methods for the study of nanostructures which will make the field of materials science more accessible, cost effective and efficient.

Modeling the reversible, diffusive sink effect in response to transient contaminant sources.

PubMed

Zhao, D; Little, J C; Hodgson, A T

2002-09-01

A physically based diffusion model is used to evaluate the sink effect of diffusion-controlled indoor materials and to predict the transient contaminant concentration in indoor air in response to several time-varying contaminant sources. For simplicity, it is assumed the predominant indoor material is a homogeneous slab, initially free of contaminant, and the air within the room is well mixed. The model enables transient volatile organic compound (VOC) concentrations to be predicted based on the material/air partition coefficient (K) and the material-phase diffusion coefficient (D) of the sink. Model predictions are made for three scenarios, each mimicking a realistic situation in a building. Styrene, phenol, and naphthalene are used as representative VOCs. A styrene butadiene rubber (SBR) backed carpet, vinyl flooring (VF), and a polyurethane foam (PUF) carpet cushion are considered as typical indoor sinks. In scenarios involving a sinusoidal VOC input and a double exponential decaying input, the model predicts the sink has a modest impact for SBR/styrene, but the effect increases for VF/phenol and PUF/naphthalene. In contrast, for an episodic chemical spill, SBR is predicted to reduce the peak styrene concentration considerably. A parametric study reveals for systems involving a large equilibrium constant (K), the kinetic constant (D) will govern the shape of the resulting gasphase concentration profile. On the other hand, for systems with a relaxed mass transfer resistance, K will dominate the profile.

Mechanically triggered heterolytic unzipping of a low-ceiling-temperature polymer

NASA Astrophysics Data System (ADS)

Diesendruck, Charles E.; Peterson, Gregory I.; Kulik, Heather J.; Kaitz, Joshua A.; Mar, Brendan D.; May, Preston A.; White, Scott R.; Martínez, Todd J.; Boydston, Andrew J.; Moore, Jeffrey S.

2014-07-01

Biological systems rely on recyclable materials resources such as amino acids, carbohydrates and nucleic acids. When biomaterials are damaged as a result of aging or stress, tissues undergo repair by a depolymerization-repolymerization sequence of remodelling. Integration of this concept into synthetic materials systems may lead to devices with extended lifetimes. Here, we show that a metastable polymer, end-capped poly(o-phthalaldehyde), undergoes mechanically initiated depolymerization to revert the material to monomers. Trapping experiments and steered molecular dynamics simulations are consistent with a heterolytic scission mechanism. The obtained monomer was repolymerized by a chemical initiator, effectively completing a depolymerization-repolymerization cycle. By emulating remodelling of biomaterials, this model system suggests the possibility of smart materials where aging or mechanical damage triggers depolymerization, and orthogonal conditions regenerate the polymer when and where necessary.

Computational Intelligence‐Assisted Understanding of Nature‐Inspired Superhydrophobic Behavior

PubMed Central

Zhang, Xia; Ding, Bei; Dixon, Sebastian C.

2017-01-01

Abstract In recent years, state‐of‐the‐art computational modeling of physical and chemical systems has shown itself to be an invaluable resource in the prediction of the properties and behavior of functional materials. However, construction of a useful computational model for novel systems in both academic and industrial contexts often requires a great depth of physicochemical theory and/or a wealth of empirical data, and a shortage in the availability of either frustrates the modeling process. In this work, computational intelligence is instead used, including artificial neural networks and evolutionary computation, to enhance our understanding of nature‐inspired superhydrophobic behavior. The relationships between experimental parameters (water droplet volume, weight percentage of nanoparticles used in the synthesis of the polymer composite, and distance separating the superhydrophobic surface and the pendant water droplet in adhesive force measurements) and multiple objectives (water droplet contact angle, sliding angle, and adhesive force) are built and weighted. The obtained optimal parameters are consistent with the experimental observations. This new approach to materials modeling has great potential to be applied more generally to aid design, fabrication, and optimization for myriad functional materials. PMID:29375975

Computational Intelligence-Assisted Understanding of Nature-Inspired Superhydrophobic Behavior.

PubMed

Zhang, Xia; Ding, Bei; Cheng, Ran; Dixon, Sebastian C; Lu, Yao

2018-01-01

In recent years, state-of-the-art computational modeling of physical and chemical systems has shown itself to be an invaluable resource in the prediction of the properties and behavior of functional materials. However, construction of a useful computational model for novel systems in both academic and industrial contexts often requires a great depth of physicochemical theory and/or a wealth of empirical data, and a shortage in the availability of either frustrates the modeling process. In this work, computational intelligence is instead used, including artificial neural networks and evolutionary computation, to enhance our understanding of nature-inspired superhydrophobic behavior. The relationships between experimental parameters (water droplet volume, weight percentage of nanoparticles used in the synthesis of the polymer composite, and distance separating the superhydrophobic surface and the pendant water droplet in adhesive force measurements) and multiple objectives (water droplet contact angle, sliding angle, and adhesive force) are built and weighted. The obtained optimal parameters are consistent with the experimental observations. This new approach to materials modeling has great potential to be applied more generally to aid design, fabrication, and optimization for myriad functional materials.

Material Modeling of Space Shuttle Leading Edge and External Tank Materials For Use in the Columbia Accident Investigation

NASA Technical Reports Server (NTRS)

Carney, Kelly; Melis, Matthew; Fasanella, Edwin L.; Lyle, Karen H.; Gabrys, Jonathan

2004-01-01

Upon the commencement of the analytical effort to characterize the impact dynamics and damage of the Space Shuttle Columbia leading edge due to External Tank insulating foam, the necessity of creating analytical descriptions of these materials became evident. To that end, material models were developed of the leading edge thermal protection system, Reinforced Carbon Carbon (RCC), and a low density polyurethane foam, BX-250. Challenges in modeling the RCC include its extreme brittleness, the differing behavior in compression and tension, and the anisotropic fabric layup. These effects were successfully included in LS-DYNA Material Model 58, *MAT_LAMINATED_ COMPOSITE_ FABRIC. The differing compression and tension behavior was modeled using the available damage parameters. Each fabric layer was given an integration point in the shell element, and was allowed to fail independently. Comparisons were made to static test data and coupon ballistic impact tests before being utilized in the full scale analysis. The foam's properties were typical of elastic automotive foams; and LS-DYNA Material Model 83, *MAT_FU_CHANG_FOAM, was successfully used to model its behavior. Material parameters defined included strain rate dependent stress-strain curves for both loading and un-loading, and for both compression and tension. This model was formulated with static test data and strain rate dependent test data, and was compared to ballistic impact tests on load-cell instrumented aluminum plates. These models were subsequently utilized in analysis of the Shuttle leading edge full scale ballistic impact tests, and are currently being used in the Return to Flight Space Shuttle re-certification effort.

DECONTAMINATION AND BENEFICIAL USE OF DREDGED MATERIALS.

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

STERN, E.A.; LODGE, J.; JONES, K.W.

2000-12-03

Our group is leading a large-sale demonstration of dredged material decontamination technologies for the New York/New Jersey Harbor. The goal of the project is to assemble a complete system for economic transformation of contaminated dredged material into an environmentally-benign material used in the manufacture of a variety of beneficial use products. This requires the integration of scientific, engineering, business, and policy issues on matters that include basic knowledge of sediment properties, contaminant distribution visualization, sediment toxicity, dredging and dewatering techniques, decontamination technologies, and product manufacturing technologies and marketing. A summary of the present status of the system demonstrations including themore » use of both existing and new manufacturing facilities is given here. These decontamination systems should serve as a model for use in dredged material management plans of regions other than NY/NJ Harbor, such as Long Island Sound, where new approaches to the handling of contaminated sediments are desirable.« less

Deciphering chemical order/disorder and material properties at the single-atom level.

PubMed

Yang, Yongsoo; Chen, Chien-Chun; Scott, M C; Ophus, Colin; Xu, Rui; Pryor, Alan; Wu, Li; Sun, Fan; Theis, Wolfgang; Zhou, Jihan; Eisenbach, Markus; Kent, Paul R C; Sabirianov, Renat F; Zeng, Hao; Ercius, Peter; Miao, Jianwei

2017-02-01

Perfect crystals are rare in nature. Real materials often contain crystal defects and chemical order/disorder such as grain boundaries, dislocations, interfaces, surface reconstructions and point defects. Such disruption in periodicity strongly affects material properties and functionality. Despite rapid development of quantitative material characterization methods, correlating three-dimensional (3D) atomic arrangements of chemical order/disorder and crystal defects with material properties remains a challenge. On a parallel front, quantum mechanics calculations such as density functional theory (DFT) have progressed from the modelling of ideal bulk systems to modelling 'real' materials with dopants, dislocations, grain boundaries and interfaces; but these calculations rely heavily on average atomic models extracted from crystallography. To improve the predictive power of first-principles calculations, there is a pressing need to use atomic coordinates of real systems beyond average crystallographic measurements. Here we determine the 3D coordinates of 6,569 iron and 16,627 platinum atoms in an iron-platinum nanoparticle, and correlate chemical order/disorder and crystal defects with material properties at the single-atom level. We identify rich structural variety with unprecedented 3D detail including atomic composition, grain boundaries, anti-phase boundaries, anti-site point defects and swap defects. We show that the experimentally measured coordinates and chemical species with 22 picometre precision can be used as direct input for DFT calculations of material properties such as atomic spin and orbital magnetic moments and local magnetocrystalline anisotropy. This work combines 3D atomic structure determination of crystal defects with DFT calculations, which is expected to advance our understanding of structure-property relationships at the fundamental level.

Nebula Scale Mixing Between Non-Carbonaceous and Carbonaceous Chondrite Reservoirs: Testing the Grand Tack Model with Almahata Sitta Stones

NASA Technical Reports Server (NTRS)

Yin, Q.-Z.; Sanborn, M. E.; Goodrich, C. A.; Zolensky, M.; Fioretti, A. M.; Shaddad, M.; Kohl, I. E.; Young, E. D.

2018-01-01

There is an increasing number of Cr-O-Ti isotope studies that show that solar system materials are divided into two main populations, one carbonaceous chondrite (CC)-like and the other is non-carbonaceous (NCC)-like, with minimal mixing between them attributed to a gap opened in the propoplanetary disk due to Jupiter's formation. The Grand Tack model suggests that there should be a particular time in the disk history when this gap is breached and ensuring a subsequent large-scale mixing between S- and C-type asteroids (inner solar system and outer solar system materials), an idea supported by our recent work on chondrule (Delta)17O-(epsilon)54Cr isotope systematics.

3D finite element modeling of sliding wear

NASA Astrophysics Data System (ADS)

Buentello Hernandez, Rodolfo G.

Wear is defined as "the removal of material volume through some mechanical process between two surfaces". There are many mechanical situations that can induce wear and each can involve many wear mechanisms. This research focuses on the mechanical wear due to dry sliding between two surfaces. Currently there is a need to identify and compare materials that would endure sliding wear under severe conditions such as high velocities. The high costs associated with the field experimentation of systems subject to high-speed sliding, has prevented the collection of the necessary data required to fully characterize this phenomena. Simulating wear through Finite Elements (FE) would enable its prediction under different scenarios and would reduce experimentation costs. In the aerospace, automotive and weapon industries such a model can aid in material selection, design and/or testing of systems subjected to wear in bearings, gears, brakes, gun barrels, slippers, locomotive wheels, or even rocket test tracks. The 3D wear model presented in this dissertation allows one to reasonably predict high-speed sliding mechanical wear between two materials. The model predictions are reasonable, when compared against those measured on a sled slipper traveling over the Holloman High Speed Tests Track. This slipper traveled a distance of 5,816 meters in 8.14 seconds and reached a maximum velocity of 1,530 m/s.

Robust identification of polyethylene terephthalate (PET) plastics through Bayesian decision.

PubMed

Zulkifley, Mohd Asyraf; Mustafa, Mohd Marzuki; Hussain, Aini; Mustapha, Aouache; Ramli, Suzaimah

2014-01-01

Recycling is one of the most efficient methods for environmental friendly waste management. Among municipal wastes, plastics are the most common material that can be easily recycled and polyethylene terephthalate (PET) is one of its major types. PET material is used in consumer goods packaging such as drinking bottles, toiletry containers, food packaging and many more. Usually, a recycling process is tailored to a specific material for optimal purification and decontamination to obtain high grade recyclable material. The quantity and quality of the sorting process are limited by the capacity of human workers that suffer from fatigue and boredom. Several automated sorting systems have been proposed in the literature that include using chemical, proximity and vision sensors. The main advantages of vision based sensors are its environmentally friendly approach, non-intrusive detection and capability of high throughput. However, the existing methods rely heavily on deterministic approaches that make them less accurate as the variations in PET plastic waste appearance are too high. We proposed a probabilistic approach of modeling the PET material by analyzing the reflection region and its surrounding. Three parameters are modeled by Gaussian and exponential distributions: color, size and distance of the reflection region. The final classification is made through a supervised training method of likelihood ratio test. The main novelty of the proposed method is the probabilistic approach in integrating various PET material signatures that are contaminated by stains under constant lighting changes. The system is evaluated by using four performance metrics: precision, recall, accuracy and error. Our system performed the best in all evaluation metrics compared to the benchmark methods. The system can be further improved by fusing all neighborhood information in decision making and by implementing the system in a graphics processing unit for faster processing speed.

Robust Identification of Polyethylene Terephthalate (PET) Plastics through Bayesian Decision

PubMed Central

Zulkifley, Mohd Asyraf; Mustafa, Mohd Marzuki; Hussain, Aini; Mustapha, Aouache; Ramli, Suzaimah

2014-01-01

Recycling is one of the most efficient methods for environmental friendly waste management. Among municipal wastes, plastics are the most common material that can be easily recycled and polyethylene terephthalate (PET) is one of its major types. PET material is used in consumer goods packaging such as drinking bottles, toiletry containers, food packaging and many more. Usually, a recycling process is tailored to a specific material for optimal purification and decontamination to obtain high grade recyclable material. The quantity and quality of the sorting process are limited by the capacity of human workers that suffer from fatigue and boredom. Several automated sorting systems have been proposed in the literature that include using chemical, proximity and vision sensors. The main advantages of vision based sensors are its environmentally friendly approach, non-intrusive detection and capability of high throughput. However, the existing methods rely heavily on deterministic approaches that make them less accurate as the variations in PET plastic waste appearance are too high. We proposed a probabilistic approach of modeling the PET material by analyzing the reflection region and its surrounding. Three parameters are modeled by Gaussian and exponential distributions: color, size and distance of the reflection region. The final classification is made through a supervised training method of likelihood ratio test. The main novelty of the proposed method is the probabilistic approach in integrating various PET material signatures that are contaminated by stains under constant lighting changes. The system is evaluated by using four performance metrics: precision, recall, accuracy and error. Our system performed the best in all evaluation metrics compared to the benchmark methods. The system can be further improved by fusing all neighborhood information in decision making and by implementing the system in a graphics processing unit for faster processing speed. PMID:25485630

Teaching Materials and Methods.

ERIC Educational Resources Information Center

Physiologist, 1982

1982-01-01

Twelve abstracts of papers presented at the 33rd Annual Fall Meeting of the American Physiological Society are listed, focusing on teaching materials/methods. Topics, among others, include trends in physiology laboratory programs, cardiovascular system model, cardiovascular computer simulation with didactic feedback, and computer generated figures…

Internet's impact on publishing

NASA Astrophysics Data System (ADS)

Beretta, Giordano B.

1997-04-01

In 1990, the first monochrome print-on-demand (POD) systems wee successfully brought to market. Subsequent color versions have been less successful, in my view mostly because they require a different workflow than traditional systems and the highly skilled specialists have not been trained. This hypothesis is based on the observation that direct-to-plate systems for short run printing, which do not require a new workflow, are quite successful in the market place. The internet and the World Wide Web are the enabling technologies that are fostering a new print model that is very likely to replace color POD before the latter can establish itself. In this model the consumers locate the material they desire from a contents provider, pay through a digital cash clearinghouse, and print the material at their own cost on their local printer. All the basic technologies for this model are in place; the main challenge is to make the workflow sufficiently robust for individual use.

Probabilistic Material Strength Degradation Model for Inconel 718 Components Subjected to High Temperature, High-Cycle and Low-Cycle Mechanical Fatigue, Creep and Thermal Fatigue Effects

NASA Technical Reports Server (NTRS)

Bast, Callie C.; Boyce, Lola

1995-01-01

The development of methodology for a probabilistic material strength degradation is described. The probabilistic model, in the form of a postulated randomized multifactor equation, provides for quantification of uncertainty in the lifetime material strength of aerospace propulsion system components subjected to a number of diverse random effects. This model is embodied in the computer program entitled PROMISS, which can include up to eighteen different effects. Presently, the model includes five effects that typically reduce lifetime strength: high temperature, high-cycle mechanical fatigue, low-cycle mechanical fatigue, creep and thermal fatigue. Results, in the form of cumulative distribution functions, illustrated the sensitivity of lifetime strength to any current value of an effect. In addition, verification studies comparing predictions of high-cycle mechanical fatigue and high temperature effects with experiments are presented. Results from this limited verification study strongly supported that material degradation can be represented by randomized multifactor interaction models.

A parametric model order reduction technique for poroelastic finite element models.

PubMed

Lappano, Ettore; Polanz, Markus; Desmet, Wim; Mundo, Domenico

2017-10-01

This research presents a parametric model order reduction approach for vibro-acoustic problems in the frequency domain of systems containing poroelastic materials (PEM). The method is applied to the Finite Element (FE) discretization of the weak u-p integral formulation based on the Biot-Allard theory and makes use of reduced basis (RB) methods typically employed for parametric problems. The parametric reduction is obtained rewriting the Biot-Allard FE equations for poroelastic materials using an affine representation of the frequency (therefore allowing for RB methods) and projecting the frequency-dependent PEM system on a global reduced order basis generated with the proper orthogonal decomposition instead of standard modal approaches. This has proven to be better suited to describe the nonlinear frequency dependence and the strong coupling introduced by damping. The methodology presented is tested on two three-dimensional systems: in the first experiment, the surface impedance of a PEM layer sample is calculated and compared with results of the literature; in the second, the reduced order model of a multilayer system coupled to an air cavity is assessed and the results are compared to those of the reference FE model.

Augmented halal food traceability system: analysis and design using UML

NASA Astrophysics Data System (ADS)

Usman, Y. V.; Fauzi, A. M.; Irawadi, T. T.; Djatna, T.

2018-04-01

Augmented halal food traceability is expanding the range of halal traceability in food supply chain where currently only available for tracing from the source of raw material to the industrial warehouse or inbound logistic. The halal traceability system must be developed in the integrated form that includes inbound and outbound logistics. The objective of this study was to develop a reliable initial model of integrated traceability system of halal food supply chain. The method was based on unified modeling language (UML) such as use case, sequence, and business process diagram. A goal programming model was formulated considering two objective functions which include (1) minimization of risk of halal traceability failures happened potentially during outbound logistics activities and (2) maximization of quality of halal product information. The result indicates the supply of material is the most important point to be considered in minimizing the risk of failure of halal food traceability system whereas no risk observed in manufacturing and distribution.

Characterization of the harvesting capabilities of an ionic polymer metal composite device

NASA Astrophysics Data System (ADS)

Brufau-Penella, J.; Puig-Vidal, M.; Giannone, P.; Graziani, S.; Strazzeri, S.

2008-02-01

Harvesting systems capable of transforming dusty environmental energy into electrical energy have aroused considerable interest in the last two decades. Several research works have focused on the transformation of mechanical environmental vibrations into electrical energy. Most of the research activity refers to classic piezoelectric ceramic materials, but more recently piezoelectric polymer materials have been considered. In this paper, a novel point of view regarding harvesting systems is proposed: using ionic polymer metal composites (IPMCs) as generating materials. The goal of this paper is the development of a model able to predict the energy harvesting capabilities of an IPMC material working in air. The model is developed by using the vibration transmission theory of an Euler-Bernoulli cantilever IPMC beam. The IPMC is considered to work in its linear elastic region with a viscous damping contribution ranging from 0.1 to 100 Hz. An identification process based on experimental measurements performed on a Nafion® 117 membrane is used to estimate the material parameters. The model validation shows a good agreement between simulated and experimental results. The model is used to predict the optimal working region and the optimal geometrical parameters for the maximum power generation capacity of a specific membrane. The model takes into account two restrictions. The first is due to the beam theory, which imposes a maximum ratio of 0.5 between the cantilever width and length. The second restriction is to force the cantilever to oscillate with a specific strain; in this paper a 0.3% strain is considered. By considering these two assumptions as constraints on the model, it is seen that IPMC materials could be used as low-power generators in a low-frequency region. The optimal dimensions for the Nafion® 117 membrane are length = 12 cm and width = 6.2 cm, and the electric power generation is 3 nW at a vibrating frequency of 7.09 rad s-1. IPMC materials can sustain big yield strains, so by increasing the strain allowed on the material the power will increase dramatically, the expected values being up to a few microwatts.

Symbiotic stars

NASA Technical Reports Server (NTRS)

Kafatos, M.; Michalitsianos, A. G.

1984-01-01

The physical characteristics of symbiotic star systems are discussed, based on a review of recent observational data. A model of a symbiotic star system is presented which illustrates how a cool red-giant star is embedded in a nebula whose atoms are ionized by the energetic radiation from its hot compact companion. UV outbursts from symbiotic systems are explained by two principal models: an accretion-disk-outburst model which describes how material expelled from the tenuous envelope of the red giant forms an inwardly-spiralling disk around the hot companion, and a thermonuclear-outburst model in which the companion is specifically a white dwarf which superheats the material expelled from the red giant to the point where thermonuclear reactions occur and radiation is emitted. It is suspected that the evolutionary course of binary systems is predetermined by the initial mass and angular momentum of the gas cloud within which binary stars are born. Since red giants and Mira variables are thought to be stars with a mass of one or two solar mass, it is believed that the original cloud from which a symbiotic system is formed can consist of no more than a few solar masses of gas.

Recommending Education Materials for Diabetic Questions Using Information Retrieval Approaches

PubMed Central

Wang, Yanshan; Shen, Feichen; Liu, Sijia; Rastegar-Mojarad, Majid; Wang, Liwei

2017-01-01

Background Self-management is crucial to diabetes care and providing expert-vetted content for answering patients’ questions is crucial in facilitating patient self-management. Objective The aim is to investigate the use of information retrieval techniques in recommending patient education materials for diabetic questions of patients. Methods We compared two retrieval algorithms, one based on Latent Dirichlet Allocation topic modeling (topic modeling-based model) and one based on semantic group (semantic group-based model), with the baseline retrieval models, vector space model (VSM), in recommending diabetic patient education materials to diabetic questions posted on the TuDiabetes forum. The evaluation was based on a gold standard dataset consisting of 50 randomly selected diabetic questions where the relevancy of diabetic education materials to the questions was manually assigned by two experts. The performance was assessed using precision of top-ranked documents. Results We retrieved 7510 diabetic questions on the forum and 144 diabetic patient educational materials from the patient education database at Mayo Clinic. The mapping rate of words in each corpus mapped to the Unified Medical Language System (UMLS) was significantly different (P<.001). The topic modeling-based model outperformed the other retrieval algorithms. For example, for the top-retrieved document, the precision of the topic modeling-based, semantic group-based, and VSM models was 67.0%, 62.8%, and 54.3%, respectively. Conclusions This study demonstrated that topic modeling can mitigate the vocabulary difference and it achieved the best performance in recommending education materials for answering patients’ questions. One direction for future work is to assess the generalizability of our findings and to extend our study to other disease areas, other patient education material resources, and online forums. PMID:29038097

Experimental validation of a 0-D numerical model for phase change thermal management systems in lithium-ion batteries

NASA Astrophysics Data System (ADS)

Schweitzer, Ben; Wilke, Stephen; Khateeb, Siddique; Al-Hallaj, Said

2015-08-01

A lumped (0-D) numerical model has been developed for simulating the thermal response of a lithium-ion battery pack with a phase-change composite (PCC™) thermal management system. A small 10s4p battery pack utilizing PCC material was constructed and subjected to discharge at various C-rates in order to validate the lumped model. The 18650 size Li-ion cells used in the pack were electrically characterized to determine their heat generation, and various PCC materials were thermally characterized to determine their apparent specific heat as a function of temperature. Additionally, a 2-D FEA thermal model was constructed to help understand the magnitude of spatial temperature variation in the pack, and to understand the limitations of the lumped model. Overall, good agreement is seen between experimentally measured pack temperatures and the 0-D model, and the 2-D FEA model predicts minimal spatial temperature variation for PCC-based packs at C-rates of 1C and below.

A pressure relaxation closure model for one-dimensional, two-material Lagrangian hydrodynamics based on the Riemann problem

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

Kamm, James R; Shashkov, Mikhail J

2009-01-01

Despite decades of development, Lagrangian hydrodynamics of strengthfree materials presents numerous open issues, even in one dimension. We focus on the problem of closing a system of equations for a two-material cell under the assumption of a single velocity model. There are several existing models and approaches, each possessing different levels of fidelity to the underlying physics and each exhibiting unique features in the computed solutions. We consider the case in which the change in heat in the constituent materials in the mixed cell is assumed equal. An instantaneous pressure equilibration model for a mixed cell can be cast asmore » four equations in four unknowns, comprised of the updated values of the specific internal energy and the specific volume for each of the two materials in the mixed cell. The unique contribution of our approach is a physics-inspired, geometry-based model in which the updated values of the sub-cell, relaxing-toward-equilibrium constituent pressures are related to a local Riemann problem through an optimization principle. This approach couples the modeling problem of assigning sub-cell pressures to the physics associated with the local, dynamic evolution. We package our approach in the framework of a standard predictor-corrector time integration scheme. We evaluate our model using idealized, two material problems using either ideal-gas or stiffened-gas equations of state and compare these results to those computed with the method of Tipton and with corresponding pure-material calculations.« less

Retardation analytical model to extend service life

NASA Technical Reports Server (NTRS)

Matejczyk, D.

1984-01-01

A fatigue crack growth model that incorporates crack growth retardation effects and is applicable to the materials characteristics and service environments of high performance LH2/LO2 engine systems was developed and tested.

Structural and Machine Design Using Piezoceramic Materials: A Guide for Structural Design Engineers

NASA Technical Reports Server (NTRS)

Inman, Daniel J.; Cudney, Harley H.

2000-01-01

Using piezoceramic materials is one way the design engineer can create structures which have an ability to both sense and respond to their environment. Piezoceramic materials can be used to create structural sensors and structural actuators. Because piezoceramic materials have transduction as a material property, their sensing or actuation functions are a result of what happens to the material. This is different than discrete devices we might attach to the structure. For example, attaching an accelerometer to a structure will yield an electrical signal proportional to the acceleration at the attachment point on the structure. Using a electromagnetic shaker as an actuator will create an applied force at the attachment point. Active material elements in a structural design are not easily modeled as providing transduction at a point, but rather they change the physics of the structure in the areas where they are used. Hence, a designer must not think of adding discrete devices to a structure to obtain an effect, but rather must design a structural system which accounts for the physical principles of all the elements in the structure. The purpose of this manual is to provide practicing engineers the information necessary to incorporate piezoelectric materials in structural design and machine design. First, we will review the solid-state physics of piezoelectric materials. Then we will discuss the physical characteristics of the electrical-active material-structural system. We will present the elements of this system which must be considered as part of the design task for a structural engineer. We will cover simple modeling techniques and review the features and capabilities of commercial design tools that are available. We will then cover practical how-to elements of working with piezoceramic materials. We will review sources of piezoceramic materials and built-up devices, and their characteristics. Finally, we will provide two design examples using piezoceramic materials, first as discrete actuators for vibration isolation, and second as structurally-distributed sensor/actuators for active acoustic control.

Information Management Workflow and Tools Enabling Multiscale Modeling Within ICME Paradigm

NASA Technical Reports Server (NTRS)

Arnold, Steven M.; Bednarcyk, Brett A.; Austin, Nic; Terentjev, Igor; Cebon, Dave; Marsden, Will

2016-01-01

With the increased emphasis on reducing the cost and time to market of new materials, the need for analytical tools that enable the virtual design and optimization of materials throughout their processing - internal structure - property - performance envelope, along with the capturing and storing of the associated material and model information across its lifecycle, has become critical. This need is also fueled by the demands for higher efficiency in material testing; consistency, quality and traceability of data; product design; engineering analysis; as well as control of access to proprietary or sensitive information. Fortunately, material information management systems and physics-based multiscale modeling methods have kept pace with the growing user demands. Herein, recent efforts to establish workflow for and demonstrate a unique set of web application tools for linking NASA GRC's Integrated Computational Materials Engineering (ICME) Granta MI database schema and NASA GRC's Integrated multiscale Micromechanics Analysis Code (ImMAC) software toolset are presented. The goal is to enable seamless coupling between both test data and simulation data, which is captured and tracked automatically within Granta MI®, with full model pedigree information. These tools, and this type of linkage, are foundational to realizing the full potential of ICME, in which materials processing, microstructure, properties, and performance are coupled to enable application-driven design and optimization of materials and structures.

[Cointegration test and variance decomposition for the relationship between economy and environment based on material flow analysis in Tangshan City Hebei China].

PubMed

2015-12-01

The material flow account of Tangshan City was established by material flow analysis (MFA) method to analyze the periodical characteristics of material input and output in the operation of economy-environment system, and the impact of material input and output intensities on economic development. Using econometric model, the long-term interaction mechanism and relationship among the indexes of gross domestic product (GDP) , direct material input (DMI), domestic processed output (DPO) were investigated after unit root hypothesis test, Johansen cointegration test, vector error correction model, impulse response function and variance decomposition. The results showed that during 1992-2011, DMI and DPO both increased, and the growth rate of DMI was higher than that of DPO. The input intensity of DMI increased, while the intensity of DPO fell in volatility. Long-term stable cointegration relationship existed between GDP, DMI and DPO. Their interaction relationship showed a trend from fluctuation to gradual ste adiness. DMI and DPO had strong, positive impacts on economic development in short-term, but the economy-environment system gradually weakened these effects by short-term dynamically adjusting indicators inside and outside of the system. Ultimately, the system showed a long-term equilibrium relationship. The effect of economic scale on economy was gradually increasing. After decomposing the contribution of each index to GDP, it was found that DMI's contribution grew, GDP's contribution declined, DPO's contribution changed little. On the whole, the economic development of Tangshan City has followed the traditional production path of resource-based city, mostly depending on the material input which caused high energy consumption and serous environmental pollution.

Multi-domain boundary element method for axi-symmetric layered linear acoustic systems

NASA Astrophysics Data System (ADS)

Reiter, Paul; Ziegelwanger, Harald

2017-12-01

Homogeneous porous materials like rock wool or synthetic foam are the main tool for acoustic absorption. The conventional absorbing structure for sound-proofing consists of one or multiple absorbers placed in front of a rigid wall, with or without air-gaps in between. Various models exist to describe these so called multi-layered acoustic systems mathematically for incoming plane waves. However, there is no efficient method to calculate the sound field in a half space above a multi layered acoustic system for an incoming spherical wave. In this work, an axi-symmetric multi-domain boundary element method (BEM) for absorbing multi layered acoustic systems and incoming spherical waves is introduced. In the proposed BEM formulation, a complex wave number is used to model absorbing materials as a fluid and a coordinate transformation is introduced which simplifies singular integrals of the conventional BEM to non-singular radial and angular integrals. The radial and angular part are integrated analytically and numerically, respectively. The output of the method can be interpreted as a numerical half space Green's function for grounds consisting of layered materials.

Advanced cathode materials for polymer electrolyte fuel cells based on pt/ metal oxides: from model electrodes to catalyst systems.

PubMed

Fabbri, Emiliana; Pătru, Alexandra; Rabis, Annett; Kötz, Rüdiger; Schmidt, Thomas J

2014-01-01

The development of stable catalyst systems for application at the cathode side of polymer electrolyte fuel cells (PEFCs) requires the substitution of the state-of-the-art carbon supports with materials showing high corrosion resistance in a strongly oxidizing environment. Metal oxides in their highest oxidation state can represent viable support materials for the next generation PEFC cathodes. In the present work a multilevel approach has been adopted to investigate the kinetics and the activity of Pt nanoparticles supported on SnO2-based metal oxides. Particularly, model electrodes made of SnO2 thin films supporting Pt nanoparticles, and porous catalyst systems made of Pt nanoparticles supported on Sb-doped SnO2 high surface area powders have been investigated. The present results indicate that SnO2-based supports do not modify the oxygen reduction reaction mechanism on the Pt nanoparticle surface, but rather lead to catalysts with enhanced specific activity compared to Pt/carbon systems. Different reasons for the enhancement in the specific activity are considered and discussed.

Accelerating materials discovery through the development of polymer databases

NASA Astrophysics Data System (ADS)

Audus, Debra

In our line of business we create chemical solutions for a wide range of applications, such as home and personal care, printing and packaging, automotive and structural coatings, and structural plastics and foams applications. In this environment, stable and highly automated workflows suitable to handle complex systems are a must. By satisfying these prerequisites, efficiency for the development of new materials can be significantly improved by combining modeling and experimental approaches. This is in fact in line with recent Materials Genome Initiative efforts sponsored by the US administration. From our experience, we know, that valuable contributions to product development are possible today by combining existing modeling techniques in an intelligent fashion, provided modeling and experiment work closely together. In my presentation I intend to review approaches to build and parameterize soft matter systems. As an example of our standard workflow, I will show a few applications, which include the design of a stabilizer molecule for dispersing polymer particles and the simulation of polystyrene dispersions.

A Risk-Based Approach for Aerothermal/TPS Analysis and Testing

NASA Technical Reports Server (NTRS)

Wright, Michael J.; Grinstead, Jay H.; Bose, Deepak

2007-01-01

The current status of aerothermal and thermal protection system modeling for civilian entry missions is reviewed. For most such missions, the accuracy of our simulations is limited not by the tools and processes currently employed, but rather by reducible deficiencies in the underlying physical models. Improving the accuracy of and reducing the uncertainties in these models will enable a greater understanding of the system level impacts of a particular thermal protection system and of the system operation and risk over the operational life of the system. A strategic plan will be laid out by which key modeling deficiencies can be identified via mission-specific gap analysis. Once these gaps have been identified, the driving component uncertainties are determined via sensitivity analyses. A Monte-Carlo based methodology is presented for physics-based probabilistic uncertainty analysis of aerothermodynamics and thermal protection system material response modeling. These data are then used to advocate for and plan focused testing aimed at reducing key uncertainties. The results of these tests are used to validate or modify existing physical models. Concurrently, a testing methodology is outlined for thermal protection materials. The proposed approach is based on using the results of uncertainty/sensitivity analyses discussed above to tailor ground testing so as to best identify and quantify system performance and risk drivers. A key component of this testing is understanding the relationship between the test and flight environments. No existing ground test facility can simultaneously replicate all aspects of the flight environment, and therefore good models for traceability to flight are critical to ensure a low risk, high reliability thermal protection system design. Finally, the role of flight testing in the overall thermal protection system development strategy is discussed.

Redox States of Initial Atmospheres Outgassed on Rocky Planets and Planetesimals

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

Schaefer, Laura; Fegley, Bruce Jr., E-mail: lschaefer@asu.edu

2017-07-10

The Earth and other rocky planets and planetesimals in the solar system formed through the mixing of materials from various radial locations in the solar nebula. This primordial material likely had a range of oxidation states as well as bulk compositions and volatile abundances. We investigate the oxygen fugacity produced by the outgassing of mixtures of solid meteoritic material, which approximate the primitive nebular materials. We find that the gas composition and oxygen fugacity of binary and ternary mixtures of meteoritic materials vary depending on the proportion of reduced versus oxidized material, and also find that mixtures using differentiated materialsmore » do not show the same oxygen fugacity trends as those using similarly reduced but undifferentiated materials. We also find that simply mixing the gases produced by individual meteoritic materials together does not correctly reproduce the gas composition or oxygen fugacity of the binary and ternary mixtures. We provide tabulated fits for the oxygen fugacities of all of the individual materials and binary mixtures that we investigate. These values may be useful in planetary formation models, models of volatile transport on planetesimals or meteorite parent bodies, or models of trace element partitioning during metal-silicate fractionation.« less

A Survey and Analysis of Military Computer-Based Systems: A Two Part Study. Volume II. A Descriptive and Predictive Model for Evaluating Instructional Systems. Final Report.

ERIC Educational Resources Information Center

McDonnell Douglas Astronautics Co. - East, St. Louis, MO.

This is the second volume of a two volume study. The first volume examined the literature to identify authoring aids for developing instructional materials, and to identify information clearing houses for existing materials. The purpose of this volume was to develop a means for assessing the cost versus expected benefits of innovations in…

Technologies Enabling Scientific Exploration of Asteroids and Moons

NASA Astrophysics Data System (ADS)

Shaw, A.; Fulford, P.; Chappell, L.

2016-12-01

Scientific exploration of moons and asteroids is enabled by several key technologies that yield topographic information, allow excavation of subsurface materials, and allow delivery of higher-mass scientific payloads to moons and asteroids. These key technologies include lidar systems, robotics, and solar-electric propulsion spacecraft buses. Many of these technologies have applications for a variety of planetary targets. Lidar systems yield high-resolution shape models of asteroids and moons. These shape models can then be combined with radio science information to yield insight into density and internal structure. Further, lidar systems allow investigation of topographic surface features, large and small, which yields information on regolith properties. Robotic arms can be used for a variety of purposes, especially to support excavation, revealing subsurface material and acquiring material from depth for either in situ analysis or sample return. Robotic arms with built-in force sensors can also be used to gauge the strength of materials as a function of depth, yielding insight into regolith physical properties. Mobility systems allow scientific exploration of multiple sites, and also yield insight into regolith physical properties due to the interaction of wheels with regolith. High-power solar electric propulsion (SEP) spacecraft bus systems allow more science instruments to be included on missions given their ability to support greater payload mass. In addition, leveraging a cost-effective commercially-built SEP spacecraft bus can significantly reduce mission cost.

A Route to Dirac Liquid Theory: A Fermi Liquid Description for Dirac Materials

NASA Astrophysics Data System (ADS)

Gochan, Matthew; Bedell, Kevin

Since the pioneering work developed by L.V. Landau sixty years ago, Fermi Liquid Theory has seen great success in describing interacting Fermi systems. While much interest has been generated over the study of non-Fermi Liquid systems, Fermi Liquid theory serves as a formidable model for many systems and offers a rich amount of of results and insight. The recent classification of Dirac Materials, and the lack of a unifying theoretical framework for them, has motivated our study. Dirac materials are a versatile class of materials in which an abundance of unique physical phenomena can be observed. Such materials are found in all dimensions, with the shared property that their low-energy fermionic excitations behave as massless Dirac fermions and are therefore governed by the Dirac equation. The most popular Dirac material, graphene, is the focus of this work. We present our Fermi Liquid description of Graphene. We find many interesting results, specifically in the transport and dynamics of the system. Additionally, we expand on previous work regarding the Virial Theorem and its impact on the Fermi Liquid parameters in graphene. Finally, we remark on viscoelasticity of Dirac Materials and other unusual results that are consequences of AdS-CFT.

Quantitative NDE applied to composites and metals

NASA Technical Reports Server (NTRS)

Heyman, Joseph S.; Winfree, William P.; Parker, F. Raymond; Heath, D. Michele; Welch, Christopher S.

1989-01-01

Research at the NASA/Langley Research Center concerning quantitative NDE of composites and metals is reviewed. The relationship between ultrasonics and polymer cure is outlined. NDE models are presented, which can be used to develop measurement technologies for characterizing the curing of a polymer system for composite materials. The models can be used to determine the glass transition temperature, the degree of cure, and the cure rate. The application of the model to control autoclave processing of composite materials is noted. Consideration is given to the use of thermal diffusion models combined with controlled thermal input measurements to determine the thermal diffusivity of materials. Also, a two-dimensional physical model is described that permits delaminations in samples of Space Shuttle Solid Rocket Motors to be detected in thermograms in the presence of cooling effects and uneven heating.

Material Development to Raise Awareness of Using Smart Boards: An Example Design and Development Research

ERIC Educational Resources Information Center

Günaydin, Serpil; Karamete, Aysen

2016-01-01

This study aims to develop training material that will help raise awareness in prospective teachers regarding the benefits of using smart boards in the classroom. In this study, a Type 2 design and development research method (DDR) was used. The material was developed by applying phases of ADDIE--an instructional systems design model. The…

Acoustical characterization and parameter optimization of polymeric noise control materials

NASA Astrophysics Data System (ADS)

Homsi, Emile N.

2003-10-01

The sound transmission loss (STL) characteristics of polymer-based materials are considered. Analytical models that predict, characterize and optimize the STL of polymeric materials, with respect to physical parameters that affect performance, are developed for single layer panel configuration and adapted for layered panel construction with homogenous core. An optimum set of material parameters is selected and translated into practical applications for validation. Sound attenuating thermoplastic materials designed to be used as barrier systems in the automotive and consumer industries have certain acoustical characteristics that vary in function of the stiffness and density of the selected material. The validity and applicability of existing theory is explored, and since STL is influenced by factors such as the surface mass density of the panel's material, a method is modified to improve STL performance and optimize load-bearing attributes. An experimentally derived function is applied to the model for better correlation. In-phase and out-of-phase motion of top and bottom layers are considered. It was found that the layered construction of the co-injection type would exhibit fused planes at the interface and move in-phase. The model for the single layer case is adapted to the layered case where it would behave as a single panel. Primary physical parameters that affect STL are identified and manipulated. Theoretical analysis is linked to the resin's matrix attribute. High STL material with representative characteristics is evaluated versus standard resins. It was found that high STL could be achieved by altering materials' matrix and by integrating design solution in the low frequency range. A suggested numerical approach is described for STL evaluation of simple and complex geometries. In practice, validation on actual vehicle systems proved the adequacy of the acoustical characterization process.

Data-driven reduced order models for effective yield strength and partitioning of strain in multiphase materials

NASA Astrophysics Data System (ADS)

Latypov, Marat I.; Kalidindi, Surya R.

2017-10-01

There is a critical need for the development and verification of practically useful multiscale modeling strategies for simulating the mechanical response of multiphase metallic materials with heterogeneous microstructures. In this contribution, we present data-driven reduced order models for effective yield strength and strain partitioning in such microstructures. These models are built employing the recently developed framework of Materials Knowledge Systems that employ 2-point spatial correlations (or 2-point statistics) for the quantification of the heterostructures and principal component analyses for their low-dimensional representation. The models are calibrated to a large collection of finite element (FE) results obtained for a diverse range of microstructures with various sizes, shapes, and volume fractions of the phases. The performance of the models is evaluated by comparing the predictions of yield strength and strain partitioning in two-phase materials with the corresponding predictions from a classical self-consistent model as well as results of full-field FE simulations. The reduced-order models developed in this work show an excellent combination of accuracy and computational efficiency, and therefore present an important advance towards computationally efficient microstructure-sensitive multiscale modeling frameworks.

Temperature dependency of the thermal conductivity of porous heat storage media

NASA Astrophysics Data System (ADS)

Hailemariam, Henok; Wuttke, Frank

2018-04-01

Analyzing the variation of thermal conductivity with temperature is vital in the design and assessment of the efficiency of sensible heat storage systems. In this study, the temperature variation of the thermal conductivity of a commercial cement-based porous heat storage material named - Füllbinder L is analyzed in saturated condition in the temperature range between 20 to 70°C (water based storage) with a steady state thermal conductivity and diffusivity meter. A considerable decrease in the thermal conductivity of the saturated sensible heat storage material upon increase in temperature is obtained, resulting in a significant loss of system efficiency and slower loading/un-loading rates, which when unaccounted for can lead to the under-designing of such systems. Furthermore, a new empirical prediction model for the estimation of thermal conductivity of cement-based porous sensible heat storage materials and naturally occurring crystalline rock formations as a function of temperature is proposed. The results of the model prediction are compared with the experimental results with satisfactory results.

Full inhibition of enzymatic browning in the presence of thiol-functionalised silica nanomaterial.

PubMed

Muñoz-Pina, Sara; Ros-Lis, José V; Argüelles, Ángel; Coll, Carmen; Martínez-Máñez, Ramón; Andrés, Ana

2018-02-15

Darkening processed fruits and vegetables is caused mainly by enzymatic browning through polyphenol oxidase (PPO) action. Accordingly, we explored the potential of four silica-based materials (MCM-41 nanometric size, MCM-41 micrometric size, UVM-7 and aerosil), non-functionalised and functionalised with thiol groups, to inhibit PPO activity in the model system and apple juice. All materials showed relevant performance when immobilising and inhibiting PPO in model systems, and support topology is a main factor for enzyme immobilisation and inhibition. Thiol-containing silica UVM7-SH showed the greatest inactivation, and similar browning values to those obtained by acidification. The enzyme's kinetic parameters in the presence of UVM-7-SH suggested non-competitive inhibition, which indicated that the material interacted with the enzyme, but beyond the active centre. In real systems, UVM-7-SH completely inhibited enzymatic browning in apple juice (cv. Granny Smith and cv. Golden Delicious) up to 9days after 5min of contact. Copyright © 2017 Elsevier Ltd. All rights reserved.

Spatial and temporal modeling of sub- and supercritical thermal energy storage

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

Tse, LA; Ganapathi, GB; Wirz, RE

2014-05-01

This paper describes a thermodynamic model that simulates the discharge cycle of a single-tank thermal energy storage (TES) system that can operate from the two-phase (liquid-vapor) to supercritical regimes for storage fluid temperatures typical of concentrating solar power plants. State-of-the-art TES design utilizes a two-tank system with molten nitrate salts; one major problem is the high capital cost of the salts (International Renewable Energy Agency, 2012). The alternate approach explored here opens up the use of low-cost fluids by considering operation at higher pressures associated with the two-phase and supercritical regimes. The main challenge to such a system is itsmore » high pressures and temperatures which necessitate a relatively high-cost containment vessel that represents a large fraction of the system capital cost. To mitigate this cost, the proposed design utilizes a single-tank TES system, effectively halving the required wall material. A single-tank approach also significantly reduces the complexity of the system in comparison to the two-tank systems, which require expensive pumps and external heat exchangers. A thermodynamic model is used to evaluate system performance; in particular it predicts the volume of tank wall material needed to encapsulate the storage fluid. The transient temperature of the tank is observed to remain hottest at the storage tank exit, which is beneficial to system operation. It is also shown that there is an optimum storage fluid loading that generates a given turbine energy output while minimizing the required tank wall material. Overall, this study explores opportunities to further improve current solar thermal technologies. The proposed single-tank system shows promise for decreasing the cost of thermal energy storage. (C) 2014 Elsevier Ltd. All rights reserved.« less

Assessment of Technologies for the Space Shuttle External Tank Thermal Protection System and Recommendations for Technology Improvement - Part III: Material Property Characterization, Analysis, and Test Methods

NASA Technical Reports Server (NTRS)

Gates, Thomas S.; Johnson, Theodore F.; Whitley, Karen S.

2005-01-01

The objective of this report is to contribute to the independent assessment of the Space Shuttle External Tank Foam Material. This report specifically addresses material modeling, characterization testing, data reduction methods, and data pedigree. A brief description of the External Tank foam materials, locations, and standard failure modes is provided to develop suitable background information. A review of mechanics based analysis methods from the open literature is used to provide an assessment of the state-of-the-art in material modeling of closed cell foams. Further, this report assesses the existing material property database and investigates sources of material property variability. The report presents identified deficiencies in testing methods and procedures, recommendations for additional testing as required, identification of near-term improvements that should be pursued, and long-term capabilities or enhancements that should be developed.

Effect law of Damage Characteristics of Rock Similar Material with Pre-Existing Cracks

NASA Astrophysics Data System (ADS)

Li, S. G.; Cheng, X. Y.; Liu, C.

2017-11-01

In order to further study the failure mechanism for rock similar materials, this study established the damage model based on accumulative AE events, investigated the damage characteristics for rock similar material samples with pre-existing cracks of varying width under uniaxial compression load. The equipment used in this study is the self-developed YYW-II strain controlled unconfined compression apparatus and the PCIE-8 acoustic emission (AE) monitoring system. The influences of the width of the pre-existing cracks to the damage characteristics of rock similar materials are analyzed. Results show that, (1) the damage model can better describe the damage characteristics of rock similar materials; (2) the tested samples have three stages during failure: initial damage stage, stable development of damage stage, and accelerated development of damage stage; (3) with the width of pre-existing cracks vary from 3mm to 5mm, the damage of rock similar materials increases gradually. The outcomes of this study provided additional values to the research of the failure mechanism for geotechnical similar material models.

Probabilistic Material Strength Degradation Model for Inconel 718 Components Subjected to High Temperature, Mechanical Fatigue, Creep and Thermal Fatigue Effects

NASA Technical Reports Server (NTRS)

Bast, Callie Corinne Scheidt

1994-01-01

This thesis presents the on-going development of methodology for a probabilistic material strength degradation model. The probabilistic model, in the form of a postulated randomized multifactor equation, provides for quantification of uncertainty in the lifetime material strength of aerospace propulsion system components subjected to a number of diverse random effects. This model is embodied in the computer program entitled PROMISS, which can include up to eighteen different effects. Presently, the model includes four effects that typically reduce lifetime strength: high temperature, mechanical fatigue, creep, and thermal fatigue. Statistical analysis was conducted on experimental Inconel 718 data obtained from the open literature. This analysis provided regression parameters for use as the model's empirical material constants, thus calibrating the model specifically for Inconel 718. Model calibration was carried out for four variables, namely, high temperature, mechanical fatigue, creep, and thermal fatigue. Methodology to estimate standard deviations of these material constants for input into the probabilistic material strength model was developed. Using the current version of PROMISS, entitled PROMISS93, a sensitivity study for the combined effects of mechanical fatigue, creep, and thermal fatigue was performed. Results, in the form of cumulative distribution functions, illustrated the sensitivity of lifetime strength to any current value of an effect. In addition, verification studies comparing a combination of mechanical fatigue and high temperature effects by model to the combination by experiment were conducted. Thus, for Inconel 718, the basic model assumption of independence between effects was evaluated. Results from this limited verification study strongly supported this assumption.

75 FR 53855 - Airworthiness Directives; BAE Systems (Operations) Limited Model BAe 146 and Avro 146-RJ Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2010-09-02

.... This puncture tends to result in a tear, which, if detected in time, can be repaired with tape; however... bag also tends to cause tears in the material, making the insulation material sag, thereby causing...

75 FR 27959 - Airworthiness Directives; BAE Systems (Operations) Limited Model BAe 146 and Avro 146-RJ Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2010-05-19

.... This puncture tends to result in a tear, which, if detected in time, can be repaired with tape; however... bag also tends to cause tears in the material, making the insulation material sag, thereby causing...

Elastic constants of stressed and unstressed materials in the phase-field crystal model

NASA Astrophysics Data System (ADS)

Wang, Zi-Le; Huang, Zhi-Feng; Liu, Zhirong

2018-04-01

A general procedure is developed to investigate the elastic response and calculate the elastic constants of stressed and unstressed materials through continuum field modeling, particularly the phase-field crystal (PFC) models. It is found that for a complete description of system response to elastic deformation, the variations of all the quantities of lattice wave vectors, their density amplitudes (including the corresponding anisotropic variation and degeneracy breaking), the average atomic density, and system volume should be incorporated. The quantitative and qualitative results of elastic constant calculations highly depend on the physical interpretation of the density field used in the model, and also importantly, on the intrinsic pressure that usually pre-exists in the model system. A formulation based on thermodynamics is constructed to account for the effects caused by constant pre-existing stress during the homogeneous elastic deformation, through the introducing of a generalized Gibbs free energy and an effective finite strain tensor used for determining the elastic constants. The elastic properties of both solid and liquid states can be well produced by this unified approach, as demonstrated by an analysis for the liquid state and numerical evaluations for the bcc solid phase. The numerical calculations of bcc elastic constants and Poisson's ratio through this method generate results that are consistent with experimental conditions, and better match the data of bcc Fe given by molecular dynamics simulations as compared to previous work. The general theory developed here is applicable to the study of different types of stressed or unstressed material systems under elastic deformation.

Model Compound Studies of Rigid Rod Aromatic Heterocyclic Polymer Systems, the X-Ray Crystal Structure of 2,6-Diphenylbenzo (1,2-d; 5,4-d’) Diimidazole Tetrahydrate, C2OH14N4. 4H2O, a Model System for the Study of Polymer-Water Interaction in Polybenzimidazoles.

DTIC Science & Technology

1983-07-01

Marilyn Hunsaker and W. Wade Adams Polyimer Branch Nonmetallic Division Albert V. Fratini University of Dayton Research Institute 300 College Park...U. CONTRACT OR GRANT NUMUER(e) M. Hunsaker, and W. W. Adams , Air Force Wright I atudrcnrc Aeronautical Laboratories, Materials Laboratory F33615-81-C...Scientist. Co-authors were Marilyn Hunsaker and W. W. Adams , Materials Laboratory (AFWAL/MLHP); and Dr. Albert V. Fratini, University of Dayton Research

Fuzzy control of burnout of multilayer ceramic actuators

NASA Astrophysics Data System (ADS)

Ling, Alice V.; Voss, David; Christodoulou, Leo

1996-08-01

To improve the yield and repeatability of the burnout process of multilayer ceramic actuators (MCAs), an intelligent processing of materials (IPM-based) control system has been developed for the manufacture of MCAs. IPM involves the active (ultimately adaptive) control of a material process using empirical or analytical models and in situ sensing of critical process states (part features and process parameters) to modify the processing conditions in real time to achieve predefined product goals. Thus, the three enabling technologies for the IPM burnout control system are process modeling, in situ sensing and intelligent control. This paper presents the design of an IPM-based control strategy for the burnout process of MCAs.

Modeling and simulation of clutch pressure plate casting using alternate materials

NASA Astrophysics Data System (ADS)

Madhuraj, H. N.; Bharath, M. R.

2018-04-01

Clutch Pressure Plate is a stress bearing component in the clutch assembly. Cast iron alloys like FG300, G2500 are commonly used for clutch pressure plate castings. These materials have high compressive strength, low tensile strength & no ductility but these cost high for the manufacturers. There is a need for alternate material so as to reduce cost, defects in castings without losing the life and effectiveness of the clutch plate. The work carried out here is modeling the clutch pressure plate using CAD tool. And then the casting process is simulated by casting simulation for fluid flow and solidification analysis by trying alternate material. Here the castability of the alternate material En-Gjs-400-15 and the commonly used material FG300 for the clutch pressure plate component is analyzed by designing and optimizing a proper gating system.

Modeling Surface Processes Occurring on Moons of the Outer Solar System

NASA Astrophysics Data System (ADS)

Umurhan, O. M.; White, O. L.; Moore, J. M.; Howard, A. D.; Schenk, P.

2016-12-01

A variety of processes, some with familiar terrestrial analogs, are known to take place on moon surfaces in the outer solar system. In this talk, we discuss the observed features of mass wasting and surface transport seen on both Jupiter's moon Calisto and one of Saturn's Trojan moons Helene. We provide a number of numerical models using upgraded version of MARSSIM in support of several hypotheses suggested on behalf of the observations made regarding these objects. Calisto exhibits rolling plains of low albedo materials surrounding relatively high jutting peaks harboring high albedo deposits. Our modeling supports the interpretation that Calisto's surface is a record of erosion driven by the sublimation of CO2 and H2O contained in the bedrock. Both solar insolation and surface re-radiation drives the sublimation leaving behind debris which we interpret to be the observed darkened regolith and, further, the high albedo peaks are water ice deposits on surface cold traps. On the other hand, the 45 km scale Helene, being a milligravity environment, exhibits mysterious looking streaks and grooves of very high albedo materials extending for several kilometers with a down-sloping grade of 7o-9o. Helene's cratered terrain also shows evidence of narrowed septa. The observed surface features suggest some type of advective processes are at play in this system. Our modeling lends support to the suggestion that Helene's surface materials behave as a Bingham plastic material - our flow modeling with such rheologies can reproduce the observed pattern of streakiness depending upon the smoothness of the underlying bedrock; the overall gradients observed; and the narrowed septa of inter-crater regions.

Optimizing emissions targets for residential recycling programmes: Why 'more' is not necessarily better with respect to diversion.

PubMed

Lakhan, Calvin

2016-11-01

This study highlights the economic and environmental challenges of recycling in Ontario, specifically examining the effect of attempting to increase the emissions target for the province's household recycling programme. The findings from the cost model analysis found that Ontario's Blue Box programme reduces overall carbon emissions by approximately 1.8 million tonnes every year. This study also found that targeting specific materials for recovery could result in a scenario where the province could improve both overall diversion and emissions offsets while reducing material management costs. Under our modelled scenario, as the tonnes of greenhouse gases (GHGs) avoided increases, the system cost per tonne of GHG avoided initial declines. However, after avoiding 2.05 million tonnes of GHGs, the system cost/tonne GHG avoided increases. To achieve an emissions target in excess of 2.05 million tonnes, the province will have to start recycling higher cost non-core materials (composite materials, other plastics, etc.). © The Author(s) 2016.

Granular dynamics under shear with deformable boundaries

NASA Astrophysics Data System (ADS)

Geller, Drew; Backhaus, Scott; Ecke, Robert

2015-03-01

Granular materials under shear develop complex patterns of stress as the result of granular positional rearrangements under an applied load. We consider the simple planar shear of a quasi two-dimensional granular material consisting of bi-dispersed nylon cylinders confined between deformable boundaries. The aspect ratio of the gap width to total system length is 50, and the ratio of particle diameter to gap width is about 10. This system, designed to model a long earthquake fault with long range elastic coupling through the plates, is an interesting model system for understanding effective granular friction because it essentially self tunes to the jamming condition owing to the hardness of the grains relative to that of the boundary material, a ratio of more than 1000 in elastic moduli. We measure the differential strain displacements of the plates, the inhomogeneous stress distribution in the plates, the positions and angular orientations of the individual grains, and the shear force, all as functions of the applied normal stress. There is significant stick-slip motion in this system that we quantify through our quantitative measurements of both the boundary and the grain motion, resulting in a good characterization of this sheared 2D hard sphere system.

Constitutive and damage material modeling in a high pressure hydrogen environment

NASA Technical Reports Server (NTRS)

Russell, D. A.; Fritzemeier, L. G.

1991-01-01

Numerous components in reusable space propulsion systems such as the SSME are exposed to high pressure gaseous hydrogen environments. Flow areas and passages in the fuel turbopump, fuel and oxidizer preburners, main combustion chamber, and injector assembly contain high pressure hydrogen either high in purity or as hydrogen rich steam. Accurate constitutive and damage material models applicable to high pressure hydrogen environments are therefore needed for engine design and analysis. Existing constitutive and cyclic crack initiation models were evaluated only for conditions of oxidizing environments. The main objective is to evaluate these models for applicability to high pressure hydrogen environments.

Boilermodel: A Qualitative Model-Based Reasoning System Implemented in Ada

DTIC Science & Technology

1991-09-01

comple- ment to shipboard engineering training. Accesion For NTIS CRA&I DTIO I A3 f_- Unairmoui1ccd [i Justification By ................... Distribut;or, I...investment (in terms of man-hours lost, equipment maintenance, materials, etc.) for initial training. On- going training is also required to sustain a...REASONING FROM MODELS Model-based expert systems have been written in many languages and for many different architectures . Knowledge representation also

Finite-Element Modeling of a Damaged Pipeline Repaired Using the Wrap of a Composite Material

NASA Astrophysics Data System (ADS)

Lyapin, A. A.; Chebakov, M. I.; Dumitrescu, A.; Zecheru, G.

2015-07-01

The nonlinear static problem of FEM modeling of a damaged pipeline repaired by a composite material and subjected to internal pressure is considered. The calculation is carried out using plasticity theory for the pipeline material and considering the polymeric filler and the composite wrap. The level of stresses in various zones of the structure is analyzed. The most widespread alloy used for oil pipelines is selected as pipe material. The contribution of each component of the pipeline-filler-wrap system to the level of stresses is investigated. The effect of the number of composite wrap layers is estimated. The results obtained allow one to decrease the costs needed for producing test specimens.

A model for dental hygiene education concerning the relationship between periodontal health and systemic health.

PubMed

Bush, Barbara Crafton; Donley, Timothy G

2002-01-01

To develop a format for educating the appropriate health care professionals as to the relationships between periodontal inflammation and increased risks for poor diabetes control, cardiovascular disease, cerebrovascular disease, pre-term low birth weight, pneumonia and gastric ulcer reinfection. Dental hygiene students in the Advanced Periodontology curriculum were instructed to review current literature regarding the increased risk for systemic health problems when periodontal inflammation is present. Abstracts of the reviewed material were then presented in group setting to all course participants. For each systemic entity (diabetes, cardio/cerebrovascular disease, adverse pregnancy outcome, pneumonia, gastric ulcer) literature-based evidence of periodontal disease's association, affect, pathogenesis, validity and clinical significance was determined. Consensus statements for each entity were developed and used as a basis for clinical interpretation. Following this, patient health-history materials were developed to obtain the necessary information from patients while educating them about the increased risk for systemic health problems when periodontal inflammation is present. Lastly, correspondence materials were developed to alert managing physicians and medical auxiliaries about the increased risk for systemic problems in their patients who may present with periodontal inflammation. A methodology which medical personnel can use to quickly screen for the presence of periodontal inflammation in at-risk patients was also developed in these correspondences. An educational model and clinical materials were developed which are aimed at alerting patients, dental and medical personnel to the increased risk for systemic health problems when inflammatory periodontal disease is present.

Realistic micromechanical modeling and simulation of two-phase heterogeneous materials

NASA Astrophysics Data System (ADS)

Sreeranganathan, Arun

This dissertation research focuses on micromechanical modeling and simulations of two-phase heterogeneous materials exhibiting anisotropic and non-uniform microstructures with long-range spatial correlations. Completed work involves development of methodologies for realistic micromechanical analyses of materials using a combination of stereological techniques, two- and three-dimensional digital image processing, and finite element based modeling tools. The methodologies are developed via its applications to two technologically important material systems, namely, discontinuously reinforced aluminum composites containing silicon carbide particles as reinforcement, and boron modified titanium alloys containing in situ formed titanium boride whiskers. Microstructural attributes such as the shape, size, volume fraction, and spatial distribution of the reinforcement phase in these materials were incorporated in the models without any simplifying assumptions. Instrumented indentation was used to determine the constitutive properties of individual microstructural phases. Micromechanical analyses were performed using realistic 2D and 3D models and the results were compared with experimental data. Results indicated that 2D models fail to capture the deformation behavior of these materials and 3D analyses are required for realistic simulations. The effect of clustering of silicon carbide particles and associated porosity on the mechanical response of discontinuously reinforced aluminum composites was investigated using 3D models. Parametric studies were carried out using computer simulated microstructures incorporating realistic microstructural attributes. The intrinsic merit of this research is the development and integration of the required enabling techniques and methodologies for representation, modeling, and simulations of complex geometry of microstructures in two- and three-dimensional space facilitating better understanding of the effects of microstructural geometry on the mechanical behavior of materials.

Uncertainty in the modelling of spatial and temporal patterns of shallow groundwater flow paths: The role of geological and hydrological site information

NASA Astrophysics Data System (ADS)

Woodward, Simon J. R.; Wöhling, Thomas; Stenger, Roland

2016-03-01

Understanding the hydrological and hydrogeochemical responses of hillslopes and other small scale groundwater systems requires mapping the velocity and direction of groundwater flow relative to the controlling subsurface material features. Since point observations of subsurface materials and groundwater head are often the basis for modelling these complex, dynamic, three-dimensional systems, considerable uncertainties are inevitable, but are rarely assessed. This study explored whether piezometric head data measured at high spatial and temporal resolution over six years at a hillslope research site provided sufficient information to determine the flow paths that transfer nitrate leached from the soil zone through the shallow saturated zone into a nearby wetland and stream. Transient groundwater flow paths were modelled using MODFLOW and MODPATH, with spatial patterns of hydraulic conductivity in the three material layers at the site being estimated by regularised pilot point calibration using PEST, constrained by slug test estimates of saturated hydraulic conductivity at several locations. Subsequent Null Space Monte Carlo uncertainty analysis showed that this data was not sufficient to definitively determine the spatial pattern of hydraulic conductivity at the site, although modelled water table dynamics matched the measured heads with acceptable accuracy in space and time. Particle tracking analysis predicted that the saturated flow direction was similar throughout the year as the water table rose and fell, but was not aligned with either the ground surface or subsurface material contours; indeed the subsurface material layers, having relatively similar hydraulic properties, appeared to have little effect on saturated water flow at the site. Flow path uncertainty analysis showed that, while accurate flow path direction or velocity could not be determined on the basis of the available head and slug test data alone, the origin of well water samples relative to the material layers and site contour could still be broadly deduced. This study highlights both the challenge of collecting suitably informative field data with which to characterise subsurface hydrology, and the power of modern calibration and uncertainty modelling techniques to assess flow path uncertainty in hillslopes and other small scale systems.

Nonlinear dynamic modeling for smart material electro-hydraulic actuator development

NASA Astrophysics Data System (ADS)

Larson, John P.; Dapino, Marcelo J.

2013-03-01

Smart material electro-hydraulic actuators use hydraulic rectification by one-way check valves to amplify the motion of smart materials, such as magnetostrictives and piezoelectrics, in order to create compact, lightweight actuators. A piston pump driven by a smart material is combined with a hydraulic cylinder to form a self-contained, power-by-wire actuator that can be used in place of a conventional hydraulic system without the need for hydraulic lines and a centralized pump. The performance of an experimental actuator driven by a 12.7 mm diameter, 114 mm length Terfenol-D rod is evaluated over a range of applied input frequencies, loads, and currents. The peak performance achieved is 37 W, moving a 220 N load at a rate of 17 cm/s and producing a blocked pressure of 12.5 MPa. Additional tests are conducted to quantify the dynamic behavior of the one-way reed valves using a scanning laser vibrometer to identify the frequency response of the reeds and the effect of the valve seat and fluid mass loading. A lumped-parameter model is developed for the system that includes valve inertia and fluid response nonlinearities, and the model results are compared with the experimental data.

Parametric model of servo-hydraulic actuator coupled with a nonlinear system: Experimental validation

NASA Astrophysics Data System (ADS)

Maghareh, Amin; Silva, Christian E.; Dyke, Shirley J.

2018-05-01

Hydraulic actuators play a key role in experimental structural dynamics. In a previous study, a physics-based model for a servo-hydraulic actuator coupled with a nonlinear physical system was developed. Later, this dynamical model was transformed into controllable canonical form for position tracking control purposes. For this study, a nonlinear device is designed and fabricated to exhibit various nonlinear force-displacement profiles depending on the initial condition and the type of materials used as replaceable coupons. Using this nonlinear system, the controllable canonical dynamical model is experimentally validated for a servo-hydraulic actuator coupled with a nonlinear physical system.

A Simplified Model of Moisture Transport in Hydrophilic Porous Media With Applications to Pharmaceutical Tablets.

PubMed

Klinzing, Gerard R; Zavaliangos, Antonios

2016-08-01

This work establishes a predictive model that explicitly recognizes microstructural parameters in the description of the overall mass uptake and local gradients of moisture into tablets. Model equations were formulated based on local tablet geometry to describe the transient uptake of moisture. An analytical solution to a simplified set of model equations was solved to predict the overall mass uptake and moisture gradients with the tablets. The analytical solution takes into account individual diffusion mechanisms in different scales of porosity and diffusion into the solid phase. The time constant of mass uptake was found to be a function of several key material properties, such as tablet relative density, pore tortuosity, and equilibrium moisture content of the material. The predictions of the model are in excellent agreement with experimental results for microcrystalline cellulose tablets without the need for parameter fitting. The model presented provides a new method to analyze the transient uptake of moisture into hydrophilic materials with the knowledge of only a few fundamental material and microstructural parameters. In addition, the model allows for quick and insightful predictions of moisture diffusion for a variety of practical applications including pharmaceutical tablets, porous polymer systems, or cementitious materials. Copyright © 2016 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

Fracture of Carbon Nanotube - Amorphous Carbon Composites: Molecular Modeling

NASA Technical Reports Server (NTRS)

Jensen, Benjamin D.; Wise, Kristopher E.; Odegard, Gregory M.

2015-01-01

Carbon nanotubes (CNTs) are promising candidates for use as reinforcements in next generation structural composite materials because of their extremely high specific stiffness and strength. They cannot, however, be viewed as simple replacements for carbon fibers because there are key differences between these materials in areas such as handling, processing, and matrix design. It is impossible to know for certain that CNT composites will represent a significant advance over carbon fiber composites before these various factors have been optimized, which is an extremely costly and time intensive process. This work attempts to place an upper bound on CNT composite mechanical properties by performing molecular dynamics simulations on idealized model systems with a reactive forcefield that permits modeling of both elastic deformations and fracture. Amorphous carbon (AC) was chosen for the matrix material in this work because of its structural simplicity and physical compatibility with the CNT fillers. It is also much stiffer and stronger than typical engineering polymer matrices. Three different arrangements of CNTs in the simulation cell have been investigated: a single-wall nanotube (SWNT) array, a multi-wall nanotube (MWNT) array, and a SWNT bundle system. The SWNT and MWNT array systems are clearly idealizations, but the SWNT bundle system is a step closer to real systems in which individual tubes aggregate into large assemblies. The effect of chemical crosslinking on composite properties is modeled by adding bonds between the CNTs and AC. The balance between weakening the CNTs and improving fiber-matrix load transfer is explored by systematically varying the extent of crosslinking. It is, of course, impossible to capture the full range of deformation and fracture processes that occur in real materials with even the largest atomistic molecular dynamics simulations. With this limitation in mind, the simulation results reported here provide a plausible upper limit on achievable CNT composite properties and yield some insight on the influence of processing conditions on the mechanical properties of CNT composites.

Verification of a Finite Element Model for Pyrolyzing Ablative Materials

NASA Technical Reports Server (NTRS)

Risch, Timothy K.

2017-01-01

Ablating thermal protection system (TPS) materials have been used in many reentering spacecraft and in other applications such as rocket nozzle linings, fire protection materials, and as countermeasures for directed energy weapons. The introduction of the finite element model to the analysis of ablation has arguably resulted in improved computational capabilities due the flexibility and extended applicability of the method, especially to complex geometries. Commercial finite element codes often provide enhanced capability compared to custom, specially written programs based on versatility, usability, pre- and post-processing, grid generation, total life-cycle costs, and speed.

Simulation of charge transfer and orbital rehybridization in molecular and condensed matter systems

NASA Astrophysics Data System (ADS)

Nistor, Razvan A.

The mixing and shifting of electronic orbitals in molecules, or between atoms in bulk systems, is crucially important to the overall structure and physical properties of materials. Understanding and accurately modeling these orbital interactions is of both scientific and industrial relevance. Electronic orbitals can be perturbed in several ways. Doping, adding or removing electrons from systems, can change the bond-order and the physical properties of certain materials. Orbital rehybridization, driven by either thermal or pressure excitation, alters the short-range structure of materials and changes their long-range transport properties. Macroscopically, during bond formation, the shifting of electronic orbitals can be interpreted as a charge transfer phenomenon, as electron density may pile up around, and hence, alter the effective charge of, a given atom in the changing chemical environment. Several levels of theory exist to elucidate the mechanisms behind these orbital interactions. Electronic structure calculations solve the time-independent Schrodinger equation to high chemical accuracy, but are computationally expensive and limited to small system sizes and simulation times. Less fundamental atomistic calculations use simpler parameterized functional expressions called force-fields to model atomic interactions. Atomistic simulations can describe systems and time-scales larger and longer than electronic-structure methods, but at the cost of chemical accuracy. In this thesis, both first-principles and phenomenological methods are addressed in the study of several encompassing problems dealing with charge transfer and orbital rehybridization. Firstly, a new charge-equilibration method is developed that improves upon existing models to allow next-generation force-fields to describe the electrostatics of changing chemical environments. Secondly, electronic structure calculations are used to investigate the doping dependent energy landscapes of several high-temperature superconducting materials in order to parameterize the apparently large nonlinear electron-phonon coupling. Thirdly, ab initio simulations are used to investigate the role of pressure-driven structural re-organization in the crystalline-to-amorphous (or, metallic-to-insulating) transition of a common binary phase-change material composed of Ge and Sb. Practical applications of each topic will be discussed. Keywords. Charge-equilibration methods, molecular dynamics, electronic structure calculations, ab initio simulations, high-temperature superconductors, phase-change materials.

Nonassociative plasticity model for cohesionless materials and its implementation in soil-structure interaction

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

Hashmi, Q.S.E.

A constitutive model based on rate-independent elastoplasticity concepts is developed and used to simulate the behavior of geologic materials under arbitrary three-dimensional stress paths. The model accounts for various factors such as friction, stress path, and stress history that influence the behavior of geologic materials. A hierarchical approach is adopted whereby models of progressively increasing sophistication are developed from a basic isotropic-hardening associate model. Nonassociativeness is introduced as correction or perturbation to the basic model. Deviation of normality of the plastic-strain increments to the yield surface F is captured through nonassociativeness. The plastic potential Q is obtained by applying amore » correction to F. This simplified approach restricts the number of extra parameters required to define the plastic potential Q. The material constants associated with the model are identified, and they are evaluated for three different sands (Leighton Buzzard, Munich and McCormick Ranch). The model is then verified by comparing predictions with laboratory tests from which the constants were found, and typical tests not used for finding the constants. Based on the above findings, a soil-footing system is analyzed using finite-element techniques.« less

Stress distribution retrieval in granular materials: A multi-scale model and digital image correlation measurements

NASA Astrophysics Data System (ADS)

Bruno, Luigi; Decuzzi, Paolo; Gentile, Francesco

2016-01-01

The promise of nanotechnology lies in the possibility of engineering matter on the nanoscale and creating technological interfaces that, because of their small scales, may directly interact with biological objects, creating new strategies for the treatment of pathologies that are otherwise beyond the reach of conventional medicine. Nanotechnology is inherently a multiscale, multiphenomena challenge. Fundamental understanding and highly accurate predictive methods are critical to successful manufacturing of nanostructured materials, bio/mechanical devices and systems. In biomedical engineering, and in the mechanical analysis of biological tissues, classical continuum approaches are routinely utilized, even if these disregard the discrete nature of tissues, that are an interpenetrating network of a matrix (the extra cellular matrix, ECM) and a generally large but finite number of cells with a size falling in the micrometer range. Here, we introduce a nano-mechanical theory that accounts for the-non continuum nature of bio systems and other discrete systems. This discrete field theory, doublet mechanics (DM), is a technique to model the mechanical behavior of materials over multiple scales, ranging from some millimeters down to few nanometers. In the paper, we use this theory to predict the response of a granular material to an external applied load. Such a representation is extremely attractive in modeling biological tissues which may be considered as a spatial set of a large number of particulate (cells) dispersed in an extracellular matrix. Possibly more important of this, using digital image correlation (DIC) optical methods, we provide an experimental verification of the model.

Report for MaRIE Drivers Workshop on needs for energetic material's studies.

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

Specht, Paul Elliott

Energetic materials (i.e. explosives, propellants, and pyrotechnics) have complex mesoscale features that influence their dynamic response. Direct measurement of the complex mechanical, thermal, and chemical response of energetic materials is critical for improving computational models and enabling predictive capabilities. Many of the physical phenomena of interest in energetic materials cover time and length scales spanning several orders of magnitude. Examples include chemical interactions in the reaction zone, the distribution and evolution of temperature fields, mesoscale deformation in heterogeneous systems, and phase transitions. This is particularly true for spontaneous phenomena, like thermal cook-off. The ability for MaRIE to capture multiple lengthmore » scales and stochastic phenomena can significantly advance our understanding of energetic materials and yield more realistic, predictive models.« less

Analysis of speckle and material properties in laider tracer

NASA Astrophysics Data System (ADS)

Ross, Jacob W.; Rigling, Brian D.; Watson, Edward A.

2017-04-01

The SAL simulation tool Laider Tracer models speckle: the random variation in intensity of an incident light beam across a rough surface. Within Laider Tracer, the speckle field is modeled as a 2-D array of jointly Gaussian random variables projected via ray tracing onto the scene of interest. Originally, all materials in Laider Tracer were treated as ideal diffuse scatterers, for which the far-field return computed uses the Lambertian Bidirectional Reflectance Distribution Function (BRDF). As presented here, we implement material properties into Laider Tracer via the Non-conventional Exploitation Factors Data System: a database of properties for thousands of different materials sampled at various wavelengths and incident angles. We verify the intensity behavior as a function of incident angle after material properties are added to the simulation.

Aluminum-26 in the early solar system - Fossil or fuel

NASA Technical Reports Server (NTRS)

Lee, T.; Papanastassiou, D. A.; Wasserburg, G. J.

1977-01-01

The isotopic composition of Mg was measured in different phases of a Ca-Al-rich inclusion in the Allende meteorite. Large excesses of Mg-26 of up to 10% were found. These excesses correlate strictly with the Al-27/Mg-24 ratio for four coexisting phases with distinctive chemical compositions. Models of in situ decay of Al-26 within the solar system and of mixing of interstellar dust grains containing fossil Al-26 with normal solar system material are presented. The observed correlation provides definitive evidence for the presence of Al-26 in the early solar system. This requires either injection of freshly synthesized nucleosynthetic material into the solar system immediately before condensation and planet formation, or local production within the solar system by intense activity of the early sun. Planets promptly produced from material with the inferred Al-26/Al-27 would melt within about 300,000 years.

Review of Development Survey of Phase Change Material Models in Building Applications

PubMed Central

Akeiber, Hussein J.; Wahid, Mazlan A.; Hussen, Hasanen M.; Mohammad, Abdulrahman Th.

2014-01-01

The application of phase change materials (PCMs) in green buildings has been increasing rapidly. PCM applications in green buildings include several development models. This paper briefly surveys the recent research and development activities of PCM technology in building applications. Firstly, a basic description of phase change and their principles is provided; the classification and applications of PCMs are also included. Secondly, PCM models in buildings are reviewed and discussed according to the wall, roof, floor, and cooling systems. Finally, conclusions are presented based on the collected data. PMID:25313367

Ablative Thermal Protection System Fundamentals

NASA Technical Reports Server (NTRS)

Beck, Robin A. S.

2013-01-01

This is the presentation for a short course on the fundamentals of ablative thermal protection systems. It covers the definition of ablation, description of ablative materials, how they work, how to analyze them and how to model them.

Course transformation: Content, structure and effectiveness analysis

NASA Astrophysics Data System (ADS)

DuHadway, Linda P.

The organization of learning materials is often limited by the systems available for delivery of such material. Currently, the learning management system (LMS) is widely used to distribute course materials. These systems deliver the material in a text-based, linear way. As online education continues to expand and educators seek to increase their effectiveness by adding more effective active learning strategies, these delivery methods become a limitation. This work demonstrates the possibility of presenting course materials in a graphical way that expresses important relations and provides support for manipulating the order of those materials. The ENABLE system gathers data from an existing course, uses text analysis techniques, graph theory, graph transformation, and a user interface to create and present graphical course maps. These course maps are able to express information not currently available in the LMS. Student agents have been developed to traverse these course maps to identify the variety of possible paths through the material. The temporal relations imposed by the current course delivery methods have been replaced by prerequisite relations that express ordering that provides educational value. Reducing the connections to these more meaningful relations allows more possibilities for change. Technical methods are used to explore and calibrate linear and nonlinear models of learning. These methods are used to track mastery of learning material and identify relative difficulty values. Several probability models are developed and used to demonstrate that data from existing, temporally based courses can be used to make predictions about student success in courses using the same material but organized without the temporal limitations. Combined, these demonstrate the possibility of tools and techniques that can support the implementation of a graphical course map that allows varied paths and provides an enriched, more informative interface between the educator, the student, and the learning material. This fundamental change in how course materials are presented and interfaced with has the potential to make educational opportunities available to a broader spectrum of people with diverse abilities and circumstances. The graphical course map can be pivotal in attaining this transition.

Update on Conformal Ablative Thermal Protection System for Planetary and Human Exploration Missions

NASA Astrophysics Data System (ADS)

Beck, R. A. S.; Arnold, J. O.; Gasch, M. J.; Stackpoole, M. M.; Venkatapathy, E.

2014-06-01

In FY13, more advanced testing and modeling of the new NASA conformal ablative TPS material was performed. Most notable were the 3- and 4-point bending tests and the aerothermal testing on seams and joints in shear. The material outperformed PICA.

Structural colored liquid membrane without angle dependence.

PubMed

Takeoka, Yukikazu; Honda, Masaki; Seki, Takahiro; Ishii, Masahiko; Nakamura, Hiroshi

2009-05-01

We have demonstrated for the first time that condensed gel particle suspensions in amorphous-like states display structural color with low angle dependence. This finding is in contrast to the common understanding that a periodic dielectric structure is fundamental to photonic band gap (PBG) production, and it validates the theory that a "tight bonding model" that is applicable to semiconductor systems can also be applied to photonic systems. More practically, this structural colored suspension represents a promising new material for the manufacture of reflective full-color displays with a wide viewing angle and nonfading color materials. This liquid system shows promise as a display material because electronic equipment used for display systems can easily be filled with the liquid in the same way that liquid crystals are currently used.

Modeling of Damage Initiation and Progression in a SiC/SiC Woven Ceramic Matrix Composite

NASA Technical Reports Server (NTRS)

Mital, Subodh K.; Goldberg, Robert K.; Bonacuse, Peter J.

2012-01-01

The goal of an ongoing project at NASA Glenn is to investigate the effects of the complex microstructure of a woven ceramic matrix composite and its variability on the effective properties and the durability of the material. Detailed analysis of these complex microstructures may provide clues for the material scientists who `design the material? or to structural analysts and designers who `design with the material? regarding damage initiation and damage propagation. A model material system, specifically a five-harness satin weave architecture CVI SiC/SiC composite composed of Sylramic-iBN fibers and a SiC matrix, has been analyzed. Specimens of the material were serially sectioned and polished to capture the detailed images of fiber tows, matrix and porosity. Open source analysis tools were used to isolate various constituents and finite elements models were then generated from simplified models of those images. Detailed finite element analyses were performed that examine how the variability in the local microstructure affected the macroscopic behavior as well as the local damage initiation and progression. Results indicate that the locations where damage initiated and propagated is linked to specific microstructural features.

Compressibility of the fluid

NASA Astrophysics Data System (ADS)

Jablonská, Jana

2014-03-01

The presence of air in the liquid causes the dynamic system behaviour. When solve to issue of the dynamics we often meet problems of cavitation. Cavitation is an undesirable phenomenon, since it causes a disruption of the surrounding material and material destruction. Cavitation is accompanied by loud sound effects and reduces the efficiency of such pumps, etc. Therefore, it is desirable to model systems in which the cavitation might occur. A typical example is a solution of water hammer.

Understanding and modeling the economics of ECM

NASA Astrophysics Data System (ADS)

Wells, Wayne E.; Edinbarough, Immanuel A.

2004-12-01

Traditional economic analysis methods for manufacturing decisions include only the clearly identified immediate cost and revenue streams. Environmental issues have generally been seen as costs, in the form of waste material losses, conformance tests and pre-discharge treatments. The components of the waste stream often purchased as raw materials, become liabilities at the "end of the pipe" and their intrinsic material value is seldom recognized. A new mathematical treatment of manufacturing economics is proposed in which the costs of separation are compared with the intrinsic value of the waste materials to show how their recovery can provide an economic advantage to the manufacturer. The model is based on a unique combination of thermodynamic analysis, economic modeling and linear optimization. This paper describes the proposed model, and examines case studies in which the changed decision rules have yielded significant savings while protecting the environment. The premise proposed is that by including the value of the waste materials in the profit objective of the firm and applying the appropriate technological solution, manufacturing processes can become closed systems in which losses approach zero and environmental problems are converted into economic savings.

The patterning center of excellence (CoE): an evolving lithographic enablement model

NASA Astrophysics Data System (ADS)

Montgomery, Warren; Chun, Jun Sung; Liehr, Michael; Tittnich, Michael

2015-03-01

As EUV lithography moves toward high-volume manufacturing (HVM), a key need for the lithography materials makers is access to EUV photons and imaging. The SEMATECH Resist Materials Development Center (RMDC) provided a solution path by enabling the Resist and Materials companies to work together (using SUNY Polytechnic Institute's Colleges of Nanoscale Science and Engineering (SUNY Poly CNSE) -based exposure systems), in a consortium fashion, in order to address the need for EUV photons. Thousands of wafers have been processed by the RMDC (leveraging the SUNY Poly CNSE/SEMATECH MET, SUNY Poly CNSE Alpha Demo Tool (ADT) and the SEMATECH Lawrence Berkeley MET) allowing many of the questions associated with EUV materials development to be answered. In this regard the activities associated with the RMDC are continuing. As the major Integrated Device Manufacturers (IDMs) have continued to purchase EUV scanners, Materials companies must now provide scanner based test data that characterizes the lithography materials they are producing. SUNY Poly CNSE and SEMATECH have partnered to evolve the RMDC into "The Patterning Center of Excellence (CoE)". The new CoE leverages the capability of the SUNY Poly CNSE-based full field ASML 3300 EUV scanner and combines that capability with EUV Microexposure (MET) systems resident in the SEMATECH RMDC to create an integrated lithography model which will allow materials companies to advance materials development in ways not previously possible.

Intelligent system of coordination and control for manufacturing

NASA Astrophysics Data System (ADS)

Ciortea, E. M.

2016-08-01

This paper wants shaping an intelligent system monitoring and control, which leads to optimizing material and information flows of the company. The paper presents a model for tracking and control system using intelligent real. Production system proposed for simulation analysis provides the ability to track and control the process in real time. Using simulation models be understood: the influence of changes in system structure, commands influence on the general condition of the manufacturing process conditions influence the behavior of some system parameters. Practical character consists of tracking and real-time control of the technological process. It is based on modular systems analyzed using mathematical models, graphic-analytical sizing, configuration, optimization and simulation.

Object-Oriented Modeling of an Energy Harvesting System Based on Thermoelectric Generators

NASA Astrophysics Data System (ADS)

Nesarajah, Marco; Frey, Georg

This paper deals with the modeling of an energy harvesting system based on thermoelectric generators (TEG), and the validation of the model by means of a test bench. TEGs are capable to improve the overall energy efficiency of energy systems, e.g. combustion engines or heating systems, by using the remaining waste heat to generate electrical power. Previously, a component-oriented model of the TEG itself was developed in Modelica® language. With this model any TEG can be described and simulated given the material properties and the physical dimension. Now, this model was extended by the surrounding components to a complete model of a thermoelectric energy harvesting system. In addition to the TEG, the model contains the cooling system, the heat source, and the power electronics. To validate the simulation model, a test bench was built and installed on an oil-fired household heating system. The paper reports results of the measurements and discusses the validity of the developed simulation models. Furthermore, the efficiency of the proposed energy harvesting system is derived and possible improvements based on design variations tested in the simulation model are proposed.

Thermohydrology of fractured geologic materials

NASA Astrophysics Data System (ADS)

Esh, David Whittaker

1998-11-01

Thermohydrological and thermohydrochemical modeling as applied to the disposal of radioactive materials in a geologic repository is presented. Site hydrology, chemistry, and mineralogy were summarized and conceptual models of the fundamental system processes were developed. The numerical model TOUGH2 was used to complete computer simulations of thermohydrological processes in fractured, geologic media. Sensitivity studies investigating the impact of dimensionality and different conceptual models to represent fractures (ECM, DK, MINC) on thermohydrological response were developed. Sensitivity to parameter variation within a given conceptual model was also considered. The sensitivity of response was examined against thermohydrological metrics derived from the flow and redistribution of moisture. A simple thermohydrochemical model to investigate a three-process coupling (thermal-hydrological-chemical) was presented. The redistribution of chloride was evaluated because the chemical behavior is well known and defensible. In addition, it is very important to overall system performance. For all of the simulations completed, chloride was found to be extremely concentrated in the fluids that eventually return to the engineered barrier system. Chloride concentration and mass flux were increased from ambient by over a factor of 1000 for some simulations. Thermohydrology was found to have the potential to significantly alter chemistry from ambient conditions.

Biomechanically based simulation of brain deformations for intraoperative image correction: coupling of elastic and fluid models

NASA Astrophysics Data System (ADS)

Hagemann, Alexander; Rohr, Karl; Stiehl, H. Siegfried

2000-06-01

In order to improve the accuracy of image-guided neurosurgery, different biomechanical models have been developed to correct preoperative images w.r.t. intraoperative changes like brain shift or tumor resection. All existing biomechanical models simulate different anatomical structures by using either appropriate boundary conditions or by spatially varying material parameter values, while assuming the same physical model for all anatomical structures. In general, this leads to physically implausible results, especially in the case of adjacent elastic and fluid structures. Therefore, we propose a new approach which allows to couple different physical models. In our case, we simulate rigid, elastic, and fluid regions by using the appropriate physical description for each material, namely either the Navier equation or the Stokes equation. To solve the resulting differential equations, we derive a linear matrix system for each region by applying the finite element method (FEM). Thereafter, the linear matrix systems are linked together, ending up with one overall linear matrix system. Our approach has been tested using synthetic as well as tomographic images. It turns out from experiments, that the integrated treatment of rigid, elastic, and fluid regions significantly improves the prediction results in comparison to a pure linear elastic model.

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

Yang, Yongsoo; Chen, Chien-Chun; Scott, M. C.

Perfect crystals are rare in nature. Real materials often contain crystal defects and chemical order/disorder such as grain boundaries, dislocations, interfaces, surface reconstructions and point defects. Such disruption in periodicity strongly affects material properties and functionality. Despite rapid development of quantitative material characterization methods, correlating three-dimensional (3D) atomic arrangements of chemical order/disorder and crystal defects with material properties remains a challenge. On a parallel front, quantum mechanics calculations such as density functional theory (DFT) have progressed from the modelling of ideal bulk systems to modelling ‘real’ materials with dopants, dislocations, grain boundaries and interfaces; but these calculations rely heavily onmore » average atomic models extracted from crystallography. To improve the predictive power of first-principles calculations, there is a pressing need to use atomic coordinates of real systems beyond average crystallographic measurements. Here we determine the 3D coordinates of 6,569 iron and 16,627 platinum atoms in an iron-platinum nanoparticle, and correlate chemical order/disorder and crystal defects with material properties at the single-atom level. We identify rich structural variety with unprecedented 3D detail including atomic composition, grain boundaries, anti-phase boundaries, anti-site point defects and swap defects. We show that the experimentally measured coordinates and chemical species with 22 picometre precision can be used as direct input for DFT calculations of material properties such as atomic spin and orbital magnetic moments and local magnetocrystalline anisotropy. The work presented here combines 3D atomic structure determination of crystal defects with DFT calculations, which is expected to advance our understanding of structure–property relationships at the fundamental level.« less

Phase 1 of the First Solar Small Power System Experiment (experimental System No. 1). Volume 3: Appendix E - N

NASA Technical Reports Server (NTRS)

Clark, T. B. (Editor)

1979-01-01

The design of a solar electric power plant for a small community is reported. Topics covered include: (1) control configurations and interface requirements for the baseline power system; (2) annual small power system output; (3) energy requirements for operation of the collectors and control building; (4) life cycle costs and reliability predictions; (5) thermal conductivities and costs of receiver insulation materials; (6) transient thermal modelling for the baseline receiver/thermal transport system under normal and inclement operating conditions; (7) high temperature use of sodium; (8) shading in a field of parabolic collectors; and (9) buffer storage materials.

Multi-disciplinary coupling effects for integrated design of propulsion systems

NASA Technical Reports Server (NTRS)

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

1993-01-01

Effective computational simulation procedures are described for modeling the inherent multi-disciplinary interactions which govern the accurate response of propulsion systems. Results are presented for propulsion system responses including multi-disciplinary coupling effects using coupled multi-discipline thermal, structural, and acoustic tailoring; an integrated system of multi-disciplinary simulators; coupled material behavior/fabrication process tailoring; sensitivities using a probabilistic simulator; and coupled materials, structures, fracture, and probabilistic behavior simulator. The results demonstrate that superior designs can be achieved if the analysis/tailoring methods account for the multi-disciplinary coupling effects. The coupling across disciplines can be used to develop an integrated coupled multi-discipline numerical propulsion system simulator.

Multi-disciplinary coupling for integrated design of propulsion systems

NASA Technical Reports Server (NTRS)

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

1993-01-01

Effective computational simulation procedures are described for modeling the inherent multi-disciplinary interactions for determining the true response of propulsion systems. Results are presented for propulsion system responses including multi-discipline coupling effects via (1) coupled multi-discipline tailoring, (2) an integrated system of multidisciplinary simulators, (3) coupled material-behavior/fabrication-process tailoring, (4) sensitivities using a probabilistic simulator, and (5) coupled materials/structures/fracture/probabilistic behavior simulator. The results show that the best designs can be determined if the analysis/tailoring methods account for the multi-disciplinary coupling effects. The coupling across disciplines can be used to develop an integrated interactive multi-discipline numerical propulsion system simulator.

Research and Development for Novel Thermal Energy Storage Systems (TES) for Concentrating Solar Power (CSP)

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

Faghri, Amir; Bergman, Theodore L; Pitchumani, Ranga

2013-09-26

The overall objective was to develop innovative heat transfer devices and methodologies for novel thermal energy storage systems for concentrating solar power generation involving phase change materials (PCMs). Specific objectives included embedding thermosyphons and/or heat pipes (TS/HPs) within appropriate phase change materials to significantly reduce thermal resistances within the thermal energy storage system of a large-scale concentrating solar power plant and, in turn, improve performance of the plant. Experimental, system level and detailed comprehensive modeling approaches were taken to investigate the effect of adding TS/HPs on the performance of latent heat thermal energy storage (LHTES) systems.

Ballistic Performance of Porous-Ceramic, Thermal-Protection-Systems

NASA Technical Reports Server (NTRS)

Christiansen, E. L.; Davis, B. A.; Miller, J. E.; Bohl, W. E.; Foreman, C. D.

2009-01-01

Porous-ceramic, thermal protection systems are used heavily in current reentry vehicles like the Space Shuttle and are currently being proposed for the next generation of manned spacecraft, Orion. These materials insulate the structural components of a spacecraft against the intense thermal environments of atmospheric reentry. Furthermore, these materials are also highly exposed to space environmental hazards like meteoroid and orbital debris impacts. This paper discusses recent impact testing up to 9 km/s, and the findings of the influence of material equation-of-state on the simulation of the impact event to characterize the ballistic performance of these materials. These results will be compared with heritage models1 for these materials developed from testing at lower velocities. Assessments of predicted spacecraft risk based upon these tests and simulations will also be discussed.

Interdisciplinary Pathways for Urban Metabolism Research

NASA Astrophysics Data System (ADS)

Newell, J. P.

2011-12-01

With its rapid rise as a metaphor to express coupled natural-human systems in cities, the concept of urban metabolism is evolving into a series of relatively distinct research frameworks amongst various disciplines, with varying definitions, theories, models, and emphases. In industrial ecology, housed primarily within the disciplinary domain of engineering, urban metabolism research has focused on quantifying material and energy flows into, within, and out of cities, using methodologies such as material flow analysis and life cycle assessment. In the field of urban ecology, which is strongly influenced by ecology and urban planning, research focus has been placed on understanding and modeling the complex patterns and processes of human-ecological systems within urban areas. Finally, in political ecology, closely aligned with human geography and anthropology, scholars theorize about the interwoven knots of social and natural processes, material flows, and spatial structures that form the urban metabolism. This paper offers three potential interdisciplinary urban metabolism research tracks that might integrate elements of these three "ecologies," thereby bridging engineering and the social and physical sciences. First, it presents the idea of infrastructure ecology, which explores the complex, emergent interdependencies between gray (water and wastewater, transportation, etc) and green (e.g. parks, greenways) infrastructure systems, as nested within a broader socio-economic context. For cities to be sustainable and resilient over time-space, the theory follows, these is a need to understand and redesign these infrastructure linkages. Second, there is the concept of an urban-scale carbon metabolism model which integrates consumption-based material flow analysis (including goods, water, and materials), with the carbon sink and source dynamics of the built environment (e.g. buildings, etc) and urban ecosystems. Finally, there is the political ecology of the material urban metabolism, which adds spatial differentiation to materials flows and form, as well as a focus on equity, access, and governance dimensions of the urban metabolism.

A phase field dislocation dynamics model for a bicrystal interface system: An investigation into dislocation slip transmission across cube-on-cube interfaces

DOE PAGES

Zeng, Y.; Hunter, A.; Beyerlein, I. J.; ...

2015-09-14

In this study, we present a phase field dislocation dynamics formulation designed to treat a system comprised of two materials differing in moduli and lattice parameters that meet at a common interface. We apply the model to calculate the critical stress τ crit required to transmit a perfect dislocation across the bimaterial interface with a cube-on-cube orientation relationship. The calculation of τ crit accounts for the effects of: 1) the lattice mismatch (misfit or coherency stresses), 2) the elastic moduli mismatch (Koehler forces or image stresses), and 3) the formation of the residual dislocation in the interface. Our results showmore » that the value of τ crit associated with the transmission of a dislocation from material 1 to material 2 is not the same as that from material 2 to material 1. Dislocation transmission from the material with the lower shear modulus and larger lattice parameter tends to be easier than the reverse and this apparent asymmetry in τ crit generally increases with increases in either lattice or moduli mismatch or both. In efforts to clarify the roles of lattice and moduli mismatch, we construct an analytical model for τcrit based on the formation energy of the residual dislocation. We show that path dependence in this energetic barrier can explain the asymmetry seen in the calculated τ crit values.« less

Two phase modeling of the influence of plastic strain on the magnetic and magnetostrictive behaviors of ferromagnetic materials

NASA Astrophysics Data System (ADS)

Hubert, Olivier; Lazreg, Said

2017-02-01

A growing interest of automotive industry in the use of high performance steels is observed. These materials are obtained thanks to complex manufacturing processes whose parameters fluctuations lead to strong variations of microstructure and mechanical properties. The on-line magnetic non-destructive monitoring is a relevant response to this problem but it requires fast models sensitive to different parameters of the forming process. The plastic deformation is one of these important parameters. Indeed, ferromagnetic materials are known to be sensitive to stress application and especially to plastic strains. In this paper, a macroscopic approach using the kinematic hardening is proposed to model this behavior, considering a plastic strained material as a two phase system. Relationship between kinematic hardening and residual stress is defined in this framework. Since stress fields are multiaxial, an uniaxial equivalent stress is calculated and introduced inside the so-called magneto-mechanical multidomain modeling to represent the effect of plastic strain. The modeling approach is complemented by many experiments involving magnetic and magnetostrictive measurements. They are carried out with or without applied stress, using a dual-phase steel deformed at different levels. The main interest of this material is that the mechanically hard phase, soft phase and the kinematic hardening can be clearly identified thanks to simple experiments. It is shown how this model can be extended to single phase materials.

A viscoelastic model for dielectric elastomers based on a continuum mechanical formulation and its finite element implementation

NASA Astrophysics Data System (ADS)

Bueschel, A.; Klinkel, S.; Wagner, W.

2011-04-01

Smart materials are active and multifunctional materials, which play an important part for sensor and actuator applications. These materials have the potential to transform passive structures into adaptive systems. However, a prerequisite for the design and the optimization of these materials is, that reliable models exist, which incorporate the interaction between the different combinations of thermal, electrical, magnetic, optical and mechanical effects. Polymeric electroelastic materials, so-called electroactive polymer (EAP), own the characteristic to deform if an electric field is applied. EAP's possesses the benefit that they share the characteristic of polymers, these are lightweight, inexpensive, fracture tolerant, elastic, and the chemical and physical structure is well understood. However, the description "electroactive polymer" is a generic term for many kinds of different microscopic mechanisms and polymeric materials. Based on the laws of electromagnetism and elasticity, a visco-electroelastic model is developed and implemented into the finite element method (FEM). The presented three-dimensional solid element has eight nodes and trilinear interpolation functions for the displacement and the electric potential. The continuum mechanics model contains finite deformations, the time dependency and the nearly incompressible behavior of the material. To describe the possible, large time dependent deformations, a finite viscoelastic model with a split of the deformation gradient is used. Thereby the time dependent characteristic of polymeric materials is incorporated through the free energy function. The electromechanical interactions are considered by the electrostatic forces and inside the energy function.

Mathematical modeling of a process the rolling delivery

NASA Astrophysics Data System (ADS)

Stepanov, Mikhail A.; Korolev, Andrey A.

2018-03-01

An adduced analysis of the scientific researches in a domain of the rolling equipments, also research of properties the working material. A one of perspective direction of scientific research this is mathematical modeling. That is broadly used in many scientific disciplines and especially at the technical, applied sciences. With the aid of mathematical modeling it can be study of physical properties of the researching objects and systems. A research of the rolling delivery and transporting devices realized with the aid of a construction of mathematical model of appropriate process. To be described the basic principles and conditions of a construction of mathematical models of the real objects. For example to be consider a construction of mathematical model the rolling delivery device. For a construction that is model used system of the equations, which consist of: Lagrange’s equation of a motion, describing of the law conservation of energy of a mechanical system, and the Navier - Stokes equations, which characterize of the flow of a continuous non-compressed fluid. A construction of mathematical model the rolling deliver to let determined of a total energy of device, and therefore to got the dependence upon the power of drive to a gap between of rolls. A corroborate the hypothesis about laminar the flow of a material into the rolling gap of deliver.

Screening of pollution control and clean-up materials for river chemical spills using the multiple case-based reasoning method with a difference-driven revision strategy.

PubMed

Liu, Rentao; Jiang, Jiping; Guo, Liang; Shi, Bin; Liu, Jie; Du, Zhaolin; Wang, Peng

2016-06-01

In-depth filtering of emergency disposal technology (EDT) and materials has been required in the process of environmental pollution emergency disposal. However, an urgent problem that must be solved is how to quickly and accurately select the most appropriate materials for treating a pollution event from the existing spill control and clean-up materials (SCCM). To meet this need, the following objectives were addressed in this study. First, the material base and a case base for environment pollution emergency disposal were established to build a foundation and provide material for SCCM screening. Second, the multiple case-based reasoning model method with a difference-driven revision strategy (DDRS-MCBR) was applied to improve the original dual case-based reasoning model method system, and screening and decision-making was performed for SCCM using this model. Third, an actual environmental pollution accident from 2012 was used as a case study to verify the material base, case base, and screening model. The results demonstrated that the DDRS-MCBR method was fast, efficient, and practical. The DDRS-MCBR method changes the passive situation in which the choice of SCCM screening depends only on the subjective experience of the decision maker and offers a new approach to screening SCCM.

Review of the synergies between computational modeling and experimental characterization of materials across length scales

DOE PAGES

Dingreville, Rémi; Karnesky, Richard A.; Puel, Guillaume; ...

2015-11-16

With the increasing interplay between experimental and computational approaches at multiple length scales, new research directions are emerging in materials science and computational mechanics. Such cooperative interactions find many applications in the development, characterization and design of complex material systems. This manuscript provides a broad and comprehensive overview of recent trends in which predictive modeling capabilities are developed in conjunction with experiments and advanced characterization to gain a greater insight into structure–property relationships and study various physical phenomena and mechanisms. The focus of this review is on the intersections of multiscale materials experiments and modeling relevant to the materials mechanicsmore » community. After a general discussion on the perspective from various communities, the article focuses on the latest experimental and theoretical opportunities. Emphasis is given to the role of experiments in multiscale models, including insights into how computations can be used as discovery tools for materials engineering, rather than to “simply” support experimental work. This is illustrated by examples from several application areas on structural materials. In conclusion this manuscript ends with a discussion on some problems and open scientific questions that are being explored in order to advance this relatively new field of research.« less

A two reservoir model to predict Escherichia coli losses to water from pastures grazed by dairy cows.

PubMed

Muirhead, R W; Monaghan, R M

2012-04-01

Animal agriculture has been identified as an important source of diffuse faecal microbial pollution of water. Our current understanding of the losses of faecal microbes from grazed pasture systems is however poor. To help synthesise our current knowledge, a simple two reservoir model was constructed to represent the faecal and environmental sources of Escherichia coli found in a grazed pastoral system. The size of the faecal reservoir was modelled on a daily basis with inputs from grazing animals, and losses due to die-off of E. coli and decomposition of the faecal material. Estimates were made of transport coefficients of E. coli losses from the two reservoirs. The concentration of E. coli measured in overland flow and artificial drainage from grazed plots, used for calibration of the model, showed a significant (P<0.0001) decrease with days since last grazing - up to 120 days. Modelled E. coli runoff concentrations calibrated well with the regression line from the measured data up to 120 days. Variability of E. coli concentrations in the source faecal material could account for the variability in the measured runoff concentrations. Measured E. coli concentrations in artificial drainage water from 120 to 1300 days since last grazing appeared to be greater than the model predicted. The longer term data clearly illustrated the need for an environmental reservoir of E. coli in models of grazed pasture systems. Research is needed to understand the behaviour and impact of this environmental reservoir. Scenario analysis using the model indicated that rather than manipulating the faecal material itself post defecation, mitigation options should focus on manipulating grazing management. Copyright © 2011 Elsevier Ltd. All rights reserved.

ISS Material Science Research Rack HWIL Interface Simulation

NASA Technical Reports Server (NTRS)

Williams, Philip J.; Ballard, Gary H.; Crumbley, Robert T. (Technical Monitor)

2002-01-01

In this paper, the first Material Science Research Rack (MSRR-1) hardware-in-the-loop (HWIL) interface simulation is described. Dynamic Concepts developed this HWIL simulation system with funding and management provided by the Flight Software group (ED14) of NASA-MSFC's Avionics Department. The HWIL system has been used both as a flight software development environment and as a software qualification tool. To fulfill these roles, the HWIL simulator accurately models the system dynamics of many MSRR-1 subsystems and emulates most of the internal interface signals. The modeled subsystems include the Experiment Modules, the Thermal Environment Control System, the Vacuum Access System, the Solid State Power Controller Module, and the Active Rack Isolation Systems. The emulated signals reside on three separate MIL-STD-1553B digital communication buses, the ISS Medium Rate Data Link, and several analog controller and sensor signals. To enhance the range of testing, it was necessary to simulate several off-nominal conditions that may occur in the interfacing subsystems.

Retardation analytical model to extend service life

NASA Technical Reports Server (NTRS)

Matejczyk, J.

1984-01-01

A fatigue crack growth model that incorporates crack growth retardation effects and is applicable to the materials characteristics and service environments of high performance LH2/LO2 engine systems is discussed. Future Research plans are outlined.

Deciphering chemical order/disorder and material properties at the single-atom level

DOE PAGES

Yang, Yongsoo; Chen, Chien-Chun; Scott, M. C.; ...

2017-02-01

Perfect crystals are rare in nature. Real materials often contain crystal defects and chemical order/disorder such as grain boundaries, dislocations, interfaces, surface reconstructions and point defects. Such disruption in periodicity strongly affects material properties and functionality. Despite rapid development of quantitative material characterization methods, correlating three-dimensional (3D) atomic arrangements of chemical order/disorder and crystal defects with material properties remains a challenge. On a parallel front, quantum mechanics calculations such as density functional theory (DFT) have progressed from the modelling of ideal bulk systems to modelling ‘real’ materials with dopants, dislocations, grain boundaries and interfaces; but these calculations rely heavily onmore » average atomic models extracted from crystallography. To improve the predictive power of first-principles calculations, there is a pressing need to use atomic coordinates of real systems beyond average crystallographic measurements. Here we determine the 3D coordinates of 6,569 iron and 16,627 platinum atoms in an iron-platinum nanoparticle, and correlate chemical order/disorder and crystal defects with material properties at the single-atom level. We identify rich structural variety with unprecedented 3D detail including atomic composition, grain boundaries, anti-phase boundaries, anti-site point defects and swap defects. We show that the experimentally measured coordinates and chemical species with 22 picometre precision can be used as direct input for DFT calculations of material properties such as atomic spin and orbital magnetic moments and local magnetocrystalline anisotropy. The work presented here combines 3D atomic structure determination of crystal defects with DFT calculations, which is expected to advance our understanding of structure–property relationships at the fundamental level.« less

Method for the thermal characterization, visualization, and integrity evaluation of conducting material samples or complex structures

DOEpatents

Ortiz, Marcos G.

1992-01-01

A method for modeling a conducting material sample or structure (herein called a system) as at least two regions which comprise an electrical network of resistances, for measuring electric resistance between at least two selected pairs of external leads attached to the surface of the system, wherein at least one external lead is attached to the surface of each of the regions, and, using basic circuit theory, for translating measured resistances into temperatures or thermophysical properties in corresponding regions of the system.

Method for the thermal characterization, visualization, and integrity evaluation of conducting material samples or complex structures

DOEpatents

Ortiz, M.G.

1992-11-24

Disclosed is a method for modeling a conducting material sample or structure (herein called a system) as at least two regions which comprise an electrical network of resistances, for measuring electric resistance between at least two selected pairs of external leads attached to the surface of the system, wherein at least one external lead is attached to the surface of each of the regions, and, using basic circuit theory, for translating measured resistances into temperatures or thermophysical properties in corresponding regions of the system. 16 figs.

Thermal Protection System of the Space Shuttle

NASA Technical Reports Server (NTRS)

Cleland, John; Iannetti, Francesco

1989-01-01

The Thermal Protection System (TPS), introduced by NASA, continues to incorporate many of the advances in materials over the past two decades. A comprehensive, single-volume summary of the TPS, including system design rationales, key design features, and broad descriptions of the subsystems of TPS (E.g., reusable surface insulation, leading edge structural, and penetration subsystems) is provided. Details of all elements of TPS development and application are covered (materials properties, manufacturing, modeling, testing, installation, and inspection). Disclosures and inventions are listed and potential commercial application of TPS-related technology is discussed.

A SWOT analysis of the organization and financing of the Danish health care system.

PubMed

Christiansen, Terkel

2002-02-01

The organization and financing of the Danish health care system was evaluated within a framework of a SWOT analysis (analysis of Strengths, Weaknesses, Opportunities and Threats) by a panel of five members with a background in health economics. The present paper describes the methods and materials used for the evaluation: selection of panel members, structure of the evaluation task according to the health care triangle model, selection of background material consisting of documents and literature on the Danish health care system, and a 1-week study visit.

Surface characteristics modeling and performance evaluation of urban building materials using LiDAR data.

PubMed

Li, Xiaolu; Liang, Yu

2015-05-20

Analysis of light detection and ranging (LiDAR) intensity data to extract surface features is of great interest in remote sensing research. One potential application of LiDAR intensity data is target classification. A new bidirectional reflectance distribution function (BRDF) model is derived for target characterization of rough and smooth surfaces. Based on the geometry of our coaxial full-waveform LiDAR system, the integration method is improved through coordinate transformation to establish the relationship between the BRDF model and intensity data of LiDAR. A series of experiments using typical urban building materials are implemented to validate the proposed BRDF model and integration method. The fitting results show that three parameters extracted from the proposed BRDF model can distinguish the urban building materials from perspectives of roughness, specular reflectance, and diffuse reflectance. A comprehensive analysis of these parameters will help characterize surface features in a physically rigorous manner.

a Study of Dynamic Powder Consolidation Based on a Particle-Level Mathematical Model.

NASA Astrophysics Data System (ADS)

Williamson, Richard L.

A mathematical model is developed to investigate the effects of large amplitude shock waves on powder materials during dynamic consolidation. The model is constructed at the particle level, focusing on a region containing a few powder particles and the surrounding interstices. The general equations of continuum mechanics are solved over this region, using initial and boundary conditions appropriate for the consolidation process. Closure of the equation system is obtained using an analytical equation of state; relations are included to account for solid to liquid phase changes. An elastic, perfectly-plastic constitutive law, specifically modified to describe material behavior at high-strain-rates, is applied to the solid materials. To reduce complexity, the model is restricted to two dimensions, therefore individual particles are approximated as infinitely long cylinders rather than spheres. The equation system is solved using standard finite-difference numerical techniques. It is demonstrated that for typical consolidation conditions, energy diffusion mechanisms are insignificant during the rapid densification phase of consolidation. Using type 304 stainless steel powder material, the particle-level model is used to investigate the mechanisms responsible for particle surface heating and metallurgical bonding during consolidation. It is demonstrated that energy deposition near particle surfaces results both from rapid particle deformation during interstitial filling and large localized impacts occurring at the final instant of interstitial closure; particle interior regions remain at sufficiently low temperatures to avoid microstructural modification. Nonuniform metallurgical bonding is predicted around the particle periphery, ranging from complete fusion to mechanical abutment. Simulation results are used to investigate the detailed wave propagation phenomena at the particle level, providing an improved understanding of this complex behavior. A variety of parametric studies are conducted including investigations of the effects of stress wave amplitude and rise time, the role of interstitial gases during consolidation, and various geometric aspects including the importance of initial void fraction. The model is applied to a metal matrix composite system to investigate the consolidation of mixtures of differing materials; results of a two-dimensional experiment are included. Available experimental data are compared with simulation results. In general, very good agreement between simulation results and data is obtained.

Mathematical modeling of heat treatment processes conserving biological activity of plant bioresources

NASA Astrophysics Data System (ADS)

Rodionova, N. S.; Popov, E. S.; Pozhidaeva, E. A.; Pynzar, S. S.; Ryaskina, L. O.

2018-05-01

The aim of this study is to develop a mathematical model of the heat exchange process of LT-processing to estimate the dynamics of temperature field changes and optimize the regime parameters, due to the non-stationarity process, the physicochemical and thermophysical properties of food systems. The application of LT-processing, based on the use of low-temperature modes in thermal culinary processing of raw materials with preliminary vacuum packaging in a polymer heat- resistant film is a promising trend in the development of technics and technology in the catering field. LT-processing application of food raw materials guarantees the preservation of biologically active substances in food environments, which are characterized by a certain thermolability, as well as extend the shelf life and high consumer characteristics of food systems that are capillary-porous bodies. When performing the mathematical modeling of the LT-processing process, the packet of symbolic mathematics “Maple” was used, as well as the mathematical packet flexPDE that uses the finite element method for modeling objects with distributed parameters. The processing of experimental results was evaluated with the help of the developed software in the programming language Python 3.4. To calculate and optimize the parameters of the LT processing process of polycomponent food systems, the differential equation of non-stationary thermal conductivity was used, the solution of which makes it possible to identify the temperature change at any point of the solid at different moments. The present study specifies data on the thermophysical characteristics of the polycomponent food system based on plant raw materials, with the help of which the physico-mathematical model of the LT- processing process has been developed. The obtained mathematical model allows defining of the dynamics of the temperature field in different sections of the LT-processed polycomponent food systems on the basis of calculating the evolution profiles of temperature fields, which enable one to analyze the efficiency of the regime parameters of heat treatment.

Finite-difference time-domain simulation of electromagnetic bandgap and bi-anisotropic metamaterials

NASA Astrophysics Data System (ADS)

Bray, Matthew G.

The term "Metamaterial" has been introduced into the electromagnetic lexicon in recent years to describe new artificial materials with electromagnetic properties that are not found in naturally occurring materials. Metamaterials exhibit electromagnetic properties that are not observed in its constituent materials, and/or not observed in nature. This thesis will analyze two different classes of metamaterials through the use of the finite-difference time-domain (FDTD) technique. The first class of metamaterials are artificial magnetic conductors (AMC) which approximate the behavior of a perfect magnetic conductor (PMC) over a finite frequency range. The AMC metamaterials are created through the use of an electromagnetic bandgap (EBG) structure. A periodic FDTD code is used to simulate a full-wave model of the metallodielectric EBG structures. The AMCs developed with the aid of the FDTD tool are then used to create low-profile antenna systems consisting of a dipole antenna in close proximity to an AMC surface. Through the use of this FDTD tool, several original contributions were made to the electromagnetic community. These include the first dual-band independently tunable EBG AMC ground plane and the first linearly polarized single-band and dual-band tunable antenna/EBG systems. The second class of materials analyzed are bi-anisotropic metamaterials. Bi-anisotropic media are the largest class of linear media which is able to describe the macroscopic material properties of artificial dielectrics, artificial magnetics, artificial chiral materials, left-handed materials, and other composite materials. The dispersive properties of these materials can be approximated by the oscillator model. This model assumes a Lorentzian frequency profile for the permittivity and permeability and a Condon model for chirality. A new FDTD formulation is introduced which can simulate this type of bi-anisotropic media. This FDTD method incorporates the dispersive material properties through a Z-transform technique derived from the constitutive relations for bi-anisotropic media. This is the first FDTD formulation to be able to simulate dispersive chiral media on a single FDTD grid. This tool was also used to perform the first simulations of dispersive chiral frequency selective surfaces.

Reactive transport simulations of alternative flow pathways in the ambient unsaturated zone at Yucca Mountain, Nevada

NASA Astrophysics Data System (ADS)

Browning, L.; Murphy, W.; Manepally, C.; Fedors, R.

2003-04-01

Uncertainties in simulated ambient system unsaturated zone flow could have a significant impact on performance evaluations of the proposed nuclear waste repository at Yucca Mountain, Nevada. In addition to determining variations in the quantity of water available to corrode engineered materials and transport radionuclides, model assumptions regarding flow pathways may significantly affect estimates of groundwater chemistry. The manner and extent to which groundwater compositions evolve along a flow pathway are determined mainly by thermohydrologic conditions, the types of reactive materials encountered, and the interaction times with those materials. Simulated groundwater compositions can thus vary significantly depending on whether or not the flow model includes lateral diversion of infiltrating waters, or preferential flow pathways in variably-saturated materials. To assist a regulatory review of a potential license application for a geologic repository for high-level waste, we developed a reactive transport model for the ambient hydrogeochemical system at Yucca Mountain. The model simulates two phase, nonisothermal, advective and diffusive flow and transport through a one dimensional, matrix and fracture continua (dual permeability) containing ten kinetically reactive hydrostatigraphic layers in the vicinity of the SD-9 borehole at Yucca Mountain. In this presentation, we describe how the model was used to evaluate alternative ambient unsaturated zone flow pathways proposed by the U.S. Department of Energy. This abstract is an independent product of the CNWRA and does not necessarily reflect the views or regulatory position of the NRC.

Defining the Meaning of a Major Modeling and Simulation Change as Applied to Accreditation

DTIC Science & Technology

2012-12-12

the University of Alabama in Huntsville in 2010. His research interests include model- driven engineering, embedded systems , cloud computing. J...Stevens Institute of Technology, Systems Engineering Research Center This material is based upon work supported, in whole or in part, by the U.S...Department of Defense through the Systems Engineering Research Center (SERC) under Contract H98230-08-D-0171. SERC is a federally funded University

Engineering Biomaterial Properties for Central Nervous System Applications

NASA Astrophysics Data System (ADS)

Rivet, Christopher John

Biomaterials offer unique properties that are intrinsic to the chemistry of the material itself or occur as a result of the fabrication process; iron oxide nanoparticles are superparamagnetic, which enables controlled heating in the presence of an alternating magnetic field, and a hydrogel and electrospun fiber hybrid material provides minimally invasive placement of a fibrous, artificial extracellular matrix for tissue regeneration. Utilization of these unique properties towards central nervous system disease and dysfunction requires a thorough definition of the properties in concert with full biological assessment. This enables development of material-specific features to elicit unique cellular responses. Iron oxide nanoparticles are first investigated for material-dependent, cortical neuron cytotoxicity in vitro and subsequently evaluated for alternating magnetic field stimulation induced hyperthermia, emulating the clinical application for enhanced chemotherapy efficacy in glioblastoma treatment. A hydrogel and electrospun fiber hybrid material is first applied to a rat brain to evaluate biomaterial interface astrocyte accumulation as a function of hybrid material composition. The hybrid material is then utilized towards increasing functional engraftment of dopaminergic progenitor neural stem cells in a mouse model of Parkinson's disease. Taken together, these two scenarios display the role of material property characterization in development of biomaterial strategies for central nervous system repair and regeneration.

Micro-scale investigation on the quasi-static behavior of granular material

NASA Astrophysics Data System (ADS)

Li, Xia

Granular material exhibits complex responses when subjected to various external loading. Fundamental mechanisms have not been well established so far, including that about the critical state, one of the most important concepts in the modern soil mechanics. With the recognition that granular material is discrete in nature, the basic understanding can only be obtained from the particle scale. The complexity in granular material behavior lies in the fact that the macroscopic behavior of granular material is determined by not only the interactions operating at contacts, but also how the particles become arranged in space to form an internal structure. This research is aimed to microscopically investigate the influence of the internal structure and the fundamental mechanism about the critical state. In view of the extensive laboratory test data already available in the literature, a numerical simulation method, DEM, is employed as the tool to conduct particle-scale investigations. The contact model for two in-contact circular disks is derived theoretically from the elasticity theory, and the result is a linear contact model with constant stiffness and lateral sliding. Based on the contact model, a systematic series of numerical tests has been implemented, and the results can successfully reproduce the main characteristics in the behavior of natural granular material, under various loading conditions. The macro-micro relationship is the link between the investigations at the two worlds. The key point is to describe the internal structure with the two dual cell systems, a particle cell system and a void cell system. Based on these two systems, the stress and strain in a uniform field are equivalently expressed in terms of the contact forces/relative displacements, and the micro-geometrical variables. With the microstructural definition of the stress tensor, the stress state of granular material is studied microscopically. The stress-fabric-force relation is derived, based on the variables describing the statistics of the contact forces and the contact vectors. By studying the evolution of the micro-quantities during shearing, how the internal structure affects the macro stress state under different loading condition is revealed. With the assumption that the influence of the local variance in stress is ignorable, the response of granular material can be investigated based on the void cell system. Starting from the behavior of a single void cell, the evolutions of the internal structure and its influence on the response of granular material are explained. The stress ratio and the dilatancy behavior of granular material are investigated. The influences of the void ratio, the mean normal stress and the drainage condition are discussed. The fundamental mechanism of the critical state is studied in the framework of thermodynamics with properly considering the influence of the internal structure. The normalized stress ratio tensor at critical state is associated with the critical void cell anisotropy, corresponding to the maximal energy dissipation. The (e, p) relationship at critical state is associated with the critical combination of the void cell size and the contact interactions, corresponding to the minimal free energy. The investigation on the influence of the internal structure anisotropy on the granular material behavior and the critical state is carried out. The results show that at small strain levels, the behavior of granular material is mainly affected by the initial fabric. As shearing continuous, the internal structure of granular material is gradually changed. The granular material approaches the critical state, which is irrespective with the initial internal structure. The critical state of granular material is not unique. With different loading modes, the critical state of granular material, including both the critical stress ratio and the critical (e, p) relations, are found to be different. A fabric tensor is defined based on the characteristics of the void cells. The laboratory method to quantify the fabric anisotropy is proposed by deviatoric shearing. 3D numerical simulations have been carried out to investigate the influence of the loading mode, which is found to be an important factor in the large strain behavior of granular material. With the obtained microscopic understanding, the influence of contact model on granular material behavior is investigated. A method to quantify the fabric anisotropy is proposed. And a simple discussion on the state variable used in the elasto-plastic constitutive model is given.

Effect of clothing material on thermal responses of the human body

NASA Astrophysics Data System (ADS)

Fengzhi, Li; Yi, Li

2005-09-01

The influence of clothing material on thermal responses of the human body are investigated by using an integrated model of a clothed thermoregulatory human body. A modified 25-nodes model considering the sweat accumulation on the skin surface is applied to simulate the human physiological regulatory responses. The heat and moisture coupled transfer mechanisms, including water vapour diffusion, the moisture evaporation/condensation, the moisture sorbtion/desorption by fibres, liquid sweat transfer under capillary pressure, and latent heat absorption/release due to phase change, are considered in the clothing model. On comparing prediction results with the experimental data in the literature, the proposed model seems able to predict dynamic heat and moisture transfer between the human body and the clothing system. The human body's thermal responses and clothing temperature and moisture variations are compared for different clothing materials during transient periods. We concluded that the hygroscopicity of clothing materials influences the human thermoregulation process significantly during environmental transients.

Spectrophotometry and organic matter on Iapetus. 1: Composition models

NASA Technical Reports Server (NTRS)

Wilson, Peter D.; Sagan, Carl

1995-01-01

Iapetus shows a greater hemispheric albedo asymmetry than any other body in the solar system. Hapke scattering theory and optical constants measured in the laboratory are used to identify possible compositions for the dark material on the leading hemisphere of Iapetus. The materials considered are poly-HCN, kerogen, Murchison organic residue, Titan tholin, ice tholin, and water ice. Three-component mixtures of these materials are modeled in intraparticle mixture of 25% poly-HCN, 10% Murchison residue, and 65% water ice is found to best fit the spectrum, albedo, and phase behavior of the dark material. The Murchison residue and/or water ice can be replaced by kerogen and ice tholin, respectively, and still produce very good fits. Areal and particle mixtures of poly-HCN, Titan tholin, and either ice tholin or Murchison residue are also possible models. Poly-HCN is a necessary component in almost all good models. The presence of poly-HCN can be further tested by high-resolution observations near 4.5 micrometers.

Multi-Scale Modeling of Microstructural Evolution in Structural Metallic Systems

NASA Astrophysics Data System (ADS)

Zhao, Lei

Metallic alloys are a widely used class of structural materials, and the mechanical properties of these alloys are strongly dependent on the microstructure. Therefore, the scientific design of metallic materials with superior mechanical properties requires the understanding of the microstructural evolution. Computational models and simulations offer a number of advantages over experimental techniques in the prediction of microstructural evolution, because they can allow studies of microstructural evolution in situ, i.e., while the material is mechanically loaded (meso-scale simulations), and bring atomic-level insights into the microstructure (atomistic simulations). In this thesis, we applied a multi-scale modeling approach to study the microstructural evolution in several metallic systems, including polycrystalline materials and metallic glasses (MGs). Specifically, for polycrystalline materials, we developed a coupled finite element model that combines phase field method and crystal plasticity theory to study the plasticity effect on grain boundary (GB) migration. Our model is not only coupled strongly (i.e., we include plastic driving force on GB migration directly) and concurrently (i.e., coupled equations are solved simultaneously), but also it qualitatively captures such phenomena as the dislocation absorption by mobile GBs. The developed model provides a tool to study the microstructural evolution in plastically deformed metals and alloys. For MGs, we used molecular dynamics (MD) simulations to investigate the nucleation kinetics in the primary crystallization in Al-Sm system. We calculated the time-temperature-transformation curves for low Sm concentrations, from which the strong suppressing effect of Sm solute on Al nucleation and its influencing mechanism are revealed. Also, through the comparative analysis of both Al attachment and Al diffusion in MGs, it has been found that the nucleation kinetics is controlled by interfacial attachment of Al, and that the attachment behavior takes place collectively and heterogeneously, similarly to Al diffusion in MGs. Finally, we applied the MD technique to study the origin of five-fold twinning nucleation during the solidification of Al base alloys. We studied several model alloys and reported the observed nucleation pathway. We found that the key factors controlling the five-fold twinning are the twin boundary energy and the formation of pentagon structures, and the twin boundary energy plays the dominant role in the five-fold twinning in the model alloys studied.

Lithium potential variations for metastable materials: case study of nanocrystalline and amorphous LiFePO4.

PubMed

Zhu, Changbao; Mu, Xiaoke; Popovic, Jelena; Weichert, Katja; van Aken, Peter A; Yu, Yan; Maier, Joachim

2014-09-10

Much attention has been paid to metastable materials in the lithium battery field, especially to nanocrystalline and amorphous materials. Nonetheless, fundamental issues such as lithium potential variations have not been pertinently addressed. Using LiFePO4 as a model system, we inspect such lithium potential variations for various lithium storage modes and evaluate them thermodynamically. The conclusions of this work are essential for an adequate understanding of the behavior of electrode materials and even helpful in the search for new energy materials.

Methods for multi-material stereolithography

DOEpatents

Wicker, Ryan [El Paso, TX; Medina, Francisco [El Paso, TX; Elkins, Christopher [Redwood City, CA

2011-06-14

Methods and systems of stereolithography for building cost-efficient and time-saving multi-material, multi-functional and multi-colored prototypes, models and devices configured for intermediate washing and curing/drying is disclosed including: laser(s), liquid and/or platform level sensing system(s), controllable optical system(s), moveable platform(s), elevator platform(s), recoating system(s) and at least one polymer retaining receptacle. Multiple polymer retaining receptacles may be arranged in a moveable apparatus, wherein each receptacle is adapted to actively/passively maintain a uniform, desired level of polymer by including a recoating device and a material fill/remove system. The platform is movably accessible to the polymer retaining receptacle(s), elevator mechanism(s) and washing and curing/drying area(s) which may be housed in a shielded enclosure(s). The elevator mechanism is configured to vertically traverse and rotate the platform, thus providing angled building, washing and curing/drying capabilities. A horizontal traversing mechanism may be included to facilitate manufacturing between components of SL cabinet(s) and/or alternative manufacturing technologies.

Simulations of inorganic-bioorganic interfaces to discover new materials: insights, comparisons to experiment, challenges, and opportunities.

PubMed

Heinz, Hendrik; Ramezani-Dakhel, Hadi

2016-01-21

Natural and man-made materials often rely on functional interfaces between inorganic and organic compounds. Examples include skeletal tissues and biominerals, drug delivery systems, catalysts, sensors, separation media, energy conversion devices, and polymer nanocomposites. Current laboratory techniques are limited to monitor and manipulate assembly on the 1 to 100 nm scale, time-consuming, and costly. Computational methods have become increasingly reliable to understand materials assembly and performance. This review explores the merit of simulations in comparison to experiment at the 1 to 100 nm scale, including connections to smaller length scales of quantum mechanics and larger length scales of coarse-grain models. First, current simulation methods, advances in the understanding of chemical bonding, in the development of force fields, and in the development of chemically realistic models are described. Then, the recognition mechanisms of biomolecules on nanostructured metals, semimetals, oxides, phosphates, carbonates, sulfides, and other inorganic materials are explained, including extensive comparisons between modeling and laboratory measurements. Depending on the substrate, the role of soft epitaxial binding mechanisms, ion pairing, hydrogen bonds, hydrophobic interactions, and conformation effects is described. Applications of the knowledge from simulation to predict binding of ligands and drug molecules to the inorganic surfaces, crystal growth and shape development, catalyst performance, as well as electrical properties at interfaces are examined. The quality of estimates from molecular dynamics and Monte Carlo simulations is validated in comparison to measurements and design rules described where available. The review further describes applications of simulation methods to polymer composite materials, surface modification of nanofillers, and interfacial interactions in building materials. The complexity of functional multiphase materials creates opportunities to further develop accurate force fields, including reactive force fields, and chemically realistic surface models, to enable materials discovery at a million times lower computational cost compared to quantum mechanical methods. The impact of modeling and simulation could further be increased by the advancement of a uniform simulation platform for organic and inorganic compounds across the periodic table and new simulation methods to evaluate system performance in silico.

Unsaturated hydraulic behaviour of a permeable pavement: Laboratory investigation and numerical analysis by using the HYDRUS-2D model

NASA Astrophysics Data System (ADS)

Turco, Michele; Kodešová, Radka; Brunetti, Giuseppe; Nikodem, Antonín; Fér, Miroslav; Piro, Patrizia

2017-11-01

An adequate hydrological description of water flow in permeable pavement systems relies heavily on the knowledge of the unsaturated hydraulic properties of the construction materials. Although several modeling tools and many laboratory methods already exist in the literature to determine the hydraulic properties of soils, the importance of an accurate materials hydraulic description of the permeable pavement system, is increasingly recognized in the fields of urban hydrology. Thus, the aim of this study is to propose techniques/procedures on how to interpret water flow through the construction system using the HYDRUS model. The overall analysis includes experimental and mathematical procedures for model calibration and validation to assess the suitability of the HYDRUS-2D model to interpret the hydraulic behaviour of a lab-scale permeable pavement system. The system consists of three porous materials: a wear layer of porous concrete blocks, a bedding layers of fine gravel, and a sub-base layer of coarse gravel. The water regime in this system, i.e. outflow at the bottom and water contents in the middle of the bedding layer, was monitored during ten irrigation events of various durations and intensities. The hydraulic properties of porous concrete blocks and fine gravel described by the van Genuchten functions were measured using the clay tank and the multistep outflow experiments, respectively. Coarse gravel properties were set at literature values. In addition, some of the parameters (Ks of the concrete blocks layer, and α, n and Ks of the bedding layer) were optimized with the HYDRUS-2D model from water fluxes and soil water contents measured during irrigation events. The measured and modeled hydrographs were compared using the Nash-Sutcliffe efficiency (NSE) index (varied between 0.95 and 0.99) while the coefficient of determination R2 was used to assess the measured water content versus the modelled water content in the bedding layer (R2 = 0.81 ÷ 0.87) . The parameters were validated using the remaining sets of measurements resulting in NSE values greater than 0.90 (0.91 ÷ 0.99) and R2 between 0.63 and 0.91. Results have confirmed the applicability of HYDRUS-2D to describe correctly the hydraulic behaviour of the lab-scale system.

A differential CDM model for fatigue of unidirectional metal matrix composites

NASA Technical Reports Server (NTRS)

Arnold, S. M.; Kruch, S.

1992-01-01

A multiaxial, isothermal, continuum damage mechanics (CDM) model for fatigue of a unidirectional metal matrix composite volume element is presented. The model is phenomenological, stress based, and assumes a single scalar internal damage variable, the evolution of which is anisotropic. The development of the fatigue damage model, (i.e., evolutionary law) is based on the definition of an initially transversely isotropic fatigue limit surface, a static fracture surface, and a normalized stress amplitude function. The anisotropy of these surfaces and function, and therefore the model, is defined through physically meaningful invariants reflecting the local stress and material orientation. This transversely isotropic model is shown, when taken to it's isotropic limit, to directly simplify to a previously developed and validated isotropic fatigue continuum damage model. Results of a nondimensional parametric study illustrate (1) the flexibility of the present formulation in attempting to characterize a class of composite materials, and (2) the capability of the formulation in predicting anticipated qualitative trends in the fatigue behavior of unidirectional metal matrix composites. Also, specific material parameters representing an initial characterization of the composite system SiC/Ti 15-3 and the matrix material (Ti 15-3) are reported.

Empirical testing of an analytical model predicting electrical isolation of photovoltaic models

NASA Astrophysics Data System (ADS)

Garcia, A., III; Minning, C. P.; Cuddihy, E. F.

A major design requirement for photovoltaic modules is that the encapsulation system be capable of withstanding large DC potentials without electrical breakdown. Presented is a simple analytical model which can be used to estimate material thickness to meet this requirement for a candidate encapsulation system or to predict the breakdown voltage of an existing module design. A series of electrical tests to verify the model are described in detail. The results of these verification tests confirmed the utility of the analytical model for preliminary design of photovoltaic modules.

Kinetics of process of product separation in closed system with recirculation

NASA Astrophysics Data System (ADS)

Prokopenko, V. S.; Orekhova, T. N.; Goncharov, E. I.; Odobesko, I. A.

2018-03-01

The object of an article is the extrapolation of the process of classifying material while passing in a model with the separation of the products of milling in the cleaning system includes a separator, concentrator, cyclone and a recycle loop. The model allows for the given parameters to predict the coarseness of grading of the finished product.

Molecular dynamics modelling of mechanical properties of polymers for adaptive aerospace structures

NASA Astrophysics Data System (ADS)

Papanikolaou, Michail; Drikakis, Dimitris; Asproulis, Nikolaos

2015-02-01

The features of adaptive structures depend on the properties of the supporting materials. For example, morphing wing structures require wing skin materials, such as rubbers that can withstand the forces imposed by the internal mechanism while maintaining the required aerodynamic properties of the aircraft. In this study, Molecular Dynamics and Minimization simulations are being used to establish well-equilibrated models of Ethylene-Propylene-Diene Monomer (EPDM) elastomer systems and investigate their mechanical properties.

The theory of cyclic voltammetry of electrochemically heterogeneous surfaces: comparison of different models for surface geometry and applications to highly ordered pyrolytic graphite.

PubMed

Ward, Kristopher R; Lawrence, Nathan S; Hartshorne, R Seth; Compton, Richard G

2012-05-28

The cyclic voltammetry at electrodes composed of multiple electroactive materials, where zones of one highly active material are distributed over a substrate of a second, less active material, is investigated by simulation. The two materials are assumed to differ in terms of their electrochemical rate constants towards any given redox couple. For a one-electron oxidation or reduction, the effect on voltammetry of the size and relative surface coverages of the zones as well as the rate constant of the slower zone are considered for systems where it is much slower than the rate constant of the faster zones. The occurrence of split peak cyclic voltammetry where two peaks are observed in the forward sweep, is studied in terms of the diffusional effects present in the system. A number of surface geometries are compared: specifically the more active zones are modelled as long, thin bands, as steps in the surface, as discs, and as rings (similar to a partially blocked electrode). Similar voltammetry for the band, step and ring models is seen but the disc geometry shows significant differences. Finally, the simulation technique is applied to the modelling of highly-ordered pyrolytic graphite (HOPG) surface and experimental conditions under which it may be possible to observe split peak voltammetry are predicted.

Multiscale Modeling of Carbon/Phenolic Composite Thermal Protection Materials: Atomistic to Effective Properties

NASA Technical Reports Server (NTRS)

Arnold, Steven M.; Murthy, Pappu L.; Bednarcyk, Brett A.; Lawson, John W.; Monk, Joshua D.; Bauschlicher, Charles W., Jr.

2016-01-01

Next generation ablative thermal protection systems are expected to consist of 3D woven composite architectures. It is well known that composites can be tailored to achieve desired mechanical and thermal properties in various directions and thus can be made fit-for-purpose if the proper combination of constituent materials and microstructures can be realized. In the present work, the first, multiscale, atomistically-informed, computational analysis of mechanical and thermal properties of a present day - Carbon/Phenolic composite Thermal Protection System (TPS) material is conducted. Model results are compared to measured in-plane and out-of-plane mechanical and thermal properties to validate the computational approach. Results indicate that given sufficient microstructural fidelity, along with lowerscale, constituent properties derived from molecular dynamics simulations, accurate composite level (effective) thermo-elastic properties can be obtained. This suggests that next generation TPS properties can be accurately estimated via atomistically informed multiscale analysis.

Algorithm applying a modified BRDF function in Λ-ridge concentrator of solar radiation

NASA Astrophysics Data System (ADS)

Plachta, Kamil

2015-05-01

This paper presents an algorithm that uses the modified BRDF function. It allows the calculation of the parameters of Λ-ridge concentrator system. The concentrator directs reflected solar radiation on photovoltaic surface, increasing its efficiency. The efficiency of the concentrator depends on the surface characteristics of the material which it is made of, the angle of the photovoltaic panel and the resolution of the tracking system. It shows a method of modeling the surface by using the BRDF function and describes its basic parameters, e.g. roughness and the components of the reflected stream. A cost calculation of chosen models with presented in this article BRDF function modification has been made. The author's own simulation program allows to choose the appropriate material for construction of a Λ-ridge concentrator, generate micro surface of the material, and simulate the shape and components of the reflected stream.

Observation of three-dimensional internal structure of steel materials by means of serial sectioning with ultrasonic elliptical vibration cutting.

PubMed

Fujisaki, K; Yokota, H; Nakatsuchi, H; Yamagata, Y; Nishikawa, T; Udagawa, T; Makinouchi, A

2010-01-01

A three-dimensional (3D) internal structure observation system based on serial sectioning was developed from an ultrasonic elliptical vibration cutting device and an optical microscope combined with a high-precision positioning device. For bearing steel samples, the cutting device created mirrored surfaces suitable for optical metallography, even for long-cutting distances during serial sectioning of these ferrous materials. Serial sectioning progressed automatically by means of numerical control. The system was used to observe inclusions in steel materials on a scale of several tens of micrometers. Three specimens containing inclusions were prepared from bearing steels. These inclusions could be detected as two-dimensional (2D) sectional images with resolution better than 1 mum. A three-dimensional (3D) model of each inclusion was reconstructed from the 2D serial images. The microscopic 3D models had sharp edges and complicated surfaces.

Computational materials design of crystalline solids.

PubMed

Butler, Keith T; Frost, Jarvist M; Skelton, Jonathan M; Svane, Katrine L; Walsh, Aron

2016-11-07

The modelling of materials properties and processes from first principles is becoming sufficiently accurate as to facilitate the design and testing of new systems in silico. Computational materials science is both valuable and increasingly necessary for developing novel functional materials and composites that meet the requirements of next-generation technology. A range of simulation techniques are being developed and applied to problems related to materials for energy generation, storage and conversion including solar cells, nuclear reactors, batteries, fuel cells, and catalytic systems. Such techniques may combine crystal-structure prediction (global optimisation), data mining (materials informatics) and high-throughput screening with elements of machine learning. We explore the development process associated with computational materials design, from setting the requirements and descriptors to the development and testing of new materials. As a case study, we critically review progress in the fields of thermoelectrics and photovoltaics, including the simulation of lattice thermal conductivity and the search for Pb-free hybrid halide perovskites. Finally, a number of universal chemical-design principles are advanced.

Modeling Earth's Climate

ERIC Educational Resources Information Center

Pallant, Amy; Lee, Hee-Sun; Pryputniewicz, Sara

2012-01-01

Systems thinking suggests that one can best understand a complex system by studying the interrelationships of its component parts rather than looking at the individual parts in isolation. With ongoing concern about the effects of climate change, using innovative materials to help students understand how Earth's systems connect with each other is…

INTEGRATED AIR POLLUTION CONTROL SYSTEM, VERSION 4.0 - VOLUME 1: USER'S GUIDE

EPA Science Inventory

The Integrated Air Pollution Control System (IAPCS) was developed for the U.S. EPA's Air and Energy Engineering Research Laboratory to estimate costs and performance for emission control systems applied to coal-fired utility boilers. The model can project a material balance, and ...

Models and materials for generalized Kitaev magnetism

NASA Astrophysics Data System (ADS)

Winter, Stephen M.; Tsirlin, Alexander A.; Daghofer, Maria; van den Brink, Jeroen; Singh, Yogesh; Gegenwart, Philipp; Valentí, Roser

2017-12-01

The exactly solvable Kitaev model on the honeycomb lattice has recently received enormous attention linked to the hope of achieving novel spin-liquid states with fractionalized Majorana-like excitations. In this review, we analyze the mechanism proposed by Jackeli and Khaliullin to identify Kitaev materials based on spin-orbital dependent bond interactions and provide a comprehensive overview of its implications in real materials. We set the focus on experimental results and current theoretical understanding of planar honeycomb systems (Na2IrO3, α-Li2IrO3, and α-RuCl3), three-dimensional Kitaev materials (β- and γ-Li2IrO3), and other potential candidates, completing the review with the list of open questions awaiting new insights.

Patient-specific system for prognosis of surgical treatment outcomes of human cardiovascular system

NASA Astrophysics Data System (ADS)

Golyadkina, Anastasiya A.; Kalinin, Aleksey A.; Kirillova, Irina V.; Kossovich, Elena L.; Kossovich, Leonid Y.; Menishova, Liyana R.; Polienko, Asel V.

2015-03-01

Object of study: Improvement of life quality of patients with high stroke risk ia the main goal for development of system for patient-specific modeling of cardiovascular system. This work is dedicated at increase of safety outcomes for surgical treatment of brain blood supply alterations. The objects of study are common carotid artery, internal and external carotid arteries and bulb. Methods: We estimated mechanical properties of carotid arteries tissues and patching materials utilized at angioplasty. We studied angioarchitecture features of arteries. We developed and clinically adapted computer biomechanical models, which are characterized by geometrical, physical and mechanical similarity with carotid artery in norm and with pathology (atherosclerosis, pathological tortuosity, and their combination). Results: Collaboration of practicing cardiovascular surgeons and specialists in the area of Mathematics and Mechanics allowed to successfully conduct finite-element modeling of surgical treatment taking into account various features of operation techniques and patching materials for a specific patient. Numerical experiment allowed to reveal factors leading to brain blood supply decrease and atherosclerosis development. Modeling of carotid artery reconstruction surgery for a specific patient on the basis of the constructed biomechanical model demonstrated the possibility of its application in clinical practice at approximation of numerical experiment to the real conditions.

Properties predictive modeling through the concept of a hybrid interphase existing between phases in contact

NASA Astrophysics Data System (ADS)

Portan, D. V.; Papanicolaou, G. C.

2018-02-01

From practical point of view, predictive modeling based on the physics of composite material behavior is wealth generating; by guiding material system selection and process choices, by cutting down on experimentation and associated costs; and by speeding up the time frame from the research stage to the market place. The presence of areas with different properties and the existence of an interphase between them have a pronounced influence on the behavior of a composite system. The Viscoelastic Hybrid Interphase Model (VHIM), considers the existence of a non-homogeneous viscoelastic and anisotropic interphase having properties depended on the degree of adhesion between the two phases in contact. The model applies for any physical/mechanical property (e.g. mechanical, thermal, electrical and/or biomechanical). Knowing the interphasial variation of a specific property one can predict the corresponding macroscopic behavior of the composite. Moreover, the model acts as an algorithm and a two-way approach can be used: (i) phases in contact may be chosen to get the desired properties of the final composite system or (ii) the initial phases in contact determine the final behavior of the composite system, that can be approximately predicted. The VHIM has been proven, amongst others, to be extremely useful in biomaterial designing for improved contact with human tissues.

Biologically inspired information theory: Adaptation through construction of external reality models by living systems.

PubMed

Nakajima, Toshiyuki

2015-12-01

Higher animals act in the world using their external reality models to cope with the uncertain environment. Organisms that have not developed such information-processing organs may also have external reality models built in the form of their biochemical, physiological, and behavioral structures, acquired by natural selection through successful models constructed internally. Organisms subject to illusions would fail to survive in the material universe. How can organisms, or living systems in general, determine the external reality from within? This paper starts with a phenomenological model, in which the self constitutes a reality model developed through the mental processing of phenomena. Then, the it-from-bit concept is formalized using a simple mathematical model. For this formalization, my previous work on an algorithmic process is employed to constitute symbols referring to the external reality, called the inverse causality, with additional improvements to the previous work. Finally, as an extension of this model, the cognizers system model is employed to describe the self as one of many material entities in a world, each of which acts as a subject by responding to the surrounding entities. This model is used to propose a conceptual framework of information theory that can deal with both the qualitative (semantic) and quantitative aspects of the information involved in biological processes. Copyright © 2015 Elsevier Ltd. All rights reserved.

Development of Rapid, Continuous Calibration Techniques and Implementation as a Prototype System for Civil Engineering Materials Evaluation

NASA Astrophysics Data System (ADS)

Scott, M. L.; Gagarin, N.; Mekemson, J. R.; Chintakunta, S. R.

2011-06-01

Until recently, civil engineering material calibration data could only be obtained from material sample cores or via time consuming, stationary calibration measurements in a limited number of locations. Calibration data are used to determine material propagation velocities of electromagnetic waves in test materials for use in layer thickness measurements and subsurface imaging. Limitations these calibration methods impose have been a significant impediment to broader use of nondestructive evaluation methods such as ground-penetrating radar (GPR). In 2006, a new rapid, continuous calibration approach was designed using simulation software to address these measurement limitations during a Federal Highway Administration (FHWA) research and development effort. This continuous calibration method combines a digitally-synthesized step-frequency (SF)-GPR array and a data collection protocol sequence for the common midpoint (CMP) method. Modeling and laboratory test results for various data collection protocols and materials are presented in this paper. The continuous-CMP concept was finally implemented for FHWA in a prototype demonstration system called the Advanced Pavement Evaluation (APE) system in 2009. Data from the continuous-CMP protocol is processed using a semblance/coherency analysis to determine material propagation velocities. Continuously calibrated pavement thicknesses measured with the APE system in 2009 are presented. This method is efficient, accurate, and cost-effective.

Development of rapid, continuous calibration techniques and implementation as a prototype system for civil engineering materials evaluation

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

Scott, M. L.; Gagarin, N.; Mekemson, J. R.

Until recently, civil engineering material calibration data could only be obtained from material sample cores or via time consuming, stationary calibration measurements in a limited number of locations. Calibration data are used to determine material propagation velocities of electromagnetic waves in test materials for use in layer thickness measurements and subsurface imaging. Limitations these calibration methods impose have been a significant impediment to broader use of nondestructive evaluation methods such as ground-penetrating radar (GPR). In 2006, a new rapid, continuous calibration approach was designed using simulation software to address these measurement limitations during a Federal Highway Administration (FHWA) research andmore » development effort. This continuous calibration method combines a digitally-synthesized step-frequency (SF)-GPR array and a data collection protocol sequence for the common midpoint (CMP) method. Modeling and laboratory test results for various data collection protocols and materials are presented in this paper. The continuous-CMP concept was finally implemented for FHWA in a prototype demonstration system called the Advanced Pavement Evaluation (APE) system in 2009. Data from the continuous-CMP protocol is processed using a semblance/coherency analysis to determine material propagation velocities. Continuously calibrated pavement thicknesses measured with the APE system in 2009 are presented. This method is efficient, accurate, and cost-effective.« less

Recondensation of chondritic material in the early solar system: Results of thermodynamic simulation

NASA Technical Reports Server (NTRS)

Dorofeyeva, V. A.; Makalkin, A. B.; Mironenko, M. V.; Vityazev, A. V.

1993-01-01

We have performed a thermodynamic simulation of the recondensation of evaporated meteoritic material. We suggest that evaporation and recondensation occurred in impact events during the intercollision of planetesimals during the early evolution of the solar system. The source materials adopted for our model are the chondrites CI Orgueil and H5 Richardton. These chondrites are representative examples of the two extremes regarding volatile content and oxidation state. We calculated equilibrium mineral compositions of the closed systems of the Orgueil's and Richardton's elemental composition at the P-T conditions characteristic of the explosion cloud formed at a planetesimal collision. The P-T conditions are as follows: 10(exp -4) bar, and 1500 and 2000 K. The results are presented.

Thermal conductivity of aerogel blanket insulation under cryogenic-vacuum conditions in different gas environments

NASA Astrophysics Data System (ADS)

E Fesmire, J.; Ancipink, J. B.; Swanger, A. M.; White, S.; Yarbrough, D.

2017-12-01

Thermal conductivity of low-density materials in thermal insulation systems varies dramatically with the environment: cold vacuum pressure, residual gas composition, and boundary temperatures. Using a reference material of aerogel composite blanket (reinforcement fibers surrounded by silica aerogel), an experimental basis for the physical heat transmission model of aerogel composites and other low-density, porous materials is suggested. Cryogenic-vacuum testing between the boundary temperatures of 78 K and 293 K is performed using a one meter cylindrical, absolute heat flow calorimeter with an aerogel blanket specimen exposed to different gas environments of nitrogen, helium, argon, or CO2. Cold vacuum pressures include the full range from 1×10-5 torr to 760 torr. The soft vacuum region, from about 0.1 torr to 10 torr, is complex and difficult to model because all modes of heat transfer - solid conduction, radiation, gas conduction, and convection - are significant contributors to the total heat flow. Therefore, the soft vacuum tests are emphasized for both heat transfer analysis and practical thermal data. Results for the aerogel composite blanket are analyzed and compared to data for its component materials. With the new thermal conductivity data, future applications of aerogel-based insulation systems are also surveyed. These include Mars exploration and surface systems in the 5 torr CO2 environment, field joints for vacuum-jacketed cryogenic piping systems, common bulkhead panels for cryogenic tanks on space launch vehicles, and liquid hydrogen cryofuel systems with helium purged conduits or enclosures.

Performance investigation on DCSFCL considering different magnetic materials

NASA Astrophysics Data System (ADS)

Yuan, Jiaxin; Zhou, Hang; Zhong, Yongheng; Gan, Pengcheng; Gao, Yanhui; Muramatsu, Kazuhiro; Du, Zhiye; Chen, Baichao

2018-05-01

In order to protect high voltage direct current (HVDC) system from destructive consequences caused by fault current, a novel concept of HVDC system fault current limiter (DCSFCL) was proposed previously. Since DCSFCL is based on saturable core reactor theory, iron core becomes the key to the final performance of it. Therefore, three typical kinds of soft magnetic materials were chosen to find out their impact on performances of DCSFCL. Different characteristics of materials were compared and their theoretical deductions were carried out, too. In the meanwhile, 3D models applying those three materials were built separately and finite element analysis simulations were performed to compare these results and further verify the assumptions. It turns out that materials with large saturation flux density value Bs like silicon steel and short demagnetization time like ferrite might be the best choice for DCSFCL, which can be a future research direction of magnetic materials.

Tuning critical failure with viscoelasticity: How aftershocks inhibit criticality in an analytical mean field model of fracture.

NASA Astrophysics Data System (ADS)

Baro Urbea, J.; Davidsen, J.

2017-12-01

The hypothesis of critical failure relates the presence of an ultimate stability point in the structural constitutive equation of materials to a divergence of characteristic scales in the microscopic dynamics responsible of deformation. Avalanche models involving critical failure have determined universality classes in different systems: from slip events in crystalline and amorphous materials to the jamming of granular media or the fracture of brittle materials. However, not all empirical failure processes exhibit the trademarks of critical failure. As an example, the statistical properties of ultrasonic acoustic events recorded during the failure of porous brittle materials are stationary, except for variations in the activity rate that can be interpreted in terms of aftershock and foreshock activity (J. Baró et al., PRL 2013).The rheological properties of materials introduce dissipation, usually reproduced in atomistic models as a hardening of the coarse-grained elements of the system. If the hardening is associated to a relaxation process the same mechanism is able to generate temporal correlations. We report the analytic solution of a mean field fracture model exemplifying how criticality and temporal correlations are tuned by transient hardening. We provide a physical meaning to the conceptual model by deriving the constitutive equation from the explicit representation of the transient hardening in terms of a generalized viscoelasticity model. The rate of 'aftershocks' is controlled by the temporal evolution of the viscoelastic creep. At the quasistatic limit, the moment release is invariant to rheology. Therefore, the lack of criticality is explained by the increase of the activity rate close to failure, i.e. 'foreshocks'. Finally, the avalanche propagation can be reinterpreted as a pure mathematical problem in terms of a stochastic counting process. The statistical properties depend only on the distance to a critical point, which is universal for any parametrization of the transient hardening and a whole category of fracture models.

Modeling the fate and end-of-life phase of engineered nanomaterials in the Japanese construction sector.

PubMed

Suzuki, Shinya; Part, Florian; Matsufuji, Yasushi; Huber-Humer, Marion

2018-02-01

To date construction materials that contain engineered nanomaterials (ENMs) are available at the markets, but at the same time very little is known about their environmental fate. Therefore, this study aimed at modeling the potential fate of ENMs by using the example of the Japanese construction sector and by conducting a dynamic material flow analysis. Expert interviews and national reports revealed that about 3920-4660 tons of ENMs are annually used for construction materials in Japan. Nanoscale TiO 2 , SiO 2 , Al 2 O 3 and carbon black have already been applied for decades to wall paints, road markings or concrete. The dynamic material flow model indicates that in 2016 about 95% of ENMs, which have been used since their year of market penetration, remained in buildings, whereas only 5% ended up in the Japanese waste management system or were diffusely released into the environment. Considering the current Japanese waste management system, ENMs were predicted to end up in recycled materials (40-47%) or in landfills (36-41%). It was estimated that only a small proportion was used in agriculture (5-7%, as ENM-containing sewage sludges) or was diffusely released into soils, surface waters or the atmosphere (5-19%). The results indicate that ENM release predominantly depend on their specific applications and characteristics. The model also highlights the importance of adequate collection and treatment of ENM-containing wastes. In future, similar dynamic flow models for other countries should consider, inasmuch as available, historical data on ENM production (e.g. like declaration reports that are annually published by relevant public authorities or associations), as such input data is very important regarding data reliability in order to decrease uncertainties and to continuously improve model accuracy. In addition, more environmental monitoring studies that aim at the quantification of ENM release and inadvertent transfer, particularly triggered by waste treatment processes, would be needed in order to validate such models. Copyright © 2017 Elsevier Ltd. All rights reserved.

Adaptive and active materials: selected papers from the ASME 2013 Conference on Smart Materials, Adaptive Structures and Intelligent Systems (SMASIS 13) (Snowbird, UT, USA, 16-18 September 2013)

NASA Astrophysics Data System (ADS)

Johnson, Nancy; Naguib, Hani; Turner, Travis; Anderson, Iain; Bassiri-Gharb, Nazanin; Daqaq, Mohammed; Baba Sundaresan, Vishnu; Sarles, Andy

2014-10-01

The sixth annual meeting of the ASME Smart Materials, Adaptive Structures and Intelligent Systems Conference (SMASIS) was held in the beautiful mountain encircled Snowbird Resort and Conference Center in Little Cottonwood Canyon near Salt Lake City, Utah. It is the conference's objective to provide an up-to-date overview of research trends in the entire field of smart materials systems in a friendly casual forum conducive to the exchange of ideas and latest results. As each year we strive to grow and offer new experiences, this year we included special focused topic tracks on nanoscale multiferroic materials and origami engineering. The cross-disciplinary emphasis was reflected in keynote speeches by Professor Kaushik Bhattacharya (California Institute of Technology) on 'Cyclic Deformation and the Interplay between Phase Transformation and Plasticity in Shape Memory Alloys', by Professor Alison Flatau (University of Maryland at College Park) on 'Structural Magnetostrictive Alloys: The Other Smart Material', and by Dr Leslie Momoda (Director of the Sensors and Materials Laboratories, HRL Laboratories, LLC, Malibu, CA) on 'Architecturing New Functional Materials: An Industrial Perspective'. SMASIS 2013 was divided into seven symposia which span basic research, applied technological design and development, and industrial and governmental integrated system and application demonstrations. SYMP 1. Development and Characterization of Multifunctional Materials. SYMP 2. Mechanics and Behavior of Active Materials. SYMP 3. Modeling, Simulation and Control of Adaptive Systems. SYMP 4. Integrated System Design and Implementation. SYMP 5. Structural Health Monitoring. SYMP 6. Bioinspired Smart Materials and Systems. SYMP 7. Energy Harvesting. Authors of selected papers in the materials areas (symposia 1, 2, and 6) as well as energy harvesting (symposium 7) were invited to write a full journal article on their presentation topic for publication in this special issue of Smart Materials and Structures. This collection of papers demonstrates the exceptional quality and originality of the conference presentations. We are very appreciative of their efforts to produce this collection of highly relevant articles on smart materials.

Life prediction and constitutive models for engine hot section anisotropic materials

NASA Technical Reports Server (NTRS)

Swanson, G. A.; Linask, I.; Nissley, D. M.; Norris, P. P.; Meyer, T. G.; Walker, K. P.

1987-01-01

The results are presented of a program designed to develop life prediction and constitutive models for two coated single crystal alloys used in gas turbine airfoils. The two alloys are PWA 1480 and Alloy 185. The two oxidation resistant coatings are PWA 273, an aluminide coating, and PWA 286, an overlay NiCoCrAlY coating. To obtain constitutive and fatigue data, tests were conducted on uncoated and coated specimens loaded in the CH76 100 CH110 , CH76 110 CH110 , CH76 111 CH110 and CH76 123 CH110 crystallographic directions. Two constitutive models are being developed and evaluated for the single crystal materials: a micromechanic model based on crystallographic slip systems, and a macroscopic model which employs anisotropic tensors to model inelastic deformation anisotropy. Based on tests conducted on the overlay coating material, constitutive models for coatings also appear feasible and two initial models were selected. A life prediction approach was proposed for coated single crystal materials, including crack initiation either in the coating or in the substrate. The coating initiated failures dominated in the tests at load levels typical of gas turbine operation. Coating life was related to coating stress/strain history which was determined from specimen data using the constitutive models.

Determination of effective mechanical properties of a double-layer beam by means of a nano-electromechanical transducer

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

Hocke, Fredrik; Pernpeintner, Matthias; Gross, Rudolf, E-mail: rudolf.gross@wmi.badw.de

We investigate the mechanical properties of a doubly clamped, double-layer nanobeam embedded into an electromechanical system. The nanobeam consists of a highly pre-stressed silicon nitride and a superconducting niobium layer. By measuring the mechanical displacement spectral density both in the linear and the nonlinear Duffing regime, we determine the pre-stress and the effective Young's modulus of the nanobeam. An analytical double-layer model quantitatively corroborates the measured values. This suggests that this model can be used to design mechanical multilayer systems for electro- and optomechanical devices, including materials controllable by external parameters such as piezoelectric, magnetostrictive, or in more general multiferroicmore » materials.« less

A visco-poroelastic model of functional adaptation in bones reconstructed with bio-resorbable materials.

PubMed

Giorgio, Ivan; Andreaus, Ugo; Scerrato, Daria; dell'Isola, Francesco

2016-10-01

In this paper, the phenomena of resorption and growth of bone tissue and resorption of the biomaterial inside a bicomponent system are studied by means of a numerical method based on finite elements. The material behavior is described by a poro-viscoelastic model with infiltrated voids. The mechanical stimulus that drives these processes is a linear combination of density of strain energy and viscous dissipation. The external excitation is represented by a bending load slowly variable with sinusoidal law characterized by different frequencies. Investigated aspects are the influence of the load frequency, of type of the stimulus and of the effective porosity on the time evolution of the mass densities of considered system.

Developpement d'un modele thermodynamique pour les cristallites de coke: Application aux systems carbone-hydrogene et carbone-soufre

NASA Astrophysics Data System (ADS)

Ouzilleau, Philippe

Carbon materials are essential components of multiple key industrial processes. One example of such a process is the production of aluminum using the Hall-Heroult process. It is well known that important quantities of carbon materials are regularily consumed by the operation of the Hall-Heroult process. In recent years, the increased impurity content of industrial carbon materials motivated the development of a better understanding for the high temperature behavior of these specific materials. The most common forms of carbon materials used in the industry are cokes. Cokes are carbon materials which, following heat treatment, present a crystalline structure similar to that observed in graphite. However, the observed crystallite size of cokes is usually much smaller than the one observed in graphite. For this reason, the chemical and thermodynamic properties of the ordered phase of cokes (i.e. coke crystallites) are very different than those of graphite (although coke crystallites of infinite size would possess properties almost identical to graphite). Coke crystallites consist of hexagonal planes of carbon atoms stacked one above the other. This particular aspect causes strong anisotropic properties in coke crystallites. No thermodynamic model was found for the production of a reliable correlation between the effect of crystallite size and chemical composition for the predictive calculations of the thermodynamic properties (and phase equilibriums) of coke crystallites. It is also difficult to produce predictive calculations that can be compared to experimental results using such a thermodynamic model. The goal of the present work is to propose a thermodynamic model designed to solve this problem. The present model is based on the well-defined geometrical properties of coke cristallites. This geometry allows the development of mathematical equations for the calculation of the mass balances of the crystallite (using a simplified geometry) using only the commonly used cristallite size parameters La (diameter of the crystallite) and Lc (height of the crystallite). The use of the Compound Energy Formalism is necessary to establish the methodology of the present model. Globally, the planar structure of the crystallites is divided into three sublattices on which individual chemical species are assumed to mix randomly. Appropriate thermodynamic paths are used to define the relative enthalpies and absolute entropies of these chemical species. The relative enthalpy and absolute entropy of the coke crystallites are derived for various values of La in the carbon/hydrogen and carbon/sulfur chemical systems. For the carbon/hydrogen system, the model parameters are based on the known values for the entropy of formation of simple hydrogenous organic compounds in the gaseous phase and known carbon/hydrogen bond enthalpies. Also, additional enthalpic properties of coke crystallites and graphitic structures are required for the definition of the thermodynamic paths (for example, the enthalpy associated with the delocalization of one electron in graphitic structures). Results for the carbon/hydrogen system are compared to experiments concerning the dehydrogenation of various cokes. A very satisfying agreement is obtained between the dehydrogenation curves predictively calculated by the model and the reported experimental results (obtained using slow heating rates). Most of the hydrogen content of coke crystallites (this content does not inclue the hydrogen in the condensed volatile matter phase) is predicted to leave the crystalline structure for temperatures between 1100 and 1300 K. Also, experimental measurements of the Gibbs energy of coke relative to graphite are reported. These measurements were obtained using a solid state electrochemical technique. A stabiliy of approximately 900 J g-1, relative to graphite, is reported for temperatures between 950 and 1250 K and for a crystallite size La of ˜10 nm. This value is in excellent agreement with the present thermodynamic model. Finally, an open discussion is made on the possible existance of a degraphitization behavior for coke crystallites heat treated above 2585 K. For the carbon/sulfur system, a modeling approach similar to the one developed for the carbon/hydrogen system is used. Approximately 75% of the model parameters of the carbon/hydrogen and carbon/sulfur systems are common to the two models. Predictive desulfurization curves using the current thermodynamic model are presented for temperatures above 1500 K. A very good agreement is obtained between the model calculations and the reported experimental data. Most of the sulfur content of coke crystallites is predicted to leave the crystallites for temperatures between 1600 and 1850 K. This temperature range is very similar to the puffing temperatures typically found during the desulfurization of petrochemical cokes. The good precision of the model for both studied systems (carbon/sulfur and carbon/hydrogen) combined with the transferability of the model parameters between the carbon/hydrogen and carbon/sulfur systems tend to validate the global approach developed so far.